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This is to certify that the
thesis entitled
AUTOMATIC TESTING OF TRAFFLC RADAR
SPEED MEASURING DEVICES
presented by
C arol L. Bridge
has been accepted towards fulfillment
of the requirements for
Major professor
Date 2-26- 81
0-7639
‘ OVERDUE FINES:
; 25¢ P°r «y per item
‘ (1 $1510sz ugmv MATERIALS:
r: "
-. " Place in book return to remove
Pm!†‘- charge from circulation records
'mx H065
SEP 2719921
25‘i
AUTOMATIC TESTING OF TRAFFIC RADAR
SPEED MEASURING DEVICES
BY
Carol L. Bridge
A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE
Department of Electrical Engineering and Systems Science
1981
cg.//3â€Q‘F
ABSTRACT
AUTOMATIC TESTING OF TRAFFIC RADAR
SPEED MEASURING DEVICES
BY
Carol L. Bridge
This thesis details the development of an apparatus
which automatically tests police traffic radar devices. The
software contains two principal components—-one facilitates
operator interaction while the other models target and patrol
vehicles moving on simulated roadways. Under program control,
the operator selects between X- or K-band radar, moving or
stationary operation, one or two synthetic targets, and one
of four target sizes. These targets may assume any realistic
speeds and initial distances from the antenna. Acceleration
and deceleration of vehicles is also permitted. A signal
channel is associated with each vehicle; frequencies and
amplitudes are varied under program control ten times per
second to update the simulation model. These signals ampli-
tude modulate the radiation sent by the radar antenna and
simulate moving objects.
The simulator meets all its design objectives and is
currently recognized as a useful tool in evaluating radar
devices and instructing radar operators.
ACKNOWLEDGEMENTS
There are many people who have worked with me to make
this research effort a success. I am very grateful to
Dr. P. David Fisher, my academic and research advisor, who
has always been a source of knowledge and encouragement. In
addition, I am indebted to Chuck Dorcey and Mike Schuette
for their substantial help in the construction and evaluation
of the simulator, and to Bill Pearson for drawing the figures
and flowcharts. I would also like to extend a special thanks
to Linda Strawn for the great care and patience she took in
typing the manuscript.
This research was supported in part by the Michigan
State Police Office of Highway Safety Planning under Grant
No. MPT-8l-OOlA.
ii
LIST OF TABLES
LIST OF FIGURES
I.
II.
III.
IV.
TABLE OF CONTENTS
INTRODUCTION
DESIGN REQUIREMENTS
2.1 Radar Test Overview
2.2 Simulator Characteristics
2.3 Hardware Requirements
2.4 Simulator Usage Requirements
HARDWARE
3.1 Main Board
3.1.1
3.1.2
3.1.3
3.1.4
3.1.5
3.2 Front
3.2.1
3.2.2
3.2.3
Data Selection
Frequency Channels
Amplitude Channels
Output Stage
Signal Conditioner
Panel
Decoding Logic
Speed and Distance Displays
LED Display Circuit
External Signal Source
3.4 Synthetic Target Generator
SOFTWARE
4.1 Input from the Operator
4.2 Program and Subroutines
4.2.1
4.2.2
4.2.3
Initialization
Initial Conditions
Computation of the Frequency
Component
iii
Page
vi
mmbww
ll
ll
13
13
18
20
20
20
24
24
29
32
32
36
36
41
41
45
48
4.2.4 Computation of the Amplitude
Component
4.2.5 Output Routine
4.2.6 Updating Frequency and Amplitude
4.2.7 Display Panel
Other Programs
4.3.1 Radar Test Program
4.3.2 Signal Strength Test Program
V. SIMULATOR EVALUATION
5.1
Amplitude Component versus Output Signal
Level
Distance versus Output Signal Level
Turn on Drift
Harmonic Distortion
Accuracy of Frequency
VI. SUMMARY
6.1
6.2
6.3
6.4
REFERENCES
The Traffic Simulator
Tests on Individual Radar Units
Future Improvements
Conclusions
iv
Page
49
50
52
52
54
55
55
61
61
66
68
68
71
74
74
77
78
79
80
LIST OF TABLES
Main board decoding scheme
Front panel decoding scheme
LED functions
Traffic Simulator Program commands
Amplitude and frequency components decode word
Simulator warm-up frequency drift
Simulator output harmonic distortion
Simulator speed synthesis accuracy
Approximate simulator costs
Page
15
25
33
4O
51
7O
72
73
76
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
3.10
3.11
3.12
3.13
3.14
4.1
4.2.
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
5.1
5.2
5.3
LIST OF FIGURES
Traffic Simulator Program terminal session
Radar Test Program terminal session
Signal Strength Test Program terminal session
Traffic radar simulator block diagram
Main board block diagram
Main board timing
Main board frequency channels
Main board amplitude channels
Main board output stage
Main board signal conditioner
Front panel block diagram
Front panel timing
Control word decoding
Speed displays
Distance displays
LED display circuit
LED status word
Traffic Simulator Program flowchart I
Traffic Simulator Program flowchart II
Initialization procedure flowchart
VCO frequency counter flowchart
Initial conditions flowchart
Speed and amplitude requirements flowchart
Speed and distance update flowchart
Radar Test Program flowchart
Signal Strength Test Program flowchart
Amplitude variation flowchart
Entire simulator setup
Computer and simulator front panel
Storage of main board and front panel
vi
Page
10
12
14
16
17
19
21
22
23
26
27
28
30
31
34
37
38
42
44
46
47
53
56
57
59
62
63
64
.6
Page
Amplitude component versus output signal 65
Distance versus signal level for different target
speeds 67
Distance versus signal level for different target
sizes 69
vii
I. INTRODUCTION
Police traffic radar has been used to detect speeding
vehicles for about the past 30 years. Over this period of
time radar devices have evolved from large stationary models
to the present compact units capable of monitoring traffic
in both the moving and stationary modes. Although these
advances have greatly improved the efficiency and effec-
tiveness of police radar, they have also increased scrutiny
by the courts and caused the public to question the accu-
racy, reliability, and limitations of today's police radar
[1, 2].
National studies and recent court decisions have shown
that there is a need to upgrade both radar equipment and the
quality of operator training. To this end, the National
Bureau of Standards (NBS) and the National Highway Traffic
Safety Administration (NHTSA) have developed performance
specifications for speed measuring devices [3]. The re-
search effort reported here deals with the design, construc-
tion, and evaluation of a computer-controlled traffic radar
simulator which is used to simulate, in a laboratory envi-
ronment, traffic on a roadway. This simulator will be an
important tool in both operator training and the assessment
of radar units.
A simulator has an advantage over field testing for
several reasons. First, it can be used to repeatedly
simulate scenes that would be difficult and time consuming
to set up on an actual roadway. It also has the advantage
of conducting tests that would be impossible to do in the
field, but are still useful in the evaluation of radar
units. For instance, the simulator has a feature that
allows an operator to "freeze" all the variables at any
point during the test and study a condition more closely
before continuing with the test. Finally, it can be used
for demonstration purposes to assist in operator training.
1
2
This thesis presents the details of the design, imple-
mentation, evaluation, and usage of the traffic radar
simulator. Chapter 2 details the basic design requirements
of the simulator. The organization of the hardware and
software is discussed in Chapters 3 and 4, respectively.
Chapter 5 summarizes the evaluation tests that were done on
the simulator. Finally, Chapter 6 discusses tests done on
individual radar units and summarizes the development and
evaluation of the simulator.
II . DESIGN REQUIREMENTS
This chapter presents the overall design requirements
for the simulator. We begin by describing in general terms
the types of tests that are to be performed. Next we con-
sider the necessary simulator features. This is followed
by a description of the hardware and its operator interaction
requirements.
2.1 Radar Test Overview
There are various situations that develop where a radar.
unit could provide misleading information to the operator.
One such situation arises when the unit acquires a target
vehicle which is not out front. This often occurs when a
larger or faster moving vehicle is further down the road.
Even though this is not an error as such, it could confuse
the operator if he/she expects to see the speed of the lead
vehicle displayed. Two moving mode errors sometimes occur
when multiple targets are present, shadowing and combining.
Shadowing occurs when the patrol car speed is displayed as
the difference between the patrol speed and that of a large
vehicle it is overtaking. So the difference between the
actual patrol speed and that which is displayed is added to
the speed reading of an oncoming target, thereby increasing
the displayed target speed. Sometimes the sum of the patrol
speed and the speed of an approaching vehicle is displayed
as the patrol car speed. This effect, known as combining,
most often occurs when the patrol car accelerates from a
stopped position. Other errors may occur when the patrol
signal is temporarily interrupted, for example, by anti-radar
detection devices that turn off the microwave oscillator.
There are other possible sources for error which NBS
and NHTSA have also identified [3]. These include
* false target readings due to rapid changes in the patrol
car speed
* errors due to low or high power supply voltages or low
or high operating temperatures
* false readings either due to electrical interference or
mechanical motion, fans, wipers, and vibration
In addition to testing for these error conditions, the
simulator can also be a useful tool in checking other required
radar unit features, for example, patrol and target speed
ranges, lock-recall-clear, and Doppler audio characteristics.
2.2 Simulator Characteristics
In order to identify problems and evaluate new and
existing radar units, there are several properties the
simulator must have. First, tests should be able to be run
in both the moving and stationary modes. There is a need for
multiple targets in order to study effects such as target
selectivity, shadowing, and combining. There is also a need
for different sized targets and the ability to start them
at any distance from the antenna. Moreover, these targets
should be able to approach the radar unit or recede from it.
The patrol vehicle and all targets should be able to accelerate
and decelerate during a test. Also, there is a need for an
external signal source so that the effects of adding noise
or other external signals can be studied.
The operator should be able to control the length of
the test since some tests might last a very long time and
others just a few seconds. The operator should also be able
to begin the test at his/her convenience and stop the test
at any point. After the test has been stopped, the option
of continuing with the old test or starting a new one should
be given.
In addition, there should be the capability to set a
signal of a certain frequency and amplitude without any dynamic
features. Also, there should be a way to vary target signal
amplitudes to any point without considering the relationship
between the amplitude and the roadway conditions.
2.3 Hardware Requirements
To simulate a moving vehicle of a certain size, speed,
and distance, a signal must be generated with a frequency
corresponding to the Doppler shift that would occur for that
speed, and an amplitude which depends on the vehicle's size
and distance away. The simulator must be such that an
operator can use a terminal to specify test parameters such
as speed, size, and distance so the correct signal will be
generated. The operator should not need any understanding
of Doppler shifts or how amplitudes depend on the target
size or the distance it is from the antenna.
Three distinct signals are needed to simulate two
targets and a patrol car. This requires three independent
channels, each with unique frequency and amplitude compo-
nents. The ability to add more channels in the future should
be allowed for. The Doppler shift signals should amplitude
modulate the microwave signal sent from the radar antenna
and thereby, create synthetic targets. Each channel should
have the capability of being sent to a separate modulator,
but there should also be the option of sending the sum of
all three channels to one modulator. The frequency require-
ments should be such that a target and the patrol car can be
converging on one another at speeds from five to 100 mph
each (maximum closing speed of 200 mph) with an accuracy of
:1 mph for stationary mode and :2 mph for moving mode. In
addition, the amplitude component should have a range of three
orders of magnitude.
There must be a Visual display in addition to that on
the radar unit to display the current state of the simulator
during the test. The target speeds and distances and the
patrol car speed should be displayed. Also, there should
be indicators of whether a test is in progress, it is moving
or stationary—mode operation, and which target has the
largest signal, is out front, and is moving fastest. This
will allow the operator to double check the accuracy of the
unit as well as keep track of what is going on during the
test.
2.4 Simulator Usage Requirements
The traffic simulator will be used to simulate actual‘
roadway occurrences with two targets and a patrol car.
After loading the simulator program into main memory, the
operator must control the entire test procedure from the
terminal. Before a test can be run, the operator must
answer a number of questions interactively about the initial
conditions. These questions must include whether moving or
stationary mode is required and the number of targets that
are to be in the test.
If the patrol car is going to be used, then the speed
and amplitude requirements must be entered by the operator.
Also, speed and amplitude requirements must be specified for
each target used. The operator must be able to select
between static and dynamic speed tests. With dynamic tests
the vehicle's speed changes with time. If this is selected,
the operator must enter the initial and final speeds and the
time over which the speed is to be changed. But for static
tests, the operator must only enter a fixed speed for each
vehicle. The patrol car amplitude component must be spec-
ified as an integer between zero and 1000, but the target
amplitudes must be computed in software from the target size
and its distance from the antenna. Therefore, the operator
must specify the distance in feet as well as the size of
each target. The target size will be represented by a
number from one to four with four corresponding to the
largest and one to the smallest.
After the initial conditions have been entered, the
test should begin when the proper command is typed on the
terminal. At this point the simulated targets should begin
moving just as they would on an actual roadway. Current
values of speeds and distances must be displayed on the
front panel and updated twice a second. The test continues
until a pause command is entered which will cause all the
variables to be held fixed until another command is entered.
A sample of the initialization and command sequence is given
in Figure 2.1.
In addition to traffic simulation, the system should be
able to run in two other modes. The first mode should
merely set up a stationary signal on one channel with a
certain frequency and amplitude. Here the operator must
first enter the channel that is to be used and then the
frequency and amplitude components. The frequency component
will be an integer that ranges from one to 700 and the
amplitude component from zero to 1000. Using interactive
commands, the operator must be able to change these fre-
quencies and amplitudes. A sample terminal session is given
in Figure 2.2.
The second mode should use two targets and allow the
operator to specify the speed of each. This mode differs
from the traffic simulation mode in that the target ampli-
tudes are not determined from the target size and distance.
Instead, one target, which must be specified by the oper-
ator, is held fixed while the other is allowed to vary. The
operator must enter the initial amplitude component of both
targets (an integer from zero to 1000) and then enter break-
points. Breakpoints must be entered one at a time and it
should take 10 seconds after the breakpoint is entered to
move from the current amplitude to the new breakpoint.
Throughout the test the speeds and current amplitude com-
ponents should be displayed on the front panel of the
simulator. Figure 2.3 illustrates a sample command sequence
for this mode.
TRAFFIC S IMI‘LATOR PRO GRAM .
X BAND on K BANDTX This test is being run on an
- X-band radar unit in station-
MOVING OR STATIOVARY MODETS ary mode with one target
vehicle. The target is size
TARGET “ERICLE 1?: three and moving at a constant
DYNAMIC TESTTg speed of 60 mph. It begins
DESIRED SPEED <MPH)?6G 5500 feet from the antenna and
TARGET DISTANCE FROM-ANTENNA <FT)?§§flfl_ moves toward it.
TARGET SIZE <1~a>73
TARGET VEHICLE 2mg
>6
>§
>§
>9
>31
X BAND OR K BAND?§| This is an example of a moving
mode test with the patrol car
MOVING OE STATIONARY MODETQI moving at a constant speed of
45 mph. The first target is a
PATROL CAR. size three vehicle decelerating
DYVAMIC TEST?3_ from 75 to 50 mph in 15 seconds.
DESIRED SPEED (MPH)?Q§_ It begins 4000 feet in front of
DESIRED AMPLITUDE <1-xaoc>?;gg the antenna and moves toward it.
Target two is moving in the same
TARGET VEHICLE 1?: direction as the patrol car and
DTNAMIC TEST?! accelerating from 45 to 50 mph
INITIAL SPEED (NPH)TZ§ in 20 seconds. It is a size four
FINAL SPEED (HPH)?§g vehicle and starts 100 feet bee
SPEED DP TIME (SEC)?i_§ hind the patrol car.
TARGET DISTANCE FROM ANTENNA (FT)?4660
TARGET SIZE <1-4>7g
TARGET vEmCLE 22;;
urnnnxc TE5T71_
INITIAL SPEED (MPH)?;5_S_
FINAL SPEED (MPH)?°SD
SPEED UP TIME (SEC)?2_6
1119.61“? DI STANCE FROM ANTmNA (FIN-180
TARGET SIZE (1-4)?g "‘"
>6
>5
>13.
PATROL can: +aaoas +aauae +aaiaa This example also illuStrates
TARGET ONE: +acosa oaaaee +aalaa th? "list" feature where at any
TARGET TVO: ~eaesa -aaaal +aaoaa POlnt during the test: the
>8 action may be Stopped and the
>§ current values of speed, distance,
>7 and signal amplitude are listed.
11.132 (A6) 1860-1775 1801
Figure 2.1 Traffic Simulator Program terminal session
RADAR TEST PROGRAM .
DESIPED TARGET NUMBERT; These tests set up a station-
DESIRED TARGET SPEED (I-TGD)7§§Q, ary signal of a prespecified
DESIRED AMPLITUDE <1-IDGD)?§Q§ frequency and amplitude. The
>1 operator enters the desired
target or channel number, the
desired speed or frequency
DESIRED TARGET MCMBERTg component, and the amplitude
DESIRED TARGET‘SPEED <1-7DG)?§gg component. An "I" is typed
DESIRED AMPLITUDE (1‘106837m to initialize a new signal.
>I
DESIRED TARGET nvnssaz;
DESIRED TAPGET SPEED (l-706)?3$D
DESIRED AMPLITEDE <I-Iaae>7gg
>F
i122 (AD) ISCD-IFTS 1361
>
Figure 2.2 Radar Test Program terminal session
10
SIGNAL STRE-IGTH TEST PROGRAM.
x BAND on x BAMDT§
xmnICLE I: DESIRED SPEED (MPH)?§§
ImHICLE 2: DESIRED SPEED (MPH)?g§
INITIAL AMPLITUDE (I-IDOD)TIDD
REFEHE‘ICE VEUCLE (! 08 2)?)_
VARY TARGET 2.
>216.
>33
>312
ms
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This test uses an x-band radar
and two targets, one at 60 mph
and the other at 25 mph. They
both start at an amplitude of
100, but target two is varied
to 200, 300, 350, 400, 500,,
100, 50, and 250 during the
test.
Figure 2.3
x BAND DR K BANDIE
tmnICLE I: DESIRED SPEED (MPH)?Q§
tmnICLE 2: DESIRED SPEED (RPRIng
INITIAL AMPLITUDE (1-100027200
REFERENCE VEHICLE (1 OR 2)?_2_
VARY TARGET l-
ilD2 (A0) ISCD-IFTS 1861
Here the vehicles are moving at
40 mph and 70 mph with an
initial amplitude of 200. For
this test the amplitude of target
one is varied and target two is
held constant.
Signal Strength Test Program terminal session
I I I . HARDWARE
Under operator control, the traffic radar simulator per-
forms static and dynamic tests on radar units placed in an
anechoic test chamber. Single and double targets of different
sizes can be simulated in both the moving and stationary modes.
A block diagram of the system hardware is presented in Figure 3.1.
The computer, a 16—bit LSI II minicomputer manufactured by
Computer Automation [4], contains 16—k of main memory, a
dual floppy disk drive, and a real time clock. The TTY serves
as the operator interface with the rest of the system. Using
keyboard commands through an interactive operating system, the
operator loads the simulator programs into main memory and
selects the appropriate options. The 16-bit I/O module serves
as the asynchronous interface between the computer's bus and
the rest of the hardware [5]. The front panel displays the
current status of the test in progress, as well as the current
target and patrol vehicle speeds and distances. The main
board acquires data and control messages from the computer
and generates sinusoidal signals for the synthetic target
generator. In this chapter the hardware implementation of
the main board and front panel display is described in detail.
3.1 Main Board
The main board consists of three separate channels which
correspond to the three Doppler signals generated. These
signals have two components that are determined by the computer,
a frequency component and an amplitude component. The former
determines the frequency of the signal sent to the synthetic
target generator. This is related to the desired target
speed and the frequency of the signal transmitted from the
radar antenna. Similarly, the amplitude component, which is
related to the target's size and distance from the antenna,
determines the amplitude of the signal. The output signal
from each channel goes to the output stage where it can
11
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be fine tuned and summed with the other channels. A block
diagram of the main board is shown in Figure 3.2.
3.1.1 Data Selection
The simulator software requires the frequency component
to be on the range one to 700 and the amplitude component
zero to 1000. Only integer values of frequency and amplitude
are allowed. Therefore, the lowest 10 bits of the data bus
are sufficient to output these components. Since the upper
bits of the bus are not used for data, they are used to
steer the lowest 10 bits of data. In particular, select
line three (EX3-), which selects the main board, and the
highest three bits of the bus are the inputs to a binary-to-
BCD decoder. The pulse that the select line generates on
the line being selected at the output of the decoder is used
to strobe the data into the appropriate latches. The decod-
ing scheme for this procedure is given in Table 3.1.
Note that a double set of latches must be used so the
data will be available when the select pulse comes. The
data word, which is output first, is strobed into the
first latch by the output strobe line (STB-). This latch
is shown on the system block diagram in Figure 3.1. The
select pulse, which determines the purpose of the data, is
generated during the next instruction cycle. This pulse
strobes the data from the first latch into the appropriate
second latch either on the main board or the front panel.
Select line three (EX3-) selects the main board. Figure 3.3
illustrates the timing of these signals.
3.1.2 Frequency Channels
The frequency channels are shown in more detail in
Figure 3.4. A Voltage Controlled Oscillator (VCO) is used to
'generate the different frequencies. The particular VCO used
in this system is the XR8038 which has sine, square, and
traingle wave outputs [6]. The sinusoidal output is used
14
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15
EX3- DB15 DB14 D813 Data‘
0 0 0 0 Channel 1: Frequency component
0 O O 1 Channel 1: Amplitude component
0 0 1 0 Channel 2: Frequency component
0 0 1 1 Channel 2: Amplitude component
0 l 0 0 Channel 3: Frequency component
0 1 O 1 Channel 3: Amplitude component
16
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by the target generator, and the traingular outputfl converted
to a digital signal, is sent back to the computer for control
purposes.
The digital frequency component is first transformed by
the D/A converter to an analog voltage ranging from .01 to 7
Volts [7]. (Note that a change of 10 in the frequency com—
ponent corresponds to a change of .1 Volt at the output of
the D/A.) The range of allowable input voltages to the VCO
is from 5 V to 12 V, so this voltage from the D/A is offset
by 5 Volts in the operational amplifier which follows.
The two 4 k9 resistors and the .001 uF capacitor control
the frequency range of the VCO. These particular values were
chosen to yield a maximum frequency of ll kHz. The two
100 k9 potentiometers are used to adjust the shape of the
output signal.
3.1.3 Amplitude Channels
Figure 3.5 gives a detailed diagram of the amplitude
channels. After the amplitude component is converted to an
analog voltage, it is multiplied by the sinusoidal output
from the VCO. The AD534 analog multiplier is used to perform
this multiplication and thereby control the amplitude [81-
The equation for the output of the multiplier is
(Xl-X2)*(Yl-Y2)
OUT =
10
Volts.
Here (Xl-XZ) corresponds to the analog amplitude component
from the D/A and (Yl—Y2) is the signal from the VCO.
Since the analog amplitude component has an amplitude
between zero and 10 Volts and the sinusoid has an amplitude
of 3 Volts peak to peak, the amplitude range of the sinusoid
at the output of the multiplier is from zero to 3 Volts.
However, the output stage reduces the signal to the millivolt
range.
19
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3.1.4 Output Stage
The output signal from each multiplier goes to the out-
put stage. A block diagram of this stage is shown in
Figure 3.6.
The 5 k9 potentiometers at the inputs of each amplifier
stage are used to adjust the voltage levels of the signals
going to the synthetic target generator. Here fine tuning
adjustments can be made so that the same amplitude component
will correspond to the same voltage out for all three channels.
Each channel may be used separately, but there is also a
summing amplifier which allows the sum of the three channels
to be taken off on one. The RC T-circuit at each output
filters any high frequency noise from the op amp and con-
verts the signal to be sent to the target generator to a
current.
3.1.5 Signal Conditioner
The triangle wave outputs from the VCO's are taken to
the signal conditioning circuit shown in Figure 3.7. This
circuit consists of three comparators, one for each channel.
These comparators convert the triangle wave to a TTL signal
of the same frequency which in turn is sent back to the
computer on the sense lines. The computer uses these lines
to count the VCO frequencies generated by different frequency
components. The purpose of this will be discussed further
in Chapter 4.
3.2 Front Panel
The target and patrol car speeds and the distances the
targets are from the antenna are continually being updated
and displayed on the front panel. There is also a series of
LED's indicating the presence of certain conditions. A
block diagram of the front panel hardware is shown in
Figure 3.8.
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23
16
DBlS
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DISTANCE
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ENABLE4
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TARGET
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DISPLAYS
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24
3.2.1 Decoding Logic
The entire data bus is needed for the data to be dis-
played. Consequently, the decoding can no longer be done
using the highest bits of the data word. Thus, two separate
words are used, a control word and a data word. Moreover,
two separate select lines are needed to distinguish between
them. The control word, which is output first, controls
where the data word is to go. The decoding for the control
word is given in Table 3.2.
Once again, two levels of latches are used so that the
data will be available when the select pulse is generated.
Select line six (EX6-) is used to strobe the control word
into the control latch and select line seven (EX7-), NOR'ed
with the outputs of the control latch, strobes the data word
into the data latches (See Figure 3.9). The hardware for
the control word decoding is shown in Figure 3.10.
3.2.2 Speed and Distance Displays
A diagram of the speed displays is shown in Figure 3.11.
ENABLEl, ENABLE3, or ENABLES strobes the data to be displayed
into the latches for the speed of target one, two, or the
patrol car, respectively. It is assumed that the vehicles
will be traveling at speeds from -199 mph to +199 mph. A
negative speed means that the vehicle is traveling away from
the antenna rather than toward it.
Since speeds only between -l99 and +199 mph will be
displayed, the speed displays are made up of three digits.
The most significant digit, which corresponds to the :100
place, is a :1 digit. Bits nine and fifteen are used to
decode the data for this digit. A high level on bit fifteen
turns the negative sign on and a low level on bit nine turns
the "l" on. It may seem that bit eight should control the
"l", but a "ilxx" is represented by a 01 in bits nine and
eight while a "iOXX" is represented by a 11. Therefore, it
is bit nine which determines the "1". If the value of the
speed is positive, no sign bit is turned on.
25
Table 3.2 Front panel decoding scheme
Control Word Data
(DBO6 - DBOO)
0 O 0 0 O O l ENABLEO: LED'S
O O O 0 0 1 0 ENABLEl: Target 1, speed
0 0 O 0 l O O ENABLEZ: Target 1, distance
0 0 O l O O 0 ENABLEB: Target 2, speed
0 O 1 0 O O O ENABLE4: Target 2, distance
0 l 0 0 O 0 0 ENABLES: Patrol car, speed
ENABLEG: Display blanking
l O 0 0 0 O 0
ENABLE7: Display blanking
26
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The two least significant digits are standard 7-segment
displays [9]. Bits four through seven contain the value
of the ten's digit in BCD code and bits zero through three
contain the value of the one's digit. The decoder/driver
chip is a BCD to 7-segment decoder. From the BCD inputs
to the decoder, each of the seven outputs determine whether
each of the seven segments of the display should be on or
off.
The distance displays, as shown in Figure 3.12, are
more straight forward than the speed displays. They are
controlled by ENABLEZ and ENABLE4 for target one and two,
respectively. It is'assumed that the antenna is in the
patrol car, so the distance from the antenna to the patrol
car is always zero.
Distances of one to 9999 feet from the antenna are
displayed. Although the software allows distances greater
than 9999 feet and less than one foot, they are not dis-
played. The four distance digits in BCD code are stored in
the data bus as follows: bits twelve through fifteen
correspond to the thousand's digit, bits eight through
eleven to the hundred's digit, bits four through seven to
the ten's digit, and bits zero through three to the one's
digit.
All of the displays may be blanked by ENABLE6 and
ENABLE7 when a control word of 1000000 is output. It is
desirable to blank the displays in this way when there is
no valid data to be displayed. In addition, each display
may be blanked separately by sending four ones to the 7447
decoder. Leading zeros of both the speed and distance
displays are blanked in this manner.
3.2.3 LED Display Circuit
The diagram for the LED display circuit is shown in
Figure 3.13. There are four LED's which correspond to the
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following conditions: "test in progress," "pause," "moving
mode," and "stationary mode." Six additional LED's are used
to indicate whether it is target one or two that is moving
fastest, is closest to the antenna, or has the largest signal.
A summary of the functions of these ten LED's is given in
Table 3.3.
A lO-bit data word contains the state of these LED's.
The format of the word is shown in Figure 3.14. The hard-
ware for the LED powering consists of a lO-bit latch into
which the LED data word is strobed by the ENABLEO pulse.
The drivers provide enough current to power each LED.
3.3 External Signal Source
There is potential for an additional input to the
system which has not been discussed previously. This input
is an external signal source and may be data recorded in
the field, a random noise generator, or an oscillator. It
is not affected at all by the computer, and may be used
alone or with the rest of the system. So this external
signal source becomes a fourth channel and gives the Operator
the opportunity to add some other source of data.
3.4 Synthetic Target Generator
The sum of the sinusoidal signals from the main board
with frequencies and amplitudes determined by the test
conditions is sent to the synthetic target generator. The
synthetic target generator amplitude modulates the micro-
wave signal sent from the radar antenna by this signal from
the main board. This modulated signal is sent back to the
antenna and is detected as the Doppler shift caused by one
or more moving objects.
The synthetic target generator is comprised of the
following: a Narda Model 640 standard gain horn, which
receives the CW microwave signal from the radar under test
and then re-transmits the signal as an amplitude modulated
wave; a Hewlett Packard Model X375A variable attenuator,
33
Table 3.3 LED functions
D10 "Test in Progress"
D9 "Pause"
D8 "Moving Mode"
D7 "Stationary Mode"
D6 "Target 1 fastest"
D5 "Target 2 fastest"
D4 "Target 1 out front"
D3 "Target 2 out front"
D2 "Target 1 largest signal"
D1 "Target 2 largest signal"
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which allows the operator to control the level of the received/
transmitted signal; and a Hewlett Packard Model X485B detector
mount with a 1N23B diode, which serves as the modulator.
IV . SOFTWARE
The last chapter defined the hardware for the traffic
radar simulator. Throughout the discussion, the existence
of the correct amplitude and frequency components and the
correct data for the display panel was assumed. This
chapter will examine the simulator's software and how these
components are determined.
The software for the simulator consists of three main
programs. The largest is the Traffic Simulator Program and
will be discussed in detail in the following sections. The
Signal Strength Test Program and the Radar Test Program
apply many of the same concepts as the Traffic Simulator
Program and will be discussed in some detail later in this
chapter.
4.1 Input from the Operator
The Traffic Simulator Program simulates actual roadway
occurrences with two target vehicles and a patrol car. A
flowchart for this program is given in Figures 4.1 and 4.2.
Before the test begins, there are a number of decisions about
the test that must be made by the operator. These decisions
will be discussed in the following paragraphs.
There are two types of radar devices that are presently
being used: X-band and K-band. The X-band device is designed
to operate in the frequency range of 10,500 to 10,550 MHz and
has a Doppler shift of 31.384 Hz/mph while the K-band device
operates in the frequency range of 24,050 to 24,250 MHz and
has a Doppler shift of 72.012 Hz/mph. The program can run
tests on either the X— or K-band device and the operator
must specify which device is being tested.
The program may also be used for both moving and
stationary mode tests. The operator must specify whether
moving or stationary mode is desired. If moving mode is
specified, the operator must enter the patrol car speed
36
37
< START >
Initialize test
Set up
initial test
conditions
C .4
H ‘-
Input command
when ready
List
initial
condition:
Go to
File manager
Cb
Figure 4.1 Traffic Simulator Program flowchart I
38
Begin RIC
o ' interrupts
[Ox/sec.
interrupt?
Update spend
distance. a
- displays for all
3 channsls
has
haractn No
son typed
Yes
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Input command
when ready
List current
values of
distance. speed.
& Jgglitude
No
Roland variables
1 with
initial conditions
Figure 4.2 Traffic Simulator Program flowchart II
39
requirements and the patrol car amplitude. On the other
hand, if stationary mode is specified, the patrol car speed
and amplitude components are zeroed for the duration of the
test.
The test may be run on either target one, target two,
or both targets. The operator must enter a "Y" after each
target number that is to be used in the test and an "N"
otherwise. If a target is used in the test, the operator
must specify the speed requirements, the initial distance
from the antenna, and the size of the target. Otherwise,
the target speed and amplitude components are set to zero.
After the initial conditions have been entered, there
are a number of commands which can be used throughout the
testing process. A summary of the commands is given in
Table 4.1.
The "G" command begins the test after all the test
conditions have been determined. At this time, the synthetic
targets start moving either toward or away from the antenna
if their speeds are positive or negative, respectively. The
display panel, which is updated twice a second, displays the
current state of the variables.
At any time during the test, a "P" may be typed to
enter the pause mode. At this point, the variables stop
changing and are held at their current values until another
command is entered. This allows the operator to stop and
examine certain conditions at any point during the test.
When the program is in the pause mode, any of the
other commands listed in Table 4.1 may be entered. A "G"
will continue the test from the point it had stopped, or an
"I" allows the operator to enter a new set of initial
conditions. If an "R" is entered, the initial conditions
from the previous test will be reloaded into the variables
and a "G" will start the previous test over. The list
command, "L" will list the present speeds, distances from
the antenna, and signal amplitudes of the two targets and
40
Table 4.1 Traffic Simulator Program Commands
"G"
"P.
.. 1..
"R.
"L.
"F"
Go
Pause
Initialize
Repeat
List
File manager
41
the patrol car. Finally, the "F" command takes control out
of the current program to the file manager, where a different
file can be loaded if it is desired to do so.
4.2 Program and Subroutines
The flowchart of the entire Traffic Simulator Program,
which is shown in Figures 4.1 and 4.2, can be broken down
into several smaller problems. These smaller problems will
be examined in the following subsections.
4.2.1 Initialization
After the program has been loaded and each time an "I"
command is used, the program goes through an initialization
routine. The flowchart for the initialization procedure is
shown in Figure 4.3. This procedure consists of three
events: writing the program heading, calibrating the VCO's,
and resetting all the variables from the previous test. The
program heading, "Traffic Simulator Program", is only
written out at the loading of the program. After the first
test has been run, the initialization procedure begins with
calibrating the VCO's. This consists of determining an
equation from which to calculate the frequency component.
If the frequency component is assumed to have a linear rela-
tion with the actual frequency of the signal produced by
the VCO, the equation would be of the form
V = M*F+B .
Here V is the frequency component, F is the actual frequency
produced by the VCO, and M and B are constants to be
determined. This linear equation gives results within the
allowed accuracy, however the values for M and B tend to
drift over a period of time. For this reason, M and B are
recalculated each time a new set of initial conditions is
entered.
42
BEGIN
Write heading
Count frequencies
of VCO's for
outputs of
V=450mV & V=650mv
‘1
Compute equations
for converting
frequency to
voltage
Zero amplitudes
& speeds.
Blank displays
Figure 4.3 Initialization
procedure flowchart
43
To calculate M and B, two points on the line must be
obtained. The points used are those corresponding to
frequency components of 450 and 650. Each component is
output to all three channels and the frequency produced by
each VCO is counted. Since each VCO may have somewhat
different characteristics than the others, a unique M and B
are determined for each channel expanding the values to be
determined to M1, M2, M3, Bl, B2, and B3. When the frequen-
cies corresponding to the two components have been counted
for each channel, the values for M and B may be obtained
from the following formulas.
200
M = F(650) - F(450)
B = 450 - M*F(450)
where F(V) corresponds to the frequency produced by a frequency
component of V.
The counting of the frequencies is done using sense
lines zero through two (ESO - E821. As discussed in
Section 3.1.5, each sense line has a TTL signal on it with
the same frequency as the frequency of its corresponding VCO.
To count the frequency of this signal, the real time clock
interrupts are set up to send a SYNC interrupt after one
second. Each rising edge of the signal is counted between
the time the interrupts are enabled and the time the SYNC
interrupt occurs. The count at the time that the SYNC occurs
corresponds to the frequency of the signal within an accuracy
of :1 Hz. A flowchart for the count subroutine is shown in
Figure 4.4.
The detection of each rising edge is outlined in the
flowchart. When a zero is sensed, the flag corresponding
to that sense line is reset. Then when a one is sensed, the
flag is set and, if it has not been previously set, the
count is incremented. But it is only incremented for the
first one in a series because any ones that occur after the
flag is set are not counted. Therefore, the count is only
incremented on a rising edge.
44
‘ BESIN >
Output voltage
for which corres-
ponding frequency
is desired
Set up RIC
to send SYNC
after 1 sec.
1
Yes . END
_' No
No
Increment
COUNTI
1
Set FLAGl
Reset FLAGl
Increment
COUNTZ
Reset FLAGZ
Set FLAGZ
E53'l?
Increment
COUNT3
1
Set FLAG3
Reset FLAGS
Figure 4.4 VCO frequency counter flowchart
45
4.2.2 Initial Conditions
Figure 4.5 shows the determination of the initial test
conditions that were discussed in Section 4.1. It is first
determined whether an X— or K-band device is being used, then
whether moving or stationary mode operation is desired. If
moving mode is desired, the speed requirements and amplitude
of the patrol car are determined. For each target that is
desired in the test, the speed and amplitude requirements of
the target are then determined.
The speed requirements are shown in greater detail in
Figure 4.6a. The program allows for a dynamic test for
which the vehicle may speed up or slow down over a period of
time. If a dynamic test is desired, the initial speed, final
speed, and speedup time must be entered. Otherwise, one
speed is entered and the final and initial speeds are set
equal to that speed for the entire test. The speedup incre-
ment is then computed from the formula
Aspeed = (final speed) - (initial speed)
(speedup time)
This determines the amount per second that the speed is
changed while going from the initial speed to the final
speed in the speedup time specified. Note that for a
stationary test, the final speed equals the initial speed
and the speedup increment is therefore zero.
If a dynamic test is being run, the frequency component
corresponding to the initial speed of each vehicle will be
output to the frequency channels initially. As soon as the
"G" command is entered to begin the test, the speeds will
start increasing or decreasing according to their speedup
increments. This is a linear change with time. As soon as
each vehicle reaches its final speed, it stops changing and
remains at that speed throughout the remainder of the
test.
Figure 4.5
46
Speed to frequencv
ratio - Jl.)85
Determine PC
soeed requirements
l
Determine PC
amplitude
Speed to frequencv
ratio - '2.fllZ
l
Zero PC
speed 5 amplitude
Deteniee urge: 1
speed requireeents
l
Oetermime terse: l
amplitude requiremente
Zero career 1
seeed i amplitude
Determine target 2
speed results-eats
l
Determine target 2
amplitude requirements
Zero rsrset 2
speed 8 amplitude
Compute initial
speed 6 amplitude
L .
Display
initial conditions
Initial conditions
flowchart
Figure 4.6
47
1
Determine Get desired
initial speed speed
7 7
Determine Set final speed
final speed - initial speed
Determine
speed up time
V
7
Compute speed
up increment:
final sod - initial 32d
SD' ’
c:
BEGIN
Determine
initial
distance away
1
Determine
size
7
b < END )
a. Speed requirements flowchart
b. Amplitude requirements flowchart
48
There are two factors that determine the amplitude of
the target signals, target distance from the antenna and
target size. As shown in Figure 4.6b, the amplitude require-
ments consist of entering the initial distance the target is
from the antenna and its size. The initial distance is to
be entered in feet and can be any signed five place decimal
number. A number one through four is to be entered to
specify the size of the target, with four corresponding to
the largest vehicle and one corresponding to the smallest.
A few special considerations must be made for the patrol
car if moving-mode operation is desired. First of all, in
order to avoid errors, the patrol car speed must be established
before any targets appear. For this reason, as soon as the
initial patrol speed is determined, its frequency component
is output while the target frequency components are not out-
put until after all the initial test conditions have been
determined. There is also a short delay in the repeat
routine so that the patrol speed may be established before
any target speeds. Another consideration that must be made
is that the amplitude of the patrol signal does not depend
on its distance and size, but on factors such as the road-
way surface and surroundings. For this reason, instead of
entering distance away (the patrol distance is zero anyway)
and size, the desired amplitude component is entered. An
amplitude component of 100 has been found satisfactory for
many of the tests that have been run.
4.2.3 Computation of the Frequency Component
Throughout each test, the value of the frequency
component is continually being updated and computed from
the values for the desired speeds of the vehicles under
test. The current speed of each vehicle is stored in the
variables CSPDl, CSPDZ, and CSPD3 for targets one, two, and
the patrol car, respectively. It is the closing speed that
the radar device actually picks up, so if the patrol car
49
speed is something other than zero, it must be added to the
target speeds before the computation of the frequency
component. Therefore, two new variables are defined:
CLSPDl
CSPDl + CSPD3
CLSPDZ CSPD2 + CSPD3
for the closing speeds of targets one and two, respectively.
From these variables, the frequencies the three channels are
computed from the equations
F1 = K*|CLSPD1I
F2 = K*ICLSPD2|
F3 = K*ICSPD3I
where F1, F2, and F3 are the desired Doppler frequency
shifts of targets one, two, and the patrol car, respectively,
and K is the speed to frequency conversion factor. K is
31.384 and 72.012 for X-band and K-band, respectively.
Since negative speeds are allowed, the absolute value of
the speeds must be used to compute the frequencies.
Now that the desired frequency shifts have been obtained,
the formulas derived in the VCO calibration procedure can be
used to determine the frequency component.
VSPDl = Ml*Fl+Bl
VSPD2 = M2*F2+BZ
VSPD3 = M3*F3+B3.
These equations yield the frequency components (VSPDl,
VSPD2, and VSPD3) for the three channels from the desired
frequencies and the M’s and B's that were derived in
Section 4.2.1.
4.2.4 Computation of the Amplitude Component
The amplitude of the patrol car signal does not change
during a test, so it requries no computation or updating.
50
However, the amplitude of the two target signals must be
computed at each time step based on target size, which
doesn't change during the test, and target distance, which
does change. The equations used to compute the amplitude
components are given below.
3
_ Kx 1
VAMPl {121 + 1811]
3
_ Kx 1
VAMP2 _[R2 + 1811]
VAMPl and VAMP2 are the amplitude components for targets
one and two, respectively and R1 and R2 are the distances
each target is from the antenna. If R1 or R2 is less than
zero, the amplitude component is set to zero. The constant
Kx corresponds to K1 through K4 for sizes one through four,
respectively and the values for Kl through K4 are 6177,
8542, 10,727, 15,277, respectively. The values for the
K's and the pole at 1811 were chosen so that a size four
vehicle would have an amplitude component of 20 at 5280 feet
and a component of 600 at zero. In addition, an amplitude
component of 20 should be obtained for size three at 3168
feet, size two at 2112 feet, and size one at 1056 feet.
4.2.5 Output Routine
After the frequency and amplitude components have been
computed, they are output to the main board. As discussed
in Section 3.1, a decode word must be added in the most
significant bits of each component to steer the data to the
appropriate channel. The code for the output of the
component is given below.
LDA Component Load accumulator with component
ADD Decode Word Add decode word to component
OTA :18,2 Output component + decode word to
main board
SEL :18,3 Generate select pulse to strobe latches
The decode word for the components are given in Table 4.2.
51
Table 4.2 Amplitude and frequency components decode word
:0000 Target one frequency
:2000 Target one amplitude
:4000 Target two frequency
:6000 Target two amplitude
:8000 Patrol car frequency
:A000 Patrol car amplitude
52
4.2.6 Updating Frequency and Amplitude
When a test is in progress, the real time clock interrupts
are set so that a SYNC interrupt will be generated ten times
a second. Every time a SYNC interrupt occurs, the current
speeds and distances are updated. Figure 4.7 illustrates
the procedure required to update the speeds and distances.
To update the speed, the final vehicle speed is compared
with the current speed. If they are the same, the current
speed is not changed. However, if they are different, oner
tenth of the speedup increment is added to the current
speed. One-tenth of the increment is used because there are
ten increments added in a second. The next step is to com-
pute the frequency component as described in Section 4.2.3
and output the updated frequency component to the main
board.
To update the amplitude, the distance the vehicle
traveled during the time interval must be computed. The
following equations can be used to compute the distance
traveled from the closing speeds of the vehicles.
INDISTl
.1466667*CLSPD1
INDIST2 .1466667*CLSPD2
The new distances can be computed by subtracting the above
distance increments from the current distances. If the
speed is positive, the vehicle will move closer to the antenna
and if the speed is negative, it will move farther away. The
new amplitude component may be computed as described in
Section 4.2.4 and output to the interface. Note that the
patrol car amplitude does not change during the test.
4.2.7 Display Panel
After every five SYNC interrupts (twice a second), the
display panel is updated. This requires converting the
current speeds of the three vehicles and the two target
distances to BCD and outputing each speed and distance to
53
Final speed
yet?
Add speed up
increment to
current speed
Compute new
frequency component
Compute distance
traveled during
interval
Subtract
distance traveled
from current distance
Compute new
amplitude
component
Display new
speeds and
distances
Figure 4.7 Speed and distance update flowchart
.....
. ,e
54
the appropriate display latches. It also requires updating
the LED status word and outputing that to the appropriate
latch. The code for outputing data to the front panel is
given below.
LDA Control Word Load accumulator with control word
OTA :18,2 Output control word
SEL :18,6 Select front panel control word
LDA Data Word Load accumulator with data word
OTA :18,2 Output data word
SEL :18,7 Select front panel data word
The control word determines where the data is to be routed
as discussed in Section 3.2 and Table 3.2 lists the control
words for each display.
The LED status word was also discussed in Section 3.2.
It is updated by comparing the amplitudes, distances from the
antenna, and speeds of the two targets. If target two has
a larger signal, bit nine is set, otherwise bit eight is set.
Similarly, if target two is closer to the antenna and moving
faster, bits seven and five are set. Otherwise, bits six and
four are set. For stationary-mode operation, bit three is
set and for moving-mode, bit two is set. Finally, if a test
is in progress, bit zero is set, otherwise the pause bit,
bit one, is set.
4.3 Other Programs
Two additional software packages were developed. The
Radar Test Program performs simple tests on one channel at a
time to ensure that the VCO and multiplier circuitry works
properly. And the Signal Strength Test Program tests the
response of a radar unit when the signal strength is varied.
These two routines are described in the remainder of this
chapter.
55
4.3.1 Radar Test Program
A flowchart for the Radar Test Program is given in
Figure 4.8. It tests one channel which is prespecified by
the operator. During the test, the other two channels have
their frequency and amplitude components set to zero. For
the channel under test, the operator must specify the
frequency component and the amplitude component desired. As
for the traffic simulator program, the frequency component
may range from one to 700 (.01 V to 7 V) and the amplitude
component may range from zero to 1000 (0 V to 10 V).
A signal will be set up on the desired channel corre-
sponding to the values for the amplitude and frequency com-
ponents that are specified. The higher the amplitude com-
ponent, the higher the actual signal amplitude will be, while
the higher the frequency component, the lower the actual
signal frequency will be. By adjusting the amplitude and
frequency components, any signal in the range of zero to
200 millivolts and 25 to 11,000 hertz may be obtained. No
computation needs to be done since the components are output
in the same form as they are input. The output routine is
the same as that discussed in Section 4.2.5 for the Traffic
Simulator Program and the display panel is left blank
throughout this program.
When the test is completed, the operator may type an
"I" to initialize the variables for a new test, or an "F"
to go to the file manager and call a new program.
The simplicity of this program makes it useful when
simple tests or minor adjustments are being done on the
hardware. It also provides a quick check that the hard-
ware is working properly.
4.3.2 Signal Strength Test Program
The Signal Strength Test Program only uses channels
one and two. A flowchart of the program is given in Figure 4.9.
In this program, the operator selects a desired speed for each
'utnu: frenulnty
component to
desired channel
Determine
amplitude
component
Output amplitude
component to
desired channel
Input next
comm-n
when ready
Radar Test Program flowchart
57
Initialize
speed (frequency
requirements
Determine initia‘
amplitude
requirements
rmine
which target
is to be varied
Input breakpoint
or comman
when ready
breakpoint
to File
nag
Figure 4.9 Signal Strength Test Program flowchart
58
target which remains constant throughout the test. The
operator also selects the initial amplitude component of the
two signals. Again, the amplitude component is a number
between zero and 1000.
After the initial amplitude and speeds are determined,
the amplitude of one of the channels is allowed to vary.
The operator selects which channel is to be varied and may
then begin entering breakpoints. If the breakpoint is
followed by a space or a carriage return, the amplitude of
the desired channel will change linearly from its current
amplitude to the amplitude specified by the breakpoint while
the amplitude of the other channel is held constant. After
the amplitude of the breakpoint has been reached, the
operator may enter another breakpoint or a command. An "I"
will initialize the amplitude and speeds or an "P" will
transfer control to the file manager.
The frequency components are computed in the same
manner as described in the discussion of the Traffic Simu-
lator Program with calibration of the VCO's at the initial-
ization of every new test. The output of the frequency and
amplitude components to the interface is also done in the
same way as the previous two programs. The speeds of the
two vehicles are displayed on the display panel, and in the
place where the distances were displayed for the Traffic
Simulator Program, the amplitude components of the two
channels are displayed. In other words, at any point during
the test, the current amplitude component is displayed on
the front panel.
Figure 4.10 shows the flowchart of the subroutine that
changes the amplitude from one breakpoint to the next. The
amplitude increment is computed by
(New breakpoint) - (Current amplitude)
AAmP = 100
which is added to the current amplitude at every SYNC inter-
rupt. Again, the SYNC interrupts occur ten times a second,
so after ten seconds, the final amplitude will be reached.
59
BEGIN
Compute
increment to
hange amplitud:
Begin RIC
interrupts
le/sec
Add increment
to current
Amplitude
Output
nev amplitude
Update
displays every
Sch pass
Figure 4.10 Amplitude variation flowchart
60
This program is especially useful in testing the
hysterisis effects of radar units. Two different speeds may
be entered and this program may be used to determine the
amplitudes when one speed is detected over another. Results
of hysterisis tests will be presented and discussed further
in a later chapter.
V. SIMULATOR EVALUATION
The previous two chapters presented the details of the
hardware and software for the simulator. Figures 5.1 through
5.3 show different aspects of the simulator. The entire
setup is shown in Figure 5.1. The operator, through use of
the teletype, provides the necessary test data to the computer
and the anechoic test chamber is shown in the lower right hand
corner. A close up of the computer and the simulator front
panel is shown in Figure 5.2. The computer is on the bottom
of the cabinet; the floppy—disk drive is above it; the main
board and front panel are housed in the top compartment. The
top section of the cabinet slides out as shown in Figure 5.3.
The main board is mounted horizontally in the drawer and the
display board stands vertically against the front. The
power supplies necessary for this hardware are mounted on
the bottom of the drawer below the main board.
Several experiments have been conducted to evaluate the
simulator. The results of these experiments are presented
in the following sections.
5.1 Amplitude Component versus Output Signal Level
The simulator transforms integer amplitude components
to a corresponding voltage. This voltage is applied to the
T-filter network (Figure 3.6) and the modulator diode to
produce a change in conductance. Ultimately, then the
amplitude component represents a target signal strength.
The first test measures the voltage level out of the
simulator for different amplitude components. Voltage
levels for amplitude components between zero and 1000 were
recorded for several different frequency components and for
each of the three channels. Since the data were consistent
for all the channels at all different target speeds, the
results for just one channel at 55 mph are plotted in
Figure 5.4.
61
62
mspwm HOpMHBEHm muflucm 1m 9.35.3
63
;m
Figure 5.2 Computer and simulator front panel
64
amend ucoum pan
UHMOQ chE How wmmuoum
m.m messes
amt/ma Hmcmflm usmpso mDmHm> ucmcomaoo wpspflamï¬m v.m musmflm
.mmvzcwflaemg bccccflrecu 2:5:92
GOA: ooa com coh cow ccm 2:. com com on; on o.
. _ . _ _
65
:9: m m
om.
tenet teubrs andano
AW)
(511.13
66
It was assumed in the software design of the simulator
that the relationship between the amplitude component and
the output signal level was linear for the entire amplitude
range. However, as seen in Figure 5.4, this relationship
only holds for amplitude components up to about 400. For
reasons stated later in this chapter, the actual amplitudes
are restricted to be less than 600. At this amplitude, the
maximum deviation between the assumed and the actual returned
target signal strength corresponds to an uncertainty in
distance of about the length of the target vehicle. This
is quite small compared with other approximations. Moreover,
size four target vehicles are the only ones which reach this
maximum amplitude (see Figure 5.6). If this nonlinear effect
does prove to lead to significant errors, it can easily be
accounted for in software.
5.2 Distance versus Output Signal Level
This test examines the output signal level versus the
distance the target is from the radar antenna. The equation
for determining the amplitude component from the distance
and size was obtained empirically after analyzing data that
was collected in field tests on actual highways. It was
found that the amplitude of an approaching vehicle varies as
_ K
AmP' ‘ [D‘i's't' .—+ 181)]?
The size coefficients (K) and the pole at 1811 were chosen
such that targets may be "just acquired" at one mile, six-
tenths, four-tenths, and two—tenths of a mile. Several runs
were made with targets of different sizes at different
speeds, and the significant results are plotted in Figures 5.5
and 5.6.
Figure 5.2 is a plot of distance versus signal level f0r
target one, size three, moving at 55 mph. The theoretical
67
Hm>wa Hmcmflm msmum> mocmumflo m.m wusmflm
“but: go mpcmmsozev mozcumga
o- m.n o.m c.~ o.~ m. N. a. mo. ï¬e.
d u q u
.. UL
1 an
0
m
1 me we
3
S
t.
6
u
D.
I
L ow I
a
A
3
I
m
A
wmucmaduwzï¬u 0 4 m5 m
S
HMUwumucvsb a (
4 ca
1 mo—
;E cm
L o-
68
curve on this figure is a plot of
3
_ 10,727 1
Am? ‘ [Dist + 181lJ
that has been normalized to the same scale as the experimental
data. Of course, this is the equation that is used in the
software to calculate the amplitude component from the
distance. The shape of the theoretical curve agrees well
with the actual signal levels. In fact, the error is less
than one target vehicle length for distances up to one-half
mile and less than two vehicle lengths for targets up to a
mile away from the antenna.
Figure 5.3 illustrates how the target size affects the
amplitude of the signal. This is a plot of all four sizes
of target one at 55 mph. It shows the difference between
the amplitude of a very large vehicle, such as a truck, and
a small vehicle, such as a motorcycle, when all other condi-
tions are the same. Although the data shown are for target
one at 55 mph, the results are virtually identical for both
targets at all reasonable speeds.
5.3 Turn on Drift
When the simulator is first turned on, the frequencies
of the signals from the VCO's drift. This drift is due to
changes in component temperature. Table 5.1 presents the
results of the tests that were run to measure the turn on
drift. The system was left off overnight and the frequen-
cies were measured periodically after it was turned back on.
It appears that 30 minutes to an hour is sufficient time to
allow the simulator to reach equilibrium. All the other
tests in this section were performed after this warm-up
period. There is no noticeable amplitude drift.
5.4 Harmonic Distortion
By the very nature of the microwave modulator, we
expect not only to obtain modulated microwave signals at the
69
mmuflm ummumu ucmumMMHp MOM Hm>mH Hmcmflm momHm> mocmumflo m.m musmwm
Abwwb ac mccamzozev woceumwa
c— m.h o.m c.N c.~ m. N. a. mc. Ac.
(1.} If 4 . . 4 a
e if i
/ llIIIITdmwNMm
{f/ 4 «m msflm 4 co
If m @Nflm
1 o-
n cmd
1 cam
1 COM
v WNMW .
tenet Ieubrs indano
(SW1 Am)
70
Table 5.1 Simulator warm-up frequency drift
Time Speed = 55 mph Speed = 55 mph Speed = 20 mph
(min.) amp. comp. = 500 amp. comp. = 200 amp. comp. = 200
93.1 92.0 92.0
93.8 92.6 92.4
94.7 93.5 93.7
10 96.0 95.3 95.7
15 96.8. 96.3 96.8
20 97.5 97.0 97.5
30 98.3 98.0 98.5
45 99.3 99.0 99.2
60 99.8 99.7 99.7
Tabulated figures represent frequency as a percent of the
final value in a 70 minute test.
71
frequencies of the VCO's but also harmonics of these fre—
quencies and the mixing of signal frequencies from different
channels. While these harmonics and mixed frequency signals
are unwanted, they are tolerable as long as they do not
produce false radar readings. Based upon radar manufactur-
er's specifications for speed/signal strength selectivity,
we chose to maintain these unwanted signals to less than
-l6dB of the desired signal. Table 5.2 summarizes the
distortion measurement results for 55 mph targets. From
these results we conclude that the allowed range for the
amplitude component is zero to 600.
5.5 Accuracy of Frequency
This test compares the actual simulated target speed
(Doppler shift) with the desired speed (Doppler shift).
Actual simulated Doppler shift frequencies were measured
and the actual speeds computed as follows:
f
speed = m for X-band, and
speed = 7§T§l§ for K-band.
The test results are presented in Table 5.3.
There are many sources of error in the actual frequency
versus the desired frequency: nonlinearity in the VCO's and
rounding in the computation of the frequency component are
two primary ones. However, the results of this test are
still very acceptable. Speeds to an accuracy of :1 mph can
be achieved in the stationary mode and :2 mph in the moving
mode (an error of :1 mph for the patrol car adds an addi-
tional :1 mph error to the target vehicle). If desired,
software could be written to further improve the accuracy.
72
.umH map Op m>HumHmH
mum mOHCOEHm: mo Ampv meson ucmmmummu UmpMHSQMp mmusmflm
.nmE mm pmmmm
Hmccmao co
mpme mpmmu HH<
m.mm: w.oml I a I h
m.mmu m.me| I u n m
«.mMI m.evu v.om1 m.mw1 m.mmt m
h.>ms «.mml o.am| m.>m| m.om| e
N.Nm| m.mm| m.mml m.mmn H.mml m
m.van H.man o.mal m.>m| o.mm| m
o o o o o a
wouMHS©oE HoumHDUOE HoumHspos HouMHSUOE HouMHSUOE 0c
coca u .QEm oow n .mEm com u .QEM cm H .mEm oom u .mEm DecoEumm
cofluuoumflp UHcOEumc psmuso HouanEHm m.m manme
73
Table 5.3 Simulator speed synthesis accuracy
X-band K-band
Desired Frequency Actual Frequency Actual
speed speed speed
(mph) (HZ) (mph) (H2) (mph)
10 339 10.80 738 10.24
20 639 20.35 1434 19.81
30 955 30.41 2135 29.72
40 1256 40.00 2883 40.01
50 1558 49.60 3618 50.26
60 1876 59.75 4345 60.49
70 2179 69.39 5065 70.36
80 2492 79.36 5797 80.24
90 2813 89.59 6513 90.08
100 3147 100.22 7228 99.96
Both channels are essentially identical.
VI . SUMMARY
The goal of the research effort described herein was to
design, implement, and evaluate an automatic test apparatus
for police radar speed measuring devices. The primary pur—
pose of this apparatus is to instruct radar devices under
controlled conditions and to educate operators in their
proper use. This chapter summarizes the development and
implementation of the traffic radar simulator which realizes
this goal.
6.1 The Traffic Simulator
The computer-controlled simulator tests X- and K-band
radar units in both the moving and stationary modes of
operation. One or two target vehicles of four different
sizes may be used in the simulation. They may start at any
realistic speed and position on the roadway, move in either'
direction, and accelerate or decelerate according to the
initial preprogrammed specifications. The patrol vehicle,
which can also be programmed to accelerate and decelerate,
may be set to any realistic speed and amplitude. The starting
time and duration of the test is completely controlled by
the operator. Moreover, at any point during the test, the
action may be frozen to examine a condition more closely.
Throughout the test, current values of speeds and distances
are continually updated and displayed on the front panel.
Three pairs of LED's also identify which target is out
front, which is moving fastest, and which has the strongest
signal.
Two additional modes of operation may be used with the
simulator. One mode establishes a stationary signal of a
desired amplitude and frequency on a single channel. The
other allows the operator to specify speeds for two channels
and vary the amplitude of one while holding the other
74
75
amplitude fixed. This second mode is a particularly useful
tool in determining speed/signal strength sensitivity and
selectivity.
This project commenced in January, 1980. The first two
months were spent in the definition phase. Here we specified
the types of radar devices that would be tested; the nature
and scope of these tests; operator interaction requirements;
and hardware precision, accuracy, and range requirements.
The next three months were spent designing and building the
main board and defining software requirements. After the
main board was built, software was written to control the
frequencies and amplitudes of the three signal channels.
While the software was expanding to include more features,
additional work was done to design and build the front
panel, including the compartment where the main board and
front panel are mounted. Construction of the hardware and
software was completed in November, 1980. Since that time
the simulator has been evaluated, used to test radar de-
vices, and used for demonstrations. Documentation has been
prepared to aid in the calibration and repair of the simu-
1ator, as well as materials necessary to instruct operators
in its use. Table 6.1 presents an assessment of the approxi-
mate total cost of the traffic simulator.
Important characteristics of the completed simulator
include the following:
* minimum warm-up time is 30 minutes;
* harmonic distortion is less than -16dB of the
fundamental;
* maximum target distance uncertainty is less than
two target vehicle lengths;
* maximum target speed uncertainty is less than 1 mph
for stationary-mode operation and less than 2 mph
for moving-mode operation;
* allowed speed range for targets or the patrol
vehicle is $199 mph for X-band radars or a
76
Table 6.1 Approximate simulator costs
Item Approximate cost
Main board $ 250
including XR8038 VCO's, AD534 multi-
pliers, AD561 D/A converters, and
other components
Display board 150
including MAN66lO displays and other
components
Computer 10,000
including Computer Automation LSI II,
minicomputer, Teletype terminal, 16-bit
I/O module, dual floppy-disk drive
Hardware 1,000
including front panel construction,
cabinet, power supplies, cables and
connectors
Test chamber 3,500
including materials for chamber, labor,
modulators, attenuators, and horns
Labor 12,500
including graduate assistantship (1100
hours) and part-time undergraduate
assistantship (500 hours)
TOTAL COST $27,400
77
maximum closing speed of 150 mph for K-band
radars;
target vehicles and the patrol vehicle may be
programmed to move at constant speeds or accelerate/
decelerate.
6.2 Tests on Individual Radar Units
Throughout the development of the simulator, demonstra-
tions of its capabilities have been given to several groups,
including radar operators, manufacturers, the Michigan Radar
Task Force formed by the Michigan State Police's Office of
Highway Safety Planning, and the public. In addition to
being used as an educational tool, the evaluation of indi-
vidual radar units has also begun. Many of the tests out-
lined in the proposed radar standards [3] have been performed
using the simulator. These include
*
Display Speed Lock Test: verify that the correct
vehicle speed is locked onto the display when a
target is present and the lock switch is activated;
Display Clear Tests: verify that the display read—
ing is cleared when a switch other than the lock
switch is activated;
Signal Processing Channel Sensitivity Tests: deter-
mine the minimum signal amplitude necessary to
acquire a target.
Low and High Speed Tests: verify that the specified
low and high speeds can be acquired for the targets
and the patrol car;
Patrol Speed Change Tests: determine that the radar
unit is capable of displaying the correct patrol speed
when the patrol speed is being increased or decreased
at a rate of three mph per second.
These tests are actually rather simple for the simulator
to perform since most only require one signal at a constant
78
frequency. Much more sophisticated tests are possible with
the simulator. For instance, the ability to
* simulate conditions for shadowing and combining;
* simulate roadway and patrol vehicle interference with
programmed noise sources;
* perform multiple target tests where the target
vehicle(s) and/or patrol vehicle dynamically change
speed;
* determine target selectivity and signal sensitivities
as a function of speeds and return signal strengths.
A decided advantage of the simulator over manual test proce-
dures is that simple or complex tests can be performed in a
repeatable manner.
6.3 Future Improvements
Using the existing hardware, additions could be made to
the software to make the tests more realistic. For instance,
stationary and moving-mode cosine effects could be taken
into account. More sophisticated speed profiles could be
incorporated with the vehicles changing speeds quadratically
or exponentially as well as linearly, or adding a feature
which allows the operator to specify a delay time before a
vehicle speed begins to change. Also, additional channels
could be added to simulate more than two targets without
changing the original design concepts, but a new cabinet
would have to be built to have space for the additional
hardware.
The traffic simulator in its present state was built
at minimum hardware expense. The computer and terminal used
were already available at the university. An alternative
approach would be to use a small desk-top computer with
built-in CRT display, bulk storage, keyboard, and printer,
such as a Hewlett Packard 9845. In addition, synthesizers
could be used for more accurate control of the frequencies
and amplitudes of the output signals. If this latter approach
79
is taken, the overwhelming majority of the simulator could
be constructed around off-the-shelf items.
6.4 Conclusions
The simulator meets or exceeds all of the design
requirements stated in Chapter 2. When the idea for the
simulator was conceived, federal performance and test standards
for radar speed measuring devices did not exist. In part
because of this, the simulator has much greater testing
capability than the standards call for, especially in the
area of dynamic testing.
This simulator clearly demonstrates that it is feasi-
ble to build a realistic automatic test apparatus to exer-
cise radar speed measuring devices under conditions similar
to those actually encountered on the nation's roads and
highways. To minimize cost and speed of development, we
elected to build the simulator around a.l6—bit minicomputer
(a Computer Automation LSI II) and a Teletype terminal.
Current advances in computer technology point the way toward
the next generation traffic radar simulator. The computer
could be a small, self-contained desk-top variety with
built-in color graphics. The CRT display could visually
illustrate the simulated target vehicles and patrol vehicle
moving along the roadway. Simultaneously, test conditions
could be displayed and hard-copy test documentation generated.
Even in its present form, this traffic simulator will
be a useful apparatus for several important user groups. It
can be used to evaluate the performance of newly introduced
or purchased radar devices and newly repaired equipment.
In addition, the simulator will be a useful tool in training
radar operators, as well as in the education of the legal
profession and the public at large regarding both the merits
and shortcomings of police radar speed measuring devices.
REFERENCES
Fisher, P.D., "Shortcomings of Radar Speed Measurement,"
IEEE Spectrum, Vol. 17, No. 12, December, 1980, pp. 28-31.
Police Radar: Is it Reliable?, National Highway Traffic
Safety Administration, U.S. Department of Transportation,
No. DOT/H8805254, February, 1980.
"Performance Standards for Speed Measuring Radar Devices,"
Federal Register, Vol. 46, No. 5, January 8, 1981, pp. 2097-
2119.
Naked Mini LSl Series Computer Handbook, Computer
Automation, Inc., October, 1974.
l6-Bit Input/Output Module, Product Number 13213-00,
Computer Automation, Inc., August, 1972.
"XR8038 Precision Waveform Generator," Exar Function
Generator Data Book, Exar Integrated Systems, Inc.,
April, 1979, PP. 30-33.
AD561: Low Cost lO-Bit Monolithic D/A Converter, Analog
Devices, September, 1976.
AD534: Internally Timed Precision 1C Multiplier, Analog
Devices.
"FND6710, FND6740 Dual Digit Numeric LED Displays,"
Optoelectronics Data Book, Fairchild, 1979, p. 4-48.
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