U.S. patent application number 10/044606 was filed with the patent office on 2002-07-11 for doppler-based traffic radar system and related method of operation without detection.
Invention is credited to Jones, David W..
Application Number | 20020089443 10/044606 |
Document ID | / |
Family ID | 26856144 |
Filed Date | 2002-07-11 |
United States Patent
Application |
20020089443 |
Kind Code |
A1 |
Jones, David W. |
July 11, 2002 |
Doppler-based traffic radar system and related method of operation
without detection
Abstract
A Doppler-based traffic radar system determines a speed of a
moving target from a platform while substantially eliminating the
possibility of detection by an operator of the moving target
utilizing a traffic radar detector. The radar system includes a
controller or digital signal processor for limiting the period of
time the system is initially transmitting. The duration of the
initial transmission period is limited such that presently
available commercial radar detectors are substantially unable to
detect and/or elect not to report the presence of the radar signal.
Specifically, the radar system is adapted to monitor the number of
accumulated digital samples from a reflected portion of the radar
signal. Upon receipt of a number of samples sufficient to determine
the speed of the target, the radar system ends the initial
transmission. Once the samples are obtained, the radar system
determines the speed of the target and displays the speed.
Dependent upon the displayed rate of speed, the radar system
operator further has the ability to halt operation of the radar
system with respect to the particular target or to reinitiate
transmission of the transmit signal for subsequently tracking the
speed of the moving target both visually and aurally for a period
of time sufficient to support a citation.
Inventors: |
Jones, David W.; (Beaver
Dam, KY) |
Correspondence
Address: |
KING & SCHICKLI, PLLC
247 NORTH BROADWAY
LEXINGTON
KY
40507
US
|
Family ID: |
26856144 |
Appl. No.: |
10/044606 |
Filed: |
January 11, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10044606 |
Jan 11, 2002 |
|
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09583054 |
May 30, 2000 |
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60159631 |
Oct 15, 1999 |
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Current U.S.
Class: |
342/104 ;
342/114; 342/115 |
Current CPC
Class: |
G01S 7/022 20130101;
G01S 7/36 20130101; G01S 13/92 20130101 |
Class at
Publication: |
342/104 ;
342/114; 342/115 |
International
Class: |
G01S 013/58 |
Claims
1. A method for determining a speed of a moving target from a
platform having a traffic radar system while substantially
eliminating the possibility of detection by an operator of the
target utilizing a traffic radar detector comprising the steps of:
transmitting a radar signal from the platform toward the moving
target for a controlled period of time; receiving a portion of said
radar signal reflected from the moving target; calculating the
speed of the moving target; displaying the speed of the moving
target; and ending the transmission of said radar signal at the end
of said controlled period of time, said controlled period of time
being sufficiently short in duration to avoid detection by the
operator of the target but sufficiently long in duration to support
said calculating step, whereby the speed of the moving target is
initially determined without alerting the operator of the moving
target.
2. The method as claimed in claim 1 wherein said controlled period
of time is substantially less than fifty milliseconds.
3. A Doppler-based radar system for determining a speed of a moving
target from a platform while substantially eliminating the
possibility of detection by a traffic radar detector associated
with the moving target comprising: an oscillator to generate a
signal; an antenna to transmit the oscillator signal toward the
target for a limited period of time and to receive a return signal
reflected from the target; means for accumulating a predetermined
amount of the received return signal sufficient to calculate the
speed of the target and for calculating the speed of the moving
target; and wherein said limited period of time ends upon the
accumulation of the predetermined amount of the return signal.
Description
This is a continuation application of U.S. patent application Ser.
No. 09/583,054, filed Aug. 16, 2000, entitled "Doppler Based Radar
System and Related Method of Operation Without Detection."
TECHNICAL FIELD
[0001] The present invention relates generally to a Doppler-based
traffic radar system and, more particularly to such a system and
related method for determining the speed of a target without
detection by an operator of the target or subsequent targets
utilizing a traffic radar detector.
BACKGROUND OF THE INVENTION
[0002] Law enforcement officers have utilized Doppler-based traffic
radar systems to monitor vehicle speeds and enforce traffic speed
limit laws for many years. Throughout this period of time, numerous
improvements in both the underlying technology and in the specific
application of new processing techniques for the traffic radar
systems themselves, have afforded law enforcement officers greater
flexibility and improved reliability in carrying out their duties.
One such improvement evident in most traffic radar systems
presently being marketed includes the capability to more accurately
and reliably monitor the speed of certain vehicles while the patrol
vehicle is either in a stationary or a moving mode of operation. In
fact, the recent traffic radar systems can now successfully monitor
the speed of vehicles approaching the moving patrol vehicle in an
opposite lane.
[0003] In addition to these capabilities, such radar systems also
provide the law enforcement officer the capability to monitor a
group of target vehicles simultaneously and to determine the
fastest vehicle within the group and/or the vehicle presenting the
traditional strongest reflected return signal. Each of these new or
improved existing capabilities provide the law enforcement officer
with a more complete picture of the traffic environment and thus, a
more flexible and reliable basis for making more informed
decisions.
[0004] Despite all the improvements in both the underlying
technology utilized in these traffic radar systems and the radar
systems themselves, drivers who elect to drive at a speed above the
legal speed limit are still able to significantly reduce the
possibility that their illegal activity will be detected by a
traffic radar system by purchasing one of several commercially
available traffic radar detectors. Typical traffic radar detectors
are known in the art including those manufactured by such companies
as Uniden America Corporation and Cobra Electronics Corporation,
among others. These radar detectors are similarly technically
advanced and have enjoyed tremendous commercial success as
evidenced by the number of sales made to the public.
[0005] In an attempt to limit the effectiveness of these radar
detectors, most traffic radar systems are capable of operation in
both a continuous transmit mode and an intermittent transmit mode.
In the intermittent transmit mode, the operator manually triggers
the radar system dependent upon several conditions including for
example, the number of approaching vehicles or perhaps an initial
visual determination of the speed of a single approaching
vehicle.
[0006] While this intermittent mode of operating traffic radar
systems has limited the ability of commercial radar detectors to
detect their presence in some scenarios, many scenarios remain in
which the radar detectors remain effective. For example,
intermittent operation of radar systems in monitored zones having
heavy traffic patterns or continuous light traffic patterns may
trigger alert signals from a radar detector which are sufficient to
allow an alert and cautious driver in and/or approaching the
monitored zone to discern the presence and operation of the radar
system, thus avoiding detection.
[0007] Thus, while traffic radar systems are capable of a high
degree of accuracy with regard to vehicle speed measurements, they
are subject to detection by commercial radar detectors and thus
vehicle operators who elect to speed are often able to avoid
detection. Accordingly, a need is clearly identified for a traffic
radar system and related methods of operating such systems which
are capable of determining the actual speed of a target vehicle
while substantially eliminating the possibility of detection by an
operator of the target utilizing a radar detector system.
[0008] Necessarily, such a radar system and related methods would
substantially eliminate the ability of vehicle operators to rely on
radar detectors in furtherance of their illegal activities.
Accordingly, such a system would significantly increase their risk
of being detected while reducing the benefit of owning a radar
detector to a point where the number of individuals willing to
accept the risks associated with driving at a rate of speed above
the legal speed limit is significantly reduced.
SUMMARY OF THE INVENTION
[0009] In accordance with the purposes and objectives of the
present invention, a novel and improved Doppler-based traffic radar
system is provided that is adapted to control the period of time or
to limit the duration of an initial transmission of microwave
energy or radar signal from the radar system toward a moving
target. By limiting the duration of the initial transmission
period, presently available commercial radar detectors are
substantially unable to detect and/or elect not to report the
presence of the radar signal. Accordingly, the traffic radar system
is capable of determining the speed of a target while substantially
eliminating the possibility of detection by an operator of the
target utilizing a traffic radar detector.
[0010] In order to limit the duration of the initial transmission
period, the radar system of the present invention monitors the
amount of the microwave energy or radar signal portion reflected
from the moving target. Upon receiving a sufficient amount of the
reflected return signal to determine the speed of the target, the
radar system ends the initial transmission. Alternatively, the
radar system may simply end the initial transmission following a
limited period of time.
[0011] Once the reflected return signal is obtained, the radar
system calculates and displays the speed of the moving target.
Dependent upon the speed of the target, the radar system operator
has the ability to discontinue the monitoring of the speed of the
target or to reinitiate the transmission of microwave energy or
radar signal for subsequently calculating the speed of the target
and tracking the speed both visually and aurally for a period of
time sufficient to support a citation.
[0012] In accordance with an important aspect of the present
invention, the traffic radar system may be operated from a
stationary or a moving platform. During operation from a moving
platform, the radar system determines the speed of the platform for
calculating the speed of the moving target utilizing a portion of
the return signal reflected from a stationary object in a manner
well known in the art. Alternatively, a second antenna transmitting
the radar signal away from the target may be used to determine the
speed of the target.
[0013] The following description shows and describes a preferred
embodiment of this invention simply by way of illustration of one
of the modes best suited to carry out the invention. As it will be
realized, the invention is capable of other different embodiments,
and its several details are capable of modifications in various,
obvious aspects all without departing from the invention.
Accordingly, the drawings and descriptions will be regarded as
illustrative in nature and not as restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings incorporated in and forming a part
of the specification, illustrate several aspects of the present
invention, and together with the description serve to explain the
principles of the invention. In the drawings:
[0015] FIG. 1 is an overall schematic block diagram of the
Doppler-based radar system of the present invention;
[0016] FIG. 2 is a comparative illustration of three distinct
transmission periods versus the ability of presently available
radar detectors;
[0017] FIG. 3 is a detailed schematic block diagram of the
turnstile of the present invention;
[0018] FIG. 4 is a schematic block diagram of the speed determining
circuitry of the present invention.
[0019] FIG. 5 is a flow chart of the control algorithm for the
radar system; and
[0020] FIG. 6 is an overall schematic block diagram of an alternate
embodiment of the Doppler-based radar system of the present
invention.
[0021] Reference will now be made in detail to the present
preferred embodiment of the invention, an example of which is
illustrated in the accompanying drawings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] With reference now to the schematic block diagram of FIG. 1,
there is shown a present preferred embodiment of a Doppler-based
traffic radar system 10 for use in determining the speed of moving
targets T.sub.1, T.sub.2, . . . T.sub.n. More specifically, the
radar system 10 of the present invention is adapted to control the
period of time or to limit the duration of an initial transmission
of microwave energy or radar signal S1 from the radar system 10
toward at least one moving target T.sub.1, T.sub.2 . . . T.sub.n
including a selected moving target T.sub.1. By limiting the
duration of the initial radar signal transmission period, presently
available commercial radar detectors are substantially unable to
detect, or elect not to report, the presence of the radar signal
S1. Accordingly, the radar system 10 is able to determine the speed
of the selected moving target T.sub.1 while substantially
eliminating the possibility of detection by an operator of the
target T.sub.1 utilizing a traffic radar detector.
[0023] In order to be useful to radar detector operators,
commercial traffic radar detectors must be designed to discern
miscellaneous microwave signals received from devices such as
burglar alarms and garage door openers, among others allowed to
operate within the frequency ranges allocated to the operation of
traffic radar systems (e.g., X band, K band, and Ka band), from
traffic radar signals, and to effectively filter out these
undesired signals. The ability of commercial radar detectors to
discern one signal type from another is directly related to the
duration of the signal and varies from one manufacturer's brand of
radar detector to the next based for the most part on individual
manufacturer preferences.
[0024] In other words, some radar detectors are designed to be more
sensitive than others, thus potentially triggering a larger number
of false alarm signals than a competing radar detector. In
realizing these design preferences, the designers of these radar
detectors must balance the desired level of sensitivity of the
radar detector against the tolerance of radar detector operators
for false signals. A radar detector that triggers an alarm each
time a miscellaneous or false signal is received is practically
useless to the radar detector operator. In accordance with an
important aspect of the present invention, the minimum time period
P.sub.1 required to receive a portion of the radar signal reflected
from the moving target T.sub.1 sufficient to support the
determination or calculation of the speed of the target T.sub.1 is
short enough in duration (shown as P.sub.1 in FIG. 2) to be
substantially undetectable or judged to simply be insignificant or
miscellaneous microwave energy noise by these radar detectors and
not reported to the operator.
[0025] As shown in the timeline of FIG. 2, the detection zone of
commercial radar detectors wherein traffic radar signals are
detected and reported varies from manufacturer to manufacturer and
from a minimum time period P.sub.2 of approximately twenty-five
milliseconds to possibly more than one second. Heretofore, this
minimum time period P.sub.2 has been sufficient to allow detection
of nearly all traffic radar signals having a manually controlled
transmission period, i.e., radar signals initiated by an operator
of the radar system manually activating a momentary switch and
subsequently releasing the momentary switch. As further shown in
FIG. 2, the minimum time period required for this type of manual
activation of a radar system sufficient to transmit a radar signal
and receive a return signal indicative of target speed is indicated
as P.sub.3 and is approximately fifty milliseconds. Further, the
minimum time period required to receive a return signal and a
visual indication of the calculated target speed prior to releasing
the momentary switch to end the transmission period is indicated as
P.sub.4 and is approximately two hundred and fifty milliseconds.
These time periods P.sub.3 and P.sub.4 as determined through
experimentation are clearly within the noted radar detection zone
and provide the radar detector and the radar detector operator with
a good indication of the presence of a traffic radar signal.
[0026] As best shown in FIG. 1, the radar system 10 includes a
conventional Gunn diode oscillator 12 to generate a constant wave
radar signal S1. The radar or oscillator signal S1is passed through
a turnstile 14 to an antenna 16. In the present preferred
embodiment, the antenna 16 is a circularly polarized horn antenna
having a half-power beam width of twelve (12) degrees in azimuth
and elevation. The antenna 16 forms a transmitter to transmit the
radar signal S1 toward the moving targets T.sub.1, T.sub.2 , . . .
T.sub.n and a receiver to receive the reflected portion of the
radar signals or return signals S2.sub.T1, S2.sub.T2 . . .
S2.sub.Tn. The reflected radar signal S2.sub.T1, for example, is
indicative of the speed of the selected target T.sub.1. Although
the radar system 10 is capable of monitoring several targets, the
remainder of the detailed description will assume only one moving
target T.sub.1 to be present.
[0027] In accordance with well known Doppler principles, if the
target T.sub.1 is moving toward or away from the antenna, the
frequency (fr) of the transmitted radar signal S1 is shifted
(fr.+-.d) upon contacting the target T.sub.1, thus forming the
reflected radar signal S2.sub.T1 in accordance with the speed of
the target. The transmitted radar signal S1 is similarly reflected
by stationary objects or the roadway R forming a second reflected
radar signal S3.sub.R. This second reflected signal is indicative
of the speed of the platform or law enforcement vehicle supporting
the radar system 10 when the platform is moving.
[0028] As shown in FIG. 3, the reflected radar signal S2.sub.T1 is
received by the antenna 16 and forwarded to a duplexer 18 in a
manner well known in the art. The duplexer 18 isolates each
reflected radar signal (S2.sub.T1, S2.sub.T2, . . . S2.sub.Tn) from
the transmitted radar signal S1 and converts the linearly polarized
signal to a circularly polarized signal. Also within the turnstile
14, the reflected radar signal S2.sub.T1 is directed to a first
receive port 22 of a mixer 24, or mixer diode, where the reflected
radar signal S2.sub.T1 is combined with a coupled portion of the
transmitted radar signal S1.sub.p1 or leakage signal forwarded to a
second receive port 26 of the mixer 24. The mixer 24 combines the
signals to form a radar processing signal S4. The apparatus and
methods of transmitting and receiving radar signals described in
the three preceding paragraphs are considered to be basic
principles which are well known in the art. As shown in FIG. 4, the
resulting processing signal S4 is amplified by a preamplifier 30
and converted into digital samples D.sub.1-n, by an
analog-to-digital converter 32 for use by processor 34 in
determining the speed of the target T.sub.1.
[0029] As shown in the flow chart diagram of FIG. 5, transmission
of the radar signal S1 represented by box 58 is manually activated
by the radar system operator. Once the transmit switch or trigger
(not shown) is activated in box 50, the radar system 10 determines
the present mode of operation of the system in decision box 52. If
the radar system 10 is in a stealth mode in accordance with the
present invention, the oscillator 12 is keyed up and the receive
buffers 36 initialized for receiving a predetermined number of
reflected radar signal samples D.sub.1-n. Once the oscillator 12 is
keyed up and the receive buffers 36 are initialized, the
transmitter begins transmitting a radar signal S1 represented by
box 58. The digital samples D.sub.1-n are accumulated in the
receive buffers 36 or memory for use in determining the speed of
the target as indicated above for display in display 38. In
accordance with the broad teachings of the present invention, the
analog-to-digital conversion may alternately be accomplished in the
processor 34 and the receive buffers 36 or memory may be internal
to the processor 34 as is known in the art.
[0030] In the present preferred embodiment of the radar system 10,
transmission of the radar signal S I toward the moving target
T.sub.1 continues as monitored in box 60 until two-hundred and
fifty-six samples D.sub.1-256 are accumulated or buffered in memory
36 by processor 34. This accumulated group of samples D.sub.1-256
is sufficient to determine the speed of the target T.sub.1. The
speed of the target T.sub.1 however, may also be determined
utilizing a lesser number of samples D although with less
resolution as described further below.
[0031] The actual period of time required by the radar system 10 to
accumulate a predetermined number of samples, for example the
samples D.sub.1-256, is dependent upon several factors including
primarily the system hardware components, i.e., the processor or
converter selected for use in the radar system 10. For example, the
sampling rate of the present embodiment of the invention is
determined and thus effectively limited by the system clock (not
shown) which runs the processor 34 and triggers the
analog-to-digital converter 32. Simply increasing the
clock/processing speed necessarily reduces the period of time
required to receive a radar signal S2.sub.T1 reflected from the
moving target T.sub.1 that is sufficient to determine the speed of
the target. However, increasing the clock/processing speed also
reduces the resolution of the signal S2.sub.T1. Therefore, radar
system designers must balance these competing factors when
designing a radar system in accordance with the teachings of the
present invention. Of course, any combination of hardware
components is acceptable so long as the transmit period P.sub.1
remains less than the time period P.sub.2 required for detection by
commercial radar detectors.
[0032] Once the initial transmission of radar signal S1 ends as
indicated at box 62 and dependent upon the mode of operation of the
radar system 10, speed determining circuitry 28 is utilized as
indicated in box 64 and shown in FIG. 4 to calculate the speed of
the target T.sub.1 for display to the radar system operator. In
accordance with principles known in the art, the processor 34
transforms the digital samples D.sub.1-256 from the time domain to
the frequency domain to provide a frequency spectrum. More
specifically, a digital signal processor 34 is utilized in the
present preferred embodiment to perform a fast Fourier transform on
the digital samples D.sub.1-256. The resulting frequency spectrum
of a time to frequency domain transformation necessarily includes a
plurality of bins indicative of the Doppler components of the
targets T.sub.1, T.sub.2 . . . T.sub.n. More specifically, the
Doppler components include the amplitude and frequency of each
target. During operation, the radar system 10 searches the Doppler
components and selects a target according to an operating mode of
the radar system. For example, in a strongest target mode of
operation, the Doppler components are searched for a target having
the highest amplitude which is subsequently displayed to the radar
system operator by display 38. Similarly, in a fastest target mode
of operation, the Doppler components are searched for a target
having the highest frequency which is similarly displayed.
[0033] Dependent upon the displayed rate of speed, the radar system
operator has the ability to halt further operation of the radar
system 10 directed toward the selected target T.sub.1 by releasing
the transmit switch prior to an arbitrarily predetermined time
period or to allow transmission of the radar signal S1 to be
reinitiated by the radar system 10 for subsequently monitoring the
speed of the target T.sub.1 in order to provide a requisite Doppler
audio signal and vehicle tracking history. In accordance with an
important aspect of the present invention, the subsequent
monitoring and tracking is accomplished in a one-step operation
with no additional action required by the radar system
operator.
[0034] More specifically, once the initial transmission period ends
and the transmitter is turned off in box 62, a counter (not shown)
is initialized in box 66 and begins counting a predetermined period
of time as indicated in box 68. After the predetermined period of
time, preferably between one-eighth and one second, and most
preferably around one half second, the radar transmitter is turned
back on if the transmit switch remains activated as indicated in
decision box 70. The exact time period is not at all critical so
long as the radar system 10 has a sufficient amount of time to
calculate and display the speed of the target T.sub.1 and the radar
system operator can determine whether to continue monitoring the
selected target T.sub.1. If the transmit switch is not activated at
the end of the period of time, the transmitter remains in a dormant
state indicated in box 72 and the radar system 10 returns to a
stand by mode indicated in box 50.
[0035] If, on the other hand, the transmit switch remains
activated, the receive buffers 36 are re-initialized as indicated
in box 74 and the transmitter 16 reinitiates transmission of a
radar signal as indicated in box 76. In the present preferred
embodiment, the re-initialization of the receive buffers 36
includes establishing the buffers to receive 1024 digital samples
of the subsequently reflected radar signals. As indicated in boxes
78 and 80, the radar system 10 continues to transmit the radar
signal and calculate and display the speed of the target T.sub.1 as
long as the transmit switch remains activated. Once the switch is
released, the transmitter is turned off in box 72 and the radar
system 10 returned to a stand by mode in box 50.
[0036] In an alternate embodiment of the present invention, as
shown in FIG. 6, a second oscillator 13, turnstile 15, and antenna
17 may be utilized to obtain the speed of the platform supporting
the radar system 10. In the alternate embodiment, the second
antenna 17 is directed away from the oncoming targets T.sub.1 in
order to avoid detection. In this manner, the speed of the platform
can be determined on a continuous basis, if desired, independent of
the mode of operation of the radar system 10.
[0037] In summary, the overall flexibility afforded a radar system
operator and utility of the Doppler-based traffic radar system 10
of the present invention are significantly enhanced. This
improvement is accomplished by controlling or limiting the duration
of the initial radar signal transmission period such that presently
available commercial radar detectors are substantially unable to
detect and/or elect not to report the presence of the signal S1.
Specifically, the radar system 10 is adapted to accumulate a
predetermined number of digital samples D. Upon receipt of a
sufficient number of samples D.sub.1-n obtained from the reflected
radar signal S2.sub.T1 to determine the speed of the target
T.sub.1, the radar system 10 ends the initial transmission of the
radar signal S1. Once the samples D.sub.1-n are accumulated, the
radar system 10 determines the speed of the target T.sub.1 and
displays the speed in accordance with principles generally known in
the art.
[0038] The foregoing description of a preferred embodiment of the
invention has not been presented to be exhaustive or to limit the
invention to the precise form disclosed. Obvious modifications or
variations are possible in light of the above teachings. The
embodiment was chosen and described to provide the best
illustration of the principles of the invention and its practical
application to thereby enable one of ordinary skill in the art to
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. All
such modifications and variations are within the scope of the
invention as determined by the appended claims when interpreted in
accordance with the breadth to which they are fairly, legally and
equitably entitled.
* * * * *