Communications: directive radio wave systems and devices (e.g. – Determining velocity – Combined with determining distance
Reexamination Certificate
2002-11-05
2004-09-28
Gregory, Bernarr Earl (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Determining velocity
Combined with determining distance
C342S027000, C342S028000, C342S070000, C342S104000, C342S105000, C342S118000, C342S175000, C342S194000, C342S195000, C342S196000
Reexamination Certificate
active
06798374
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to Doppler shifted radar and more specifically to target identification with respect to surveillance of moving vehicles. More particularly, it relates to an improved system using two or more continuously transmitting frequencies directed toward target vehicles whereby the phase difference of the reflected Doppler signals is scaled to a target range. As such the system can detect the speed of each target within a specified range including the closest, the next closer, next faster, fastest closing vehicle, etc.
BACKGROUND OF THE INVENTION
One of the most common and useful tools in the enforcement of vehicular speed limit laws has been the use of Doppler radar. In a Doppler radar system, a microwave signal is transmitted to a vehicle and then reflected off the vehicle. When the reflected signal is received back at the Doppler radar system, a change of frequency in the signal is proportional to the vehicle speed. That shift in signal frequency is known as the “Doppler Effect”. The shift in frequency is measured and the resulting vehicle speed is calculated and displayed on the radar system, thereby eliminating any need for calculations for the system operator (police officer) in the vehicle that has the radar system. The radar system may be permanently mounted in the vehicle or the system may be a portable hand-held unit with a display. If a vehicle speed is measured over the speed limit, the officer may pursue the vehicle and issue a speeding ticket.
In actual application, a problem arises when more than one vehicle is in the visual sight of the operator. The problem is the identification of which vehicle's speed is displayed when more than one vehicle is in a position to reflect the microwave signal. Conventional radar is always instructed to display the speed of the “strongest” radar return in the “strongest target window”, most often the leftmost window of the radar display. Since the round trip strength of the radar signal drops off at 1/R
4
(where R is the distance to the target), it can be somewhat assured that the strongest return is also comparable to the closest target. The using system operator will develop a tracking history (speed values over time) and mentally correlate the reading from the actual viewed traffic. When a speed violator has been detected and confirmed (through the tracking history), then the operator may issue a citation.
The originating signal is usually conical shaped and emits a half angle of six degrees. As the range is increased, more vehicles can come within the “measurement cone” and reflect back to the system. The best reflector of the radar is a function of the vehicle design, that is, vehicle size, shape, grills, headlights, bumpers, large flat surfaces, etc. When a plurality of vehicles with various geometric shapes enters a radar area, there may be a situation where the identification of a target vehicle is indeterminate. All of these factors contribute to the problem of reliable vehicle identification.
When citizens come into contact with law-enforcement personnel, it is important that they feel that they have been dealt with in a fair and consistent manner. Thus, it is important that traffic citations be based on factual matter and not be left to any discretion of the law-enforcement officer. Police traffic radar has always suffered from the inability to accurately report the range of, a target object. It has always been taught to system operators that the strongest return corresponds to the closest target. Unfortunately, this only applies to vehicles of the same size, shape, etc. Vehicles that vary significantly in their geometric properties can produce equally varying signal strengths. Common roadway traffic is usually composed of a multitude of vehicle sizes, shapes, etc. ranging from motorcycles, sports cars to large eighteen-wheeler trucks. These varying targets increase the difficulty of correctly identifying the closest vehicle based on signal strength alone.
There are many methods to detect the relative or exact range of target vehicles. These methods include pulsing, modulation of the carrier wave and alternately transmitting more than one carrier frequency towards a target. The pulsing methods have drawbacks with FCC limitations and the modulation methods tend to be more complex and thus more expensive.
The present invention will describe a means that accurately determines the exact or relative range to a target while being relatively inexpensive, stable, and accurate over time and temperature variations. The present invention resolves issues of accurate target identification regarding the radar operator use of discretion when operating the radar system. The present invention will provide a means for the radar operator to correctly identify the closest target in range thereby substantially improving target identification. The present invention utilizes two or more “continuously” transmitting frequencies directed toward the moving target(s) whereby the phase difference of the reflected Doppler signals is scaled to a target range.
SUMMARY OF THE INVENTION
The main aspect of the present invention is to provide for an improved vehicle radar system whereby two or more continuous transmitting frequencies provide for correct identification of the closest target in range, thus improving target identification.
Another aspect of the present invention is to provide the relative range of a target by comparing the phase differences between the Doppler signals.
Another aspect of the present invention is to provide for a longer detection range.
Another aspect of the present invention is to provide for better stability and accuracy over the lifetime of the radar unit.
Another aspect of the present invention is a relatively inexpensive manufacturing cost and compact size.
Another aspect of the present invention is the ability to combine the range and speed.
Another aspect of the present invention, an alternate embodiment, is to provide a speed for a plurality of relative targets coinciding with each targets range.
Another aspect of the present invention, an alternate embodiment, is to report and/or display the relative speeds of the closest, next closest, etc. vehicles.
Another aspect of the present invention is to allow the operator of the radar system to control the display to show the speed of the closest, then switch to the next closest or again next closest vehicle as desired.
Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.
The present invention employs two or more continuous frequencies and is thus a multiple frequency transmitting radar system (MFTRS). The MFTRS can determine the relative range to a target by comparing the phase differences between the returned Doppler signals. This phase difference is directly proportional to the range of the target. Determination of the relative range of a vehicle will then allow the MFTRS to display the speed of the closest vehicle.
The use of continuous transmission of two or more frequencies overcomes many problems with prior art, which used alternating transmitting signals, thereby introducing errors into a system. Further detail of the MFTRS will be described below.
DETAILED DESCRIPTION OF INVENTION
The MFTRS provides continuous transmitting frequencies for correct identification of the closest target in range (and its speed), thus improving target identification. The transmitting frequencies are phase locked to a reference offset to provide a stable output over time and temperature. The MFTRS utilizes the combining action of these continuous transmission signals and eliminates many errors commonly found in prior art. A combiner circuit takes the transmitted frequencies from two separate microwave sources and combines (adds) them together before being transmitted. The combiner circuit will accurately perform the
Decatur Electronics Inc.
Gregory Bernarr Earl
Martin Rick
Patent Law Offices of Rick Martin P.C.
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