Doppler complex FFT police radar with direction sensing capability

• US 6,646,591 B2
• Filed: 11/07/2001
• Issued: 11/11/2003
• Est. Priority Date: 07/21/1998
• Status: Expired due to Term

• Current Assignee: Applied Concepts Incorporated (Emerson Electric Company)
• Original Assignee: Applied Concepts Incorporated (Emerson Electric Company)
• Inventors: Gammenthaler, Robert S., Aker, John L.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US10/005,553
• Publication Number:
  US 20020080062A1
• Time in Patent Office: 734 Days
• Field of Search: 342/104, 342/105, 342/107, 342/109, 342/113, 342/114, 342/115, 342/118, 342/127, 342/133, 342/146, 342/147, 342/175, 342/192-197
• US Class Current: 342/114
• CPC Class Codes: G01S 13/589 measuring the velocity vector
• CPC Class Codes: G01S 7/04 Display arrangements
• CPC Class Codes: G01S 7/2883 using FFT processing

Abstract

A series of police doppler single mode radars and a multimode police doppler radar, all with direction sensing capability are disclosed. A quadrature front end which mixes received RF with a local oscillator to generate two channels of doppler signals, one channel being shifted by an integer multiple of 90 degrees in phase relative to the other by shifting either the RF or the local oscillator signal being fed to one mixer but not the other. The two doppler signals are digitized and the samples are processed by a digital signal processor programmed to find one or more selected target speeds. Single modes disclosed are: stationary strongest target; stationary, fastest target; stationary, strongest and fastest targets; moving, strongest, opposite lane; moving, strongest, same lane; moving, fastest, opposite lane; moving, fastest and strongest, opposite lane; moving, fastest, same lane; moving fastest and strongest, same lane.

Claims

1. A method for carrying out a stationary, strongest target search for targets travelling in one selected direction only in a Doppler police radar having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals, and having at least a single antenna, said method for searching comprising the steps of:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

applying a Hamming window or other DFT window to the data to minimize end effects;

performing a complex Fast Fourier Transform (FFT) on said sample data from said buffer for reach said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so a to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

searching the appropriate half spectrum defining speeds of targets travelling in the selected direction relative to said police radar for one or more frequency component(s) defining the speed of the strongest magnitude target travelling in a selected direction corresponding to the direction of targets the speeds of which re defined by the frequency components in said half spectrum searched by said searching step and converting the frequency of said component(s) to a speed and displaying said speed.

2. The method of claim 1 wherein said searching step is carried out in a half spectrum defined by preselected criteria.

3. The method of claim 1 wherein said searching step searches the half spectrum selected by an operator input command.

4. The method of claim 1 further comprising the step of giving a visible or audible indication of the direction of travel of said target.

5. A method of searching in stationary mode in a Doppler police radar having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and having at least a single antenna, said met ad for searching for a strongest target regardless of whether said strongest target is traveling away from said radar or approaching said radar and giving an indication with the target speed display which direction the target is travelling, comprising the steps of:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

applying a Hamming window or other OFT window to the data to minimize end effects;

performing a complex Fast Fourier Transform (FFT) of said sample data from said buffer for each said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so as to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

searching in both halves of said Fourier spectrum for one or more frequency components that define the speed of a strongest target and converting the frequency of said one or more frequency components to a displayed speed and providing an indication of the direction of travel of said strongest target based upon the half spectrum from which said one or more frequency components that define the speed of said strongest target were located.

6. A method of searching in stationary mode in a Doppler police radar having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and having at least a single antenna, said method for searching for a fastest target travelling in a single direction wherein a faster target is defined as any target travelling faster than a target with the strongest radar return signal which passes predetermined qualification tests, comprising the steps of:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

performing a complex Fast Fourier Transform (FFT) on said sample data from said buffer for reach said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so as to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

searching in the appropriate half of said Fourier spectrum to find one or more frequency components that define the relative speed of a fastest target travelling in a selected direction relative to said radar, and converting the frequency of said one or more frequency components to a displayed fastest target speed.

7. The method of claim 6 further comprising the step of applying a Hamming window other DFT window to said digital sample data to minimize end effects, and wherein said searching step is carried out in a half spectrum defined by preselected criteria to find a fastest target from a predetermined number of fastest target candidates all of which are faster than the speed of said target with the strongest radar return signal, said fastest target being the fastest of said fastest target candidates which pass one or more predetermined qualification tests to ensure said fastest target is not a false fastest target.

8. The method of claim 6 wherein said searching step searches the half spectrum selected by an operator input command.

9. The method of claim 6 further comprising the step of giving a visible or audible indication of the direction of travel of said target based upon the half spectrum in which said one or more frequency components were found.

10. The method of claim 6 further comprising the steps of finding and storing the true power and frequency of a predetermined number of the strongest signals in each spectrum aid using this information to screen fastest target candidates to eliminate false fastest targets caused by intermodulation mix products between one or more of said strongest signals or harmonics of one or more of said strongest signals.

11. The method of claim 10 further comprising the step of screening out false fastest targets at harmonics or intermodulation product frequencies of said strongest signals by examining the true power of said strongest signals and not eliminating fastest target candidates if the true power of said strongest signals is not strong enough to have generated a harmonic or intermodulation product at the frequency of a fastest target candidate thereby preventing said police radar from being blinded at these harmonic and intermodulation product frequencies.

12. The method of claim 10 further comprising the step of screening out false fastest target candidates b using a bleed through qualification test to determine if the fastest target candidate is or is not a real fastest target candidate based upon the fact that every target and false target which has a frequency component that appears in one half of said Fourier spectrum will have a paired frequency component in the other half of said Fourier spectrum and real targets will have a magnitude difference between the paired frequency components in the two halves of the spectrum because real targets are directional, but false targets such as harmonics and intermodulation products will not have a significant magnitude difference between the paired frequency components in the two halves of the spectrum since harmonics and intermodulation products do not have a direction.

13. A method of searching in stationary mode in a Doppler police radar having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and having at least a single antenna, said method for searching for a fastest target travelling either toward or away from said radar, wherein a fastest target is defined as any target travelling faster than a target with the strongest radar return signal which passes predetermined qualification tests, comprising the steps of:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

perform a complex Fast Fourier Transform (FFT) on said sample data from said buffer for each said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so as to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

searching in both halves of said Fourier spectrum to find one or more frequency components that define the speed of a fastest target travelling either away from or toward said radar, and converting the frequency of said one or more frequency components to a displayed speed.

14. The method of claim 13 further comprising the step of applying a Hamming window other window to said digital sample data to minimize end effects, and further comprising the step of giving a visible or audible indication of the direction of travel of said target based upon the half spectrum in which said one or more frequency components defining the speed of said fastest target were found, and wherein said fastest target is found from a predetermined number of fastest target candidates all of which are faster than the speed of said target with the strongest radar return signal, said fastest target being the fastest of said fastest target candidates which pass one or more predetermined qualification tests to ensure said fastest target is not a false fastest target.

15. The method of claim 13 further comprising the steps of finding and storing the true power and frequency of a predetermined number of the strongest signals in each spectrum a d using this information to screen fastest target candidates to eliminate false fastest targets caused by intermodulation mix products between one or more of said strongest signals or harmonics of one or more of said strongest signals.

16. The method of claim 15 further comprising the step of screening out false fastest targets at harmonics or intermodulation product frequencies of said strongest signals by examining the true power of said strongest signals and not eliminating fastest target candidates if the true power of said strongest signals is not strong enough to have generated a harmonic or intermodulation product at the frequency of a fastest target candidate thereby preventing said police radar from being blinded at these harmonic and intermodulation product frequencies.

17. The method of claim 13 further comprising the step of screening out false fastest target candidates b using a bleed through qualification test to determine if the fastest target candidate is or is not a real fastest target candidate based upon the fact that every target and false target which has a frequency component that appears in one half of said Fourier spectrum will have a paired frequency component in the other half of said Fourier spectrum an real targets will have a magnitude difference between the paired frequency components in the two halves of the spectrum because real targets are directional, but false targets such as harmonics and intermodulation products will not have a significant magnitude difference between the paired frequency components in the two halves of the spectrum since harmonics and intermodulation products do not have a direction.

18. A method of doing a moving mode, opposite lane, fastest target search in a Doppler police radar moving in a vehicle and having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and having at least a single antenna which either is pointed toward targets in front of said vehicle or is pointed at targets behind said vehicle, wherein a fastest target is defined as any target travelling faster than a target with the strongest radar return signal which passes predetermined qualification tests, comprising the steps:

acquiring buffer full of digital sample data for each said quadrature shifted channel;

performing a complex Fast Fourier Transform (FFT) on said sample data from said buffer for each said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so a to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

using said radar to determine the patrol speed of said police car from stationary object radar reflections in the approaching target half spectrum if said antenna is pointed toward targets in front of said police car or from stationary object radar reflections in the receding target half spectrum if said antenna is pointed at targets behind the police car, or by using other means for determining the patrol speed of said police car from the speed at which the wheels thereof are turning;

searching in the appropriate half spectrum, depending-upon which way the antenna is pointed, to determine the strongest target which has a relative speed greater than said patrol speed, and then searching in the appropriate half spectrum, depending upon which way the antenna is pointed, for the relative speed of the fastest target which has a relative speed which is higher than said strongest target'"'"'s relative speed, thereby eliminating same lane targets and restricting the fastest target relative speed to relative speeds above the strongest target relative speed; and

subtracting the patrol speed from said fastest target'"'"'s relative speed and displaying the speed of said fastest target.

19. The method of claim 18 further comprising the step of applying a Hamming window other DFT window to said digital sample data to minimize end effects, and further comprising the step of simultaneously displaying the speed of the strongest target with the speed of said fastest target, said fastest target being found from a predetermined number of fastest target candidates all of which are faster than the speed of said strongest target, said fastest target being the fastest of said fastest target candidates which pass one or more predetermined qualification tests to ensure said fastest target is not a false fastest target.

20. The method of claim 19 further comprising the step of simultaneously displaying said patrol speed with the speed of said strongest target and the speed of said fastest target.

21. The method of claim 18 further comprising a step for qualifying fastest target candidates using one or more qualification tests to eliminate false fastest targets caused by harmonics, double bounce reflections or other causes.

22. The method of claim 18 further comprising the step of simultaneously displaying the speed of said patrol car with the speed of said fastest target.

23. A method of doing a moving mode, opposite lane, strongest target search in a Doppler police radar moving in a police car and having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and has at least a single antenna which either is pointed toward targets in front of the police car or is pointed at targets behind the police car, comprising the steps:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

apply a Hamming window or other DFT window to the data to minimize end effects;

perform a complex Fast Fourier Transform (FFT) on said sample data from said buffer for each said quadrature shifted channel using a sample from one buffer as there axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so as to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

using said radar to determine the patrol speed of said police car from stationary object radar reflections in the approaching target half spectrum if said antenna is pointed toward targets in front of said police car or from stationary object radar reflection in the receding target half spectrum if said antenna is pointed at targets behind the police car, or by using other means for determining the patrol speed of said police car from a speedometer interface;

searching in the appropriate half spectrum, depending upon which way the antenna is pointed, to determine the strongest target which has a relative speed greater than said patrol speed thereby eliminating same lane strongest targets; and

subtracting the patrol speed from said strongest target'"'"'s relative speed and displaying the speed of said strongest target.

24. The method of claim 23 further comprising a step for qualifying strongest target candidates using one or more qualification tests to eliminate false strongest targets caused by harmonics, double bounce reflections or other causes.

25. A method of doing a moving mode, same lane, fastest target search in a Doppler police radar moving in a vehicle and having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and has at least a single antenna which either is pointed toward targets in front of said vehicle or is pointed at targets behind said vehicle, wherein a fastest target is defined as any target travelling faster than a target with the strongest radar return signal which passes predetermined qualification tests, comprising the steps:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

perform a complex Fast Fourier Transform (FFT) on said sample data from said buffer for each said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so as to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

using said radar to determine the patrol speed of said police car from stationary object radar reflections in the approaching target half spectrum if said antenna is pointed forward targets in front of said vehicle or from stationary object radar reflection in tile receding target half spectrum if said antenna is pointed at targets behind the vehicle, or by using a speedometer interface;

searching in both halves of the Fourier spectrum generated by said complex FFT for the relative speed of the strongest target which has a relative speed less than said patrol speed thereby eliminating opposite lane targets;

searching in both halves of the Fourier spectrum generated by said complex FFT for a fastest target having a relative speed less than said patrol speed, so as to eliminate opposite lane fastest targets, and with a relative speed which is such that relative to said relative speed of said strongest target said fastest target has an absolute speed higher than the absolute speed of said strongest target;

automatically determining said fastest target'"'"'s speed by calculating said patrol speed plus or minus said fastest target'"'"'s relative speed depending upon which half spectrum said fastest target was found in and whether said antenna is pointing toward targets in front of said vehicle or pointing toward targets behind said vehicle; and

displaying a least the speed of said fastest target.

26. The method of claim 25 further comprising the step of applying a Hamming window other window to said digital sample data to minimize end effects, and further comprising a step for qualifying fastest target candidates using one or more qualification tests to eliminate false fastest targets caused by harmonics, double bounce reflections or other causes, said fastest target being found from a predetermined number of fastest target candidates all of which are faster than the speed of said target with the strongest radar return signal (hereafter referred to as the strongest target), said fastest target being the fastest of said fastest target candidates which pass said step of qualifying fastest target candidates.

27. The method of claim 26 further comprising the steps of calculating the speed of said strongest target by automatically determining whether to add or subtract said patrol speed from said strongest target'"'"'s relative speed based upon which half spectrum said fastest target was found in and whether said antenna is pointing towards targets in front of said police car pointing toward targets behind said police car, and simultaneously displaying said strongest target'"'"'s speed along with said fastest target'"'"'s speed and said patrol speed.

28. A method of doing a moving mode, same lane, strongest target search in a Doppler police radar moving in a vehicle and having a quadrature front end receiver that generates two quadrature shifted channels of digital sample data from Doppler shifted reflected radar signals and has at least a single antenna which is pointed toward targets in front of said vehicle, comprising the steps:

acquiring a buffer full of digital sample data for each said quadrature shifted channel;

apply a Hamming window or other DFT window to said sample data to minimize end effects;

perform a complex Fast Fourier Transform (FFT)on said sample data from said buffer for each said quadrature shifted channel using a sample from one buffer as the real axis magnitude and a paired sample from the other buffer as the imaginary axis magnitude of each complex number input vector to said complex FFT so as to generate a Fourier spectrum with a first half with frequency components that define the speed of only approaching targets and a second half with frequency components that define the speed of only receding targets;

using said radar to determine the patrol speed of said police car from stationary object radar reflections in the approaching target half spectrum, or by using a speedometer interface;

searching in both halves of the Fourier spectrum generated by said complex FFT for the speed of the strongest target which has a relative speed less than said patrol speed thereby eliminating opposite lane targets;

automatically determining strongest target absolute speed as patrol speed plus or minus said strongest target'"'"'s relative speed based upon which half spectrum said strongest target was found in; and

displaying the absolute speed of said strongest target.

29. A method for interacting with a user to provide a user interface protocol to use a police radar which calculates a Fourier spectrum from digitized, doppler shifted radar reflection signals, said radar having circuitry and software to do, at operator selection, either moving or stationary searches and having circuitry and software to search for, at operator selection, approaching targets only or receding targets only in either moving or stationary search mode to determine the speed of at least one selected target, comprising the steps of:

receiving an operator input command indicating operator selection between moving mode searching or stationary mode searching;

regardless of whether moving mode or stationary mode searching has been selected, receiving an operator input command indicating operator selection between an approaching target search only or a receding target search only; and

if stationary, receding targets only search mode has been selected searching said Fourier spectrum for the strongest receding only target and displaying the displaying the speed thereof.

30. The method of claim 29 wherein said radar includes circuitry and software to perform strongest and fastest target searches, further comprising the steps:

receiving an operator input command indicating operator selection between a desire to see the speeds of a fastest receding target as well as a strongest receding target or only a strongest receding target; and

if the operator requested to see the speeds of a fastest receding target as well as a strongest receding target, searching said Fourier spectrum for a fastest receding target and displaying the speed of said fastest receding target along with the speed of said strongest receding target.

31. The method of claim 29 wherein said radar includes circuitry and software to perform either strongest or fastest target stationary searches further comprising the steps:

receiving an operator input indicating operator selection between a desire to see a fastest receding target only or a strongest receding target only; and

if the operator indicated a desire to see the speed of the fastest receding target only, searching said Fourier spectrum for a fastest receding target, and displaying the speed of said fastest receding target only, but if the operator indicated a desire to see the speed of the strongest receding target only, displaying only the speed of the strongest receding target.

32. A method for interacting with a user to provide a user interface protocol to use a police radar which calculates a Fourier spectrum from digitized, doppler shifted radar reflection signals, said radar having circuitry and software for doing moving or stationary searches and searching for approaching targets only or receding targets only in either moving or stationary search mode to determine the speed of at least one selected target, comprising the steps of:

receiving a input command from an operator indicating operator selection between moving ode searching or stationary mode searching;

regardless of whether moving mode or stationary mode searching has been selected, receiving an input command from an operator indicating operator selection between an approaching target search only or a receding target search only; and

if stationary, approaching targets only search mode has been selected, searching said Fourier spectrum for the strongest approaching target and displaying the speed thereof.

33. The method of claim 32 wherein said radar includes circuitry and software to perform strongest and fastest target stationary searches and further comprising the steps:

receiving an operator input command indicating operator selection between a desire to see a fastest approaching target as well as a strongest approaching target or only a strongest approaching target; and

if the operator indicated a desire to see a fastest approaching target as well as a strongest approaching target, searching said Fourier spectrum for a fastest approaching target, and displaying the speed of said fastest approaching target along with the speed of the strongest approaching target.

34. The method of claim 32 further comprising the steps:

receiving an operator input command indicating operator selection between a desire to see a fastest approaching target only or a strongest approaching target only; and

if said operator indicated a desire to see the speed of only a fastest approaching target, searching said Fourier spectrum for a fastest approaching target, and displaying the speed of said fastest approaching target only, but if the operator indicated desire to see the speed of only a strongest approaching target, displaying the speed of the strongest approaching target only.

35. The method of claim 32 wherein said radar includes circuitry and software to carry out strongest and fastest target stationary searches further comprising the steps:

receiving an operator input command indicating operator selection between a desire to see a fastest approaching target as well as a strongest approaching target or only a strongest approaching target; and

if the operator indicated a desire to see a fastest approaching target as well as a strongest approaching target, searching said Fourier spectrum for a fastest approaching target, and displaying the speed of said fastest approaching target along with the speed of the strongest approaching target.

36. A method for interacting with a user to provide a user interface protocol to use a direction sensing police radar which has quadrature front end circuitry to transmit radar signals and receive Doppler shifted reflected radar signals and mix said reflected radar signals down in frequency using a local oscillator signal at the frequency of said transmitted radar signals and a quadrature mixer so as to generate two channels of Doppler signals, and circuitry to convert each of said two channels of audio frequency Doppler signals to generates two streams of digital samples, said police radar further comprising a digital signal processor programmed to receive both said streams of digital samples and calculate a complex Fourier spectrum therefrom, said radar further comprising software for controlling said digital signal processor to do moving or stationary searches and, in moving mode, search for same lane targets only or opposite lane targets only to determine the speed of at least one selected target, comprising the steps of:

receiving an operator input command indicating operator selection between moving mode searching or stationary mode searching;

if moving mode searching has been selected, receiving an operator input command indicating operator selection between a same lane target search only or an opposite lane target search only;

if moving made, same lane searching has been selected, carrying out a search of said complex Fourier spectrum to determine and display the speed of at least one target including a strongest same lane target and without the need for operator input telling the radar whether the same lane target the operator is visually tracking which he or she believes is identical to a strongest same lane target said radar is tracking is moving faster or slower than a patrol car in which said radar is operating.

37. The method of claim 36 wherein said radar further comprises software for controlling said digital signal processor to perform strongest and/or fastest target searches, further comprising the steps:

receiving a operator input command indicating operator selection between a desire to see the speed of a fastest same lane target as well as the speed of a strongest same lane target or only the speed of a strongest same lane target; and

if the operator indicated a desire in moving mode to see the speed of a fastest same lane target as well as the speed of a strongest same lane target, searching said Fourier spectrum for a fastest same lane target, and using the patrol speed to calculate the speed of said fastest same lane target without the need for any operator input telling the radar whether a fastest same lane target being visually tracked by the operator which the operator believes is the same fastest same lane target being tracked by said radar is moving faster or slower than the patrol car in which said radar is operating, and displaying the speed of the fastest same lane target along with the speed of the strongest same lane target, but if the operator indicated a desire to see the strongest same lane target only, displaying only the speed of said strongest same lane target.

38. The method of claim 36 wherein said radar includes software to control said digital signal processor to perform strongest and fastest target searches, further comprising the steps:

receiving an operator input command indicating operator selection between a desire to see the speed of a fastest same lane target only or only the speed of a strongest same lane target; and

if the operator indicated a desire to see the speed of a fastest same lane target only, searching said Fourier spectrum for a fastest same lane target, and using the patrol speed to calculate the speed of said fastest same lane target and displaying the speed of said fastest same lane target only, but if said operator indicated a desire to see the speed of only a strongest same lane target, displaying only the speed of said strongest same lane target.

39. A method for interacting with a user to provide a user interface protocol to use a direction sensing police radar which calculates a Fourier spectrum from digitized, doppler shifted radar reflection signals, said radar having circuitry and software for processing said Fourier spectrum to do moving or stationary searches and search for approaching targets only or receding targets only in stationary search mode or, in moving mode, search said Fourier spectrum for opposite lane only targets or same lane only targets so as to determine the speed of at least one selected target, comprising the steps of:

1) receiving an operator input command indicating operator selection between moving mode searching or stationary mode searching;

2) if stationary mode searching has been requested, receiving an operator input command indicating operator selection between an approaching target search only or a receding target search only; and

3) if moving mode searching has been requested, receiving an operator input command indicating operator selection between same lane target only searching or opposite lane target only searching; and

4) responding to said operator input commands to do the requested search of said complex Fourier spectrum.

40. The method of claim 39 wherein said radar includes circuitry and software to do strongest and fastest target searches, further comprising the steps:

receiving an operator input command indicating operator selection between a desire, in whatever search mode the radar is operating, to see the speed of a fastest target as well as the speed of a strongest target or only the speed of a strongest target; and

responding to the operator input commands by doing each requested search.

41. A method for interacting with a user to provide a user interface protocol to use a direction sensing police radar which has quadrature front end circuitry to transmit radar signals and receive Doppler shifted reflected radar signals and convert said signals to digital data, said police radar further comprising a digital signal processor programmed to receive said digital data and do a complex Fourier conversion calculation thereupon to generate a complex Fourier spectrum having an approaching target half and a receding target half, said radar further comprising software for controlling said digital signal processor to do moving or stationary searches and, in moving mode, search for same lane targets only or opposite lane targets only to determine the speed of at least one selected target, comprising the steps of:

receiving an operator input command indicating operator selection between moving mode searching or stationary mode searching;

if moving mode searching has been selected, receiving an operator input command indicating operator selection between a same lane target search only or an opposite lane target search only; and

if a moving mode, same lane search has been requested, searching said complex Fourier spectrum to determine and display the speed of at least one strongest target automatically without any need for operator input telling said radar whether a strongest target the operator is visually tracking is moving faster or slower than the patrol car in which said radar is operating in moving mode.

42. A method for interacting with a user to provide a user interface protocol to use a direction sensing police radar which has quadrature front end circuitry to transmit radar signals and receive Doppler shifted reflected radar signals using either a front antenna or a rear antenna and mix said reflected radar signals down in frequency to the audio range using a local oscillator signal at the frequency of said transmitted radar signals in a quadrature mixer using a relative phase shift of an integer multiple of 90 degrees so as to generate two channels of audio frequency Doppler signals, and circuitry to convert each of said two channels of audio frequency Doppler signals to generate two streams of digital samples, said police radar further comprising a digital signal processor programmed to receive both said streams of digital samples and do a complex Fourier conversion calculation thereupon to generate a complex Fourier spectrum having an approaching target half and a receding target half, said radar further comprising software for controlling said digital signal processor to do moving or stationary searches and, in moving mode, searching for same lane targets only or opposite lane targets only to determine the speed of at least one selected target, comprising the steps of:

receiving an operator input command indicating operator selection between moving ode searching or stationary mode searching;

if moving mode searching has been selected, receiving an operator input command indicating operator selection between a same lane target search only or an opposite lane target search only;

in moving mode where either same lane or opposite lane searches have been selected, receiving an operator input command selecting operation from either said front antenna or said rear antenna; and

carrying out a search of said complex Fourier spectrum to determine and display the speed of at least one target, said search being controlled by said operator input commands.

43. The process of claim 42 further comprising the steps of using a quadrature front end circuit to generate two streams of sample data from reflected, doppler shifted radar signals transmitted by said radar and controlling a computer which is part of said circuitry with a program which is part of said software to receive said two streams of digital sample data generated from said reflected, doppler shifted radar signals and calculate a complex Fourier transform spectrum therefrom, and controlling said computer with said program to perform one or more operator requested searches in said complex Fourier spectrum, and controlling said computer with said program to use bleed through characteristics and non directionality characteristics of false targets as screening characteristics during said one or more operator requested searches to screen out false targets.