Doppler complex FFT police radar with direction sensing capability

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.