Target persistence filter for multi-frequency automotive radar system

In an automotive collision avoidance system in a vehicle having a Doppler radar system with means for successively transmitting a radar beam at a plurality of successive intervals and for receiving echo signals corresponding to the plurality of successive intervals from at least one target within the radar beam, a target persistence and environment filter comprising:

• a. means for receiving a first and a second echo signal from at least one target, for comparing the relative phase difference between the first and the second received echo signals, and for generating a signal as a result of such comparison to indicate change in relative distance of such at least one target with respect to the vehicle, the generated signal having a first value when such relative distance is decreasing and a second value when such relative distance is increasing;
• b. signal delay means, coupled to the generated signal, and including a programmable time delay means for determining a time period in accordance with a programmed value, for delaying the generated signal for a time period determined by the programmed value of the time delay means, the signal delay means generating an output signal having a first value if the generated signal has its first value for the determined period of time, and having a second value if the generated signal has its second value during the determined period of time;
• c. speed determinatin means, for determining the speed of the vehicle;
• and
• d. programming means, coupled to the signal delay means and to the speed determination means, for programming the time delay means with a value whereby the duration of the time period is proportional to the speed of the vehicle;
• whereby only echo signals from targets persisting in the radar beam for the determined period of time are further processed by the radar system.

In an automotive collision avoidance system in a vehicle having a Doppler radar system with means for successively transmitting a radar beam at a plurality of successive intervals and for receiving echo signals corresponding to the plurality of successive intervals from at least one target within the radar beam, a target persistence and environment filter comprising:

• a. a bistable latch for receiving a first and a second echo signal from at least one target, for comparing the relative phase difference between the first and the second received echo signals, and for generating a signal as a result of such comparison to indicate change in relative distance of such at least one target with respect to the vehicle, the generated signal having a first value when such relative distance is decreasing and a second value when such relative distance is increasing;
• b. a resettable shift register, coupled to the output of the bistable latch, for delaying the generated signal a selected number of bit shifts, the shift register generating an output signal having a first value if the generated signal has its first value for the selected number of bit shifts, and being reset to a second value if the generated signal has its second value during the selected number of bit shifts;
• c. speed determination means, for determining the speed of the vehicle;
• and
• d. programming means, coupled to the resettable shift register and to the speed determination means, for programming the resettable shift register with a selected bit shift value whereby the selected number of bit shifts is proportional to the speed of the vehicle;
• whereby only echo signals from targets persisting in the radar beam for the selected number of bit shifts are further processed by the radar system.

In an automotive collision avoidance system in a vehicle having a Doppler radar system with means for successively transmitting a radar beam at a plurality of successive intervals and for receiving echo signals corresponding to the plurality of successive intervals from at least one target within the radar beam, a target persistence and environment filter comprising:

• a. a bistable latch having a clock input coupled to a first echo signal from at least one target, and a data input coupled to a second echo signal from at least one target, for generating a signal indicative of the relative phase difference between the first and the second received echo signals, such relative phase difference corresponding to a change in relative distance of such at least one target with respect to the vehicle, the generated signal having a first value when such relative distance is decreasing and a second value when such relative distance is increasing;
• b. a resettable shift register, coupled to the output of the bistable latch, for delaying the generated signal a selected number of bit shifts, the shift register generating an output signal having a first value if the generated signal has its first value for the selected number of bit shifts, and being reset to a second value if the generated signal has its second value during the selected number of bit shifts;
• c. speed determination means, for determining the speed of the vehicle;
• and
• d. programming means, coupled to the resettable shift register and to the speed determination means, for programming the resettable shift register with a selected bit shift value whereby the selected number of bit shifts is proportional to the speed of the vehicle;
• whereby only echo signals from targets persisting in the radar beam for the selected number of bit shifts are further processed by the radar system.