Range and range rate estimation for stepped frequency waveform with constant pulse repetition period
Systems and methods are provided and include a radar system that transmits radar signals within frames having radar chirps. The radar chirps have a stepped frequency waveform such that the initial and end frequencies are changed for subsequent chirps and have a constant pulse repetition period between chirps. The radar system performs range fast Fourier transform (FFT) processing and Doppler FFT processing on receive values corresponding to reflected signals from an object. The radar system estimates range and range-rate information about the object based on range FFT values and Doppler FFT values using a signal model and determines information about the object based on the estimated range and range-rate information. The signal model includes (1) a fast-time dimension term corresponding to samples within a radar chirp and (2) a slow-time dimension term corresponding to individual radar chirps within the frame, with the slow-time dimension term including a second degree term.
1 . A radar system comprising a processor and memory configured to:
control a transmitter/receiver to transmit radar signals within at least one frame having a plurality of radar chirps, the plurality of radar chirps having a stepped frequency waveform such that an initial transmit frequency and an end transmit frequency is changed for each subsequent chirp within the plurality of radar chirps, and the plurality of radar chirps having a constant pulse repetition period between chirps;
control the transmitter/receiver to receive and sample radar signals of the plurality of radar chirps reflected from at least one object to generate a plurality of receive values from the received and sampled radar signals;
perform range fast Fourier transform (FFT) processing and Doppler FFT processing on the plurality of receive values to generate range FFT values and Doppler FFT values;
estimate range and range-rate information about the at least one object based on the range FFT values and Doppler FFT values using a signal model; and
determine information about the at least one object based on the estimated range and range-rate information, the information about the at least one object including at least one of a location, a size, an orientation, a velocity, and an acceleration of the at least one object;
wherein:
the signal model includes at least one formula for a two-dimensional FFT map having (1) at least one quadratic fast-time dimension term (m 2 ), with m corresponding to an index indicating individually received samples within each radar chirp of the plurality of radar chirps reflected from the at least one object and (2) at least one quadratic slow-time dimension term (k 2 ), with k corresponding to an index indicating individual radar chirps within the plurality of radar chirps reflected from the at least one object; and
the radar system is located in a vehicle and the information about the at least one object is communicated to at least one of an autonomous driving system and a driver assistance system that controls at least one of a steering system, a braking system, and a throttle system of the vehicle based on the information about the at least one object.
2 . A method comprising:
transmitting, with a transmitter/receiver controlled by a processor and memory of a radar system, radar signals within at least one frame having a plurality of radar chirps, the plurality of radar chirps having a stepped frequency waveform such that an initial transmit frequency and an end transmit frequency is changed for each subsequent chirp within the plurality of radar chirps and the plurality of radar chirps having a constant pulse repetition period between chirps;
receiving and sampling, with the transmitter/receiver, radar signals of the plurality of radar chirps reflected from at least one object to generate a plurality of receive values from the received and sampled radar signals;
performing, with the processor and memory of the radar system, range fast Fourier transform (FFT) processing and Doppler FFT processing on the plurality of receive values to generate range FFT values and Doppler FFT values;
estimating, with the processor and memory of the radar system, range and range-rate information about the at least one object based on the range FFT values and Doppler FFT values using a signal model;
determining, with the processor and memory of the radar system, information about the at least one object based on the estimated range and range-rate information, the information about the at least one object including at least one of a location, a size, an orientation, a velocity, and an acceleration of the at least one object;
wherein:
the signal model includes at least one formula for a two-dimensional FFT map having (1) at least one quadratic fast-time dimension term (m 2 ), with m corresponding to an index indicating individually received samples within each radar chirp of the plurality of radar chirps reflected from the at least one object and (2) at least one quadratic slow-time dimension term (k 2 ), with k corresponding to an index indicating individual radar chirps within the plurality of radar chirps reflected from the at least one object; and
the radar system is located in a vehicle and the information about the at least one object is communicated to at least one of an autonomous driving system and a driver assistance system that controls at least one of a steering system, a braking system, and a throttle system of the vehicle based on the information about the at least one object.