US-12618969-B2 - Range and range rate estimation for stepped frequency waveform with constant pulse repetition period

Abstract

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.

Inventors

• BOYI GAO

Assignees

• Aptiv Technologies AG

Dates

Publication Date

20260505

Application Date

20230919

Claims (2)

1. 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. 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.

Description

FIELD The present disclosure relates to radar systems and methods and, more particularly, to radar systems and methods that determine range and range rate estimates for a stepped frequency waveform having a constant pulse repetition period. BACKGROUND This section provides background information related to the present disclosure which is not necessarily prior art. Automotive radar sensors are used in vehicle sensing systems to determine information about objects in the environment of the vehicle, such as the location, size, orientation, velocity, and acceleration of objects in the environment of the vehicle. The sensed information can, for example, be used by other vehicle systems, such as autonomous driving systems and/or advanced driver assistance systems (ADAS), etc., to control steering, braking, throttle, and/or other vehicle systems. A radar system may transmit a number of radar chirps within a particular transmit frame and then receive signals corresponding to the transmitted chirps within the transmit frame reflected from an object within the environment of the vehicle. The frequency of the radar signal may vary during each individual chirp. For example, in some radar systems the transmitted signal may start at an initial frequency and then increase or decrease over the time period of the chirp to an end frequency. In some conventional radar systems, the initial frequency and the end frequency of each chirp can stay the same for each chirp over the course of the transmit frame. Other radar systems, however, may utilize a stepped frequency waveform such that the initial frequencies and end frequencies of the transmitted signals change from chirp to chirp. For example, a radar system may utilize a step-down frequency waveform such that the initial frequency and end frequency of each subsequent chirp is lower than the initial frequency and end frequency of the previous chirp. Alternatively, a radar system may utilize a step-up frequency waveform such that the initial frequency and end frequency of each subsequent chirp is higher than the initial frequency and end frequency of the previous chirp. Additionally, in some radar systems the time period between each chirp, referred to as the pulse repetition period (“PRP”), can remain constant for all chirps within a transmit frame. Alternatively, other radar systems can be configured to vary the PRP between chirps over the transmit frame such that the time between chirps changes over the course of the transmit frame. Radar systems can use signal models to process received radar signals reflected off of an object and determine range and range rate information of the object. Using a signal model developed for stepped frequency waveforms with variable PRP in a radar system that utilizes a constant PRP, however, can introduce errors. SUMMARY This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features. In accordance with the present disclosure, a radar system comprising a processor and memory configured 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. The processor and memory are further configured to receive and sample radar signals reflected from at least one object to generate receive values from the received and sampled radar signals. The processor and memory are further configured to perform range fast Fourier transform (FFT) processing and Doppler FFT processing on the receive values to generate range FFT values and Doppler FFT values. The processor and memory are further configured to 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. The processor and memory are further configured to determine information about the object based on the estimated range and range-rate information, the information about the object including at least one of a location, a size, an orientation, a velocity, and an acceleration of the at least one object. The signal model includes (1) at least one fast-time dimension term that corresponds to individual receive samples within each radar chirp of the plurality of radar chirps and (2) at least one slow-time dimension term that corresponds to individual radar chirps within the plurality of radar chirps, and the at least one slow-time dimension term includes at least one second degree term corresponding to individual radar chirps within the plurality of radar chirps. In other features, the at least one slow-time dimension term is quadratic. In other features, the at least one slow-time dimension term includes an index for the indi