Parameter defined stepped frequency waveform for radar
This document describes techniques, apparatuses, and systems for a parameter defined stepped frequency waveform for a radar system. A radar system transmits radar transmit signals including a parameter defined stepped frequency waveform with a specific change in frequency between chirps. The specified change in frequency may increase the signal to noise ratio of radar receive signals reflected off an object in the field of view. The radar receive signals may then be transformed into the frequency domain to determine a range and range rate of the object in the field of view. The range and range rate determined from the representation of the radar receive signals in the frequency domain may be output to a radar tracker to enable tracking of the object in the field of view. In doing so, accurate radar tracks may be generated that robustly track objects in the field of view of the radar system.
1. A method comprising:
transmitting, by a radar system, radar transmit signals representing a parameter defined stepped frequency waveform for a frame having at least two chirps including an initial chirp in the frame and a current chirp in the frame, the transmitting of the radar transmit signals representing the parameter defined stepped frequency waveform including,
determining a pulse frequency for the current chirp relative to a pulse frequency of the initial chirp that cancels a coupling term in a frequency domain representation of radar receive signals received in response to the transmitting of the radar transmit signals based on: i) a starting frequency of the initial chirp; ii) a slope of the initial chirp; iii) an index of the current chirp; and iv) a pulse repetition period of the initial chirp, and
outputting the current chirp of the parameter defined stepped frequency waveform having the pulse frequency that cancels the coupling term in the frequency domain representation of the radar receive signals;
receiving, by the radar system, the radar receive signals representing the parameter defined stepped frequency waveform reflected off of an object in a field of view of the radar system;
performing a transformation of the radar receive signals to determine a representation of the radar receive signals in the frequency domain with the representation of the radar receive signals in the frequency domain having the coupling term cancelled therefrom;
determining a range and a range rate associated with the object in the field of view based on the representation of the radar receive signals in the frequency domain; and
outputting, to a radar tracker, the range and range rate associated with the object in the field of view to enable radar tracking of the object in the field of view.
2. The method of claim 1 , wherein the parameter defined stepped frequency waveform for the frame further comprises a delay time of the current chirp from a beginning of the frame based on:
the starting frequency of the initial chirp;
the index of the current chirp; and
the pulse repetition period of the initial chirp.
3. The method of claim 1 , wherein performing a transformation of the radar receive signals to determine the representation of the radar receive signals in the frequency domain comprises:
performing a two-dimensional Fourier transform of the radar receive signals to generate a two-dimensional representation of the radar receive signals in the frequency domain, the two-dimensional representation including a fast-time dimension and a slow-time dimension.
4. The method of claim 3 , wherein determining the range and the range rate associated with the object in the field of view based on the representation of the radar receive signals in the frequency domain comprises:
determining a peak of the two-dimensional representation of the radar receive signals; and
determining the range and the range rate corresponding to the peak of the two-dimensional representation of the radar receive signals.
5. The method of claim 4 , wherein determining the range and the range rate corresponding to the peak of the two-dimensional representation of the radar receive signals comprises:
determining a fast-time frequency and a slow-time frequency associated with the peak of the two-dimensional representation of the radar receive signals; and
determining the range and the range rate corresponding to the fast-time frequency and the slow-time frequency associated with the peak of the two-dimensional representation.
6. The method of claim 3 , wherein performing the transformation of the radar receive signals to determine the representation of the radar receive signals in the frequency domain further comprises:
compensating for a phase contribution of the radar receive signals in the slow-time dimension based on range values of the two-dimensional representation of the radar receive signals.
7. The method of claim 6 , wherein:
the two-dimensional representation of the radar receive signals further comprises a collection of range values; and
compensating for the phase contribution of the radar receive signals in the slow-time dimension based on the range values of the two-dimensional representation of the radar receive signals comprises:
compensating, for a portion of the collection of range values, the slow-time dimension of the two-dimensional representation based on the portion of the collection of range values of the two-dimensional representation.
8. The method of claim 1 , wherein determining a range and a range rate associated with the object in the field of view based on the representation of the radar receive signals in the frequency domain comprises neglecting second order terms.
9. The method of claim 1 , further comprising:
determining, based on a user input, one or more of the starting frequency of the initial chirp, the slope of the initial chirp, or the pulse repetition period of the initial chirp.
10. The method of claim 1 , further comprising:
maintaining, in a memory in communication with the radar system, one or more of the starting frequency of the initial chirp; the slope of the initial chirp; or the pulse repetition period of the initial chirp.
11. The method of claim 1 , wherein transmitting radar transmit signals representing the parameter defined stepped frequency waveform comprises:
obtaining, by a multiple-input multiple-output integrated circuit of the radar system and from a memory in communication with the radar system, the starting frequency of the initial chirp, the slope of the initial chirp, or the pulse repetition period of the initial chirp.
12. A system comprising:
a radar system having at least one processor configured to:
transmit, from the radar system, radar transmit signals representing a parameter defined stepped frequency waveform for a frame having at least two chirps including an initial chirp of the frame and a current chirp of the frame, the transmit of the radar transmit signals representing the parameter defined stepped frequency waveform including,
determining a pulse frequency for the current chirp relative to a pulse frequency of the initial chirp that cancels a coupling term in a frequency domain representation of radar receive signals received in response to the transmitting of the radar transmit signals by based on: i) a starting frequency of the initial chirp; ii) a slope of the initial chirp; iii) an index of the current chirp; and iv) a pulse repetition period of the initial chirp, and
outputting the current chirp of the parameter defined stepped frequency waveform having the pulse frequency that cancels the coupling term in the frequency domain representation of the radar receive signals;
receive, at the radar system, the radar receive signals representing the parameter defined stepped frequency waveform reflected off of an object in a field of view of the radar system;
perform a transformation of the radar receive signals to determine a representation of the radar receive signals in the frequency domain with the representation of the radar receive signals in the frequency domain having the coupling term cancelled therefrom;
determine a range and a range rate associated with the object in the field of view based on the representation of the radar receive signals in the frequency domain; and
output, to a radar tracker, the range and range rate associated with the object in the field of view to enable radar tracking of the object in the field of view.
13. The system of claim 12 , wherein the parameter defined stepped frequency waveform for the frame further comprises a delay time of the current chirp from a beginning of the frame based on:
the starting frequency of the initial chirp;
the index of the current chirp; and
the pulse repetition period of the initial chirp.
14. The system of claim 13 , wherein the processor is configured to perform a transformation of the radar receive signals to determine the representation of the radar receive signals in the frequency domain by:
performing a two-dimensional Fourier transform of the radar receive signals to generate a two-dimensional representation of the radar receive signals in the frequency domain, the two-dimensional representation including a fast-time dimension and a slow-time dimension.
15. The system of claim 14 , wherein the processor is configured to determine the range and the range rate associated with the object in the field of view based on the representation of the radar receive signals in the frequency domain by:
determining a peak of the two-dimensional representation of the radar receive signals; and
determining the range and the range rate corresponding to the peak of the two-dimensional representation of the radar receive signals.
16. The system of claim 15 , wherein the processor is configured to determine the range and the range rate corresponding to the peak of the two-dimensional representation of the radar receive signals by:
determining a fast-time frequency and a slow-time frequency associated with the peak of the two-dimensional representation of the radar receive signals; and
determining the range and the range rate corresponding to the fast-time frequency and the slow-time frequency associated with the peak of the two-dimensional representation.
17. The system of claim 14 , wherein the processor is configured to perform the transformation of the radar receive signals to determine the representation of the radar receive signals in the frequency domain by:
compensating for a phase contribution of the radar receive signals in the slow-time dimension based on range values of the two-dimensional representation of the radar receive signals.
18. The system of claim 17 , wherein:
the two-dimensional representation of the radar receive signals further comprises a collection of range values; and
the processor is configured to compensate for the phase contribution of the radar receive signals in the slow-time dimension based on the range values of the two-dimensional representation of the radar receive signals by compensating, for a portion of the collection of range values, the slow-time dimension of the two-dimensional representation based on the portion of the collection of range values of the two-dimensional representation.
19. The system of claim 12 , wherein the processor is further configured to:
maintain, in a memory of the radar system, one or more of the starting frequency of the initial chirp; the slope of the initial chirp; or the pulse repetition period of the initial chirp.
20. The system of claim 12 , further comprising a multi-input multiple-output integrated circuit configured to:
obtain, from a memory of the radar system, one or more of the starting frequency of the initial chirp, the slope of the initial chirp, or the pulse repetition period of the initial chirp; and
generate the parameter defined stepped frequency waveform based on the one or more of the starting frequency of the initial chirp, the slope of the initial chirp, or the pulse repetition period of the initial chirp obtained from the memory.
21. The method of claim 1 , wherein the determining determines the pulse frequency for the current chirp relative to the pulse frequency of the initial chirp based on i) the starting frequency of the initial chirp; ii) the slope of the initial chirp; iii) the index of the current chirp; and iv) the pulse repetition period of the initial chirp such that the pulse repetition period decreases as the index of the current chirp increases.
22. The system of claim 12 , wherein the at least one processor is configured to determine the pulse frequency for the current chirp relative to the pulse frequency of the initial chirp based on i) the starting frequency of the initial chirp; ii) the slope of the initial chirp; iii) the index of the current chirp; and iv) the pulse repetition period of the initial chirp such that the pulse repetition period decreases as the index of the current chirp increases.