Stepped pulse digitally modulated radar

1 . A method performed by a radar system, the method comprising:

transmitting a radar signal toward a target, the radar signal comprising a first sequence of first pulses transmitted via a first transmit antenna within a first frequency band and a second sequence of second pulses transmitted via a second transmit antenna within a second frequency band;

receiving a radar return from the target, the radar return comprising:

the first sequence of first pulses within the first frequency band, wherein the first pulses in the first sequence are encoded according to a first Barker code; and

the second sequence of second pulses within the second frequency band, wherein the second pulses in the second sequence are encoded according to a second Barker code, wherein the second pulses in the second sequence are received at different times as compared to the first pulses in the first sequence, and wherein the second frequency band is different from the first frequency band;

concatenating a frequency domain representation of the first sequence of first pulses and a frequency domain representation of the second sequence of second pulses to generate a concatenated pulse sequence; computing an estimated range to the target based upon the first sequence of first pulses and the second sequence of second pulses, wherein the estimated range has a resolution that is based upon bandwidth of a third frequency band that includes the first frequency band and the second frequency band, wherein computing the estimated range comprises computing an inverse fast Fourier transform (IFFT) over the concatenated pulse sequence, wherein computing the estimated range is based upon the IFFT; and

navigating an autonomous vehicle based in part on the estimated range,

wherein the autonomous vehicle is a first autonomous vehicle operating within a threshold distance of a second autonomous vehicle, wherein the first autonomous vehicle transmits the first sequence of first pulses and the second sequence of second pulses in accordance with a first order, and wherein the second autonomous vehicle transmits the first sequence of first pulses and the second sequence of second pulses in accordance with a second order different from the first order, wherein the first autonomous vehicle and the second autonomous vehicle transmit the pulse sequences using a same set of center frequencies in the first order and the second order respectively.

2 . The method of claim 1 , wherein the resolution of the estimated range is less than or equal to 7.5 centimeters, and wherein bandwidths of the first frequency band and the second frequency band are less than 2 GHZ.

3 . A radar system comprising:

a first transmit antenna that transmits, toward a target, a first plurality of first pulses within a first frequency band, wherein the first pulses in the first sequence are encoded according to a first Barker code;

a second transmit antenna that transmits, toward the target, a second plurality of second pulses within a second frequency band, wherein the second pulses in the second sequence are encoded according to a second Barker code, wherein the first transmit antenna and the second transmit antenna transmit the first pulses and second pulses at different times, and wherein the first frequency band and the second frequency band are different;

an analog-to-digital converter (ADC) that receives an analog signal that is indicative of a radar return received from the target, the radar return based upon a radar signal reflecting from the target, the ADC configured to digitally sample the analog signal to generate radar data that is indicative of the radar return; and

a hardware logic component that is configured to perform acts comprising:

computing an estimated range to the target based upon the radar data, wherein the estimated range has a resolution that is based upon bandwidth of a third frequency band that includes the first frequency band the second frequency band,

wherein an autonomous vehicle is navigated based in part on the estimated range, and wherein the radar data includes a first portion that is representative of a reflection of the first pulses from the target and a second portion that is representative of a reflection of the second pulses from the target, the acts further comprising:

concatenating a frequency domain representation of the first portion and a frequency domain representation of the second portion to generate a concatenated pulse sequence, and wherein computing the estimated range comprises computing an inverse fast Fourier transform (IFFT) over the concatenated pulse sequence, wherein computing the estimated range is based upon the IFFT,

wherein the autonomous vehicle is a first autonomous vehicle operating within a threshold distance of a second autonomous vehicle, wherein the first autonomous vehicle transmits the first sequence of first pulses and the second sequence of second pulses in accordance with a first order, and wherein the second autonomous vehicle transmits the first sequence of first pulses and the second sequence of second pulses in accordance with a second order different from the first order, wherein the first autonomous vehicle and the second autonomous vehicle transmit the pulse sequences using a same set of center frequencies in the first order and the second order respectively.

4 . The radar system of claim 3 , wherein the resolution is less than or equal to 15 centimeters, and wherein a sampling rate of the ADC is less than or equal to 500 megasamples per second (MS/s).

5 . The radar system of claim 4 , wherein the first frequency band and the second frequency band have bandwidths less than or equal to 250 MHz.

6 . The radar system of claim 3 , wherein the resolution is less than or equal to 7.5 centimeters, and wherein a sampling rate of the ADC is less than or equal to 1 gigasamples per second (GS/s).

7 . The radar system of claim 6 , wherein the first frequency band and the second frequency band have bandwidths less than or equal to 500 MHz.

8 . The radar system of claim 3 , wherein the radar signal further comprises a third sequence of third pulses within a fourth frequency band, wherein the third pulses in the third sequence are encoded according to a third Barker code, wherein the third frequency band further includes the fourth frequency band.

9 . The radar system of claim 8 , wherein the first pulses, the second pulses, and the third pulses are transmitted in order of increasing frequency.

10 . The radar system of claim 8 , wherein the first pulses, the second pulses, and the third pulses are transmitted in order of decreasing frequency.

11 . The radar system of claim 8 , wherein the first pulses, the second pulses, and the third pulses are transmitted in random order.

12 . The radar system of claim 3 , wherein the radar data includes a first portion that is representative of a reflection of the first pulses from the target and a second portion that is representative of a reflection of the second pulses from the target, the acts further comprising:

prior to computing the estimated range, applying a first matched filter to the first portion of the radar data, the first matched filter based upon the first pulses; and

prior to computing the estimated range, applying a second matched filter to the second portion of the radar data, the second matched filter based upon the second pulses.

13 . The radar system of claim 3 , wherein the radar system is configured for phase-modulated continuous wave (PMCW) operation.

14 . A radar system comprising:

a first transmit antenna; a second transmit antenna;

a receive antenna; and

a hardware logic component that is configured to perform acts comprising:

causing the first transmit antenna to transmit, toward a target, a first sequence of first pulses within a first frequency band, wherein the first pulses in the first sequence are encoded according to a first Barker code;

causing the second transmit antenna to transmit, toward the target, a second sequence of second pulses within a second frequency band, wherein the second pulses in the second sequence are encoded according to a second Barker code, wherein the first transmit antenna and the second transmit antenna transmit the first pulses and second pulses at different times, and wherein the first frequency band and the second frequency band are different;

responsive to receiving a return of the radar signal from the target by way of the receive antenna, computing an estimated range to the target based upon the first pulses and the second pulses, wherein the estimated range has a resolution that is based upon bandwidth of a third frequency band that includes the first frequency band and the second frequency band, wherein a frequency domain representation of the first pulses and a frequency domain representation of the second pulses are concatenated to generate a concatenated pulse sequence, wherein computing the estimated range comprises computing an inverse fast Fourier transform (IFFT) over the concatenated pulse sequence, wherein computing the estimated range is based upon the IFFT; and

navigating an autonomous vehicle based in part on the estimated range,

wherein the autonomous vehicle is a first autonomous vehicle operating within a threshold distance of a second autonomous vehicle, wherein the first autonomous vehicle transmits the first sequence of first pulses and the second sequence of second pulses in accordance with a first order, and wherein the second autonomous vehicle transmits the first sequence of first pulses and the second sequence of second pulses in accordance with a second order different from the first order, wherein the first autonomous vehicle and the second autonomous vehicle transmit the pulse sequences using a same set of center frequencies in the first order and the second order respectively.

15 . The radar system of claim 14 , wherein causing the first transmit antenna and the second antenna to transmit the first sequence of first pulses and the second sequence of second pulses, respectively, comprises:

controlling a digital-to-analog converter (DAC) to output the first pulses and the second pulses; and

shifting a center frequency of the second pulses such that the second pulses have a different center frequency than the first pulses.

16 . The radar system of claim 15 , wherein the DAC has a sampling rate that is less than the bandwidth of the third frequency band.

17 . The radar system of claim 16 wherein the DAC has a sampling rate of less than or equal to 500 megasamples per second (MS/s).

18 . The radar system of claim 14 , wherein the resolution of the estimated range is less than or equal to 7.5 centimeters, and wherein bandwidths of the first frequency band and the second frequency band are less than or equal to 500 MHz.