Extended doppler FMCW code division MIMO radar

Patent metadata

Field	Value
Publication number	US-11054516-B2
Application number	US-201816223881-A
Country	US
Kind code	B2
Filing date	Dec 18, 2018
Priority date	Dec 18, 2018
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

Embodiments are provided for a radar system including: an N number of transmit antennas; a chirp generator configured to produce linear chirp waveforms; an N number of phase shift keying (PSK) coders, each assigned a respective optimized transmitter code of a set of optimized transmitter codes, each optimized transmitter code of the set comprises a sequence of K code chips, each optimized transmitter code of the set is orthogonal to every other optimized transmitter code of the set, spectral analysis of a cross-correlation between any two optimized transmitter codes results in sidelobes no greater than a predetermined detection threshold, each PSK coder encodes K linear chirp waveforms according to the sequence of K code chips of the respective optimized transmitter code and produces a respective optimized coded chirp sequence, and each of the N transmit antennas outputs the respective optimized coded chirp sequence at the same time.

First claim

What is claimed is:

1. A radar system comprising:
an N number of transmit antennas; and
an N number of phase shift keying (PSK) coders, each of the N PSK coders assigned a respective optimized transmitter code of a set of optimized transmitter codes, wherein
each optimized transmitter code of the set comprises a sequence of K code chips,
each optimized transmitter code of the set is orthogonal to every other optimized transmitter code of the set,
spectral analysis of a cross-correlation between any two optimized transmitter codes results in sidelobes having a value no greater than a predetermined detection threshold,
each PSK coder is configured to encode a K number of ranging waveform blocks according to the sequence of K code chips of the respective optimized transmitter code and produce a respective optimized coded sequence, and
each of the N transmit antennas is configured to output the respective optimized coded sequence at the same time.

2. The radar system of claim 1 , wherein
the respective optimized coded sequence is transmitted once to form a Doppler frame, and
the sequence of K code chips used to code the respective optimized coded sequence is never repeated during the Doppler frame.

3. The radar system of claim 2 , wherein
a pulse repetition interval (PRI) has a duration equal to or greater than a duration of the ranging waveform block,
a K number of PRIs are completed during the Doppler frame,
a Doppler measurement resolution of the radar system is 1/(K*PRI), and
a maximum unambiguous Doppler shift measurable by the radar system is +/−0.5*(1/PRI).

4. The radar system of claim 2 , wherein
the Doppler frame is less than or equal to a dwell time,
the dwell time is a maximum amount of time in which an echo signal is coherently processed by the radar system, and
K is an integer number of Doppler bins that are allowable during the dwell time.

5. The radar system of claim 1 , wherein
the set of optimized transmitter codes comprises a set of binary phase shift keying (BPSK) transmitter codes, and
the predetermined detection threshold is less than or equal to √{square root over (K)}.

6. The radar system of claim 1 , further comprising:
an M number of receive antennas configured to receive reflected optimized coded sequences that were transmitted by one or more of the N transmit antennas and reflected off of a target, wherein
each echo signal's original optimized coded sequence comprises a sequence of K ranging waveform blocks that are encoded according to a sequence of K code chips of a particular optimized transmitter code, each ranging waveform block comprising an L number of unit ranging waveforms;

an M number of fast time matched filters (FTMF), each FTMF comprising a bank of J range gates, each J range gate comprising L filters, each J range gate tuned to a respective range, wherein the J range gates are configured to sort the echo signals into J range bins;
an M number of summer blocks, each summer block configured to sum a set of J*L outputs into J range gate outputs; and
an M number of joint matched filters, each of the M joint matched filters implementing N*K combination filters for each of the J range gate outputs, for a total of N*K*J combination filters, wherein
each of the N*K*J combination filters is configured to simultaneously perform decoding and Doppler filtering of an echo signal.

7. The radar system of claim 6 , wherein
for each of the J range gate outputs:
the N*K combination filters are grouped into N groups, each N group having K combination filters,
each of the N groups is associated with a distinct optimized transmitter code of the set of optimized transmitter codes,
each of the K combination filters in a given group is tuned to a respective Doppler shift, and
each of the K combination filters in the given group is weighted with a complex conjugate of a respective code chip of the distinct optimized transmitter code.

8. The radar system of claim 7 , wherein
for each of the J range gate outputs:
for each of the N groups:
each K combination filter is configured to multiply a respective code chip of a particular optimized transmitter code of a given echo signal by the complex conjugate of a respective code chip of the distinct optimized transmitter code, and
each of the K combination filters is configured to output a correlation signal.

9. The radar system of claim 8 , wherein
for each of the J range gate outputs:
for each of the N groups:
a correlation peak is detected when a sum of the outputs of the K combination filters is greater than the predetermined detection threshold, and
the correlation peak indicates that all code chips of the particular optimized transmitter code of the echo signal matches all code chips of the distinct optimized transmitter code.

10. The radar system of claim 6 , wherein
the N*K*J combination filters are implemented with Fast Fourier transform (FFT) filters.

11. A radar system comprising:
an N number of transmit antennas;
an M number of receive antennas configured to receive reflected optimized coded sequences that were transmitted by one or more of the N transmit antennas and reflected off of a target, wherein
each echo signal's original optimized coded sequence comprises a sequence of K ranging waveform blocks that are encoded according to a sequence of K code chips of a particular optimized transmitter code, each ranging waveform block comprising an L number of unit ranging waveforms;

an M number of fast time matched filters (FTMF), each FTMF comprising a bank of J range gates, each J range gate comprising L filters, each J range gate tuned to a respective range, wherein the J range gates are configured to sort the echo signals into J range bins;
an M number of summer blocks, each summer block configured to sum a set of J*L outputs into J range gate outputs; and
an M number of joint matched filters, each of the M joint matched filters implementing N*K combination filters for each of the J range gate outputs, for a total of N*K*J combination filters, wherein
each of the N*K*J combination filters is configured to simultaneously perform decoding and Doppler filtering of an echo signal.

12. The radar system of claim 11 , wherein
each of the N transmit antennas is assigned a respective optimized transmitter code of a set of optimized transmitter codes,
each optimized transmitter code of the set comprises a sequence of K code chips,
each optimized transmitter code of the set is orthogonal to every other optimized transmitter code of the set, and
spectral analysis of a cross-correlation between any two optimized transmitter codes results in sidelobes having a value no greater than a predetermined detection threshold.

13. The radar system of claim 12 , wherein
for each of the J range gate outputs:
the N*K combination filters are grouped into N groups, each N group having K combination filters,
each of the N groups is associated with a distinct optimized transmitter code of the set of optimized transmitter codes,
each of the K combination filters in a given group is tuned to a respective Doppler shift, and
each of the K combination filters in the given group is weighted with a complex conjugate of a respective code chip of the distinct optimized transmitter code.

14. The radar system of claim 13 , wherein
for each of the J range gate outputs:
for each of the N groups:
each K combination filter is configured to multiply a respective code chip of a particular optimized transmitter code of a given echo signal by the complex conjugate of a respective code chip of the distinct optimized tra

Assignees

• Nxp Usa Inc

Inventors

• Wu Ryan Haoyun
• Li Chunshu
• Roy Arunesh

Classifications

• G01S7/356

  involving particularities of FFT processing · CPC title

• G01S13/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S13/46) · CPC title

• G01S13/584

  adapted for simultaneous range and velocity measurements · CPC title

• G01S13/44

  Monopulse radar, i.e. simultaneous lobing · CPC title

• G01S7/42

  Diversity systems specially adapted for radar · CPC title