Phase coded linear frequency modulation for radar

• US 9,841,498 B1
• Filed: 11/20/2014
• Issued: 12/12/2017
• Est. Priority Date: 11/20/2014
• Status: Active Grant

• Current Assignee: Waymo LLC (Alphabet Inc.)
• Original Assignee: Waymo LLC (Alphabet Inc.)
• Inventors: Campbell, Tim, Smith, Russell Leigh
• Primary Examiner(s): Adams, Tashiana
• Assistant Examiner(s): Seraydaryan, Helena
• Application Number:
  US14/548,807
• Time in Patent Office: 1,118 Days
• Field of Search: 342 59
• CPC Class Codes: G01S 13/02 Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
• CPC Class Codes: G01S 13/343 using sawtooth modulation
• CPC Class Codes: G01S 13/426 Scanning radar, e.g. 3D radar G01S13/66 takes precedence
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/93272 in the back of the vehicles
• CPC Class Codes: G01S 2013/93274 on the side of the vehicles
• CPC Class Codes: G01S 2013/93277 in the lights
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• CPC Class Codes: G01S 7/0233 Avoidance by phase multiplex
• CPC Class Codes: G01S 7/0234 Avoidance by code multiplex
• CPC Class Codes: G01S 7/41 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

Disclosed herein are embodiments that relate to phase coded linear frequency modulation for a radar system. Embodiments include transmitting at least two signal pulses. The transmitting includes transmitting a first pulse with a first phase modulation and a first chip rate, and transmitting a second pulse with a second phase modulation and a second chip rate. The second chip rate may be different than the first chip rate. Embodiments also include receiving a signal that includes at least two reflection signals associated with reflection of the at least two transmitted signal pulses. Embodiments further include processing the received signal to determine target information. The processing includes filtering the received signal to time-align the at least two reflection signals. The filtering includes applying a frequency-dependent time delay to one or more of the at least two reflection signals. Additionally, embodiments include removing phase code modulations from the time-aligned reflection signals.

Claims

1. A method of signaling with a radar system comprising:

randomly selecting a chip rate offset, wherein the chip rate offset is 100 kilohertz or less;

transmitting, by an antenna of a transmitter of a radar unit, at least two signal pulses, wherein each signal pulse comprises a linear frequency modulation, wherein the transmitting comprises;

transmitting a first pulse, wherein the first pulse comprises an encoded signal encoded by a code synthesis module, wherein the code synthesis module encodes the signal with a first phase modulation and a first chip rate, and

transmitting a second pulse, wherein the second pulse comprises a second encoded signal encoded by the code synthesis module, wherein the code synthesis module encodes the signal with a second phase modulation and a second chip rate, wherein the second chip rate is offset from the first chip rate by the randomly selected chip rate offset;

receiving, by the radar unit, a signal that includes at least two reflection signals associated with reflection of the at least two transmitted signal pulses; and

processing the received signal to determine target information, wherein the processing comprises;

filtering the received signal to time-align the at least two reflection signals, wherein the filtering includes applying a frequency-dependent time delay to one or more of the at least two reflection signals, and

removing phase modulations from the time-aligned reflection signals.

2. The method according to claim 1, wherein the filtering is performed with a finite impulse response filter.

3. The method according to claim 1, wherein removing phase modulations further comprises mixing each time-aligned reflection signal with a respective conjugate signal.

4. The method according to claim 1, wherein the processing further comprises, before the filtering, mixing, using a stretch processor, the received reflection signal with reference signals corresponding to the at least two transmitted pulses.

5. The method according to claim 1, wherein the first phase modulation and the second phase modulation are different phase modulations.

6. The method according to claim 1, wherein the method of signaling is performed by each of a plurality of radar units during overlapping time intervals, wherein each radar unit is located on a respective vehicle.

7. The method according to claim 6, wherein the signaling performed by each of the plurality of radar units is performed with a different phase modulation for each radar unit of the plurality of radar units.

8. A radar system comprising:

a radar unit comprising;

a transmitter configured to transmit at least two signal pulses by an antenna, wherein the transmitter being configured to transmit at least two signal pulses, wherein each signal pulse comprises a linear frequency modulation, wherein the transmitter being further configured to;

transmit a first pulse, wherein the first pulse comprises an encoded signal encoded by a code synthesis module, wherein the code synthesis module encodes the signal with a first phase modulation and a first chip rate, and

transmit a second pulse, wherein the second pulse comprises a second encoded signal encoded by the code synthesis module, wherein the code synthesis module encodes the signal with a second phase modulation and a second chip rate, wherein the second chip rate is offset from the first chip rate by 100 kilohertz or less based on a random selection of an offset;

a receiver configured to receive a signal that includes at least two reflection signals associated with reflection of the at least two transmitted signal pulses;

a processing unit configured to process the received signal to determine target information, wherein the processing unit being configured to process the received signal comprises the processing unit being configured to;

filter the received signal to time-align the at least two reflection signals, wherein the filtering includes applying a frequency-dependent time delay to one or more of the at least two reflection signals, and

remove phase modulations from the time-aligned reflection signals.

9. The radar system according to claim 8, wherein the filtering is performed with a finite impulse response filter.

10. The radar system according to claim 8, wherein removing phase modulations comprises mixing each time-aligned reflection signal with a respective conjugate signal.

11. The radar system according to claim 8, wherein the processing further comprises, before the filtering, mixing, using a stretch processor, the received reflection signal with reference signals corresponding to the at least two transmitted pulses.

12. The radar system according to claim 8, wherein the first phase modulation and the second phase modulation are different phase modulations.

13. The radar system according to claim 8, wherein the method of signaling is performed by each of a plurality of radar units during overlapping time intervals, wherein each radar unit is located on a respective vehicle.

14. The radar system according to claim 13, wherein the signaling performed by each of the plurality of radar units is performed with a different phase modulation for each radar unit of the plurality of radar units.

15. An article of manufacture including a non-transitory computer-readable medium, having stored thereon program instructions that, if executed by a computing device, cause the computing device to perform operations comprising:

randomly selecting a chip rate offset, wherein the chip rate offset is 100 kilohertz or less;

transmitting, by an antenna of a transmitter of a radar unit, at least two signal pulses, wherein each signal pulse comprises a linear frequency modulation, wherein the transmitting comprises;

transmitting a first pulse, wherein the first pulse comprises an encoded signal encoded by a code synthesis module, wherein the code synthesis module encodes the signal with a first phase modulation and a first chip rate, and

transmitting a second pulse, wherein the second pulse comprises a second encoded signal encoded by the code synthesis module, wherein the code synthesis module encodes the signal with a second phase modulation and a second chip rate, wherein the second chip rate is offset from the first chip rate by the randomly selected chip rate offset;

receiving, by the radar unit, a signal that includes at least two reflection signals associated with reflection of the at least two transmitted signal pulses;

processing the received signal to determine target information, wherein the processing comprises;

filtering the received signal to time-align the at least two reflection signals, wherein the filtering includes applying a frequency-dependent time delay to one or more of the at least two reflection signals, and

removing phase modulations from the time-aligned reflection signals.

16. The article of manufacture according to claim 15, wherein the filtering is performed with a finite impulse response filter.

17. The article of manufacture according to claim 15, wherein removing phase modulations comprises mixing each time-aligned reflection signal with a respective conjugate signal.

18. The article of manufacture according to claim 15, wherein the processing further comprises, before the filtering, mixing, using a stretch processor, the received reflection signal with reference signals corresponding to the at least two transmitted pulses.

19. The article of manufacture according to claim 15, wherein the first phase modulation and the second phase modulation are different phase modulations.

20. The article of manufacture according to claim 15, wherein the method of signaling is performed by each of a plurality of radar units during overlapping time intervals, wherein each radar unit is located on a respective vehicle, and wherein the signaling performed by each of the plurality of radar units is performed with a different phase modulation for each radar unit of the plurality of radar units.