Orthogonal Frequency Division Multiplexing (OFDM) Radio as Radar

• US 20110193739A1
• Filed: 06/08/2010
• Published: 08/11/2011
• Est. Priority Date: 02/10/2010
• Status: Active Grant

• Current Assignee: TiaLinx, Inc.
• Original Assignee: TiaLinx, Inc.
• Inventors: Strauch, Paul, Nag, Soumya K., Mohamadi, Farrokh
• Granted Patent: US 8,441,393 B2
• Time in Patent Office: Days
• US Class Current: 342/146
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/288 phase modulated
• CPC Class Codes: G01S 13/888 through wall detection
• CPC Class Codes: G01S 7/006 using shared front-end circuitry, e.g. antennas G01S13/765, G01S13/825 take precedence
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

An orthogonal frequency division multiplexing (OFDM) communication system is adapted for radar ranging and imaging. A radar system includes an orthogonal frequency division multiplexing (OFDM) radio communications transmitter configured to transmit information bits using one or more payload symbols in a transmitted signal; and a receiver configured to: construct the payload symbols from the information bits provided by the transmitter; receive the payload symbols in the transmitted signal reflected from a target; apply a matched filter to the received payload symbols using the constructed payload symbols as a template; and process a magnitude response at an output of the matched filter for estimating location and imaging of the target.

Claims

1. A radar system comprising:

an orthogonal frequency division multiplexing (OFDM) radio communications transmitter configured to transmit information bits using one or more payload symbols in a transmitted signal; and

a receiver configured to;

construct the payload symbols from the information bits provided by the transmitter;

receive the payload symbols in the transmitted signal reflected from a target;

apply a matched filter to the received payload symbols using the constructed payload symbols as a template; and

process a magnitude response at an output of the matched filter for estimating location and imaging of the target.

2. The radar system of claim 1, wherein the radar receiver is further configured to apply a pulse integration at the output of the matched filter.

3. The radar system of claim 1, wherein applying the matched filter to the received payload symbols comprises applying a pulse compression technique to the payload symbols.

4. The radar system of claim 1, wherein:

the information bits are provided at a physical layer service access point (PHY SAP);

the information bits from the PHY SAP comprise at least one of a physical-layer convergence protocol (PLCP) service data unit (PSDU) or a media access control (MAC) protocol data unit (MPDU) provided to a scrambler input; and

the template comprises an OFDM symbol generated from the specific scrambled, encoded, and interleaved bit pattern at an interleaver output or OFDM modulator input of the transmitter, the specific bit pattern corresponding to a specific PSDU or MPDU data at the scrambler input.

5. The radar system of claim 1, wherein the received payload symbols are generated from samples extracted at an output of an analog-to-digital converter (ADC) in a receiver physical-layer system on chip (PHY-SoC).

6. The radar system of claim 5, wherein the samples at the ADC output are extracted at a rate of at least 512 Msps via an interface to a digital signal processor for real-time processing.

7. The radar system of claim 5, wherein a start of the extracted samples from the ADC output corresponds to a start of frame payload symbols of a PSDU so as to provide a synchronization allowing removal of zero padded suffix (ZPS) samples per OFDM payload so that the matched filter applies only on data samples exclusive of the ZPS.

8. The radar system of claim 1, wherein a ranging functionality of the OFDM transmitter and receiver is used to provide a true time of arrival of an initial transmitted signal reflection from a scatterer.

9. The radar system of claim 1, further comprising:

a downconverter applied to the transmitted signal for transmitting pulses in a UWB wave band; and

an upconverter applied to the received signal reflected from the target.

10. The radar system of claim 9, wherein:

the received payload symbols are generated from samples extracted at an output of an analog-to-digital converter (ADC) in the receiver physical-layer system on chip (PHY-SoC); and

the samples at the ADC output are extracted at a rate of at least 2.538 Gsps via an interface to a digital signal processor for real-time processing.

11. The radar system of claim 9, wherein:

a start of the extracted samples from the ADC output corresponds to a start of frame payload symbols of an MPDU so as to provide a synchronization allowing removal of a cyclic prefix (CP) per OFDM payload so that the matched filter applies only on data samples exclusive of the CP.

12. The radar system of claim 9, wherein an antenna coupling between an antenna of the OFDM transmitter and an antenna of the receiver is used to provide a true time of arrival of an initial transmitted signal reflection from a scatterer.

13. A method comprising:

transmitting an orthogonal frequency division multiplexing (OFDM) modulated signal comprising information bits conveyed by one or more payload symbols;

constructing the payload symbols from the information bits provided to a receiver;

receiving the payload symbols in the transmitted signal reflected from a target;

applying matched filtering to the received payload symbols using the constructed payload symbols as a template; and

processing a magnitude response at a matched filter output to produce a range estimate of the target.

14. The method of claim 13, further comprising processing a magnitude response at a matched filter output to produce imaging of the target.

15. The method of claim 13, further comprising apply a pulse integration technique to the output of the matched filter to improve signal-to-noise ratio (SNR).

16. The method of claim 13, further comprising:

providing the information bits at a physical layer service access point (PHY SAP) of an OFDM transmitter;

providing the information bits in at least one of a physical-layer convergence protocol (PLCP) service data unit (PSDU) or a media access control (MAC) protocol data unit (MPDU) to a scrambler input; and

constructing the templates for matched filtering from OFDM symbols generated from the specific scrambled, encoded, and interleaved bit pattern at an interleaver output or OFDM modulator input of the transmitter, wherein the specific bit pattern corresponds to a specific PSDU or MPDU data at the scrambler input.

17. The method of claim 13, further comprising generating the received payload symbols from samples extracted at the output of an analog-to-digital converter (ADC) in a receiver physical-layer system on chip (PHY-SoC).

18. The method of claim 17, wherein a start of the extracted samples from the ADC output corresponds to a start of frame payload symbols of a PSDU so as to provide a synchronization allowing removal of zero padded suffix (ZPS) samples per OFDM payload so that the matched filter applies only on data samples exclusive of the ZPS.

19. The method of claim 17, wherein:

the transmitted signal is downconverted from a millimeter wave band to a UWB wave band;

the received signal reflected from the target is upconverted; and

a start of the extracted samples from the ADC output corresponds to a start of frame payload symbols of an MPDU so as to provide a synchronization allowing removal of a cyclic prefix (CP) per OFDM payload so that the matched filter applies only on data samples exclusive of the CP.

20. An orthogonal frequency division multiplexing (OFDM) radio comprising:

an OFDM radio communications transmitter configured to;

transmit information bits using one or more payload symbols in a transmitted signal; and

provide the information bits from a physical layer service access point (PHY SAP); and

a receiver configured to;

construct the payload symbols from the information bits provided by the transmitter;

receive the payload symbols in the transmitted signal reflected from a target;

apply a matched filter to the received payload symbols using the constructed payload symbols as a template; and

process a magnitude response at the matched filter output for ranging and imaging of the target.