Method, Apparatus and System for Receiving Waveform-Diverse Signals

• US 20200132836A1
• Filed: 10/30/2018
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: Government Of The United Stated As Represented By Secretary Of The Air Force, United States Secretary of the Air Force
• Original Assignee: US Department of The Air Force (U.S. Department Of Defense)
• Inventors: Sahin, Cenk, Metcalf, Justin G., Himed, Braham
• Granted Patent: US 10,725,175 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: G01S 7/006 using shared front-end circuitry, e.g. antennas G01S13/765, G01S13/825 take precedence
• CPC Class Codes: G01S 7/282 Transmitters
• CPC Class Codes: G01S 7/292 Extracting wanted echo-signals
• CPC Class Codes: G01S 7/52025 for pulse systems G01S7/52034 takes precedence

Abstract

A receiver method and apparatus provides a more efficient computation and application of optimal filters. Range and Doppler processing in the receiver are decoupled and, as a result, computational complexity required for both filter computation and filtering stages are significantly reduced. In one embodiment, a response to an emitted signal is demodulated and sampled to provide baseband samples. The response includes a component due to interaction of the emitted signal with a target, The baseband samples are filtered in a bank of N parallel range filters to provide N filter outputs for each of the baseband samples. For one or more Doppler phase shifts ϕ, a discrete Fourier transform of the N filter outputs is computed to produce Doppler components that may be analyzed to determine at least one of a presence, range and speed of the target.

Claims

1. A method for processing a response to an emitted signal, where the emitted signal comprises a sequence of N transmitted pulses, the method comprising:

demodulating and sampling a response to the emitted signal to provide a plurality of baseband samples, where the response includes a component due to interaction of the emitted signal with a target;

for a plurality of times t,

for each filter of a bank of N parallel filters, filtering the plurality of baseband samples to provide N filter outputs;

for one or more Doppler phase shifts ϕ

, computing a discrete Fourier transform of the N filter outputs to produce one or more Doppler components; and

analyzing the one or more Doppler components to determine at least one of a presence, range and speed of the target.

2. The method of claim 1, where analyzing the one or more Doppler components comprises:

identifying a time t₀ and Doppler phase shift ϕ

₀ for which the transformed output has the largest amplitude; and

determining the at least one of the presence, range and speed of the target from the identified time t₀ and the identified Doppler shift ϕ

₀.

3. The method of claim 1, where coefficients of the N filters are based, at least in part, on the N transmitted pulses and an inverse covariance matrix of interference in the plurality of baseband samples and where coefficients of the N filters are independent of the one or more Doppler shifts.

4. The method of claim 3 where the N parallel filters are characterized by filter coefficients that based, at least in part, on an inverse of a covariance matrix of interference in the plurality of baseband samples, the method further comprising:

determining the covariance matrix of interference in the plurality of baseband samples;

ordering elements of the covariance matrix to form a block-Toeplitz matrix; and

determining the inverse of the covariance matrix of interference in the plurality of baseband samples from the block-Toeplitz matrix.

5. The method of claim 4, further comprising:

partitioning the inverse covariance matrix of interference in the plurality of baseband samples into N partitions; and

determining filter coefficients of a filter of the filter bank from a partition of the inverse covariance matrix of interference and a corresponding transmitted pulse of the N transmitted pulses.

6. The method of claim 4, where the interference in the plurality of baseband samples is, at least in part, due to clutter, and where determining the covariance matrix of interference in the plurality of baseband samples is dependent upon the emitted signal and a covariance matrix of clutter coefficients.

7. The method of claim 6, where the interference is, at least in part, due to noise, and where determining the covariance matrix of interference in the plurality of baseband samples is dependent upon a power level of the noise.

8. A method of comprising:

emitting a signal comprising a sequence of N transmitted pulses;

demodulating and sampling a response to the emitted signal to provide a plurality of baseband samples, where the response includes a component due to interaction of the emitted signal with a target;

for a plurality of times t,

for each filter of a bank of N parallel filters, filtering the plurality of baseband samples to provide N filter outputs;

for one or more Doppler phase shifts ϕ

, computing a discrete Fourier transform of the N filter outputs;

identifying a time t₀ and Doppler phase shift ϕ

₀ for which the transformed output has the largest amplitude; and

determining at least one of a presence, range and speed of the target from the identified time t₀ and the identified Doppler shift ϕ

₀.

9. The method of claim 8, further comprising:

encoding a sequence of symbols to provide a waveform; and

modulating the waveform to provide a pulse of the N transmitted pulses.

10. The method of claim 9, where the N parallel filters are characterized by filter coefficients, the method further comprising:

determining the filter coefficients dependent upon the sequence of symbols.

11. The method of claim 10, where the filter coefficients are determined, at least in part, based on an inverse of a covariance matrix of interference in the plurality of baseband samples, the method further comprising:

determining the covariance matrix of interference in the plurality of baseband samples;

ordering elements of the covariance matrix to form a block-Toeplitz matrix;

determining the inverse of the covariance matrix of interference in the plurality of baseband samples from the block-Toeplitz matrix;

partitioning the inverse covariance matrix of interference in the plurality of baseband samples into N partitions; and

determining filter coefficients of a filter of the filter bank from a partition of the inverse covariance matrix of interference and a corresponding transmitted pulse of the N transmitted pulses.

12. An apparatus comprising:

a demodulation unit configured to;

receive a response to an emitted signal, where the response comprises N response pulses each corresponding to a pulse of a sequence of N transmitted pulses, and where the response includes a component due to interaction of the transmitted pulses with a target; and

demodulate and sample the received response to provide a plurality of baseband samples;

a filter bank comprising N filters, each configured to receive the plurality of baseband samples and produce N filter outputs therefrom;

a transform unit configured to compute a discrete Fourier transform of the N filter outputs to produce one or more Doppler components; and

an analysis unit configured to monitor the one or more Doppler components and determine at least one of a presence, range and speed of the target therefrom.

13. The apparatus of claim 12, where the N filters of the filter bank are configured to maximize a signal-to-interference-and-noise ratio (SINR) in the Doppler components.

14. The apparatus of claim 12, further comprising a pre-processor, configured to determine coefficients of the N filters of the filter bank based at least in part on statistical properties of the interference and on the sequence of N transmitted pulses.

15. The apparatus of claim 12, where the emitted signal and response to the emitted signal comprise radar signals.

16. The apparatus of claim 12, further comprising a transmitter configured to:

produce a waveform from a sequence of codes;

modulate the waveform to provide the sequence of N transmitted pulses; and

emit the sequence of N transmitted pulses.

17. The apparatus of claim 16, where the sequence of codes comprises a sequence of communication symbols.

18. The apparatus of claim 16, where the sequence of codes comprises a sequence of radar signal shaping codes.

19. The apparatus of claim 16, where the transmitter comprises a radar transmitter.