Adjusting DFT coefficients to compensate for frequency offset during a sounding sequence used for fractional time determination

Patent metadata

Field	Value
Publication number	US-11638116-B2
Application number	US-202017108908-A
Country	US
Kind code	B2
Filing date	Dec 1, 2020
Priority date	Dec 1, 2020
Publication date	Apr 25, 2023
Grant date	Apr 25, 2023

Abstract

A receiver includes a first discrete Fourier transform (DFT) block to perform a first single tone DFT on a positive tone associated with a sounding sequence. A second DFT block performs a second single tone DFT on a negative tone associated with the sounding sequence. A DFT coefficient generation block generates first DFT coefficients based on a nominal frequency of the positive tone and an estimated frequency offset between a transmitter frequency and a receiver frequency. The DFT coefficient generation block generates second DFT coefficients based on a nominal frequency of the negative tone and the estimated frequency offset. Multipliers in the DFT blocks multiply I and Q values of the sounding sequence with the coefficients. Accumulators in the DFT blocks accumulate multiplier outputs. An arctan function receives averaged accumulated values from the first and second DFT blocks and supplies first and second phase values used to calculate fractional timing.

First claim

What is claimed is:

1. A receiver comprising:
digital filters in a receive path of the receiver to provide imaginary components of a received signal and real components of the received signal;
a first discrete Fourier transform (DFT) block including,
a first complex multiplier coupled to receive the imaginary components of the received signal and the real components of the received signal and to receive first complex DFT coefficients;
a first accumulator to receive real outputs of the first complex multiplier and to supply first accumulated real values;
a second accumulator to receive imaginary outputs of the first complex multiplier and to supply first accumulated imaginary values; and

a DFT coefficient generation function to generate the first complex DFT coefficients based in part on one or more estimated frequency offsets between a transmitter frequency and a receiver frequency and to supply the first complex DFT coefficients to the first complex multiplier.

2. The receiver as recited in claim 1 further comprising:
an arctan function coupled to receive an average of the first accumulated real values and an average of the first accumulated imaginary values and supply a first phase value.

3. The receiver as recited in claim 2 further comprising:
a second DFT block including,
a second complex multiplier coupled to receive the imaginary components of the received signal and the real components of the received signal and second complex DFT coefficients; and
a third accumulator to receive real outputs of the second complex multiplier and to supply second accumulated real values;

a fourth accumulator to receive imaginary outputs of the second complex multiplier and to supply second accumulated imaginary values wherein the DFT coefficient generation function generates the second complex DFT coefficients based in part on the one or more estimated frequency offsets; and
wherein the arctan function is coupled to receive an average of the second accumulated real values and an average of the second accumulated imaginary values and supply a second phase value.

4. The receiver as recited in claim 3 wherein the received signal is a sounding sequence generated with an alternating ones and zeros pattern.

5. The receiver as recited in claim 4 wherein the one or more estimated frequency offsets are generated using, at least in part, a sequence received prior to the sounding sequence.

6. The receiver as recited in claim 4 further wherein the first DFT block performs a first single tone DFT for a positive tone associated with the sounding sequence and the second DFT block performs a second single tone DFT for a negative tone associated with the sounding sequence.

7. The receiver as recited in claim 6 wherein the positive tone is nominally 500 kHz or 1000 kHz and the negative tone is nominally −500 kHz or −1000 kHz.

8. The receiver as recited in claim 6 wherein the first DFT coefficients are generated by adjusting nominal first coefficients for a nominal frequency of the positive tone by Φn, where Φ(n)=e j2πΔfn/(2×OSR×500 kHz) , where Δf is the frequency offset estimate, and OSR is the over sampling ratio.

9. The receiver as recited in claim 8 wherein the second DFT coefficients are generated by adjusting nominal second coefficients for a nominal frequency of the negative tone by Φn, where Φ(n)=e j2πΔfn/(2×OSR×500 kHz) .

10. The receiver as recited in claim 3 further comprising:
fractional timing logic to determine a fractional timing value based on a difference between the first phase value and the second phase value.

11. A method for determining fractional timing comprising:
receiving at a receiving device a sounding sequence of alternating ones and zeros transmitted from a transmitting device;
generating first coefficients used by a first complex multiplier of a first discrete Fourier transform (DFT) block, the first coefficients being based in part on a frequency offset estimate of a frequency offset between a first frequency associated with the transmitting device and a second frequency associated with the receiving device;
supplying a first DFT output from the first DFT block;
generating a second coefficients used by a second complex multiplier of a second DFT block based in part on the frequency offset estimate;
supplying a second DFT output from the second DFT block; and
determining a first phase based on the first DFT output and a second phase based on the second DFT output.

12. The method as recited in claim 11 further comprising:
accumulating a first real part and a first imaginary part supplied by the first complex multiplier to generate an accumulated first real part and an accumulated first imaginary part; and
supplying an average of the accumulated first real part and an average of the accumulated first imaginary part to an arctan function for use in generating the first phase.

13. The method as recited in claim 12 further comprising:
accumulating a second real part and a second imaginary part supplied by the second complex multiplier to generate an accumulated second real part and an accumulated second imaginary part; and
supplying an average of the accumulated second real part and an average of the accumulated second imaginary part to the arctan function for use in generating the second phase.

14. The method as recited in claim 11 further comprising:
determining fractional timing value based on a difference between the first phase and the second phase.

15. The method as recited in claim 11 wherein the first and second DFTs are single tone DFTs.

16. The method as recited in claim 11 further comprising generating the frequency offset estimate based, at least in part, on a sequence received preceding the sounding sequence.

17. The method as recited in claim 11 further comprising:
generating one or more additional frequency offsets estimates during the sounding sequence;
generating additional first coefficients for the first DFT block, based in part on the one or more additional frequency offset estimates; and
generating additional second coefficients for the second DFT block, based in part on the one or more additional frequency offset estimates.

18. The method as recited in claim 11 ,
wherein the first coefficients are based on a first nominal value of a positive frequency adjusted by the frequency offset estimate; and
wherein the second coefficients are based on a second nominal value of a negative frequency adjusted by the frequency offset estimate.

19. An apparatus comprising:
a first discrete Fourier transform (DFT) block to perform a first single tone DFT on a positive tone associated with a sounding sequence;
a second DFT block to perform a second single tone DFT on a negative tone associated with the sounding sequence; and
a DFT coefficient generation block to generate first DFT coefficients that are based on a nominal frequency of the positive tone and one or more frequency offset estimates between a transmitter frequency and a receiver frequency and to supply the first DFT coefficients to the first DFT block and to generate second DFT coefficients that are based on a nominal frequency of the negative tone and the one or more frequency offset estimates and to supply the second DFT coefficients to the second DFT block.

20. The apparatus as recited in claim 19 ,
wherein the first DFT block includes,
a first complex multiplier coupled to receive imaginary components of the sounding sequence and real components of the sounding sequence and to receive th

Assignees

• Silicon Lab Inc

Inventors

• Li Wentao
• Zhou Yan
• Wu Michael A

Classifications

• G01S11/02

  using radio waves (G01S19/00 takes precedence) · CPC title

• G01R23/175

  by delay means, e.g. tapped delay lines · CPC title

• G01S13/765 Primary

  with exchange of information between interrogator and responder · CPC title

• G01S5/0252 Primary

  Radio frequency fingerprinting · CPC title

• H04L43/0852

  Delays · CPC title