Reconfigurable chirp fourier transform based continuous convolution processor

• US 8,494,472 B1
• Filed: 03/27/2012
• Issued: 07/23/2013
• Est. Priority Date: 03/28/2011
• Status: Active Grant

• Current Assignee: Ami Research & Development, LLC
• Original Assignee: Ami Research & Development, LLC
• Inventors: Apostolos, John T., Feng, Judy, Mouyos, William
• Primary Examiner(s): Wendell, Andrew
• Application Number:
  US13/431,477
• Time in Patent Office: 483 Days
• Field of Search: 455/425, 455/63.1, 455/550.1, 455/222, 455/278.1, 455/283, 455/286, 455/296, 455/299, 455/306, 455/307, 455/339, 333/165, 333/166, 333/167, 333/186, 333/202
• US Class Current: 455/296
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 2001/6912 using chirp

Abstract

Reconfigurable Chirp Fourier Transform (CFT) based continuous convolution apparatus(es) and method(s) that are effectively used, for example, in interference cancellation applications.

Claims

1. A method for filtering an input signal carried out in a device that includes a dispersive delay line comprising:

feeding the input signal to a forward Chirp Fourier Transform (CFT), where the forward CFT further comprises;

generating a forward periodic chirp signal;

mixing the input signal with the forward periodic chirp signal, to produce a mixed signal;

feeding the mixed signal to said forward dispersive delay line (DDL), to produce a DDL output signal;

modulating the DDL output signal with a filter function H(t), to produce a filter function output signal;

feeding the filter function H(t) output signal to an inverse Chirp Fourier Transform (CFT) to produce an output signal; and

the method for filtering resulting in a continuous convolution process by a subsequent mixing step of, within the inverse CFT, either;

(a) subsequent mixing by two or more overlapping inverse periodic chirp signals;

or

(b) subsequent mixing by a wide band inverse periodic chirp signal of at least twice a duration of the forward periodic chirp signal used in the forward CFT process; and

, further

bandpass filtering the output signal from the inverse CFT, to reject cross products introduced by one of the subsequent mixing steps (a) or (b).

2. The method of claim 1 wherein the filtering is used to mitigate interference.

3. The method of claim 2 additionally comprising:

adaptively estimating the interference to provide an interference estimate; and

determining the filtering function from the interference estimate.

4. The method of claim 3 wherein adaptively estimating further uses a least mean square (LMS) fit to create spatial nulls corresponding to the interference.

5. The method of claim 2 additionally comprising:

sampling an interfering signal;

in response thereto, adjusting weights of the filtering function.

6. The method of claim 2 wherein the interference cancellation is further for isolating a victim receiver.

7. The method of claim 2 additionally wherein:

the input signal is received as a pair of first and second polarized signals; and

the first polarized signal is fed to a first forward CFT; and

the second polarized signal is fed to a second forward CFT.

8. The method of claim 1 wherein

the forward periodic chirp signal has a bandwidth Δ

and duration T; and

the forward DDL has a bandwidth 3Δ and

a duration 3T.

9. The method of claim 8 further wherein

the inverse CFT comprises an inverse dispersive delay line (DDL) having a bandwidth 3Δ

and a duration 3T.

10. The method of claim 1 wherein

adjacent ones of the inverse periodic chirps are overlapped in time by ½

.

11. A method for interference cancellation in a device that

comprises an antenna that provides a right-hand (RH) polarized and left hand (LH) polarized radio frequency input signal, the method comprising:

forward converting the RH polarized signal to a frequency domain representation of the RH polarized signal;

forward converting the LH polarized signal to a frequency domain representation of the LH polarized signal;

detecting interference using a least mean square (LMS) estimate to provide an interference estimate;

determining a filtering function form the interference estimate;

applying a filtering function to the RH and LH frequency domain representation signals to provide a filtered signal; and

inverse converting the filtered signal to produce a radio frequency output signal.

12. The method of claim 11 wherein the steps of forward converting and inverse converting comprise chirp Fourier transforming.