INTERFERENCE CANCELLATION SYSTEM AND METHOD USING IMPULSE RESPONSE

• US 20080089451A1
• Filed: 10/17/2006
• Published: 04/17/2008
• Est. Priority Date: 10/17/2006
• Status: Active Grant

• Current Assignee: Edgewater Computer Systems Inc.
• Original Assignee: Edgewater Computer Systems Inc.
• Inventors: Price, George, Esmailian, Tooraj, Taylor, Doug, Fanson, John
• Granted Patent: US 7,907,690 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04L 12/40006 Architecture of a communication node current supply arrangements H04L12/10; intermediate storage or scheduling H04L49/90
• CPC Class Codes: H04L 2012/4028 the transportation system being an aircraft

Abstract

An interference cancellation (IC) system and method for use within a 1553 communication system comprising a data bus carrying primary signals having a 1553 component and a non-1553 component are provided. The IC system has an input port, a 1553 data extraction block and an interference cancellation circuit. The interference cancellation circuit has an interference measurement and a cancellation block. The interference measurement block receives 1553 decoded data from the 1553 data extraction block and a sampled primary signal via the input port, and, within an impulse response block, produces an interference signal based on a 1553 impulse response system model. The cancellation block subtracts the interference signal from the sampled primary signal and produces an output signal with the 1553 component substantially cancelled. Furthermore, an IC system using adaptive filtering techniques within the impulse response block is provided. According to an embodiment of the invention, the Least Mean Squares (LMS) algorithm is used as an adaptive filter technique. An Impulse Response model based on Basis Functions, that can be used within an IC system or independently, is also provided.

Claims

1. Within a 1553 communication system comprising a data bus carrying primary signals having a 1553 component and a non-1553 component, an interference cancellation system comprising:

an input port for receiving a sampled primary signal from the data bus, via an analog-front end block comprising sampling means;

a 1553 data extraction block connected to said input port, for extracting 1553 data from said sampled primary signal and for outputting 1553 decoded data; and

an interference cancellation circuit comprising;

an interference measurement block for receiving said 1553 decoded data and said sampled primary signal, said interference measurement block comprising an impulse response block for producing an interference signal based on a 1553 impulse response system model; and

a cancellation block for subtracting the interference signal from the sampled primary signal and for producing an output signal with the 1553 component substantially cancelled.

2. The interference cancellation system of claim 1, wherein said impulse response block comprises an FIR filter for producing said interference signal based on determined impulse response coefficients.

3. The interference cancellation system of claim 1, wherein said impulse response block comprises an IIR filter for producing said interference signal.

4. The interference cancellation system of claim 1, wherein said impulse response block comprises an adaptive filter for determining impulse response coefficients and for producing said interference signal.

5. The interference cancellation system of claim 4, wherein said adaptive filter uses a Least Mean Square (LMS) algorithm.

6. The interference cancellation system of claim 5, wherein said Least Mean Square (LMS) algorithm uses a step size parameter that is a power of 2.

7. The interference cancellation system of claim 1, wherein said interference measurement block further comprises a generate reference block for producing a reference signal based on said 1553 decoded data and based on predetermined impulse sequences and wherein said impulse response block receives said reference signal.

8. The interference cancellation system of claim 7, wherein said interference measurement block further comprises a resampler for producing a resampled reference signal.

9. The interference cancellation system of claim 1, wherein said analog-front-end comprises first sampling means for producing a first sampled primary signal sent to said 1553 data extraction block and second sampling means for producing a second sampled primary signal sent to said interference cancellation circuit.

10. The interference cancellation system of claim 9, wherein said interference cancellation circuit further comprises a first resampler for resampling said second sampled primary signal in producing a resampled second sampled primary signal and a second resampler for resampling said output signal in producing a resampled output signal.

11. The interference cancellation system of claim 9, wherein said interference cancellation circuit further comprises a first resampler for resampling said second sampled primary signal in producing a resampled second sampled primary signal and a second resampler for resampling said interference signal in producing a resampled interference signal.

12. The interference cancellation system of claim 1, wherein said interference measurement block further comprises an accumulate basis functions block for accumulating basis functions and wherein said impulse response block comprises an extract IR coefficients block for calculating impulse response coefficients w based on said accumulated basis functions.

13. The interference cancellation system of claim 12, wherein said extract IR coefficients block comprises means for calculating impulse response coefficients w based on a matrix equation ψ

w=φ

, wherein ψ

is an invertible matrix constructed based on predefined 1553 symbol sequences that have associated basis functions, and φ

is a vector of said associated basis functions.

14. The interference cancellation system of claim 13, wherein said matrix equation represents and overdetermined system.

15. The interference cancellation system of claim 14, wherein said matrix ψ

is constructed such that it has a pseudoinverse that is a constant multiplied by the transpose of matrix ψ

.

16. The interference cancellation system of claim 12, wherein said extract IR coefficients block comprises means for calculating impulse response coefficients w based on a circular deconvolution.

17. The interference cancellation system of claim 12, wherein the autocorrelation of said input sequence ψ

(n) is a unit impulse sequence.

18. The interference cancellation system of claim 1 used for substantially linear 1553 systems.

19. An interference cancellation method for canceling interference of 1553 signals within a non-1553 data communications system overlayed on a 1553 data communication system, the method comprising the steps of:

acquiring from a data bus a sampled primary signal, the sampled primary signal comprising non-1553 encoded data and 1553 encoded data;

decoding the 1553 encoded data within the sampled primary signal to produce a decoded 1553 data;

producing a variant of an interfering signal based on the decoded 1553 data and based on the sampled primary signal using an impulse response modeling technique;

subtracting the variant of said interfering signal from the sampled primary signal and producing an output signal with a substantially cancelled 1553 component.

20. Within a 1553 communication system comprising a data bus carrying primary signals having a 1553 component and a non-1553 component, the interference cancellation system comprising:

means for separating from said primary signals on said bus a first primary component S1 and a second primary component S3, said S1 including mostly said 1553 component within a first frequency band, and said S3 including mostly said 1553 component and a non-1553 component within a second frequency band;

a 1553 decoder for extracting from said first primary component S1 a 1553 decoded signal; and

an interference canceller for synthesizing a variant of said 1553 component within said second frequency band based on said 1553 decoded signals and said second primary component S3 and based on an impulse response model, and for subtracting said variant of said 1553 component within said second frequency band from said second primary component S3 in producing an output signal including mostly a non-1553 component.

21. An impulse response system comprising an accumulate basis functions block for accumulating basis functions and an impulse response block, said impulse response block having an extract IR coefficients block for calculating impulse response coefficients w based on said accumulated basis functions.

22. A method of determining the impulse response of a system, the method comprising the steps of:

accumulating a plurality of basis functions describing output states of the system; and

solving for the impulse response coefficients of the system based on said accumulated basis functions.