Method for efficient and zero latency filtering in a long impulse response system

• US 8,340,285 B2
• Filed: 11/19/2007
• Issued: 12/25/2012
• Est. Priority Date: 08/25/2000
• Status: Active Grant

• Current Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Asia Pacific Pte Limited (STMicroelectronics NV)
• Inventors: Tian, Wenshun
• Primary Examiner(s): Powers, William S.
• Assistant Examiner(s): WYSZYNSKI, AUBREY H
• Application Number:
  US11/942,654
• Publication Number:
  US 20080155001A1
• Time in Patent Office: 1,863 Days
• Field of Search: 380/37, 708/300
• US Class Current: 380/37
• CPC Class Codes: H03H 17/0213 Frequency domain filters using Fourier transforms
• CPC Class Codes: H03H 17/0219 Compensation of undesirable effects, e.g. quantisation noise, overflow stability problems H03H17/0461
• CPC Class Codes: H03H 17/06 Non-recursive filters

Abstract

A method for long impulse response digital filtering of an input data stream, by use of a digital filtering system. Where the input data stream is divided into zero-input signals and zero-state signals. One of the zero-input signals and a corresponding impulse response of the digital filtering system is converted to the frequency domain to determine a respective zero-input response of the digital filtering system. One of the zero-state signals is convolved with a corresponding impulse response of the digital filtering system to determine a respective zero-state response of the digital filtering system, wherein at least part of the zero-input signal precedes the zero-state signal. The zero-state response of the digital filtering system is added to the zero-input response of the digital filtering system to determine the response of the digital filtering system. Apparatus for effecting this method is also disclosed.

Claims

1. A method for long impulse response digital filtering of an input data stream in a digital filtering system to improve signal accuracy in electronic systems, comprising:

(a) dividing the input data stream into zero-input signals and zero-state signals using a digital filter;

(b) determining a zero-input response of the digital filter by performing with the digital filtering system a first conversion of one of the zero-input signals and a corresponding impulse response of the digital filtering system to the frequency domain and a second conversion of a product of the one of the zero-input signals and the impulse response in the frequency domain to the time domain;

(c) determining a zero-state response of the digital filter by convolving one of the zero-state signals with a corresponding impulse response of the digital filtering system, wherein at least part of the zero-input signal precedes the zero-state signal; and

(d) producing an output of the digital filtering system by adding the zero-state response to the zero-input response to produce an output of the digital filtering system that is a response of the digital filtering system to the input data stream.

2. The method of claim 1, wherein the zero-input signal includes a first plurality of input data samples from the input data stream and the zero-state signal includes a second plurality of input data samples from the input data stream, wherein the zero-input signal at least partially includes input data samples from a prior zero-state signal.

3. The method of claim 1, wherein prior to the converting one of the zero-input signals and a corresponding impulse response of the digital filtering system to the frequency domain, the method includes:

(a) appending a first plurality of zeros to said one of the zero-input data signals to form a first data block of a predetermined size;

(b) appending a second plurality of zeros to the corresponding impulse response of the digital filtering system to form a second data block of a predetermined size, wherein the first and second data blocks are of equal size; and

(c) shifting the contents of the first data block in accordance with a predetermined function to produce a shifted first data block;

wherein the first conversion converts the shifted first data block and the second data block to the frequency domain and the second conversion converts the product of the shifted first data block and the second data block to the time domain to determine the shifted zero-input response of the digital filtering system, and

further including shifting the contents of the shifted zero-input response of the digital filtering system in accordance with a predetermined function to determine the respective zero-input response of the digital filtering system.

4. The method of claim 1, wherein the output of the digital filtering system corresponds to:

5. A method for long impulse response digital filtering of an input data stream by use of a digital filtering system structured to improve signal accuracy in electronic systems, comprising:

(a) dividing the input data stream into zero-input signals and zero-state signals;

(b) receiving one of the zero-input signals and appending a first plurality of zeros to said one of the zero-input signals in order to form a first data block of a predetermined size;

(c) determining an impulse response of the digital filtering system that corresponds to said one of the zero-input signals and appending a second plurality of zeros to the impulse response of the digital filtering system to form a second data block of a predetermined size, wherein the first and second data blocks are of equal size;

(d) shifting the contents of the first data block in accordance with a predetermined function;

(e) determining a shifted zero-input response of the digital filtering system by converting the contents of the first and second data blocks to the frequency domain and then converting a product of the first and second data blocks in the frequency domain to the time domain;

(f) shifting the shifted zero-input response of the digital filtering system in accordance with a predetermined function to determine the zero-response of the digital filtering system;

(g) receiving one of the zero-state signals and convolving said one of the zero-state signals with a corresponding impulse response of the digital filtering system to determine a respective zero-state response of the digital filtering system, wherein said one of the zero-input signals at least partially precedes said one of the zero-state signals; and

(h) adding the zero-state response to the zero-input response to generate an output of the digital filtering system that is a response of the digital filtering system to the input data stream.

6. The method of claim 5, wherein the output of the digital filtering system corresponds to:

7. A method for long impulse response digital filtering of an input data stream that includes first and second data sequences, the method comprising:

(a) receiving one of the first data sequences, that includes a first plurality of input data samples from the input data stream;

(b) receiving one of the second data sequences, that includes a second plurality of input data samples from the input data stream, wherein said one of the first data sequences at least partially precedes said one of the second input data sequences;

(c) determining an impulse response using a digital filter of the digital filtering system;

(d) storing said one of the first data sequences in a first fixed sized data block, wherein remaining space in the first fixed sized data block is occupied by zero data units;

(e) storing the impulse response of the digital filter in a second fixed size data block, wherein remaining space of the second fixed sized data block is occupied by zero data units and wherein the first and second fixed sized data blocks are of equal size;

(f) determining a zero-impulse response of the digital filter by converting the first and second fixed sized data blocks to the frequency domain and then converting their product to the time domain using the digital filter;

(g) determining a zero-state response of the digital filter by convolving said one of the second data sequences with a corresponding impulse response of the digital filtering system; and

(h) adding the second response to the first response in the digital filtering system to produce an output that is a response of the digital filtering system to the input data stream.

8. The method of claim 7, wherein converting from the time domain to the frequency domain is effected by 2N-point transforms and converting from the frequency domain to the time domain is effected by 2N-point inverse transforms.

9. The method of claim 7, wherein the output of the digital filtering system corresponds to:

10. A method for long impulse response digital filtering of an input data stream by use of a digital filtering system, comprising:

(a) dividing the input data stream into first stage zero-input signals and first stage zero-state signals;

(b) performing a first conversion of one of the first stage zero-input signals and a corresponding impulse response of the digital filtering system to the frequency domain;

(c) performing a second conversion of the product of the first stage zero-input signal and the corresponding impulse response in the frequency domain to the time domain to determine a respective first stage zero-input response of the digital filtering system;

(d) dividing one of the first stage zero-state signals into a second stage zero-input signal and a second stage zero-state signal;

(e) converting the second stage zero-input signal and a corresponding impulse response of the digital filtering system to the frequency domain;

(f) determining a second stage zero-input response of the digital filtering system by converting a product of the second stage zero-input signal and the corresponding impulse response in the frequency domain to the time domain;

(g) determining a second stage zero-state impulse response of the digital filtering system by convolving the second stage zero-state signal with a corresponding impulse response of the digital filtering system;

(h) determining a first stage zero-state response of the digital filtering system by adding the second stage zero-state response of the digital filtering system to the second stage zero-input response of the digital filtering system; and

(i) adding the first stage zero-state response of the digital filtering system to the first stage zero-input response of the digital filtering system to produce an output of the digital filtering system that is a response of the digital filtering system to the input data stream.

11. The method of claim 10, wherein further stages are created by dividing zero-state signals into zero-input and zero-state signals.

12. The method of claim 10, wherein the output of the digital filtering system corresponds to:

13. A digital filtering system, comprising:

a long impulse response digital filter for filtering an input data stream, the filter structured to;

(a) divide the input data stream into zero-input signals and zero-state signals;

(b) convert one of the zero-input signals and a corresponding impulse response of the digital filter to the frequency domain and to convert the product of the zero-input signal and the impulse response in the frequency domain to the time domain in order to determine a respective zero-input response of the digital filter;

(c) convolve one of the zero-state signals with a corresponding impulse response of the digital filter to determine a respective zero-state response of the digital filter, wherein at least part of the zero-input signal precedes the zero-state signal; and

(d) add the zero-state response to the zero-input response to produce an output of the digital filter that is a response of the digital filter to the input data stream.

14. The digital filtering system of claim 13, wherein the digital filter is structured to include a first plurality of input data samples from the input data stream in the zero input signal and to include a second plurality of input data samples from the input data stream in the zero-state signal, and to at least partially includes input data samples from a prior zero-state signal in the zero-input signal.

15. The digital filtering system of claim 13, wherein the digital filter is further structured, prior to converting said one of the zero-input signals and the corresponding impulse response of the digital filter to the frequency domain to:

(a) append a first plurality of zeros to said one of the zero-input data signals to form a first data block of a predetermined size;

(b) append a second plurality of zeros to the corresponding impulse response of the digital filter to form a second data block of a predetermined size, wherein the first and second data blocks are of equal size;

(c) shift the contents of the first data block in accordance with a predetermined function to produce a shifted first data block;

(d) convert the shifted first data block and the second data block to the frequency domain and convert the product of the shifted first data block and the second data block back to the time domain to determine the shifted zero-input response of the digital filtering system; and

(e) shift the contents of the shifted zero-input response of the digital filter in accordance with a predetermined function to determine the respective zero-input response of the digital filter.

16. The method of claim 13, wherein the output of the digital filter corresponds to:

17. A long impulse response digital filter for filtering of an input data stream to improve signal accuracy in electronic systems, the digital filter structured to:

(a) divide the input data stream into zero-input signals and zero-state signals;

(b) receive one of the zero-input signals and append a first plurality of zeros to said one of the zero-input signals in order to form a first data block of a predetermined size;

(c) determine an impulse response of the digital filter that corresponds to said one of the zero-input signals and append a second plurality of zeros to the impulse response of the digital filter to form a second data block of a predetermined size, wherein the first and second data blocks are of equal size;

(d) shift the contents of the first data block in accordance with a predetermined function;

(e) determine a shifted zero-input response of the digital filter by converting the contents of the first and second data blocks to the frequency domain and convert a product of the first and second data blocks in the frequency domain to the time domain;

(f) shift the shifted zero-input response of the digital filter in accordance with a predetermined function to determine the zero-response of the digital filter;

(g) receive one of the zero-state signals and convolve said one of the zero-state signals with a corresponding impulse response of the digital filter to determine a respective zero-state response of the digital filter, wherein said one of the zero-input signals at least partially precedes said one of the zero-state signals; and

(h) add the zero-state response to the zero-input response to produce an output of the digital filter that is a response of the digital filter to the input data stream.

18. The long impulse response digital filter of claim 17, wherein the digital filter is structured to convert the contents of the first and second data blocks from the time domain to the frequency domain by effecting 2N-point transforms and to convert from the frequency domain to the time domain by effecting 2N-point inverse transforms.

19. The long impulse response digital filter of claim 17, wherein the digital filter is structured to have multiple stages in which later stages are provided by dividing zero-state signals into zero-input and zero-state signals.

20. The method of claim 17, wherein the output of the digital filter corresponds to:

21. A long impulse response digital filter for filtering an input data stream to improve signal accuracy in electronic systems, the filter structured to:

divide the input data stream into zero-input signals and zero-state signals;

convert one of the zero-input signals and a corresponding impulse response of the digital filter to the frequency domain;

convert the product of the zero-input signal and the impulse response of the frequency domain to the time domain for determining a respective zero-input response of the digital filter;

convolve one of the zero-state signals with a corresponding impulse response of the digital filter to determine a respective zero-state response of the digital filter, wherein at least part of the zero-input signal precedes the zero-state signal; and

add the zero-state response to the zero-input response to produce an output of the digital filter that is a response of the digital filter to the input data stream.

22. The long impulse response digital filter of claim 21, wherein the digital filter is structured to:

convert one of the zero-input signals by appending a first plurality of zeroes to the one of the zero-input data signals to form a first data block of a predetermined size, and to append a second plurality of zeroes to the corresponding impulse response of the digital filter to form a second data block of a predetermined size, wherein the first and second data blocks are of equal size;

to shift the contents of the first data block in accordance with a predetermined function to produce a shifted first data block;

to convert at least one of the zero-input signals and the corresponding input signal response of the digital filter to the frequency domain by converting the shifted first data block and the second data block to the frequency domain; and

to convert the product of the shifted first data block and the second data block back to the time domain to determine the shifted zero input response of the digital filtering system.

23. The method of claim 21, wherein the output of the digital filter corresponds to: