METHOD FOR EFFICIENT AND ZERO LATENCY FILTERING IN A LONG IMPULSE RESPONSE SYSTEM

• US 20080155001A1
• Filed: 11/19/2007
• Published: 06/26/2008
• 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
• Granted Patent: US 8,340,285 B2
• Time in Patent Office: Days
• US Class Current: 708/300
• 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 lo 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-stale signal. The zero-state response of the digital filtering system is added to the zero-input response or 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 by use of a digital filtering system to improve signal accuracy in electronic systems, comprising the steps of:

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

(b) performing 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 the product of the zero-input signal and the impulse response in the frequency domain to the time domain to determine a respective zero-input response of the digital filtering system;

(c) convolving 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 at least part of the zero-input signal precedes the zero-state signal; and

(d) determining a response of the digital filtering system by adding the zero-state response to the zero-input response to increase signal accuracy in the filtered input data stream.

2. The method of claim 1, wherein the zero-input signal comprises a first plurality of input data samples from the input data stream and the zero-state signal comprises 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 step of converting one of the zero-input signals and a corresponding impulse response of the digital filtering system to the frequency domain:

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

(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) determining a response of the digital filtering system by adding the zero-state response to the zero-input response to increase signal accuracy in the filtered input data stream.

5. A method for long impulse response digital filtering of an input data stream to improve signal accuracy in electronic systems, where the input data stream comprises first and second data sequences, by use of a digital filtering system, including the steps of:

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

(b) receiving one of the second data sequences, comprising 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 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 filtering system 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 first response of the digital filtering system by converting the first and second fixed sized data blocks to the frequency domain and then converting their product to the time domain;

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

(h) determining a response of the digital filtering system by adding the second response to the first response to increase signal accuracy in the filtered input data stream.

6. The method of claim 5 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.

7. A method for long impulse response digital filtering of an input data stream by use of a digital filtering system to improve signal accuracy in electronic systems, including the steps of:

(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) determining a response of the digital filtering system by 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 increase signal accuracy in the filtered input data stream.

8. The method of claim 7, wherein further stages are created by dividing zero-state signals into zero-input and zero-state signals.

9. A long impulse response digital filter for filtering an input data stream to improve signal accuracy in electronic systems comprising:

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

(b) a first means for converting one of the zero-input signals and a corresponding impulse response of the digital filter to the frequency domain and a second means for converting 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) means for convolving 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) means for determining a response of the digital filter by adding the zero-state response to the zero-input response to increase signal accuracy in the filtered input data stream.

10. The long impulse response digital filter of claim 9, wherein the zero-input signal comprises a first plurality of input data samples from the input data stream and the zero-state signal comprises 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.

11. The long impulse response digital filter of claim 9, wherein further means are included prior to the means for converting said one of the zero-input signals and the corresponding impulse response of the digital filter to the frequency domain, the further means comprising:

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

wherein the means for the first conversion comprises means for converting the shifted first data block and the second data block to the frequency domain and the means for the second conversion comprises means for converting 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

the apparatus further comprises a means for shifting 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.

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

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

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

(e) means for 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 means for converting a product of the first and second data blocks in the frequency domain to the time domain;

(f) means for 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) means for 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) means for determining a response of the digital filtering system by adding the zero-state response to the zero-input response to increase signal accuracy in the filtered input data stream.

13. A long impulse response digital filter for filtering an input data stream, where the input data stream comprises first and second data sequences to improve signal accuracy in electronic systems, comprising:

(a) means for receiving one of the first data sequences, comprising a first plurality of input data samples from the input data stream;

(b) means for receiving one of the second data sequences, comprising a second plurality of input data samples from the input data stream, wherein at least one of the data samples in the second plurality of input data samples is preceded by the first plurality of data samples;

(c) means for determining an impulse response of the digital filter;

(d) means for storing the first data sequence in a first fixed sized data block, wherein remaining space in the first fixed sized data block is occupied by zero data units;

(e) means for 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) means for determining a first 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;

(g) means for determining a second response of the digital filtering system by convolving a plurality of input data samples, with the impulse response of the system; and

(h) means for determining a response of the digital filtering system by adding the second response to the first response to increase signal accuracy in the filtered input data stream.

14. The long impulse response digital filter of claim 13, wherein the means for converting from the time domain to the frequency domain comprises means for effecting 2N-point transforms and the means for converting from the frequency domain to the time domain comprises means for effecting 2N-point inverse transforms.

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

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

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

(c) means for 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 filter;

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

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

(f) means for determining a second stage zero-input response of the digital filter 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) means for determining a second stage zero-state impulse response of the digital filter by convolving the second stage zero-state signal with a corresponding impulse response of the digital filter;

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

(i) means for determining a response of the digital filter by adding the first stage zero-state response of the digital filter to the first stage zero-input response of the digital filter to increase signal accuracy in the filtered input data stream.

16. The long impulse digital filter of claim 15, wherein further stages are provided by dividing zero-state signals into zero-input and zero-state signals.

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

a divider circuit for dividing the input data stream into zero-input signals and zero-state signals;

a first conversion circuit for converting one of the zero-input signals and a corresponding impulse response of the digital filter to the frequency domain;

a second conversion circuit for converting 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;

a convolving circuit configured to 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

an adder circuit for determining a response of the digital filter by adding the zero-state response to the zero-input response to increase signal accuracy in the filtered input data stream.

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

a divider circuit for dividing the input data stream into zero-input signals and zero-state signals;

an appending circuit for 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;

a second appending circuit configured 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;

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

a first conversion circuit for converting at least one of the zero-input signals and a corresponding input signal response of the digital filter to the frequency domain, the first conversion circuit configured to convert the shifted first data block and the second data block to the frequency domain, and a second conversion circuit configured 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;

a second shifting circuit configured to 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 to increase signal accuracy in the filtered input data stream.

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

a divider circuit configured to receive the input data stream and to generate in response thereto corresponding zero-input signals and zero-state signals;

an appending circuit configured to receive the zero-input signals and to append a first plurality of zeroes to each of the zero-input signals in order to form a first data block of a predetermined size;

an impulse response determining circuit configured to determine the impulse response of the digital filtering system that corresponds to each of the zero-input signals and to append a second plurality of zeroes to the impulse response of the digital filtering system to form a second data block of a predetermined size, with the first and second data blocks of equal size;

a first shifting circuit configured to shift the contents of the first data block in accordance with a predetermined function;

a determining circuit configured to determine 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;

a conversion circuit for converting a product of the first and second data blocks in the frequency domain to the time domain;

a second shifting circuit configured to shift the zero-input response of the digital filtering system in accordance with a predetermined function to determine the zero-response of the digital filtering system;

a convolving circuit configured to receive each of the zero-state signals and to convolve each 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 at least one of the zero-input signals at least partially precedes at least one of the zero-state signals; and

an adder circuit configured to determine a response of the digital filtering system by adding the zero-state response to the zero-input response to increase signal accuracy in the filtered input data stream.

20. A long impulse response digital filter for filtering an input data stream to improve signal accuracy in electronic systems, where the input data stream includes first and second data sequences, comprising:

an input configured to receive one of the first data sequences that includes a first plurality of input data samples from the input data stream;

a second input configured to receive one of the second data sequences that include a second plurality of input data samples from the input data stream, with at least one of the data samples in the second plurality of input data samples preceded by the first plurality of data samples;

an impulse response circuit configured to determine an impulse response of the digital filter;

a first storage for storing the first data sequence in a first fixed sized data block wherein the remaining space in the first fixed size data block is occupied by zero data units;

a second storage for storing the impulse response of the digital filter in a second fixed sized data block with the remaining space of the second fixed sized data block occupied by zero data units, with the first and second fixed sized data blocks of equal size;

a converting circuit for determining a first response of the digital filter by converting the first and second fixed sized data blocks to the frequency domain and then converting a product thereof to the time domain;

a convolving circuit configured to determine a second response of the digital filtering system by convolving a plurality of input data samples with the impulse response of the system; and

an adder circuit configured to determine a response of the digital filtering system by adding the second response to the first response to increase signal accuracy in the filtered input data stream.