CN105306008A - Interpolation filtering processing method of arbitrary sampling rate conversion - Google Patents
Interpolation filtering processing method of arbitrary sampling rate conversion Download PDFInfo
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- CN105306008A CN105306008A CN201510780444.6A CN201510780444A CN105306008A CN 105306008 A CN105306008 A CN 105306008A CN 201510780444 A CN201510780444 A CN 201510780444A CN 105306008 A CN105306008 A CN 105306008A
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Abstract
The invention relates to an interpolation filtering processing method of arbitrary sampling rate conversion. The method comprises the following steps of: (1) generating a FIR filter tap coefficient table according to bandwidth requirement and filtering precision coefficient of input signals; (2) generating a double data clock signal Rs by NCO, and obtaining clock phase Phase of the clock signal; (3) executing signal receiving through the double data clock signal; (4) extracting corresponding filter coefficient in a FIR filter coefficient table according to the clock phase Phase; (5) applying the extracted filter coefficient to a FIR filter, filtering the received signal, thereby converting the sampling rate of the input signal to a system work frequency fs from Rs, and realizing interpolation filtering processing of sampling rate conversion. In the method, the interpolation filter used is composed of a transversal FIR filter and a ROM table in which the filter coefficient is bound. The method is simple to implement, consumes less hardware resource and is highly practical.
Description
Technical field
The present invention relates to digital filtering technique field, particularly a kind of interpolation filtering processing method of any sample rate conversion.
Background technology
In existing digital interpolation design of filter, signal sampling rate is changed to system works clock, in order to adapt to the variable requirement of data rate, a kind of method is the speed according to transmission data, employing reconfigures clock chip to change DA work clock, and this method limits by hardware platform; Another method adopts multiple filter to carry out integral multiple filtering interpolation for specific several speed, and this method filter order is many, complex structure, consumes resources are huge, and data rate can not continuous variable, and practicality is not strong.
Summary of the invention
The object of the invention is to overcome the deficiencies in the prior art, provide a kind of interpolation filtering processing method of any sample rate conversion, the interpolation filter adopted in the method is shown to form by the ROM of filter coefficient by a horizontal FIR filter and a bookbinding, within each system works clock fs cycle, interpolation filter coefficient table is searched according to the clock phase phase after quantizing, real-time update FIR filter coefficient also carries out filtering operation, obtaining sample rate is signal after the interpolation of fs, this interpolation filtering method realizes simple, expend hardware resource few, practical.
Technical scheme of the present invention is: a kind of interpolation filtering processing method of any sample rate conversion, comprises the following steps:
1) according to the bandwidth B w of input signal and the resolution 1/K of input signal, generate K group filter coefficient, and described K group filter coefficient is kept in newly-established FIR filter tap coefficient table; Wherein, the resolution parameter K=2 of input signal
l, L is positive integer;
2) according to code check Rb and the system clock frequency fs of input signal, NCO is adopted to produce 1 haplotype data clock signal, the frequency Rs=Rb of described data clock signal, the clock phase Phase of described data clock signal equals the high L position intercepting value of described NCO accumulated value, and namely the span of described clock phase Phase is 0 ~ K-1; Wherein, the bit wide of described NCO is M and M >=L;
3) according to step 2) the 1 haplotype data clock signal that produces receives input signal, obtains Received signal strength;
4) according to the value of the clock phase Phase in Signal reception moment, in step 1) extract the tap coefficient of FIR filter in the FIR filter tap coefficient table that produces;
5) by step 4) extract the FIR filter coefficient that obtains and be applied in FIR filter, interpolation filtering process is carried out to the Received signal strength obtained in step (3), obtains signal after interpolation filtering.
In step 1) in, according to the bandwidth B w of input signal and the resolution 1/K of input signal, generate K group filter coefficient, and be kept in FIR filter tap coefficient table by described K group filter coefficient, specific implementation process is as follows:
1a) according to the bandwidth B w of input signal, generate tap coefficient h (n) that a group meets the FIR filter of filtering requirements in described signal bandwidth, wherein, n=1,2 ..., N, N are the tap number of described FIR filter;
1b) obtain K proportion function according to the resolution 1/K of input signal, wherein, a described kth proportion function is
k=1,2 ..., K, n=1,2 ..., N;
1c) to step 1a) FIR filter tap coefficient h (n) that obtains carries out leaf transformation in N point discrete Fourier, obtain FIR filter response function H (jw)=DFT (h (n)), wherein, DFT () represents discrete Fourier transform; N number of value of described response function H (jw) is respectively h
1, h
2..., h
n..., h
n;
1d) according to step 1b) K proportion function obtaining and step 1c) the response function H (jw) that obtains, obtain K new response function, wherein, a described kth new response function is H '
k(jw), H '
k(jw) N number of value is respectively h '
1, h '
2..., h '
n..., h '
n, wherein, h '
n=h
n× f
k(n), k=1,2 ..., K, n=1,2 ..., N;
1e) to step 1d) K that obtains a new response function carries out inverse Fourier transform and obtains K group filter coefficient, and wherein, described kth group filter coefficient is h '
k(n)=IDFT (H '
k(jw)), IDFT represents inverse discrete Fourier transform, k=1, and 2 ..., K;
1f) by step 1e) in obtain K group filter coefficient successively stored in tables of data, obtain FIR filter tap coefficient table.
Described FIR filter tap coefficient table bookbinding is in ROM table.
Step 4) if in described clock phase Phase=k-1, then in described FIR filter tap coefficient table extract obtain kth group low-pass FIR filter coefficient h '
k(n), wherein, k=1,2 ..., K, n=1,2 ..., N, N are the tap number of described FIR filter.
The present invention's advantage is compared with prior art:
(1), the present invention adopts fraction double interpolation filter to realize the sample rate of different rates signal by the sample rate conversion of signal frequency to system operating frequency, and implementation structure is simple, and can meet the continuous variable requirement of input signal, practical.
(2) fraction double interpolation filter of the present invention is shown to form by the ROM of filter coefficient by a horizontal FIR filter and a bookbinding, within each system works clock fs cycle, internal filter coefficients table is searched according to the clock phase phase after quantizing, real-time update FIR filter coefficient also carries out filtering operation, and obtaining sample rate is signal after the interpolation of fs.This filter implementation method is simple, and hardware resource used is few, effectively can overcome that prior art is simple by the interpolation filter structure in hardware platform restriction, the inventive method, operand is little.
(3) the ROM table size of the bookbinding filter coefficient used in the present invention can adjust flexibly according to the requirement of input signal resolution, can meet performance requirement, again can saving resource, and flexibility is strong.
Accompanying drawing explanation
Fig. 1 is the process flow block diagram of interpolation filtering processing method of the present invention.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail:
Shown in process flow block diagram of the present invention as shown in Figure 1, the interpolation filtering processing method of any sample rate conversion of the present invention, comprises the following steps:
(1), according to the bandwidth B w of input signal and the resolution 1/K of input signal, generate K group filter coefficient, and described K group filter coefficient is kept in FIR filter tap coefficient table; Wherein, the resolution parameter K=2 of input signal
l, L is positive integer; Specific implementation step is as follows:
(1a), according to signal bandwidth Bw, generate tap coefficient h (n) that a group meets the FIR filter of filtering requirements in described signal bandwidth, described filtering requirements refers to the requirement to filter practical function, performance; Wherein, n=1,2 ..., N, N are the tap number of described FIR filter;
(1b), according to the quality coefficient K of setting obtain K proportion function, wherein, a kth described proportion function is
k=1,2 ..., K, n=1,2 ..., N;
(1c), leaf transformation in N point discrete Fourier is carried out to FIR filter tap coefficient h (n) that step (1a) obtains, obtain FIR filter response function H (jw)=DFT (h (n)), wherein, DFT () represents discrete Fourier transform; N number of value of described response function H (jw) is respectively h
1, h
2..., h
n..., h
n;
(1d) the response function H (jw) that K the proportion function, according to step (1b) obtained and step (1c) obtain, obtain K new response function, wherein, the response function after a kth described renewal is H '
k(jw), H '
k(jw) N number of value is respectively h '
1, h '
2..., h '
n..., h '
n, wherein, h '
n=h
n× f
k(n), k=1,2 ..., K, n=1,2 ..., N;
(1e) K the new response function, to step (1d) obtained carries out inverse Fourier transform and obtains K group filter coefficient, and wherein, filter coefficient described in kth group is h '
k(n)=IDFT (H '
k(jw)), IDFT represents inverse discrete Fourier transform, k=1, and 2 ..., K;
(1f), K group filter coefficient will be obtained in step (1e) successively stored in tables of data, obtain FIR filter tap coefficient table, this FIR filter tap coefficient table can be bound and be shown at ROM, be convenient to hardware implementing, can with horizontal FIR filter conbined usage, realize the filtering interpolation process of variable sampling rate.
In the present embodiment, FIR filter is set as the transversal filter on 32 rank, namely has 32 delay cells, altogether N=33 tap coefficient; And setting input signal resolution 1/K, K=256, i.e. positive integer L=8;
(2), according to code check Rb and the system clock frequency fs of input signal, NCO (digital oscillator) is adopted to produce 1 haplotype data clock signal, the frequency Rs=Rb of described data clock signal, the clock phase Phase of described data clock signal equals the high L position intercepting value of described NCO accumulated value, and namely the span of described clock phase Phase is 0 ~ K-1; Wherein, the bit wide of described NCO is M and M >=L; The operating frequency of this NCO is fs;
In the present embodiment, the bit wide of NCO is M=32, and when the input signal resolution parameter K=256 set, clock phase phase is the most-significant byte intercepting value of NCO accumulated value, and that is the value of clock phase is 0 ~ 255; In the present invention, adopt this clock phase to obtain the extraction sequence number of FIR filter coefficient exactly, the coefficient realizing filtering interpolation extracts.
(3) the 1 haplotype data clock signal, according to step (2) produced receives input signal, obtains Received signal strength; Namely the sample rate of this Received signal strength is Rs, and object of the present invention is exactly be converted to systematic sampling rate by unified for the sample rate of this signal, and ensures that signal is undistorted;
(4), according to the value of the phase place Phase of Signal reception clock, the tap coefficient of FIR filter is extracted in the FIR filter tap coefficient table that step (1) produces, wherein, if described clock phase Phase=k-1, then in described FIR filter tap coefficient table extract obtain kth group low-pass FIR filter coefficient h '
k(n), wherein, k=1,2 ..., K, n=1,2 ..., N, N are the tap number of described FIR filter;
(5), step (4) being extracted the FIR filter coefficient obtained is applied in FIR filter, interpolation filtering process is carried out to the Received signal strength obtained in step (3), obtain signal after interpolation filtering, the sample rate of this signal is fs, namely be that the Interpolation of signals of Rs is filtered into the signal that sample rate is fs through to process sample rate above, thus realize the conversion of sample rate.
In the present embodiment, interpolation filter of the present invention is shown to form by the ROM of filter coefficient by a horizontal FIR filter in 32 rank and a bookbinding.Within each system works clock fs cycle, according to the clock phase phase after quantizing, in ROM table, search filter coefficient, real-time update FIR filter coefficient also carries out filtering operation, and obtaining sample rate is signal after the interpolation of fs.If quantized by 16 each filter factor, clock phase phase quantizes by 8, then the memory space of binding the ROM table of FIR filter coefficient is 33*16*2
8=135168bit.
The present invention adopts the fraction double interpolation filter of variable coefficient, realizes the filtering of different rates signal interpolation, and whole function can adopt FPGA to realize.
The above; be only the embodiment of the best of the present invention, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.
The content be not described in detail in specification of the present invention belongs to professional and technical personnel in the field's known technology.
Claims (4)
1. an interpolation filtering processing method for any sample rate conversion, is characterized in that comprising the following steps:
1) according to the bandwidth B w of input signal and the resolution 1/K of input signal, generate K group filter coefficient, and described K group filter coefficient is kept in newly-established FIR filter tap coefficient table; Wherein, the resolution parameter K=2 of input signal
l, L is positive integer;
2) according to code check Rb and the system clock frequency fs of input signal, NCO is adopted to produce 1 haplotype data clock signal, the frequency Rs=Rb of described data clock signal, the clock phase Phase of described data clock signal equals the high L position intercepting value of described NCO accumulated value, and namely the span of described clock phase Phase is 0 ~ K-1; Wherein, the bit wide of described NCO is M and M >=L;
3) according to step 2) the 1 haplotype data clock signal that produces receives input signal, obtains Received signal strength;
4) according to the value of the clock phase Phase in Signal reception moment, in step 1) extract the tap coefficient of FIR filter in the FIR filter tap coefficient table that produces;
5) by step 4) extract the FIR filter coefficient that obtains and be applied in FIR filter, interpolation filtering process is carried out to the Received signal strength obtained in step (3), obtains signal after interpolation filtering.
2. the interpolation filtering processing method of a kind of any sample rate conversion according to claim 1, it is characterized in that: in step 1) in, according to the bandwidth B w of input signal and the resolution 1/K of input signal, generate K group filter coefficient, and described K group filter coefficient is kept in FIR filter tap coefficient table, specific implementation process is as follows:
1a) according to the bandwidth B w of input signal, generate tap coefficient h (n) that a group meets the FIR filter of filtering requirements in described signal bandwidth, wherein, n=1,2 ..., N, N are the tap number of described FIR filter;
1b) obtain K proportion function according to the resolution 1/K of input signal, wherein, a described kth proportion function is
k=1,2 ..., K, n=1,2 ..., N;
1c) to step 1a) FIR filter tap coefficient h (n) that obtains carries out leaf transformation in N point discrete Fourier, obtain FIR filter response function H (jw)=DFT (h (n)), wherein, DFT () represents discrete Fourier transform; N number of value of described response function H (jw) is respectively h
1, h
2..., h
n..., h
n;
1d) according to step 1b) K proportion function obtaining and step 1c) the response function H (jw) that obtains, obtain K new response function, wherein, a described kth new response function is H '
k(jw), H '
k(jw) N number of value is respectively h '
1, h '
2..., h '
n..., h '
n, wherein, h '
n=h
n× f
k(n), k=1,2 ..., K, n=1,2 ..., N;
1e) to step 1d) K that obtains a new response function carries out inverse Fourier transform and obtains K group filter coefficient, and wherein, described kth group filter coefficient is h '
k(n)=IDFT (H '
k(jw)), IDFT represents inverse discrete Fourier transform, k=1, and 2 ..., K;
1f) by step 1e) in obtain K group filter coefficient successively stored in tables of data, obtain FIR filter tap coefficient table.
3. the interpolation filtering processing method of a kind of any sample rate conversion according to claim 1, is characterized in that: described FIR filter tap coefficient table bookbinding is in ROM table.
4. the interpolation filtering processing method of a kind of any sample rate conversion according to claim 1, it is characterized in that: step 4) if in described clock phase Phase=k-1, then in described FIR filter tap coefficient table extract obtain kth group low-pass FIR filter coefficient h '
k(n), wherein, k=1,2 ..., K, n=1,2 ..., N, N are the tap number of described FIR filter.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1371179A (en) * | 2001-02-20 | 2002-09-25 | 三星电子株式会社 | Sample rate converting device and method |
| US20070041438A1 (en) * | 2004-01-30 | 2007-02-22 | Sony Corporation | Sampling rate conversion device and method, and audio device |
| WO2011090110A1 (en) * | 2010-01-25 | 2011-07-28 | 三菱電機株式会社 | Sampling rate conversion device, and sampling rate conversion method |
| CN104539261A (en) * | 2014-12-08 | 2015-04-22 | 北京遥测技术研究所 | Arbitrary sampling rate conversion interpolation filtering processing method |
-
2015
- 2015-11-13 CN CN201510780444.6A patent/CN105306008A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1371179A (en) * | 2001-02-20 | 2002-09-25 | 三星电子株式会社 | Sample rate converting device and method |
| US20070041438A1 (en) * | 2004-01-30 | 2007-02-22 | Sony Corporation | Sampling rate conversion device and method, and audio device |
| WO2011090110A1 (en) * | 2010-01-25 | 2011-07-28 | 三菱電機株式会社 | Sampling rate conversion device, and sampling rate conversion method |
| CN104539261A (en) * | 2014-12-08 | 2015-04-22 | 北京遥测技术研究所 | Arbitrary sampling rate conversion interpolation filtering processing method |
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