CN1567728A - Conversion device and method for sampling frequency and uses thereof - Google Patents
Conversion device and method for sampling frequency and uses thereof Download PDFInfo
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- CN1567728A CN1567728A CN 03140971 CN03140971A CN1567728A CN 1567728 A CN1567728 A CN 1567728A CN 03140971 CN03140971 CN 03140971 CN 03140971 A CN03140971 A CN 03140971A CN 1567728 A CN1567728 A CN 1567728A
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Abstract
The invention provides a sampling frequency converting device, including a noise shaper and a sampling frequency converter, where the noise shaper receives and shapes a digital input signal and outputs a n-bit digit flow and the sampling frequency converter is connected with the noise shaper to receive the n-bit digit flow and outputs a digital signal. Because the sampling frequency converter makes sampling frequency conversion by nonintegral multiplying power and the n-bit digit flow is a digital signal with less bits, for example of a 1-bit signal, as calculating the numerical value at each interpolation point, it only need to add by interpolation function, thus able to use smaller circuit area to complete this.
Description
(1) technical field
Relevant a kind of sampling frequency conversion equipment of the present invention and method thereof in order to produce the sampling frequency of any multiplying power, especially can produce the sampling frequency of a non-integer multiplying power.
(2) background technology
Seeing also Fig. 1 (a) and Fig. 1 (b), is to be typical single order and second-order increment-summation (Delta-Sigma) modulator (modulator).The Delta-Sigma modulator be basically with conversion of signals be the lower signal of bit number (for example, the signal of one bit), make the latter have identical spectrum component at low frequency with the former, make the noise of its quantization error (quantization error) concentrate on HFS, see also Fig. 2 (a) and Fig. 2 (b).
Seeing also Fig. 3, is to cross sampling Delta-Sigma digital-analog convertor for a typical case.As shown in Figure 3, (Sample Rate Converter, SRC) 100 raising frequencies produce one and cross the sampling digital signal input signal via a sampling frequency converter.This sampling frequency converter 100 comprises a upconverter (expander) 101 and a wave digital lowpass filter (digital low-pass filter) 102.This crosses the sampling digital signal, converts the lower digital signal of bit number (being generally 1 bit) to via a Delta-Sigma transducer 103.The digital signal that this bit number is lower, its radio-frequency component have added the high frequency noise that is produced because of via Delta-Sigma transducer 103 in addition except that the frequency content of original input signal.The digital signal that the bit number that Delta-Sigma transducer 103 is produced is lower produces an analog signal via digital-analog convertor (DAC) the 104 digital signal conversions that this bit number is lower again.This analog signal promptly produces an output analog signal via the high frequency noise that the previous Delta-Sigma transducer 103 of a low pass filter (LPF) 105 filterings is produced.
In the prior art, be with the digital signal addition of two different sampling frequencies (Sample Rate), and be converted to analog signal, generally be respectively two digital conversion of signals to be become analog signal, afterwards again with two analog signal additions.See also Fig. 4 (a).Yet Analog Circuit Design, the layout time-histories is longer, and the characteristic usefulness of analog circuit is subject to the processing procedure influence.Along with the progress of process technique, the digital circuit area diminishes fast, therefore more and more many circuit will be arranged, and replaces analog form with digital form, and the analog circuit area is huge to solve, the design time-histories is long and circuit characteristic is subject to problems such as processing procedure influence.
Seeing also Fig. 4 (b), is the method for handling foregoing problems with the prior art of Digital Signal Processing.This method no doubt can be avoided the analog circuit problems, yet, the difficulty that it faces, (Over-Sample Rate OSR) is difficult to select to be the operated mistake sampling frequency of shared Delta-Sigma transducer and digital-analog convertor (DAC).If two groups of sampling frequency converters, one group raising frequency multiplying power wherein, select 2 power value (powerof two, for example 64,128 or 256), on side circuit is realized, carry out easily, then another organizes sampling frequency converter, the power of its raising frequency multiplying power possibility non-2, even possibility non-integer (for example need expend more resources, bigger circuit area, or computing unit faster) could realize.With Fig. 4 (b) is example, sampling frequency f1=48KHz wherein, f2=50KHz.If the raising frequency multiplying power of first sampling frequency converter is 128, then the raising frequency multiplying power of second sampling frequency converter is necessary for 128*48/50=122.88, and both output just can have identical sampling frequency f=6.144MHz.Therefore the latter will expend more resources.
(3) summary of the invention
First purpose of the present invention is to provide a kind of sampling frequency conversion equipment and method thereof, in order to produce the sampling frequency of any multiplying power, especially can produce the sampling frequency of a non-integer multiplying power.
Second purpose of the present invention is to provide a kind of sampling frequency conversion equipment, implements with digital circuit, and the analog circuit area is huge to solve, the design time-histories is long and circuit characteristic is subject to problems such as processing procedure influence.
The 3rd purpose of the present invention is to provide a kind of digital-analog convertor to have the conversion equipment that can produce any sampling frequency.In this digital-analog convertor, digital signal is converted to the digital signal with required sampling frequency, to make things convenient for the processing of subsequent conditioning circuit.
The 4th purpose of the present invention is to provide a kind of sampling frequency conversion equipment, can carry out the sampling frequency conversion of non-integer multiplying power, and reduces the complexity of computing, only need the interpolating function addition, with reduce circuit area with and cost.
For achieving the above object, the invention provides a kind of sampling frequency conversion equipment, it comprises a noise reshaper and a sampling frequency converter.This noise reshaper, in order to receiving a digital input signals, and with this digital input signals through noise shaping conversion after, export a n bit digital stream.This sampling frequency converter is to be electrically connected this noise reshaper, receives this n bit digital stream, and is output as a digital output signal.
Because this n bit digital stream is the less digital signal of bit number, is example with a bit signal, when calculating each interpolated point numerical values recited, only need to use more small circuit area occupied finishing like this with the interpolating function addition.
The present invention is by the following drawings and detailed description and can obtain a more deep understanding.
(4) description of drawings
Fig. 1 (a) is existing single order Delta-Sigma modulator;
Fig. 1 (b) is existing second order Delta-Sigma modulator;
Fig. 2 (a) is the output waveform schematic diagram that existing string ripple signal produces through the Delta-Sigma modulation;
Fig. 2 (b) is the spectrum analysis schematic diagram that existing string ripple signal produces through the Delta-Sigma modulation;
Fig. 3 had sampling Delta-Sigma digital-analog convertor now;
Fig. 4 (a) is the prior art with simulation, and the digital signal of two different sampling frequencies (Sample Rate) is converted to analog signal addition schematic diagram;
Fig. 4 (b) is the prior art with Digital Signal Processing, with the schematic diagram of the digital signal addition of two different sampling frequencies;
Fig. 5 (a) is the sampling frequency converter structural representation of the embodiment of the invention;
Fig. 5 (b) is the mistake number of samples analog-to-digital converter structural representation of Application Example of the present invention;
Fig. 6 (a) is non-integer type sampling frequency converter (SRC) schematic diagram;
Fig. 6 (b) is the technology with Digital Signal Processing, carries out non-integer sampling frequency conversion schematic diagram; And
Fig. 7 is the digital-analog convertor structural representation of another embodiment of the present invention.
(5) embodiment
See also the sampling frequency conversion equipment 200 of Fig. 5 (a), a kind of sampling frequency conversion equipment 200 of the present invention comprises a noise reshaper 203 and a sampling frequency converter 204.This noise reshaper 203 receives one first up-conversion signal, and its sampling frequency is f
4, and, export a noise reshaping signal with after this first up-conversion signal process noise shaping conversion.This noise reshaping signal, its sampling frequency is identical with this first up-conversion signal, and has low bit number.This sampling frequency converter 204 is to be electrically connected this noise reshaper 203, receives this noise reshaping signal, and exports a three digital signal, and its sampling frequency is f
3This sampling frequency converter 204, when calculating the interpolation numerical values recited of novel sampling location, because this noise reshaping signal has low bit number, thereby amount of calculation abbreviation significantly.With a bit signal is example, and the calculating of interpolation numerical value only can be finished with addition, need not utilize mlultiplying circuit.
The execution mode of this noise reshaper 203 can adopt the Delta-Sigma modulator of prior art or any circuit with quantification noise (quantization noise) shaping effect.
General this sampling frequency converter 204 comprises: a digital analog converter 209, a low pass filter 210 and a sample circuit 211.See also Fig. 6 (a).Wherein, this digital analog converter 209 is in order to receiving this noise reshaping signal, and this noise reshaping signal is converted to one first continuous time signal, and its waveform is as stepped.This low pass filter 210 is to be electrically connected this digital analog converter 209, and this first continuous signal is carried out filtering, produces one second continuous time signal.And this sample circuit 211 is to be electrically connected this low pass filter 210, and this second continuous time signal sampling is produced this three digital signal, and its sampling frequency is f
3Because when 211 pairs of aforementioned second continuous time signals of aforementioned sample circuit are taken a sample, in the middle of second continuous time signal, specific high frequency composition will cause assumed name effect (aliaseffect), influence sampling frequency conversion quality.Therefore aforementioned low pass filter 210, promptly in the middle of the prior art, so-called antialiasing filtering (anti-alias filter), its function is the aforementioned specific high frequency composition of filtering in advance, to avoid taking place the assumed name effect.
Aforementioned concepts all can use digital form to finish.Wherein, aforementioned digital analog converter 209 and aforementioned low pass filter 210, its impulse response (impulse response) is equivalent to an interpolating function (interpolation function), sees also Fig. 6 (b).Therefore, aforementioned sample circuit 211 is with sampling frequency f
3,, in the middle of digital circuit, promptly be equivalent to sampling frequency f to aforementioned second continuous time signal sampling
3, demarcate the position of each interpolated point, and, calculate the numerical values recited of this interpolated point with aforementioned interpolating function.The execution mode of interpolating function can use hardware computing function value, also can use read-only memory (ROM), is implemented with look-up table.
For example, make x[n]=+ 1 or-1, represent the noise shaping signal of an aforementioned bit, wherein n is an integer, the express time sequence.X
c(n) expression state second continuous time signal, X
c(n)=and ∑ x[i] F (n-i), wherein F (x) is an interpolating function.Because X
cBe signal continuous time, therefore wherein employed parameter n can be non-integer.With sampling frequency f
3After resampling, its output can be expressed as y[n]=X
c((f
3/ f
4) n)=∑ x[i] F ((f
3/ f
4) n-i).During enforcement, only need calculate y[n]=∑ x[i] F ((f
3/ f
4) n-i), wherein F (x) functional value can utilize read-only memory to store, because x[n]=+ 1 or-1, calculate y[n] time, only need table look-up and add (subtracting) method, need not to use multiplication.
By aforementioned noise reshaper 203, add aforementioned sampling frequency converter 204, can finish the power part of raising frequency multiplying power central non-2.Its advantage is: the output signal of noise reshaper 203, the bit number is low (for example: a bit), can significantly lower aforementioned sampling frequency converter 204, carry out the sampling frequency conversion of non-integer multiplying power, the complexity of required computing.With a bit signal is example, when calculating each interpolated point numerical values recited, only needs the interpolating function addition need not used multiplication, can significantly reduce resource requirement (for example, can use littler circuit area to finish aforementioned work) like this.Otherwise, carry out the non-integral number frequency multiplication raising frequency in a conventional manner, owing to be not, need a large amount of multiplication with a bit signal interpolation, just can finish.
Seeing also Fig. 5 (b), is the mistake number of samples analog-to-digital converter structural representation for Application Example of the present invention.Shown in Fig. 5 (b), a kind of number of samples analog-to-digital converter of crossing comprises one first sampling frequency converter 201, one second sampling frequency converter 202, one first noise reshaper 203, one the 3rd sampling frequency converter 204, a digital synthesizer 205, one second noise reshaper 206, a digital-analog convertor 207 and a low pass filter 208.Wherein, this first sampling frequency converter 201 is in order to receive one first digital signal, and this first digital signal has one first sampling frequency f
1And with this first digital signal raising frequency to produce one first up-conversion signal, this first up-conversion signal has one the 3rd sampling frequency f
3=128f
1This second sampling frequency converter 202 is in order to receive one second digital signal, and this second digital signal has one second sampling frequency f
2And with this second digital signal with 2 power numerical value 128 raising frequencies to produce one second up-conversion signal, this second up-conversion signal has one the 4th sampling frequency f
4=128f
2This first noise reshaper 203 is electrically connected these second sampling frequency converters 202, in order to receiving this second up-conversion signal, and this second up-conversion signal conversion is output as one the 1 bit (1-bit) digital stream after the noise shaping.The 3rd sampling frequency converter 204 is to be electrically connected this first noise reshaper 203, receives the one 1 bit digital stream, the conversion of the one 1 bit digital stream is output as a three digital signal has sampling frequency f
3This digital synthesizer 205 is to be electrically connected the 3rd sampling frequency converter 204 and this first sampling frequency converter 201, will have identical sampling frequency f
3This three digital signal and this first up-conversion signal addition, produce a composite signal.This second noise reshaper 206 is to be electrically connected this digital synthesizer 205, and this composite signal conversion is output as one the 21 bit digital stream after the noise shaping.And this digital-analog convertor 207 is to be electrically connected this second noise reshaper 206, with the 21 bit digital stream conversion output one analog signal.Wherein being somebody's turn to do the number of samples analog-to-digital converter and also comprising a low pass filter 208, is to be electrically connected this digital-analog convertor 207, quantizes noise in order to the high frequency that will reduce this analog signal.
In Application Example of the present invention, the raising frequency multiplying power of this second sampling frequency converter 202 is the power values for two.The raising frequency multiplying power of the 3rd sampling frequency converter 204 is non integer value.With f
1=48KHz, f
2=50KHz is an example, and the 3rd sampling frequency converter 204 is that the conversion of the one 1 bit digital stream is output as this three digital signal, and sampling frequency is by f
4=128f
2Be converted to f
3=128f
1, its raising frequency multiplying power is f
1/ f
2=0.96.
Seeing also Fig. 7, is to be Another Application embodiment of the present invention, and as shown in Figure 7, a kind of digital-to-analog/analog-digital conversion equipment comprises a digital-analog converter and an analog-digital conversion equipment.Because this analog-digital conversion equipment comprises a Delta-Sigma analog-digital conversion 220 and a sampling frequency converter 221, these Delta-Sigma analogue-to-digital converters 220 have the characteristic of a noise shaping, its output signal is a bit digital signal, this bit digital signal is input to this sampling frequency converter 204, also can reaches and change out sampling frequency arbitrarily.Comprehensively above-mentioned, the invention provides a kind of sampling frequency converter that can produce any sampling frequency, this sampling frequency converter has a Delta-Sigma modulator, make the input signal of different sampling frequencies, via technology of the present invention, can easily the digital signal of different sampling frequencies be changed out required sampling frequency, and then directly addition, with the disappearance of solution prior art, and then realize research and development purpose of the present invention.Therefore use technology of the present invention, help in response to the processing procedure progress trend of digital circuit area downsizing.The disappearance of avoiding prior art need use the plurality analog-to-digital converter to be caused.
Claims (10)
1. a sampling frequency conversion equipment is characterized in that, comprises:
One noise reshaper receives a digital input signals, and the conversion of this digital input signals is output as a n bit digital signal after the noise shaping, and wherein this digital input signals has one first sampling frequency; And
One sampling frequency converter is to be electrically connected this noise reshaper, receives this n bit digital signal, and exports a digital output signal, and this digital output signal has one second sampling frequency;
Wherein this first sampling frequency and this second sampling frequency are inequality.
2. device as claimed in claim 1 is characterized in that, the ratio of this first sampling frequency and this second sampling frequency is a non integer value.
3. device as claimed in claim 1 is characterized in that, this n bit digital signal is one 1 bit digital signals.
4. device as claimed in claim 1 is characterized in that, this noise reshaper comprises an increment-summation modulator.
5. device as claimed in claim 1 is characterized in that this sampling frequency converter comprises a read-only memory, and implements frequency inverted with look-up method.
6. digital-analog converter comprises:
One sampling frequency converting unit receives a digital input signals, and exports a digital output signal, and this digital input signals has one first sampling frequency, and this digital output signal has one second sampling frequency, comprising:
One first noise reshaper be to receive this digital input signals, and conversion is output as a n bit digital signal; And
One sampling frequency converter is to be electrically connected this first noise reshaper, receives this n bit digital signal, and exports this digital output signal;
One digital-to-analog converting unit is to receive this digital output signal, and exports an analog signal, comprising:
One second noise reshaper is to receive this digital output signal, and is output as a m bit digital signal; And
One digital-analog convertor is to be electrically connected this second noise reshaper, receives this m bit digital signal, and conversion output one analog signal;
Wherein this first sampling frequency and this second sampling frequency are inequality.
7. device as claimed in claim 6, it is characterized in that, also comprise a digital synthesizer, be to be connected between this sampling frequency converting unit and this digital-to-analog converting unit, one second digital output signal and this digital output signal that will have this second sampling frequency are synthetic, export this digital-to-analog converting unit to.
8. device as claimed in claim 6 is characterized in that, this n bit digital signal is one 1 bit digital signals.
9. device as claimed in claim 6 is characterized in that, this first noise reshaper comprises that an increment-summation modulator or this second noise reshaper comprise a modulator.
10. method of changing sampling frequency comprises:
Receive a digital input signals, this digital input signals has one first sampling frequency;
This digital input signals is carried out the noise shaping, be output as a n bit digital signal; And
This n bit digital signal that receives is carried out the sampling frequency conversion, and export a digital output signal, this digital output signal has one second sampling frequency;
Wherein this first sampling frequency and this second sampling frequency are inequality.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031409717A CN100399703C (en) | 2003-06-09 | 2003-06-09 | Conversion device and method for sampling frequency and uses thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB031409717A CN100399703C (en) | 2003-06-09 | 2003-06-09 | Conversion device and method for sampling frequency and uses thereof |
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| Publication Number | Publication Date |
|---|---|
| CN1567728A true CN1567728A (en) | 2005-01-19 |
| CN100399703C CN100399703C (en) | 2008-07-02 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69428987T2 (en) * | 1994-07-25 | 2002-04-04 | Matsushita Electric Ind Co Ltd | Digital / digital sampling rate converter |
| CN2301013Y (en) * | 1997-06-02 | 1998-12-16 | 周毅 | Digital sound multi-sampling frequency convertor |
| CN1273709A (en) * | 1998-04-27 | 2000-11-15 | 皇家菲利浦电子有限公司 | Sample rate converter using polynomial interpolation |
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Granted publication date: 20080702 |