CN101093624A - Method for implementing diversiform A-D /D-A conversion based on experimental platform - Google Patents
Method for implementing diversiform A-D /D-A conversion based on experimental platform Download PDFInfo
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Abstract
A method for realizing multi-type AD/DA conversion includes realizing ideal-sampling on inputted analog signal by an accurate AD chip, using a FPGA chip to realize quantization and coding of signal to finalize A/D conversion, using D/A conversion as inverse process of A/D conversion, carrying out decoding on inputted digital signals in sequence, making inverse quantization and finally restoring inputted digital signal to be analog signal.
Description
Technical field
The invention belongs to the communications electronics technical field, relate to the conversion of simulating signal and digital signal, be specifically related to a kind of method that realizes multiple modulus/digital-to-analog conversion based on experiment porch.
Background technology
Antijamming capability is strong, mistake is controlled because of having for digital communication system, be easy to developing direction and main flow that many outstanding advantages such as signal Processing day by day become communication, but natural a lot of information all is simulating signal, for example speech, image etc., so modulus/digital-to-analog conversion seems particularly important.So-called analog to digital conversion changes into digital signal with simulating signal exactly, and typical method divides three steps to carry out: sampling, to the operation that simulating signal is carried out on time domain, discretize on the deadline; Quantize, the sample value of simulating signal is quantized, make amplitude become limited kind of value; Encode, replace the value of limited kind with one group of binary digital code.And digital to analog conversion is the inverse process of analog to digital conversion, and it is deciphered and processing such as low-pass filtering the digital signal that receives, and recovers original analog signal.
Along with the fast development of the communication technology, be to the general requirement of Principles of Modern Communication experimental system: 1, multifunctionality, promptly on same experimental system, platform or device, can carry out the communication theory experiment of multiple different levels and different modes or method; But 2, reproducibility and novelty, be in the communication theory experiment overall process, the experimenter is on system-level and module level level, not only can select to be provided with existing communication mode or method on the experimental system voluntarily, reappear previous research, the checking relative theory also can design on experimental system voluntarily, starts new communication function; But 3, have and communication theory, principle corresponding illustrative and observability function fully, such as one of the typical way of analog signal digital pulse code modulation (PCM).Three steps in its digitized process---sampling, quantification, coding, all systematic observation is arrived by experiment.
Figure 1 shows that the communication theory experiment system functional-block diagram, it respectively forms the module subsystem, except that modulus/digital to analog conversion part (being source encoder/code translator among the figure), all relatively easily be developed into satisfy above-mentioned requirements respectively test subsystem, but most basic part---up to the present modulus/D/A converter module but also fails to accomplish to satisfy above-mentioned requirements.With the existing Principle of Communication teaching experiment system that comes into operation is example, as close the SEED-DTK_FPD experimental box that the crowd reaches company, a high performance stereo audio Codec chip TLV320AIC23B that releases with TI experimentizes, but the analog to digital conversion of TLV320AIC23B (ADCs) and digital-to-analog conversion (DACs) component height concentrate on chip internal, the user can only be to sampling rate, sampling length and sampling resolution carry out some limited selections, can't observe the waveform of each link of analog signal digital process, the quantizing noise that the degree of accuracy that produces as Different Results and different quantification manner because of sampling rate change generation is different etc., and the user can not participate in the design voluntarily of each step in the analog signal digital process fully.The JH5001A type communication theory experiment case of prompt for another example brightness company, be only limited to voice signal, with PCM is example, this experimental system only can be verified sampling theorem and PCM code and decoding principle, for how the statistical property difference of basis signal is chosen optimum quantization method, and sampling, quantification, the waveform in each stage of encoding etc. that the difference that more different quantization method produced quantizes signal to noise ratio (S/N ratio) and observes PCM can't experimentize, and can not design the checking that experimentizes of new modulus/digital-analog convertion method voluntarily.In addition, application number is 200520022910.6 open communication principle experiment porch, its opening only limits to modulation, the Error-correcting Encoding and Decoding part, and modulus, the digital to analog conversion subsystem still simply adopts common modulus, the digital-to-analogue integrated chip is realized, so modulus, the digital to analog conversion method is relatively-stationary, and its platform structure complexity is huge, each step in the transfer process is difficult for cutting apart, can not freely control and change relevant parameters experimentizes, thereby can't be to modulus, each step of digital to analog conversion system is carried out tracing observation or design, has reduced the experiment effect of experimental system.
Why the modulus of existing communication theory experiment system/digital-to-analog conversion subsystem can not satisfy the requirement of above-mentioned communication experiment teaching to experimental system, be simply to constitute realization by modulus/digital-to-analogue integrated chip because of its modulus/digital-to-analog conversion part, and existing modulus/digital to analog conversion chip such as MAX132, MAX1400, though can realize the transformation from the simulating signal to the digital signal and from the digital signal to the simulating signal respectively, but a kind of modulus of the realization that can only fix/digital to analog conversion method, as PCM or DM, and two or more analogue-digital converting method can not be realized on chip piece, and can not select different quantization methods according to the information characteristics of signal, or select different coded systems neatly, the experiential function illustrative of the modulus of the communication theory experiment system that it constituted/digital to analog conversion subsystem is imperfect, design freedom is little, and experiment effect is not good enough.
Summary of the invention
The technical problem to be solved in the present invention is: existing modulus/digital-to-analogue experimental system is open not enough, uses degree of freedom little, and illustrative is imperfect.A kind of method that realizes multiple modulus/digital-to-analog conversion based on experiment porch is provided, the use device is few, can in same system, realize multiple modulus/digital-to-analog conversion mode, can freely select sampling rate, quantization algorithm and coded system, and can pass through oscillograph, spectrum analyzer observation conversion process.
Technical scheme of the present invention is: the method that realizes multiple modulus/digital-to-analog conversion based on experiment porch, comprise analog-to-digital conversion module and D/A converter module, analog-to-digital conversion module earlier with a high-precision A chip to the simulating signal of the importing sampling of realizing ideal, realize the quantification and the coding of signal again with a fpga chip or CPLD chip, finish analog to digital conversion, wherein, the clock signal that changes the high-precision A chip obtains different sampling rates, fpga chip or CPLD chip programming are realized different quantification and coding method, can reach the analog to digital conversion of various modes thus, digital-to-analog conversion is the inverse process of analog to digital conversion correspondence, successively the digital signal of input is deciphered, re-quantization reverts to simulating signal at last, and all chips of analog-to-digital conversion module and D/A converter module use unified clock signal.
Simulating signal of the present invention carries out filtering noise with wave filter before the analog to digital conversion, number is touched conversion back low-pass filtering and is leached original analog signal, download to fpga chip or CPLD chip by single-chip microcomputer or computer programming, single-chip microcomputer or computing machine also provide and control the clock signal of all chips.Signal behind sampling, quantification, decoding, the re-quantization is imported a digital-to-analogue respectively and is transformed chip, as the test point among Fig. 2 and Fig. 31, and test point 2, test point 3 and test point 4 are observed waveform or the frequency spectrum that chip is exported with oscillograph or spectrum analyzer.
The present invention is by the sampling of realizing ideal of high-precision A converter, for after the FPGA/CPLD chip realize that various quantifications, coding method provide the foundation.The principle of the invention as shown in Figure 4, simulating signal, common single frequency sinusoidal ripple signal, voice signal and the picture signal etc. of comprising, at first pass through analog filter, filter unnecessary noise, then enter analog-to-digital conversion module, with single-chip microcomputer or computer control clock signal input terminal, change sampling rate by programming; The sample program that provides with single-chip microcomputer or downloaded written program or system realizes different digital form or quantization method and different coding methods in the FPGA/CPLD chip; Observe the time domain specification and the frequency domain characteristic of sampling or quantification back signal with dual trace oscilloscope and/or spectrum analyzer.Digital to analog conversion is the inverse process of corresponding analog to digital conversion, quantification, decoded mode according to the analog to digital conversion use, with the FPGA/CPLD chip decipher accordingly, re-quantization, recover simulating signal by high precision DA chip again, and with the noise that is subjected in the wave filter elimination signals transmission, the time domain specification of signal and the also available dual trace oscilloscope of frequency domain characteristic and/or spectrum analyzer are observed behind decoding, the re-quantization.
For making total system easy to use, also design a close friend's man-machine interface, whole experimental system is by Single-chip Controlling, and by computing machine with the mode of man-machine interface demonstrate, design, the experiment of programming or property of participation.
The invention has the beneficial effects as follows: by the new combination on high-precision A chip and the field programmable gate function function, can realize known all moduluses/digital-to-analog conversion mode, secondly, the present invention can be to sampling, the quantification and three processes of encoding are independently programmed respectively, the user can freely change sampling rate as required, quantified precision and coded system, and can be by dual trace oscilloscope and frequency spectrograph observation experiment effect, provide one to be convenient to go deep into observational learning, the flexible teaching experiment system that uses, have excellent programmability and observability, in addition, the present invention is open completely makes it also can be used for the development research of new modulus/digital-to-analog conversion mode.
Description of drawings
Fig. 1 is the communication theory experiment system functional-block diagram.
Fig. 2 is an analog-to-digital conversion module synoptic diagram of the present invention.
Fig. 3 is a D/A converter module synoptic diagram of the present invention.
Fig. 4 is a principle of the invention synoptic diagram.
Fig. 5 is concrete hardware synoptic diagram of implementing of the present invention.
Fig. 6 is sampling back signal and two kinds of different quantized result in the embodiment of the invention PCM analog to digital conversion.
Fig. 7 is the DPCM system principle diagram.
Fig. 8 is an oscillogram behind the signal sampling in the embodiment of the invention DPCM analog to digital conversion.
Fig. 9 is an oscillogram after the signal quantization in the embodiment of the invention DPCM analog to digital conversion.
The original signal of Figure 10 for recovering after the embodiment of the invention DPCM digital-to-analog conversion.
Figure 11 is the DM system principle diagram.
Figure 12 is an oscillogram behind the signal sampling in the embodiment of the invention DM analog to digital conversion.
Figure 13 is an oscillogram after the signal quantization in the embodiment of the invention DM analog to digital conversion.
Embodiment
The present invention can realize multiple modulus/digital-to-analog conversion mode, wherein, can be existing ripe modulus/digital-to-analog conversion mode, also can be used as and realizes or test the experiment porch of new modulus/digital-analog convertion method.Fig. 5 is a concrete hardware synoptic diagram of implementing of the present invention.Wherein the high-precision A conversion chip is selected the ADI AD7678 of company, and its conversion accuracy is 18, and high precision DA chip is selected isonomic AD760, and its conversion accuracy is 18; Fpga chip is selected the EP2C8 of altera corp; Common DA chip is selected typical DAC 0832; Master controller is selected the 80C51 series monolithic, and observation instrument is TDS2012 dual trace oscilloscope, E4438C frequency spectrograph.Below in conjunction with experimental system shown in Figure 5, with pulse code modulation (pcm), differential pulse coding modulation (DPCM) and delta modulation (DM) conversion method are example, illustrate the function and the effect of this system respectively.
The PCM conversion regime, import one section analog voice signal m (t), its maximal value | m (t) |＜0.2V, frequency (300,3400Hz):
1, sampling: with the sampling of realizing ideal of 18 high-precision A converters, promptly the pulsewidth τ of the pulse after the sampling goes to zero, sampling rate 16kHz, with high precision multidigit binary digital signal represent to sample the back simulating signal, because the big I of sampling rate is by switch or computer program control, observe sample under the various the sampling rates afterwards time domain waveform or the frequency-domain waveform of signal by oscillograph or frequency spectrograph, also can understand sampling theorem intuitively;
2, quantize: the signal of getting unlimited multiple probable value after the sampling is converted to limited kind of possible values by quantizing tolerance.Fig. 6 is the comparison of sampling back signal and two kinds of different quantized result, and wherein quantization method 1 is 8 bit uniform quantizers; Quantization method 2 is 4 bit uniform quantizers.The user can oneself design quantizer on computers, according to the analysis of computing machine to input signal statistical nature or amplitude characteristic, select or design the quantification progression of quantizer, quantize step and quantized interval, programming also downloads to program in the FPGA in the system, realize the quantizer of different quantified precisions or performance, time domain and frequency-domain waveform after quantizing by dual trace oscilloscope and frequency spectrograph observation;
3, coding: the signal level value after quantizing is mapped as the scale-of-two code character, finishes the conversion of simulating signal to digital signal.The user is the programmed scrambler on computers, and the program that writes is downloaded to the fpga chip of experiment porch, realizes the corresponding encoded function.The general binary code that adopts in PCM.Binary code type commonly used has three kinds: natural binary code, folding binary code and gray binary code.As shown in Figure 6, sampling back signal is example through quantization method 1 with the top ten, adopts the scale-of-two code character of natural binary coding to be:
The 1st: 01111010
The 2nd: 01111000
The 3rd: 01110110
The 4th: 01110111
The 5th: 01111000
The 6th: 01111010
The 7th: 01111000
The 8th: 01110110
The 9th: 01110111
The 10th: 01111000
Coded system can adopt the binary code of equal length that the signal sample after quantizing is encoded, and also can adopt the variable length binary code, finishes coding as coding methods such as Huffman (Huffman), Lempel-Ziv.
Digital-to-analog conversion partly is the inverse process corresponding with analog to digital conversion, and it is deciphered and the re-quantization process is also programmable and observability.The user can observe on principle level step by step, the operation of study and experience type, for example to the study of sampling theorem with sharpen understanding; On the other hand, also can carry out the operation of research and development formula, for example write new quantization algorithm program and download in the FPGA/CPLD chip, verify the quality of the quantization method that the user designs by the effect of degree of distortion demonstration, analog waveform demonstration and loudspeaker.
DPCM is converted to a kind of D conversion method with differential coding, and Fig. 7 is the functional-block diagram of DPCM, x
nRepresent current information source sample value, the input of fallout predictor
Represent reconstruction signal.Fallout predictor is output as
Difference
As quantizer input, e
QnBe quantizer output, each the predicated error e after the quantification
QnBe encoded into sequence of binary digits, be sent to the destination by channel.This error e
QnBe added to local predicted value simultaneously
And obtain
At receiving end the fallout predictor identical with transmitting terminal is housed, its output
With e
QnAddition produces
Signal
Being the pumping signal of desired fallout predictor, also is the reconstruction signal of desired demoder output.Present embodiment is a simulation signal generator with one section voice signal, after the 16KHz sampling, its waveform as shown in Figure 8, write quantification program and coded program according to the theory diagram of DPCM, adopt 4 level to quantize, quantize the back waveform as shown in Figure 9, the last speech reconstructing signal of being exported by demoder as shown in figure 10.
Delta modulation (DM) is a kind of D conversion method with differential coding, only with the relative size of an adjacent sample value of coded representation, thereby reflects the variation tendency of sampling time waveform.Figure 11 is the functional-block diagram of DM, concrete transfer process is: sampling realizes with high-precision AD converter part, sampling rate is used switch or programming Control by the user, can arbitrarily increase or reduce sampling rate, observe under the various sampling rate situations time domain waveform or the frequency-domain waveform of sampled signal by oscillograph or frequency spectrograph, the Changing Pattern of the difference reflection simulating signal of adjacent sample value, adjacent sample value difference is not to be exactly less than zero greater than zero, use respectively " 1 " sign indicating number and the adjacent sample value difference of " 0 " sign indicating number representative greater than zero-sum less than zero, so just finished and quantized and coding.Corresponding with it, decode procedure promptly is according to a corresponding respectively quantization step and the quantization step that descends of rising in " 1 " of receiving, " 0 ", restores original voice signal by wave filter then.The present embodiment sampling rate is 16kHz, and Figure 12 is an oscillogram behind the analog signal sampling, and Figure 13 is oscillogram after the signal quantization, and the user can compare the confirmatory experiment effect to the output waveform observation analysis of quantizer and with theoretical waveform.
Experimental system of the present invention not only can realize existing modulus/digital-analog convertion method, can also be as exploitation, innovation, the research experiment platform of the new modulus/digital-analog convertion method of design.
Claims (9)
1, realize the method for multiple modulus/digital-to-analog conversion based on experiment porch, it is characterized in that analog to digital conversion earlier with a high-precision A chip to the simulating signal of the importing sampling of realizing ideal, realize the quantification and the coding of signal again with a fpga chip or CPLD chip, finish analog to digital conversion, the clock signal that changes the high-precision A chip obtains different sampling rates, fpga chip or CPLD chip programming are realized different quantification and coding method, can reach the analog to digital conversion of various modes thus, digital-to-analog conversion is the inverse process of analog to digital conversion correspondence, successively the digital signal of input is deciphered, re-quantization, revert to simulating signal at last, all chips of analog to digital conversion and digital-to-analog conversion use unified clock signal.
2, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 1 is characterized in that simulating signal carries out filtering noise with wave filter before the analog to digital conversion, and number is touched conversion back low-pass filtering and leached original analog signal.
3, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 1 and 2 is characterized in that downloading to fpga chip or CPLD chip by single-chip microcomputer or computer programming, and single-chip microcomputer or computing machine also provide and control the clock signal of all chips.
4, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 1 and 2, it is characterized in that sampling, quantize, the signal after the decoding, re-quantization imports a digital-to-analogue respectively and transforms chip, observes the waveform or the frequency spectrum of chip output with oscillograph or spectrum analyzer.
5, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 3, it is characterized in that sampling, quantize, the signal after the decoding, re-quantization imports a digital-to-analogue respectively and transforms chip, observes the waveform or the frequency spectrum of chip output with oscillograph or spectrum analyzer.
6, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 1 and 2 is characterized in that high-precision adc is 18 analog to digital converters, and high precision digital-to-analog converter is 18 figure place weighted-voltage D/A converters.
7, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 3 is characterized in that high-precision adc is 18 analog to digital converters, and high precision digital-to-analog converter is 18 figure place weighted-voltage D/A converters.
8, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 4 is characterized in that high-precision adc is 18 analog to digital converters, and high precision digital-to-analog converter is 18 figure place weighted-voltage D/A converters.
9, the method for the multiple modulus/digital-to-analog conversion of realization according to claim 5 is characterized in that high-precision adc is 18 analog to digital converters, and high precision digital-to-analog converter is 18 figure place weighted-voltage D/A converters.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105827241A (en) * | 2016-03-17 | 2016-08-03 | 苏州易瑞得电子科技有限公司 | Intelligent signal control method and controller |
| CN107251439A (en) * | 2015-02-11 | 2017-10-13 | 三菱电机株式会社 | Method and AMC controllers for adaptive modulation and coding AMC |
| CN108447364A (en) * | 2018-05-22 | 2018-08-24 | 同济大学 | A kind of portable multi-function time domain sampling theorem experimental provision |
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2007
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107251439A (en) * | 2015-02-11 | 2017-10-13 | 三菱电机株式会社 | Method and AMC controllers for adaptive modulation and coding AMC |
| CN107251439B (en) * | 2015-02-11 | 2021-01-05 | 三菱电机株式会社 | Method and AMC controller for adaptive modulation and coding of AMC |
| CN105827241A (en) * | 2016-03-17 | 2016-08-03 | 苏州易瑞得电子科技有限公司 | Intelligent signal control method and controller |
| CN108447364A (en) * | 2018-05-22 | 2018-08-24 | 同济大学 | A kind of portable multi-function time domain sampling theorem experimental provision |
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