CN1744441A - Method and device for increasing A/D converter signal noise ratio - Google Patents

Method and device for increasing A/D converter signal noise ratio Download PDF

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Publication number
CN1744441A
CN1744441A CN 200510108034 CN200510108034A CN1744441A CN 1744441 A CN1744441 A CN 1744441A CN 200510108034 CN200510108034 CN 200510108034 CN 200510108034 A CN200510108034 A CN 200510108034A CN 1744441 A CN1744441 A CN 1744441A
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power
pga
converter
gain
signal
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CN 200510108034
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CN100481729C (en
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温小勇
冯宇红
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Vimicro Corp
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Vimicro Corp
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Abstract

The method includes following steps: through programmable gain amplifier, input analog signals are magnified; through A/D converter, amplified analog signal is converted to digital signal outputted; calculating power of digital signal from a certain amount of output data; comparing power of digital signal with power value of target setup in advance; based on result obtained from comparing powers, gain of programmable gain amplifier is adjusted. The invention also discloses device for raising SNR of A/D converter. The device includes PGA, A/D converter, module for calculating output power, power comparison module, and PGA gain control module. The method can reach optimal match between input signal and A/D converter, and raises SNR of A/D converter evidently. The method and device are applicable to circuit of containing A/D converter.

Description

A kind of method and device that improves the A/D converter signal to noise ratio
Technical field
The present invention relates to circuit noise-reducing design field, particularly a kind of method and device that improves the A/D converter signal to noise ratio.
Technical background
For A/D converter, quantization error always exists.If regard quantization error as a kind of additive noise, the A/D converter of one (B+1) position, its signal can be expressed as with dB (decibel) with the ratio of additivity quantizing noise:
SNR = 6.02 B + 10.8 - 10 × log 10 ( X m P x ) ( dB ) .
X wherein mBe the full range value of A/D converter, P xBe the power of input signal.
The method that improves the A/D converter signal to noise ratio in the prior art generally is: over-sampling, filtering, Gain Automatic control etc.Wherein by improving sample frequency and using filter to improve the method for A/D converter signal to noise ratio, its circuit parameter is all fixed, promptly just designed the parameter of sample frequency or filter before the sampling beginning, after the sampling beginning, these parameters can not change.
But after beginning sampling, the amplitude of input signal is constantly to change, and for example signal amplitude may be less than the full range value X of A/D converter sometimes m1/8, sometimes may be greater than X m2/3.In this case, still amplify, just can't make full use of the sampling precision of A/D converter with original multiplication factor for signal much smaller than the full range value of A/D converter.Therefore, if the method for the automatic control of utilization amplifier gain is used less yield value when signal amplitude is big, when small-signal,, just can utilize the precision of A/D converter fully, thereby improve the signal to noise ratio of A/D converter with than big yield value.
Automatic controlling method for gain of the prior art is to compare with setting threshold by the magnitude of voltage that PGA is amplified output, regulates the PGA gain according to comparative result then: the less PGA that then makes of amplitude uses big yield value, and amplitude is more then used less yield value.
But, this method also has weak point: owing to constantly compare with setting voltage value by the PGA amplified voltage value, and regulate the gain of PGA, and the gain of the PGA through overregulating will settle out and always needs the regular hour, will bring extra noise to system like this.
Summary of the invention
At the problems referred to above, purpose of the present invention is exactly when guaranteeing that automatic gain is regulated the useful influence that raising A/D converter signal to noise ratio is brought, and reduces the number of times of PGA gain-adjusted, regulates the too much noise that brings of number of times thereby reduce PGA.
In order to achieve the above object, the present invention proposes a kind of method that improves the A/D converter signal to noise ratio.
A kind of method that improves the A/D converter signal to noise ratio may further comprise the steps:
(a) Shu Ru analog signal is amplified by programmable gain amplifier PGA;
(b) described analog signal through amplification is passed through A/D converter, changes digital signal output into;
(c) calculate the power of exporting digital signal;
(d) power of described output digital signal is compared with predefined target power value;
(e) according to the more resulting result of described power ratio, the gain of described PGA is regulated.
Preferably, the performance number of described output digital signal is approximate by the following method obtains: get the sample data of some from the digital signal of described analog to digital converter output, calculate its root mean square and be the signal power value.
Preferably, the frequency of A/D converter is high more, and then required sample data is many more.
Preferably,
When sample frequency was between 8KHz～12KHz, its required sample number was 256;
When sample frequency was between 16KHz～24KHz, its required sample number was 512;
When sample frequency was between 44KHz～48KHz, its required sample number was 1024.
Preferably, described predefined target power value P 0Computing formula be:
P 0 = X m × 10 - ( 6.02 B + 10.8 - SNR 0 10 ) ,
SNR wherein 0Be the signal to noise ratio that system requirements reaches, B is that the figure place of analog to digital converter subtracts 1 value that obtains, X mFull range value for analog to digital converter.
Preferably, the following situation that comprises is regulated in the gain to PGA described in the step e):
(e1) power of output digital signal then reduces the gain of PGA greater than target power value;
(e2) power of output digital signal then increases the gain of PGA less than target power value;
(e3) power of output digital signal equals target power value, and then the gain of PGA remains unchanged.
Preferably, if the power of the digital signal of output and the absolute difference between the target power then keep the current gain of PGA constant in the permissible error scope.
The invention allows for a kind of device that improves the A/D converter signal to noise ratio, comprising:
PGA is used for amplifying the analog signal of importing with certain gain;
A/D converter is used for the signal after the PGA amplification is carried out analog-to-digital conversion;
Power output is calculated module, is used to calculate the power of the digital signal of A/D converter output;
The power comparison module is used for the power of digital signal of comparison A/D converter output and the size of target power;
The PGA gain adjustment module is used for the result that obtains according to the power comparator, correspondingly regulates the gain of PGA.
Preferably, described power output is calculated module, gets the sample data of some from the digital signal of described analog to digital converter output, calculates its root mean square and is the signal power value.
Preferably, during greater than target power, described PGA gain adjustment module makes the gain of PGA reduce to the result who obtains when described power comparison module, otherwise then increases, if described two performance numbers equate that then the gain of PGA remains unchanged for the power of output digital signal.
Preferably, the result who obtains when described power comparison module is: the power of output digital signal and the absolute difference between the target power then keep the current gain of PGA constant in the permissible error scope.
The method and apparatus of raising A/D converter signal to noise ratio disclosed by the invention, the gain of A/D converter PGA before can be set automatically according to the output signal of A/D converter, avoided simultaneously regulating too continually the additional noise that the gain of PGA brings to system again, can make input signal and A/D converter obtain optimum Match, thus the optimum signal-noise ratio of obtaining.
Description of drawings
Fig. 1 is the flow chart of the inventive method;
Fig. 2 is the theory diagram of apparatus of the present invention.
Embodiment
The method and the device of raising A/D converter signal to noise ratio disclosed in this invention, its core concept is that the power of A/D converter output signal is compared with the predetermined pairing echo signal power of signal to noise ratio, regulate the gain that is connected A/D converter PGA before according to comparative result, make the analog signal and the A/D converter of input a/d converter obtain optimum Match, thus the optimum signal-noise ratio of obtaining.
Fig. 2 is the theory diagram of apparatus of the present invention, comprising:
PGA is used for amplifying the analog signal of importing with certain gain;
A/D converter is used for the signal after the PGA amplification is carried out analog-to-digital conversion;
Power output is calculated module, is used to calculate the power of the digital signal of A/D converter output;
The power comparison module is used for the power of digital signal of comparison A/D converter output and the size of target power;
The PGA gain adjustment module is used for the result that obtains according to the power comparator, correspondingly regulates the gain of PGA.
Fig. 1 is the flow chart of the inventive method, utilizes the method and apparatus disclosed by the invention step that gain is regulated to PGA as follows:
The analog signal of step 1, input is amplified by PGA with certain gain;
The gain of PGA is that able to programme definite, initial yield value can calculate setting by the designer, and gain is afterwards determined by method of the present invention.
In this example, suppose that the initial yield value of setting is 100, then import analog signal A InAmplified 100 times by PGA, be designated as 100 *A In
Step 2, A/D converter are to carrying out analog-to-digital conversion through the analog signal of amplifying;
Analog signal 100 through described PGA amplification *A In, be converted to digital signal output by A/D converter, be designated as D (100 *A In).
The power P of the digital signal of step 3, the output of calculating A/D converter x
Digital signal D (100 from described A/D converter output *A In) the middle partial data that takes out, calculate its signal power.
The quantity of data can be determined according to following principle: the sample frequency of A/D converter is when 8KHz～12KHz, and the quantity of sample data is 256; Sample frequency between 16KHz～24KHz, corresponding sample number can be 512; Sample frequency between 44KHz～48KHz, its corresponding sample number is 1024.Under other sample frequency, the data volume that should choose, based on mentioned above principle, can select the data volume identical with it, perhaps suitably increase or reduce data volume.Sample number value in the mentioned above principle all is the optimum number value that obtains by experiment, can reach the effect of the gain of regulating PGA timely and accurately, certainly in actual applications, also can choose other quantitative values.
Calculate P x, promptly from D (100 *A In) in the root mean square of the sample value of taking out, its computing formula is:
P x = 1 m Σ n = 1 m D n 2 2
Wherein, D nRepresent n sample value, m is a total sample number.
For example, the A/D converter sample frequency is 16K, so according to the principle of above-mentioned selection data volume, and can be at output digital signal D (100 *A In) in choose 512 data, each data are designated as D successively 1, D 2... D 512, then P X = 1 512 Σ n = 1 512 D n 2 2 , Suppose the P as a result that calculates xValue is 1532.
The power P of step 4, output signal xWith predefined target power value P 0Compare;
For a specific A/D converter, its figure place (B+1) and full range value X mBe fixed value.So for the specific SNR of system requirements 0, always can be by the snr computation formula:
SNR = 6.02 B + 10.8 - 10 × log 10 ( X m P x ) ,
The anti-desired value P that releases input signal power 0: P 0 = X m × 10 - ( 6.02 B + 10.8 - SNR 0 10 ) ,
P 0Be that calculated in advance is also preserved, in this example, suppose by known X m, B and SNR 0The P that calculates 0Value be 1600.
The power comparison procedure is as follows:
A) P x＞P 0If the result is for being, a) step in the execution in step five, if the result for not, the comparison step b below then continuing to carry out);
B) P x＜P 0If the result is for being the b in the execution in step five) step, if the result for not, the c in the execution in step five then) step.
Certainly, two the determining step Ps of power ratio in x＞P 0And P x＜P 0Sequencing can change, as long as guarantee P x＞P 0The time, reduce the gain of PGA; P x＜P 0The time, increase the gain of PGA; P x=P 0The time PGA gain constant getting final product.
By the step of front as can be known, P xValue is 1532, P 0Value is 1600, so P x＜P 0
Step 5, regulate the gain of PGA according to comparative result;
For the gain-adjusted of PGA, existing narration need be carried out according to the comparative result of step 4 in step 4, now specifies as follows:
A) P x＜P 0The time, increase the gain of PGA;
B) P x＞P 0The time, reduce the gain of PGA;
C) P x=P 0The time, keep the gain of PGA constant.
Because by step 4 P as can be known x＜P 0So, should increase the gain of PGA in this step.
The initial gain of above-mentioned PGA is 100 times, and the gain after regulating so should be for 101 times, and after adjusting, input signal carries out modulus according to conversion by A/D converter after should being amplified 101 times by PGA again.
Described adjusting program is being carried out always, and in this example, 512 data of the every output of A/D converter will utilize these 512 data approximate calculation to go out performance number P x, with calculated in advance and the P that stores 0Compare, and regulate the yield value of PGA according to comparative result.
Because the analog signal of input may cause the power P that goes out with the dateout approximate calculation constantly all changing xWith P 0Be difficult to the situation that reaches equal.Generally speaking, P XCan level off to P gradually 0, afterwards at P 0Value is done fluctuation by a small margin up and down.
The above only is preferred embodiment of the present invention, and is in order to restriction the present invention, within the spirit and principles in the present invention not all, any modification of being done, is equal to replacement etc., all should be included within protection scope of the present invention.

Claims (11)

1, a kind of method that improves the A/D converter signal to noise ratio may further comprise the steps:
(a) Shu Ru analog signal is amplified by programmable gain amplifier PGA;
(b) described analog signal through amplification is passed through A/D converter, changes digital signal output into;
(c) calculate the power of exporting digital signal;
(d) power of described output digital signal is compared with predefined target power value;
(e) according to the more resulting result of described power ratio, the gain of described PGA is regulated.
2, method according to claim 1, it is characterized in that, the performance number of described output digital signal is approximate by the following method to be obtained: get the sample data of some from the digital signal of described analog to digital converter output, calculate its root mean square and be the signal power value.
3, method according to claim 2 is characterized in that, the frequency of A/D converter is high more, and then required sample data is many more.
4, method according to claim 2 is characterized in that,
When sample frequency was between 8KHz～12KHz, its required sample number was 256;
When sample frequency was between 16KHz～24KHz, its required sample number was 512;
When sample frequency was between 44KHz～48KHz, its required sample number was 1024.
5, method according to claim 1 is characterized in that, described predefined target power value P 0Computing formula be: P 0 = X m × 10 - ( 6.02 B + 10.8 - SNR 0 10 ) ,
SNR wherein 0Be the signal to noise ratio that system requirements reaches, B is that the figure place of analog to digital converter subtracts 1 value that obtains, X mFull range value for analog to digital converter.
6, method according to claim 1 is characterized in that, the following situation that comprises is regulated in the gain to PGA described in the step e):
(e1) power of output digital signal then reduces the gain of PGA greater than target power value;
(e2) power of output digital signal then increases the gain of PGA less than target power value;
(e3) power of output digital signal equals target power value, and then the gain of PGA remains unchanged.
7, method according to claim 1 is characterized in that, if the power of the digital signal of output and the absolute difference between the target power then keep the current gain of PGA constant in the permissible error scope.
8, a kind of device that improves the A/D converter signal to noise ratio comprises:
PGA is used for amplifying the analog signal of importing with certain gain;
A/D converter is used for the signal after the PGA amplification is carried out analog-to-digital conversion;
Power output is calculated module, is used to calculate the power of the digital signal of A/D converter output;
The power comparison module is used for the power of digital signal of comparison A/D converter output and the size of target power;
The PGA gain adjustment module is used for the result that obtains according to the power comparator, correspondingly regulates the gain of PGA.
9, device according to claim 8 is characterized in that, described power output is calculated module, gets the sample data of some from the digital signal of described analog to digital converter output, calculates its root mean square and is the signal power value.
10, according to Claim 8 or 9 described devices, it is characterized in that, the result who obtains when described power comparison module is for the power of output digital signal during greater than target power, described PGA gain adjustment module makes the gain of PGA reduce, otherwise then increase, if described two performance numbers equate that then the gain of PGA remains unchanged.
11, according to Claim 8 or 9 described methods, it is characterized in that the result who obtains when described power comparison module is: the power of output digital signal and the absolute difference between the target power then keep the current gain of PGA constant in the permissible error scope.
CNB2005101080343A 2005-10-09 2005-10-09 Method and device for increasing A/D converter signal noise ratio Expired - Fee Related CN100481729C (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101873453A (en) * 2010-06-23 2010-10-27 西安交通大学 Automatic gain controller of composite video signal and control method thereof
CN101931412A (en) * 2009-06-19 2010-12-29 联发科技股份有限公司 Gain control method and electronic apparatus
CN102590828A (en) * 2012-02-15 2012-07-18 北京中科贝银科技有限公司 Method for reducing quantized noise of ADC (analog to digital converter) in satellite navigation receiver
CN101821597B (en) * 2007-10-12 2012-11-07 罗伯特·博世有限公司 Knock detection system and method for amplifier control for knock signal
CN106972837A (en) * 2017-02-21 2017-07-21 和芯星通科技(北京)有限公司 A kind of method and device for realizing gain control
CN108337460A (en) * 2018-04-23 2018-07-27 昆山锐芯微电子有限公司 The reading circuit of imaging sensor
CN115065370A (en) * 2022-03-31 2022-09-16 北京全路通信信号研究设计院集团有限公司 Gain control method, device, equipment and medium

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101821597B (en) * 2007-10-12 2012-11-07 罗伯特·博世有限公司 Knock detection system and method for amplifier control for knock signal
CN101931412A (en) * 2009-06-19 2010-12-29 联发科技股份有限公司 Gain control method and electronic apparatus
CN101873453A (en) * 2010-06-23 2010-10-27 西安交通大学 Automatic gain controller of composite video signal and control method thereof
CN102590828A (en) * 2012-02-15 2012-07-18 北京中科贝银科技有限公司 Method for reducing quantized noise of ADC (analog to digital converter) in satellite navigation receiver
CN106972837A (en) * 2017-02-21 2017-07-21 和芯星通科技(北京)有限公司 A kind of method and device for realizing gain control
CN106972837B (en) * 2017-02-21 2019-07-30 和芯星通科技(北京)有限公司 A kind of method and device for realizing gain control
CN108337460A (en) * 2018-04-23 2018-07-27 昆山锐芯微电子有限公司 The reading circuit of imaging sensor
CN108337460B (en) * 2018-04-23 2020-12-08 锐芯微电子股份有限公司 Readout circuit of image sensor
CN115065370A (en) * 2022-03-31 2022-09-16 北京全路通信信号研究设计院集团有限公司 Gain control method, device, equipment and medium
CN115065370B (en) * 2022-03-31 2024-04-02 北京全路通信信号研究设计院集团有限公司 Gain control method, device, equipment and medium

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