CN103490740A - Automatic gain control device and method thereof - Google Patents

Abstract

The invention discloses an automatic gain control device and a method thereof. The automatic gain control device comprises a simulation VGA, an ADC, a downsampling unit, a digital VGA, a simulation AGC controller, a digital AGC controller and a power calculating unit, wherein the simulation VGA, the ADC, the downsampling unit and the digital VGA are sequentially connected, the simulation AGC controller is connected with the simulation VGA and the digital AGC controller, the digital AGC controller is connected with the digital VGA, and the power calculating unit is connected with the downsampling unit, the simulation AGC controller and the digital AGC controller. The method comprises the steps of downsampling analog-digital conversion output signals, calculating the power average value for downsampled data, calculating the gain coefficient of the simulation VGA in a logarithm domain based on the power average value, using the gain coefficient of the simulation VGA to gain the power average value, and calculating the amplitude gain coefficient based on the gained power average value. The automatic gain control device can reduce downsampling operation amount and signal distortion, widens an automatic gain dynamic range, enables coefficient updating time to be controllable, solves the problem of loop convergence time and is small in resource consumption of hardware.

Description

A kind of automatic gain control equipment and method thereof

Technical field

The present invention relates to the communications field, be specifically related to a kind of automatic gain control equipment and method thereof.

Background technology

In general communication system, usually use automatic gain to control the amplitude that (AGC, Automatic Gain Control) carrys out the self adaptation input signal, facilitate the subsequent treatment of data.In the AGC system, by regulating analogue variable gain amplifier (AVGA, Analog Variable Gain Amplifier) or digital variable gain amplifier (DVGA, Digital Variable Gain Amplifier), realize the signal gain self adaptation.AVGA acts on the ADC(analog to digital converter) input, it is stabilized near a desired value, avoid the too small or saturated phenomenon of digital signal resolution after ADC changes as far as possible, DVGA acts on the input of digital processing, to guarantee that output signal meets the needs of follow-up digital processing, as synchronous, demodulation etc.

In prior art; the typical structure of realizing the automatic gain control of AVGA and DVGA comprises VGA(VGA; Variable Gain Amplifier), error controller and loop filter, error controller is often realized based on peak detector, square root controller or mean absolute error controller.Adopt the AGC system of peak detector without multiplying, operand is little, and shortcoming is poor anti jamming capability, particularly large impulse disturbances; Square root control device is simple in structure, good stability, but operand is slightly large; The mean absolute error controller algorithm is relatively simple, but stability is slightly poor.Loop filter is an integral process, the convergence rate of choosing the direct AGC of impact and the gain accuracy of its coefficient.In addition, in order to increase the adjusting range of gain, yield value converts to usually take the 10 LOG values that are the end, but has increased the complexity of computing simultaneously.

In addition, in the multi-signal treatment system, the output speed of analog to digital converter (ADC) is often higher, needs down-sampled processing.Down-sampled method more commonly used is to adopt comb filter (CIC, Cascaded Integrator Comb), but it is only suitable for the situation of sample rate much larger than signal bandwidth, and the improper low power of doing extracts; Half-band filter (HB, Half band) is for 2 times of extractions, has a coefficient few, and the advantage that operand is little, but its wide transition band, be not suitable for doing afterbody and extract; General FIR(Finite Impulse Response, have limit for length's unit impulse response) extraction that filter is realized, can meet the needs that pass band damping is little, stopband attenuation is large, transition band is narrow, but exponent number is often very high, operand is large, and complexity is high.

In sum, the applicant is devoted to solve low power is down-sampled and AGC controls performance and the problem of complexity.

Summary of the invention

The object of the invention is to overcome the defect of prior art and a kind of automatic gain control equipment and method thereof are provided, can reduce down-sampled operand and distorted signals, can also enlarge the automatic gain dynamic range, make the coefficient update time controlled, and there do not is the problem of loop convergence time, simple in structure, hardware resource consumption is little.

The technical scheme that realizes above-mentioned purpose is:

A kind of automatic gain control equipment, comprise simulation VGA, ADC, digital VGA, down-sampled unit, power calculation unit, simulation AGC controller and digital AGC device; Described simulation VGA, ADC, down-sampled unit are connected successively with digital VGA; Described power calculation unit connects respectively down-sampled unit, simulation AGC controller and digital AGC device; Described simulation AGC controller is connecting analog VGA and digital AGC device respectively; Described digital AGC device connects digital VGA, wherein:

Down-sampled module, carry out down-sampledly for the output signal to described ADC, after reducing data rate, export to described power calculation unit and digital VGA;

Power calculation unit, for the rated output mean value in a regular length of the data to after down-sampled, pass to described simulation AGC controller and digital AGC device by the power average obtained;

Simulation AGC controller, according to the gain coefficient of described power average and the described simulation of the first preset reference power calculation VGA, and pass to described simulation VGA and digital AGC device;

The digital AGC device, utilize the gain coefficient of the described simulation VGA described power average that gains, and then according to power average and the second preset reference power calculation amplitude gain coefficient after gain, feedovers to described digital VGA.

In above-mentioned automatic gain control equipment, described down-sampled module comprises several half-band filters and a FIR filter of cascade successively, wherein:

Carry out the extraction of 2 times after each half-band filter;

The FIR filter carries out the afterbody extraction.

In above-mentioned automatic gain control equipment, described power calculation unit comprises squarer, accumulator sum counter, wherein:

Squarer, squared for the output to described down-sampled unit, the square value of obtaining is passed to described accumulator;

Accumulator, cumulative for the square value by receiving, after being averaging, the cumulative sum obtained is transferred to described simulation AGC controller and digital AGC device;

Counter, for the length of control inputs signal, realize that the AGC coefficient update time is controlled.

In above-mentioned automatic gain control equipment, described simulation AGC controller comprises Logarithmic calculation unit, subtracter, adder, register and analog gain coefficient elements, wherein:

The Logarithmic calculation unit, change into the LOG value by described power average;

Subtracter, the difference of calculating LOG value and the first preset reference power Ref_power1, obtain the current power difference, and give described adder;

Adder, for calculate current power difference and last yield value and, obtain current gain value, and give described register and analog gain coefficient elements yield value;

Register, for storing current gain value;

The analog gain coefficient elements, for current gain value is encoded into to gain coefficient by gain step size, feed back to described simulation VGA.

In above-mentioned automatic gain control equipment, described Logarithmic calculation unit converts described power average to take the 10 LOG values that are the end to, and at first power average P converts to and take the 2 LOG values that are the end by shift operation, based on relationship:

$\log 10\left(P\right)=\frac{\log 2\left(p\right)}{\log 2\left(10\right)}$

Then be multiplied by a constant, convert to and take the 10 LOG values that are the end.

In above-mentioned automatic gain control equipment, described digital AGC device comprises multiplier, divider and amplitude gain coefficient elements, wherein:

Multiplier, multiply each other gain coefficient and the power average of simulation VGA, the gain power average;

Divider, the power average after calculated gains and the ratio of the second preset reference power, obtain power gain factor;

The amplitude gain coefficient elements, for power gain factor being converted to the amplitude gain coefficient, feedforward is to described digital VGA.

In above-mentioned automatic gain control equipment, described amplitude gain coefficient, be the extraction of square root of power gain factor.

In above-mentioned automatic gain control equipment, can first calculate the gain coefficient of simulation VGA, then calculate the amplitude gain coefficient; Also can before the gain coefficient of stable simulation VGA, enable the calculating of amplitude gain coefficient, realize that AGC is controlled stabilization time by the adjustment time of controlling two-stage AGC.

The present invention's two auto gain control method, comprise the following steps:

Step S1, realize the convergent-divergent of analog input signal;

Step S2, be converted to digital signal by the analog input signal after convergent-divergent;

Step S3, carry out down-sampled to digital signal;

Step S4, calculate the power average of data in a regular length after down-sampled;

Step S5, change into the LOG value to the power average, and then the difference with the first preset reference power in the calculating of LOG territory, finally be encoded into the gain coefficient of simulating VGA;

Step S6, utilize the gain coefficient gain power average of described simulation VGA;

Step S7, the power average after calculated gains and the ratio of the second preset reference power, obtain power gain factor, and power gain factor converted to the amplitude gain coefficient;

Step S8, be multiplied by the amplitude gain coefficient digital signal of down-sampled rear output, realizes convergent-divergent.

In above-mentioned auto gain control method, described step S3 comprises: at first, digital signal is through several half-band filters, carries out the extraction of 2 times after each half-band filter, then, through a FIR filter, carries out the afterbody extraction.

In above-mentioned auto gain control method, in described step S5, described power average is transformed into the LOG value, refers to: at first by shift operation, convert to and take the 2 LOG values that are the end, based on relationship:

$\log 10\left(P\right)=\frac{\log 2\left(p\right)}{\log 2\left(10\right)},$

Wherein, P is the power average;

Then be multiplied by a constant, obtain take the 10 LOG values that are the end.

In above-mentioned auto gain control method, described amplitude gain coefficient, be the extraction of square root of power gain factor.

The invention has the beneficial effects as follows: the present invention utilizes the cascade of half-band filter and FIR filter to realize that low power is down-sampled, and operand is little, and spectral characteristic is good; Simultaneously, data based on after down-sampled are calculated average power can reduce operand, only by a power calculation unit, control the gain coefficient of two-stage AGC, and stablize respectively two-stage AGC within the controlled time, with existing scheme, compare, two-stage AGC has enlarged the dynamic gain scope, coefficient update time controlled, the time of stablizing the AGC coefficient is also controlled, do not have the problem of loop convergence time, in addition, the method transformed in the middle of using makes without specific algorithm process logarithm, reduced complexity, hardware configuration is simple.

The accompanying drawing explanation

Fig. 1 is the frame structure schematic diagram;

The structure chart that Fig. 2 is automatic gain control equipment of the present invention;

The structure chart that Fig. 3 is down-sampled unit in the present invention;

The structure chart that Fig. 4 is simulation AGC controller in the present invention;

The structure chart that Fig. 5 is digital AGC device in the present invention;

The flow chart of Fig. 6 auto gain control method of the present invention;

The AGC coefficient update schematic flow sheet that Fig. 7 provides for the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

The present invention can be used to plurality of communication systems, as audio-video-frequency broadcast, WLAN (wireless local area network), cellular system, power line carrier system etc.; Can be used to multicarrier system, also can be used for single-carrier system.Below to the present invention is based on OFDM(Orthogonal Frequency Division Multiplexing, OFDM) embodiment of receiving system.Fig. 1 is the frame structure schematic diagram that the present embodiment provides, and several OFDM symbols, consists of.

Refer to Fig. 2, one of the present invention's automatic gain control equipment comprises: simulation VGA10, ADC(analog to digital converter) 11, down-sampled unit 12, power calculation unit 13, simulation AGC controller 14, digital AGC device 15 and digital VGA16; Simulation VGA10, ADC11, down-sampled unit 12 are connected successively with digital VGA16; Power calculation unit 13 connects respectively down-sampled unit 12, simulation AGC controller 14 and digital AGC device 15; Simulation AGC controller 14 is connecting analog VGA10 and digital AGC device 15 respectively; Digital AGC device 15 connects digital VGA16, wherein:

Simulation VGA10 receives analog signal, according to gain coefficient, realizes zooming in or out of analog signal; Simulation VGA10 is realized by analog circuit, Digital Circuit Control;

ADC11 converts digital signal to for the signal that will simulate VGA10 output, range and the precision scale signal of simulation VGA10 based on ADC11;

The needs that down-sampled unit 12 is processed according to follow-up signal, carry out down-sampledly to the output signal of ADC11, after reducing data rate, export to power calculation unit 13 and digital VGA16; As shown in Figure 3, down-sampled unit 12 comprises several half-band filters 121 and a FIR filter 122 of cascade successively, wherein: each half-band filter 121 carries out the extraction of 2 times, and FIR filter 122 carries out the afterbody extraction, and down-sampled general times is N=2^ (p) ^*q, N can not be too large, wherein, the number that p is half-band filter 121, the extracting multiple that q is FIR filter 122.FIR filter 122 makes the signal of down-sampled rear output meet passband, stopband attenuation and transition band requirement, and it has multiple implementation, how based on THE DESIGN OF WINDOW FUNCTION;

In the present embodiment, down-sampled multiple N=4, by a HB(half band) filter 121 and a FIR filter 122 form, and as shown in Figure 3, the Rate Relationship in diagram is: f _s1=2f _s2=4f _s3.Half-band filter 121 is Kaiser windows, and FIR filter 122 is Hamming windows;

Below provided a bandwidth fp=500KHz, sample rate is f _sthe signal of=4.8MHz carries out 4 times of down-sampled examples, and table 1 is some parameters about dual stage filter:

Table 1

Passband fluctuation and the stopband attenuation of first order HB filter 121 are δ=0.001(60dB), that designs is filtered into 11 rank, and nonzero coefficient has 4, and middle one be 0.5, and the required multiplying of filtering is seldom.

The passband of second level Hamming window filter and the ripple coefficient δ=0.0022(53dB of stopband), totally 64 rank, coefficient of efficiency has 32.

If do not adopt the two-stage cascade pattern, only use a FIR filter 122, while meeting the design's parameter request, the exponent number of filter is at least wanted 128 rank, so structure of the present invention greatly reduces the exponent number of filter, has reduced operand.

Data rated output mean value in a regular length after 13 pairs of power calculation unit are down-sampled, pass to simulation AGC controller 14 and digital AGC device 15 by the power average obtained; Power calculation unit 13 comprises squarer, accumulator sum counter, output for down-sampled unit 12, after squared by squarer, by accumulator, add up again, after being averaging, the cumulative sum obtained is transferred to simulation AGC controller 14 and digital AGC device 15, by the length of the input signal of counter controls power calculation unit 13, the length of calculating can be compromised and be considered that gain accuracy and coefficient update speed arrange, and realize that by adjusting this length the time of AGC coefficient update is controlled.In the present embodiment, calculate all sampled point power in an OFDM symbol;

14 gains for control simulation VGA10 of simulation AGC controller, the power average is changed into to the LOG(logarithm) value, then calculate the difference with the first preset reference power Ref_power1 in the LOG territory, finally be encoded into the gain coefficient of simulation VGA10, feed back to simulation VGA10, and flow to digital AGC device 15.As shown in Figure 4, simulation AGC controller 14 comprises Logarithmic calculation unit 141, subtracter 142, adder 143, register 144 and analog gain coefficient elements 145, wherein:

Logarithmic calculation unit 141 changes into the LOG value by the power average, converts to take the 10 LOG values that are the end, and at first power average P converts to and take the 2 LOG values that are the end by shift operation, based on relationship:

$\log 10\left(P\right)=\frac{\log 2\left(p\right)}{\log 2\left(10\right)}$

Then be multiplied by a constant [1/ (log2 (10))], just converted to and take the 10 LOG values that are the end; Here do not use traditional cordic algorithm (rotation of coordinate numerical calculation method), but take the calculating of the 10 LOG values that are the end by displacement and multiplication realization, greatly reduced operand;

Subtracter 142 calculates the difference of LOG value and the first preset reference power Ref_power1, obtains the current power difference; The first preset reference power Ref_power1, be based on the range of ADC11 and precision setting, in the present embodiment, be arranged to the ADC11 full range of power-10dB;

Adder 143 for calculate current power difference and last gain and, obtain current gain value;

Register 144 is for storing current gain value, and the initial value of register is 0;

Analog gain coefficient elements 145, for current gain value is encoded into to the gain coefficient of binary bits form according to the gain step size of simulation VGA, feeds back to simulation VGA.

Digital AGC device 15 is for the gain of control figure VGA16, the gain coefficient that utilizes simulation AGC controller 14 to provide is adjusted current average power (output of power calculation unit 13), then the power average after calculate adjusting and the ratio of the second preset reference power Ref_power2, and power gain factor (this ratio) is converted to the amplitude gain coefficient feedover to digital VGA16.As shown in Figure 5, digital AGC device 15 comprises multiplier 151, divider 152 and amplitude gain coefficient elements 153, wherein:

Gain coefficient and power average that multiplier 151 will be simulated VGA multiply each other, and the gain power average makes the power average after gain approach the power average of next time calculating; Use the purpose of the gain coefficient adjustment current power average of simulation VGA to be to enable digital AGC device 15 before simulation AGC controller 14 is stable, reduce the data that the AGC process consumes, and the shortening stable time of AGC;

The ratio of power average after divider 152 calculated gains and the second preset reference power Ref_power2; The second preset reference power Ref_power2 is to arrange according to the needs of follow-up Digital Signal Processing;

Amplitude gain coefficient elements 153 feedovers to digital VGA16 for converting power gain factor (ratio) to the amplitude gain coefficient.The amplitude gain coefficient, be specially the extraction of square root of power gain factor, and for convenience of hardware designs, A can approximate by displacement 2 integral number power, but precision is slightly lost;

Numeral VGA16 receives the signal of down-sampled unit 12 outputs, this signal times is realized to the convergent-divergent of digital signal with the amplitude gain coefficient, by digital circuit.When coefficient is designed to 2 integral number power, multiplication can be realized by displacement.

Refer to Fig. 6, the present invention's two the auto gain control method based on one of the present invention, specifically comprise the following steps:

Step S1, by simulation, VGA10 realizes the convergent-divergent of analog input signal;

Step S2, be converted to digital signal by ADC11 by the analog input signal after convergent-divergent;

Step S3, undertaken down-sampledly by 12 pairs of down-sampled unit digital signal, reduce data rate; Be specially: at first, digital signal is through several half-band filters 121, carries out the extraction of 2 times after each half-band filter 121, then, through a FIR filter 122, carries out the afterbody extraction, and down-sampled general times is N=2^ (p) ^*q, N can not be too large, and wherein, p is half-band filter 121 numbers, the extracting multiple that q is afterbody FIR filter 122;

Step S4, by the average of the down-sampled output data power of power calculation unit 13 calculating, that is:, to the rated output mean value in a regular length of the data after down-sampled, in the present embodiment, calculate all sampled point power in an OFDM symbol;

Step S5, carry out analog gain calculating by simulation AGC controller 14: the power average that step S4 is provided changes into the LOG(logarithm) value, then the difference with the first preset reference power Ref_power1 in the calculating of LOG territory, finally be encoded into the gain coefficient of simulating VGA; Wherein, the first preset reference power Ref_power1, be based on analog-to-digital range and precision setting; The power average is transformed into the LOG value, is to convert to take the 10 LOG values that are the end, is attached to hardware and realizes, at first power average P converts to and take the 2 LOG values that are the end by shift operation, based on relationship:

$\log 10\left(P\right)=\frac{\log 2\left(p\right)}{\log 2\left(10\right)}$

Then be multiplied by a constant [1/ (log2 (10))], just converted to and take the 10 LOG values that are the end;

Step S6, by digital AGC device 15, utilize the gain coefficient gain current power average of the simulation VGA go out according to the current power mean value computation, makes the power average after gain approach the power average of next time calculating;

Step S7, carry out digital gain calculating by digital AGC device 15: the ratio of the power average after calculated gains and the second preset reference power Ref_power2, and this ratio (power gain factor) is converted to the amplitude gain coefficient; Wherein, the second preset reference power Ref_power2, be to arrange according to the needs of follow-up Digital Signal Processing.The amplitude gain coefficient, be specially the extraction of square root of power gain factor;

Step S8, amplitude gain coefficient step S7 provided by digital VGA16 is multiplied by input signal and realizes convergent-divergent, and when coefficient is designed to 2 integral number power, multiplication can be realized by displacement; Wherein, input signal refers to the digital signal of down-sampled rear output in step S3.

The gain coefficient of above-mentioned calculating simulation and digital gain coefficient, can first calculate the analog gain coefficient and calculate digital gain coefficient again, according to the needs of real system, also can before the stable simulation gain coefficient, enable the calculating of digital gain factor.In the present invention, the gain coefficient of simulation VGA10 and digital VGA16 has three kinds of operating states at least, and the one, new state more, coefficient is provided by simulation AGC controller 14 or digital AGC device 15; The 2nd, stable state, coefficient is provided by latch; The 3rd, idle condition, gain coefficient is 1.This enforcement provides a kind of control flow as shown in Figure 7, below in conjunction with Fig. 1, illustrates:

During beginning, simulation AGC controller 14 or digital AGC device 15 are all in idle condition, and gain coefficient is 1;

After this enter step S001, simulation VGA10 enables, digital VGA16 disable, and gain coefficient still remains 1, in conjunction with Fig. 1, refers to the beginning of symbol _ 0;

After this enter step S002, simulation VGA10, in new state more, upgrades the analog gain coefficients by simulation AGC controller 14;

After this enter step S003, after several symbols, simulation VGA10 is set to stable state, latchs gain coefficient, simultaneously, enables digital VGA16, and the end of the is-symbol of embodiment middle finger _ 1, can certainly be arranged to other value;

After this enter step S004, digital VGA16, in new state more, upgrades digital gain factor by digital AGC device 15;

After this enter step S005, after several symbols, digital VGA16 is set to stable state, latchs gain coefficient, and the end of the is-symbol of embodiment middle finger _ 1 equally also can be arranged to other value.

It is above-mentioned that provide is the embodiment of a kind of AGC of simulation and the digital AGC step that enables respectively, upgrade, just complete the adjustment of two-stage AGC in two OFDM symbols, it is short that AGC adjusts the time, needs according to real system, also can after simulation AGC is stable, enable digital AGC, realize the controlled of AGC coefficient stabilization time by the adjustment time of control simulation AGC and digital AGC.

Above embodiment is used for illustrative purposes only, but not limitation of the present invention, person skilled in the relevant technique, without departing from the spirit and scope of the present invention, can also make various conversion or modification, therefore all technical schemes that are equal to also should belong to category of the present invention, should be limited by each claim.

Claims (12)

1. an automatic gain control equipment, comprise simulation VGA, ADC and digital VGA, it is characterized in that, described automatic gain control equipment also comprises down-sampled unit, power calculation unit, simulation AGC controller and digital AGC device; Described simulation VGA, ADC, down-sampled unit are connected successively with digital VGA; Described power calculation unit connects respectively down-sampled unit, simulation AGC controller and digital AGC device; Described simulation AGC controller is connecting analog VGA and digital AGC device respectively; Described digital AGC device connects digital VGA, wherein:

Down-sampled module, carry out down-sampledly for the output signal to described ADC, after reducing data rate, export to described power calculation unit and digital VGA;

Power calculation unit, for the rated output mean value in a regular length of the data to after down-sampled, pass to described simulation AGC controller and digital AGC device by the power average obtained;

Simulation AGC controller, according to the gain coefficient of described power average and the described simulation of the first preset reference power calculation VGA, and pass to described simulation VGA and digital AGC device;

The digital AGC device, utilize the gain coefficient of the described simulation VGA described power average that gains, and then according to power average and the second preset reference power calculation amplitude gain coefficient after gain, feedovers to described digital VGA.

2. automatic gain control equipment according to claim 1, is characterized in that, described down-sampled module comprises several half-band filters and a FIR filter of cascade successively, wherein:

Carry out the extraction of 2 times after each half-band filter;

The FIR filter carries out the afterbody extraction.

3. automatic gain control equipment according to claim 1, is characterized in that, described power calculation unit comprises squarer, accumulator sum counter, wherein:

Squarer, squared for the output to described down-sampled unit, the square value of obtaining is passed to described accumulator;

Accumulator, cumulative for the square value by receiving, after being averaging, the cumulative sum obtained is transferred to described simulation AGC controller and digital AGC device;

Counter, for the length of control inputs signal, realize that the AGC coefficient update time is controlled.

4. automatic gain control equipment according to claim 1, is characterized in that, described simulation AGC controller comprises Logarithmic calculation unit, subtracter, adder, register and analog gain coefficient elements, wherein:

The Logarithmic calculation unit, change into the LOG value by described power average;

Subtracter, the difference of calculating LOG value and the first preset reference power Ref_power1, obtain the current power difference, and give described adder;

Adder, for calculate current power difference and last yield value and, obtain current gain value, and give described register and analog gain coefficient elements yield value;

Register, for storing current gain value;

The analog gain coefficient elements, for current gain value is encoded into to gain coefficient by gain step size, feed back to described simulation VGA.

5. automatic gain control equipment according to claim 4, it is characterized in that, described Logarithmic calculation unit converts described power average to take the 10 LOG values that are the end to, and at first power average P converts to and take the 2 LOG values that are the end by shift operation, based on relationship:

$\log 10\left(P\right)=\frac{\log 2\left(p\right)}{\log 2\left(10\right)}$

Then be multiplied by a constant, convert to and take the 10 LOG values that are the end.

6. automatic gain control equipment according to claim 1, is characterized in that, described digital AGC device comprises multiplier, divider and amplitude gain coefficient elements, wherein:

Multiplier, multiply each other gain coefficient and the power average of simulation VGA, the gain power average;

Divider, the power average after calculated gains and the ratio of the second preset reference power, obtain power gain factor;

The amplitude gain coefficient elements, for power gain factor being converted to the amplitude gain coefficient, feedforward is to described digital VGA.

7. automatic gain control equipment according to claim 6, is characterized in that, described amplitude gain coefficient is the extraction of square root of power gain factor.

8. automatic gain control equipment according to claim 1, is characterized in that, can first calculate the gain coefficient of simulation VGA, then calculate the amplitude gain coefficient; Also can before the gain coefficient of stable simulation VGA, enable the calculating of amplitude gain coefficient, realize that AGC is controlled stabilization time by the adjustment time of controlling two-stage AGC.

9. the auto gain control method based on the described automatic gain control equipment of claim 1, is characterized in that, comprises the following steps:

Step S1, realize the convergent-divergent of analog input signal;

Step S2, be converted to digital signal by the analog input signal after convergent-divergent;

Step S3, carry out down-sampled to digital signal;

Step S4, calculate the power average of data in a regular length after down-sampled;

Step S5, change into the LOG value to the power average, and then the difference with the first preset reference power in the calculating of LOG territory, finally be encoded into the gain coefficient of simulating VGA;

Step S6, utilize the gain coefficient gain power average of described simulation VGA;

Step S7, the power average after calculated gains and the ratio of the second preset reference power, obtain power gain factor, and power gain factor converted to the amplitude gain coefficient;

Step S8, be multiplied by the amplitude gain coefficient digital signal of down-sampled rear output, realizes convergent-divergent.

10. auto gain control method according to claim 9, is characterized in that, described step S3 comprises: at first, digital signal is through several half-band filters, carry out the extraction of 2 times after each half-band filter, then, through a FIR filter, carry out the afterbody extraction.

11. auto gain control method according to claim 9, is characterized in that, in described step S5, described power average is transformed into the LOG value, refers to: at first by shift operation, convert to and take the 2 LOG values that are the end, based on relationship:

$\log 10\left(P\right)=\frac{\log 2\left(p\right)}{\log 2\left(10\right)},$

Wherein, P is the power average;

Then be multiplied by a constant, obtain take the 10 LOG values that are the end.

12. auto gain control method according to claim 9, is characterized in that, described amplitude gain coefficient is the extraction of square root of power gain factor.

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