CN1510909A

CN1510909A - Automatic gain controller of digital TV-set receiver

Info

Publication number: CN1510909A
Application number: CNA021569053A
Authority: CN
Inventors: 李泰源
Original assignee: LG Electronics Shenyang Inc
Current assignee: LG Electronics Shenyang Inc
Priority date: 2002-12-23
Filing date: 2002-12-23
Publication date: 2004-07-07

Abstract

This invention relates to AGC (automatic gain control) device for digital TV receiver,. Specially can automatically control the reference value of RF AGC (radio frequency automatic gain control) according to the state of channel to ratio of distribute radio frequency and medium frequency, so can make best AGC. Besides, due to digital structure of receiving chip, can carry through RF AGC and IP AGC (intermediate frequency automatic gain control) directly, so it is easy to integrate it into one chip; because it selectively uses receiving signal of pass band and base band to determine gain error, so can improve the function of receiving system.

Description

The automatic gain control equipment of digital television receiver

[technical field]

The invention relates to auto-gain control device for digital television receiver (the Auto Gain Control that uses residual sideband (VSB) mode; AGC).

[background technology]

Fig. 1 is the Digital Television structured flowchart that comprises general AGC device.

Among the figure, 101: tuner 102:SAW (surface acoustic wave) filter

103:IF amplifies and the converter that falls progressively

Digital Television is a kind of television system of developing in order to experience the strong atmosphere of arenas in family.Compare with the simulated television of present extensive use, improved definition, the fabric width of picture greatly, and the multichannel sound accompaniment of CD level is provided.

About this class Digital Television, the U.S., Europe, Japan and other countries are being formulated the broadcast system and the specification that meet self respectively and are being advanced its benchmark.With the U.S. is example, and the transmission standard has been taked residual sideband (VSB) mode by U.S. Jie Nisi (Zenith) proposition; The video compression of compression standard aspect has been taked the MPEG benchmark; Doby AC-3 has been taked in audio compression; Show that standard then is defined as and the existing method maintenance interchangeability of showing.

On the other hand, the signal gain size of being sent by the portion of posting a letter is normally certain, still since signal arrive receiver the distance of process, and when arriving receiver,, cause the size of signal gain to change to some extent by various passages.This signal that has changed the gain size will be input in the receiver.But when most of digital circuit of design receiver, suppose that all input signal is that a gain that has a certain size is imported usually.Therefore, just be necessary to regulate the analog signal gain that is input to receiver, one of make to have a certain size gain, and then be transformed into digital signal to maintenance.

What play this effect is exactly automatic gain control (Auto Gain Control:AGC) device.The AGC device is to judge present input signal gain (gain) according to the average level of input signal or power (Power).And according to the gain of judging, the amplifier in control radio frequency and intermediate frequency (intermediate frequency) analog circuit makes signal have required size.

The most of AGC device that uses all utilizes delay (Delayed) AGC mode as shown in Figure 1 now.

At first, modulated VSB high frequency (radio frequency) signal is by after the antenna input,, tuner (101) is the RF signal transformation of 40～860MHZ the 1IF signal of 44MHZ, outputs to then to adopt the SAW filter (102) of removing adjacent channel signal and noise signal function.Here, the output valve size of tuner (101) is regulated according to the RF amplifying stage in the tuner (101).

At this moment, in the digitlization play signal, because in the intermediate frequency of 44MHZ, exist all information in the 6MHZ frequency band.So in SAW filter (102), only stay the 6MHZ frequency band that has information from tuner (101) output, and remove after all remaining frequency bands, be input to IF and amplify and the converter that falls progressively (103).

IF amplifies and the converter that falls progressively (103), to receive one in order to generate after the frequency of oscillation (not shown) that the 2IF signal uses, filtering signal, be transformed into the 2IF signal that falls progressively, and then output to VSB acceptance division (104) again by SAW filter (102) output.

At this moment, the 1IF signal after its gain is controlled, is input to VSB acceptance division (104) again in IF amplification and the converter that falls progressively (103).Be IF amplify and the converter that falls progressively (103) when falling progressively conversion, or when in VSB acceptance division (104), carrying out digitlization to received signal, will go to control the gain of 1IF signal, make signal magnitude become required value.

VSB acceptance division (104) carries out the controlled 2IF signal that gains carrying out digitized processing again after the VSB.Simultaneously, in order to carry out automatic gain control, be input to AGC signal generation (100) to the VSB restituted signal after the demodulation.

AGC signal generation (104), for instance, it has the information that receiver is extremely regulated gain to current being used to from the work initial stage; When the signal after the input VSB demodulation, will compare with the gain information value of having stored; If the signal gain that receives is little, just generation is made gain become big IF AGC signal; If the signal gain that receives is big, the IF AGC signal that just generation is made gain diminish; To be fed back to IF then amplifies and the converter that falls progressively (103).

The IF AGC signal that IF amplifies and the converter that falls progressively (103) basis is transfused to increases, subtracts the yield value of 1IF signal, makes the 1IF signal gain become required state.

That is, the method for regulating actual gain is at first in opening power or when changing passage, allows receiver have maximum yield value, then according to the gain size of input signal, at first IF amplify and the converter that falls progressively (103) in regulate and gain.

Gain-adjusted ability when IF amplification and the converter that falls progressively (103), though reach capacity, but the output signal of VSB acceptance division (104), when still not reaching desired gain size, AGC signal generation (100) will be regulated the yield value of tuner again automatically to tuner (101) propagation delay RF AGC signal.

At this moment, be input to the fixing RF AGC fiducial value of AGC signal generation (100), with the proportion of decision RF gain with the IF gain.When RF gains heavy the time, received signal is amplified very big that section put in prime, from lacking that noise figure (noise figure) characteristic aspect noise appends.What therefore the signal to noise ratio (snr) of signal band descended lacks.But, if exist when influencing the adjacent channel of receive path, since at SAW filter (102) leading portion that the yield value that obtains is very big, can become responsive to the influence of adjacent channel; In addition, when a plurality of RF passages are input to tuner (101), because of in the amplifying stage of tuner, will producing saturation condition, thereby can make distorted signals, and then reduce SNR.

Otherwise when the IF gain proportion that is in SAW filter (102) back segment became big, though can prevent the saturation condition that influence and RF to adjacent channel amplify section, the further amplification because of noise can reduce SNR.

So the RF AGC fiducial value of decision RF gain and IF gain proportion has just had the relation of exchange (trade-off).

[summary of the invention]

The objective of the invention is to, a kind of environmental condition according to receive path is provided, regulate the digital television receiver AGC devices and methods therefor of RFAGC fiducial value automatically.

In order to achieve the above object and the AGC device of digitlization TV receiver of exploitation, structurally has following characteristics, that is: be provided with a tuning portion, it will be from the radiofrequency signal that receives by antenna, only de-tuned specific radiofrequency signal, and by the rf gain control signal of importing, automatically go to regulate tuning radiofrequency signal gain, then it is transformed to intermediate-freuqncy signal; Be provided with an intermediate frequency and amplify and transformation component, it will go to regulate automatically the 1IF signal gain by tuner output according to the IF AGC signal of input, then it will be transformed into the 2IF signal; Be provided with a VSB acceptance division, it is with 2nd intermediate-freuqncy signal of demodulation by intermediate frequency AGC amplification and transformation component output, simultaneously, according to by the signal SNR of demodulation, go to control automatically RF AGC fiducial value, and utilize the signal of RF AGC fiducial value and demodulation, and generate RF AGC signal and IF AGC signal, output to tuner and intermediate frequency AGC again and amplify and transformation component.

The VSB acceptance division has following architectural feature, is provided with a demodulation section that is:, it to amplify at IF and transformation component in the 2IF signal of the controlled passband of gain, carry out the VSB demodulation, and be the 2IF signal transformation of passband baseband signal; Be provided with the SNR calculating part, it will calculate from the signal to noise ratio (snr) of demodulation section output; Be provided with RF AGC benchmark control part, it regulates RF AGC value automatically according to the SNR value; Be provided with RF and IF AGC portion, the received signal that it utilizes RF AGC fiducial value and is exported by demodulation section generates IF AGC signal and RF AGC signal, and to IF amplification and transformation component and tuner output.

RF and IF AGC portion have the following structures feature, that is: be provided with an AGC error detector, it is to being undertaken by the passband of demodulation section output and baseband receiving signals after square processing, obtain and the reference power value between difference, and exported as the gain error value; Be provided with the belt filter of IF, it accumulates detected IF gain error; Be provided with IF and change and tower-sigma digital antenna transformation component, it is the signal transformation of the belt filter of IF an analog signal, and amplifies and transformation component output to IF; Be provided with and postpone AGC portion, obtain the poor of the RFAGC fiducial value exported by the signal of IF loop filter feedback and RF AGC benchmark control part, and export as RF gain error value; Be provided with the RF loop filter, its accumulation is by the RF gain error value that postpones the output of AGC portion; Be provided with RF and change and tower-sigma DAC (digital-to-analog converter), it is the signal transformation of RF loop filter output an analog signal, and exports to tuner with the RFAGC signal.

The feature of RF AGC benchmark control part is, the signal SNR value that receives and original SNR value compared, if littler than original SNR value, would be the convergence direction transformation of RF AGC fiducial value opposite direction so just; If bigger, so the convergence direction of RF AGC fiducial value is just maintained the statusquo than original SNR value.

RF AGC benchmark control part also has another feature to be, the SNR value of the signal that receives and original SNR value are compared, if two values are consistent, goes to set the convergence direction of RF AGC fiducial value so, makes RF AGC reference value gets smaller.

The feature of SNR calculating part is, the filtering synchronizing signal that is contained in the demodulated received signal is carried out a square processing with the difference of training sequential value, and after accumulating, obtain mean value, calculate the Mean Square Error (MSE) of received signal, and adopt the MSE value to detect the SNR value.

The SNR calculating part also has another feature to be, demodulated received signal and judgement star is carried out a square processing as value difference, and obtain mean value after accumulating, and calculates the Mean Square Error (MSE) of received signal, detects the SNR value with the MSE value again.

Purpose of the present invention, feature and advantage can be understood the detailed description of example by the reference accompanying drawing.

Below, to example of the present invention, described in detail with reference to accompanying drawing.

[description of drawings]

Fig. 2 is the Digital Television structured flowchart according to the AGC of comprising device of the present invention.

Fig. 3 is the detailed diagram of RF and IF AGC portion in Fig. 2.

Fig. 4 illustrates the RF of Fig. 2 and the example block diagram of IF AGC portion.

Fig. 5 is changing and the detailed diagram of tower-sigma DAC of Fig. 2.

Fig. 6 is the detailed diagram of the RF AGC benchmark control part of Fig. 2.

Fig. 7 is the coordinate diagram that SNR and RF AGC fiducial value correlation are shown.

Fig. 8 is an exemplary construction block diagram of MSE calculating part that is applicable to the SNR computing system of Fig. 2

The symbol description at the main position of drawing

101: tuner 102:SAW (surface acoustic wave) filter

103:IF amplifies and converter 200:VSB (residual sideband) acceptance division that falls progressively

201: demodulation section 202:SNR (signal to noise ratio) calculating part

203:RF AGC benchmark control part 204:RF and IF AGC portion

The 301:AGC error-detecting 302:IF of the portion filter that goes in ring

303:IF changes and tower-sigma DAC (digital-to-analog converter) 304: postpone AGC portion

The belt filter 306:RF of 305:RF changes and tower-sigma DAC

[embodiment]

The present invention directly carries out RF AGC and IF AGC for realizing the single integrated of a plurality of systems from receiving chip; Especially can calculate the SNR of received signal, and, go to regulate automatically the fiducial value of RF AGC according to the SNR value.

Fig. 2 illustrates digital television receiver structured flowchart of the present invention.Be used for directly controlling the digital integrated chip VSB acceptance division (200) of RF signal gain and IF signal gain, by forming with the lower part.That is: the controlled 2IF signal of handlebar gain carries out the demodulation section (201) of VSB demodulation process; The SNR value SNR calculating part (202) that calculates by demodulation section output is arranged; : with good grounds SNR value is regulated the RF AGC benchmark control part (203) of RFAGC fiducial value; RF and IF AGC portion (204) are arranged, and passband or baseband receiving signals that it will utilize RF AGC fiducial value and be exported by demodulation section (201) generate IF AGC signal and RF AGC signal, and amplify and transformation component (103) and tuner (101) output signal to IF.In Fig. 2, tuner (101), SAW filter (102) and IF amplify and the transformation component that falls progressively (103) is the AFE (analog front end) part, because its formation and work are identical with Fig. 1, therefore use same-sign, describe in detail then and omit.

Fig. 3 is the RF of Fig. 2 and the structured flowchart of IF AGC portion (204), and Fig. 4 is the detailed diagram of RF and IF AGC portion (204), and it is made of following part.From passband or baseband receiving signals, detect AGC error AGC error-detecting portion (301); Accumulate detected AGC error IF loop filter (302); The analog signal that is transformed to 1 bit by IF loop filter (302) power output, change and tower-sigma (Delta-sigma) D-A converter (Digital Analog Converter) (303) with IF to IF amplification and transformation component (103) output IF AGC signal then; Utilize the signal and the RF AGC reference signal of IF loop filter (302) feedback, generate the AGC signal delayer (304) that postpones; The output valve of accumulated delay AGC portion (304) RF loop filter (305); RF loop filter power output is transformed to 1 bit analog signal, and changes and tower-sigma DAC (306) with RF to tuner output RF AGC signal.

At this moment, the AGC error-detecting portion (301) of RF and IF AGC (204), the signal of received passband or base band, and obtain the IF gain error.If use the received signal of passband, gain control loop can become very short so, and AGC is restrained fast.But, during not by band filter, can there be flip-flop and noise contribution, therefore need carry out the process of anticipating of a little.Anti-speech, when using baseband receiving signals, gain control loop is elongated relatively, though make convergence rate slack-off relatively, can obtain correct gain error.In the present invention, can optionally use by its application purpose.That is, convergence fast can utilize the received signal of passband to ask gain error so if desired; Obtain correct gain error if desired, can utilize the received signal of base band to try to achieve gain error so.

Below with reference to Fig. 3 and Fig. 4, describe the course of work of RF and IF AGC portion in detail: at first, the multiplier (301a) of AGC error-detecting portion (301) square is handled the received signal of passband or base band, and exports with the signal power value of received signal.The subtracter (301b) of AGC error-detecting portion (301) will go to ask poor between the signal power value of received signal and the AGC fiducial value (that is: reference signal performance number), and export to the IF loop filter as IF gain error value.

IF loop filter (302) will be accumulated the IF gain error value of input, and changes and tower-sigma DAC (303) output to IF, feeds back to the AGC portion (304) that postpones simultaneously.

Postpone poor between value that AGC portion (304) will obtain accumulation and feedback and the RF AGC fiducial value, and differ from as RF gain error value, export to RF loop filter (305) with this.The RF gain error value of accumulating in RF loop filter (305) will output to RF and change and tower-sigma DAC (306).

At this moment, IF, RF loop filter (302,305) will be at the frequency bands of AGC feedback loop, are feedback gain and the gain error value imported, are multiplied by a constant.This is in order to be restrained rapidly and to have less jittering noise characteristics and be provided with.In addition, the present invention uses with the multiplier of phase shifter (shift, 302a, 305a) as multiplication by constants in order to reduce hardware.Phase shifter (302a, 305a) is the right side phase shifter that plays the division effect by the signal of the input that moves right.

Be the phase shifter (302a) of the belt filter (302) of IF, will after the bit number right shift of having set, output to delayer (302b) to the IF gain error value that is input into.Delayer (302b) after a period of time, is exported the signal delay of input to adder (302c).Adder (302c) outputs to delayer (302d) after will carrying out addition to the signal of input with by the signal that back segment delayer (302d) feeds back.Delayer (302d) will be accumulated the signal of input, and the signal feedback of accumulation to adder (302c) with postpone AGC portion (304), change and tower-sigma DAC (303) exports to AF simultaneously.That is, delayer (302b), adder (302c) and delayer (302d) are a kind of integrators of accumulation input signal.

The go in ring composition of filter (305) of RF is also identical with the IF filter (302) that goes in ring.Be that it is with the RF gain error value that is input into, form by the phase shifter (305a) of the bit number right shift of setting and the signal integration device (305b, 305c, 305d) of accumulated shift.

Fig. 5 is that RF, IF change and the detailed diagram of tower-sigma DAC (303,306).It is transformed to the analog signal (IF AGC signal and RF AGC signal) of 1 bit separately to the value of belt filter (302) of IF and the belt filter (305) of RF, and outputs to IF amplification and transformation component (103) and tuner (101) output.

That is, subtracter (501) is the RF or the IF gain error value of accumulation in the filter (303 or 305) that goes in ring, with outputing to adder (502) by the maximum of MUX (506) output or the difference of minimum value.Adder (502) is exported to delayer (503) after carrying out addition the output valve of subtracter (501) with by the value of the delayer (503) of back segment feedback.Delayer (503) is only exported the bit of upper after the output valve of adder (502) is postponed a period of time as the selection signal of inverter (504) and MUX (506), feed back to adder (502) simultaneously.Behind the bit of the upper of inverter (504) counter-rotating delayer (503),, export after postponing a period of time again by delayer (505).

Fig. 6 is the detailed diagram of the RF AFC benchmark control part (203) of Fig. 2.It is the signal SNR value that receives according to final, obtains RF AGC fiducial value, and exports to the delay AGC portion (304) of RF and IF AGC portion (204).

Fig. 7 illustrates the SNR of final received signal and the coordinate diagram of RF AGC fiducial value correlation.From Fig. 7, can recognize, when RF AGC fiducial value becomes big,, SNR be diminished because the RF signal reduces; Anti-speech, in the time of RF AGC reference value gets smaller, the distorted signals phenomenon takes place because of the saturation condition of amplifier in the RF signal, and because of the influence of adjacent channel, SNR is also reduced.Thus, can recognize that best RF AGC datum mark has the highest SNR value.

Be after Fig. 6 shows the SNR that receives feedback, to make RF AGC fiducial value converge to the example of optimum value.

Fig. 6 is made up of following components.They are that the SNR value of received signal is delayed device (601) by what certain hour was delayed; Deduct the subtracter (602) of the SNR value that postpones by delayer (601) from the signal SNR value that receives; The multiplier (603) that the output valve and the direction signal of subtracter (602) multiplied each other; The belt filter (607) of continued product musical instruments used in a Buddhist or Taoist mass (603) output valve; After the output valve of the filter (607) that goes in ring and the deviant set carried out addition, the adder of exporting as the benchmark of RF AGC (608); Whether the output valve of checking subtracter (602) is 0, and exports the zero portion (604) of checking of selecting signal according to its result; According to the zero selection signal of checking portion (604), the multiplexer (605) of output-1 or output multiplier (603) signal; After pressing certain hour and postponing the output valve of multiplexer (605), with the symbol of inhibit signal as direction signal, to the delayer (606) of multiplier (603) output.Belt filter (607) and adder (608) are called RF AGC fiducial value efferent here; Multiplexer (605) and delayer (606) are called the direction signal efferent.

Fig. 6 that constitutes like this, initial stage RF AGC fiducial value is defined as bias, and suppose that the RF signal does not exist the saturation condition owing to amplifier that distorted signals takes place, and the influence that does not have adjacent channel, and go the direction initialization signal for reducing-1 direction of RF AGC fiducial value.That is be the direction setting of RF reference value gets smaller-1 direction; The RF fiducial value is become big direction setting be+1 direction.At this moment, if directional information is-1 o'clock, the gain proportion of RF will become big; If+IF gain proportion will become big in 1 o'clock.

For SNR calculating part (202),, generate so and allow signal, and export to RF AGC control part (203) when calculating first SNR value; Simultaneously SNR is fed back to the delayer (601) and the subtracter (602) of RF AGC control part (203).Delayer (601) is exported to subtracter (602) after will postponing by certain hour from the SNR value of input.Subtracter (602) deducts the SNR value that postpones by the delayer (601) from the present SNR value by SNR calculating part (202) input, afterwards its difference is transported to multiplier (603) and zero and checks portion (604).

At this moment, if the output valve of subtracter (602) is+value so, just to belong to the SNR value and become big situation (with reference to Fig. 7); If-value, be exactly the situation that SNR diminishes so.That is, the change of SNR value greatly just represents that SNR improves; The SNR value diminishes, and just represents that SNR degenerates.

Thus, if the SNR value diminishes, just should change RF AGC reference direction in the other direction into; If it is big that the SNR value becomes, so owing to just handling, so will keep direction signal present situation to get final product by optimum RF AGC datum mark.

In order to achieve the above object, multiplier (603) will multiply by the output valve of subtracter (602) by the direction signal of delayer (606) output and handle.When the output valve of multiplier (603) outputs to belt filter (607), will feed back to multiplexer (605).Multiplexer (605) will go to select the output valve or the selection-1 of multiplier (603) according to by the zero selection signal of checking portion (604) output, export to delayer (606) then.Delayer (606) is transformed to direction signal to the signal code that postpones, and exports to multiplier (603) by after the regular hour delay input signal.

For example, if the output valve of subtracter (602) is negative (-), direction signal also is negative (-), so, when its expression SNR value will diminish, the situation that RF AGC fiducial value also diminishes by little direction, therefore, the output valve of multiplier (603) will be (+) value just, promptly be transformed to the positive direction signal.And if the output valve of subtracter (602) is negative (-), direction signal is just (+), so, this expression SNR value will diminish, and RF AGC fiducial value is to become big situation to big direction, therefore, the output valve of multiplier (603) is " bearing " (-), promptly is transformed to negative (-) direction signal.

In addition, if the output valve of subtracter (602) is (+) value just, directional information is negative (-), so, its expression SNR value will become greatly, the situation that RF AGC fiducial value then diminishes to little direction, therefore, the output valve of multiplier (603) is negative (-), promptly continues to keep the negative direction signal of original delayer machine (606) output; If the output valve of subtracter (602) is in (+) value, directional information also is just (+), so, this expression SNR value will become big, RF AGC benchmark also becomes big situation to big direction, therefore, the output valve of multiplier (603) is (+) value, promptly continues to keep the positive direction signal of delayer (606) output.

At this moment, zero check whether the output valve that portion (604) will confirm subtracter (602) is 0.Here, the output valve of subtracter (602) is " 0 ", and the SNR value that expression is present is identical with the SNR value that is delayed; This situation is exactly that the highest SNR value is when being fed.At this moment, zero checks portion (604) will generate one to select signal to enable the choice direction signal be-1, and exports to multiplexer (605).That is, the difference of SNR equals at 0 o'clock, and multiplexer (605) is selected-1 direction signal.In other cases, generate an output valve of selecting signal to enable to select multiplier (603), and export to multiplexer (605).

Go in ring and export to adder (608) after filter (607) is accumulated the output valve of multiplier (603).

Go in ring filter (607) with the output valve of continued product musical instruments used in a Buddhist or Taoist mass (603), and export to adder (608); Adder (608) will be to the output valve of the filter (607) that goes in ring and the initial RF AGC fiducial value of having set, and promptly deviant is carried out after the addition, and its result as RF AGC fiducial value, is exported to the delay AGC portion (304) of RF and IF AGC portion (204).

At this moment, RF AGC fiducial value control part (203) also can receive the improper value that is included in the passage in the same old way, i.e. noise power is to substitute the SNR value of received signal; But by original, i.e. noise signal.At this moment, SNR value and the noise power relation of being inversely proportional to, so, in delayer (602), from the noise power that postpones, cut the noise power that is input into now and get final product.

On the other hand, SNR calculating part (202) is tried to achieve Mean Square Error (mean square error in the I of equilibrium channel data or the synchronous filtering signal that received; MSE) after the value, utilize the MSE value to calculate SNR.

Fig. 8 illustrates the MSE calculating part exemplary construction block diagram that is applicable to SNR calculating part (202).It can select dual mode to use.First kind of mode is only to detect the mode of error in demodulated received signal filtering sync section; It is to each filtering signal new data more.At this moment, subtracter (801) will be obtained received filtering synchronizing signal and train the poor of sequential value, and export to multiplier (802).

Second method is to detect the demodulated received signal, promptly detects the error mode of balanced I channel data and judgement star picture (decision constellation) value, and it can upgrade the data of each integrator form size.At this moment, subtracter (801) will and be judged the poor of star picture (R-I) value I channel data (R-I), and export to multiplier (802).

After multiplier (802) will carry out square processing to the output valve of subtracter (801),, and accumulate to accumulator (803) output.After the signal of accumulator (803) by the temporary accumulation of latch (Latch, 804), export to modulus calculation portion (805).Modulus calculation portion (805) when its count value is M, all resets to 0 in the output procedure of meter record latch (804).Accumulator (803), latch (804), modulus exerciser (805) are called integrator here.

At this moment, the M value in modulus exerciser (805) is, integrator promptly is input to the form value of accumulator (803).

And SNR can ask calculation with following mathematical expression 1.

[mathematical expression 1]

SNR＝10Elog(Ps/Pn)

In the formula, Ps is a signal power, during with 1 normalization,

Pn is noise power=Pn| _Mse,

PnC _mse＝Q(mse/m)

Mse＝(D_I-R_I) ²

R_I is the signal star picture (received constellations) of demodulation.

D_I is decision signal star picture (decision constellations).

M is the value of integrator form size.

As mentioned above, can promptly replace SNR, export to the delayer (601) and the subtracter (602) of RF AGC benchmark calculating part (203) with the MSE value with noise power.

The present invention is applicable to wired, wireless communication fields such as VSB9 (residual sideband), QAM (quadrature amplitude modulation), QPSK (four phase shift offset modulation), OFDM (orthogonal frequency-division) receivers.

As mentioned above, the AGC device of digital television receiver has following advantage:

The first, according to channel status, can control RF AGC fiducial value automatically, and distribute the proportion of RF gain and IF gain, can finish best AGC function.Promptly, can prevent the AGC performance decrease according to channel status.

The second, at the receiving chip that constitutes by numeral, directly go to finish RF AGC and IF AGC function, can carry out single integrated easily, especially when forming two or more different receiving system, can go to select separately RF AGC fiducial value by mode, therefore can have AGC.

The 3rd, according to application purpose, select the received signal of passband and base band, obtain error amount, so can improve the performance of receiving system.

By above explanation,, in the scope that does not break away from technological thought of the present invention, can carry out numerous variations or correction so as can be known if expert.

Claims

1, a kind of auto-gain control device for digital television receiver, it is characterized in that: be provided with a tuning portion, it will be from the radiofrequency signal that receives by antenna, only de-tuned specific radiofrequency signal, and by the rf gain control signal of importing, automatically go to regulate tuning radiofrequency signal gain, then it is transformed to intermediate-freuqncy signal;

Be provided with an intermediate frequency and amplify and transformation component, it will go to regulate automatically the 1IF signal gain by tuner output according to the IF AGC signal of input, then it will be transformed into the 2IF signal;

Be provided with a VSB acceptance division, it is with 2nd intermediate-freuqncy signal of demodulation by intermediate frequency AGC amplification and transformation component output, simultaneously, according to by the signal SNR of demodulation, go to control automatically RF AGC fiducial value, and utilize the signal of RF AGC fiducial value and demodulation, and generate RF AGC signal and IF AGC signal, output to tuner and intermediate frequency AGC again and amplify and transformation component.

2, according to the described auto-gain control device for digital television receiver of claim 1, it is characterized in that: VSB acceptance division wherein, form by following part, that is:

The VSB acceptance division has following architectural feature, is provided with a demodulation section that is:, it to amplify at IF and transformation component in the 2IF signal of the controlled passband of gain, carry out the VSB demodulation, and be the 2IF signal transformation of passband baseband signal;

Be provided with the SNR calculating part, it will calculate from the signal to noise ratio (snr) of demodulation section output;

Be provided with RF AGC benchmark control part, it regulates RF AGC value automatically according to the SNR value;

Be provided with RF and IF AGC portion, the received signal that it utilizes RF AGC fiducial value and is exported by demodulation section generates IF AGC signal and RF AGC signal, and to IF amplification and transformation component and tuner output.

3, according to the described auto-gain control device for digital television receiver of claim 2, it is characterized in that: the received signal that is input to RF and IF AGC is passband and baseband receiving signals.

4, according to the described auto-gain control device for digital television receiver of claim 2, it is characterized in that: incite somebody to action wherein RF AGC benchmark control part, the SNR value of received signal and original SNR value are compared,, go to set RF AGC fiducial value so and be the convergence direction if two values are consistent.

5, according to the described auto-gain control device for digital television receiver of claim 2, it is characterized in that: wherein RF AGC benchmark control part is made up of following part, that is:

Receive after the input signal SNR value of feedback, it is postponed the delayer of certain hour;

Deduct the subtracter of the SNR value that postpones by delayer (601) from the SNR value of received signal;

The multiplier that the output valve and the direction signal of subtracter multiplied each other;

After the output of continued product musical instruments used in a Buddhist or Taoist mass and after the deviant that is set at initial RF AGC benchmark carries out addition, the RF AGC fiducial value efferent of exporting as the benchmark of RF AGC;

Whether what confirm subtracter output is 0, and exports the zero portion of checking of selecting signal according to its result;

According to the zero selection signal of checking portion, go to select to export-1 or the output signal of output multiplier, then selecteed signal code as direction signal, to the direction signal efferent of multiplier output.

6, according to the described auto-gain control device for digital television receiver of claim 2, it is characterized in that: SNR calculating part wherein, the filtering synchronizing signal that is contained in the demodulated received signal is carried out a square processing with the difference of training sequential value, and after accumulating, obtain mean value, calculate the Mean Square Error (MSE) of received signal, and adopt the MSE value to detect the SNR value.

7, according to the described auto-gain control device for digital television receiver of claim 2, it is characterized in that: SNR calculating part wherein, demodulated received signal and judgement star are carried out a square processing as value difference, and accumulate and obtain mean value afterwards, calculate the Mean Square Error (MSE) of received signal, and then detect the SNR value with the MSE value.