CN102196212A - Method and apparatus for automatic gain control - Google Patents

Abstract

The invention relates to a method and apparatus for automatic gain control, capable of controlling the intensity of a signal applied to and received from a receiver for receiving a digital broadcast signal to a constant level. An input signal received by a gain error detector is compensated by a compensation signal to detect the gain error and the detected gain error is accumulated by a loop filter. The accumulated gain error value is compensated by a compensation signal generator based on a preset compensation function to generate a compensate signal and the received input signal detected by the gain error detector is compensated according to the generated compensation signal.

Description

The equipment and the method that are used for automatic gain control

The application is that denomination of invention is " equipment and the method that are used for automatic gain control " (application number: 200710128885.3; The applying date: the dividing an application of application on March 2nd, 2007).

Technical field

The present invention relates to be used for the equipment and the method for automatic gain control, more specifically, relate to the gain that is used for adjusting automatically the broadcast singal that receives from the receiver of receiving broadcast signal equipment and method.

Background technology

Following description is usually directed to be used for automatic gain control (AGC) equipment and method, and this automatic gain control is used for adjusting automatically the gain of the broadcast singal that receives from the receiver of receiving broadcast signal.

At present, digital broadcasting is just carried out local standardized based on multiple technologies.For example, the broadcast standard of discussing in China comprises digital ground multimedia broadcast (DTMB).The DTMB standard that comes into question has adopted the new modulation scheme that is called as time-domain synchronous orthogonal frequency division multiplex (TDS-OFDM).

The service that is based on the OFDM scheme that adopt in Europe, OFDM scheme are to transmit one of modulation scheme of surface wave with digital signal.In the OFDM scheme, information is divided in several carrier waves, and provides orthogonality to be used to minimize gap between the carrier wave of being divided, and described carrier wave is re-used and sends out then.

Usually; in the TDS-OFDM scheme; transmit data just as in Cyclic Prefix (cyclic prefix) OFDM (CP-OFDM); (IDFT) carries out by inverse discrete Fourier transformer inverse-discrete, and in protection interval (GI), uses pseudo noise (PN) sequence as doing training signal (known array; pilot frequency sequence) replaces Cyclic Prefix; to reduce transport overhead, increase channel efficiency, and strengthen the performance of synchronizer and channel estimator.The equation of creating the PN sequence can obtain by following formula 1.

[formula 1]

P(x)＝x ⁸+x ⁶+x ⁵+x+1

It is very important that the receiver that is used to receive the transmission data that transmitted by DTMB remains on the intensity of received signal on the constant level, remains steady state value with the correlated results that allows the PN sequence always.

For the intensity with received signal remains on the constant level, the gain error value of accumulation predetermined reference signal and received signal in automatic gain control (AGC) equipment, and the gain error value of being accumulated is generated as gain control signal, is used to adjust the amplitude gain of received signal.Respond the gain error value of being accumulated and generate compensating signal, to compensate the signal that is received.

According to the compensating signal of the gain error value of being accumulated formal representation with exponential function, at this, compensating signal is stored in the memory as question blank in advance, and read the compensating signal corresponding with the gain error value of being accumulated and export this compensating signal from memory, this will increase the capacity of memory.

Summary of the invention

[technical problem]

The disclosed purpose of example provides the equipment and the method for a kind of automatic gain control (AGC), and it is not by making the size that realizes AGC under the memory-aided situation and can reduce hardware in fact.

Another purpose provides a kind of equipment and method can real-time update AGC bandwidth, that be used for automatic gain control.

[technical solution]

In the example embodiment of the disclosed AGC equipment according to example, the gain error detector response compensates the input signal that is received in signal, to detect the gain error value.Accumulate detected gain error value by loop filter, and the gain error value of utilizing the default penalty function of compensating signal generator to compensate to be accumulated to be generating compensating signal, and the compensating signal that is generated is outputed to the gain error detector to allow compensated input signal.

In the example embodiment of disclosed AGC method according to example, compensate the input signal that is received in response to compensating signal, detect the gain error value, the detected gain control value that adds up compensates the gain error value of being accumulated to generate compensating signal in response to default penalty function.

[advantageous effects]

Example openly can reduce the size of hardware by AGC and cancellation memory and the controll block of optimizing digital ground multimedia broadcast (DTMB) receiver.In addition, may control the amplitude gain of AGC amplifier adaptively, thereby the intensity of received signal is remained on the constant level always by the irregular change of tackling received signal effectively.

Description of drawings

By with reference to the embodiment that describes by example in the following description and with reference to the accompanying drawings, these and other aspect of the present disclosure is with apparition and will be illustrated.In any possible place, in whole accompanying drawing, use identical Reference numeral to indicate same or analogous part.

Fig. 1 be illustrate from the transmission frame that DTMB transmits, the schematic diagram of protection structure at interval with 1/9 size of frame.

Fig. 2 is the block diagram of configuration that illustrates the transmitter of DTMB.

Fig. 3 is the block diagram that illustrates the configuration of the receiver in DTMB.

Fig. 4 is the block diagram that illustrates the configuration of AGC equipment.

Fig. 5 is the curve chart that illustrates the gain curve that AGC equipment adopted.

Fig. 6 is the block diagram that illustrates according to the configuration of the AGC equipment of example embodiment.

Fig. 7 is the block diagram that illustrates according to the configuration of the AGC equipment of another example embodiment.

Fig. 8 and Fig. 9 illustrate the curve chart that the output signal according to the AGC equipment of another example embodiment changes.

Embodiment

Described embodiment only is used for explanation but is not used in restriction.Be provided at this item of describing illustrated to help understanding disclosed in conjunction with the accompanying drawings some example embodiment of the present invention all sidedly.Therefore, those of ordinary skill in the art will recognize: can carry out various changes and modification to example embodiment described here, and not deviate from desired scope of invention and spirit.Therefore, the application is applicable in useful and the simplest mode and explains its general principle and notion.

Fig. 1 be illustrate from the transmission frame that DTMB transmits, its protection is the block diagram of the structure of 1/9 frame at interval.

With reference to figure 1, the transmission frame that transmits from DTMB comprises frame synchronization and as the frame of data break.

Frame synchronization comprises the PN sequence.The PN sequence that is used for frame synchronization is for example used but is not limited to the wherein sequence of parameter m=8.In the sequence of parameter m=8, have only 255 bit streams.Therefore, when the protection of 1/9 size with frame generated at interval, the code element of afterbody was extended to lead code, and the code element of beginning part is extended to postamble (postamble), has the PN sequence of 420 code elements with generation.

For example, if frame will be made up of 3780 code elements, the protection that then has 1/9 size of frame must be made up of 420 sign indicating numbers at interval.Therefore, in order to create 420 code elements with 255 code elements, 50 code elements that then are positioned at afterbody are expanded and are lead code, and 155 code elements that are positioned at the beginning part are expanded and are postamble.At this moment, lead code and postamble are the cyclic extensions of PN code, and the PN code is in its response initial condition and from 0 to 254 variation on the phase place that generates.

Fig. 2 is the block diagram of the configuration of diagram DTMB transmitter.With reference to figure 2, in transmitter, Voice ﹠ Video (AV) signal as the data that will transmit is encoded by chnnel coding unit (200).The data of being carried out chnnel coding by chnnel coding unit (200) are imported into quadrature amplitude modulation (QAM) unit (202), and are modulated among 4QAM, 16QAM or the 64QAM one.

QAM unit (202) changes from the amplitude and the phase place of the numerical data of chnnel coding unit (200) input and modulates this amplitude and phase place, make the data of chnnel coding whether be modulated into 4,16 or 64QAM in one depend on that numerical data is disperseed and is modulated to how many coordinates (corordinates).

By IDFT unit (204) data of QAM unit (202) modulation are carried out inverse discrete Fourier transform (IDFT), and be transformed to time domain data.In addition, PN generator (206) establishment will be as PN (pseudo noise) sequence of training signal.

Be imported into multiplexer (208) from time domain data of IDFT unit (204) output and the PN sequence that generates by PN generator (206), and carry out multiplexedly therein, and in square root raised cosine (SQRC) filter (210), filter to limit its bandwidth.

Mix with carrier signal (fc) in frequency mixer (212) by the transmission data that SQRC filter (210) filters, and up-converted to radio frequency (RF) bandwidth of 450～860MHz, send out then.

Fig. 3 is the block diagram that illustrates the configuration of the receiver in DTMB.Now, with reference to figure 3, tuner (300) receives radio frequency (RF) the transmission data that the bandwidth that is transmitted by transmitter is 450～860MHz.In AGC amplifier (302), will be normalized to the constant level its gain from the signal power that tuner (300) receives, and be converted to digital signal by analog to digital converter (ADC.304).

Phase splitter (306) is separated into same-phase signal and orthogonal signalling with the output signal of ADC (304), and realizes Frequency Synchronization by frequency synchronisation (308).

Frequency synchronisation (308) mainly comprises three unit, comprising: 1. automatic frequency controller (AFC.358), and it is poor to be used for compensating frequency; 2. timing synchronizer (360) is used for the PN sequence that is transmitted by transmitter synchronously; And 3. tracking cell (362) and sampler (352) again, be used to compensate the different symbol errors that produce of sampling rate when transmitter and receiver is digital signal with analog signal conversion.

Aforesaid operations is all as the correlated results of PN correlator (356) and realize.In other words, AFC (358) generates the AFC signal as the correlated results of PN correlator (356), and this AFC signal that is generated multiply by the estimated frequency error of compensation mutually with the output signal of phase splitter (306) in multiplier (350).

In addition, the regularly correlated results of synchronizer (360) response PN correlator (356) and synchronic PN sequence.And tracker (362) is controlled sampler (352) with the symbol error of compensation from the signal of multiplier (350) output again in response to the output signal of timing synchronizer (360).

By SQRC filter (354) output signal of sampler (352) is again filtered to be entered into PN correlator (356).The output signal of SQRC filter (354) is imported in the AGC signal detector (310) to detect the AGC signal, and the amplitude gain of AGC amplifier (302) changes according to detected AGC signal, thereby the gain of received signal can be adjusted on the constant level.

Discrete Fourier transformer (DFT.312,314) is carried out DFT to the code element of AGC signal detector (310) output with from the channel estimating information of PN correlator (356) output, and carries out channel compensation by equalizer (316), to output to channel decoder.

As mentioned above, in the receiver of DTMB, AFC (358) compensates frequency displacement according to the correlated results of PN correlator (356).Especially, regularly synchronizer (360) thus detect and follow a peak value of associative operation after, expressing to detect effective peak, for this reason, have only peak value to be used to regularly synchronous above predetermined threshold.

Therefore, it is very important remaining on the constant level by the intensity with received signal always and the correlated results of PN sequence is remained constant level always.Therefore, the DTMB receiver is equipped with the AGC equipment that comprises AGC signal detector (310) and AGC amplifier (302), thereby can be always the intensity of received signal be remained on the constant level.

Fig. 4 is the block diagram that illustrates the configuration of AGC equipment.

With reference to figure 4, AGC equipment mainly is made up of gain error detector (400), loop filter (410) and compensating signal generator (420).

Gain error detector (400) comprise two multipliers (402), power checker (404), mean value computation device (406) and, subtracter (408).Two multipliers (402) multiply each other in-phase signal (I_IN) and orthogonal signalling (Q_IN) and compensating signal respectively, with the compensating gain error and output to DFT (312).In addition, power checker (404) is measured the power of the output signal of multiplier (402), and utilizes mean value computation device (406) that the average power measured value of measuring an image duration is calculated.Subtracter deducts default reference power to detect gain error from the average power content that is calculated.

Be imported into loop filter (410) and postponed by the detected gain error of gain error detector (400) by delayer (414).Adder (412) is added to by the detected gain error of gain error detector (400) output of delayer (414) with the storage gain error.The gain error of being accumulated outputs to AGC amplifier (302) as the AGC signal, adjusts the gain amplifier of AGC amplifier (302) thus.

In addition, be imported into the storage control (422) of compensating signal generator (420) by loop filter (410) gain error of being accumulated, at this, storage control (422) is read the compensating signal value corresponding with the gain error of being accumulated from memory (424), multiplier (402) multiplies each other the compensating signal read and in-phase signal (I_IN) and orthogonal signalling (Q_IN) so that gain error is compensated.

In other words, memory (424) with the form memory response in advance of question blank in the compensating signal value of the gain error value of being accumulated.Storage control (422) is read from memory (424) and the corresponding compensating signal value of importing from loop filter (410) of gain error value, with the compensating gain error.

For example represent with the compensating signal that the question blank form is stored in the memory (424) with exponential form as shown in Figure 5.Therefore, if the gain error value of accumulation is big in loop filter (410), then the compensating signal value then becomes bigger, thereby increases compensation magnitude; And if the value of the gain error of being accumulated is little, then the compensating signal value becomes littler, to reduce compensation magnitude, has strengthened the stability of AGC loop thus.

In order directly the nonlinear function as exponential function to be carried out computing, common way is to use algorithm to converge to the value of hope by carrying out repetitive operation.Therefore, in the circuit of the high speed operation of operating with high-frequency clock, it is very difficult adjusting data rate when exponential function is carried out computing, but is possible when hardware size increases.The actual use is that the form of precalculated exponential function value with question blank is stored in the memory (424) in advance, rather than direct gauge index function.

At this moment, determine the gain step size of AGC, thereby can greatly suppress according to the memory span of quantization step with the bit width use that is distributed according to the quantization step of exponential function curve.

For example, suppose that from the input range of the exponential function of loop filter (410) input be 1024 data, and, have two byte-sized from the exponential function of compensating signal generator (420) output with respect to each input data, the desired volume of memory (424) will be two kilobytes, increase the whole size of receiver thus.Therefore, when generating compensating signal, it is very favourable not using memory with regard to hardware size.

Now, with reference to figure 6, it is the block diagram that illustrates according to the configuration of the AGC equipment of example embodiment, the power of this AGC calculation of equipments received signal and difference (the Δ δ between the desirable reference power _n).And operate as follows: if the difference of being calculated (Δ δ _n) big, then the value of feedback of compensating signal just reduces; And if the difference of being calculated (Δ δ _n) little, then value of feedback just increases.

Usually, the deviation of the power of received signal is quite big.Therefore, with a frame time corresponding during the result that obtains from the power averaging of code element be used to improve the estimated performance that the power received signal is estimated.Comprise gain error detector (400), loop filter (410) and compensating signal generator (600) according to AGC equipment of the present disclosure.

As mentioned above, gain error detector (400) is used to detect gain error, and wherein loop filter (410) is accumulated the gain error that is detected, and the gain error of being accumulated is used to generate the AGC signal to adjust the amplitude gain of AGC amplifier (302).

Compensating signal generator (600) is according to the gain error value of default penalty function cause compensation loop filter (410) accumulation, and generate compensating signal thus, and the compensating signal that is generated is imported into the multiplier (402) of gain error detector (400), so that gain error is compensated.

At this moment, suppose: because the bandpass width of loop filter (410) is than wide from the transmission data tape of gain error detector (400) input, so loop filter (410) is not carried out function.Now, will describe compensating signal generator (600) generates compensating signal in response to the gain error of exporting from gain error detector (400) processing in detail.

Following formula 2 has defined gain error value (the Δ δ that gain error detector (400) detected in the last time (n-1) _N-1), formula 3 shows gain error value (the Δ δ that gain error detector (400) detected in the current time (n) _n).

[formula 2]

${\mathrm{\Δ\δ}}_{n-1}={\mathrm{\α}}_{n-1}^2\left[\underset{m=(n-1)-N}{\overset{n-1}{\mathrm{\Σ}}}(i_m^2+q_m^2)\right]-\mathrm{ref}$

[formula 3]

${\mathrm{\Δ\δ}}_n={\mathrm{\α}}_n^2\left[\underset{m=n-N}{\overset{n-1}{\mathrm{\Σ}}}(i_m^2+q_m^2)\right]-\mathrm{ref}$

Wherein, (α) defined the compensating signal that is generated by compensating signal generator (600), N has defined a frame, i _mAnd q _mBe the in-phase signal (I_IN) imported and the power of orthogonal signalling (Q_IN), ref refers to default reference power.

At this moment, the performance number of last time (n-1) is defined as

Then, following formula 4 can be derived by formula 2.

Formula 4

$p(n-1)=\frac{\mathrm{ref}+{\mathrm{\Δ\δ}}_{n-1}}{{\mathrm{\α}}_{n-1}^2}$

If it is constant in single frame to suppose with the ofdm system to be that the impulse response of communication channel of model changes, then goes up p as a result (n) that received signal is averaged by N and between the last p as a result (n-1) that received signal is averaged by N of last time (n-1), be roughly the same in the current time (n) as can be seen.As shown in Equation 5.

Formula 5

$p(n-1)\≅p\left(n\right)$

Then, can derive following formula 6 with respect to the current time (n).

Formula 6

$p\left(n\right)=\frac{\mathrm{ref}+{\mathrm{\Δ\δ}}_n}{{\mathrm{\α}}_n^2}\⇒{\mathrm{\α}}_n^{2}p\left(n\right)=\mathrm{ref}+{\mathrm{\Δ\δ}}_n$

Now, if value p (n) the substitution formula 6 that is drawn by formula 4 can obtain following formula 7.

Formula 7

${\mathrm{\α}}_n^2\left(\frac{\mathrm{ref}+{\mathrm{\Δ\δ}}_{n-1}}{{\mathrm{\α}}_{n-1}^2}\right)=\mathrm{ref}+{\mathrm{\Δ\δ}}_n\⇒{\mathrm{\α}}_n^2=\frac{\mathrm{ref}+{\mathrm{\Δ\δ}}_n}{\mathrm{ref}+{\mathrm{\Δ\δ}}_{n-1}}{\mathrm{\α}}_{n-1}^2$

Then, the value (α of the compensating signal that generated of compensating signal generator (600) _n) can draw from following formula 8:

Formula 8

${\mathrm{\α}}_n={\mathrm{\α}}_{n-1}\sqrt{\frac{\mathrm{ref}+{\mathrm{\Δ\δ}}_n}{\mathrm{ref}+\mathrm{\Δ}{\mathrm{\δ}}_{n-1}}}$

The formula 8 that has defined relation between formula 2 and the formula 3 can be called as the characteristic function of compensating signal generator (600).

If negative feedback type AGC equipment is stable, then As time goes on diminish, and the compensating signal that is generated by compensating signal generator (600) must converge to constant by the detected gain error value of gain error detector (400).

If operation of receiver is stable, following formula 9 has illustrated that the characteristic function of compensating signal generator (600) converges to constant.

Formula 9

Wherein, ignored the influence of loop filter (100), because compare little that the output signal of gain error detector (100) may be suitable with the bandwidth of loop filter (200).

In order to satisfy the condition of formula 9, the mode that will must reduce with the absolute value of the output on the gain error detector (100) in the output of the compensating signal generator (600) of current time (n) compensation is determined.

Following formula 10 represented compensating signal generator (600), be used for the compensating signal value that generates in the last time (n-1) based on compensating signal generator (600) and make gain error detector (100) minimize necessary output condition in detected gain error value of current time (n).

Formula 10

${\mathrm{\&alpha;}}_n^2\left[\underset{m=n-N}{\overset{n-1}{\mathrm{\&Sigma;}}}(i_m^2+q_m^2)\right]-\mathrm{ref}={\mathrm{\&Delta;\&delta;}}_n<<{\mathrm{\&Delta;\&delta;}}_{n-1}\&DoubleRightArrow;{\mathrm{\&alpha;}}_n^2\left[\underset{m=n-N}{\overset{n-1}{\mathrm{\&Sigma;}}}(i_m^2+q_m^2)\right]-\mathrm{ref}\&cong;0$

In other words, if gain error (the Δ δ that hypothesis gain error detector (400) detected in the last time (n-1) _N-1) significantly less than gain error value (the Δ δ of gain error detector (100) in current time current time (n) detection _n), then the average power of input signal multiply by the compensating signal that is generated by compensating signal generator (600), and deducts reference power from the value that multiplies each other, and wherein institute's value of deducting is to be necessary for zero gain error value.

At this moment, the compensating signal that is generated by compensating signal generator (600) is the function of gain error detector (400) in the gain error of current time (n) detection.Therefore, only when the power of the input signal that can accurately estimate to receive, can estimate the The optimal compensation signal that generates by compensating signal generator (600) in the current time.

AGC equipment is used to measure the interior average power content of section at the fixed time, to measure the accurate power of the input signal that is received, makes that average power content and the difference between the average power content of current time (n) measurement measured in the last time (n-1) are very little.

As a result, can be used on average power content that the last time (n-1) calculates, and can use formula 4, set up and the relevant function of compensating signal generator (600) according to formula 11 and formula 12 as the average power estimated value of current time (n).

Formula 11

${\mathrm{\&alpha;}}_n^2=\frac{\mathrm{ref}}{\underset{m=n-N}{\overset{n-1}{\mathrm{\&Sigma;}}}(i_m^2+q_m^2)}=\frac{\mathrm{ref}}{p\left(n\right)}\&cong;\frac{\mathrm{ref}}{\hat{p}\left(n\right)}\&cong;\frac{\mathrm{ref}}{p(n-1)}={\mathrm{\&alpha;}}_{n-1}^2\frac{\mathrm{ref}}{\mathrm{ref}+{\mathrm{\&Delta;\&delta;}}_{n-1}}$

Formula 12

${\mathrm{\&alpha;}}_n={\mathrm{\&alpha;}}_{n-1}\sqrt{\frac{\mathrm{ref}}{\mathrm{ref}+{\mathrm{\&Delta;\&delta;}}_{n-1}}}$

Here,

Be the average power estimated value of p (n), here

If the function of formula 12 is applied on the compensating signal generator (600), the size variation that then can minimize received signal is to improve receptivity.Yet,, therefore be necessary to be equipped with independent memory and store compensating signal in advance or be equipped with independent circuit and come computing formula 12 because formula 12 adopted subduplicate form.

In order to solve this shortcoming, the disclosure uses Taylor series that square root function is changed to the form of linear function, thereby AGC equipment can be save the single memory that is used to calculate the independent circuit of square root function or stores compensating signal with the form of question blank in advance.Formula 12 can expand to following formula 13.

Formula 13

${\mathrm{\&alpha;}}_n={\mathrm{\&alpha;}}_{n-1}\sqrt{\frac{\mathrm{ref}}{\mathrm{ref}+{\mathrm{\&Delta;\&delta;}}_{n-1}}}={\mathrm{\&alpha;}}_{n-1}\sqrt{\frac{1}{1+\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}}{\mathrm{ref}}}},$ $\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}}{\mathrm{ref}}<<1$

In the formula 13 Can expand to following formula 14.

Formula 14

$\sqrt{\frac{1}{1+\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}}{\mathrm{ref}}}}={(1+\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}}{\mathrm{ref}})}^{-\frac{1}{2}}={(1+y)}^{-\frac{1}{2}},$ $\frac{\mathrm{\&Delta;}{\mathrm{\&delta;}}_{n-1}}{\mathrm{ref}}=y$

If as in the formula 14, replace

And use just can be derived the functional form that is similar to formula 13 as the Taylor series of formula 15.

Formula 15

${(1+y)}^n=1+n\&CenterDot;y+\frac{n(n-1)}{2}{y}^2+...$

At this moment, if be input to gain error value (the Δ δ of compensating signal generator (600) _N-1) bigger, then generate very large approximate error value.Yet receiver is used for adjusting gain amplifier in response to the AGC signal of exporting from the AGC amplifier, feasible gain error value (the Δ δ that is input to compensating signal generator (600) _N-1) dynamic range be not very big.Therefore, can ignore and formula 13 is being approximately the error that produces in the process of linear function.

As the result who formula 13 is carried out Taylor series expansion, compensating signal generator (600) generates the approximate penalty function of compensating signal shown in following formula 16.

Formula 16

${\mathrm{\&alpha;}}_n=(1-\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}}{2\mathrm{ref}})\&CenterDot;{\mathrm{\&alpha;}}_{n-1}$

Thus, compensating signal generator (600) comprising: fader (610) is used for adjusting gain error value (the Δ δ that is input to compensating signal generator (600) _N-1) gain; And compensator (620), be used for by utilizing compensating signal value α in output of last time (n-1) _N-1Come compensating gain adjuster (610) to adjust the gain error value of its gain And the compensating signal α of generation current time (n) _n

Fader (610) for example uses, and its amplitude gain is

Amplifier make up.For example, compensator (620) comprising: delayer (622), be used to the to postpone current time compensating signal (α of (n) _n); Multiplier (624) multiplies each other the output signal of fader (610) and the output signal of delayer (622); And adder (626), the output signal and the output signal of multiplier (624) of delayer (622) generated mutually the compensating signal α of current time (n) _n

The invention pattern

Fig. 7 is the block diagram that illustrates according to the configuration of the AGC equipment of another example embodiment.With reference now to Fig. 7,, AGC equipment also comprises gain error compensator (700), and it is inserted between gain error detector (400) and the loop filter (410).This gain error compensator (700) predetermined threshold value (TH).If less than preset threshold value (TH), then failure of consideration is from the gain error value of gain error detector (400) output from the gain error value of gain error detector (400) output, but tale quale outputs to loop filter (410) with it.If greater than preset threshold value (TH), then utilize threshold value (TH) to proofread and correct, and the value after will proofreading and correct outputs to loop filter (410) from the gain error value of gain error detector (400) output from the gain error value of gain error detector (400) output.

In other words, in this another example embodiment, as shown in formula 17, will be from gain error value (the Δ δ of gain error detector (400) output _N-1) and preset threshold value (TH) compare.Result as a comparison, if | Δ δ _N-1|≤TH, then compensating signal generator (600) uses gain error value (Δ δ _N-1) the compensating gain error.If | Δ δ _N-1|＞TH, then compensating signal generator (600) uses

Rather than (Δ δ _N-1) as the gain error value, thus the compensating gain error.

Formula 17

${\mathrm{\&alpha;}}_n=(1-\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}^{\&prime;}}{2\mathrm{ref}})\&CenterDot;{\mathrm{\&alpha;}}_{n-1}\left\{\begin{array}{c}\left|{\mathrm{\&Delta;\&delta;}}_{n-1}\right|\&le;\mathrm{TH},{\mathrm{\&Delta;\&delta;}}_{n-1}^{\&prime;}={\mathrm{\&Delta;\&delta;}}_{n-1}\\ \left|{\mathrm{\&Delta;\&delta;}}_{n-1}\right|>\mathrm{TH},{\mathrm{\&Delta;\&delta;}}_{n-1}^{\&prime;}=\frac{{\mathrm{\&Delta;\&delta;}}_{n-1}}{\mathrm{TH}}\end{array}\right.$

For this reason, in another example embodiment, gain error compensator (700) is equipped with comparator (702), in order to gain error value (Δ δ _N-1) and preset threshold value (TH) compare; Adjuster (704) is equipped with and, in order to gain error value (Δ δ _N-1) proofread and correct to be

Device (702) result relatively as a comparison, if | Δ δ _N-1|≤TH, then converting unit (706) output gain error amount (Δ δ _N-1), and if | Δ δ _N-1|＞TH, then converting unit (706) output

As the gain error value.

As mentioned above, in another example embodiment, according to gain error value (Δ δ _N-1) size and utilize two functions to come the bandwidth of Adjustment System, thereby can suppress that input signal is suddenly big to be changed or the transient response of system with imitating, can make system stability.

Fig. 8 and Fig. 9 illustrate according to another example embodiment, from the curve chart that the output signal of compensating signal generator (600) output changes, and wherein change threshold (TH) is to check the performance of using AGC equipment of the present disclosure.

Now,, can notice that when threshold value (TH) changed, the bandwidth of system also changed with reference to figure 8 and Fig. 9.In the degeneration factor such as AGC equipment of the present disclosure, if bandwidth is big, then variation of output signals as shown in Figure 8.Alternatively, if bandwidth is little, variation of output signals as shown in Figure 9.

Although in conjunction with embodiment of the present disclosure the disclosure is described, it is apparent to those skilled in the art that disclosed application can be revised according to multiple mode, and can suppose the many preferred embodiments except that above-mentioned specific embodiment.Therefore, claims are intended to contain all open modifications that fall within true spirit of the present invention and the scope.

Industrial applicibility

According to the disclosure, the various digital broadcasting signal receivers that are used for the digital broadcasting signal of reception such as digital ground multimedia broadcasting (DTMB) signal are equipped with equipment and the method for automatic gain control (AGC), to adjust the intensity that receives signal.

Claims (16)

1. broadcast signal transmission machine that is used to handle broadcast singal, it comprises:

The chnnel coding unit, it is configured to broadcast singal is carried out chnnel coding;

Quadrature amplitude modulation (QAM) unit, it is configured to coded broadcast singal is carried out the QAM modulation;

The PN generator, it is configured to create the PN sequence;

Multiplexer, it is configured to form transmission frame, and described transmission frame comprises frame synchronization with 420 code elements and the frame with 3780 code elements, and described frame is based on described broadcast singal through the QAM modulation, and described frame synchronization comprises the PN sequence;

Frequency mixer, it is configured to transmit formed transmission frame.

2. broadcast signal transmission machine as claimed in claim 1, wherein, described frame synchronization further comprises lead code and postamble, the code element number of described lead code is less than the code element number of described postamble.

3. broadcast signal transmission machine as claimed in claim 2, wherein, described lead code is the cyclic extensions of described PN sequence.

4. broadcast signal transmission machine as claimed in claim 2, wherein, described postamble is the cyclic extensions of described PN sequence.

5. broadcast signal receiver that is used to handle broadcast singal, it comprises:

Tuner, it is configured to receive the broadcast singal that comprises transmission frame, described transmission frame comprises frame synchronization with 420 code elements and the frame with 3780 code elements, and described frame is based on described broadcast singal through the QAM modulation, and described frame synchronization comprises the PN sequence;

Analog to digital converter, its broadcast singal that is configured to be received is converted to digital broadcast signal;

Equalizer, it is configured to the digital broadcast signal of being changed is carried out channel compensation.

6. broadcast signal receiver as claimed in claim 5, wherein, described frame synchronization further comprises lead code and postamble, the code element number of described lead code is less than the code element number of described postamble.

7. broadcast signal receiver as claimed in claim 6, wherein, described lead code is the cyclic extensions of described PN sequence.

8. broadcast signal receiver as claimed in claim 6, wherein, described postamble is the cyclic extensions of described PN sequence.

9. method that is used for handling broadcast singal at the broadcast signal transmission machine, it comprises:

Broadcast singal is carried out chnnel coding;

Coded broadcast singal is carried out quadrature amplitude modulation (QAM);

Create the PN sequence;

Form transmission frame, described transmission frame comprises frame synchronization with 420 code elements and the frame with 3780 code elements, and described frame is based on described broadcast singal through the QAM modulation, and described frame synchronization comprises the PN sequence;

Transmit formed transmission frame.

10. method as claimed in claim 9, wherein, described frame synchronization further comprises lead code and postamble, the code element number of described lead code is less than the code element number of described postamble.

11. method as claimed in claim 10, wherein, described lead code is the cyclic extensions of described PN sequence.

12. method as claimed in claim 10, wherein, described postamble is the cyclic extensions of described PN sequence.

13. a method that is used for handling at broadcast signal receiver broadcast singal, it comprises:

Reception comprises the broadcast singal of transmission frame, and described transmission frame comprises frame synchronization with 420 code elements and the frame with 3780 code elements, and described frame is based on described broadcast singal through the QAM modulation, and described frame synchronization comprises the PN sequence;

The broadcast singal that is received is converted to digital broadcast signal;

The digital broadcast signal of being changed is carried out channel compensation.

14. method as claimed in claim 13, wherein, described frame synchronization further comprises lead code and postamble, and the code element number of described lead code is less than the code element number of described postamble.

15. method as claimed in claim 14, wherein, described lead code is the cyclic extensions of described PN sequence.

16. method as claimed in claim 14, wherein, described postamble is the cyclic extensions of described PN sequence.

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