CN102196212B - 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 bythe 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 equipment and method for automatic gain control, more specifically, relate to for the gain of automatically adjusting the broadcast singal that receives from the receiver of receiving broadcast signal equipment and method.

Background technology

Following description is usually directed to for automatic gain control (AGC) equipment and method, and this automatic gain control is used for automatically adjusting 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 come be used to the gap that minimizes between the carrier wave of dividing, and described carrier wave is re-used and then sends out.

Usually; in the TDS-OFDM scheme; transmit data just as among 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 that creates the PN sequence can obtain by following formula 1.

[formula 1]

P(x)＝x ⁸+x ⁶+x ⁵+x+1

The receiver that be used for to receive the transmission of data that is transmitted by DTMB is very important with the Strength retention of received signal in constant level, remains steady state value with the correlated results that allows the PN sequence always.

For with the Strength retention of received signal on 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 accumulating is generated as gain control signal, is used for adjusting the amplitude gain of received signal.Respond the gain error value of accumulating and generate compensating signal, to compensate the signal that is received.

According to the compensating signal of the gain error value of the accumulating formal representation with exponential function, at this, compensating signal is as question blank and pre-stored in memory, and the compensating signal that the gain error value of reading from memory and accumulating is corresponding is also exported this compensating signal, and this will increase the capacity of memory.

Summary of the invention

[technical problem]

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

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 receives 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 accumulate to be generating compensating signal, and the compensating signal that generates is outputed to the gain error detector to allow compensated input signal.

In the example embodiment of the disclosed AGC method according to example, compensate the input signal that receives in response to compensating signal, detect the gain error value, cumulative detected gain control value compensates the gain error value of accumulating to generate compensating signal in response to default penalty function.

[advantageous effects]

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

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 elucidated.In any possible place, in whole accompanying drawing, indicate same or analogous part with identical Reference numeral.

Fig. 1 be illustrate from the transmission frame that DTMB transmits, the schematic diagram of structure at protection 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 adopts.

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 to understand all sidedly by reference to the accompanying drawings disclosed some example embodiment of the present invention.Therefore, those of ordinary skill in the art will recognize: can example embodiment described here be made various changes and modifications, and do not deviate from desired scope of invention and spirit.Therefore, the application is applicable to explain its general principle and concept in useful and the simplest mode.

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

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, only have 255 bit streams.Therefore, when the protection interval of 1/9 size with frame generated, the code element of afterbody was extended to lead code, and the code element of beginning is extended to postamble (postamble), has the PN sequence of 420 code elements with generation.

For example, if frame will be comprised of 3780 code elements, the protection interval that then has 1/9 size of frame must be comprised of 420 codes.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 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, by chnnel coding unit (200) Voice ﹠ Video (AV) signal as the data that will transmit is encoded.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 amplitude and the phase place of the numerical data of chnnel coding unit (200) input and modulates this amplitude and phase place so that the data of chnnel coding whether be modulated into 4,16 or 64QAM in one depend on numerical data is dispersed 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 the time domain data of IDFT unit (204) output and the PN sequence that is generated by PN generator (206), and carry out therein multiplexedly, and in square root raised cosine (SQRC) filter (210), filter to limit its bandwidth.

The transmission of data that is filtered by SQRC filter (210) mixes with carrier signal (fc) in frequency mixer (212), and is up-converted to radio frequency (RF) bandwidth of 450～860MHz, then sends out.

Fig. 3 is the block diagram that illustrates the configuration of the receiver in DTMB.Now, with reference to figure 3, it is radio frequency (RF) the transmission of data of 450～860MHz that tuner (300) receives the bandwidth that is transmitted by transmitter.In AGC amplifier (302), will be normalized to from the signal power that tuner (300) receives the constant level its gain, 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 Synchronization device (360) is used for the PN sequence that is transmitted by transmitter synchronously; And 3. tracking cell (362) and again sampler (352), be used for the different symbol errors that produce of compensation 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 generates multiply by the estimated frequency error of compensation mutually with the output signal of phase splitter (306) in multiplier (350).

In addition, the correlated results of Timing Synchronization device (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 Synchronization device (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) carry out DFT to the code element of AGC signal detector (310) output with from the channel estimating information of PN correlator (356) output, and by equalizer (316) implementation channel compensation, 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, Timing Synchronization device (360) thus detect follow expression associative operation after a peak value to detect effective peak, for this reason, only have the peak value above predetermined threshold to be used to Timing Synchronization.

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), thus can be always with the Strength retention of received signal on constant level.

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

With reference to figure 4, AGC equipment mainly is comprised 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 calculates.

Be imported into loop filter (410) and postponed by delayer (414) by the detected gain error of gain error detector (400).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 accumulating outputs to AGC amplifier (302) as the AGC signal, adjusts thus the gain amplifier of AGC amplifier (302).

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

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

The compensating signal that is stored in the memory (424) with the question blank form for example represents with as shown in Figure 5 exponential form.Therefore, if the gain error value of accumulation is large in loop filter (410), then the compensating signal value then becomes larger, thereby increases compensation magnitude; And if the value of the gain error of accumulating is little, then the compensating signal value becomes less, to reduce compensation magnitude, has strengthened thus the stability of AGC loop.

In order directly the nonlinear function such as exponential function to be carried out computing, common way is the value that converges to hope by carrying out repetitive operation with algorithm.Therefore, in the circuit of the high speed operation that operates 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 according to the quantization step of exponential function curve, thereby can greatly suppress according to the memory span of quantization step with the bit width use that distributes.

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 thus the whole size of receiver.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, and this AGC equipment calculates the power of received signal and difference (the Δ δ between the desirable reference power _n).And operate as follows: if the difference of calculating (Δ δ _n) large, then the value of feedback of compensating signal just reduces; And if the difference of calculating (Δ δ _n) little, then value of feedback just increases.

Usually, the deviation of the power of received signal is quite large.Therefore, be used to improve the estimated performance that the power received signal is estimated at the time durations corresponding with frame from the result that the power averaging of code element obtains.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 for detection of gain error, wherein loop filter (410) is accumulated the gain error that detects, and the gain error of accumulating is used for generating 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 thus compensating signal, and the compensating signal that generates 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 of data band 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) inputted 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 that the impulse response of the communication channel take ofdm system as model changes, then can find out at the upper as a result p (n) that received signal is averaged by N of current time (n) and between the upper as a result p (n-1) that received signal is averaged by N of last time (n-1) to be roughly the same.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 generates 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 formula 2 and formula 3 Relations Amongs 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 diminished by the detected gain error value of gain error detector (400), and the compensating signal that is generated by compensating signal generator (600) must converge to constant.

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

AGC equipment is used for measuring average power content within a predetermined period of time, to measure the accurate power of the input signal that is received, so 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.

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

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,

The average power estimated value of p (n), here

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

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 for the independent circuit of Computation of Square Root function or with the single memory of the pre-stored compensating signal of form of question blank.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 such 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) larger, 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, so that be input to gain error value (the Δ δ of compensating signal generator (600) _N-1) dynamic range be not very large.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 the 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), the compensating signal (α that is used for postponing the current time (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 of the output signal of delayer (622) and multiplier (624) is 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 from the gain error value of gain error detector (400) output less than default threshold value (TH), then failure of consideration is from the gain error value of gain error detector (400) output, but tale quale outputs to loop filter (410) with it.If from the gain error value of gain error detector (400) output greater than default threshold value (TH), then utilize threshold value (TH) to proofread and correct from the gain error value of gain error detector (400) output, and the value after will proofreading and correct output to loop filter (410).

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 default 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 default 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 suddenly large the change or the transient response of system of input signal 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, with reference to figure 8 and Fig. 9, can notice that when threshold value (TH) changed, the bandwidth of system also changed.In the degeneration factor such as AGC equipment of the present disclosure, if be with roomyly, then the variation of output signal as shown in Figure 8.Alternatively, if bandwidth is little, the variation of output signal 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 various ways, and can suppose the many preferred embodiments except 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 broadcast signal of reception such as digital ground multimedia broadcast (DTMB) signal are equipped with equipment and the method for automatic gain control (AGC), to adjust the intensity that receives signal.

Claims (8)

1. broadcast signal transmission machine for the treatment of 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 the 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;

Square root raised cosine filter, it is configured to transmission frame is carried out filtering; And

Frequency mixer, it is configured to transmit filtered transmission frame,

Wherein, described frame synchronization comprises the PN sequence, described PN sequence has 255 code elements, in order to generate the frame synchronization with 420 code elements, described afterbody code element with PN sequence of 255 code elements is extended to lead code, and described code element with PN sequence beginning of 255 code elements is extended to postamble.

2. broadcast signal transmission machine as claimed in claim 1, wherein, described QAM is among 4QAM, 16QAM or the 64QAM.

3. broadcast signal receiver for the treatment of broadcast singal, it comprises:

Tuner, it is configured to receive the broadcast singal that comprises transmission frame, and described transmission frame comprises the 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;

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

Equalizer, it is configured to the digital broadcast signal of changing is carried out channel compensation,

Wherein, described frame synchronization comprises the PN sequence, described PN sequence has 255 code elements, in order to generate the frame synchronization with 420 code elements, described afterbody code element with PN sequence of 255 code elements is extended to lead code, and described code element with PN sequence beginning of 255 code elements is extended to postamble.

4. broadcast signal receiver as claimed in claim 3, wherein, described QAM is among 4QAM, 16QAM or the 64QAM.

5. method that is used for processing at the broadcast signal transmission machine broadcast singal, 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 the 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;

Described transmission frame is carried out filtering;

Transmit filtered transmission frame,

Wherein, described frame synchronization comprises the PN sequence, described PN sequence has 255 code elements, in order to generate the frame synchronization with 420 code elements, described afterbody code element with PN sequence of 255 code elements is extended to lead code, and described code element with PN sequence beginning of 255 code elements is extended to postamble.

6. method as claimed in claim 5, wherein, described QAM is among 4QAM, 16QAM or the 64QAM.

7. method that is used for processing at broadcast signal receiver broadcast singal, it comprises:

Reception comprises the broadcast singal of transmission frame, and described transmission frame comprises the 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;

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

The digital broadcast signal of changing is carried out channel compensation,

Wherein, described frame synchronization comprises the PN sequence, described PN sequence has 255 code elements, in order to generate the frame synchronization with 420 code elements, described afterbody code element with PN sequence of 255 code elements is extended to lead code, and described code element with PN sequence beginning of 255 code elements is extended to postamble.

8. method as claimed in claim 7, wherein, described QAM is among 4QAM, 16QAM or the 64QAM.

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