KR20060083666A - Method for detecting agc lock and mobile-type broadcasting receiver using it - Google Patents

Abstract

The present invention relates to an AGC lock detection method and a mobile broadcast receiver that prevents a malfunction of AGC by adjusting the AGC bandwidth when the power of the received signal is out of the AGC operating range. In particular, in the present invention, when the average power of the received signal is out of the AGC operating range, by adjusting the parameters of the AGC to bring the power of the received signal into the AGC operating region, the channel environment is severely changed and a gap filler which is a repeater for satellite DMB. Change in transmission output, shaded area, weak field, and strong field area can prevent AGC from falling out or malfunctioning. In addition, in the DMB receiver using two-path antenna diversity, the unlocked path signal may not be used when blocking input or combining data with another finger, thereby improving reception performance of the satellite DMB receiver.

AGC lock, unlock, AGC bandwidth adjustment

Description

Method for detecting AGC lock and mobile-type broadcasting receiver using it}

1 is a block diagram of a typical mobile satellite broadcasting receiver

2 is a view showing a frame structure of a typical satellite DMB pilot channel

3 is a block diagram showing an example of a conventional AGC device

4A is a block diagram showing an example of an AGC device according to the present invention;

4B is a detailed block diagram illustrating an embodiment of the gain controller of FIG. 4A.

5 is a flowchart showing an embodiment of an AGC lock detection method according to the present invention.

6 is a schematic diagram of a mobile satellite broadcast receiver to which two-path antenna diversity is applied according to the present invention;

Explanation of symbols for main parts of the drawings

10: tuner 11: AGC section

12: A / D conversion unit 31: reception signal power measurement unit

32: AGC error detector 33: gain control

34: Delta & Sigma Modulator 35: LPF

36: reference power generator

The present invention relates to a mobile broadcast receiver, and more particularly, to a method for detecting AGC lock in a satellite digital multimedia broadcasting (DMB) broadcast receiver.

In general, digital multimedia broadcasting (DMB) can be roughly divided into terrestrial DMB and satellite DMB. Terrestrial DMB provides audio and video services on the move based on Orthogonal Frequency Division Modulation (OFDM). In contrast, satellite DMB provides audio and video services on the move using satellite and complementary ground gap fillers based on CDM (Code Division Multiplexing). In other words, most of the terrestrial areas are directly received from satellites, and provide an environment where audio and video can be received anywhere by using the gap filler as a supplementary means such as shadowed areas and underground spaces by high-rise buildings in urban areas where direct reception is impossible. do.

Currently, the technical standard of satellite DMB adopted in Korea and Japan is the system E method specified by ITU, which basically adopts CDM transmission method, and is representative communication that broadcasts weather, traffic, video information using CD quality sound and various channels. It is a new concept service of broadcasting convergence.

These satellite DMBs use frequencies up 13.824-13.883 GHz, down 2.630-2.655 GHz, and 12.21-12.23 GHz, support up to 64 channels (32 channels in Korea and Japan), and feature wide coverage as a national broadcast. There is this. In addition, the transmission channel of the satellite DMB is a wireless mobile reception channel, and the amplitude of the received signal is not only time-varying, but also the Doppler shift of the received signal spectrum occurs due to the mobile reception. . In consideration of the transmission and reception under such a channel environment, the satellite DMB transmission scheme adopts the CDM scheme, and interleaving the time domain signals to correct errors occurring in the transmission channel. The CDM method spreads the frequency by multiplying the data to be transmitted by Pseudo Noise (PN) signal having a data rate much faster than the data. Since the signal exists over a wide band, the narrow-band signal interference (Narrow-band) It has a strong characteristic against interference, and it is possible to reduce reception performance deterioration due to multipath through a receiver having a RAKE structure. That is, in the satellite DMB transmitter, an error correction code is added to the transmission data of a plurality of channels, and each channel is transmitted independently by multiplying a Walsh code having a different 64-bit length for each channel. At this time, the data to be transmitted is multiplied by a 2048-bit Pseudo Noise (PN) signal having a much faster rate than the data to be transmitted by frequency spreading.

1 shows a conceptual block diagram of a general satellite DMB receiver for receiving such CDM signal. That is, the tuner 10 tunes only the RF signal of a specific frequency among the RF signals received by the antenna and converts the signal into baseband, and then converts the A / D into an auto gain control (AGC) unit 11. Output to section 12.

The AGC unit 11 generates a control signal for maintaining a constant magnitude of the signal output from the tuner 10 and feeds it back to the tuner 10. To this end, the AGC unit 11 measures the power of the received signal and multiplies the calculated gain by the received signal.

The A / D converter 12 receives a signal having a relatively constant magnitude by the AGC unit 11 from the tuner 10 and samples the converted signal to convert an analog signal into a digital signal. The digitized signal is output to a searcher 13 and a tracker of each finger 141 to 14n for demodulation. Each of the fingers 141 to 14n includes a tracker and a despreading unit.

In other words, in order to demodulate a signal in the CDM transmission scheme, the acquisition of a Pseudo Noise (PN) signal used for spreading the signal should be prioritized. This process involves two steps: acquisition and tracking of the signal. Is made of.

The division unit of the PN signal is called a chip, and signal acquisition is a process of securing signal synchronization within a 1/2 chip at a receiver, and is performed by the search unit 13. In addition, the signal tracking refers to finely synchronizing the found signals, and is performed in a tracker of each finger 141 to 14n. The despreading unit of each finger 141 to 14n despreads by multiplying the signal synchronized by the signal acquisition and tracking with the PN signal generated by the receiver, and by multiplying the corresponding WALSH code used to distinguish the CDM channels. The symbol of the desired CDM channel is extracted.

That is, the above-described signal tracking and despreading processes are performed in all the multipaths found by the search unit 13, and each of them is called a finger. In other words, signals received through different paths are assigned to the arbitrary fingers by the search unit 13 and demodulated. In this case, there may be various ways of allocating a finger, for example, using a pilot signal.

The CDM symbols of each path extracted from the fingers 141 to 14n are output to the RAKE synthesizer 16 and to the frequency offset estimator 15 for frequency offset compensation.

The frequency offset estimator 15 estimates the frequency offset for each finger, synthesizes it, and feeds it back to the tuner 10 to compensate for the frequency offset.

The rake synthesizer 16 synthesizes CDM symbols output from the fingers 141 to 14n. In this case, the rake synthesizer 16 may take a method of improving reception performance by estimating and compensating a reception channel environment. That is, the rake synthesizer 16 performs rake synthesis on all CDM channels for demodulation.

The signal synthesized by the rake synthesizer 16 is output to the demodulator 17. The demodulator 17 demodulates the pilot channel and the data channel by demodulating corresponding to the digital modulation on the transmitting side. The pilot channel includes information on interleaver size and convolutional coding rate.

FIG. 2 is a diagram illustrating a frame structure of such a satellite DMB pilot channel, in which one superframe, which is a transmission unit, is composed of six subframes, and each frame further includes 51 control data units D1 to D51 and respective control data. It consists of a pilot symbol (PS) inserted before the part. At this time, the pilot symbol PS is inserted every 250usec and transmitted together with the control data unit indicated by D1 to D51.

The pilot symbol PS is composed of consecutive 32-bit '1' and is used for multi-path search of the satellite DMB receiver, and D1 is used to determine whether the receiver is synchronized by transmitting in a 32-bit predefined pattern. . D2 is a frame counter and is used to keep the superframe in sync. D3 to D22 and D27 to D46 contain pilot information, and D23 to D26 and D47 to D50 contain error correction outer codes. And D51 includes extended information.

On the other hand, the size of the gain of the signal transmitted from the transmitter is always constant, but the gain of the signal changes through various channels until the distance to the receiver and the receiver are reached. The gain-modulated signal is input to the receiver, and most of the digital parts of the receiver are designed assuming that the signal is always input with a constant magnitude of gain. Therefore, it is necessary to adjust the gain of the analog signal input to the receiver so that it always has a constant gain, and then convert it into a digital signal. At this time, the level of the transmitter may be greater or smaller than the level of the receiver according to the transmission power and the reception power, so gain adjustment is necessary.

It is the auto gain control (AGC) device that plays this role.

The AGC device determines the gain of the current input signal by looking at the average power or instantaneous power of the input signal. At this time, according to the gain determined, the amplifier is controlled at the RF (high frequency) and IF (intermediate frequency) terminals of the tuner so that the signal has a desired size.

3 shows an AGC related block diagram of a typical satellite DMB broadcast receiver.

That is, the signal tuned by the tuner 10 and converted to the baseband is input to the reception signal power measurement unit 31 of the AGC unit 11.

The power measuring unit 31 estimates the power of the received signal from the baseband digital signal and outputs the AGC error detector 32. The AGC error detector 32 outputs the difference between the currently estimated power and the reference power generated by the reference power value generator 36 as the AGC error to the gain controller 33. The gain controller 33 integrates the AGC error using a time constant set according to the expected characteristic of the received signal and increases or decreases the gain of the tuner 10 from the result. Is generated and output to the delta & sigma modulator 34. The delta & sigma modulator 34 is a single bit D / A converter and converts a digital gain up or gain down control signal into a 1-bit analog signal and outputs it to the low pass filter 35. The low pass filter 35 filters the low-pass portion of the analog gain up or down control signal to make it smooth and outputs it to the tuner 10. The tuner 10 adjusts the gain of the analog RF signal and the IF signal within the input range of the A / D converter 12 according to the gain up or down control signal output from the low pass filter 35. At this time, by adjusting the gain of the tuner 10 through a feedback structure, the level of the received signal is kept constant.

At this time, the power measurement unit 31 obtains average power obtained by averaging instantaneous power or instantaneous power of a received signal for a predetermined period and outputting the average power to the AGC error detector 32.

 However, the AGC device of FIG. 3 has a severe change in the channel environment and is out of the dynamic range of the AGC according to the change in the transmission output of the gap filler Gap Filler, which is a satellite DMB repeater, the shadow area, the weak field, and the strong field area. It may malfunction.

The present invention is to solve the above problems, an object of the present invention is to adjust the AGC bandwidth when the power of the received signal is out of the AGC operating area, AGC lock detection method for preventing the malfunction of AGC and mobile broadcast using the same It is to provide a receiver.

In order to achieve the above object, the AGC lock detection method according to the present invention,

(a) determining whether the power of the received signal is outside a preset automatic gain control (AGC) operating area;

(b) determining to unlock when out of a predetermined AGC operation area and determining to AGC locking when within an AGC operation area; And

and (c) adjusting the bandwidth of the AGC when it is determined that the unlocking operation is performed.

In the step (a), if the average power of the received signal is between the upper threshold value and the lower threshold value generated based on the reference power, it is determined that it is within the AGC operation region.

In the step (b), if the average power of the received signal is not between the upper threshold value and the lower threshold value generated based on the reference power, the AGC unlock is determined.

A mobile broadcast receiver according to an embodiment of the present invention includes: a tuner for tuning a signal of a specific channel received through an antenna and adjusting and outputting a gain of the tuned signal according to a gain control signal; A power measuring unit calculating a power of a received signal output from the tuner; An AGC lock detector configured to generate an AGC locking signal indicating that the signal power calculated by the power measuring unit is unlocked when it is out of a preset AGC operating area, and locked when within the AGC operating area; A gain controller configured to detect an AGC error by comparing the signal power calculated by the power measurement unit with a reference power, and generate a gain control signal with a bandwidth adjusted by proportionally integral control of the detected AGC error according to the AGC locking signal; And a delta-sigma modulation and filter unit for analogizing the gain control signal output from the gain control unit, filtering only the low pass portion, and outputting the gain control signal to the tuner as a gain control signal.

According to another embodiment of the present invention, a mobile broadcast receiver using a plurality of antennas to receive a mobile broadcast signal for each finger includes:

A data processor is provided as many as the number of antennas, and each data processor receives a signal of a specific channel through a corresponding antenna to perform AGC and digitizes;

AGC lock detection units are provided as many as the number of data processing units, and each AGC lock detection unit is unlocked when the average power of the signal received by the data processing unit is out of the preset AGC operation region, and locks when the AGC lock detection unit is within the AGC operation region. Generate a signal;

And a finger controller configured to determine the operation of each finger according to the AGC locking signal output from the AGC locking detection unit.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. At this time, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, by which the technical spirit of the present invention and its core configuration and operation is not limited.

In this case, the same components as the prior art are given the same names and the same reference numerals for convenience of description, and detailed description thereof will be omitted.

4A is a block diagram showing an embodiment of an AGC device according to the present invention, in which an AGC lock detector 38 is connected to an output terminal of a received signal power measurement unit 31, and an output of the AGC lock detector 38 is shown. Is input to the gain control unit 33 to adjust the parameters in the gain control unit 33.

The gain control unit 33 includes a proportional integration control unit 41 and an AGC step-size control unit 45.

That is, since the AGC device as shown in FIG. 3 has a slow adaptation speed, there is a problem in that the AGC device does not properly adapt to severe channel changes.

Therefore, in order to solve this problem, if the gain control unit 33 is configured with the proportional integral control structure as shown in FIG. 4B, the AGC is faster than the case of the satellite DMB broadcasting receiver used in the high speed mobile communication and the channel change environment. It has the effect of working adaptively and stabilizing.

The proportional integral control unit 41 receives the AGC error of the AGC error detector 32, multiplies the integral constant K _I , integrates the integrated controller 42, and outputs an integral control signal of the AGC error detector 32. A proportional controller 43 that receives an AGC error and multiplies the proportional constant K _P and outputs a proportional control signal, and an adder that adds and outputs an integral control signal of the integration controller 42 and a proportional control signal of the proportional controller 43 ( 44). The output of the proportional integral control unit 41 is output to the delta & sigma modulator 34 after the step size is adjusted by the AGC step size control unit 45. The output of the gain control unit 33 is a gain up or gain down control signal for increasing or decreasing the gain of the tuner 10.

In the present invention configured as described above, the received signal power measuring unit 31 calculates instantaneous power and average power from the received signal, and outputs the instantaneous power to the AGC error detector 32, and the average power is AGC lock. It outputs to the detection part 38.

The AGC lock detection unit 38 checks whether the received signal is within the dynamic range of the AGC and activates the AGC locking signal if it is within the operating range, indicating that the AGC is locked, and if not within the operating range, the AGC locking signal. Deactivate to indicate that the AGC is unlocked. In the AGC unlocked state, the parameters of the gain control unit 33 (for example, integral constant K _I , proportional constant K _P , step size, etc.) are adjusted so that the received signal is within the AGC operating region.

In the present invention, after setting the upper threshold value and the lower threshold value based on the reference power according to an embodiment, if the received signal is between the upper threshold value and the lower threshold value, the AGC locking signal is activated, and out of the upper threshold value or lower threshold value. Departing the threshold deactivates the AGC locking signal. For example, an upper and lower value of about 10 to 20% of the reference power may be set as an upper threshold value and a lower threshold value.

5 is a flowchart illustrating an AGC lock detection method according to an embodiment of the present invention, where ThH represents an upper threshold value, ThL represents a lower threshold value, avg_pwr1 represents an average power of a received signal, and agc_ctrl1 represents an AGC locking signal.

In the present invention, when the AGC locking signal agc_ctrl1 is 1, AGC is locked as an active state, and 0 is AGC unlocked as an inactive state.

That is, if the average power of the received signal (avg_pwr1) is input from the received signal power measuring unit 31 is compared whether or not greater than the upper threshold value (ThH) (step 51). If the average power (avg_pwr1) of the received signal is not greater than the upper threshold ThH, it is compared whether it is smaller than the lower threshold ThL (step 52).

If the average power of the received signal (avg_pwr1) is not less than the lower threshold ThL means that the average power (avg_pwr1) of the received signal is within the AGC operating range. Accordingly, the unlock_cnt1 value is set to 0 (step 53), and the AGC locking signal (agc_ctrl1) is activated to 1 (step 54).

On the other hand, if it is determined in step 51 that the average power (avg_pwr1) of the received signal is greater than the upper threshold (ThH) or less than the lower threshold (ThL) in step 52, the average power (avg_pwr1) of the received signal is the AGC operation region. If outside of the case.

In this case, the unlock_cut1 value is increased (step 55). Then, it is compared whether the increased unlock_cut1 value is larger than the preset error value err (step 56). If the unlock_cnt1 value is greater than the predetermined error value err, the AGC locking signal acg_ctrl1 is inactive to 0 (step 57).

In this case, when the average power of the received signal is out of the upper threshold value or the lower threshold value, the AGC locking signal is not inactivated immediately, and the monitoring time has a predetermined time until the unlock_cnt1 value has a preset value (err). If power fluctuations are temporary, the AGC can recover itself, allowing normal operation within a short time. On the contrary, if the power change is reflected immediately, the AGC needs to be re-initialized and operated, so the system may be reversed. Therefore, an appropriate value (err) for the monitoring time should be accompanied.

The active or inactive AGC locking signal is output to the gain control unit 33. If the AGC locking signal is inactive, the gain control unit 33 recognizes that the AGC unlocking is performed, and the parameters (for example, the integral constant K _I , the proportional constant K _P , the AGC step size, etc.) to make the received signal AGC lock. ). That is, in the unlocked state, the AGC gain control unit 33 adjusts the bandwidth of the AGC so as to become a lock. At this time, if the AGC locking signal is in an inactive state, the tuner 10 may be reset. This is because AGC malfunction may occur even if the tuner 10 is wrong.

6 is a schematic diagram of a satellite DMB receiver to which two-path antenna diversity is applied according to the present invention, in which path 1 and path 2 exist by two-path antenna diversity. That is, the first data processor 610 for processing the signal of path 1, the first AGC lock detector 620 for detecting the AGC lock of the first data processor 610, and the second data processor for processing the signal of path 2 ( 630, a second AGC lock detector 640 that detects an AGC lock of the second data processor 620, and a finger controller that controls a finger operation according to AGC lock signals of the first and second AGC lock detectors 620 and 640. It consists of 650.

The first data processor 610 includes a tuner 611, an AGC unit 612, and an A / D converter 613. The second data processor 630 also has the same structure as the first data processor 610, and differs from each other in that the antennas receive signals only.

Detailed configurations and operations of the AGC units 612 and 632 of the first and second data processing units 610 and 630 are the same as those of the AGC apparatus of FIG.

Similarly, the first and second AGC lock detectors 620 and 640 detect the AGC lock through the process shown in FIG. 5.

5 is a flowchart illustrating the operation of one AGC lock detector. As shown in FIG. 6, in the mobile broadcast receiver to which 2-path antenna diversity is applied, the lock detection process of FIG. 5 is performed by the first and second AGC lock detectors 620 and 640. Is performed in each.

Let the first AGC locking signal output from the first AGC lock detector 620 be agc_ctrl1 and the second AGC locking signal output from the second AGC lock detector 640 be agc_ctrl2.

The first AGC locking signal agc_ctrl1 is output to the gain control unit, tuner 611, and finger control unit 650 of the first AGC unit 612. Similarly, the second AGC locking signal agc_ctrl2 is output to the gain control unit, tuner 631, and finger control unit 650 of the second AGC unit 632.

If the first AGC locking signal agc_ctrl1 is in an inactive state, that is, unlocked, the tuner 611 is reset, and the gain control unit of the first AGC unit 612 adjusts the bandwidth of the AGC to lock.

If the second AGC locking signal agc_ctrl2 is in an inactive state, that is, unlocked, the tuner 631 is reset, and the gain control unit of the second AGC unit 632 adjusts the bandwidth of the AGC to lock. For example, AGC bandwidth may be adjusted by adjusting parameters in the gain controller, for example, an integral constant K _I , a proportional constant K _P , and an AGC step size.

Meanwhile, the finger controller 650 determines the operation by combining the first and second AGC locking signals as shown in Table 1 below.

     00     01     10     11  agc_ctrl1   Unlock   Unlock     Lock     Lock  agc_ctrl2   Unlock     Lock   unlock     Lock

For example, when the first AGC locking signal agc_ctrl1 indicates an unlocked state, the first AGC blocking signal agc_ctrl1 blocks an input of data output from the first data processing unit 611 or does not use it when combining data with another finger.

When the first AGC locking signal agc_ctrl1 indicates the locking state, the first AGC locking signal agc_ctrl1 receives data from the first and second data processing units 610 and 630 to perform normal operation.

As described above, in the present invention, even when a satellite DMB receiver to which two-path antenna diversity is applied, AGC malfunction is controlled by adjusting the AGC bandwidth when the power of the received signal exceeds a predetermined threshold in the operation of the AGC. Can be blocked in advance. In addition, the AGC bandwidth can be adjusted by adjusting the parameters of the AGC according to the change of the channel environment, thereby improving the performance of the satellite DMB receiver.

On the other hand, the terms used in the present invention (terminology) are terms defined in consideration of the functions in the present invention may vary according to the intention or practice of those skilled in the art, the definitions are the overall contents of the present invention It should be based on.

The present invention is not limited to the above-described embodiments, and can be modified by those skilled in the art as can be seen from the appended claims, and such modifications are within the scope of the present invention.

The AGC lock detection method according to the present invention described above and the effects of the mobile broadcast receiver applying the same will be described below.

First, when the power of the received signal is out of the AGC operating range, by adjusting the parameters of the AGC to bring the power of the received signal into the AGC operating region, the channel change is severe and the transmission of the gap filler, a repeater for satellite DMB, is transmitted. It is possible to prevent the AGC from falling out or malfunctioning in the change of output, shadowed area, weak electric field, and strong electric field.

Second, in the DMB receiver using two-path antenna diversity, the unlocked path signal is not used when blocking the input or combining data with other fingers, thereby improving the reception performance of the satellite DMB receiver.

Third, the performance of the satellite DMB receiver can be improved by generating control data that can adaptively change the bandwidth of the AGC according to the change in the channel environment, that is, in the strong or weak electric field.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (10)

(a) determining whether the power of the received signal is outside a preset automatic gain control (AGC) operating area; (b) determining to unlock when out of a predetermined AGC operation area and determining to AGC locking when within an AGC operation area; And and (c) adjusting the bandwidth of the AGC if it is determined to be unlocked in the step.  The method of claim 1, wherein step (a) And if the average power of the received signal is between an upper threshold value and a lower threshold value generated on the basis of the reference power, the AGC lock detection method is determined. The method of claim 1, wherein step (b) The AGC lock detection method, characterized in that the AGC unlock is determined when the average power of the received signal is not between the upper threshold value and the lower threshold value generated based on the reference power. A tuner for tuning a signal of a specific channel received through an antenna and adjusting and outputting a gain of the tuned signal according to a gain control signal; A power measuring unit calculating a power of a received signal output from the tuner; An AGC lock detector configured to generate an AGC locking signal indicating that the signal power calculated by the power measuring unit is unlocked when it is out of a preset AGC operating area, and locked when within the AGC operating area; A gain controller configured to detect an AGC error by comparing the signal power calculated by the power measurement unit with a reference power, and generate a gain control signal with a bandwidth adjusted by proportionally integral control of the detected AGC error according to the AGC locking signal; And And a delta-sigma modulation and filter unit for analogizing the gain control signal output from the gain control unit, filtering only the low range part, and outputting the gain control signal to the tuner as a gain control signal. The method of claim 4, wherein the AGC lock detection unit And if the average power of the received signal is between an upper threshold value and a lower threshold value generated based on the reference power, the mobile broadcast receiver is determined to be within an AGC operating range. The method of claim 4, wherein the AGC lock detection unit And if the average power of the received signal is not between the upper threshold value and the lower threshold value generated based on the reference power for a predetermined time, the mobile broadcast receiver according to the AGC unlock. The method of claim 4, wherein the gain control unit And when the AGC locking signal indicates that the signal is unlocked, varying at least one of an integral constant, a proportional constant, and a step size to adjust a bandwidth of a gain control signal. 5. The apparatus of claim 4, wherein the tuner is And resetting when the AGC locking signal is unlocked. In the mobile broadcast receiver using a plurality of antennas to receive a mobile broadcast signal for each finger, A data processor is provided as many as the number of antennas, and each data processor receives a signal of a specific channel through a corresponding antenna to perform AGC and digitizes; AGC lock detection units are provided as many as the number of data processing units, and each AGC lock detection unit is unlocked when the average power of the signal received by the data processing unit is out of the preset AGC operation region, and locks when the AGC lock detection unit is within the AGC operation region. Generate a signal; And a finger controller configured to determine the operation of each finger according to the AGC locking signal output from the AGC locking detection unit. The method of claim 9, And a data processing unit indicating that the AGC locking signal is unlocked, and resetting the tuner and adjusting the AGC bandwidth.

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