KR20020014544A - Apparatus and method for carrier recovery - Google Patents

Abstract

PURPOSE: A restoring device of a carrier is provided to promote the optimum carrier restoration by calculating the maximum/minimum values from the output of a loop filter and detecting the fixed quantity of FM(Frequency Modulation) hum with the difference. CONSTITUTION: An FM hum detector(400) consists of an FM hum calculator(401) detecting the fixed quantity of FM hum from units by receiving the frequency offset of a carrier from a loop filter(300) and the FM hum from a digital broadcasting receiver, a comparator(402) comparing the output of the FM hum calculator with pre-saved reference FM hum, and a reliability counter(403) checking and outputting the reliability of the comparator to a lock detector(500). The fixed quantity of FM hum is detected by a minimum-maximum algorithm, and the bandwidth of the loop filter is set in proportion to the fixed quantity. Therefore, the restoration capability of FM hum is improved.

Description

Apparatus and method for carrier recovery

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital broadcast receiver, and more particularly, to a carrier recovery apparatus and method for detecting an FM hum in a carrier recovery bush.

Digital broadcasting reception technology, which is currently divided into various media (terrestrial wave, cable, satellite), is being developed as an integrated system structure for integrated digital broadcasting in the future. In particular, the transmission system of a digital TV (eg, HDTV) transmits data having a high bit rate of about 20 Mb / s or more through a limited band, that is, 6 MHz, so that the modulation / demodulation / modulation / modulation / bandwidth is good. Demodulation) method is required. In addition, a channel equalizer technique is required to compensate for non-ideal characteristics of the channel such as symbol / carrier recovery technique for symbol and carrier recovery, multi-path, and Doppler effect. In addition, an efficient channel decoding method is used to reliably transmit noise.

In this case, the integrated multimedia digital broadcast receiver is largely classified into three reception methods as follows.

1) Terrestrial broadcast reception method:

VSB (Vestigial Side Band, SSB, ATSC American Style)

Orthogonal Frequency Division Multiplexing (DSB, European Type)

2) Cable broadcast reception method:

Quadrature Amplitude Modulation (QAM)

3) Satellite broadcasting reception method:

Quadrature Phase Shift Keying (QPSK)

According to these three reception methods, elements such as an analog receiver, a signal synchronization method (symbol recovery / carrier recovery), a channel equalization method, a matched filter, and a channel decoding method are composed of different element technologies.

1 is a block diagram illustrating a general multimedia digital broadcast receiver. The tuner 101 selects only a specific channel frequency desired by a user from a received RF frequency, and then fixes a signal of an RF band carried on the channel frequency. Transition to band (IF (usually 44MHz or 43.75MHz widely used)) and filter out other channel signals as appropriate.

The output signal of the tuner 101, which lowers the spectrum of an arbitrary channel to a fixed primary IF band, is a surface acoustic wave (SAW) filter 102 employed as a function of removing adjacent channel signals and removing noise signals. Will pass through.

At this time, the digital broadcast signal, for example, since all information is present in the band of 6 MHz from the intermediate frequency of 44 MHz, the SAW filter 102 removes all remaining sections except for the 6 MHz band in which the information exists from the output of the tuner 101. After that, it is output to the analog-to-digital (A / D) converter 103.

The A / D converter 103 samples the output of the SAW filter 102 at a fixed sampling frequency, digitizes it, and outputs the digitized signal to a resampler 104 for conversion into a symbol recovered signal. .

The resample unit 104 outputs to the matching filter 105 by interpolating in the direction of reducing the error between the digitized signal and the signal.

The matched filter 105 filters the signal output in synchronization with the symbol in the resampler 105 to readjust the SNR at the symbol position to the maximum, and outputs the result to the phase divider 106.

The phase divider 108 separates the passband digital signal filtered and output from the matched filter 105 into I and Q passband digital signals, and then outputs the passband digital signal to the carrier recovery unit 107. The carrier recovery unit 107 demodulates the I, Q passband digital signal into a carrier with carrier recovery to generate an I, Q baseband digital signal from which frequency offset and phase noise have been recovered. 108).

The channel equalization and decoding unit 108 removes the inter-symbol interference (ISI) due to the multipath included in the I, Q baseband signals recovered by the carrier recovery unit 107, and then It removes the scattering noise and the scattering noise existing on the channel included in the interference canceled signal.

FIG. 2 is a block diagram illustrating a general configuration of the carrier recovery unit 107 and illustrates an example of recovering a carrier of a signal transmitted in a QAM scheme.

That is, the I, Q passband digital signals output from the phase divider 106 are input to the first and second complex multipliers 201 and 202, respectively. The first complex multiplier 201 multiplies the I passband digital signal by a cosine wave COSφ generated by a numerical controlled oscillator (NCO) 207 to convert the I passband digital signal into an I baseband digital signal. The second complex multiplier 202 converts the Q passband digital signal into a Q baseband digital signal by multiplying the Q passband digital signal by the sinusoidal wave SINφ generated by the NCO 207.

The outputs of the first and second complex multipliers 201 and 202 are output to the decision unit 203, the lock detector 204, and the phase / frequency error detector 205, respectively.

The determination unit 203 generates an I, Q determination signal constellation corresponding to each signal level of the I, Q demodulation signal constellations output from the first and second complex multipliers 201 and 202 so that the phase / frequency error detection unit 205 To the lock detection unit 204.

For example, the determination unit 203 generates a decision signal constellation by determining that the baseband digital signal demodulated in the QAM constellation is a signal in the first quadrant if the baseband digital signal is within the determination region in the first quadrant.

The phase / frequency error detection unit 205 uses the I, Q baseband digital signal output from the first and second complex multipliers 201 and 202 and the I, Q determination signal constellation generated by the determination unit 203. The error is detected and then output to the loop filter 206.

That is, the phase / frequency error detection unit 205 obtains a difference between the phase of the I, Q demodulated signal constellation and the phase of the I, Q determination signal constellation, and the two phase differences are phase errors.

The loop filter 206 uses a general first-order baseband loop filter, accumulates the phase error output from the phase / frequency error detection unit 205 to generate an intermediate frequency that is a sum of frequency offset and phase jitter, and then NCO ( 207). The NCO 207 generates a sine wave and a cosine wave having an intermediate frequency generated by the loop filter 206 as a center frequency, and the cosine wave COSφ is the first complex multiplier 201, and the sine wave SINφ is the second complex multiplier ( 202).

At this time, gear shifting of the filter bandwidth of the loop filter 206 is automatically performed by the lock control signal LD [2: 0] of the lock detector 204. That is, the lock detector 204 switches the noise bandwidth of the loop filter 206 by using the I, Q demodulation signal constellation and the I, Q determination signal constellation, for example.

As such, the carrier recovery unit 107 recovers (acquires / tracks) corresponding noise (frequency offset, phase noise, FM hum) included in the received signal to improve the BER (Bit Error Rate) performance of the system. The phase error detection algorithm uses a method of switching from blind mode to decision-directed mode and gradually narrowing the noise bandwidth of the loop filter. This method is called gear shifting. That is, the carrier recovery unit 107 quickly acquires / acquires hundreds of KHz frequency offset, phase jitter, and FM hum generated from a tuner or an RF oscillator. Tracking requires accurate data recovery. In particular, efficient recovery (acquisition and tracking) of the corresponding noise (frequency offset, phase noise, FM Hum) is one of the key technologies in the development of optimized multimedia digital broadcast receivers.

In addition, a criterion for determining whether the corresponding noise is correctly removed is required, and the lock detection unit 204 is generally used as a judgment tool.

Here, FM Hum (Residual Frequency Modulation) is usually a cable channel up-converters, satellite receivers, cable television channel modulators that incorporate synthetic localized oscillators. modulators, which occur in the power supply frequency pickup of many headed modulators. In addition, FM Deviation in NTSC signal occurs like Hum modulation.

At this time, due to the increased use of sensitive oscillators of the cable channel up converter, satellite receiver, cable TV channel modulator, and head modulator equipment, the sensitivity of the tuner to the FM Hum becomes an important factor in determining the performance of the receiver. It must be determined during receiver design. While these devices typically have a 60 Hz FM Hum as the supply noise, digital broadcast receivers are designed to capture and track even peak-to-peak tens to hundreds of Khz FM Hum at least 120 Hz. The carrier recovery unit 107 of the components of the digital broadcast receiver performs the function of capturing and tracking the FM Hum.

3A to 3C show frequency characteristics of FM Hum of a synthesis frequency (SF) of equipment generating FM Hum noise. That is, FIG. 3A is a spectrum of a synthesis frequency in which FM Hum of Peak-to-peak OKhz of 60 Hz exists, and it can be seen that spurious FM Hum signals having a period of 60 Hz are added to the synthesis frequency. In addition, FIG. 3B is a spectrum of a synthesis frequency in which FM Hum of Peak-to-Peak OKhz of 120 Hz exists, and it can be seen that spurious FM Hum signals having a period of 120 Hz are added to the synthesis frequency. In addition, FIG. 3C is a spectrum of a synthesis frequency in which FM Hum of Peak-to-Peak 80Khz of 120Hz exists, and that pseudo FM Hum signals having a period of 120Hz are added to the synthesis frequency over Peak-to-Peak 80Khz. Able to know.

4A to 4C show a convergence curve depicting, in a time domain, a process in which the carrier recovery unit 107 of the digital broadcast receiver recovers (captures and tracks) an FM Hum generated from a device. That is, Figure 4a is a convergence curve of the carrier recovery unit 107 when the FM Hum of the Peak-to-Peak OKhz of 60Hz, Figure 4b is a carrier recovery unit of FM Hum of the Peak-to-Peak OKhz of 120Hz 4C is a convergence curve of the carrier recovery unit 107 when the FM Hum of Peak-to-Peak 160Khz of 120Hhz is present.

In general, broadcast equipment ages as performance progresses. Therefore, the carrier recovery unit 107 of the digital broadcast receiver should be able to recover the FM Hum regardless of the performance aging of the broadcast equipment. However, it can be said that it is virtually impossible for all the carrier recovery units 107 to recover the infinite FM Hum.

As in the case of FIGS. 4A and 4B, when there is a very small amount of FM Hum corresponding to approximately less than several tens of Khz peak-to-peak, the carrier recovery unit 107 typically recovers the FM Hum without a separate FM Hum detector. can do. However, in order to recover the FM Hum reaching the Peak-to-Peak hundreds of Khz as in the case of FIG. The bandwidth of 206 must be adjusted.

At this time, the lock detection unit 204 of the carrier recovery unit 107 determines the recovery processing sequence (acquisition 1-> acquisition 2-> acquisition 3-> tracking) as shown in Figure 5, and at the same time the loop filter corresponding to each step ( 206) to automatically adjust the bandwidth. However, the lock detector 204 merely serves to determine the presence or absence of a phase error, and cannot determine the FM hum of quantitative magnitude.

Therefore, the lock detector 204 is a loop filter proportional to the quantitative size of the FM Hum in the tracking mode corresponding to the final stage of the recovery process without losing the threshold of visibility (TOV) of the signal / noise ratio (SNR). It is impossible to determine the bandwidth of the system, resulting in tracking and capturing the FM Hum, which spans several hundred Khz of Peak-to-Peak.

For this reason, the FM Hum detector is required as a tool that can determine the bandwidth of the loop filter proportional to the quantitative size of the FM Hum without losing the TOV of the SNR in the tracking mode, which is the final stage of the lock detector 204.

As such, there is no separate device that can determine the presence and quantitative size of FM Hum. Therefore, there is a problem that the loss of TOV of the SNR due to the FM Hum recovery inevitably occurs, and the FM Hum recovery ability is degraded.

The present invention is to solve the above problems, an object of the present invention is to provide a separate device that can determine the presence and quantitative size of FM Hum, after obtaining the maximum value and the minimum value from the output of the loop filter The present invention provides a carrier recovery apparatus and method for performing optimal carrier recovery by detecting the quantitative size of FM Hum as the difference value.

1 is a block diagram of a general digital broadcast receiver

FIG. 2 is a detailed block diagram of a carrier recovery unit of FIG. 1.

3a to 3c show a typical frequency spectrum of the FM Hum of the synthesized frequency of equipment generating FM Hum noise

3A shows a spectrum of a synthesized frequency in which FM Hum of Peak-to-peak OKhz of 60 Hz is present

Figure 3b is a spectrum of the synthesis frequency in the presence of FM Hum of Peak-to-Peak OKhz of 120Hz

Figure 3c is a spectrum of the synthesized frequency in the presence of FM Hum of Peak-to-Peak 80Khz of 120Hz

4A to 4C are general convergence curves illustrating a process of recovering an FM hum generated in a device by a carrier recovery unit of the digital broadcast receiver in a time domain;

4A shows a convergence curve of a carrier recovery unit in the presence of FM Hum of Peak-to-Peak OKhz of 60 Hz.

4B shows a convergence curve of a carrier recovery unit in the presence of FM Hum of Peak-to-Peak OKhz of 120Hhz.

4c shows a convergence curve of a carrier recovery unit in the presence of an FM hum of a peak-to-peak 160 kHz of 120 hz

5 is a flowchart illustrating a transition mode of an operation mode and a loop filter bandwidth of the phase / frequency error detector according to the operation mode of the lock detector of FIG.

Figure 6 is a schematic diagram showing the relationship between the loop filter and the FM Hum detection unit according to the present invention

7 is a detailed block diagram of a loop filter and an FM Hum detection unit according to the present invention.

8 is a control flowchart illustrating a transition process of a tracking step of a carrier recovery unit by an interlocking operation of an FM Hum detector and a lock detector according to the present invention;

9 is a convergence curve of the peak-to-peak 160Khz FM Hum @ 120Hz of the carrier recovery unit applying the FM Hum detection unit according to the present invention

Explanation of symbols for main parts of the drawings

300: loop filter 400: FM Hum detector

401: FM Hum calculator 401-1: Maximum value calculator

401-2: minimum value calculator 401-3: first delay unit

401-4: second delay unit 401-5: subtractor

402: comparator 403: reliability counter

500: lock detection unit

The carrier recovery apparatus according to the present invention for achieving the above object, switching the noise bandwidth in accordance with the lock control signal, the frequency offset of the carrier ( And a loop filter for outputting the FM Hum (± FM Hum) introduced into the digital broadcasting receiver, and the output of the loop filter. FM Hum detector for detecting the quantitative size of the FM Hum by obtaining the maximum value and the minimum value from the ± FM Hum, and outputting a control signal proportional to the quantitative size, and tracking step of the carrier recovery unit according to the control signal of the FM Hum detector And a lock detector for determining a transition of the signal and outputting a lock control signal for selecting the noise bandwidth of the loop filter to the loop filter according to the tracking step.

The FM Hum detector detects the maximum value and the minimum value from the output of the loop filter and then subtracts the minimum value from the maximum value to detect the quantitative size of the FM Hum introduced into the digital broadcast receiver, and the FM And a comparator for comparing the quantitative size of the FM Hum output from the Hum calculator with a pre-stored reference FM Hum and outputting a control signal for determining the bandwidth of the loop filter based on a comparison result to the lock detector. .

The FM Hum calculator detects a maximum value and a minimum value in symbol units, and a sample period of the maximum value and minimum value is performed in 120 Hz units.

In the carrier recovery method of the digital broadcasting receiver according to the present invention, the first to third reference FM Hum value (first reference FM Hum value> second reference FM Hum value> third reference FM Hum value) is set in advance after the frequency. When the acquisition is made, transitioning to the first stage for phase tracking, and the first tracking, finds the maximum and minimum values from the output of the loop filter, and then subtracts the minimum value from the maximum value to detect the quantitative size of the FM Hum. And comparing the quantitative magnitude of the FM Hum with the first reference FM Hum value to determine whether it is in the first stage of tracking or the second stage of tracking, and the second stage of tracking again includes the maximum value from the output of the loop filter. After finding the minimum value, subtract the minimum value from the maximum value to detect the quantitative size of the FM Hum, and compare the quantitative size of the FM Hum with the first to third reference FM Hum values to determine whether it is in the second stage of tracking. Determining whether to transition to step 1 or tracking 3, and the tracking 3 is to obtain the maximum value and the minimum value from the output of the loop filter, and then subtract the minimum value from the maximum value to detect the quantitative size of the FM Hum. And comparing the quantitative size of the FM Hum with the first to third reference FM Hum values, and determining whether to be in the tracking 3 step or the tracking 1 step or the tracking 2 step.

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, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The carrier recovery unit, which is generally settled in multi-media digital broadcasting receivers such as VSB / PSK / QAM, performs peak-to-peak tens of kilohertz FM hum generated by tuners, cable channel up converters, satellite receivers, cable TV channel modulators, and head modulator equipment. Acquisition / Tracking should be quick. It also requires reliable acquisition / tracking operations for low SNR and severe channel ISI (Ghost).

The acquisition / tracking performance of the carrier recovery unit is generally determined by a phase / frequency error detector algorithm and a PLL implementation method. Determining the bandwidth of a PLL proportional to the quantitative size of the FM Hum is a very important factor in capturing and tracking a serious FM Hum without loss of TOV in the SNR.

In order to realize this, a tool for determining the quantitative size of the FM Hum is required, and the FM Hum detector of the present invention performs such a role.

That is, the present invention determines the quantitative size of the FM Hum introduced into the digital broadcast receiver with the two difference values after obtaining the minimum-maximum value from the output of the loop filter for detecting the frequency offset of the carrier, and determining the quantitative size of the FM Hum. In order to select the bandwidth of the loop filter in proportion.

FIG. 4 is a block diagram illustrating FM Hum detection in a carrier recovery unit of a digital broadcast receiver according to the present invention. ) And a loop filter 300 for outputting the FM Hum (± FM Hum) introduced into the digital broadcasting receiver, and the output of the loop filter 300. FM Hum detector 400 for detecting the quantitative magnitude of the FM Hum by detecting the minimum and maximum values from the FM Hum and outputting a control signal proportional to the quantitative magnitude, according to the control signal of the FM Hum detector 400 The lock detection unit 500 determines a transition of the tracking step of the recovery unit and outputs a control signal for selecting the bandwidth of the loop filter 300 to the loop filter 300 according to the tracking step.

7 is a detailed block diagram of the loop filter 300 and the FM Hum detector 400. The FM Hum detector 400 is a frequency offset of the carrier wave from the loop filter 300. And FM Hum (± FM Hum) input to the digital broadcast receiver to detect the quantitative size of the FM Hum generated from the equipment, the FM Hum calculator 401, the output of the FM Hum calculator 401 and A comparator 402 for comparing the pre-stored reference FM Hum, and a reliability counter 403 for checking the reliability of the comparator 402 and outputting the reliability to the lock detector 500.

The FM Hum calculator 401 calculates a maximum value from the output of the loop filter 300, a maximum value calculator 401-1, a minimum value calculator 401-2 for calculating a minimum value, and the maximum value. A first delayer 401-3 sampling at a 120Hz period, a second delayer 401-4 sampling the minimum value at a 120Hz period, and a second delayer 401 at the output of the first delayer 401-3. And subtracter 401-5 to detect the quantitative size of the FM Hum. That is, the maximum value calculator 401-1 and the minimum value calculator 401-2 operate by a symbol clock, and the first and second delayers 401-3, 401-4 operate at a 120 Hz clock. It works by

In FIG. 7 configured as described above, the loop filter 300 includes first and second selectors 301 and 303, an adder 302 and 304, and a delayer 305 that output the selected bandwidth, and the delay with the adder 304. The generator 305 is a general integrator that accumulates the output of the second selector 303 in symbol units.

That is, the loop filter 300 has a corresponding frequency offset ( In order to capture, the value of the bandwidth selected according to the control signal LD [2: 0] of the lock detector 500 is accumulated and the corresponding frequency offset ( ) And the frequency offset ( FM Hum (± FM Hum) generated from the frequency offset (Δf) and the cable channel up converter, the satellite receiver, the cable TV channel modulator, and the head modulator equipment. ) Is output to the FM Hum detection unit 400.

Then, the maximum value calculator 401-1 of the FM Hum calculator 401 of the FM Hum detector 400 receives the output (Δf ± FM Hum) of the loop filter 300 to a maximum value in symbol units. After calculating Max (Δf ± FM Hum), it outputs to the first delay unit 401-3, and the minimum value calculator 401-2 outputs the output of the loop filter 300 (Δf ± FM Hum). The minimum value Min (Δf ± FM Hum) is calculated in symbol units and then output to the second delay unit 401-4. The first and second delayers 401-3 and 401-4 delay the maximum value Max (Δf ± FM Hum) and minimum value Min (Δf ± FM Hum) by one symbol to the subtractor 401-5. In this case, the maximum and minimum sample periods of the first and second delayers 401-3 and 401-4 are performed in units of 120 Hz. The reason for sampling in units of 120 Hz is that 120 Hz FM Hum is generated from the devices as described above, and FM Hum can be modeled as a sinusoidal wave having a frequency of 120 Hz. Subtract the minimum value Min (Δf ± FM Hum) from the maximum value Max (Δf ± FM Hum) sampled in 120Hz unit in the subtractor 401-5, and then remove the frequency offset Δf. Two-peak FM Hum is available.

The output of the FM Hum calculator 401 is input to the comparator 402. The comparator 401 compares the magnitude of the quantitative peak-to-peak FM hum calculated by the FM hum calculator 401 with a pre-stored reference peak-to-peak FM hum in 120 Hz sample units. From the result, a control signal for determining the loop filter bandwidth of the carrier recovery unit 107 is generated and output to the reliability counter 403.

The reliability counter 403 is used to improve the reliability of the control signal generated by the comparator 402. That is, the reliability counter 403 outputs the control signal to the lock detector 500 only when the control signal output from the comparator 402 maintains the same value for a predetermined number of times.

The lock detection unit 500 determines the transition of the tracking step of the carrier recovery unit 107 according to the control signal output from the reliability counter 403, and also determines the loop filter bandwidth according to the tracking step. [2: 0] is output to the first and second selectors 301 and 303 of the loop filter 300.

8 is a control flowchart illustrating a transition process of a tracking step of a carrier recovery unit by an interlocking operation between the FM Hum detector 400 and the lock detector 500. For example, assume that the reference peak-to-peak FM Hum is set to three values of High, Middle, and Low. Here, the reference peak-to-peak FM Hum may be set in plural, which may be changed by the designer.

That is, the first, second, and third stages 601 represent the stages of the general lock detection unit 500. In the third stage, the lock detector 500 transitions to the first stage 602.

In the tracking step 1 602, the FM Hum detection unit 400 selects the bandwidth of the loop filter 300 as a large bandwidth by default to track a serious FM Hum. Here, the reason why the large bandwidth is selected by default is that the small bandwidth does not endure tracking 1 and transitions to the acquisition phase.

In the tracking step 1 (602), the FM Hum detector 400 calculates the quantitative size of the FM Hum introduced into the receiver in units of 120 Hz using the proposed Min-Max algorithm, and whether the tracking is in the tracking step 1 or 2 steps. Decide if you want to transition. That is, it is compared whether the quantitative size of the FM Hum calculated in the tracking step 1 602 is greater than the 'high' set as the reference peak-to-peak FM Hum value (603). If it is determined that the quantitative size of the FM Hum calculated in step 603 is greater than the 'high' value, the tracking 1st step 602 is maintained, and if it is determined that it is not large, the process transitions to the tracking 2nd step 604. At this time, the bandwidth selected in the first tracking step 602 is large, and the TOV loss of the SNR is high.

On the other hand, in the tracking step 2 (604), the FM Hum detection unit 400 calculates the quantitative size of the FM Hum introduced into the receiver in units of 120 Hz using the proposed Min-Max algorithm, and whether it is in the tracking step 2, tracking 3 Decide if you want to transition to Step 1 or Track 1 That is, it is compared whether the quantitative size of the FM Hum calculated in the tracking 2 step 604 is smaller than the 'high' value set as the reference peak-to-peak FM Hum value and larger than the 'middle' value (605). If the condition of step 605 is satisfied, tracking 2 step 604 is continued, and if the condition of step 604 is not satisfied, if the calculated quantitative size of the FM Hum is greater than the 'high' value (606), or ' Compare whether it is less than the low 'value (607). If it is determined in step 606 that the quantitative size of the FM Hum is greater than 'high', or if it is determined in step 607 that it is greater than the 'low' value, then the process transitions to tracking 1 step 602. In addition, if it is determined that the quantitative size of the FM Hum calculated in step 606 is not greater than 'high', or is determined to be smaller than the 'low' value in step 607, the process proceeds to tracking 3 step 608. The bandwidth selected in step 2 is middle, and the TOV loss of the SNR is also medium.

Similarly, in the tracking step 3 (608), the FM Hum detection unit 400 calculates the quantitative size of the FM Hum introduced into the receiver in units of 120 Hz using the proposed Min-Max algorithm, and whether the tracking step is in step 3, tracking step 1 Or decide to transition to step 2 of tracking. That is, it is compared whether the quantitative size of the FM Hum calculated in the tracking 3 step 608 is smaller than the 'low' value set as the reference peak-to-peak FM Hum value (step 609). If the condition of step 609 is satisfied, the tracking step 3 (608) is continued. If the condition of step 609 is not satisfied, the calculated quantitative size of the FM Hum is set to a reference peak-to-peak FM Hum value. It is compared whether it is smaller than the 'high' value and larger than the 'middle' value (610) or compares whether it is larger than the 'high' value (611). If it is determined that the quantitative size of the FM Hum calculated in step 610 is smaller than the 'high' value and larger than the 'middle' value, the process proceeds to tracking step 2 (604), and if the condition is not satisfied, tracking 3 step (608) is performed. Keep it up. In addition, if it is determined that the quantitative size of the FM Hum calculated in step 611 is greater than the 'high' value, the process proceeds to the first tracking step 602, and if the condition is not satisfied, the third tracking step 609 is maintained. . In this case, the bandwidth selected in the tracking step 3 is small and the TOV loss of the SNR is low.

In conclusion, the size of the bandwidth of the loop filter 300 is determined in the order of tracking step 1> tracking step 2> tracking step 3, and the minimization of the TOV loss of SNR is determined in order of tracking step 1 <tracking 2 step <tracking 3 steps. do.

9 shows an embodiment of the peak-to-peak FM Hum @ 120Hz convergence characteristic curve of the carrier recovery unit to which the FM Hum detection unit 400 proposed in the present invention is applied. After the convergence curve captures the frequency offset and FM Hum, it can be seen that the tracking curve tracks the FM Hum in the form of a sine wave having a peak-to-peak 160Khz magnitude and 120Hz.

Meanwhile, the FM Hum detector according to the present invention can be applied to not only a single all digital broadcast receiver but also a composite VSB / PSK / QAM terrestrial / satellite / cable digital receiver.

As described above, according to the carrier recovery apparatus and method according to the present invention, a quantitative size of the FM Hum is detected using a Min-Max algorithm, and a control signal is generated to select a loop filter bandwidth in proportion to the quantitative size. By doing so, the following effects are obtained.

That is, it is possible to determine the existence and quantitative size of the FM Hum, thereby eliminating the loss of TOV of the SNR due to the FM Hum recovery, it is possible to improve the recovery capacity of the FM Hum. In particular, the carrier recovery unit can easily perform the acquisition and tracking of serious FM Hum, and can be used in conjunction with the lock detector of the carrier recovery unit to improve the reliability of the FM Hum recovery function of the carrier recovery unit.

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 (9)

A carrier recovery apparatus of a digital broadcasting receiver for demodulating a passband digital signal of a specific channel into a baseband digital signal by demodulating the frequency band and the phase noise into a recovered baseband digital signal. The noise bandwidth is switched in accordance with the lock control signal, and the frequency offset of the carrier ( A loop filter for outputting FM Hum (± FM Hum) introduced into the digital broadcasting receiver; Output of the loop filter An FM Hum detector for detecting a quantitative magnitude of the FM Hum by obtaining a maximum value and a minimum value from ± FM Hum and then outputting a control signal proportional to the quantitative magnitude; And And a lock detector for determining a transition of the tracking step of the carrier recovery unit according to the control signal of the FM Hum detector and outputting a lock control signal for selecting the noise bandwidth of the loop filter to the loop filter according to the tracking step. Carrier recovery apparatus characterized in that the. The method of claim 1, wherein the loop filter The switching of the filter bandwidth according to the lock control signal of the lock detection unit selects one of the pre-stored bandwidths and accumulates the value of the selected bandwidth to obtain a corresponding frequency offset ( ) And output the signal to the FM Hum detection unit together with the FM Hum (± FM Hum) introduced into the digital broadcasting receiver. The method of claim 1, wherein the FM Hum detection unit An FM Hum calculator for detecting a maximum value and a minimum value from an output of the loop filter and subtracting the minimum value from the maximum value to detect the quantitative size of the FM Hum introduced into the digital broadcast receiver; Comparing the quantitative size of the FM Hum output from the FM Hum calculation unit and the pre-stored reference FM Hum and a control signal for determining the bandwidth of the loop filter according to the comparison result to the lock detection unit Carrier recovery apparatus. The method of claim 3, wherein And a reliability counter for counting the output of the comparator and confirming the reliability of the comparator. The method of claim 3, wherein the FM Hum calculation unit The maximum and minimum values are detected in symbol units, and the sample period of the maximum and minimum values is performed in units of 120 Hz. A loop filter for detecting the frequency offset of the carrier, and the carrier recovery method of the digital broadcasting receiver for demodulating the passband digital signal of a specific channel into a constant / cosine wave to perform frequency acquisition and phase tracking to convert to a baseband digital signal In After the first to third reference FM Hum values (the first reference FM Hum value> the second reference FM Hum value> the third reference FM Hum value) are set in advance and then the frequency acquisition is performed, the process shifts to the primary stage for phase tracking. Doing; In the tracking step 1, the maximum value and the minimum value are obtained from the output of the loop filter, and the minimum value is subtracted from the maximum value to detect the quantitative size of the FM Hum, and the quantitative size of the FM Hum is compared with the first reference FM Hum value. Determining whether to be in the first step of tracking or the second step of tracking; In the tracking step 2, the maximum and minimum values are obtained from the output of the loop filter, and the minimum value is subtracted from the maximum value to detect the quantitative size of the FM Hum. Comparing the FM Hum values to determine whether to be in tracking 2 or transition to tracking 1 or tracking 3; And In the tracking step 3, the maximum and minimum values are obtained from the output of the loop filter, and the minimum value is subtracted from the maximum value to detect the quantitative size of the FM Hum. And comparing the FM Hum values to determine whether to be in the third step of tracking or the second step of tracking. The method of claim 6, wherein the tracking step 1 And if the calculated quantitative size of the FM Hum is greater than the first reference FM Hum value, the tracking step 1 is maintained, and if it is not large, the carrier recovery method is shifted to tracking step 2. The method of claim 6, wherein the tracking step 2 If the calculated quantitative size of the FM Hum is less than the first reference FM Hum value and greater than the second reference FM Hum value, the tracking step 2 is continued, and if it is larger than the first reference FM Hum value, the transition to the first tracking step is performed. And if less than a third reference FM Hum value, transition to a third tracking step. The method of claim 6, wherein the tracking step 3 If the quantitative size of the calculated FM Hum is less than the third reference FM Hum value, the third tracking step is continued, and if it is less than the first reference FM Hum value and greater than the second reference FM Hum value, the transition to tracking step 2 is performed. And if greater than the first reference FM Hum value, transition to a first tracking step.