KR100425104B1 - Apparatus for recovering carrier - Google Patents

Abstract

The present invention relates to a carrier recovery apparatus of a VSB-type digital TV receiver. In particular, a gain of an digitized passband I, Q signal is adjusted so that the pilot signal included in the I, Q signal of the passband is always constant. Or by adjusting the gain of the digitized baseband I, Q signal to make the pilot signal included in the baseband I, Q signal always constant, and then performing carrier recovery to perform a severe multipath path on the transmission channel. Even in the presence of ghosts, the carrier can be recovered accurately.

Description

Carrier recovery device {Apparatus for recovering carrier}

The present invention relates to a digital TV receiver, and more particularly, to a carrier recovery apparatus for a digital TV receiver of a VSB type.

Currently, the residual sideband (VSB) method, which is adopted as a digital TV (hereinafter referred to as DTV) broadcasting standard in Korea and the United States, is to transmit a broadcast signal using a frequency allocated for conventional analog TV broadcasting. However, in order to minimize the impact on the existing analog TV broadcasting, the strength of the DTV signal is transmitted at a much smaller size than the analog TV signal strength. Of course, various coding schemes and channel equalizers are used in the DTV signal to reduce the influence of noise. However, if the situation of the transmission channel is very poor, the signal may not be properly received. In general, the DTV transmission method has the advantage of completely eliminating the noise generated on the transmission channel when receiving a broadcast, so that the screen can be viewed without any noise. However, if the transmission signal cannot be completely restored, the screen cannot be viewed at all. Should be able to receive all signals passing through any poor transmission channel.

FIG. 1 is a block diagram illustrating a general VSB digital TV receiver. When a RF (Radio Frequency) signal modulated by a VSB method is received through an antenna 101, the tuner 102 selects only a specific channel frequency desired by a user. The VSB signal of the RF band carried on the channel frequency is lowered to an intermediate frequency band (IF (typically 44 MHz or 43.75 MHz is widely used in analog TV broadcasting) and the other channel signal is properly filtered.

The output signal of the tuner 102, which converts an arbitrary channel spectrum into a passband signal of IF, 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 103 removes all remaining sections except for the 6 MHz band in which the information exists from the output of the tuner 102. It is then output to the IF amplifier 104.

The IF amplifier 104 multiplies the signal output from the SAW filter 103 by a gain value already calculated in order to always equalize the signal output to the rear A / D converter 105. Therefore, the A / D converter 105 always receives the same size signal from the IF amplifier 104 and digitizes it. The passband signal digitized by the A / D converter 105 is shifted to the baseband by the carrier recovery unit 106 and then output to the DC remover 107. In this case, the carrier signal used in the carrier recovery by the carrier recovery unit 106 is changed to a DC component having a frequency of 0 Hz after carrier recovery.

That is, the DC component is forcibly inserted into the transmission signal by the transmitter in order to enable the carrier recovery unit to perform carrier recovery. Therefore, after carrier recovery is performed, the DC component inserted in the transmitter is not necessary. Accordingly, the DC remover 107 detects and removes a DC component from the baseband signal output from the carrier recovery unit 106.

The baseband digital signal from which the DC component is removed is output to the synchronizer 109 and the channel equalizer 109.

In general, the most notable characteristics of the VSB transmission scheme proposed by the Grand Alliance (GA) are the pilot signal, the data segment synchronization signal, and the field synchronization signal. These signals are inserted and transmitted by the transmitter to improve characteristics such as carrier recovery and timing recovery.

Accordingly, the synchronization unit 108 recovers the data segment synchronization signal and the field synchronization signals that were inserted at the time of transmission from the DC-removed signal. The synchronization signals thus obtained are output to the channel equalizer 109, the phase corrector 110, and the FEC unit 111.

The channel equalizer 109 removes linear distortion of amplitude causing interference between symbols included in the baseband digital signal and ghost generated by a building or a mountain by using the baseband digital signal and a synchronization signal. The output is then output to the phase corrector 110.

The phase corrector 110 removes the residual phase noise caused by the tuner 102 from the output signal of the channel equalizer 109 and outputs the residual phase noise to the FEC unit 111. The FEC unit 111 recovers a transmission symbol from a signal from which phase noise is removed using the synchronization signals and outputs the transmission symbol in the form of a transport stream.

In this case, referring to FIG. 1, signals that have undergone all analog processing are converted into digital signals by the A / D converter 105 and then output to the carrier recovery unit 106. Therefore, all digital processing blocks after the carrier recovery unit 106 cannot operate normally unless carrier recovery is performed in the carrier recovery unit 106.

Figure 2 shows the frequency characteristics of the over-the-air signal defined in the current DTV standards of Korea and the United States. Although the center frequency fc and the pilot frequency fp are different for each channel, the center frequency is referred to as fc and the pilot frequency as fp. For example, the bandwidth of each terrestrial channel is the center frequency fc of 6 MHz, and the frequency at which the carrier signal exists on the transmission signal is called a pilot frequency fp. In this case, the term “pilot” is used instead of the carrier because the size of the carrier signal is reduced to be very small (about 13 dB) so that the DTV signal does not affect the existing analog TV signal.

Accordingly, the carrier recovery unit 106 in the DTV receiver accurately restores the position of the pilot frequency fp existing on the frequency of the transmission signal and converts it to the baseband signal.

Currently, the most common algorithm of the carrier recovery unit 106 is a frequency phase locked loop (FPLL) as shown in FIG. 3. The circuit is simple to implement and has excellent performance. That is, the carrier recovery unit 106 composed of the FPLL demodulates the pass band I, Q signal output from the A / D converter 105 into the baseband I, Q signal to lock frequency and phase.

3, the I and Q signals of the passband digitized by the A / D converter 105 are input to the mixer 301.

The mixer 301 receives a complex carrier wave, that is, a sinusoidal wave (SIN) and a cosine wave (COS), through a NCO (Numerically Controlled Oscillator) 308, and is output through the A / D converter 105. The I, Q signals in the pass band are multiplied by the I and Q signals in the pass band, respectively, to shift the I, Q signals in the pass band to I, Q signals in the base band.

The baseband I and Q signals are output to the DC canceller 107 and the baseband I signals are output to the first low pass filter 302 for carrier recovery, and the baseband Q signals are output to the second low pass. It is output to the filter 303.

In this case, the carrier recovery unit 106 for recovering the carrier only needs a signal around a frequency at which the pilot frequency fp exists among the bandwidth of 6 MHz. Accordingly, the first and second low pass filters 302 and 303 remove the remaining frequency components in which the data components exist from the I and Q signals to prevent the performance of the carrier recovery unit from being degraded by the data.

That is, in the baseband I, Q signal, the pilot signal is changed into a DC component. Strictly, it changes to the frequency component around the DC component. This is caused by the difference between the carrier frequency component of the input signal and the carrier frequency component generated at the NCO 308. Accordingly, since only the component around the DC can recover the carrier, the first and second low pass filters 302 and 303 remove the remaining data components except for the signal around the DC component.

The output of the first low pass filter 302 is input to a delay 303. The delay unit 303 delays the I signal from which the data component is removed and outputs the delayed signal to the code extractor 304. At this time, if the I signal of the pilot component output from the first low pass filter 302 passes through the delay unit 303 and the pilot does not change exactly to the DC component, a phase error corresponding to that much is generated.

Accordingly, the delay unit 303 converts the difference between the pilot frequency component of the input passband signal and the carrier frequency component of the NCO 308 into a form of phase error and outputs the result to the code extractor 304.

The code extractor 304 extracts only the sign of the signal output from the delayer 303 and outputs it to the multiplier 306. The multiplier 306 multiplies the sign of the I signal and the Q signal from which the data components are removed and outputs the phase error to the loop filter 307 as a phase error. The loop filter 307 filters and integrates an input phase error and outputs the NCO 308, and the NCO 308 generates a complex carrier (COS, SIN) proportional to the output of the loop filter 307. It is outputted to the mixer 301. The complex carrier becomes a signal closer to a carrier frequency component of a signal input more than before. Repeating this process, a carrier frequency signal, which is almost similar to the carrier frequency component of the input signal, is generated by the NCO 308 and output to the mixer 301. The mixer 301 converts the passband signal into a desired baseband signal. Transition

That is, if the frequency of the pilot signal, which is the carrier signal component present in the input pass band, and the frequency component of the carrier signal generated by the NCO 308 are exactly the same, the role of the carrier recovery unit 106 is finished. However, in the actual situation, due to the influence of the natural characteristics of the NCO 308 and the characteristics of the transmission line, they have similar frequency components, but the frequencies of the two carrier signals are not exactly matched. Accordingly, the carrier recovery unit 106 corrects the frequency components that are inconsistent with each other to change the frequency of the NCO 308 so that the frequencies of the two carrier signals match.

On the other hand, in order to make the size of the input signal of the A / D converter 105 constant at all times, the gain of the input signal is adjusted by the IF amplifier 104. Information on this can be extracted directly from the analog signal, It may be extracted from the digital block after the D converter 105 and transmitted. The signal input to the A / D converter 105 is a 6 MHz passband signal. Therefore, the IF amplifier 104 adjusts the gain so that it can always have a constant magnitude for all signals of 6MHz input to the A / D converter 105.

If there is no linear noise in the input signal, the relative size of the size of the data and the size of the pilot is always constant so that there is no influence on the carrier recovery unit 106 at all.

However, in the case of linear ghost, the size of data and relative size of pilot are changed by the delay time and phase difference of the linear noise.

4 is a diagram showing the shape of a passband frequency when the time delay of the noise is about one symbol interval. FIG. 4A shows the frequency when the phase difference is 0 °, and FIG. 4B shows the frequency when the phase difference is 180 °. Characteristic. Compared with the frequency characteristic of FIG. 2, the size of the pilot is relatively larger than that of data in the case of FIG. 4A. In contrast, in the case of FIG. 4B, the size of the pilot is smaller than the size of data.

FIG. 5 is a diagram illustrating a shape of a passband frequency corresponding to a case where a noise time delay is about 10 symbol intervals. FIG. 5A illustrates a phase difference of 0 °, and FIG. 5B illustrates a phase difference of 180 °. Frequency characteristic. Similarly, in the case of FIG. 5A, the size of the pilot is relatively larger than the size of the data. In FIG. 5B, the size of the pilot is smaller than the size of the data.

In this case, the magnitude of the signal input to the A / D converter 105 is always constant in the case of FIGS. 2, 4, and 5. Only the frequency characteristics have changed. However, the magnitudes of the pilot signals used in the carrier recovery unit 106 are all different. 2, 4A and 5A, since the pilot size of the received signal is relatively large compared to the data, the carrier recovery unit 106 does not have a big problem in extracting information on the mismatch of carriers. However, in the case of FIGS. 4B and 5B, the carrier recovery cannot be performed accurately because the magnitude of the pilot signal is small. In this case, the problem may be solved by increasing the size of the signal input to the A / D converter 105, but there is a disadvantage in that the performance of other digital processing units is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to perform carrier recovery by adjusting the gain of a pilot signal, thereby enabling accurate carrier recovery even when a linear ghost exists in a received signal. The present invention provides a carrier recovery apparatus.

1 is a block diagram of a general digital TV receiver

2 is a spectrum diagram showing the frequency characteristics of a typical airwave signal

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

4A and 4B are spectral diagrams showing the frequency characteristics of an over-the-air signal in the presence of linear noise with about one symbol delay

5A and 5B are spectral diagrams showing the frequency characteristics of an over-the-air signal in the presence of linear noise of about 10 symbol delays

6 is a block diagram illustrating a carrier recovery apparatus according to a first embodiment of the present invention.

7 is a block diagram illustrating a carrier recovery apparatus according to a second embodiment of the present invention.

Explanation of symbols for main parts of the drawings

601,701,703: mixer 602,604,702: pilot gain control unit

603,605,704,705: Low Pass Filter

606, 706: pilot gain detector 607, 707: delay

608,708: Sign Extractor 609,709: Multiplier

610,710 Loop filter 611,711 NCO

The carrier recovery apparatus according to the first embodiment of the present invention for achieving the above object is based on the passband I, Q signal by multiplying the digitized passband I, Q signal and a complex carrier proportional to the phase error, respectively. A mixer that transitions to band I and Q signals, and a pilot gain that adjusts the gain of the base band I and Q signals according to a gain up / down control signal to make the pilot included in the base band I and Q signals constant. A control unit, a filter for outputting only I, Q signals of a pilot component among I, Q signals whose gain is adjusted by the pilot gain control unit, and detecting gains of I, Q signals of pilot components output through the filter; A pilot gain detector for comparing a gain of a preset reference signal and outputting a gain up / down control signal according to a comparison result to the pilot gain adjuster; After delaying the I signal of the idle component for a predetermined time, the phase error detection unit which extracts a sign and multiplies the Q signal of the pilot component and the phase error output from the phase error detection unit are filtered and integrated and then proportional to the integrated phase error. And a filter and an oscillator for generating a complex carrier and outputting the complex carrier.

The carrier recovery apparatus according to the second embodiment of the present invention multiplies the digitized passband I signal by a cosine wave proportional to a phase error, transitions the passband I signal to a baseband I signal, and outputs the signal for symbol recovery. A mixer, a pilot gain adjusting unit for adjusting the gain of the passband I and Q signals according to a gain up / down control signal to make the pilot included in the passband I and Q signals constant; A second mixer for converting the passband I, Q signal to a baseband I, Q signal by multiplying the I, Q signal of the pass band whose gain is adjusted by the adjusting unit with a complex carrier proportional to the phase error, and the second mixer; A filter for outputting only the I and Q signals of the pilot component among the baseband I and Q signals output from the mixer, and detecting the gain of the I and Q signals of the pilot component output through the filter. After comparing the gain of the reference signal with the pilot gain detector for outputting the gain up / down control signal according to the comparison result to the pilot gain control unit, and delaying the I signal of the pilot component output through the filter for a predetermined time, Extracting and multiplying a phase error detector for multiplying the Q signal of the pilot component and a phase error output from the phase error detector, generating a complex carrier proportional to the integrated phase error, and outputting the complex carrier to the second mixer; At the same time, the cosine wave of the complex carrier is characterized by including a filter and an oscillator output to the first mixer.

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 illustrating the configuration and operation of the embodiment of the present invention, 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 the technical spirit of the present invention described above and its core configuration and operation is not limited.

FIG. 6 is a block diagram illustrating a carrier recovery apparatus according to a first embodiment of the present invention, in which carrier recovery is performed on I and Q signals of a pass band output through the A / D converter 105. FIG. A multiplier for controlling the gain of the I signal so that the size of the pilot included in the baseband I signal output from the mixer 601 is always constant. A first low pass filter 603 for passing only an I signal of a pilot component whose gain is adjusted by the first pilot gain adjusting unit 602 and the first pilot gain adjusting unit 602, and a base output from the mixer 601. The second pilot gain adjusting unit 604 for adjusting the gain of the Q signal so that the size of the pilot included in the Q signal of the band is always constant, and the gain of the pilot component whose gain is adjusted in the second pilot gain adjusting unit 604. Second low pass through Q signal only A pilot for outputting a gain control signal to the first and second pilot gain adjusters 602 and 604 after calculating the gain of the pilot signal output from the pass filter 605 and the first and second low pass filter 606. A gain detector 606, a delayer 607 for delaying the I signal of the pilot component output from the first low pass filter 603 for a predetermined time, and a code for detecting the sign of the I signal delayed at the delayer 607. A multiplier 609 that multiplies the sign of the I signal of the pilot component detected by the extractor 608 and the Q signal of the pilot component output from the second low pass filter 605 and outputs the result as a phase error. A loop filter 610 for filtering and integrating the phase error output from the multiplier 609 and a complex sine wave (COS, SIN) proportional to the output of the loop filter 610 to generate the mixer 601. Configured to include an NCO 611 to output . Here, the retarder 607, the code extractor 608, and the multiplier 609 are called phase error detectors.

In the present invention configured as described above, the mixer 601 receives a complex carrier in the form of a sine wave (SIN) and a cosine wave (COS) in which carrier recovery is performed through an NCO 611 and is output through the A / D converter 105. The I, Q signals in the pass band are multiplied by the I and Q signals in the pass band, respectively, to shift the I, Q signals in the pass band to I, Q signals in the base band.

The baseband I, Q signals are output to the DC eliminator 107 for digital processing, and at the same time, the baseband I signals are output to the first pilot gain control unit 602 for carrier recovery, and the baseband Q signals. Is output to the second pilot gain control unit 604.

The first pilot gain adjuster 602 adjusts the gain of the baseband I signal according to the gain control signal output from the pilot gain detector 606 so that the pilot size is always constant.

In addition, the second pilot gain adjuster 604 adjusts the gain of the baseband Q signal according to the gain control signal output from the pilot gain detector 606 so that the pilot size is always constant.

The gain-adjusted signals in the first and second pilot gain adjusters 602 and 604 are output to the first and second low pass filters 603 and 605, respectively.

In this case, since the carrier recovery requires only signals around a frequency in which a pilot frequency (fp) exists among 6 MHz bandwidths, the first and second low pass filters 603 and 605 may include the first and second pilot gain adjusters. From the I and Q signals output from 602, 604, the frequency component in which the pilot component is present is passed and the remaining frequency component in which the data components are present is removed. That is, the first and second low pass filters 602 and 604 are removed from the data components other than the DC component, for example, the signal around the pilot.

The I signal of the pilot component that has passed through the first low pass filter 603 is output to the pilot gain detector 606 and the delayer 607, and the Q of the pilot component that has passed through the second low pass filter 605. The signal is output to the pilot gain detector 606 and the multiplier 609.

The pilot gain detector 606 detects the gain of the pilot signal from the I and Q signals of the pilot components output from the first and second low pass filters 603 and 605. In this case, since only the pilot frequency component is included in the I and Q signals output from the first and second low pass filters 603 and 605, the gain detected by the pilot gain detection unit 606 eventually results in a gain of the pilot signal. do. The pilot gain detector 606 compares the gains of the I, Q signals of the pilot component thus detected with the gains of the I, Q signals of the reference pilot component, and generates a gain up or down signal according to the comparison result. The control signal is output to the first and second pilot gain adjusters 602 and 604. Here, the gain of the I, Q signals of the reference pilot component stored in advance for the comparison may be determined by, for example, pre-calculating an expected value when the most normal signal is input.

Accordingly, the size of the pilot included in the I and Q signals output from the first and second pilot gain adjusters 602 and 604 is always constant.

On the other hand, the delay unit 607 receives an I signal from which data components are removed from the first low pass filter 603 in order to convert a frequency error into a phase error, and then delays it for a predetermined time and then outputs it to the code extractor 608. do. At this time, when the I signal of the pilot component output from the first low pass filter 603 passes through the delay unit 607 and the pilot does not change exactly to the DC component, a phase error corresponding thereto is generated.

Accordingly, the delay unit 607 converts the difference between the pilot frequency component of the input passband signal and the carrier frequency component of the NCO 611 into a form of phase error and outputs the result to the code extractor 608.

The code extractor 608 extracts only the sign of the signal output from the delayer 607 and outputs the code to the multiplier 609. The multiplier 609 multiplies the sign of the I signal from which the data component is removed and the Q signal from which the data component is removed and outputs the phase error to the loop filter 610 as a phase error. The loop filter 610 filters and integrates an input phase error and outputs the NCO 611, and the NCO 611 generates a complex carrier (COS, SIN) proportional to the output of the loop filter 610. It is outputted to the mixer 601. The complex carrier becomes a signal closer to a carrier frequency component of a signal input more than before. When this process is repeated, a carrier frequency signal, which is almost similar to the carrier frequency component of the input signal, is generated by the NCO 611 and output to the mixer 601. The mixer 601 converts the passband signal into a desired baseband signal. Transition

Accordingly, in the first embodiment of the present invention, even when the size of the pilot is small due to linear noise as shown in FIGS. 4B and 5B, the carrier recovery is performed by adjusting the gain to a constant size at all times, whereby the size of the pilot is small. The probability of judgment can be reduced, resulting in an overall system performance improvement.

Meanwhile, the first embodiment of FIG. 6 described above is a case where the gain adjustment of the pilot is performed in the baseband.

7 is a block diagram illustrating a configuration of a carrier recovery apparatus according to a second embodiment of the present invention, in which a gain adjustment of a pilot is performed in a pass band.

Referring to FIG. 7, the I / Q signals of the passband digitized by the A / D converter 105 are output to the first mixer 701 and the pilot gain adjuster 702. The first mixer 701 multiplies the carrier recovered cosine wave (COS) output from the NCO 711 by the I signal of the pass band output from the A / D converter 105 to base the I signal of the pass band. The signal is converted to an I signal in a band and output for digital processing.

On the other hand, the pilot gain control unit 702 adjusts the gain of the pass band I, Q signal output from the A / D converter 105 according to the gain control signal of the pilot gain detector 706 and then the second Output to mixer 703. That is, the magnitude of the pilot signal included in the I and Q signals output from the pilot gain control unit 702 always has a constant size regardless of the state of the input signal.

At this time, if the gain of the pilot signal is adjusted in the pass band, the gain of the data is also changed. Therefore, when the gain-adjusted signal is output as it is for digital processing, the digital block in the later stage, for example, the channel decoding unit, cannot operate normally.

Therefore, two mixers 701 and 703 are used in FIG.

That is, the first mixer 701 multiplies the I-signal of the passband output from the A / D converter 105 by the carrier-recovered cosine wave (COS) to make a transition to the I-band of the baseband and then performs DC for digital processing. The sine wave (SIN) and the cosine wave (COS) whose carriers are recovered to the I, Q signals of the pass band whose gain is adjusted by the pilot gain control unit 702 are output to the eliminator 107. Multiply by and shift the signals to baseband I, Q signals and output them for carrier recovery. That is, the gain-adjusted signal is used only for carrier recovery and is not output for digital processing.

In this case, since the first mixer 701 only needs to output the baseband I signal, the number of gates required is about half of that of the mixer 601 of FIG. 6.

The baseband I signal output from the second mixer 703 is output to the first low pass filter 704, and the baseband Q signal is output to the second low pass filter 705. The I signal of the pilot component passing through the first low pass filter 704 is output to the pilot gain detector 706 and the delayer 707, and the Q of the pilot component passing through the second low pass filter 705 is passed. The signal is output to the pilot gain detector 706 and multiplier 709.

The pilot gain detector 706 detects a gain from the I and Q signals of the pilot components output from the first and second low pass filters 704 and 705, compares the gain with a preset reference gain, and increases or decreases the gain according to the comparison result. A down signal is generated and output to the pilot gain control unit 702.

Therefore, the size of the pilot included in the I, Q signals output from the pilot gain control unit 702 is always constant.

The delay unit 707 delays the I signal of the pilot component for a predetermined time and outputs it to the code extractor 708 in order to convert the frequency error into a phase error, and the code extractor 708 only outputs the sign of the I signal of the pilot component. Extract it and output it to the multiplier 709.

The multiplier 709 multiplies the sign of the I signal by the Q signal of the pilot component and outputs the multiplier 709 to the loop filter 710. The loop filter 710 filters and integrates an input phase error and outputs the NCO 711. The NCO 711 generates a complex carrier wave proportional to the output of the loop filter 710 and then generates a cosine wave ( COS) is output to the first and second mixers 701, and the sinusoidal wave SIN is output only to the second mixer 703. Repeating this process generates a carrier frequency signal in the NCO 711 that is almost similar to the carrier frequency component of the input signal.

As described above, according to the second embodiment of the present invention, by adjusting the gain of the pilot in the pass band, it is possible to secure better performance by reducing the possibility of malfunction that may occur in the mixer.

In this case, the pilot gain detectors 606 and 706 may generate the gain control signal by receiving the I and Q signals of the pilot component from the first and second low pass filters, and receive only the I signal of the pilot component to obtain the gain control signal. It can also be generated.

As described above, according to the carrier recovery apparatus according to the present invention, the carrier recovery is always performed after adjusting the gain of the pilot to a constant size, thereby accurately recovering the carrier even in the presence of severe multipath paths on the transmission channel. It is effective to carry out.

In addition, the present invention improves the performance of these blocks by relieving the burden of the timing recovery unit, the channel equalizer, and the phase corrector, which are the digital processing units of the rear stage, by stabilizing the baseband signal, which is the output of the mixer, in addition to improving the performance of the carrier recovery unit. There is also an effect.

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 (8)

A carrier recovery apparatus for converting a passband signal of a digitized specific channel into a baseband signal through carrier recovery, A mixer for multiplying the passband I, Q signal by a complex carrier proportional to a phase error to transition the passband I, Q signal to a baseband I, Q signal; A pilot gain adjuster configured to adjust the gain of the baseband I and Q signals according to a gain up / down control signal so as to make a size of a pilot included in the baseband I and Q signals constant; A low pass filter for removing data components from the gain-adjusted I, Q signals and outputting only the I, Q signals of the pilot components, respectively; A pilot for detecting gains of I and Q signals of pilot components respectively output through the low pass filter, comparing the gain with a preset reference signal and outputting a gain up / down control signal according to a comparison result to the pilot gain control unit. A gain detector; A phase error detector for delaying the I signal of the pilot component respectively output through the low pass filter, extracting a sign, and multiplying the Q signal of the pilot component; And And a filter and an oscillator for filtering and integrating the phase error output from the phase error detector, generating a complex carrier proportional to the integrated phase error, and outputting the complex carrier to the mixer. The method of claim 1, wherein the pilot gain control unit A first pilot gain adjuster which adjusts a gain of the baseband I signal according to a gain up / down control signal to make a size of a pilot included in the baseband I signal constant; And a second pilot gain adjuster which adjusts a gain of the baseband Q signal according to a gain up / down control signal to make a size of a pilot included in the baseband Q signal constant. delete The method of claim 1, wherein the pilot gain detector Carrier recovery characterized in that the gain of the I signal of the pilot component output through the filter is detected and compared with the gain of a preset reference signal and outputs a gain up / down control signal according to the comparison result to the pilot gain control unit. Device. The method of claim 1, wherein the phase error detector A delay unit for delaying the I signal of the pilot component outputted through the filter for a predetermined time; A code extracting unit for extracting a sign of an I signal of a pilot component output from the delay unit; And a multiplier for multiplying the sign of the I signal by the Q signal of the pilot component and outputting the result as a phase error. A carrier recovery apparatus for converting a passband signal of a digitized specific channel into a baseband signal through carrier recovery, A first mixer for multiplying the passband I signal by a cosine wave proportional to a phase error and translating the passband I signal to a baseband I signal and outputting it for symbol recovery; A pilot gain adjuster configured to adjust gains of the passband I and Q signals according to a gain up / down control signal so as to uniformly size a pilot included in the passband I and Q signals; A second mixer for translating the passband I, Q signal to a baseband I, Q signal by multiplying the I, Q signal of the pass band whose gain is adjusted by the pilot gain control unit with a complex carrier proportional to a phase error; A low pass filter for removing data components from the baseband I, Q signals output from the second mixer and outputting only I, Q signals of pilot components; A pilot for detecting gains of I and Q signals of pilot components respectively output through the low pass filter, comparing the gain with a preset reference signal and outputting a gain up / down control signal according to a comparison result to the pilot gain control unit. A gain detector; A phase error detector for delaying the I signal of the pilot component respectively output through the low pass filter, extracting a sign, and multiplying the Q signal of the pilot component; And After filtering and integrating the phase error output from the phase error detector, a complex carrier which is proportional to the integrated phase error is generated and output to the second mixer, and the cosine wave among the complex carriers is output to the first mixer. And an oscillator. The method of claim 6, wherein the pilot gain control unit A first pilot gain adjuster which adjusts a gain of the passband I signal according to a gain up / down control signal to make a size of a pilot included in the passband I signal constant; And a second pilot gain adjuster which adjusts a gain of the passband Q signal according to a gain up / down control signal to make a size of a pilot included in the passband Q signal constant. delete