KR100956813B1 - Polarity Correction Device of Digital TV Receiver - Google Patents

Abstract

The present invention relates to a polarity correcting apparatus of a digital TV receiver that determines and corrects a polarity of data when demodulating broadcast data received by a digital TV receiver due to the nature of a carrier demodulator. By determining the convergence phase of the carrier using the DC component of the signal and correcting the carrier to always converge to 0 °, the information signal to be transmitted by the transmitter is present in the orthogonal signal component, or the carrier's convergence phase is a real signal. Always converge at 0 ° even if the signal is reversed by and orthogonal signals.

Polarity correction, polarity judgment

Description

Polarity correction device of digital TV receiver {APPARATUS FOR CORRECTING POLARITY IN DIGITAL TV RECEIVER}

1 is a block diagram of a general digital TV receiver

2 is a block diagram illustrating a polarity correcting apparatus of a digital TV receiver according to the present invention.

Explanation of symbols for main parts of the drawings

201: first DC detector 202: second DC detector

203: polarity determination unit 204: polarity correction unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital TV receiver, and more particularly, to a polarity correction apparatus of a digital TV receiver for determining and correcting a polarity of data when the received data is demodulated due to characteristics of a carrier demodulator.

Currently, the residual sideband (VSB) method, which is adopted as a digital TV (DTV) broadcasting standard in Korea and the United States, is to transmit a broadcast signal using a frequency allocated for an existing analog TV broadcast. At this time, in order to minimize the impact on the existing analog TV broadcasting, the strength of the DTV signal is transmitted in a very small size compared to the analog TV signal strength. Of course, in order to reduce the influence of noise in the DTV signal, various coding schemes and channel equalizers are used so that the specification is determined so that the reception of the DTV signal is not a problem even if the signal strength is small.

However, if the situation of the transmission channel is very poor, it cannot receive a signal. DTV transmission method has the advantage of completely eliminating the noise on the transmission channel when receiving a broadcast, so that you can see the screen without any noise.However, the receiver cannot see the screen at all unless the transmission signal is completely restored. All signals that pass through poor transmission channels should be received. In practice, however, it is impossible to construct a perfect receiver because of various constraints. However, it should be configured to receive in as many situations as possible.

1 is a block diagram of a digital TV receiver receiving an ATSC 8VSB transmission scheme currently adopted as a digital TV transmission scheme in the United States and Korea, wherein a radio frequency (RF) signal modulated by a VSB scheme is received through an antenna 101. When the tuner 102 selects only a specific channel frequency desired by the user, the tuner 102 converts the VSB signal of the RF band carried on the selected channel frequency into a first intermediate frequency (IF) band and outputs it to the analog processor 103. The analog processor 103 controls passband filtering and gain on the first IF signal output from the tuner 102 to convert the first IF signal into a second IF signal, thereby converting the A / D converter 104 into a second IF signal. Will output The A / D converter 104 digitizes the second IF signal and outputs it to the phase separator 105.

 The phase separator 105 separates the digital signal into passband signals of real and imaginary components whose phases are -90 ° to each other, and outputs the digital signals to the carrier recovery unit 106. Here, for convenience of explanation, the real component signal output from the phase separator 105 is called an I signal, and the imaginary component signal is called a Q signal.

The carrier recovery unit 106 converts the I, Q passband digital signal output from the phase separator 105 into an I, Q baseband digital signal and outputs the polarity correction unit 107.

That is, the output signal of the carrier recovery unit 106 may converge in various phases according to the algorithm used. In this case, the polarity correction unit 107 corrects the polarity of the signal output from the carrier recovery unit 106 so that the convergence phase is always 0 ° in order to enable normal operation in the digital block at the rear end. The output of the polarity compensator 107 is output to the synchronizer 108 and to the digital processor 109 for channel equalization, phase tracking, error correction, and the like.

Meanwhile, in FIG. 1, the output of the carrier recovery unit 106 is input to the polarity correction unit 107, and the convergence phase of the carrier is changed according to the algorithm of the carrier recovery unit 106 used in the digital TV receiver. For example, when the frequency & phase locked loop (FPLL), which is a carrier recovery algorithm proposed in the ATSC standard of the US digital TV signal, is used, the convergence phase of the carrier may converge at 0 ° or 180 °. In addition, when other algorithms are used, the phases may converge at 90 ° or 270 ° as well as at 0 ° or 180 °.                         

However, the carrier recovery unit algorithms commonly used by the company and the third party use the carrier recovery algorithm FPLL, which is proposed in the ATSC standard, which is a standard for digital TV signals in the United States. This is because the FPLL method has a simple structure and excellent performance. Accordingly, the role of the polarity correcting unit 107 is designed to enable polarity correction only when the angle is 0 ° or 180 °. That is, when the convergence phase of the carrier is 0 ° or 180 °, since the sign (+/-) of the signal simply changes, the polarity correction unit 107 corrects this.

However, when the carrier recovery unit uses an algorithm other than FPLL, the phase of the carrier may converge at 90 ° or 270 ° as well as 0 ° or 180 °, and the polarity correction unit 107 may have a different phase of the carrier. When convergence at 90 ° or 270 ° there was a problem that can not correct the polarity.

That is, when the convergence phase of the carrier is 0 ° or 180 °, not only the sign but also the real signal and its quadrature signal are inverted. The polarity correction unit 107 uses only the real signal. Since the polarity was corrected, the correct polarity was not corrected, and the information could not be corrected even when the information signal to be transmitted by the transmitter was present in the orthogonal signal component. In this case, there was a problem that the digital TV receiver does not operate normally.

The present invention has been made to solve the above problems, and an object of the present invention is to determine the change in polarity caused by the characteristics of the carrier recovery unit in the digital TV receiver, the convergence phase of the carrier is 0 °, 90 °, 180 °, It is to provide a polarity correction device for a digital TV receiver that improves the performance of the entire receiver by correcting the convergence to 0 ° at all times even at 270 °.

Another object of the present invention is to provide a polarity correction apparatus of a digital TV receiver for determining and correcting a convergence phase of a carrier using not only a real signal but also a quadrature signal thereof.

In order to achieve the above object, a polarity correction apparatus of a digital TV receiver according to the present invention includes a first direct current detector for detecting a direct current component of a baseband real signal output from a carrier recovery unit, and a direct current of the baseband orthogonal signal. A polarity determining unit for determining a carrier convergence phase of the carrier recovery unit by using a second DC detector for detecting a component, magnitudes and codes of two DC components output from the first and second DC detectors; And a polarity correction unit for correcting the polarity of the baseband real and quadrature signals output from the carrier recovery unit and outputting the data for data recovery according to the determination result.

The polarity determining unit determines that the convergence phase of the carrier is 0 ° when the absolute value of the DC component of the real signal is greater than the absolute value of the DC component of the orthogonal signal, and the sign of the real signal DC component is '+'. The polarity correction unit may output a baseband real signal and an orthogonal signal output from the carrier recovery unit as they are.

The polarity determining unit determines that the convergence phase of the carrier is 180 ° when the absolute value of the DC component of the real signal is greater than the absolute value of the DC component of the orthogonal signal, and the sign of the real signal DC component is '-'. The polarity correcting unit inverts and outputs the baseband real signal and the orthogonal signal respectively output from the carrier recovery unit.

The polarity determination unit determines that the convergence phase of the carrier is 90 ° when the absolute value of the DC component of the real signal is smaller than the absolute value of the DC component of the orthogonal signal and the sign of the orthogonal signal DC component is '+'. The polarity correcting unit converts the baseband real signal output from the carrier recovery unit into an orthogonal signal and outputs the converted orthogonal signal, and converts the orthogonal signal into an inverted real signal.

The polarity determining unit determines that the convergence phase of the carrier is 270 ° when the absolute value of the DC component of the real signal is smaller than the absolute value of the DC component of the orthogonal signal, and the sign of the orthogonal signal DC component is '-'. The polarity correction unit converts the baseband real signal output from the carrier recovery unit into an inverted orthogonal signal, and outputs the converted orthogonal signal into a real signal.

The present invention is characterized in that the carrier recovery unit can always converge to 0 ° even when the carrier convergence phase is 0 °, 90 °, 180 °, and 270 ° even when using various algorithms other than FPLL. .

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, the configuration and operation of the embodiments of the present invention with reference to the accompanying drawings, the configuration and operation of the invention shown in the drawings and described by it will be described as at least one embodiment, which By the technical spirit of the present invention described above and its core configuration and operation is not limited.

2 is a block diagram illustrating a polarity correcting apparatus according to the present invention, wherein a first DC detector 201 and a carrier wave detect a DC component of a baseband real signal i (t) output from the carrier recovery unit 106. A second DC detector 202 for detecting a DC component of the baseband quadrature signal q (t) output from the recovery unit 106, the magnitudes of the two DC components output from the first and second DC detectors 202, and The polarity determination unit 203 for determining the convergence phase of the carrier wave output from the carrier recovery unit 106 by using the polarity, and the output from the carrier recovery unit 106 according to the determination result of the polarity determination unit 203 And a polarity correction unit 204 for correcting the convergence phase of the baseband real number and quadrature signals i (t) and q (t) to be always 0 degrees.

In the present invention, the convergence phase of the carrier and the polarity of the carrier are used in the same sense, and they will be used interchangeably.

According to the present invention configured as described above, when two signals of a passband, that is, a real signal and a quadrature signal pass through the carrier recovery unit 106, the baseband real signal i (t) Is converted to the orthogonal signal q (t). In this case, the two signals i (t) and q (t) of the baseband are completely transformed into baseband signals after the carrier recovery is completed, but components according to the convergence phase remain due to the algorithm of the carrier recovery unit 106. In order to determine the convergence phase, the baseband real signal i (t) is input to the first DC detector 201 and the orthogonal signal q (t) is input to the second DC detector 202.

The first direct current detector 201 detects the direct current (dc) component of the real signal i (t) of the baseband and outputs it to the polarity determination unit 204, and the second direct current detector 202 outputs the baseband orthogonal signal. A direct current (dc) component of q (t) is detected and output to the polarity determination unit 204.

The polarity determination unit 204 determines the polarity of the signal output from the carrier recovery unit 106 by using the detected two DC components, in which case the four cases are determined. That is, the polarity determined by the polarity determination unit 203 is a convergence phase of carriers corresponding to 0 °, 90 °, 180 °, and 270 °. The polarity determination operation of the polarity determination unit 203 is shown in Table 1 below.

   Criteria 1       Judgment standard 2  Judgment polarity   DC signal size       DC signal polarity | Real signal DC component | > | Signal DC component | Real signal polarity of DC component = '+'      0 ° Real signal polarity of DC component = '-'    180 ° | Real signal DC component | <| Orthogonal Signal DC Component | Polarity of orthogonal signal DC component = '+'     90 ° Polarity of orthogonal signal DC component = '-'    270 °

That is, in Table 1, there are two judgment criteria, judgment criteria 1 for determining polarity based on the magnitude of the DC component of the real signal and the DC component of the orthogonal signal, and judgment for determining the polarity based on the sign of the DC component having a large magnitude. There is a standard two. For example, | real signal DC component | > | Orthogonal signal direct current component | and the polarity of the real signal direct current component is '+', the signal output from the carrier recovery unit 106 is determined to have a polarity of 0 °, | real signal direct current component | > | Orthogonal signal direct current component | and the polarity of the real signal direct current component is '-', the signal output from the carrier recovery unit 106 is determined to have a polarity of 180 °. Also, | real signal DC component | <| Orthogonal signal direct current component | and the polarity of the orthogonal signal direct current component is '+', the signal output from the carrier recovery unit 106 is determined to have a polarity of 90 °, | real signal direct current component | If the polarity of the orthogonal signal DC component is &quot;-&quot;, the signal output from the carrier recovery unit 106 has a polarity of 270 °.

The polarity signal determined by the polarity determination unit 203 is transmitted to a polarity corrector 204, and the carrier convergence phases of the baseband signals i (t) and q (t), which are outputs of the carrier recovery unit 106, are output. The polarity of the output signal of the carrier recovery unit 106 is corrected so as to always be 0 ° and output.

Table 2 below shows the operation of the polarity correction unit 204.

Judgment Polarity (Convergence Phase)          Input signal           Output signal Real signal i (t) Quadrature signal q (t) Real signal i '(t) Quadrature signal q '(t)      0 °     i (t)     q (t)     i (t)     q (t)     90 °     i (t)     q (t)     q (t)    -i (t)    180 °     i (t)     q (t)    -i (t)    -q (t)    270 °     i (t)     q (t)    -q (t)     i (t)

That is, the polarity correction unit 204 always modifies the polarity of two signals i (t) and q (t) input according to the polarity (or the convergence phase of the carrier) determined by the polarity determination unit 203. Two converged signals i '(t), q' (t)} are generated with the convergence phase of 0 °.

Looking at the operation of the polarity determination unit 203 and the polarity correction unit 204 as follows. First, two baseband signals i (t) and q (t) output from the carrier recovery unit 106 are represented by Equation 1 below.

는 반송파 복구부(106)의 알고리즘에 따른 수렴 위상이다. 또한, 상기된 수학식 1에 있는 파일롯 신호 성분은 반송파 복구가 완료되어 직류 신호 성분에 존재하게 된다.Here, I (t) is an information signal to be transmitted by the transmitter, Q (t) is an orthogonal component of the I (t) signal, and p is a pilot signal component used by the carrier recovery unit 106. Ingredient. Also,

Is the convergence phase according to the algorithm of the carrier recovery unit 106. In addition, the pilot signal component in the above Equation 1 is completed in the carrier recovery is present in the DC signal component.

Therefore, the outputs of the first and second DC detectors 201 and 202 are as shown in Equation 2 below.

When the polarity determined by the polarity determination unit 203 is substituted into the equation 1 using the signal output as shown in Equation 2,

When the convergence phase of the carrier is 0 °, it is expressed by Equation 3 below.                     

When the convergence phase of the carrier is 90 °, the following equation (4) is used.

When the convergence phase of the carrier is 180 °, it is expressed by Equation 5 below.

When the convergence phase of the carrier is 270 °, the following equation (6) is obtained.

Therefore, the polarity correction unit 204 always outputs a signal as shown in Equation 3 above.

As described above, the polarity correction apparatus of the digital TV receiver according to the present invention determines the convergence phase of the carrier by using the DC component of the real signal and the orthogonal signal in which carrier recovery has been performed, and corrects the carrier to always converge to 0 °. Thus, accurate polarity correction is performed even when the information signal to be transmitted by the transmitter is present in the orthogonal signal component or when the convergence phase of the carrier is inverted with a real signal and its orthogonal signal. By operating, the performance of the receiver is improved. In addition, even if the algorithm used in the carrier recovery unit uses an algorithm other than FPLL, the receiver works well regardless of the convergence phase of the carrier signal of the carrier recovery unit.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the 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 (6)

A polarity correction apparatus of a digital TV receiver having a carrier recovery unit for converting a passband real signal and an orthogonal signal into a baseband real signal and an orthogonal signal, A first DC detector which detects a DC component of the baseband real signal output from the carrier recovery unit and outputs the DC component to a polarity determination unit; A second DC detector for detecting a DC component of the baseband orthogonal signal output from the carrier recovery unit and outputting the DC component to a polarity determination unit; A polarity determination unit for determining a carrier convergence phase of the carrier recovery unit by using magnitudes and codes of a DC component of the baseband real signal and a DC component of a baseband orthogonal signal, and And a polarity correction unit for correcting the polarity of the baseband real and quadrature signals output from the carrier recovery unit according to the determination result of the polarity determination unit and outputting the data for data recovery. The method of claim 1, The polarity determining unit determines that the convergence phase of the carrier is 0 ° when the absolute value of the DC component of the real signal is greater than the absolute value of the DC component of the orthogonal signal, and the sign of the real signal DC component is '+'. And the polarity correcting unit outputs a baseband real signal and an orthogonal signal output from the carrier recovery unit as it is. The method of claim 1, The polarity determination unit determines that the convergence phase of the carrier is 180 ° when the absolute value of the DC component of the real signal is greater than the absolute value of the DC component of the orthogonal signal, and the sign of the real signal DC component is '-'. And the polarity correction unit inverts the baseband real signal and the orthogonal signal output from the carrier recovery unit, respectively, and outputs the inverted signals. The method of claim 1, The polarity determining unit determines that the convergence phase of the carrier is 90 ° when the absolute value of the DC component of the real signal is smaller than the absolute value of the DC component of the orthogonal signal, and the sign of the orthogonal signal DC component is '+'. And the polarity correcting unit converts the baseband real signal output from the carrier recovery unit into an orthogonal signal, and converts the baseband orthogonal signal into an inverted real signal and outputs the converted real signal. The method of claim 1, The polarity determining unit determines that the convergence phase of the carrier is 270 ° when the absolute value of the DC component of the real signal is smaller than the absolute value of the DC component of the orthogonal signal, and the sign of the orthogonal signal DC component is '-'. And the polarity correcting unit converts the baseband real signal output from the carrier recovery unit into an inverted orthogonal signal, and converts the baseband orthogonal signal into a real signal and outputs the real signal. delete

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