KR20040083694A - Method for tuning channel of broadcast receiver - Google Patents

Abstract

PURPOSE: A broadcasting receiver and a channel tuning method therefor are provided to set tuning priority in channel environment in which input signals with inter-different signaling types are mixed, discriminate a modulation type, and efficiently tune a channel on the basis of the discriminated result. CONSTITUTION: A power detecting unit(13) detects a receiving signal in channel environment in which an NTSC(National Television Systems Committee) signal, a VSB(Vestigial SideBand) signal and a QAM(Quadrature Amplitude Modulation) signal are mixed. If the detected signal is the NTSC signal, the power detecting unit outputs the first switching signal. The first and second BPFs(Band Pass Filters)(18,19) filter the receiving signal according to inter-different pass bands. A VSB discriminator(14) selectively outputs the second and third switching signals for switching the VSB signal and the QAM signal according to the output signals of the first and second BPFs. An output signal switching unit(20) selectively switched by the first to third switching signals outputs one of the NTSC signal, the VSB signal and the QAM signal. An NTSC demodulating unit(15), a VSB demodulating unit(16) and a QAM demodulating unit(17) demodulate the signal outputted from the output signal switching unit, respectively.

Description

Broadcast receiver and its channel tuning method {Method for tuning channel of broadcast receiver}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast receiver, and in particular, to set a tuning priority and determine a modulation scheme in a channel environment in which input signals of different signal types are mixed, and to enable efficient channel tuning based on the broadcasting receiver and its channel tuning. It is about a method.

There are several types of Set Top Boxes (STBs) in the market now.

Most of the prior art STBs accept only one type of input signal, and on new TVs or STBs, the input signal can be a variety of inputs such as NTSC (National Television Systems committe), VSB (vestigial sideband), and Quadrature Amplitude Modulation (QAM). When a modulated signal comes in, there is a problem of defining channel tuning.

Here, NTSC (National Television Systems committe) converts the R, G, and B signals into one luminance signal (Y) and two chrominance signals (I, Q), and then converts the two color difference signals into 3.58 MHz in the video band. A subcarrier having a frequency is modulated, and a complex signal obtained by adding the modulated color difference signal and the luminance signal is modulated and transmitted to a carrier having a higher frequency.

QAM is a modulation method that uses a combination of both amplitude and phase of a modulated carrier, and is one of multi-level modulation methods commonly used as high-speed modulators for digital transmission using analog telephone lines. .

And VSB (vestigial sideband) is a sideband transmission method, when amplitude or voice signal or other signal waves are amplitude modulated, the spectrum of the original signal wave is preserved as the sidebands of the upper and lower sides with the carrier frequency as the center. The scheme is double sideband (DSB) transmission.

The transmission of only one of the upper side bands or the lower side band is SSB transmission, and the removal of most of one side band and transmission of the remaining side band and the other side band is the remaining side band (VSB). Transmission method.

Such a broadcast receiver of the prior art needs user definition regarding channel tuning in a channel environment in which broadcast signals of various modulation methods are mixed.

However, the conventional broadcast receiver described above has the following problems.

There is a need for additional customization and complex procedures for tuning in a reception environment with mixed signals of different modulation schemes.

The present invention is to solve the problems of the conventional broadcast receiver as described above, and to set the tuning priority in a channel environment in which the input signals of different signaling methods are mixed, and to determine the modulation scheme based on the efficient channel tuning It is an object of the present invention to provide a broadcast receiver and a channel tuning method thereof.

1 is a block diagram of a broadcast receiver according to the present invention

2 is a flowchart for a channel tuning method of a broadcast receiver according to the present invention.

Explanation of symbols for main parts of the drawings

11. Tuner 12. SAW filter / amplifier

13. Signal detector 14. VSB discriminator

15.NTSC demodulator 16.VSB demodulator

17. QAM Demodulator 18. First Band Pass Filter

19. Second band pass filter 20. Output signal switching unit

The broadcast receiver according to the present invention for achieving the above object is a signal detector for detecting a received signal in a mixed channel environment of NTSC, VSB, QAM signal and outputs a first switching signal when the detected signal is an NTSC signal ; First and second band pass filters for filtering the received signal with different pass bands; Second and third switching signals for switching VSB and QAM signals, respectively, according to output signals of the first and second band pass filters. VSB discriminator for selectively outputting a; Output signal switching unit for selectively switching by the first, second, and third switching signals to output any one signal; Demodulation of each signal output by the output signal switching unit Characterized in that it comprises a demodulation unit.

In the channel tuning method of the broadcast receiver according to the present invention, if there is a signal received in a mixed channel environment of a mixed NTSC, VSB, and QAM signal, performing NTSC tuning; terminating the tuning process when the NTSC tuning is performed. Determining whether a VSB pilot signal is detected if NTSC tuning is not performed; performing VSB tuning if a VSB pilot signal is detected; and performing QAM tuning if a VSB pilot signal is not detected.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of the embodiments.

A preferred embodiment of the broadcast receiver and its channel tuning method according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a broadcast receiver according to the present invention, and FIG. 2 is a flowchart for a channel tuning method of the broadcast receiver according to the present invention.

The present invention enables channel tuning that can be used in all kinds of TVs and STBs in a channel environment in which various types of modulation schemes such as NTSC, VSB, and QAM are mixed.

In the present invention, in order to efficiently tune an input signal in a channel situation in which various modulation schemes (NTSC, VSB, and QAM) are mixed, a tuning priority is set for each channel, and the modulation scheme is determined.

To this end, the broadcast receiver of the present invention includes a signal detector capable of determining the presence or absence of an RF input signal, and has a band pass filter unit and a discriminator for discriminating VSB and QAM signals.

It also has a means for switching the output signal of the tuner in accordance with the signal detector output and the VSB / QAM discrimination signal output.

As shown in FIG. 1, the tuner 11 converts an input RF signal into an IF signal, a surface acoustic wave (SAW) filter / amplifier 12 for filtering and amplifying a signal converted into an IF signal. A signal detector 13 for detecting a power of the filtered and amplified signal to determine the presence or absence of a signal, and determining the presence or absence of a signal and outputting a first switching signal for switching the NTSC signal by determining that the signal is an NTSC signal; The first and second band pass filters 18 and 19 and the first and second band pass filters 18 and 19 which filter the signals output to the amplifier 12 as inputs have different pass bands. The VSB discriminator 14 which determines whether the VSB signal or the QAM signal is output according to the output signal and outputs the second and third switching signals for switching the VSB signal or the QAM signal, and the SAW by the 1,2,3 switching signals. Selectively switching the output signal of the filter / amplifier 12 to output NTSC demodulator 15, VSB demodulator 16, QAM, which demodulate the NTSC signal, the VSB signal, and the QAM signal selectively output by the output signal switching unit 20 and the output signal switching unit 20, respectively. And includes a demodulator 17.

The RF signal input to the broadcast receiver is converted into an IF signal through the tuner 11, and then through the SAW filter / amplifier 12, the NTSC demodulator 15, the VSB demodulator 16, and the QAM demodulator 17. It is input to the output signal switching unit 20 for switching to.

In addition, the output of the SAW filter / amplifier 12 is input to the signal detector 13 and the first and second band pass filters 18 and 19 used for discriminating VSB / QAM.

First, if it is determined that there is a signal detected by the signal detector 13, NTSC detection is attempted, because the detection of NTSC signals takes much less time than the detection of digital signals.

In this case, when the NTSC signal is detected, the received signal is recognized as an NTSC signal. Otherwise, the signal is switched to the VSB / QAM determination signal.

For VSB / QAM discrimination, a VSB signal or a QAM signal is determined according to the presence or absence of a 46.69 MHz pilot signal existing only in the VSB.

Signal discrimination and tuning priority in channel tuning according to the present invention are as shown in FIG.

First, in a channel environment where mixed signals of NTSC, VSB, and QAM signals are mixed (S201), it is determined whether there is a signal input to a broadcast receiver such as a TV or an STB (S202).

Here, it is checked whether the detected RF AGC (Auto Gain Controller) value is greater than or equal to the set value, and if it is less than or less, it is determined that there is no input signal and ends.

If the RF AGC (Auto Gain Controller) value is greater than or equal to the set value, it is determined whether the NTSC signal is applied (S204), and the NTSC tuning is attempted (S205). When the tuning is completed, the NTSC channel is determined. Determine that is not and follow these steps.

Two band pass filters are used to determine whether they are VSB signals (S206).

Pass the input signal through two band pass filters (46.69MHz) (44MHz) to compare the two signals.

The VSB pilot signal (46.69MHz) is compared with the 44MHz IF signal, and if there is a 46.69MHz pilot signal only in the VSB signal, it is judged as a VSB signal and tuned (S208).

If there is no 46.69MHz pilot signal, it is determined as a QAM signal and tuned (S207).

The channel tuning method of the broadcast receiver according to the present invention can efficiently input signals in a channel situation in which various modulation schemes (NTSC, VSB, QAM) are mixed, and various cable channel environments depending on a single modulation scheme are used. It is to respond appropriately to the change in the mixed situation.

Such a broadcast receiver and its channel tuning method according to the present invention has the following effects.

First, separate user definition is not required for tuning in a reception environment in which signals of various modulation methods are mixed, thereby simplifying the procedure and enabling efficient tuning.

Second, it is advantageous in terms of the time required for tuning by configuring the tuning priority of the modulation scheme and the modulation scheme discriminator.

Third, the cable channel environment depending on the single modulation method can effectively cope with the change in the channel situation of the various modulation methods (NTSC, VSB, QAM).

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 (4)

A signal detector for detecting a received signal in a channel environment in which NTSC, VSB, and QAM signals are mixed and outputting a first switching signal when the detected signal is an NTSC signal; First and second band pass filters for filtering the received signals with different pass bands; A VSB discriminator for selectively outputting second and third switching signals for switching the VSB signal and the QAM signal according to the output signals of the first and second band pass filters; An output signal switching unit configured to selectively switch by the first, second, and third switching signals to output any one signal; And demodulators for demodulating each signal output by the output signal switching unit. The broadcast receiver of claim 1, wherein the first band pass filter filters 46.69 MHz VSB pilot signals and the second band pass filter filters 44 MHz IF signals. Performing NTSC tuning if there is a signal received in a mixed channel environment in which the mixed NTSC, VSB, and QAM signals are present; Terminating the tuning process if NTSC tuning is performed; Determining whether a VSB pilot signal is detected if NTSC tuning is not performed; And performing a VSB tuning when the VSB pilot signal is detected, and performing a QAM tuning when the VSB pilot signal is not detected. According to claim 3, To determine whether there is a signal input to the broadcast receiver, If the detected RF AGC (Auto Gain Controller) value is greater than or equal to the set value, and if it is less than or equal to the set value, it is determined that there is no input signal, and the tuning process is terminated. Channel tuning method of a broadcast receiver, characterized in that.