JPH02183686A - Satellite broadcast tuner - Google Patents

Abstract

PURPOSE:To offer the convenience for the viewer by detecting the reception of a satellite broadcast signal, discriminating the modulation system from the prescribed information component and displaying it if a signal unable to be demodulated is received. CONSTITUTION:A carrier detection circuit 21 supplies a broadcast detection signal to a control section 30 when a video signal band component with a prescribed level over exists. Moreover, a PCM demodulation circuit 13 supplies a control code separated from the demodulated digital data to a control code discrimination circuit 22 being a modulation system discrimination means. Then the control section 30 consists of a microprocessor, controls each section of the tuner and when the absence of a decoding means corresponding to the modulation system discriminated under the presence of a broadcast detection signal is detected, the section 30 applies a prescribed display. Thus, the reason why a picture or an audio signal are unable to be reproduced is displayed clearly to offer the convenience for the viewer.

Description

TECHNICAL FIELD The present invention relates to a satellite broadcast tuner (hereinafter simply referred to as a tuner) that receives a satellite broadcast signal and obtains a video signal and an audio signal.

Background technology An example of a conventional tuner will be explained with reference to FIG.

In FIG. 3, satellite broadcast radio waves arriving at a parabolic antenna 1 are converted into satellite broadcast signals and supplied to a converter 2. The converter 2 converts the 12 [GHz] band satellite broadcasting signal into a 1 [GHz] first intermediate frequency signal, amplifies it, and supplies it to the preamplifier circuit 3 of the tuner. The preamplifier circuit 3 amplifies the first intermediate frequency signal, attenuates the interference signal in the image frequency band using an image rejection filter, and supplies the signal to the mixing circuit 4 . The mixing circuit 4 constitutes a frequency conversion circuit together with a local oscillator circuit 5 that generates a local oscillator signal of a frequency according to a tuning command. The frequency conversion circuit converts 1,035 to 1.335 [MHz] from the preamplifier 3.
The first intermediate frequency signal of 134.26 MHz or 4
02.78 [MHz] into a second intermediate frequency signal. The oscillation frequency of the local oscillator circuit 5 is such that the second intermediate frequency signal is 13
In the case of 4.26 [MHz], it is 1.18 to 1.45 [G
Hz], 402.78 [MHz], 1.45
~1.72 [GHz]

The intermediate frequency amplification circuit 6 amplifies the second intermediate frequency signal, selects the signal of the reception channel using a 27 [GHz] bandpass filter, and blocks unnecessary signals other than those of the reception channel. Then, the AGC circuit supplies a signal at a constant level to the amplitude limiting circuit 7 at the next stage. The amplitude limiting circuit 7 keeps the amplitude of the FM signal constant, removes unnecessary amplitude noise, and amplifies the signal to a signal level suitable for the operation of the FM demodulation circuit 8 in the next stage. The FM demodulation circuit 8 is configured using, for example, a PLL system, and outputs a voltage proportional to the frequency deviation of the FM signal. This output is a baseband signal, which includes a video signal with a bandwidth of 4.5 [MHz] and a video signal with a bandwidth of 5.73 [MHz].
MHz] and an audio carrier having a center frequency are frequency division multiplexed. The baseband signal demodulated in this way is transmitted to the video signal processing circuit 9 and the audio signal processing circuit 1.
0.

The video signal processing circuit 9 separates the video signal from the baseband signal using a low-pass filter (not shown), and restores the pre-emphasized video signal to its original characteristics using a de-emphasis circuit. Furthermore, the energy spread signal is removed from this video signal by an energy spread signal removal circuit and is supplied to a receiver (not shown).

The baseband signal is also supplied to the audio signal processing circuit 10, and is passed through a 5.73 [MHz] bandpass filter 11.
The audio carriers are separated by

This audio carrier is a PSK signal and is supplied to the four-phase DPSK demodulation circuit 12. The four-phase DPSK demodulation circuit 12 has a known configuration including a synchronous detector, a differential converter, a parallel-serial converter, etc., and decodes a digital data signal from a PSK signal. The above-mentioned digital data signal is a PCM signal along with a pit clock reproduced from this digital data signal.
The signal is supplied to the demodulation circuit 13.

The PCM demodulation circuit 13 detects, from the digital data signal, a frame synchronization signal indicating the start of a frame, a control code for distinguishing between A/B modes, stereo/monaural, etc., and based on these signals. The decoding method is selected and data processing such as disk crumple and deinterleaving of the digital data signal is performed. The processed digital data signal is converted into an analog signal by the D/A converter 14, and output as an audio signal through a low-pass filter, de-emphasis circuit, etc. (not shown). This audio signal is supplied to the receiver or stereo device.

In this way, it becomes possible to receive satellite broadcast signals and watch television.

By the way, MUSE (Mul
tiple 5ub-Nyquist Samplin
Satellite broadcasting using the g encoding) system is planned and is currently in the experimental broadcasting stage. This system is the same as the current satellite broadcasting system up to the demodulation stage of the baseband signal, so when an experimental broadcast is made on the same channel, the tuner enters the receiving state.

However, since the digital data decoding method is different between current satellite broadcasting and MUSE satellite broadcasting, images and audio are not demodulated, so viewers may mistakenly think that the tuner is malfunctioning.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a tuner that displays a message to that effect when a signal that cannot be demodulated is being received for the convenience of the viewer.

In order to achieve the above object, a satellite broadcast tuner includes a demodulating means for receiving and demodulating a satellite broadcast signal, and a reception detecting means for detecting reception of the satellite broadcast signal and generating a broadcast detection signal; a modulation method determining means for determining the modulation method of the satellite broadcasting signal from a predetermined information component of the signal; and a decoding means corresponding to the determined modulation method in the presence of the broadcast detection signal. The present invention is characterized by comprising a control means for displaying the information.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIG. In FIG. 1, parts corresponding to those shown in FIG. 3 are given the same reference numerals, and explanations of these parts will be omitted.

In FIG. 1, a video signal demodulated by a video signal processing circuit 9 is supplied to a video output end via one input end of a video switch 20 for synthesizing character information and the like on the screen. The output signal of the character pattern generation circuit 23 is supplied to the other input terminal of the video switch 20. When the output signal is supplied, the video switch 20 preferentially relays the character pattern output signal to the output terminal and inserts a character subtitle or the like on the screen. The character pattern generation circuit 23 is composed of a memory, a character generator, etc.
Generates a series of character patterns in response to instructions from 0.

In order to detect signal reception, a carrier detection circuit 21 as a reception detection means is provided, for example, at a subsequent stage of the FM demodulation circuit 8. The carrier detection circuit 21 includes a low-pass filter, a level detector, a level comparator, etc., and supplies a broadcast detection signal to the control unit 30 when a video signal band component of a predetermined level or higher is present.

Further, the PCM demodulation circuit 13 supplies the control code separated from the demodulated digital data to the control code discrimination circuit 22, which is a modulation method discrimination means. The control code determination circuit 22 is configured by, for example, a microprocessor, and is configured to determine whether the supplied control signal corresponds to the current satellite broadcasting signal decoding system consisting of an NTSC video signal and a PCM audio subcarrier signal. If a control code is present, a control code detection signal is supplied to the control unit 30, and if a control code is not supplied or the tuner does not have decoding means corresponding to the content of the control code, no control code detection signal is generated.

The control section 30 is composed of a microprocessor and controls each section of the tuner.

The operation of the control section 30 will be explained with reference to FIG. 2. In the main control program, the microprocessor
When it is detected that a flag indicating that a satellite broadcast that cannot be demodulated should be displayed on the screen when it is received is turned on, the subroutine shown in FIG. 2 is executed.

First, it is determined whether a broadcast detection signal is being supplied (step Sl). If a broadcast detection signal is being supplied, it is determined whether a control code detection signal is being supplied (step S2). If the broadcast carrier component is detected but no control signal is detected, this corresponds to the case where a MUSE system broadcast signal is being received, so a display command is issued to the character pattern generation circuit 23 (step S3). The character pattern generation circuit 23 sends out a character pattern stored in the memory, for example, "Unable to receive during rMUSE broadcast" in response to the display command.

This character pattern is displayed on the screen of the receiver via the video switch 20. After issuing the above display command, the process returns to the main control program.

If the broadcast detection signal is not supplied (step S1), the tuner will not enter the receiving state, and the viewer will not be misled, so this subroutine ends. If a control code is detected (step S2), it means that the current satellite broadcasting signal is being received, so there is no need to perform the above display, and this subroutine ends. The microprocessor repeats execution of the above-mentioned subroutine at regular intervals to respond to changes in the reception status.

In this manner, when satellite broadcasting using the MUSE system is performed, a message indicating that the MUSE broadcast is in progress is displayed on the television screen to attract the attention of viewers.

In the embodiment, text captions are displayed on the television screen, but synthesized voices, display lamps, etc. may also be used to indicate that MUSE is being broadcast.

Further, the configuration of the modulation method determining means for detecting the MUSE signal is not limited to the embodiment. For example, the baseband signal of the MUSE signal has a bandwidth of about 8.1 [MHz], which is wider than current satellite broadcasting, so a bypass filter is used to detect the level of signal components of, for example, 7 [MHz] or higher. The presence of the MUSE signal may also be detected.

Furthermore, in the MUSE system, since the synchronization signal of the video signal is different from that in the normal NTSC system, the modulation system determining means may determine the modulation system of the satellite broadcasting signal from this synchronization signal.

Furthermore, it is also possible to detect reception of a satellite broadcasting signal using the AGC signal of the intermediate frequency amplification circuit 6.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the satellite broadcast tuner of the present invention is capable of notifying that the tuner is receiving a MUSE signal when the received satellite broadcast signal is in a decoding system that the tuner does not have, such as the MUSE system. Therefore, the reason why images and sounds are not reproduced is clearly shown for the convenience of the viewers.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a flowchart for explaining the operation of the control unit 30.
FIG. 3 is a block diagram showing a conventional example. Explanation of codes of main parts 8...FM demodulation circuit 10...Audio signal processing circuit 21...Carrier detection circuit 22...Control code detection circuit 23. ...Character pattern generation circuit 30...
・Control Department Applicant: Pioneer Corporation

Claims (4)

[Claims] (1) A satellite broadcast tuner including demodulation means for receiving and demodulating a satellite broadcast signal, the receiver detection means for detecting reception of the satellite broadcast signal and generating a broadcast detection signal, and the satellite broadcast signal. a modulation method determining means for determining the modulation method of the satellite broadcasting signal from a predetermined information component of the signal; and a predetermined display when it is detected that there is no decoding means corresponding to the determined modulation method in the presence of the broadcast detection signal. A satellite broadcasting tuner characterized by comprising a control means that performs the following. (2) The satellite broadcast tuner according to claim 1, wherein the predetermined information component is a control code of a decoded audio signal. (3) The satellite broadcast tuner according to claim 1, wherein the predetermined information component is a high frequency component of a baseband signal. (4) The satellite broadcast tuner according to claim 1, wherein the predetermined information component is a synchronization signal of a video signal.