JPH07212800A - Discriminating device for broadcast system - Google Patents

Abstract

PURPOSE:To provide a broadcast system discriminating device capable of deciding whether a broadcast system in an analog or a digital. CONSTITUTION:An analog broadcast signal subjected to FM modulation via a channel selection circuit 2 is inputted to an FM demodulator 4, in which the signal is demodulated. A demodulation output of the FM demodulator 4 is converted into a video signal by using a video circuit 6. The digital broadcast signal subjected to I/Q modulation via the channel selection circuit 2 is inputted to an I/Q detector 5, where the signal is detected. A detection output from the I/Q detector 5 is demodulated into a video signal by using a digital demodulation circuit 9. The video signals outputted respectively from the video circuit 6 and the digitial demodulation circuit 9 are discriminated by a video discrimination circuit 8. The video discrimination circuit 8 selects the output of the FM demodulator or the output from the I/Q detector based on the result of discrimination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast type broadcast discriminating apparatus for discriminating analog and digital television broadcasting systems.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional analog and digital television (TV) broadcast receiver.
The signal input from the antenna 51 is distributed to a system A for receiving analog broadcasting and a system D for receiving digital broadcasting.

In the case of analog broadcasting transmitted by the FM modulation system, the signal input from the antenna 61 is selected by the tuning circuit 62. This selected signal is
The signal input to the FM demodulation circuit 63 and FM-demodulated is output 6a. The demodulated signal 6a is input to the video processing circuit 64 and output as the video signal 6b.

In the case of digital broadcasting transmitted by the multiplex PSK modulation system, the signal input from the antenna 61 is selected by the tuning circuit 65. The selected signal is input to the I / Q detection circuit 66, and the I / Q detected output signal 6c is output. The I / Q detection signal 6c is input to the digital demodulation circuit 67 and the analog video signal 6d is input.
Is output, and one is output as a video output signal.

In this way, analog and digital broadcasts can be received by separate TV receivers. However, the user did not know whether the broadcast received and tuned by each TV receiver was an analog broadcast or a digital broadcast until the actual video signal was displayed on the screen. Further, even if it was understood, it was necessary to switch to the broadcasting system corresponding to the received signal.

[0006]

SUMMARY OF THE INVENTION In the above-mentioned conventional broadcasting system discriminating apparatus for discriminating between analog and digital TV broadcasting systems, it is not possible to discriminate the TV broadcasting system until it is displayed on the screen, and it is received even after it is understood. It took time and effort to switch to a broadcasting system corresponding to the signal.

The present invention provides a broadcasting system discriminating apparatus capable of discriminating between broadcasting systems of analog broadcasting and digital broadcasting.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an F output to an FM demodulation circuit for analog broadcasting.
M demodulation discrimination circuit, or video signal discrimination circuit for video output, and I / Q detection circuit output for I / Q
It is characterized by comprising means for connecting a circuit for performing detection discrimination or a circuit for performing video signal discrimination to video output, and controlling the signal selection SW after the channel selection circuit from the result of the determination circuit.

[0009]

According to the above means, the signal inputted from the result of each judgment circuit is discriminated whether it is an analog broadcast or a digital broadcast, and the signal selection SW circuit is controlled. In the case of analog broadcast, the signal is transmitted to the FM demodulator side. However, in the case of digital broadcasting, the broadcasting system can be automatically determined in order to transmit the signal to the I / Q detection side.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of a TV broadcast receiver for explaining one embodiment of the present invention. The signal input from the antenna 1 is tuned for broadcasting by the channel selection circuit 2. The selected signal is input to the broadcasting system switch 3. The switch 3 outputs the output signal a to the FM demodulation circuit 4 in the case of analog FM broadcasting, and outputs the output signal b to the I / Q detection circuit 5 in the case of digital broadcasting.

In the case of FM-modulated analog broadcasting, the output signal a is input to the FM demodulation circuit 4, where the FM demodulated signal c is output. The demodulated signal c is the video processing circuit 6
1 is output to the output terminal 7 and the other is input to the video discriminating circuit 8.

In the case of multiplex PSK-modulated digital broadcasting, the output signal 3b is input to the I / Q detection circuit 5 and
The detected output signal e is output. The I / Q detection signal e is input to the digital demodulation circuit 9, and the analog video signal f
Is output, one is output as a video output signal, and the other is input to the video discriminating circuit 8.

In the TV receiver configured as described above, it is impossible to determine whether the input signal is analog broadcasting or digital broadcasting, but it cannot be determined when the signal is input to the antenna 1. Therefore, first, the switch 3 for signal switching
It is necessary to switch to either of them to discriminate the signal. Here, the switch 3 is switched to the analog broadcasting side when a signal is input.

In such a state, for example, in the case of analog broadcasting, the signal input from the antenna 1 is transmitted to the FM demodulator 4 by the switch 3 via the tuning circuit 2. This signal becomes the video signal output d in the video circuit 6. The video signal d is discriminated by the video signal discrimination circuit 8 as to whether it is a correct video signal. The discriminating circuit 8 can be realized by, for example, a well-known circuit for discriminating whether or not there is a synchronizing pulse of a TV video signal. If the analog broadcast can be correctly received in such a state, the video signal discrimination circuit 8 discriminates that the signal is correctly received and switches the switch 3 to the analog broadcast side as it is.

When a digital broadcast is received in the above state,
Since no video signal is output to the output signal d of the video circuit 6, the video signal discrimination circuit 8 discriminates that the signal is not correctly received and switches the switch 3 to the digital broadcasting side. The signal from the tuning circuit 2 is I / Q by the switch 3.
It is transmitted to the detection circuit 5. The signal e detected by the I / Q detection circuit 5 is demodulated by the digital demodulation circuit 9 into a video signal f, which is supplied to the video signal discrimination circuit 8 and output to the video output 10. If the digital broadcast can be correctly received in such a state, the video signal discrimination circuit 8 discriminates that the signal is correctly received, and the switch 3 is switched to the digital broadcast side as it is. When an analog broadcast is received while the switch 3 in the above-described state is on the digital broadcast side, the video signal is not output to the output signal f of the digital demodulation circuit 9, so the video signal determination circuit 8 receives the signal correctly. The switch 3 is switched to the analog broadcasting side by the determination signal g that it is not.

In this way, whether the input signal received from the antenna 1 is an analog broadcast or a digital broadcast, the switching state of the switch 3 is changed to the broadcasting system based on the discrimination signal g generated by the video signal discrimination circuit 8. You can automatically switch to the corresponding state.

FIG. 2 is a circuit configuration diagram for explaining another embodiment of the present invention. The same parts as those in FIG. The signal input from the antenna 1 is tuned for broadcasting by the channel selection circuit 2. This selected signal is
Input to the switch 3 for switching the broadcasting system. The switch 3 outputs the output signal a in the case of analog FM broadcasting.
In the case of digital broadcasting, the output signal b is output.

In the case of analog broadcasting, the output signal a is input to the FM demodulation circuit 4, and the FM demodulated signal c is output here. One of the demodulated signals c is input to the video processing circuit 6, and the other is input to the FM demodulation determination circuit 21. It is input to the video processing circuit 6 and output to the video output 7 as the video signal d.

In the case of digital broadcasting, the output signal b is I / Q.
The signal is input to the detection circuit 5, and the output signal e subjected to I / Q detection is output here. One of the output signals e is the digital demodulation circuit 9
And the other is input to the I / Q detection determination circuit 22. The signal input to the digital demodulation circuit 9 is demodulated,
It is output to the video output 10 as an analog video signal f.

Discrimination signal g of FM demodulation discrimination circuit 21 and I /
The discrimination signal h from the Q detection discrimination circuit 22 is input as a control signal for the switch 3 to switch the signal transmission path. Here, the FM demodulation circuit discrimination circuit 21 and I /
The Q detection discrimination circuit 22 can discriminate from the characteristics of the signal spectrum, for example. FIG. 3 shows an input spectrum in the FM demodulation discrimination circuit 21. FIG. 3 (a)
Shows the frequency spectrum of the analog broadcast signal after FM demodulation. In analog FM broadcasting, a dispersal signal is added to spread the spectrum, so
A spectrum signal also appears on the low frequency side. On the other hand, FIG.
(B) shows the frequency spectrum after the multiplex PSK signal of digital broadcasting is input to the FM demodulation circuit. Here, the multiplexed PSK signal is, for example, F of the demodulation method of the PLL circuit.
The output signal when phase-locked by the M demodulation circuit 4 is locked to the frequency of the transmission carrier signal, so that a frequency carrier appears on the high frequency side. Due to such characteristics of frequency components, the FM demodulation determination circuit 21 has a BPF characteristic as shown in A of FIG. That is, the frequency spectrum signal is extracted by the BPF having the characteristic of extracting the frequency component of the low frequency region not including the transmission carrier signal of the multiplex PSK signal, and if the signal level is high, it is regarded as analog broadcasting, and if the signal level is low, it is digital broadcasting. Can be determined.

Similarly, FIG. 4 shows an input spectrum in the I / Q detection discrimination circuit 22. FIG. 4A shows the frequency spectrum of the digital broadcast signal after I / Q detection. In digital broadcasting, the multiplexed PSK signal is input to the I / Q detection circuit 5, and the frequency spectrum after detection outputs the frequency of the transmission carrier signal, so that the frequency carrier appears on the high frequency side. On the other hand, when the analog broadcast is input to the I / Q detection circuit 5, the input spectrum of the I / Q detection determination circuit 22 is simply converted by the detection circuit. get together.
Due to such characteristics of frequency components, the I / Q detection determination circuit 22 has a BPF characteristic as shown by B in FIG. That is, the frequency spectrum signal is extracted by the BPF having the characteristic of extracting the high frequency component including only the transmission carrier signal of the multiplex PSK signal, and if the signal level is high, it is regarded as digital broadcasting, and if the signal level is low, it is determined as analog broadcasting. be able to.

In determining whether the input signal is analog broadcasting or digital broadcasting, it cannot be determined when the signal is input to the antenna 1. Therefore, first, it is necessary to switch the switch 3 for signal switching to either one to discriminate the signal. Here, the switch 3 is switched to the analog broadcasting side when a signal is input.

In such a state, for example, in the case of analog broadcasting, the signal input from the antenna 1 is transmitted to the FM demodulator 4 by the switch 3 via the tuning circuit 2. FM
The demodulation determination circuit 21 determines whether the FM demodulation signal is correct. The FM demodulation discriminating circuit 21 discriminates that the signal is correctly received and switches the switch 3 to the analog broadcasting side as it is.

When a digital broadcast is received in this switching state, the FM demodulation determination circuit 21 determines that the signal is not correctly received and switches the switch 3 to the digital broadcast side. The signal from the tuning circuit 2 is transmitted to the I / Q detection circuit 5 by the switch 3 circuit. With respect to the signal e detected by the I / Q detection circuit 5, the I / Q detection determination circuit 22 determines that the signal is correctly received, and the switch 3 is switched to the digital broadcasting side as it is.

When analog broadcasting is received while the switch 3 is on the digital broadcasting side, the I / Q detection discrimination circuit 22
Determines that the signal is not correctly received and automatically switches the switch 3 to the analog broadcasting side.

In this embodiment, the analog and digital broadcasting systems can be discriminated by a simple structure after the FM demodulation circuit 4 and the I / Q detection circuit 5. Since this can be determined in the portion closer to the input of the TV receiving system, it is possible to determine analog broadcast and digital broadcast at higher speed.

FIG. 5 is a circuit configuration diagram for explaining another embodiment of the present invention. The signal input from the antenna 1 is tuned by the tuning circuit 2 for broadcasting. The selected signal is input to the FM demodulation circuit 4 and the I / Q detection circuit 5. Of these signals, when the signal input to the FM demodulation circuit 4 is analog broadcasting, the FM demodulated signal c is output. One of the demodulated signals c is input to the video processing circuit 6 and the other is input to the FM demodulation determination circuit 21. It is input to the video processing circuit 6 and output as a video signal d to one input of the switch 3 '.

The I / Q detection circuit 5 outputs the I / Q-detected output signal e when the input signal is digital broadcasting. One of the output signals e is sent to the digital demodulation circuit 9,
The other is input to the I / Q detection determination circuit 22. The signal input to the digital demodulation circuit 9 is output to the other input of the switch 3'as an analog video signal f.

The output signal g of the FM demodulation discrimination circuit 21 and I /
The output signals h from the Q-detection determination circuit 30 are input to the switches 3'and the signal transmission paths are switched to output video signals.

Here, the FM demodulation circuit discrimination circuit 21 and the I / Q detection discrimination circuit 22 can discriminate between digital broadcasting and analog broadcasting according to the characteristics of the signal spectrum of the method described with reference to FIGS.

In the TV receiver configured as described above, it is impossible to determine whether the input signal is an analog broadcast or a digital broadcast, but it cannot be determined when the signal enters the antenna. Therefore, the signal input from the antenna 1 is transmitted to the FM demodulator 4 via the channel selection circuit 2, and the FM demodulation determination circuit 21 determines whether the signal is a correct FM demodulation signal. When the FM demodulation discriminating circuit 21 discriminates that the signal is correctly received, the switch 3 ′ is switched to obtain the video output from the output of the video circuit 6.

When the switch 3'receives a digital broadcast in this switching state, the FM demodulation discriminating circuit 21 discriminates that the signal is not correctly received and the switch 3'outputs the video signal from the output of the digital demodulating circuit 9. To do. Tuning circuit 2
The signal from is transmitted to the I / Q detection circuit 5. For the signal 15 detected by the I / Q detection circuit 5, the I / Q detection determination circuit 22 determines that the signal is correctly received and the switch 3 is detected.
´ is switched as it is.

When an analog broadcast is received with the switch 3'on the digital broadcast side, the I / Q detection discrimination circuit 2
Switch 2 determines that 2 is not receiving the signal correctly
Switch ´ to analog broadcasting side.

In this embodiment, since the broadcasting systems of analog and digital broadcasting are discriminated after the FM demodulation circuit 4 and the I / Q detection circuit 5, it is possible to discriminate in the portion closer to the input of the TV receiving system. It is possible to distinguish between analog broadcasting and digital broadcasting at higher speed.

[0035]

As described above, according to the broadcasting system discriminating apparatus of the present invention, it is possible to discriminate between analog broadcasting and digital broadcasting and automatically switch to a receiving state corresponding to this.

[Brief description of drawings]

FIG. 1 is a system diagram for explaining an embodiment of a broadcasting system discrimination device of the present invention.

FIG. 2 is a system diagram for explaining another embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining an input spectrum of the FM demodulation discrimination device of FIG.

4 is an explanatory diagram for explaining an input spectrum of the I / Q detection discrimination device of FIG.

FIG. 5 is a system diagram for explaining another embodiment of the present invention.

FIG. 6 is a system diagram for explaining a method for distinguishing analog broadcasting / digital broadcasting in a conventional TV receiving system.

[Explanation of symbols]

 1 ………… Antenna 2 ………… Channel selection circuit 3,3 ′… Switch 4 ………… FM demodulation circuit 5 ………… I / Q detection circuit 6 ………… Video circuit 8 ………… Video discrimination circuit 9 ………… Digital demodulation circuit 21 ………… FM demodulation discrimination circuit 22 ………… I / Q detection discrimination circuit

Claims (3)

[Claims] 1. An FM demodulator that demodulates an FM-modulated analog broadcast signal, a video circuit that uses a demodulated output of the FM demodulator as a video signal, and an I that detects an I / Q-modulated digital broadcast signal. / Q
A detector, a digital demodulation circuit for demodulating the I / Q detector into a video signal, a video discriminator capable of discriminating between the video circuit and a video signal connected to the digital demodulation circuit, and a discrimination result of the video discrimination circuit. A broadcasting system discriminating apparatus comprising: the FM demodulator and a selection means for selecting an output to the I / Q detector based on the FM demodulator. 2. An FM demodulator for demodulating an FM-modulated analog broadcast signal, and an I / Q for detecting an I / Q-modulated digital broadcast signal.
A detector and F for discriminating that the FM demodulation has been performed by the FM demodulator.
M demodulation discriminator, I / Q detection discriminator capable of discriminating whether the output of the I / Q detector is an I / Q detected output, discrimination result of the FM demodulation discrimination circuit and the I / Q detection discrimination circuit A broadcasting system discriminating apparatus comprising: the FM demodulator and a selecting means for selecting an output to the I / Q detector based on the above. 3. An FM demodulator for demodulating an FM-modulated analog broadcast signal, a video circuit for converting a demodulated output of the FM demodulator into a video signal, and an I / Q for detecting an I / Q-modulated digital broadcast signal. A Q detector, a digital demodulator circuit for demodulating the output of the I / Q detector into a video signal, a video discriminator capable of discriminating between the video circuit and a video signal connected to the digital demodulator circuit, A broadcasting system discrimination device comprising a selection means for selecting an output from the video circuit and the digital demodulation circuit based on a discrimination result.