JPH03177174A - Intermediate frequency processing unit - Google Patents

Abstract

PURPOSE:To allow an intermediate frequency processing IC compatible with plural systems to corresponding to the digital voice multiplex system by adding a voice IF signal input terminal and a switch switching a signal to the IC. CONSTITUTION:In the case of using the unit in the multi-mode of PAL/SECAM system, a switch 15 is thrown to the position 2, a filter equivalent to a SAW filter 2 passing only through a voice IF signal is connected to a QIF input terminal 13 and a VCO(Voltage Controlled Oscillator) 8 at the QIF side is locked to the voice subcarrier fs2. As a result, a voice signal is outputted from an output terminal 18 in the SECAM mode and an FM voice intercarrier is outputted from an SIF signal output 17 in the PAL mode similar to the NICAM mode. However, the FM signal different from the NICAM mode is inputted to a PLL(Phase Locked Loop) detection circuit comprising of an IF amplifier 4 at the QIF side, a voice detector 6-2, a voice amplifier 9-2 and an AGC (Automatic Gain Controller) 5 to activate the AGC. Thus, the intermediate processing IC also corresponds to the digital voice multiplex system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a television intermediate frequency processing device compatible with a digital audio multiplexing system.

[Conventional technology]

Figure 3 shows NI CAM (Near
In5 tantaneous compound Au
dio Multiplex) system intermediate frequency (hereinafter referred to as I
(referred to as F).

In the figure, fs is a digital voice subcarrier, fs,
is the analog audio subcarrier, fp is the video carrier, and the digital audio subcarrier fs is QPS K (Quad
rate Phase 5hift Keying
) and the analog audio subcarrier fsz is a conventional FM signal.

FIG. 2 is a block diagram of a conventional IF processing circuit compatible with the N I CAM system.

B-1 and 8-2 are the same PLL (Phase L
(ockedLoop) method VIF (Video intermediate frequency) I
It is C.

1.2.3 is a 5AW (Surf) with the band characteristics shown in the figure.
ace Acoustic Wave) filter, 11
12 is the video signal input manually, 12 is the audio IF (SIF) signal input,
16 of VIPIC (B-1) is video signal output, VIFI
16 of C (B-2) is a QPSK signal output, and 17 is an FM audio signal output. Also, 4 is an IF amplifier, and 5 is an AGC
16-1 is a video detector (ν1deo Detect
r), 7 is APC (＾automatic Power
Control) 8 is V CO (Voltage Co
9 is a video amplifier, and 10 is a SIF detector.

Next, the operation will be explained.

VIPIC (B-1) has a SAW (Surface Acoustic Wa) with the band characteristics shown in the figure.
ve) IF multiplied signal video signal human power 11 through filter 1
The video signal is input to the VIPI, and the video signal is detected.
CCB-2) video signal input 11 includes a video carrier fp
The IF multiplied signal is inputted through a SAW filter 3 having a band characteristic having two peaks of the digital audio carrier fst and the digital audio carrier fst, and the video signal is detected. Sonotame, VIPIC (B-
2) (7) A QPSK signal is obtained as an intercarrier from the video signal output 16. Also VIPIC (B-2
) is a SAW filter 2 having a peak at the analog audio carrier fs.
An IP signal is input from the SIF detector 10, and this signal is sent to the SIF detector 10.
is multiplied by the output of ■C○8 locked to the video carrier wave fp, and an intercarrier of an analog FM audio signal is obtained from the SIF signal output 17.

As mentioned above, the QPSK signal, which is a digital audio signal, is processed in a VIF circuit separate from the video signal, and the analog audio signal is also processed in an independent detector, so the video signal and analog audio It is possible to obtain a QPSK signal, which is a digital audio signal, without receiving interference from the signal.

[Problems to be Solved by the Invention] Since the conventional digital audio multiplexing intermediate frequency processing device is configured as described above, two VIPICs are required, and one of the VIPICs is not used. There were blocks, which was wasteful both in terms of cost and power consumption.

This invention was made to solve the above-mentioned problems, and its purpose is to eliminate the waste of using two of the same IC, and to obtain a digital audio multiplexing intermediate frequency processing device that is inexpensive and consumes little power. shall be.

[Means to solve the problem]

The digital audio multiplexing intermediate frequency processing device according to the present invention includes an intermediate frequency processing IC that supports a plurality of broadcasting systems;
An input terminal for an audio IF signal is further provided, and a switch for switching the signal is added inside the IC.

[Effect]

In this invention, since an audio IF signal input terminal and a switch for switching signals are added to the IC, an intermediate frequency processing IC compatible with multiple systems can also be made compatible with digital audio multiplexing systems.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an intermediate frequency processing device according to an embodiment of the present invention.
This is a multi-IFIC that supports the /G system. This is VIPPLL detection block Al for video IF signal processing.
and a QIF PLL detection block A2 for audio IF signal processing.

In FIG. 1, the same symbols as in FIG. 2 indicate the same parts,
6-1 and 6-2 are a video detector and an audio detector, respectively, and these have the same circuit configuration, and the audio detector 6-2 detects an audio signal when the audio IF signal is AM in SECAM-L. , PAL-B/G where the audio IF signal is FM
At the time, the peak voltage of the signal is detected and AG C (Aut
o Ga1n Contr.

l). Further, 9-1 is a video amplifier, 9-2 is an audio amplifier, 14 is an audio IF signal input terminal provided to support the NICAM system, and 15 is an NI
This is a switch for switching between two modes: CAM and SECAM/PAL. This switch 15 is set to NICAM mode in the 1st position and multi (PAL/SEC) in the 2nd position.
AM) mode, and is switched by the voltage applied to the switch terminal 14. Further, 16, 17, and 18 are output terminals for video signals, FM audio signals, and QPSK signals, respectively.

Next, the operation will be explained.

First, when used in the N I CAM mode, the switch 15 is in the l position, and the input SAW filters 1, 2 .
The operation of 3 is the same as the conventional example, and the video signal is S
The IF multiplied signal that has passed through the AW filter 1 and is input to the terminal 11 is detected by the PLL detection block Al on the VIF side.

Analog audio IF signal is sent from SAW filter 2 to terminal 12
The VC on the VTF side, which is manually inputted to the SIF detector 10 and locked to the video carrier wave rp, passes through the switch 15.
○8 output and an FM signal is output from the output terminal 17 as an intercarrier.

The digital audio signal is input from the SAW filter 3 through the terminal 13 to the PLL detection block A2 on the QIF side, and the QPSK signal is outputted as an intercarrier from the terminal 18 by the same operation as the conventional IC (B-2).

When using in PAL/SECAM multi mode,
The switch 15 is in position 2, and a filter similar to the SAW filter 2 that passes only the audio IF signal is connected to the QIF input terminal 13, and the VCOB on the QIF side is locked to this audio subcarrier fs. As a result, the audio signal is output from the output terminal 18 during SECAM, and the NI CA signal is output during PAL.
As in the case of M, the FM audio intercarrier is output from the SIF signal output 17. However, this FM signal is
Unlike the AM mode, the IF amplifier on the QIF side 4. Audio detector 6-2. Audio amplifier 9-2. The AGC works by being input to the PLL detection circuit consisting of the AGC 5, and within this control range, the amplitude is always constant regardless of the input electric field strength.

〔Effect of the invention〕

As described above, according to the present invention, in contrast to the N I CAM system, the multi-I CAM system is equipped with two independent PLL detectors.
This was achieved by adding an input terminal to the FIC and a changeover switch inside the IC, so the video signal, digital audio signal, and analog audio signal are each processed by independent detection blocks, and both the video and analog audio signals are processed. This has the effect of being able to prevent interference with digital audio, being inexpensive, and consuming less power.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an intermediate frequency processing device compatible with a digital audio multiplexing method according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional intermediate frequency processing device compatible with a digital audio multiplexing method, and FIG. 3 is a block diagram of an intermediate frequency processing device compatible with a conventional digital audio multiplexing method. FIG. 2 is an IF band characteristic diagram of FIG. 1 is a video SAW filter, 2.3 is an audio SAW filter, 4 is an IF amplifier, 5 is an AGC 16 is a video or audio detector, 7 is an APC 18 is a VCO 19-1, 9-2 is a video and audio amplifier, 10 is an SIF detector 11 is the VIF input terminal, 12 is the SIF input terminal, 3 is the QIF input terminal,
14 is NICAM switch control terminal, 15 is NICAM
Switches 16, 17, and 18 are video, FM, and QPSK output terminals, respectively. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) An intermediate frequency processing device compatible with multiple broadcasting systems, including a PLL (Phase) for processing video intermediate frequency signals.
(Locked Loop) detection circuit, a second PLL detection circuit for processing the audio intermediate frequency signal, and a switch for switching between the audio intermediate frequency signal and the second audio intermediate frequency signal input. An intermediate frequency processing device that is compatible with a digital audio multiplexing system and processes video signals, analog audio signals, and digital audio signals in independent circuits so as to prevent interference with digital audio signals. .