JPS62117887U - - Google Patents

Description

[Brief explanation of the drawing]

Fig. 1 is a schematic circuit block diagram of an intermediate frequency amplification/detection circuit in a television receiver according to an embodiment of the present invention, Fig. 2 is a diagram showing the selectivity characteristics of each filter in Fig. 1, and Fig. 3 is a diagram showing the selectivity characteristics of each filter in Fig. 1. A schematic circuit block diagram of a conventional example, FIG. 4 is a diagram showing the selectivity characteristics of the surface acoustic wave filter shown in FIG. 3, and FIGS. FIG. 2 is a composite wave vector diagram for explaining. 13...First surface acoustic wave filter, 14...Video intermediate frequency amplification circuit, 15...Video detection circuit, 16...Correction filter, 17...APC detection circuit, 18...VC
O circuit, 19... second surface acoustic wave filter, 20...
Audio intermediate frequency amplification circuit, 21... audio detection circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] In an intermediate frequency amplification/detection circuit in a television receiver that simultaneously amplifies and detects two intermediate frequency signals, video and audio, provided from a tuner, for audio intermediate frequency and video intermediate frequency. a first surface acoustic wave filter having selectivity characteristics; a first video intermediate frequency amplification circuit for amplifying the output of the first surface acoustic wave filter; a correction filter having selectivity characteristics so as to extract sidebands symmetrically; and a VCO that outputs the correction filter output.
an APC detection circuit that performs a phase comparison with a circuit output and outputs a detection output corresponding to a phase difference between the two;
a VCO circuit that outputs an oscillation frequency output corresponding to the detection output from the detection circuit as a switching signal; a video detection circuit that synchronously detects the output of the first video intermediate frequency amplification circuit with the switching signal; a second surface acoustic wave filter having a selectivity characteristic that extracts upper and lower sidebands symmetrically; an audio intermediate frequency amplification circuit that amplifies the output of the second surface acoustic wave filter; and an audio intermediate frequency amplification circuit that amplifies the output of the audio intermediate frequency amplification circuit. An intermediate frequency amplification/detection circuit for a television receiver, comprising an audio detection circuit that performs synchronous detection using the switching signal.