US 5,134,707 AGranted

Satellite receiver

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsSeiji Sakashita, Hiroaki Ozeki, Ippei Kanno

Life of this patent

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Abstract

Radio waves used in broadcasting and communications making use of broadcasting satellite and communication satellite are FM signals, and the frequency shift and exclusive bandwidth vary depending on the modulation signal. The satellite broadcasting receiver is designed to control the frequency shift so that the amplitude of the demodulation signal is constant, thereby making the bandwidth of the intermediate frequency filter, so as to be capable of receiving using just one filter. At this time, the frequency shift can be controlled continuously, from large to small one, in a predetermined exclusive bandwidth. When further expanding the frequency shift, since the exclusive bandwidth is extended, the noise electric power is increased and the receiving sensitivity is lowered as compared with the exclusive machine. Accordingly, when expanding the frequency shift, the noise bandwidth is narrowed in the PLL demodulator, thereby enhancing the receiving sensitivity.

Claims15

Dependent claims

A satellite broadcasting receiver for converting an FM signal into a fixed intermediate frequency by a mixing circuit also having an oscillation circuit connected thereto, demodulating the fixed intermediate frequency in a demodulation circuit after passing it through one filter, and delivering a signal from a demodulation signal processing circuit operatively connected to an output of the demodulation circuit, comprising:

an output level setting means for setting a predetermined amplitude of the demodulation signal;
a comparing means for comparing the amplitude of the demodulation signal with the predetermined amplitude;
a modulation driving means for supplying the demodulation signal to the oscillation circuit while continuously changing the amplitude and polarity of the demodulation signal in response to an output of the comparing means;
and
an AGC voltage generating means for generating an AGC voltage for controlling the input level to the demodulator according to the polarity of the demodulation signal supplied to the oscillation circuit.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/600,988Filed 23 Oct 1990
Priority: JP 1-28055126 Oct 1989
Granted: 28 Jul 1992
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H03D 3/244
The oscillator being part of a phase locked loop: combined with means for obtaining automatic gain control
H03D 3/242
The oscillator being part of a phase locked loop: combined with means for controlling the frequency of a further oscillator, e.g. for negative…
H04B 1/1638
Circuits: special circuits to enhance selectivity of receivers not otherwise provided for
H03D
Demodulation or transference of modulation from one carrier to another