Satellite receiver
First Claim
1. 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.
1 Assignment
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Accused Products
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.
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Citations
15 Claims
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1. 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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification