# US 4,393,274 A · AM Stereo receiver

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- Number: US 4,393,274 A
- Document ID: US4393274A
- Status: Granted
- Kind: A
- Application number: 06/293,839
- Filed: 1981-08-18
- Granted: 1983-07-12
- Earliest claimed: 1980-08-20
- Assignees: Trio Kabushiki Kaisha
- Inventors: Yukihiko Miyamoto
- Web page: https://patentgrep.com/patent/US4393274A

## CPC

- H04H 20/49: for AM stereophonic broadcast systems
- H04H: BROADCAST COMMUNICATION (multiplex communication H04J; pictorial communication aspects of broadcast systems H04N)

## Abstract

An AM stereo receiver for receiving AM stereo broadcasting of an AM-PM or AM-FM system. Between an IF AM signal amplifier and an limiter is interposed a 5 or more frequency multiplier so that the frequency of a spurious signal radiated from the limiter may lie outside of the frequency range handled by the RF tuner.

## Claims

### Claim 1

An AM stereo receiver comprising:
an RF AM tuner for selecting and converting an RF AM stereo signal of an AM-PM or AM-FM system into an IF AM stereo signal;
an IF AM signal amplifier for amplifying the IF AM stereo signal from the RF AM tuner;
a frequency multiplier for frequency multiplying the IF AM stereo signal from the IF AM signal amplifier to obtain a frequency-multiplied IF AM stereo signal having a frequency higher than the maximum frequency of a signal handled by the RF AM tuner;
A limiter for amplitude limiting the frequency-multiplied IF AM stereo signal from the frequency multiplier to obtain a frequency-multiplied IF PM or FM difference signal;
a PM or FM demodulator for phase or frequency modulating the frequency-multiplied IF PM or FM difference signal from the limiter to obtain a difference signal;
an AM demodulator for amplitude demodulating the IF AM stereo signal from the IF AM signal amplifier to obtain a sum signal; and
a matrix circuit for deriving a right signal and a left signal from the difference signal from the PM or FM demodulator and the sum signal from the AM demodulator.

### Claim 2 (depends on 1)

An AM stereo receiver according to claim 1 wherein the frequency multiplier frequency multiplies the IF AM stereo signal up to a frequency five times or more its frequency.