发明名称 |
Tuning meter for use with a pulse count FM demodulation circuit |
摘要 |
A tuning meter circuit for use with a pulse count FM demodulator of an FM receiver. The circuitry comprises a limiter circuit for amplitude limiting a frequency modulated input signal to produce a train of pulses the width of which varies in accordance with the frequency modulation of the input signal; a pulse shaping circuit for generating a trigger pulse for each of the pulses of the pulse train; a monostable multivibrator responsive to each trigger pulse for generating a train of pulses of substantially constant width, the number of which per unit time interval varies in accordance with the frequency modulation of the input signal; a low pass filter responsive to the last mentioned pulse train to produce a low frequency signal and thereby demodulate the frequency modulated signal; a difference amplifier also responsive to the last-mentioned pulse train, the difference amplifier having a threshold level at which it changes state; a tuning meter responsive to the direct current component of the output of the difference amplifier; the duty cycle of the monostable multivibrator and the threshold level of the difference amplifier being so related that the tuning indicator indicates the FM receiver is tuned correctly when a signal of exact intermediate frequency is applied to the limiter circuit; and where the monostable multivibrator includes means for varying the duty cycle thereof to compensate for undesired variations in the FM demodulator.
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申请公布号 |
US4180777(A) |
申请公布日期 |
1979.12.25 |
申请号 |
US19770859538 |
申请日期 |
1977.12.12 |
申请人 |
TRIO K K |
发明人 |
MIYAMOTO, YUKIHIKO;YAMADA, TSUNEO |
分类号 |
H03D3/00;G01R23/06;H03J3/14;(IPC1-7):H04B1/16 |
主分类号 |
H03D3/00 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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