Self-test device and method having an amplifier converted into an oscillator
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United States of America Patent
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-
Sep 5, 1989
Grant Date -
N/A
app pub date -
Sep 28, 1987
filing date -
Sep 28, 1987
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
An FM receiver is self tested by connecting a positive feedback network in circuit with a wideband, front end r.f. amplifier of the receiver, so that the amplifier is converted into an oscillator. R.f. and i.f. characteristics of the receiver are determined by comparing the amplitude of an i.f. signal with a predetermined reference value while the amplifier is converted to an oscillator. Noise characteristics of the receiver are determined by comparing the amplitude of an audio frequency signal of the receiver with a predetermined value while the amplifier is converted to an oscillator and the amplifier derives an unmodulated r.f. output. Baseband characteristics of the receiver are determined by varying a reactance in the positive feedback path to impose FM on r.f. oscillations derived by the amplifier and by comparing the amplitude of the output of the audio frequency amplifier with a predetermined value. By varying the value of the reactance in the feedback loop, the oscillating frequency is swept to determine the center operating frequency and i.f. bandwidth of the r.f., amplifier.
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