Direct conversion FM receiver
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United States of America Patent
Stats
-
Sep 24, 1991
Grant Date -
N/A
app pub date -
Mar 14, 1989
filing date -
Mar 16, 1988
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A direct conversion receiver for demodulating an FM signal converted frequency down converts the signal to quadrature related baseband signals (I,Q). These signals are applied by way of respective d.c. blocking capacitors (16, 18) and differentiating circuits (26, 28) to a differential arctan demodulator (20). The action of the differentiating circuits (26, 28) is to remove any d.c. component in the I and Q signals and to perform a frequency shaping which enables the demodulator (20) to recover correctly the modulating information. Measures are disclosed to overcome the effects of 180 degree phase jumps which will occur when the direction of rotation of the phasor reverses and of frequency dependent amplitude scaling introduced into the differentiated signals (I', Q').
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