| 摘要 |
An improved threshold performance for an FM demodulator is obtained by employing the combined features of a phase locked loop demodulator and a N-path (digital) filter. The bandwidth of the filter is adjusted to approximately two times the highest baseband frequency and its center frequency is determined by the switching frequency employed in the filter which is derived from the output signal of the phase locked loop's voltage control oscillator (VCO). The VCO output signal is determined by the instantaneous IF input frequency resulting in an IF filter having a minimum bandwidth that tracks the input IF frequency.
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