| 摘要 |
A bridge circuit demodulator for frequency-modulated signals includes a parallel resonant circuit tuned to the carrier frequency of the FM signals. The resonant circuit includes the secondary winding of a transformer which is strongly coupled to the secondary winding. The signal to be demodulated is applied to the primary winding. Further, the signal to be demodulated is also applied to an LC phase shift circuit which shifts the signal applied to it through 90 DEG . The phase shift circuit has an output terminal connected to a center tap of the secondary winding and an input connected to receive the signal to be demodulated. The parallel resonant circuit and the phase shift circuit constitute the diagonals of the bridge circuit constituting the demodulator. The FM signal is applied to the phase shift circuit and to the parallel resonant circuit through separate outputs of a difference amplifier. The phase shift and parallel resonant circuits are thus isolated from one another so that changes in the phase or tuning of one do not affect the phase or tuning of the other.
|
