초록 ▼

An AM Stereo receiver is described which includes an AGC having an output which indicates whether the received signal has significantly decreased in level and having a clamping circuit for controlling the voltage at the input of a VCO. The clamping circuit is further defined as having a window detec

An AM Stereo receiver is described which includes an AGC having an output which indicates whether the received signal has significantly decreased in level and having a clamping circuit for controlling the voltage at the input of a VCO. The clamping circuit is further defined as having a window detector for sensing a change in the voltage at the input of the VCO according to a predetermined threshold; a selectable controller, responsive to the window detector, for adjusting the voltage at the input of the VCO; and a window reduction circuit, responsive to the output signal of the AGC, for altering the predetermined threshold to provide the controller with a more sensitive indication of a drift in the voltage at the input of the VCO. The receiver additionally includes a conventional locked loop driver for steering the VCO according to the phase of the received input signal. When the AGC output signal indicates that the signal quality of the received signal has significantly decreased in level, or when the window detector indicates that the system is tuned outside of an established narrow “tuned”window, the locked loop driver is disabled to prevent the locked loop driver from introducing a beat note into the VCO.

대표청구항 ▼

In a receiver which includes sensor means for detecting a decrease in the level of a received signal, a clamping circuit for controlling the voltage coupled to the input of a VCO, comprising: window detection means for sensing a change responsive to the frequency of said received signal in the volta

In a receiver which includes sensor means for detecting a decrease in the level of a received signal, a clamping circuit for controlling the voltage coupled to the input of a VCO, comprising: window detection means for sensing a change responsive to the frequency of said received signal in the voltage at the input of the VCO according to a predetermined threshold; window reduction means, responsive to the sensor means, for altering the predetermined threshold; and clamping means, responsive to said window detection means, for selectively controlling the voltage coupled to the input of the VCO, further including phase driver means, responsive to the sensor means, for controlling the voltage at the input of the VCO when the phase locked loop is locked to the received signal.