Abstract: A system which provides frequency conversion and continuously variable bandwidth control uses fixed filters to which opposite edges of the passband of the signal are applied in inverted frequency relationship. A channel contains the filters and three mixers to which injection signals derived from a single variable frequency oscillator and a fixed oscillator are applied to vary the bandwidth of the system without affecting the center frequency of the signal after processing in the system. The system may be designed to obtain either a variable bandpass or rejection band filtering characteristic.

Abstract: An adjacent channel rejector for use in communication systems such as TACAN includes a high gain amplifier adapted to be driven into saturation in response to signals in the channel, a wide band filter/demodulator connected to the high gain amplifier and a narrow band filter/demodulator connected to the amplifier. The rejector further includes an amplitude comparator coupled to these filters/demodulators for determining when a desired signal is in the channel thereby providing adjacent channel rejection.