Abstract: A monitoring and alarm system for a radio frequency microwave communications repeater unit. A plurality of signals representative of the status of a corresponding plurality of operating conditions of the repeater unit are simultaneously generated. The signals are time multiplexed to form a combined signal. The combined signal is encoded to form a digital signal of frames of data having a frequency substantially less than the communication signal carrier frequency and preferably less than the communication modulating signal frequency, with a frame being formed of data from each of the status signals. A variable attenuator is responsive to the digital signal for varying the level of the communication signal proportionally with the value of the digital signal. The level-varied communication signal is then retransmitted.

Abstract: A split band filtering scheme to reduce adjacent band interference in a communications network, such as a cellular mobile radio system, is disclosed. A repeater, interposed between a base or cell site and a mobile/portable radio, includes a down converter for converting a system operating frequency to a lower frequency signal. The lower frequency signal represents a communications band. The signal is presented to a split band filter having a narrow passband with steep skirts. The processed signal is coupled to an up converter where it is restored to the system operating frequency. In this way, the passband of the repeater is restricted to that of the desired communications band and adjacent band interference is reduced or eliminated.

Abstract: A frequency demodulation system for wideband FM is responsive to an incoming wideband frequency modulated signal to derive therefrom a demodulated output signal. The system includes a delay line having an input to which the incoming signal is applied and having an output at which a delayed incoming signal appears. The system also includes a differential amplifier having a first input to which the incoming signal is applied and a second input coupled to the delay line to receive the delayed signal. The amplifier performs direct vector addition of the incoming signal and delayed signal to produce at the output of the amplifier an amplitude modulated and frequency modulated signal which is the direct vector sum of the incoming signal and the delayed signal as amplified. The system also includes an envelope detector coupled at its input to the output of the amplifier and responsive to the amplifier output signal to produce at the detector output the demodulated signal.