Abstract: A one frequency repeater includes a receiver for receiving a reception signal through a receiving antenna, a variable frequency characteristic filter for generating a signal for cancelling an interference signal caused by leakage of a transmission signal into a receiving antenna, an adder for adding the interference signal and the reception signal, a demodulator for demodulating an output signal from the adder, a data converter for converting an output signal from the modulator, a modulator for modulating a carrier according to an output from the data converter, and a transmitter for transmitting from a transmitting antenna an output signal modulated by the modulator. The variable frequency characteristic filter receives the signal modulated by the modulator, is controlled in response to a control signal including the output from the data converter, and supplies the interference cancellation signal to the adder.

Abstract: A digital microwave radio repeater using the same carrier frequency for the transmitter and the receiver carriers for improving the frequency utilization efficiency. The transmitter-to-receiver interference signal is cancelled by producing an estimated-interference signal of the interference signal from the digital baseband signal by the use of a transversal filter and by subtracting the estimated-interference signal from the received signal. The estimated-interference signal is also produced by frequency shifting a digital modulated signal in the transmitter. The transmitter carrier frequency is locked to the receiver carrier frequency by the use of a phase-locking technique, so that the interference signal is reduced.

Abstract: Transmission lines for digital signals may include a large number--for example, several hundred--of intermediate generators. In this case, telemetering units are provided at the end points and at intermediate points, by means of which the digital telemetry signals are generated and sent over the transmission lines together with the digital information signals. In the event of interference, a problem arises, due to the fact that the telemetry signal that is needed to identify the interference is only available after a comparatively long time. Therefore, according to the invention, a method is recommended for the initial synchronization, at bit rate, of the pulse generators which generate the bit pulse in the telemetering units. The pulse generation is accomplished with a phase-control loop which generates a signal pulse with a comparatively high frequency.