Abstract: A digital rotating complex phasor generator (60) provides a constant magnitude continuous phase signal at either a positive or a negative frequency for translating the frequencies of a modulated signal from a near-zero intermediate frequency (IF) to baseband. The rotating complex phasor generator allows a digital receiver front-end to down-convert the received signal to an IF of substantially zero Hertz prior to analog to digital conversion, even in the presence of large Doppler frequency shifts and tuning uncertainties which may result in a residual IF carrier which has either a positive or a negative frequency.

Abstract: A digital radio-relay system has a transmitting terminal station, at least one repeater station a receiving terminal station, a non-regenerative repeater station which does not regenerate a digital signal in order to simplify and reduce cost of the system, while keeping excellent signal quality in transmission. Each repeater station has a plurality of sub-units relating to respective sub-system signals each having a plurality of carriers so that the frequency spectrum of each sub-system signal is allocated on a frequency axis based upon a frequency division multiplex system.