Low-cost phaselocked local oscillator for millimeter wave transceivers

Abstract

An LMDS system including a base station, subscriber units and subscriber modems. Transmission frequencies between the base station and the subscriber units are specified by the Federal Frequency Commission. Signal frequencies between the subscriber units and the subscriber modems are specified by industry standards. The subscriber units couple and frequency translate modulated signals between the base stations and the subscriber modems. The frequency translation requires an intermediate transmit oscillator and a local oscillator. The intermediate transmit oscillator, however, can also be used to frequency translate a local oscillator signal within each subscriber unit down to a lower frequency which allows a low cost phase locked loop chip to be used to phase lock the local oscillator in each subscriber unit to a reference source. A pilot tone can be coupled onto modulated signals transmitted from the base station to the subscriber units. The pilot tone can be summed into the local oscillator phase locked loop within each subscriber unit to reduce the effects of signal transmission on the phase noise of the modulated signals. Furthermore, dual pilot tones can be coupled onto the modulated signal transmitted from the base station to the subscriber units. The dual pilot tones can be used to generate a reference signal within each subscriber unit.