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.

Abstract: A frequency synthesizing apparatus of the closed-loop design employing a first frequency mixing means to provide a continuous constant increment frequency coverage over a given output signal frequency range. The first frequency mixing means is responsive to the output signal and a first reference signal to provide a first difference signal both when the output signal frequency is higher than and lower than the first reference signal frequency. A frequency comparison means is responsive to the first difference signal and to an input signal, the input signal being continuously variable over a given input frequency range, to provide a first error signal for controlling the output frequency and stabilizing the closed loop. The first reference signal is comprising of a plurality of predetermined, selectable frequencies provided by a phase-locked loop employing a second frequency mixing means.