REFERENCE OSCILLATOR DESIGN FOR IMPROVED RECEIVER FREQUENCY STABILITY
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2001-Nov-29
Frequency drift of narrowband receivers is a major design concern. Frequency drift over temperature, of superheterodyne receivers is largely caused by two factors: local oscillator drift and i.f. filter drift. These drifts must be compensated by widening the i.f. filters, which in turn degrades receiver selectivity. With the introduction of digitally stabilized reference oscillators, local oscillators controlled by the phase locked loop method can be stabilized to 1 ppm or less quite economically, eliminating the local oscillator drift as a concern. This leaves the i.f. filter as the major source of receiver drift. This invention uses the local oscillator to counteract the filter drift, to produce a receiver with significantly greater frequency stability.