High stability buffered phase comparator

Abstract

A low noise RF signal phase comparator comprised of two high stability driver-buffer amplifiers (16 and 18) driving a double balanced mixer (14) which operate to generate a beat frequency between the two RF input signals coupled to the amplifiers from the RF sources. The beat frequency output from the mixer is applied to a low noise zero crossing detector (20) which generates a square wave output whose positive and negative going edges provide a measure of the phase difference between the two RF inputs. Temperature stability is provided by mounting the amplifiers (16 and 18) and mixer (14) on a common circuit board (29) with the active circuit elements (62, 68, 70, 82, 88, 90, 110) thereof being located on one side of a circuit board (29) while the passive circuit elements (112) are located on the opposite side. A common heat sink (28) consisting of a relatively thick metal plate of relatively large mass and having a plurality of recesses or bores (31, 33, 35, 37, 39, 41) formed therein is located adjacent the circuit board (29) such that the active circuit elements (62, 68, 70, 82, 88, 90, 110) are embedded into the bores which has the effect of slowing down the effect of ambient temperature changes and reduces the temperature gradients between the active circuit elements, and thus improving the cancellation of temperature effects inherent in such devices. Additionally, the two amplifiers (16 and 18) include individual voltage regulators (70 and 90) which effectively increases RF isolation by reducing cross-talk through the power supply connected thereto.