Temperature-compensated microwave integrated circuit delay line

Abstract

A temperature-compensated microwave integrated circuit device such as a delay line in which the phase delay imparted to signals coupled through the delay line is substantially constant over a wide range of temperatures. A dielectric substrate is provided, with strip conductors on one surface defining a desired device configuration such as a multi-pole Butterworth filter configuration. The substrate is enclosed within a support frame with the lower side of the substrate positioned upon the bottom surface of the enclosure forming a ground plane. A conductive plate is attached to the top cover of the enclosure through a layer of compensating material. As the temperature changes, the layer of compensating material expands or contracts, thereby varying the height of the conductive plate above the substrate, which changes the electromagnetic field pattern of signals propagating along the delay line and, consequently, the propagation velocity. The thickness and coefficient of expansion of the compensating layer are chosen to maintain the delay time through the device at a substantially constant value.