Microwave and millimeter wave phase shifter

摘要

A variable phase shifter based on the slow-wave effect for operation in the millimeter wave region, comprising a GaAs substrate for mechanical support; an n+ doped semiconductor layer disposed on the GaAs substrate for operation as a first ground plane; an n doped semiconductor layer disposed on the n+ semiconductor layer with a thickness to permit only one mode at millimeter wave frequencies to propagate, while suppressing higher order millimeter wave modes; and a Schottky metal microstrip with first and second ends disposed on top of the n doped semiconductor layer. Means are provided in the form of ohmic contacts for electrically connecting the n+ semiconductor layer to ground electrical potential. These ohmic contacts are disposed on top of the n doped layer, but are provided with a very large surface area contact to the n doped layer in order to significantly reduce the resistance between the ohmic contact and to the n+ semiconductor layer. Means are included for providing an electrical bias voltage between the Schottky metal microstrip and the n+ doped layer. The propagating phase velocity of millimeter waves propagating along the Schottky metal microstrip can be varied in accordance with the bias voltage to obtain a desired phase shift between the first and second ends of the metal microstrip. In one embodiment, a metallic second ground plane is disposed on the other face of the semiconductor substrate. In a preferred embodiment, the n doped semiconductor layer is approximately 2 microns or less in thickness.