Monolithic MM-wave phase shifter using optically activated superconducting switches

DETAILED DESCRIPTION It is an object of the present invention to provide an improved phase shifter that has low overall insertion loss and symmetric insertion loss between the reference path and the delay path.
Another object of the present invention is to provide an improved phase shifter that eliminates interactions between the radio frequency signal and the biasing networks of conventional phase shifters.
Still another object of the present invention is to provide an improved phase shifter having greatly reduced signal distribution complexity, reduced control logic problems and reduced system weight.
In order to achieve the foregoing and other objects, in accordance with the purposes of the present invention as described herein, a phase shifter having an input line with a bifurcation junction and an output line with a rejoining junction, comprises: a reference path and a delay path, each extending from the bifrication junction to the rejoining junction; illumination means for providing light; and switching means operatively connected to the reference path and delay paths for switching between the reference path and the delay path in response to the illumination means.
In the preferred embodiment of the present invention, the switching means includes four switches that are made from a superconductive material.
These switches are each terminated in a virtual short circuit.
Two of the switches are connected to the reference path, and the other two switches are connected to the delay path.
Two of the switches are located about one quarter of a wavelength from the bifurcation junction, and the other two switches are located about one quarter of a wavelength from the rejoining junction.
Each of the switches is normally held near its transition temperature, i.
e.
, the temperature at which the switch enters a superconductive state from a resistive state, so that each switch is normally in a superconductive state.
The switches on either the reference path or the delay path are selectively illuminated by the illumination means, and thereby enter a resistive state