Patent ID: 7084717

Claim:
A quadrature hybrid circuit in which, under the condition that first, second, third and fourth I/O ports are all matched, a high-frequency signal fed via said first I/O port is divided into two according to a predetermined degree of coupling and said divided signals are provided to said second and third I/O ports in phases displaced 90° apart, said quadrature hybrid circuit comprising: circuit element means by which boundary condition on a plane of symmetry, with which side of the first and second I/O ports and side of the fourth and third I/O ports of the quadrature hybrid circuit are symmetrical to each other, is controlled in response to an external control signal so that said plane of symmetry become equivalent to a magnetic wall or electric wall; a first two-port circuit connected between said first and second I/O ports; a second two-port circuit connected between said fourth and third I/O ports; a third two-port circuit connected between said first and fourth I/O ports; and a fourth two-port circuit connected between said second and third I/O ports wherein said circuit element means includes first and second circuit elements for controlling electromagnetic connections or coupling between said first and fourth I/O ports at an intermediate point of said third two-port circuit and between said second and third I/O ports at an intermediate point of said fourth two-port circuit, wherein said first and second circuit elements are first and second single-pole single-throw switches that divide said third and fourth two-port circuits into two at said intermediate point of symmetry, respectively, and are connected in series between said divided circuits of said third and fourth two-port circuits, respectively, and wherein third single-pole single-throw switches are each inserted between one end of said first and second single-pole single-throw switches and the ground.