Two-port dipolar switch

The letter describes a simple 2-port reciprocal ferrite switch that relies on the rotation of the dipolar mode in a ferrite post or disc for its operation. The switch uses the fact that the electric field for this mode has a figure-of-eight pattern at the edge of the post or disc. In the unmagnetised state, this field pattern couples the inputn ad output ports of the transmission line. In the magnetised state, the two ports are decoupled, provided that the field is rotated through 90°, thereby placing a null of the figure-of-eight pattern at the input port. An experimental switch was constructed in stripline at 2 GHz, with an insertion loss of 1 dB and an attenuation of 28 dB.