A unilateral three-level maser employing a ruby-loaded comb-type structure

BROADBAND VERY-LOW-NOISE microwave amplification has been obtained in a propagating microwave structure by using the emissive property of a three-level solid state maser material. Previous maser amplifiers have employed standing-wave cavity-type microwave structures for coupling to the emissive material.3 Such cavity-type maser amplifiers are limited in bandwidth and gain by the microwave cavity circuit. The bandwidth is limited by regenerative effects in the cavity and the gain is limited by the stringent requirements placed upon the input match and the circulator.