Broadband CMOS unidirectional coupler using differential mode suppression

Abstract

AbstractThis paper describes the design of a broadband, unidirectional coupler designed using complementary metal oxide semiconductor technology. The proposed coupler achieves high isolation by using a differential mode suppressor, employing a differential splitter, followed by a common mode combiner. An intermediary network is used to match all stages to the ports. The coupler, fabricated using United Microelectronics Corporation 180 nm RF/MM technology, achieves better than 15 dB isolation from 0.2 to 1.5 GHz. For this band, it achieves a near flat coupling of 5 dB. The net coupler area is  mm2. Such broadband unidirectional couplers can be used in network analyzer testsets.