A novel wide band 180-degree phase shift transition on multilayer substrates

This paper describes a low loss, compact and wide band microstrip to stripline transition with 180 degree phase shift on multilayer substrates. The simulated and measured characteristics of this transition are demonstrated here to validate the proposed concept. A phase deviation of less than 10-degrees has been achieved over a broad bandwidth of 1-25 GHz. Based on this transition, an improved compact rat race hybrid is designed and fabricated. The measured and simulated results show that the achievable bandwidth is more than twice that of conventional rat race coupler.