Compact dual-mode four-port network with quadrature coupling and direct-thru transmission in each of the individual bands

Summary form only given, as follows. By utilizing quasi-lumped LC tanks, a new synthesized microstrip line is proposed. Differing from its conventional counterparts, this design shows open-circuit input impedance at its attenuation pole; it isolates the synthesized line from other signal paths. A compact dual-mode fourport network, having quadrature coupling and direct-thru transmission in each of the two bands, is developed. The design method, circuit layouts, and experimental results are discussed carefully in this paper.