Miniaturized hybrid ring circuits using T-type folded substrate integrated waveguide (TFSIW)

T-type folded substrate integrated waveguide (TFSIW) scheme is an effective SIW miniaturization technique for developing high-density integrated circuits. In this paper, the propagation constant and characteristic impedance of TFSIW structures are analyzed on the basis of their equivalent circuits. To demonstrate the circuit applications, the design procedure of a proposed TFSIW hybrid ring is presented and discussed with reference to the calculated parameters. Simulation results of the designed coupler ring circuit are compared with measurement results.