A Ka-Band Three-Stage Coupled-Resonator Single-Pole-Double-Throw Switch Using Gallium Nitride Technology

This article proposes a Ka-band single-pole-double-throw (SPDT) switch utilizing coupled-resonator circuit topology. First, the parasitic parameters of gallium nitride (GaN) high electron mobility transistors (HEMTs) are analyzed and extracted. In this way, the equivalent circuit for a third-order coupled-resonator SPDT switch is built by merging these extracted parasitic effects. One extra transmission zero (TZ) can been generated for one HEMT-based resonator, which can be further controlled for a high out-of-band suppression by selecting appropriated inductive parameter of HEMT devices. In addition, the transmission pole (TP) of the HEMT-based resonator can also be controlled. By further using the coupling matrix theory, three poles and one zero are obtained for a three-stage coupled-resonator SPDT switch. For demonstration, a 150nm GaN-on-Si process is adopted, and the coupled-resonator switch is constructed by a five-section coupled-line in conjunction with four HEMTs. The switch features a compact layout with dimensions of 0.82 mm
²
, a wide passband of three TPs, and over 20 dB off-state isolation, 1.5 dB on-state insertion loss, and over 17 on-state dB return loss.