GaN HEMT-Based Resonators Using Parasitic Effects and Its Application to A Ka-band Coupled-Resonator SPDT Switch

A series of switchable resonators are proposed by incorporating the parasitic effects of two gallium nitride (GaN) high electron mobility transistor (HEMT) devices in this letter, based on which a broadband single-pole double-throw (SPDT) switch is presented with a bandpass response. As for on-chip switches, the ideal transistor is desired to act as a capacitor in its off-state but a resistor in its on-state. In conventional switch designs, the inductive effects of transistors are typically suppressed due to their detrimental impact on impedance matching and isolation. In contrast to this conventional approach, this study proposes a resonator-based design strategy that intentionally exploits and amplifies these inductive characteristics to construct two distinct GaN HEMT-integrated resonators. The first resonator employs the enhanced on-state inductance of a switching transistor combined with an MIM capacitor to form a series resonant network, enabling broadband impedance matching. The second resonator utilizes the large off-state capacitance of a power transistor and a short-circuited transmission line to establish a parallel resonant network. Leveraging the unique properties of these resonators, a broadband switch topology is accordingly proposed and experimentally validated. For demonstration, a SPDT switch is designed and fabricated in a 100 nm GaN-on-Si process. The proposed switch operates from 16 to 33 GHz based on experimental measurements. Two transmission poles are observed in the passband. This result experimentally validates the GaN HEMT-based resonator design.