In this study, we designed a $W$ -band asymmetric single-pole double-throw (SPDT) switch using a 65-nm RFCMOS process. In order to secure the power-handling capability of the switch, all transistors constituting the switch were designed to be in the on-state in the transmit (Tx) mode. In addition, the designed switch was matched in the Tx mode and achieved compact size using the property of the inductor. In the receive (Rx) mode, four $LC$ resonators were used to achieve both wide and high isolation and low insertion loss. At 70–90 GHz, the isolations in the Tx and Rx modes were measured higher than 17.5 and 22.5 dB, respectively. The insertion losses in the Tx and Rx modes were measured less than 3.71 and 3.11 dB, respectively, in the frequency range of 70–90 GHz. The measured input 1-dB compression points (IP $_{\mathrm{1dB}}$ s) at 80 GHz were $>$ 18.5 dBm and 7.5 dBm in the Tx and Rx modes, respectively. The core size of the designed SPDT switch is 0.057 mm $^{2}$ .

This article presents the design, fabrication, and experimental validation of an X-band (8–12 GHz) high-power single-pole double-throw (SPDT) RF switch based on a 150-nm gallium nitride high electron mobility transistor (GaN HEMT) process. The proposed switch architecture incorporates parallel LC resonant circuits and a traveling-wave transistor network to simultaneously achieve low insertion loss, high Tx/Rx isolation, and enhanced power handling capability in a compact footprint. To overcome the limitations of conventional quarter-wavelength-based designs, a novel power distribution technique using parallel inductors is introduced, enabling dynamic current sharing under high-power operation. The fabricated chip, including test pads, occupies an area of $2.70 \times 0.74$ mm². Measured results demonstrate a return loss greater than 13.3dB across the target frequency band, with insertion losses of less than 0.9 dB in Tx mode and 1.2 dB in Rx mode. Isolation performance exceeds 37.2dB (Tx) and 27.8 dB (Rx), while the input 1-dB compression point (IP ${}_{\mathrm {1dB}}$ ) reaches 41.7dBm in Rx mode and exceeds 45.5 dBm in Tx mode. These results confirm the effectiveness of the proposed resonant isolation and power distribution strategy, making the switch a promising candidate for compact, high-power RF systems in X-band applications.

In this study, we present the design of a single-pole double-throw (SPDT) switch for Sub-6 GHz applications, implemented using a 500-nm GaAs BiFET process. To enhance power handling capability, multi-gate transistors are selectively employed. The frequency characteristics of return loss, insertion loss, and isolation are analyzed through an equivalent circuit model. Based on this analysis, we propose a design methodology that optimizes transistor on-resistance and parasitic capacitance for the target frequency range, thereby improving power handling, insertion loss, return loss, and isolation. The fabricated switch is evaluated across an operating frequency range of 3.0-5.0 GHz. In Tx mode, the input P1dB exceeds 38.1 dBm at 4.0 GHz. The measured insertion loss and isolation in Tx mode are below 0.38 dB and above 36.6 dB, respectively. In Rx mode, insertion loss remains below 0.38 dB, while isolation exceeds 35.0 dB.

In this study, a single-pole double-throw (SPDT) switch for Sub-6 GHz application is designed. In particular, a shunt inductor is connected to the antenna port of the switch for ESD (electrostatic discharge) protection in RF (radio frequency) front end module. The shunt inductor not only serves as an ESD protection device, but also serves as a component of a parallel resonance circuit to suppress insertion loss of the switch. In addition, in order to secure the power handling capability, transistors turned off in the transmit (Tx) mode are implemented as quadruple-gate transistors. An SPDT switch is fabricated using GaAs pHEMT provided in the 500 nm GaAs BiFET process to verify the feasibility of the proposed switch structure. The operating frequency is set from 3 GHz to 5 GHz. The insertion loss and isolation measured in the Tx mode are lower than 0.35 dB and higher than 31.6 dB, respectively. The insertion loss and isolation measured in the Rx mode are lower than 0.32 dB and higher than 33.9 dB, respectively. The chip size including test pads is 0.890 × 0.875 mm².

Series-connected inductors are widely employed in RF integrated circuits to implement compact high-impedance shunt paths. However, unexpected impedance minima are often observed near the operating band, severely degrading RF performance. This article identifies the physical origin of this phenomenon and demonstrates that it arises from an eigenmode, previously unexplored in integrated spiral inductor literature, formed by the coupling between floating intermediate nodes and the substrate. Specifically, we term this resonance phenomenon “floating node resonance (FNR).” Critically, FNR frequency (f_FNR) is not a higher order standing-wave self-resonant frequency (SRF) of a single inductor, but rather a new eigenmode arising from floating node-to-substrate coupling that exists only in series-connected structures. This resonance is inherently absent in single-inductor configurations. Closed-form modal resonance laws are derived to predict the frequencies of this new resonance for both double- and triple-series configurations, and their physical validity is rigorously verified through distributed transmission-line theory and full-wave electromagnetic simulations. Based on this understanding, a systematic design methodology is developed that intentionally exploits the first self-resonance to maximize shunt impedance while placing the new resonance outside the operating band. An X-band gallium nitride (GaN) HEMT SPDT switch fabricated in a 150-nm GaN process validates the proposed framework, achieving insertion loss below 1.0 dB, isolation exceeding 35.3 dB, and IP ${}_{\text {1 dB}}$ greater than 45.5 dBm in Tx mode and 43.8 dBm in Rx mode in a compact chip area of $2.62\times 0.73$ mm².

This article presents the design of a band-selectable switch for 5G New Radio (NR) multiband (MB) transceiver applications. To achieve high isolation (ISO) and impedance matching across low-band (LB) (24–29 GHz) and high-band (HB) (37–40 GHz) operations, a reconfigurable magnetically coupled inductor structure is proposed. The mutual inductance polarity of the inductors is configured to be positive or negative depending on the operating band, enabling band-specific resonance through the combination of magnetic coupling and parasitic capacitances. The switch is implemented in a 65-nm RFCMOS process. Measurement results show that the proposed switch achieves ISO greater than 36.6 dB and insertion loss (IL) less than 2.37 dB in the LB mode, and ISO greater than 33.3 dB and IL less than 3.28 dB in the HB mode.