Pneumatically controlled non-magnetic, high-power, and low insertion loss RF switch

Abstract

While positive-intrinsic-negative (PIN) diodes are commonly used in radio frequency (RF) circuits, their use often degrades the signal-to-noise ratio (SNR) due to high insertion loss and interference from additional biasing circuit components, which is critical for SNR-prioritized applications. This work presents the design of a novel pneumatically controlled switch, called AeroSwitch, which serves as an RF switch alternative to PIN diodes by significantly reducing lossy elements and additional biasing circuitry, with a focus on the applicability of AeroSwitch for magnetic resonance imaging (MRI) RF switch implantation. AeroSwitch was assessed against the PIN diode using bench testing, revealing a slightly reduced average insertion loss of 0.1 dB and an enhancement in average isolation by 15 dB. The switches are incorporated into a capacitor switch array within an L-matching network. This matching network connects to a loop RF coil, serving as a high-impedance load. The quality (Q)-factors were evaluated compared to a PIN diode capacitor switch array matching network configured identically. Overall, the AeroSwitch demonstrated an average 62% improved Q-factor compared to the PIN diode. These findings indicate that AeroSwitch offers significant advantages over the PIN diode due to its lower loss and higher isolation, potentially improving SNR. Additionally, the temperature of the AeroSwitch, while operating at 100 watts, remained consistently below 30°C, suggesting its potential as a self-temperature-regulated high-power switch. Since the AeroSwitch is non-magnetic, has high-power capability, low insertion loss, requires no electric biasing, and uses no conductive wires, this switching technique is significantly beneficial for MRI applications and medical related other RF applications.