On-Wafer Microstrip Meander-Line Slow-Wave Structure at Ka-Band

A novel configuration for a Ka-band V-shaped microstrip meander-line slow-wave structure (SWS) is reported. The SWS is designed to work at a voltage less than 4 kV and provide a wide bandwidth. Coplanar waveguide (CPW) input-output feed lines and a shielding structure are incorporated to enable fast on-wafer cold test measurements on a CPW probe station without requiring dicing or a metal enclosure. Simulated dispersion characteristics and coupling impedance for the optimized design are presented. The simulated S
₁₁
of the entire structure is better than -15 dB over 25-36 GHz. The proposed configuration is fabricated using 4'' Si wafers and standard microfabrication processes. The measured S11 of the entire structure is better than -10 dB over 20-40 GHz. The observed high insertion loss has been explained in detail, and alternative approaches that can reduce the loss have been proposed. The PIC simulation results show that for a 3.6-kV, 50-mA sheet beam, the output power can potentially reach 14.5 W at 34 GHz with a gain of 21.6 dB. A 3-dB bandwidth of about 25% centered at 32 GHz is also indicated.