Packaging of a state-of-the-art v-band active cold load and RF switch

Abstract

Microwave radiometers must be regularly calibrated to maintain high measurement accuracy. Conventional calibration systems often use cold sky and onboard reference views. These different views are typically selected using a rotating mirror. An Active Cold Load (ACL) can provide an electronically controlled cold reference directly in the receiver chain, while a Radio Frequency (RF) switch routes the receiver between the measurement and calibration reference paths. This thesis presents the packaging and integration of two V-band Silicon-Germanium (SiGe) Monolithic Microwave Integrated Circuits (MMICs), an ACL and an RF switch. The thesis includes the design of a WR-15 waveguide-to-planar transition, bondwire interconnects between MMIC and transition, split-block design and biasing boards. Specifically an E-plane probe on alumina was developed and designed for the SiGe MMIC interface using a Coplanar Waveguide with Ground (CPWG) section and a multi-stage impedance transformer optimized in ANSYS High Frequency Structure Simulator (HFSS). The transition achieved a simulated return loss of S11 < −26.9 dB and S21 > −0.3 dB across the targeted frequency band 50 − 60 GHz. In addition, a backto- back structure showed S11 < −17.8 dB and S21 > −0.6 dB. Furthermore, a sensitivity analysis was performed, demonstrating that the design remained below S11 < −20 dB for all investigated variations. The design was evaluated through fullwave electromagnetic (EM) simulations, while the planned scattering parameter and noise temperature measurement procedures are described for future characterization. The simulation results suggest that the proposed packaging design is suitable to realize compact V-band ACL and RF switch modules for radiometer calibration.