Development of Low-Cost Microwave and RF Modules for Compact, Fine-Resolution FMCW Radars

The Center for Remote Sensing and Integrated Systems (CReSIS) has enabled the development of several radars for measuring ice and snow depth. One of these systems is the Ultra-Wideband (UWB) Snow Radar, which operates in microwave range and can provide measurements with cm-scale vertical resolution. To date, renditions of this system demand medium to high size, weight and power (SWaP) characteristics. To facilitate a more flexible and mobile measurement setup with these systems, it became necessary to reduce the SWaP of the radar electronics. This thesis focuses on the design of several compact RF and microwave modules enabling integration of a full UWB radar system weighing < 5 lbs and consuming < 30 W of DC power. This system is suitable for operation over either 12-18 GHz or 2-8 GHz in platforms with low SWaP requirements, such as unmanned aerial systems (UAS). The modules developed as a part of this work include a VCO-based chirp generation module, downconverter modules, and a set of modules for a receiver front end, each implemented on a low-cost laminate substrate. The chirp generator uses a Phase Locked Loop (PLL) based on an architecture previously developed at CReSIS and offers a small form factor with a frequency non-linearity of 0.0013% across the operating bandwidth (12-18 GHz) using sub-millisecond pulse durations. The down-conversion modules were created to allow for system operation in the S/C frequency band (2-8 GHz) as well as the default Ku band (12-18 GHz). Additionally, an RF receiver front end was designed, which includes a microwave receiver module for de-chirping and an IF module for signal conditioning before digitization. The compactness of the receiver modules enabled the demonstration of multi-channel data acquisition without multiplexing from two different aircraft. A radar test-bed largely based on this compact system was demonstrated in the laboratory and used as part of a dual-frequency instrument for a surface-based experiment in Antarctica. The laboratory performance of the miniaturized radar is comparable to the legacy 2-8 GHz snow radar and 12-18 GHz Ku-band radar systems. The 2-8 GHz system is currently being integrated into a class-I UAS.