A Power-Combined 240 GHz Frequency-Multiplier Source for Cloud Radar Applications

We present the design and testing of a >400 mW solid-state G-band transmitter developed for cloud radar applications. The source relies on GaAs on-chip power-combined Schottky diode frequency-triplers operating over a bandwidth that includes the 238–240 GHz span allocated for radar. High continuous-wave output power is achieved with additional four-way waveguide power combining, for a total of eight Schottky diode frequency-tripler circuits. This device achieves a conversion efficiency of ∼15% near 240 GHz, and was measured to have an 8% fractional bandwidth spanning 235–255 GHz. The source has been integrated into the Jet Propulsion Laboratory’s CloudCube radar instrument for profiling clouds and drizzle to reveal aspects of their microphysics and dynamics.