Steady-State and Transient Thermal Analysis of High-Power Planar Schottky Diodes

Abstract

Recent progress in power amplifier technology has made it possible to construct W-band sources which are capable of producing powers in the 1-Watt range. These sources are required in order to build multiplier based local oscillator chains in the frequency range of 2-3 THz. However, it becomes imperative that the multipliers, in particular the initial stage multipliers, be able to withstand the large input power without degrading efficiency or burning out.In this work, we present a systematic study of the steady-state as well as transient thermal behavior of doubler and tripler chips in the 200 GHz range that have been developed at JPL. The Ansys Structural Mechanic software tool has been used to simulate thermal performance of the planar Schottky diodes using a finite-element approach. Experimental verification of the simulation tool is achieved by performing infra-red (IR) thermal imaging on a multiplier chip mounted in a half open waveguide block. The simulation tool is used to explore the various parameters (chip topology, novel materials, cryogenic temperatures etc) and it is concluded that a careful thermal design of the first stage multiplier is necessary in order to produce robust LO chains in the 2-3 THz range. The thermal effects on the multiplier performances will also be discussed.