Investigation of thick film technology for microwave applications

Abstract

Recently, considerable interest has arisen in the use of thick film technology for microwave circuit applications. The thick film process can be used to fabricate microwave circuits that perform just as well as thin film counterparts in the lower-frequency region below 1 GHz, but systematic efforts to explore the upper frequency limit of thick-film technology with practical microwave circuits have been lacking. We describe such an effort which involved testing four scaled versions of one microwave circuit design over an 18-to-one frequency range. By using the same basic design and scaling the circuit physically to cover a given sub-range, variations in the circuit design were eliminated and any degradation in measured performance can be attributed to intrinsic process limitations. Results are presented for octave-bandwidth Wilkinson power dividers for the frequency ranges 1–2 GHz, 2–4 GHz, 4–8 GHz, and 9–18 GHz. We conclude that satisfactory microwave performance can be obtained routinely from thick-film circuits up to approximately 10 GHz, and with special attention designs can be extended to perhaps 12–15 GHz.