Broadband and compact impedance transformers for microwave circuits

The introduction of unconventional matching techniques, such as a transmission line transformer (TLT) using straight or coiled sections of coupled transmission lines, to realize multi-octave impedance transformation at RF and low microwave frequencies, was investigated. The TLT transformer design employed multilayer fabrication technology, such as a printed circuit board, low temperature cofired ceramic (LTCC), high temperature cofired ceramic (HTCC), and monolithic silicon or galium arsenide ICs. The four microstrip 50 to 12.5 Ω transformer configurations which were used in simulation includes single section, uncoupled lines TLT, side coupled lines TLT and asymmetric broadside coupled lines TLT. The effect of polymide thickness on TLT bandwidth was studied by varying its value and keeping other parameters. The TLT transformers were tested as a function of input power using high power sources, which includes the assembling of several chips on gold plated Elkonite crystals.