Abstract
One of the most important microstrip discontinuities used in hybrid and monolithic MIC circuit design is the T-junction. T-junctions are heavily used in a variety of microstrip circuits including impedance matching networks, transistor amplifiers, mixers, filters, power dividers, antenna feeds, couplers, switches and diplexers. GaAs monolithic microwave integrated circuit (MMIC) design is primarily accomplished through the use of microwave computer aided design (CAD) tools. CAD has revolutionized hybrid and monolithic microwave integrated circuit design as with many other engineering disciplines. However, CAD based microwave circuit design success is inherently dependent on the accuracy of the models used to simulate individual circuit elements. Currently, GaAs T-junction discontinuity effects and circuit models are not fully understood nor accurate. This thesis thoroughly characterizes 100 um thick GaAs based microstrip T-junction discontinuity effects. This thesis also provides a new CAD based equivalent circuit model for 100 tun thick GaAs symmetric T-junctions. The new model was developed based on the results of an accurate full- wave analysis. Compared to the currently accepted Hammerstad model the new model has a 35.7% reduction in S₂₁ phase error and a 41.6% reduction in S₃₁ phase error at 50 GHz for GGs T-junctions with line widths ranging from 10 um to 300 um. T-junction measurement theory and RLC equivalent circuit modeling techniques are discussed. Comprehensive full-wave electromagnetic simulator setup and simulation settings specific to GaAs T-junction simulations are presented. Finally, T-junction compensation techniques and their applications to GaAs circuit design are discussed.
Guill, Dennis Jarrett (1999). A study of microstrip T-juction discontinuity effects and modeling on GAAS substrates. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1999 -THESIS -G82.