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This thesis consists of two parts. The first part presents a
novel electromagnetic simulation technique that incorporates a
full-wave space-domain integral equation technique with a
proposed excitation model based on the equivalence principle.
The integral equation is solved numerically by Galerkin''s
procedure resulting in the generalized scattering matrix (GSM)
descriptions of the microwave circuit de-embedding. Rigorous
convergence studies and extensive validity checks confirm the
reliability and accuracy of the proposed method. The novel
technique immediately demonstrates its obvious application for
quantitative near-discontinuity characterization of higher-order
modes and multimode associated with microwave circuit
discontinuity problems. The newly proposed method is employed
further to investigate the mode conversion of a CBCPW open-end
discontinuity with unequal side plane widths. The conversion
into two additional dominant modes, the c-mode-like mode and the
?mode-like mode, and into the transmitted microstrip mode from
an incident CPW mode is studied against side plane width, degree
of asymmetry, substrate thickness, and frequency. Theoretical
results are in excellent agreement with experimental ones. The
mode conversion associated with the surface-wave- like mode at
discontinuities of CPW is also investigated. When incorporated
with the segmentation method to analyze a complex and large
microwave planar circuit, the novel technique analyzes
individually each smaller segment and then combines them to
yield overall network characterization of the composite circuit.
This can significantly reduce the requirement of computation
time and memory space. Very good agreement is obtained in a
comparative study of an arbitrary planar structure analyzed by
the full-wave method with and without segmentation,
respectively. The second part of the thesis uses a rigorous
full-wave mode-matching method, considering finite metal-strip
thickness and conductivity, to investigate the leaky dominant
modes on symmetric coupled microstrips with and without
superstrate and on a finite-width conductor-backed CPW. This
work demonstrates the significant effects of the top cover over
these structures and proves that the even leaky dominant mode is
an additional parallel-plate mode perturbed by the presence of
the strips, which is different from the phenomenon that the odd
leaky dominant mode is a conversion or evolution from the odd
bound dominant mode. Moreover, a HEMT-based amplifier
integrated with an arched microstrip line is developed for an
oscillator-type active antenna. The microstrip line serves as a
feedback circuit of the oscillator as well as a radiating
element. Two microstrip-slotline transitions are used for
interconnecting the amplifier and the leaky-wave antenna
feedback loop, and thus no DC blocking capacitor is required.
The far-field patterns of the arched antenna and the circuit
performance including the self-mixing feature of the active
antenna are presented.
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