Summary: | 碩士 === 大葉工學院 === 電機工程研究所 === 84 === During the past three decades, the areas of microwave integrated
circuits(MIC)and microwave monolithic integrated circuits (MMIC)
have made significant advances. More and more components made of
MIC's and MMIC's are replacing the conventional microwave
components, such as power generators, isolators, mixers, and
filters, etc.. Compared to the conventional microwave
components, the MIC's and the MMIC's have the benefits of
wider bandwidth capability,reduced size and weight, easiness of
mass production, and higher system reliability, to name only a
few. Over the years, many transmission-line structures that
employe d the MIC's and MMIC's techniques have been proposed as
a means ofconnecting different microwave components. Microstrip
transmission line, withor without top perfect electric
conducting (PEC) plane or even entirely enclosed by a metallic
box, is one of the interconnects that habeen quite popular. Our
object in this report is to investigate the microstrip
transmission line with a top PEC plane.In practical development
of MIC's, people lay out the circuits on a grounded substrate
first. Because of the absenc of the top PEC plane, it is easy to
do post-manufacturing tweaking and readjusting the circuits, if
the performance of the circuits are not within the designers'
specifications. In order to prevent interfering with nearby
circuits to electromagnetic radiations, it is sometimes
inevitable to put the to-be-finished MIC components in a
metallic box. However, to simplify the manufacturing process, we
have another choice, i.e., putting another PEC plane above the
circuits to prevent radiatons. If the additional PEC plane is
too closto the circuit board, the behaviors of the circuits of
the characteristics of the open-type microstrip transmission
line may deviate too much from what was originally designed or
tuned to be. Therefore, there is a need to investigate the
effects of the top PEC planeon the behaviors of the circuits and
the characteristics of the transmission lines. In this report,
only the propagation characteristics of microstrip transmission
lines are considered. Many procedures have been successfully
applied to obtain the propagation characteristics on openand
shielded structures of microstrip transmission lines. The
quasi-TEM model provides a good solution only at low frequency
limit, but becomes increasingly inaccurate as the operating
frequency is raised. The spectral domain analysis (SDA) has
beenfound to be rigorous and accurate even at high frequencies,
but can handle conducting strips of zero thickness only. The
space domain electric field integral equation (EFIE) is also
considered rigorous and can handle conducting strips of
arbitrary cross section. However, the Green's functions used in
EFIE are highly singular when the source points and the
observation points are close to each other, thus making the
numerical integration not efficient. To overcome the problem of
highly singular Green's function, a rigorous mixed potential
integral equation (MPIE) formulation was proposed and applied to
various microstrip patches and microstrip transmission lines by
Michalski and Zheng. In this report, we use the MPIE formulation
to investigate the effects of the top PEC planes on the
propagation characteristics of a multiconductor transmission
line, where the conductors are of arbitrary cross section.
Computed dispersion curves and modal currents are presented and,
when possible, are compared with data available in the
literature.The numericalresults presented here include the
propagation constants of the eigenmodes in both the bound regime
and in the leaky regime. The results will help the circuit
designers to determine where to put shielding ground plane above
the open transmission line system in the final stage of the MIC'
s fabrication process.
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