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Abstract
This dissertation introduces defected ground structure (DGS)
implemented beneath coupled microstrip lines. The defected coupled line
(DCL) is modeled using both differential/common and even/odd modes.
The model was proven to be efficient in designing wideband baluns and
coupled lines based bandpass filters.
Both applications were implemented on low cost FR4 substrate with
thickness 1.5 mm and dielectric constant of 4.6. Excellent agreement
between circuit model, EM simulation and measurement was achieved.
When compared to their conventional counterpart, both applications have
superior performance and smaller overall circuit area.
The single-section and three-section baluns have a fractional
bandwidth of 40% and 70%, a maximum amplitude balance of 0.5 dB
(for both) and a maximum phase balance of 10 deg. and 3 deg.
respectively. Single-section and two-section DCL filters operating at 550
MHz, have rejection levels of the spurious resonances at 2f0, 3f0 as well
as 4f0 better than -11 dB and -14 dB for single-section DCL and doublesection
DCL, respectively.