Miniaturized 3-dB Branch-line Hybrid Couplers Using Distributed Capacitors and Defected Ground Structure
Date Issued
2011
Date
2011
Author(s)
Tsai, Kai-Yu
Abstract
Reducing the size of a 3-dB branch-line hybrid coupler without significant performance degradation is the main purpose of this thesis. Two techniques are used in order to achieve this goal: first is the application of the finger-shaped or leaf-shaped distributed capacitors; and second is use of defected ground on the bottom metal of standard PCB.
In the first part of this thesis, the finger-shaped or leaf-shaped distributed capacitors are proposed in the design of a 3-dB branch-line hybrid coupler in order to increase the capacitance between ports. As a result, the size of a 3-dB branch-line hybrid coupler could be substantially reduced. Two samples of miniaturized branch-line hybrids at 836.5MHz using the design of the finger-shape and leaf-shape structure have been fabricated and measured. Without significant performance degradation, the physical sizes of the fabricated branch line hybrid couplers are reduced by 70% and 73%, respectively.
In the second part, the defected ground design is applied to the leaf-shaped hybrid to further minimize the size. Defected ground creates an eddy current disturbance underneath the coupler. By designing an appropriate etched pattern, the induced current is interrupted to enhance circuit inductance. The size of coupler can be reduced accordingly. A miniaturized branch-line hybrid with leaf-shaped capacitors and defected ground at 836.5MHz has been fabricated and measured. The physical size of the branch line hybrid coupler is reduced by 86%.
Subjects
miniaturized hybrid coupler
distributed capacitors
defected ground structure
shunt capacitor
split-ring resonator
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-100-R98942002-1.pdf
Size
23.32 KB
Format
Adobe PDF
Checksum
(MD5):a38b58d7c846535c84140ac6bef9a496