CPW-Fed Branch Line coupler
Date Issued
2006
Date
2006
Author(s)
Lin, Kai-Min
DOI
zh-TW
Abstract
Abstract
In the beginning of this thesis, the basic theory and characteristics of quadrature hybrid coupler, which is also known as branch-line couplers are introduced. Afterwards, we make use of 3-D coupling structures to realize branch-line couplers in multi-layered PCB. In practice, due to the quarter-wave length requirement, the bandwidth of a branch-line coupler hybrid is limited to 10-20%. But, the branch-line coupler we designed is different from the conventional structure. The broadband branch-line coupler has been developed to enlarge operation bandwidth by enhanced impedance matching design at port junctions. Hence, we achieve wideband performance by only one section.
At first, we make use of CPW-fed microstrip method to implement the 3-D coupling structures in a single-layered PCB. Using the 3-D coupling structures, the uniplanar circuit design implemented in a single layered PCB can be extended to multi-layered design. This kind of branch-line coupler has the advantages of wideband, flat response on transmission band, and DC current blocking.
Since the microstrip lines used in the CPW-fed microstrip branch-line coupler possess serious dispersion phenomenon and radiation loss. One can use strip lines to avoid these disadvantages. Therefore, we further use the method of CPW-fed strip lines to realize the 3D coupling structures to modify the branch-line coupler.
There are two main techniques for the transition between a microstrip and CPW. One is the electrical contact, and the other is the electromagnetic coupling. The former usually uses via hole for the electrical contact. The mechanism of the proposed transition for the later is base on the electromagnetic coupling between stripline quarter-wavelength open-stub and CPW quarter-wavelength short-stub. This transition design is capable of inducing strong coupling between CPW and stripline around the resonance frequency. Accordingly, we design two kinds of CPW-fed branch-line coupler in multi-layered PCB to improve insertion loss and radiation loss. Observed from the measurement data, the insertion loss of stripline type is better than that of microstirp type at the same center frequency.
Subjects
共平面波導
轉換
直交分合波器
CPW
Transition
branch-line coupler
Type
thesis
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