Impedance-Transforming Coplanar-Waveguide to Stripline Transitions
Date Issued
2006
Date
2006
Author(s)
Huang, Guo-Shu
DOI
zh-TW
Abstract
In order to cooperate with the development of multi-layered millimeter-wave transceiver module, the multi-layered coplanar-waveguide-to-stripline transition is proposed to facilitate the interconnection between uniplanar MMIC and embedded microwave passive components in the multi-layered substrate, so as to establish the key component technology for wireless transceiver modules. Uniplanar lines such as CPW has received increased attentions due to their merits over the conventional microstrip line. Therefore, it is widely used for MMIC designs. While Stripline features the advantages of no radiation loss and can support TEM mode, and is a very good candidate for embedded microwave passive component design in multi-layered substrate. Since the two transmission lines situate at different layers, implementation of compact and low-loss interconnections through the multi-layered substrate is of practical significance. In this study, a CPW-to-stripline transition is discussed and thoroughly investigated.
The mechanism of the proposed transition is based on 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. As a result, the signal can be effectively transferred from upper CPW to embedded stripline through the electromagnetic coupling. In multi-layered circuit designs, vias are often used to transfer signals from the upper metal layer to the inner metal layer for the consideration of measurement and interconnection with other circuits. Misalignment of vias between layers could occur when more layers are used, which leads to shifts in transition frequency response and impedance matching, and becomes more serious as the operation frequency increases. Here, since the proposed transition requires no vias in the main circuit structure, we may reduce the shift in transition characteristic with fabrication error.
For the proposed transition structure, the effect of substrate thickness between CPW and stripline on the amount of electromagnetic coupling is also investigated. The amount of coupling is represented by the transformer turn ratio in the equivalent-circuit model. As a result, the proposed transition also possesses the capability of impedance transformation. Based on the impedance-transforming property of proposed transition, one may employ low-impedance thus wider stripline for embedded microwave passive component designs, such that the sensitivity to fabrication error may be further reduced. The proposed transition is also applied to the design of bandpass filter in 60GHz low-temperature co-fired ceramic transceiver module. The proposed transitions have the advantages of wide bandwidth, low loss, and may be designed to provide impedance transformation between CPW and Stripline. They are attractive in implementing multi-layered microwave and millimeter-wave transceiver modules.
Subjects
共面波導
帶線
轉接器
Coplanar-Waveguide
Stripline
Transition
Type
thesis
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