Analysis, Design, and Applications of CMOS Synthetic Coupled Transmission Lines
Date Issued
2011
Date
2011
Author(s)
Tsai, Kun-Hung
Abstract
This dissertation presents the analysis, design, and application of the CMOS synthetic coupled transmission lines. The proposed coupled lines are designed in a meandered form for circuit miniaturization. The conventional even-odd mode analysis is not appropriate to apply due to the meandering structure, which is asymmetric. In the first part of this dissertation, the asymmetric coupled-line model is adopted for analyses and the equivalent model parameters are extracted based on asymmetric coupled-line ABCD parameters and S parameters. The Rc and Rp in the model is available for quantitatively define the symmetry of coupled lines. The proposed extraction procedure is then applied on a 3-dB directional coupler on 0.18-um CMOS technology. The results quantitatively show that symmetry of the coupled lines is well maintained. Symmetry of other coupled-line structures that degrade coupled-line symmetry such as loosely coupled lines and different bend direction are also analyzed based on this model. An equal-length bend design suitable for the CMOS synthetic coupled lines is proposed and has managed to improve symmetry on various structures. Three-line coupled lines have also been analyzed with the similar procedure. Two kinds of three-line bends are designed and compared their utility on different modes.
Chapter 5 presents the design and analysis of a high directivity coupler using the multi-conductor synthetic lines and interwound-spiral shape in 0.18-um CMOS technology. Parallel coupled lines are used to model the non-uniform point-symmetric interwound spirals. By applying a more general asymmetric coupled-line model, the circuit appears to be slightly asymmetric. The interwound spiral coupler demonstrates that the analysis is capable to be applied on structurally non-uniform circuits with space symmetry. The interwound spirals can be modeled more accurately as asymmetric coupled lines than symmetric ones in the design of high directivity directional couplers.
Chapter 6 describes a novel Marchand balun consisting of synthetic coupled lines and active circuits. By properly placing a negative resistance circuit in the Marchand balun, the active circuit is able to compensate the loss of coupled lines. Derivation of the proposed Marchand balun characteristics is provided. The complementary cross-coupled pair compensates the loss of coupled lines and reduces the total line-length required. The proposed Marchand balun operated on 24 GHz is designed and fabricated on 0.18-um CMOS technology. It achieves the desired lossless and out-of-phase balun performance with an area of 240 um × 270 um.
Subjects
Synthetic waveguide
CMOS
coupled lines
directional coupler
microwave circuit
Type
thesis
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