Graduation Year

2003

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Ph.D, Tom M. Weller

Keywords

model, marchand, antenna, compensation, spiral

Abstract

This work examined the design and characterization of multilayer coplanar waveguide baluns and inductors. This work derives a design procedure that helps RF engineers design cost effective multilayer coplanar waveguide (CPW) spiral balun that works in the frequency range 1-8 GHz. The accuracy of the developed procedure has been proven by designing two balun circuits of different dimensions and simulating them using available commercial software, Momentum (MoM) and Empire (FDTD). The simulation results have shown good balun performance over the desired frequency range. Furthermore some of the designed balun circuits have been fabricated and measured and the results agree with the simulations. The smaller balun (2.4 mm x 1.4 mm) with a minimum spacing of 25mm works very good in the frequency range 4-8 GHz with a 4 GHz operational bandwidth (OBW) and 5o phase difference and 0.5 dB amplitude imbalance.

The larger balun (5.6mm x 3.0 mm) with minimum spacing of 100mm works well in the frequency range 2-4 GHz with a 2 GHz operational bandwidth (OBW) and 10o phase difference and 0.5 dB amplitude imbalance. Such a large-size balun is suitable for a new fabrication technique called Direct-Write. This thesis focuses on techniques that can be used to enhance balun performance, it has been shown through this work that adding some capacitance at certain points in the balun circuit will decrease both the phase difference and the amplitude imbalance of the balun. Some of these techniques were discovered through the thesis work and the other techniques were used before, but for different balun structures. An additional study to the effect of the ground plane on the spiral inductor model is included herein.

Formulas for the inductance nominal value in the existing CPW ground plane for some spiral inductors are derived here, in addition to the derivation of an RF spiral inductor model that is independent of the ground plane. The importance of this model lies in its necessity in designing an antenna dipole loaded with lumped elements (in the absence of ground plane) to control the antenna electrical length without changing its physical length.

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