Optimization Study of the Stripline Resonator Technique for Dielectric Characterization

To properly design the microwave components such as transmission lines, filters, capacitors, inductors, and many others, it is important to know the characteristics of the construction materials at microwave frequencies. One of the most reliable techniques in material characterization at microwave frequencies is the coplaner coupled stripline resonator technique. This technique is an enhancement to the classical stripline resonator technique. In this technique, the measured resonance frequency and quality factor of the resonator are used to determine the complex permitivity. One of the main problems in this technique is the proper modeling of the coupling gaps. In this dissertation we will introduce an accurate model of the coupling gap, which will shows that the capacitive behavior of the gap is not pure capacitive as known before, but it turns into more complex one at higher frequencies depending on the dimensions of the gap primarily. The second main problem is the limitation in the frequency range for accurate measurements. At higher frequencies, the coupling reaches its peak value for a given stripline resulting in excessive loading to the resonator and thus a lowered Q value. In this frequency range, measurement of the dielectric properties looses its accuracy because the lowered Q values which means inaccuracies in determining the resonant frequencies as well as great error in determining the Qc and Qd terms. In this dissertation, attempts to remedy this problem by introducing two different approaches to get an improved design for the coplaner coupled stripline resonator are presented. The first approach to optimize the design of the coplaner coupled stripline resonator is based on optimizing the dimensions of the coplaner coupled stripline resonator three sections (coplaner, transition region, and the center stripline). In the second approach, a reactive stub (via) is introduced in the coupling gap between the coplaner line and the center stripline. The added stub is designed to improve the Q values of the structure resonances. Simulations of different designs of the coplaner coupled stripline resonator using different stub dimensions are presented. Advantages and disadvantages of these designs as well as the solution to their resonance frequency shift problems are discussed as well.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Electrical and Computer Engineering

Department dc:contributor.department

Electrical and Computer Engineering

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1999

Author dc:creator

• El-Bakly, Ahmed Mostafa

Chair dc:contributor.committeechair

• Riad, Sedki Mohamed

Committee members dc:contributor.committeemember

• Scales, Wayne A.
• Besieris, Ioannis M.
• Elshabini-Riad, Aicha A.
• Su, Wansheng

• Material Characterization
• Gaps
• Stripline Resonator
• Stripline

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-021599-133448

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/26217