RF-Microwave Circuitry
Relevant Publications: IEEE TDEI '15, IEEE ICIIS '15, BSc Thesis '14, IEEE ICIIS '14
Design of optimal passive and active RF and Microwave circuits and components.
#1. Microstrip Ring Resonators
Measurement of dielectric properties of copper clad printed circuit boards using microstrip ring resonators is a well-studied problem widely in use. The problem addressed here is different from this as the sample under test is difficult to copper clad. The sample is placed on a ring resonator fabricated on a printed circuit board of known dielectric properties and the properties of the test sample are obtained from the measurement of the resulting multilayer stack. Although the measurement of dielectric constant does not pose problems, the calculation of the loss tangent needs the radiation and conduction losses. Out of the two losses, estimation of radiation loss is a difficult task, firstly because the problem is multi-layer and, secondly because the dielectric properties of one of the layers (test sample) are unknown. As a result it is usually assumed that the radiation losses are negligible. This paper examines the effects of this assumption using accurate electromagnetic simulations.
#2. Asymmetric Coupler Design
The design and simulation of a wideband coupler for improved directivity is investigated. The coupled line coupler is considered for weak (or lose) coupling purposes. An improved bandwidth performance is achieved by increasing the number of stages of the coupled line coupler, thus resulting in a Multi stage coupler. The research focuses on the 3 stage coupler with optimally positioned capacitances, however the result can be easily extrapolated and generalized to any number of stages. An odd number of stages is considered for structural symmetry and wider bandwidth performance. The performance of the conventional multistage coupler, the compensation with a single capacitance, multiple capacitances and optimally positioned capacitances for both symmetric and asymmetric couplers are investigated in detail with special focus on the asymmetric couplers. This dissertation introduces the novel Pointer-Robust optimization scheme for optimal positioning and the asymmetric compensation for enhanced bandwidth-directivity performance. Several design examples and simulation results are presented and the results are confirmed by measurements. The results confirm the novel optimization scheme and compensation approach.
Maqsood Careem
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