Reconfigurable passive RF microwave components

Date of Award


Degree Name

Ph.D. in Electrical Engineering


Department of Electrical and Computer Engineering


Advisor: Guru Subramanyam


Passive devices are the key elements in various Radio Frequency and microwave communication systems for functions such as switching, filtering and impedance matching. Passive devices realized with lumped elements exhibit losses from resistive and reactive parasitic behavior at higher frequencies, while distributed elements can achieve superior high frequency performance at a sacrifice of increased electrical lengths. In recent years, novel ideas have emerged for the design of RF/microwave components composed of transmission lines loaded with reactive elements (inductors, capacitors, and/or both of them in the form of resonators). These structures have been extensively shown to exhibit high controllability in their passband or stopband characteristics and electrical lengths. In this study, novel passive RF/microwave components in the form of ferroelectric varactors, subwavelength resonators, and Defected Ground Structures (DGS) are explored with an eye to design innovative RF/microwave devices such as filters and phase shifters. Specifically, main contributions are: Analog phase shifters realized with a cascade of thin film Barium Strontium Titantite (BST) varactors are demonstrated with a FOM of 24.5 degrees/dB at 8 GHz in an area of 0.45 by 3.3 mm² with a maximum DC bias of 8 V. A capacitive tuning ratio of 4:1 is achieved by apply 0-10 V dc bias on a single varactor unit with loss tangent under 0.01 up to 40 GHz. Capacitive loading capability is integrated to subwavelength resonators, making it possible for varactor loading. Resulting design is exhibits a notch depth of 48 dB at 116 MHz within an area of 6.1 by 9.65 cm², demonstrating its exceptional compactness without sacrificing the performance of band-rejection behavior. Modified Spiral-shaped DGS are presented with superior stopband performance and suppressed harmonics. Resulting design showed enhanced band-rejection behavior of around -50dB notch depth and less than 3dB insertion loss at 3.64 GHz within an area of 1.5 by 13 mm² with no higher order harmonics up to 10 GHz. In conclusion, this dissertation represents a successful demonstration of passive electrical small components with improved performance for RF/microwave applications.


Passive components, Radio frequency modulation Transmitters and transmission Frequency deviation, Microwave communication systems, Frequency stability, Electrical Engineering, Defected Ground Structures, Ferroelectric varactors, Subwavelength resonators, Reconfigurable RF tranceivers

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Copyright © 2016, author