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This thesis contributes to the methods for evaluating the hardware performance of microwave imaging systems. Different aspects of this performance study are systematically described and evaluated through existing and novel performance metrics. The dynamic range of two vector network analyzers and their noise floor are explored. The effects of low noise amplifiers on the dynamic range of the microwave system are also studied. To increase the dynamic range and sensitivity of the system, a new high efficiency ultra wide band TEM horn antenna is introduced. The new antenna significantly blocks the electromagnetic interference from the surrounding medium. The parasitic coupling between the transmitting and receiving antennas has been reduced to a minimum. To estimate the efficiency of the antenna used in tissue imaging more realistically, a measurement based method is also proposed. The method models the two-port network formed by the antennas and the medium between them by signal flow graph. The medium’s electrical properties mimic those of tissue and can vary according to the application. Also, a new performance metric for microwave systems namely, the physical contrast sensitivity is proposed. Methodologies are proposed for its evaluation through measurements and through simulations. This enables the estimation of the smallest detectable target permittivity contrast or size for the system under evaluation. / Thesis / Doctor of Philosophy (PhD)

Radio Frequency Identification (RFID) systems use electromagnetic signals to wirelessly identify and track RFID-tagged objects. A reader transmits a carrier wave request signal to an RFID tag, which then transmits a unique identification signal back to the reader. Applications include supply chain inventory management, automated toll booth fee systems, sports event timing, restricted access control, pet monitoring and retail theft prevention. An RFID tag includes an antenna connected to a Radio Frequency Integrated Circuit (RFIC). RFID tags in the ultra-high frequency (UHF), industrial, scientific and medical (ISM) 902-928MHz band and global Electronic Product Code (EPC) 860‑960MHz band are powered passively (power extracted from carrier wave) and cost less than 15 cents per tag. Low cost UHF ISM RFID tags are an effective solution for tracking large inventories. UHF ISM tag antennas are typically planar dipoles printed onto a plastic dielectric substrate (inlay). Power exchange and transmit range is maximized when a tag antenna’s input impedance is conjugate matched to the RFIC input impedance. Since RFIC input impedance includes capacitive reactance, optimized antenna input impedance includes compensating inductive reactance. The T-match network adds inductive matching microstrips to conjugate match the RFIC. Narrowband (±1.5% of center frequency) and broadband (±5% of center frequency) lumped element designs also use inductive matching strips. Narrowband, lumped element design is accomplished through Smith Chart matching assuming lumped antenna elements. The broadband lumped element design is accomplished through a circuit transformation to an equivalent network and tuning the transformed circuit to resonate from 865MHz to 955MHz, with a center frequency of 910MHz. This thesis demonstrates a start-to-finish design process for narrow (±1.5% of center frequency) and broadband (±5% of center frequency) RFID tag antennas [3]. Furthermore, antenna matching element geometries are parametrically swept to characterize input impedance frequency response. Thesis accomplishments include (a) narrow and broadband antenna designs, (b) Keysight’s Advanced Design System (ADS) Momentum simulations, (c) antenna fabrication, and (d) differential probe impedance setup and antenna impedance measurements. Additional items include (e) impedance adjustments (f) tag range testing and (g) narrow vs. broadband matching technique comparisons. Antennas were fabricated in Cal Poly’s Graphic Communication Department by silk-screening silver conductive ink onto DuPont Melinix Polyethylene Terephthalate (PET) plastic. Impedance simulations are compared to fabricated antenna impedance measurements and range testing results.

Fractal antennas have the potential to provide multi-band solution through the property of self similarity that the fractal shape possess. This thesis deals with some modifications of the original Sierpinski fractal patch antenna, providing additional parameters to optimize in order to get the required radiation characteristics. A systematic study of the original Sierpinski monopole was done to gain an insight on the operation and multi-band behavior of the antenna and a similar study was done to find out why the patch version of Sierpinski lacks multi-band behavior. A Sierpinski antenna is designed by merging a grid and the fractal restoring the multi-band behavior. A stacked Sierpinski antenna is then designed by introducing an intermediate layer containing the triangular patch whose size is equal to that of the triangular hole in the fractal structure. The introduction of a gap in this structure improves the overall radiation pattern. The antennas are analyzed using the commercial IE3D package and the simulated radiation patterns are presented.

Ever since the dawn of radio communication systems, the antenna has been the key component in the construction and performance of every wireless system. With the proliferation of new radio systems, a cognitive radio is a radio that has the capability to sense, learn, and autonomously adapt to its environment. The hardware components are essential to optimizing performance. Antenna hardware for cognitive radio applications presents distinctive problems, since in theoretical terms, a cognitive radio can operate anywhere in the spectrum. The purpose of this thesis is to investigate a particular type of cognitive radio system and examine the potential affects the antenna will have on the system. The thesis will provide an overview of fundamental antenna properties, the performance characteristics of the particular antenna used in this research, and the system characteristics when the antenna is integrated. This thesis will also illustrate how the antenna and its properties affect the overall public safety cognitive radio performance. This information can be used to establish antenna selection criteria for optimum system performance. / Master of Science

No / In this study, a planar 4×4 phased array including modified E-shaped radiation elements is designed and fabricated to be incorporated in a Relay Station (RS) for realizing the communication with the super-ordinate Base Station. The proposed array provides 12.4% bandwidth at the 3.5GHz frequency band and gain of 21.2dB. Moreover a beamforming module is designed and simulated, aimed to be connected to the proposed array and realizing beamforming applications. This module provides 650 MHz bandwidth around 3.5GHz frequency band and is used for proper power division and controlling the amplitude/phase of the excitation currents.

No / A coplanar edge-fed triangular patch antenna with an integrated stubline is proposed for harmonic rejection application. The design is aimed to achieve a good impedance matching to 50 ω at the fundamental frequency while suppressing radiation of the first and second harmonics. The antenna is attended to operate around 1GHz, with acceptable power gain above 1dBi and less than -15dBi at the harmonics. Simulated and measured results show a reasonable agreement.

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No description available.