Date of Award

6-25-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Systems Engineering

First Advisor

Hussain Al-Rizzo

Abstract

Modern wireless systems for implantable and wearable Body Area Network (BAN) applications have reached an advanced stage of design and development not possible in previous generations. Systems engineering techniques allow for modern wireless devices to be developed in a top-down approach to meet the necessary design requirements while utilizing modular architectures. A modular systems architecture is developed to form a platform for BAN systems design. The BAN systems architecture defines the requirements, physical architecture, and operational architecture. The antenna component of the system is researched in detail and prototypes are developed to meet the requirements of implantable and wearable BAN devices. The miniaturized implantable antennas are designed for medical monitoring devices such as wireless electroencephalogram (EEG). The antennas are compact in size and function in the MedRadio band of 401 MHz to 457 MHz. The wearable antennas are designed for worn, on-body BAN devices. These devices serve many applications in the area of personal health monitoring such as hospital patient monitoring, sports medicine, military, and space applications. The conformal antennas are developed for integration with clothing or other flexible garments. These antennas operate in the 5.2 GHz wireless Local Area Network (WLAN) band and the 5.8 GHz Industrial, Scientific, and Medical (ISM) band. A dual band bow-tie antenna is designed to communicate with implanted devices as well as base stations. It operates in the 915 MHz ISM band with a dipole like radiation pattern and in 2.45 GHz ISM band with a broadside radiating pattern. Tuning slots are used to adjust the TM30 mode resonance into the 2.45 GHz band. The base station antennas are developed to fulfill two needs, communication with on-body devices and precision location for deployed command centers. For the dual band circularly polarized array, four bow-tie antenna elements are sequentially rotated in position and phase. The resulting benefit is a significant increase in gain: 10.8 dB in the 915 MHz band and 2.9 dB in the 2.45 GHz band. The array size is reduced by using a high dielectric alumina substrate. For precise GPS location, a five element antenna array is developed utilizing proximity coupling to power the four surrounding elements. The center element is fed with two orthogonal and 90° phase shifted feeds to excite circular polarization. The proximity coupling allows for a compact array size by reducing the element edge spacing to 2 mm. The array exhibits a high gain across the GPS bands, from 8.8 dBi to 9.5 dBi at boresight, and provides an excellent axial ratio. Three fabrication methods used in this dissertation are wet chemical etching, computer numerical control (CNC) micro-milling, and conductive ink printing. Experimental testing methods for anechoic chamber configuration, S11 measurements, and gain measurements are described in detail. The experimental testing of a wearable antenna integrated with a system on chip (SoC) is conducted and results are presented for link budget and packet error rate (PER). Overall, the systems architecture, microstrip antennas, and experimental characterization methods presented in this dissertation advance the state of the art in wireless systems and microstrip antenna technology.

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