Graduation Year

2005

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Thomas M. Weller, Ph.D.

Committee Member

Lawrence P. Dunleavy, Ph.D.

Committee Member

Kenneth A. Buckle, Ph.D., P.E.

Keywords

Broadside coupled, Strip-line, Low profile, Detector, Sleeve

Abstract

Due to the rapid growth in the filed of RF and Microwaves circuits, the demand for smaller, faster, and more precise devices has increased. In this thesis, a compact shielded balun, a diode detector, and a broadband sleeve dipole are modeled and implemented resulting in optimal devices presenting accurate operation.

The balun circuit is designed to meet the need for a miniaturized device with broadband application. A balun is a transformer used to connect unbalanced to balanced circuitry, for example, the unbalanced connection from a power splitter (coax) to the balanced input (two-wire) of a dipole. The main objective for the balun discussed in this work is to serve as the feeding element of a printed dipole antenna operating from 1.35 GHz to 2.7 GHz. The main characteristics from this device that distinguished it from previous structures are its PCB compatibility, shielding (strip-line), and compact footprint. The effective output balancing capability of this balun is proven by the close agreement between the measured and simulated results.

Diode detectors are nonlinear devices used for extraction of DC from free space transmission, achieving RF to DC conversion. Detectors are of popular use today in RF-ID tags, virtual batteries, power scavenging, and many other portable applications. The dominating factor on the performance for this device is responsivity (mV/mW), which depends on the input matching, and in the relation of power level to input impedance. Here, an accurate comparison between model measured detectors has been accomplished, and a sensitivity study has been applied to the input impedance to represent variations in responsivity due to input mismatch.

At last an End-Loaded Planar Open-Sleeve Dipole (ELPOSD) is realized resulting on a printed dipole structure offering broadband response. An ELPOSD consist of a radiating element exposed to the effects of sleeves (parasitic), loading plates, and a thick substrate which contributes to a broad bandwidth. The main characteristic of its structure is the large number of parameters that can be optimized for maximum performance.

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