Miniaturized Antennas for Platform-level Integration Scenarios.

Abstract

Efforts to reduce the physical dimension of an antenna have been vigorously studied for many decades. Through the collection of such efforts, the effects of size reduction on the performance of an antenna are fairly well understood matters in present day. The fundamental limitations established by Wheeler and Chu have been referenced as theoretical guidelines for acquiring smaller antenna size at the expense of radiation resistance, antenna Q (bandwidth) and polarization. While performance degradation is inevitable using contemporary materials as a resonant antenna volume decreases, it is still possible to overcome this restriction by taking a different route. Techniques such as facilitation of mutual coupling effects of parasitic elements, utilization of transistors, capacitive and inductive loading methods and artificial materials are now employed to mitigate and curb the inverse relationship between antenna volume and performance. This dissertation continues the path of designing fully integrated, electrically small antennas in a controlled manner. The contributions of this dissertation include:

A method to reduce the dimension of a cavity-backed slot antenna is synthesized. For a simple straight slot antenna, this technique can reduce the overall occupied volume of the modified cavity backing the slot antenna by more than 65% without effecting the high radiation effciency of the antenna. This facilitates proper fabrication and integration of miniaturized slot antennas on multi-layer substrates.

A platform-integrated low-profile antenna with high isolation levels to its environment is reported. Through this approach, complex package-level designs and simulations can be greatly simplified as the antenna exhibits similar behavior when integrated as it does in open-space. The method enables the realization of unidirectional cavity-backed slot antennas with heights less than lambda/100, minimizing surface intrusion or protrusion for platform antenna implementations.

An infinitesimal electric dipole radiating vertical polarization with less than lambda/100 height is realized. The theoretical equivalence relation between a short electric dipole and a magnetic loop at resonance is valid under the following preconditions: 1) The existence of uniform in-phase magnetic current, 2) Impedance matching to the low radiation resistance of the magnetic loop. This dissertation is the first to satisfy both requirements to the best of my knowledge.