Publication Date

8-2018

Date of Final Oral Examination (Defense)

6-15-2018

Type of Culminating Activity

Dissertation

Degree Title

Doctor of Philosophy in Electrical and Computer Engineering

Department

Electrical and Computer Engineering

Major Advisor

Hani Mehrpouyan, Ph.D.

Advisor

Nader Rafla, Ph.D.

Advisor

Hao Chen, Ph.D.

Abstract

Adaptive beamforming antennas open a new venue for research to achieve high data rates. Such antennas are of interest at higher frequencies, especially at millimeter-waves. Millimeter-wave band ranges from 30 GHz - 300 GHz. There is an ample bandwidth available in this spectrum. However, due to the significant path loss at high frequencies, there is a need for better error correction schemes and adaptive beam-forming antennas for this frequency band.

The goal of our research is to design a novel adaptive beamforming smart antenna that is low cost, compact, power-efficient and less complex. Based on our recently awarded US patent, we have devised a novel beamforming technique in which phased array and parasitic array approaches are used in conjunction with each other. Conventionally, phased array or switched array techniques are used in smart antennas for beam-steering. In phased array antennas each antenna element has a separate excitation. Therefore, such antennas are costly and impractical for use in everyday communication devices. Switched array antennas are cost-effective and simple to implement, but the antenna beam can only be formed at a predefined location.

Our proposed novel beamforming technique is based on a mathematical model. After mathematical modeling, the antenna is simulated in Ansoft High Frequency Structure Simulator (HFSS). Results of the simulated model in Ansoft HFSS and the mathematical model are in close agreement with each other, Ansoft HFSS uses the finite element method (FEM) for complex electromagnetic computations. Antenna design consists of two circular arrays of six parasitic elements. Each array has an active element in its center and there is a fixed phase difference between excitation currents to the active elements. The beam is steered either by changing the phase difference between excitation currents to the active elements or by changing reactance of the parasitic elements. Our technique is novel as this is the first time switched parasitic array and phased array approaches are efficiently used in conjunction with each other. After mathematical modeling and simulations, two antennas are designed and tested. The first antenna is centered at 2.5 GHz. This antenna is used for proof of concept. The second antenna is centered at 28 GHz. The 28 GHz band will play a key role in the next generation of wireless networks, i.e., 5G. The antenna hardware testing results are also in line with the mathematical and the simulated models. This dissertation aims to provide an overview of smart adaptive beamforming antenna design, propose a mathematical model for novel hybrid beamforming, present the application of the proposed antenna in satellite communication and airborne communication, and demonstrate the validity of the design via software simulations and hardware testing.

DOI

10.18122/td/1432/boisestate

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