Design And Performance Evaluation Of Self-Adjusting Antenna For Independent Frequency And Radiation pattern reconfigurability

number: 
3385
English
Degree: 
Author: 
Mustafa Safaa Hussein Shubbar
Supervisor: 
Dr. Lubab A. Salman
year: 
2015
Abstract:

Optimal power handling is one of the primary concerns in wireless communications. Antennas with frequency, radiation pattern, and/or polarization reconfiguration capabilities can prove to be of much use in this regard. This thesis proposes the design and investigates the performance of a pixel monopole antenna with independent frequency and pattern reconfigurability for optimal power handling in wireless communications. The proposed design involves splitting the radiating aperture into driven and parasitic sections with independent pixelization schemes. In order to evaluate the impact of each of the fixed design parameters of the proposed antenna on its performance, a parametric study is conducted first on an initial monopole pixel design using full-wave MoM-based simulation. The investigated design parameters include the substrate’s permittivity and thickness, the ground-to-patch separation, the pixel-to-pixel gap size, and the pixel size itself. Subsequently, different switching states of the initial pixel antenna design are considered in order to identify those states that would allow independent frequency and pattern control benefitting from the symmetry feature of the proposed design. The covered frequency range extends from 2 GHz to 11 GHz. Next, a series of modifications are conducted on the initial pixel antenna design in order to allow as much independent as possible control of its frequency and radiation pattern responses. These modifications include the incorporation of parasitic pixel elements of different sizes placed in the plane of the driven elements matrix, one set of parasitic elements on each one of its three un-driven sides. The improvement gained by the introduction of the above modifications is demonstrated by considering representative switching states for different values of the design parameters and comparing the results in both the frequency and the spatial domains. The results clearly demonstrate that using a substrate with a dielectric constant of 2.7 or a thickness of 0.8 mm leads to a 30% increase in radiation efficiency compared to a substrate with a dielectric constant of 6 or a thickness of 2.4 mm. On the other hand, increasing the patch-to-ground separation results in a larger operational bandwidth. It has also been noticed that increasing the pixel-to-pixel gap size up to 53% of the pixel size while maintaining a fixed pixel size causes the lower and upper cutoff frequencies to shift downwards leading to a smaller operational bandwidth of about 2.5 GHz. However, varying the pixel-to-pixel gap up to 83% of the pixel size while maintaining a fixed radiating aperture or varying the width of interpixel connections from 5% up to 21% of the pixel width, has been seen to have no major impact on the antenna response. It has been also demonstrate that the introduced parasitic pixel elements have a negligible impact on the frequency response of the antenna while allowing a more flexible control of its radiation pattern, thereby maximizing its power handling capability. These results were reached at through extensive full-wave simulations using the Momentum simulator of Agilent’s ADS 2011.