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Mazhar, Waqas 1988-

One of the major challenges in deploying future millimeter-wave, wideband communication systems is the designing of wide impedance bandwidth, high gain and high efficiency front end antennas. Conventional metal antennas have disadvantages like narrow frequency bandwidth, high conductor loss, and low radiation efficiency which make them inadequate for such systems. Therefore, this thesis investigates the future potentials of the low loss (i.e., no conductor loss) and high efficiency artificial grid dielectric resonator antennas for millimeter-wave applications using deep X-Ray lithography (DXRL). 
In the first section, a new design approach is introduced, to enhance the feed versatility and design characteristics of the previously explored grid dielectric resonator antennas (GDRAs). For instance, the implementation of the multi-layer GDRAs technique has improved the impedance bandwidth performance of normal GDRAs from 5.5% to ≥12%. Secondly, the integration of the various feeding techniques such as conventional coplanar waveguide (CPW), capacitive CPW and inductive CPW feeds are successfully applied to GDRAs for mm-wave applications, which was previously limited to microstrip feed-line only due to grid to feed-line shorting issues. 
The power distribution networks are always very crucial in defining antenna array performance. The feed structures like microstrip corporate feed and series feed are not practical at millimeter-wave frequencies due to the high conductor and radiation losses. Therefore, in the second section, the substrate integrated waveguide (SIW) feeding mechanisms for one-dimensional (1D) and two-dimensional (2D) planar arrays are explored. Various wide-band, low amplitude and phase imbalance, SIW parallel feed networks are developed at 24 and 60 GHz for the large GDRA arrays integration.
In the third section, the X-ray lithographic procedure for the development of two different monolithic GDRA array layers is described: i) solid template frame GDRA array layer; ii) and strip template frame GDRA array layer. All design steps from the DXRL mask fabrication to sample exposure, sample development and electroplating are thoroughly investigated. 
In the fourth and the final section, the performance of the two proposed GDRA array approaches using SIW feed mechanism is evaluated. Contrary to ordinary large DRA arrays these monolithic GDRA array designs greatly help in mitigating the GDRAs to a feedline alignment problem, which may result in distorted radiation pattern and significant impedance mismatch. Furthermore, the use of thin rectangular micro-inclusions over more complicated I-beam structures has reduced the fabrication complexities as well as has enhanced the effective permittivity of the newly developed GDRAs up to 22.5 which results in compact and low-profile structures. The performance of the rectangular grid based monolithic GDRAs is characterized in two steps. In a first step, low profile single channel series fed 1×4, and 1×8 GDRA arrays are implemented using SIW longitudinal slot feed topology at 32 GHz with a maximum impedance bandwidth of 12% and a realized gain of 11.9 dBi. Moreover, the effect of the template frame thickness, frame permittivity and the inclusion heights on the antenna array performance is discussed in detail. While, in a second step, subarrays of 1×4 and 1×8 GDRA elements are further extended to 4×4 and 8×8, 2D-monolithic GDRA arrays with SIW parallel feed networks and which have successfully demonstrated an impedance bandwidth up to 18% and a peak realized gain of 19.8 dBi at 60 GHz. 
The proposed GDRAs offer exciting features such as wide impedance bandwidth, high gain and low cross polarization and are a promising alternative at mm-wave frequencies to conventional metallic patch antennas antennas which suffer from low impedance bandwidth and high conductor losses, as well as an alternative to high permittivity, conventional ceramic DRAs which are narrow band and hard to machine at mm-wave frequencies where fabrication tolerances become comparable with the operating frequency wavelength. Lastly, the high permittivity GDRAs are low profile antennas which can be easily integrated in compact mm-wave devices

METAL EMBEDDED ARTIFICIAL GRID DIELECTRIC RESONATOR ANTENNA ARRAYS AND SIW FEEDING MECHANISMS FOR MM-WAVE APPLICATIONS

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