Analysis and Design Consideration of Millimeter-wave Rectangular Dielectric Resonator Antennas
thesisposted on 18.02.2018, 00:00 by Shanshan Zhao
Dielectric Resonator (DR) has long been recognized valuable in designing filters, oscillators and other millimeter-wave components. By removing the shield which is usually used for radiation prevention and applying lower dielectric constant materials, DRs have been brought to attention that they could also be treated as effective radiators, especially after a series of papers on cylindrical, rectangular and hemispherical dielectric resonator antennas published by Long et al.. Traditionally, dielectric resonator antenna (DRA) has been used in microwave range and advantages including small size, low loss, light weight, relatively wide bandwidth, ease of excitation and integration and so on. Recently, mm-wave range, especially 7G unlicensed band around 60GHz has been brought to attention and considered as the spectrum for next generation mobile communication system. Taken into account the demand of high speed, ease of integration and operation, a high-gain low-profile antenna with end-fire radiation pattern is required. Among all the shapes, rectangular DRA is much easy to fabricate in mm-wave range and has two degrees of freedom which is a good candidate for 60GHz high-speed antenna-in-package (AiP) design. However, the previous researches have been focusing on the broadside radiation with nearly omni-directional pattern. No thorough study has been carried out for the design of mm-wave low-profile high-gain rectangular DRA with end-fire pattern and planar excitation. In this thesis, Theoretical method for mode study has first been chosen and proven its validity for eigenmodes in the DRA. Then a more practical model with planar excitation suitable for board integration in mobile system is presented and the characteristics equations are revised and applied to this new model to determine the modes excited in it. The industrial mainstream material LTCC is used as the substrate for most of the examples. As for the low-profile DRA with relatively low dielectric constant, the most distinctive property is that it shows both the characteristics of dielectric resonator antenna and surface-wave antenna. Using end-fire gain as a criteria, the knowledge of surface-wave antenna is first applied to study the performance of the antenna with different dimensions. Then the standing-wave modes of DRA bring certain variation to the gain curve. Various situations are discussed such as single-mode and degenerate-mode operation. Finally, the design rule of thumb is suggested and design curve is provided for preliminary end-fire antenna design using LTCC in 60GHz. Another popular material of Rogers 4350 is used as the substrate material to illustrate the potential effect of additional directors. Off-centered feeding is also investigated and solutions of beam tilt are discussed. Based on these rules, several single antennas using different materials are fabricated and the results are discussed. Flip-chip technology is used to form the 1-by-1 T/R antenna system and certain measured and simulated data are compared. Eventually, 2-by-2 T/R antenna arrays can be integrated into the AiP system.