Abstract
In this paper, a multi-shell spherical dielectric lens antenna is synthesized to radiate multi-beams with optimum shaped patterns for radio coverage at millimeter wave (mmW) frequencies. In particular, the design considers the composing characteristics of discrete multi-shell Luneburg lens antenna as an initial structure, and synthesizes its permittivity and sizes of dielectric shells to produce relatively shaped main beam patterns rather than conventional pencil-shapes. It targets to minimize inter-beam overlapping transition regions with slowly varying power density in the coverage boundary, and therefore reduce the ping-pong effect of inter-sector handovers to potentially minimize the inter-cell interferences arising from the over-large gain of pencil beam when the user equipment (UE) is at near the sector boundary far-off the beam peak. After the synthesis, the antenna is implemented at 38 GHz with both numerical simulation and measurement results shown to validate the concept. Successfully validation on the feasibility of beam synthesis in comparison to that of Luneburg lens antennas has been achieved. Discrepancy in fabrication to potentially result in slight radiation degradation is also discussed.
Highlights
Cellular mobile communication antennas at millimeter wave frequencies require high gain radiation to compensate electromagnetic (EM) wave propagation loss in air [1]
This paper presents a shaped-beam synthesis of multi-shell lens antennas [7], [9]–[15] to optimize the radio coverage by shaping the main beam’s radiation patterns
In contrast to previous works of Luneburg lens optimization, which either minimize the estimation error of permittivity [10] in a least square error (LSE) sense, or enhance the gain and reduce sidelobe levels (SLLs) [12], [13], this paper focuses on the main beam pattern with a target to reduce the inter-beam overlapping and minimize gain variation within the coverage area, which may better retain the power control stability during connection in mobile communications
Summary
Cellular mobile communication antennas at millimeter wave (mmW) frequencies require high gain radiation to compensate electromagnetic (EM) wave propagation loss in air [1]. These two lenses are both composed of 10 dielectric shells (including the air), and are fed by the radiations of rectangular waveguides of 0.7 × 0.35λ2 in cross-section with a tight placement next to each other, where λ is the wavelength of free space.
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