Authors: Ahmed H. Abdelrahman and Hao Xin
Source: FERMAT,Volume 19,Communication,June 26 – July 1, 2016
Abstract: Transmitarray antennas have received considerable attention in the area of high gain antennas. They combine the advantages of the microstrip antenna arrays and the lens antennas, leading to the light weight and low profile designs. A transmitarray antenna consists of multiple layers of planar array elements and an illuminating feed source. The transmission phase of each element is designed independently to convert the spherical phase front from the feed source into a planar phase front and focus the radiation beam with a high gain. However, a full transmission phase range of 360° cannot be achieved by a single layer of array elements, and therefore a design of multiple layers is required. 3D printing technology has recently attracted a growing interest in the microwave field as a novel manufacturing technique. This technology allows the rapid prototyping of 3D arbitrary structures at low cost. The goal of this work is to decrease the number of conductor layers using the 3D printing technology, thereby reducing the complexity and cost of designing transmitarray antennas. The design methodology is based on using two groups of unit cells. Each unit-cell group is composed of two layers of printed elements separated by a dielectric material. The two groups have the same dielectric thickness but different relative permittivities, such that the transmission coefficient phase range of each unit cell group is different from the phase range of the other group. When combining the two phase ranges, a full transmission coefficient phase range of 360° is obtained. A polymer-jetting 3D printing technology will be used to fabricate the proposed transmitarray aperture, which includes a mix of two different dielectric properties. As an example, Fig. 1 presents a parametric analysis of the two double-layer unit cells using an arbitrary conductor element. The two unit cells have the same substrate thicknesses equal to 0.4 wavelength, but different relative dielectric permittivity equal to 1 and 2.8, respectively. It can be noticed that a full transmission phase range of 360° is achieved with transmission magnitude better than -2 dB. These simulations were carried out using the commercial software ANSYS HFSS.
Index Terms: Transmitarray antenna, multilayer, transmission phase range, 3D printing.
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