A Transmitarray Illuminated by a Pencil Beam Source to Obtain Conical Beam With Fixed Linear Polarization and Circular Polarization

Abstract

A linear polarization matching with fixed linear-polarized conical beam antenna has the superiority in some applications compared with the radially linear-polarized conical beam antenna. In this communication, a transmitarray illuminated by a pencil beam source to obtain conical beam with fixed linear polarization (FLP) is presented. The pencil beam source is also used to obtain the conical beam with circular polarization (CP). To achieve good circumferential symmetry, the transmitarray elements are distributed on rings. And the dimensions of the double-ring elements on the surface of the transmitarray are adjusted to compensate for the phase delay of the wave from the horn phase center and form a desired phase distribution on the transmitarray aperture. Based on this mechanism, three different cone angles of the FLP conical beam transmitarray are designed. A transmitarray illuminated by a horn to obtain conical beam with the radius of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.25\lambda $ </tex-math></inline-formula> has been designed and fabricated. The simulated results show that its gain is higher than 9 dBi at the designed frequency 12.5 GHz with a cone angle of 40°. Measured results agree reasonably well with the simulated ones. The conical beam antenna with CP has also been simulated and designed using the circular polarized feed source illumination.