Design and implementation of a novel wideband dual-polarised transmitarray antenna based on tightly coupled cross dipole cells

Abstract

A novel broadband dual-polarised transmitarray antenna (TA) utilising tightly coupled cross dipole cells is proposed in this work. The transmitarray cell using the tightly coupling wideband principle comprises two radiation patches designed as two orthogonal planar dipoles with four interdigital capacitors, two meandered parallel plate transmission lines, and a ground. Each cell has a square shape and a dimension of approximately 0.28 ${\lambda }_c$ where ${\lambda }_c$ is the wavelength at central frequency 5.5 GHz. The transmitarray cell can achieve 475° phase shift at central frequency and transmission magnitude better than −2.5 dB within the working band. To verify the feasibility of this design, a tightly coupled dual-polarised transmitarray antenna (TCDPTA) is modelled and manufactured. The transmitarray aperture size is approximately 4.1 ${\lambda }_c$ $\times$ 4.1 ${\lambda }_c$. The simulation and measurement illustrate that the TCDPTA has stable and distortion-free main beams whose side lobe levels are generally below −10 dB in the band of 3.0–8.0 GHz. The measured gain at central frequency is 16.2 dBi and peak gain is 19 dBi at 7.5 GHz. The working bandwidth is 90.9% and 3 dB gain bandwidth is 66.7%. The measured cross-polarisation levels are below −15 dB at axial direction. This TA has potential applications for high-date-rate communication and high-revolution radar imaging systems at C-band.