A Design of Orthogonal Switchable Feed Networks Integrated Microstrip Antenna for Six Polarization States

Abstract

In this paper, an aperture-coupled microstrip antenna with polarization reconfigurability in the sub-6 GHz range is proposed. The proposed antenna can excite horizontal and vertical linear polarization (LP), +45°and -45°LP, right-hand and left-hand circular polarization (CP). To attain polarization reconfigurability, a square shaped patch antenna is excited by either single or dual-feeding mode with two orthogonal aperture-coupled switchable feed networks where each network has either a quadrature length shifter or a 180° phase shifter. Single port is used to excite horizontal and vertical LP. On the other side, switchable dual port excitation can produce +45°LP, -45°LP, RHCP, and LHCP. Basically, 180° phase shifter helps to achieve ±45° LP and quadrature length shifter is used to excite dual-CP sense. For wireless applications, the suggested antenna is more appealing due to its low cross-polarization level and good isolation in each polarization state. The proposed antenna has 10-dB impedance bandwidth (BW) of 1.17% for LP, 0.72% for LHCP, and 0.60% for RHCP. Moreover, 3-dB axial ratio (AR) BW is more than 2.50% for both CP senses. Better isolation characteristic (<-25 dB) is attained at resonance frequency of 3.356 GHz without utilizing any isolation improvement techniques. Besides, the maximum gain of two CP modes and the LP mode are 7.82 dBic, 7.68 dBic, and 8.90 dBi, respectively.