Design of a Aperture-Coupled Pentad-Polarization Reconfigurable Microstrip Antenna

This paper presents a multi–layer pentad– polarization reconfigurable antenna with an intent to use in the sub–6 GHz spectrum. By employing two orthogonal aperture– couple switchable feed networks, the proposed antenna can operate in dual–fed and single–fed modes. At single–fed mode, linear polarization (LP) sense of horizontal and vertical polarization can be obtained. At dual–fed mode, +45° LP and circular polarization (CP) sense of right–hand CP (RHCP) or left–hand CP (LHCP) can be achieved by switchable microstrip feed line excitation. Each feed network contains two microstrip feed lines with quadrature phase difference and switching between the feed lines is achieved by integrating two PIN diodes. A 10–dB impedance bandwidth of 1.02% for LP and 1.19% for CP are attained. Furthermore, without applying any kind of isolation enhancement techniques, excellent isolation characteristic (<–35 dB) is achieved at the resonant frequency of 3.35 GHz. A 3–dB axial ratio bandwidth of 18.18% is achieved for two CP modes. The maximum gains of LP mode and two CP modes are 6.5 dBi, 6.32 dBic, and 6.58 dBic, respectively. Moreover, the proposed antenna shows good radiation pattern at each polarization state.