Dual-Polarization Cylindrical Long-Slot Array (CLSA) Antenna Integrated With Compact Broadband Baluns and Slot Impedance Transformers

In this letter, a realistic method for feeding the dual-polarized cylindrical long-slot array (CLSA) antenna is presented. A compact lumped-element balun with 2.5:1 bandwidth is designed, fabricated, measured, and used for feeding the dipole-mode, while a compact microstrip coupled-line impedance transformer is used for feeding the slot mode of the antenna. Simulation results of these feeds are compared to experimental measurements, and the overall performance of the dual-polarized CLSA antenna with these feeds is also simulated. Simulation results agree with measured data, and it is shown that this antenna has the capability of achieving four polarization modes [vertical, horizontal, left-handed circular polarization (LHCP), right-handed circular polarization (RHCP)]. The gain over 225-450 MHz ranges from -1.42 to -3.15 dBi for the dipole mode, -0.44 to -2.24 dBi for the slot mode, -1.76 to -2.70 dBic for the LHCP mode, and -1.80 to -2.68 dBic for the RHCP mode.