# A Two-Port Dual-Band Dual-Circularly-Polarized Dielectric Resonator Antenna
## 1 Introduction  
Circularly polarized (CP) antennas have gained considerable attention due to their ability not only to mitigate multipath propagation effects and decrease polarization mismatch loss, but also to suppress Faraday effects caused by the ionosphere [1, 2]. Additionally, circularly polarized antennas do not require polarization alignment and are widely used in modern wireless communication, including satellites, unmanned aerial vehicles, wireless sensors, global navigation satellite systems (GNSS), and worldwide microwave access (WiMAX) [3]. This has therefore led to an increase in research on circularly polarized broadband antennas. Besides achieving circular polarization by various techniques, patch antennas are generally low-cost, low-profile, easy to manufacture, and they are used in numerous applications such as satellites, radars, GNSS, and wireless networks. However, microstrip patch antennas have relatively narrow impedance and 3-dB axial ratio (AR) bandwidths [4, 5]. Dielectric resonators (DRs) manufactured with a low-loss and high-permittivity material were implemented for the first time as an antenna by [PERSON] et al. [6] in 1983. Since then, dielectric resonator antennas (DRAs) have become one of the most popular microwave antennas. Compared to a patch antenna, a DRA has a higher radiation efficiency since no conductor loss occurs. Other attractive features of the DRA include its wide bandwidth, simplicity of excitation, and versatility in shape and material [7, 8]. These attractive features make the DRA an excellent antenna candidate for modern wireless communication systems [9]. Circular polarization can be achieved through DRA antennas primarily by modifying either the excitation mechanism or by using a special dielectricresonator (DR). A variety of CP DRAs have been reported so far, including wideband CP DRAs [10; 11], broad beamwidth CP DRAs [12; 13], dual/multi-band CP DRAs [14; 15; 16], and so on. Among these CP DRAs, dual-band dual-circularly-polarized (DBDCP) DRAs have gained intensive research interests, especially for satellite communications (SAT-COMs) [17; 18]. The dual-band antenna offers a low interchannel interference and a reduced size and weight since it works in two frequencies to simultaneously facilitate the uplink and the downlink channels. In addition, the CP rotating sense for each band is opposite to each other, thus further improving the interchannel isolation. However, despite these technical potentials, there are only a few works on DBDCP DRAs [17; 18; 19; 20; 21]. A metallic strip-loaded DRA reported in [18] produces a DBDCP performance, but with narrow axial ratio (AR) bandwidths of 5.2% and 4.1%. In [19], a cylindrical DRA excited by a microstrip feedline through an asymmetrical Swastik-shaped aperture was developed, reportedly showing the DBDCP performance of 5.5% for left-handed CP (LHCP) at the lower band (LB) and 8.8% for right-handed CP (RHCP) at the upper band (UB). In another work [20], three pairs of near-degenerate orthogonal modes of the fundamental TE\({}_{111}\) and the higher-order TE\({}_{121}\) and TE\({}_{131}\) of a rectangular DRA were excited simultaneously to yield a large AR bandwidth of 19.8% for LHCP at the LB and 6.1% for RHCP at the UB. The design using a combination of the DRA mode and slot mode in [21] achieved broad AR bandwidths of 27.1% for LHCP in the LB and 12.8% for RHCP in the UB. In this paper, we propose the design of a two-port DBDCP DRA. The DRA is fed by two 50-\(\Omega\) microstrip feedlines through a common cross-slot-coupled aperture to resonate at two pairs of near-degenerate orthogonal modes of TE\({}_{111}\) and TE\({}_{113}\) for simultaneously achieving dual-band impedance matching with RHCP and LHCP performances in the LB and UB, respectively. The antenna performance is first studied using ANSYS HFSS and is then verified through an antenna prototype that works in C-band.