Wideband Dual-Polarized Octagonal Cavity-Backed Antenna with Low Cross-Polarization and High Aperture Efficiency

Abstract

Simultaneously enhancing multiple antenna performance parameters is a demanding task, especially with a challenging set of design goals. In this paper, by carefully deriving a compatible set of enhancement techniques, we propose a compact/lightweight/low-cost high-performance L-band octagonal cavity-backed hybrid antenna with multiple attractive features: dual-polarization, wide impedance bandwidth, low cross-polarization, high gain, and high aperture efficiency. The ground cavity is octagonal, which allows the antenna to have a small footprint, and, more importantly, low cross-polarization and high aperture efficiencies when compared to a commonly-used square design. The hybrid design relies on the resonance merging of two radiating elements, i.e., radiating feedlines and a conductive open prism, to form a wide impedance bandwidth. To permit polarization diversity and low cross-polarization, it is differentially and orthogonally fed. Herein, a series of parametric simulation studies on antenna configurations provide information on how to improve the impedance bandwidth and cross-polarization performance. To verify the simulation studies, an antenna prototype was fabricated and tested. Excellent agreement between the simulated and measured results was reached.

Gain Enhancement and Cross-Polarization Suppression of Cavity-Backed Antennas Using a Flared Ground Cavity and Iris

“…Our goal is to further improve both the gain and the cross-polarization performance of our previous OCROP antenna from [2] without compromising its impedance bandwidth. As aperture flaring has the capacity for gain enhancement with minimal impact on the impedance bandwidth, it was adopted to meet the above-mentioned design goal.…”

“…The antenna excitation ports are located on the sidewalls of the ground cavity, and therefore, the feedline length (i.e., 𝑙 + 𝑙 ) is a function of the aperture length. As a result, the impedance bandwidth varies with changes in the aperture length [2]. To avoid affecting the impedance matching, instead of flaring the entire ground cavity sidewalls, we add a flare to the aperture opening of the original non-flared ground cavity.…”

“…Same as the OCROP design, the open prism, sitting in the center of the ground cavity, is excited with two orthogonal pairs of differential feedlines to provide dual-polarization and low cross-polarization. The antenna consists of four parts: a conductive octagonal-shaped ground cavity, a conductive radiating cubic prism with no bottom face, two orthogonal pairs of differential feedlines, and a supporting dielectric substrate [2]. The only difference between an OCROP design and an OCROP-Flared design is the existence of the flared section of the ground cavity.…”

“…The simulations in this paper were carried out in ANSYS Electronics Desktop 2021 R1©. Due to the perfect geometrical and electrical symmetry, the performance for the two orthogonal polarizations of interest (i.e., X-and Y-polarizations) are identical [2]. Therefore, in the following simulation studies, we only demonstrate the antenna performance under the Y-polarized operation mode by exciting the Y-polarized differential pair with equal amplitude and 180 • out-of-phase signals while matching the X-polarized differential pair with 50 Ω loads.…”

“…Cavity-backed antennas are good candidates, as they can readily be designed and adapted to meet these applications. In [2], we presented a dual-polarized L-band octagonal cavity-backed radiating open prism antenna (we called it OCROP antenna) with the above-mentioned desirable features. It was compact, lightweight, and had excellent frequency scalability [3] and a wide impedance bandwidth of >50%.…”