A Series-fed Traveling-wave SIW Slot Array Antenna Generating Two Orbital Angular Momentum Modes

Abstract

<p>A series-fed traveling-wave uniform circular array of sequentially rotated slot antennas producing two orbital angular momentum (OAM) modes is presented. The antenna operates at 10190 MHz, is built using a single layer of substrate integrated waveguide technology, and can be readily expanded to create additional modes from a shared aperture. A unique simulation-based step-by-step design procedure is presented, taking practically all functional features of a series-fed array into account. A novel formulation for computing the radiation pattern of an array with variable-polarization elements is also offered. The antenna’s performance is evaluated using simulated, calculated, and measured data, with a significant correlation between the three sets. The first mode is a left-hand circularly polarized (LHCP) antenna, with measured impedance, gain, and axial ratio bandwidth of around 8.2, 5.9, and 3.9 percent, respectively. The second mode, which has a measured impedance bandwidth of roughly 7.9 percent, also features an LHCP radiation pattern around the broadside null. The simulated radiation efficiency for the first and second modes is around 48% and 30%, respectively. Furthermore, the orthogonality bandwidth for two identical antennas placed 28 cm apart in front of each other is around 4.5 percent. The antenna's near-field radiation patterns are also studied.</p>