A Compact Monopulse Circularly Polarized Slot Array Antenna for Airborne Applications

In most advanced communication systems, radio frequency (RF) front ends having high power capability, high gain, and low-profile antenna systems are desired. In this paper, a small, lightweight, high gain with improved impedance bandwidth and circularly polarized slotted waveguide array antenna with mono-pulse capability in Ku-band is presented. Target application of presented research is on-board radio links for airborne platforms such as Unmanned Aerial Vehicles (UAVs) with built-in tracking capability. The antenna presented in this study has three key components: a comparator network, a radiating slot array and a polarizer. Slotted waveguide arrays with longitudinal slots have linear polarization. Therefore, a multi-layer meta-surface based low cost polarizer is used to convert linearly polarized (LP) wave of antenna aperture into to radiating circularly polarized (CP) wave. The designed polarizer is a combination of meander and strip lines on thin dielectric substrates. The designed antenna is operating at 15 GHz and simulated using Advance Electromagnetic (EM) Simulation software. It is a an array of 6 × 8 radiating slots having peak gain >22 dB at 15 GHz, reflection bandwidth of 1200 MHz, axial ratio band-width >2 GHz and single plane mono-pulse capability. Polarizer has square shape unit cell of dimensions 5.1 mm×5.1 mm. The complete antenna including feed network and polarizer is compact with dimensions of 11 cm×11 cm×9 cm that makes it easy to house on an aircraft.