Polarization Diversity Controllable Monopulse Antenna Array Design

The design of a compact and wideband circularly polarized (CP) Monopulse antenna is presented. Firstly, the small-sized antenna element (13mm
$\times13$
mm), with the impedance bandwidth (BW) of 80.5% (4.3-10.1 GHz) and axial ratio (AR) bandwidth of 48.1% (6-9.8 GHz), and the gain of 7.2 dBic is designed. The array structure consists of two rat-race couplers; two metalized via holes that generate sum and difference patterns, and four branch-line couplers for CP characteristic improvement. The proposed antenna is capable of controlling CP diversity in both sum and difference beams. Additionally, with 50% BW and 25% 3-dB AR results and also with null-depth of less than −48 dB, it is a convenient design for tracking purposes.