Frequency Controlled Polarization Rotating Transmitarray for Polarimetric Radar Applications

Polarization rotating transmitarrays can be used for enabling the detection of polarimetric scattering effects with radar systems. This work presents a compact Ka-band antenna-filter-antenna (AFA) unit cell design containing a 5th -order planar interdigital diplexer and three patch antennas for orthogonal polarizations. Thus, the linear polarization incident by a frequency modulated radar system can be preserved or rotated by 90° depending on the instantaneous frequency. The proposed transmitarray is developed for multilayer printed-circuit board fabrication with RO3003 layers composed with RO4450T bondply. Simulations are performed that include losses and copper surface roughness. The design exhibits 25 dB polarization separation and sufficiently low input return loss with a relative bandwidth of 11.4% at the radar layer and within two closely spaced bands with a relative bandwidth of 4.9% at the target layer.