Broadband Circularly Polarized Microstrip Array Antenna With Curved-Truncation and Circle-Slotted Parasitic

This article presents a novel broadband circularly polarized microstrip array antenna for synthetic aperture radar system onboard Cessna 172 Aircraft. The antenna employs an 8x8 matrix formation with uniform element separation of 0.5 lambda and single-proximity-coupled strip-line feeding. The circular polarization wave generation uses a curved-truncation patch and a circle-slotted parasitic patch above it to realize the broadband circularly polarized antenna. The broadening of the axial ratio bandwidth (ARBW) applies a fully serial sequential rotation on the array feeding network. Meanwhile, the gain is improved using a circle-slotted parasitic patch with a floating cover on the top layer. The prototype antenna has a physical aperture of 270 mm x 300 mm with 1.1-kg weight. The prototype produces an impedance bandwidth of 1.5 GHz (29.3%), ARBW of 1.62 GHz (30.6%), a gain of 18.17 dBic, and aperture efficiency of 26%. The azimuth and elevation beamwidth achieved 12.7 degrees and 13.0 degrees at the center frequency, respectively.

Automated summary

This article introduces a novel broadband circularly polarized microstrip array antenna for synthetic aperture radar system onboard Cessna 172 Aircraft. The antenna design includes a unique array formation and element layout to achieve broadband circular polarization, improved gain, wide impedance bandwidth, and high aperture efficiency. The prototype antenna demonstrates impressive performance in terms of bandwidth, axial ratio, gain, and beamwidth.