A Broadband Printed Monofilar Square Spiral Antenna : A circularly polarized low-profile antenna.
This article presents a novel circularly polarized (CP) wide-band printed monofilar square spiral antenna (MSSA) with a low profile and 50-X input impedance, as well as a technique to improve the overlapped bandwidth and reduce the profile of a conventional MSSA. To extend the application of the present design to an array antenna, a square cavity is introduced. This simple and low-cost approach results in a wide-band printed MSSA with high directivity. To verify this design concept, antenna prototypes operating at Ku frequency band have been designed and fabricated. Simulation and measurement results show that the present designs have more than 16% 10-dB return loss and 3-dB axial ratio (AR) bandwidth within the same frequency range with high radiation efficiency. The beam-scanning performance of the array antenna using the present design was investigated, and the calculated results suggest that good CP performance is obtained during the beam scanning. The advantages of our MSSA design are wide overlapped bandwidth, low profile, flexibility in antenna performance tuning, and easy fabrication. The present antennas have the potential to be used in small satellites such as microsatellites and CubeSats for tracking, command function, and data downlink applications.