Wideband and Low-Loss Beam-Scanning Circularly Polarized Antenna Based on Air-Filled SIW

In this letter, a wideband beam-scanning antenna with circular polarization (CP) characteristics is proposed. The antenna is designed based on an air-filled substrate-integrated waveguide (SIW), which is composed of three layers of printed circuit board. Since the medium is dug out, the transmission structure has low-loss characteristics. An array of slots is etched on the top layer as radiating elements. Due to the fast-wave characteristic of the air-filled SIW, the antenna can radiate over a wide bandwidth. The proposed antenna is designed, fabricated, and tested. Within the frequency band of 12-18 GHz (40% relative bandwidth), the measured scanning angle is from 28° to -13°. The antenna axial ratio is below 3 dB at the corresponding maximal beam direction, and the gain is above 10.30 dBic over the whole band. This antenna has potential applications in the satellite and wireless communication systems for its advantages of wideband, low loss, CP properties, low cost in fabrication, and simplicity in design.