A W-band High Efficiency Multi-Beam Circularly Polarized Antenna Array Fed by GGW Butler Matrix

In this letter, a high efficiency multi-beam circularly polarized (CP) antenna array with the Groove Gap Waveguide (GGW) feeding technology for W band application is proposed. First, a wideband CP septum antenna element based on GGW structure is proposed. Two symmetrical septum blades filled in the widened rectangular waveguide are employed to obtain the circular polarization characteristics. The antenna has a simple structure with high tolerance, and the GGW technology reduces the machine difficulty, making the antenna easier to work in the higher frequency. Next, a 4 4 GGW Butler matrix with improved crossover is designed to feed the antenna array. Finally, a high efficiency W band four-beam CP end-fire antenna array is fabricated and measured. Measured results verify that the antenna has a wider impedance bandwidth of 17.6 % from 77.5 to 92.5 GHz for |S11| < -10 dB. The measured AR values of the main lobe range of four beams are almost less than 3 dB. Also, stable radiation patterns are obtained. The maximum gain and radiation efficiency are 15.29 dBic and 89.6%, respectively.