Millimeter-wave wideband circularly polarized antenna arrays using travelling-wave elements

Using travelling-wave elements, two planar antenna arrays are developed for millimeter-wave wideband circularly polarized (CP) applications. First, the aperture-fed travelling-wave element is designed. Stacked curl element is printed on the surface of the substrate to realize wideband axial ratio (AR) and impedance performance. Then, two antenna arrays using substrate integrated waveguide (SIW) and microstrip feeding networks are developed, respectively. Performance comparison between these two arrays are discussed. Finally, the wideband CP antenna array which is fed by the SIW network is fabricated and measured. The measured impedance bandwidth of the array is 35.4%, 3-dB AR bandwidth is 33.8%, and 3-dB gain bandwidth is 32.2% with a peak gain of 23.5 dBic. The overall bandwidth is 30.6% and good efficiency of about 70% is obtained because of the low-loss full-corporate SIW feeding scheme.