Starting with smartphones, mobile data traffic has exploded and is expected to continue to increase in the future. Therefore, studies on the millimeter wave band as the next generation communication are proceeding. The millimeter wave is particularly notable because it has a wider bandwidth than the currently used bandwidth and can implement phased array antenna in a relatively small space. Conventional end-fire antennas used in the millimeter wave have disadvantages that they have a length of more than half wavelength and are difficult to implement circularly polarized waves. Therefore, an end-fire antenna having a shorter length is required, and research on an end-fire circularly polarized antenna is particularly important.
This paper proposed a novel planar end-fire antenna that has a shorter length than conventional end-fire antenna by using long vias. Also, end-fire circularly polarized via antenna is realized by changing feeding position of via antenna. Since it is difficult to measure the antenna gain in millimeter-wave band in Korea, the research have studied at 10 GHz instead of millimeter wave. The proposed antenna uses three long vias on a FR-4〖(ε〗_r=4.05) substrate with a height corresponding to half wavelength of the resonant frequency. The proposed antenna has the impedance bandwidth of 15.6% at 9.5 GHz to 11 GHz and shows an antenna gain of 5.19 dBi. The end-fire circularly polarized antenna implemented by changing feeding position has a 3 dB axial ratio bandwidth of 5.29% at 9.76 GHz to 10.29 GHz and shows a circularly polarized antenna gain is 3.88 dBic.
Also, This paper propose a circularly polarized antenna using dual feeds and propose a superstrate and parasitic patch method for gain improvement.
