Millimeter-Wave Differentially Fed Single-Layered Circularly Polarized Antenna

A millimeter-wave (mmw) circularly polarized (CP) antenna in single-layered laminate is proposed in this letter. For performances, it yields obvious advantages in terms of profile (single layer), gain and bandwidth when compared with recently reported high-gain CP antennas. For design method is the first attempt to introduce I-shaped differentially fed slots to achieve enhanced bandwidth over the traditional slot antenna. Then, we add complementary dipoles to the same plane of the I-shaped slots, contributing to CP radiation. Then, we build 1 × 8 antenna array to increase the gain of the proposed CP element. For demonstration, a single-layered CP antenna array operating at 77 GHz is designed, fabricated, and measured. Measured results show that the overlapped bandwidth for impedance matching, axial ratio and gain is 13% [(72 to 82) GHz]. It realizes a flat in-band gains with a peak gain of 13 dBic. It is a promising candidate for mmw vehicular communications systems such as unmanned aerial vehicles (UAV) and motor cars, which require low profile, CP radiation and fast data transmission speed.