Multi-band Series-Fed Millimeter Wave Array Antenna with LP and CP Characteristics for 5G Applications

The article presents the multi-band, left-hand circular polarized antenna array for millimeter-wave applications. The single radiating element has an orthogonal feed configuration from the single port. Thus, by adjusting the length of the orthogonal feed equal to λ_1/2 at 28 GHz, an approximately 150° phase difference between the two points is achieved. As a result, a left-hand circular polarization is achieved. Further, the bandwidth and radiation pattern are improved by arranging the radiating element along the one-dimension array (in the y-axis) and feeding it in series at the center. This is to achieve maximum antenna efficiency and reduce the losses. Consequently, penta resonances are generated at 27, 28, 31.5, 34.25, and 37.2 GHz with decent bandwidths of |S11| ≥ 10 dB are 26.7-26.95, 27.31-30.1, 31.18-31.65, 34.2-34.4, 37.2-37.85 GHz. The array antenna has resulted in circular polarization (CP) at 28 and 37.5 GHz and linear polarization (LP) at other bands. The achieved radiation is a narrow beam in a broadside direction with a half-power beamwidth of < 12°. The antenna LP gain ranges from 12 to 14.4 dBi in the band of interest.