Bandstop filtering for integrated substrate gap waveguide high‐gain and wideband slot antenna for 5G

Abstract

Slot antenna based on microstrip line and waveguide is a popular design for future 5G antennas. To improve performance of slot antenna, a high-gain wideband slot antenna based on integrated substrate gap waveguide (ISGW) is presented, in which a stepped impedance feeding line is adopted to broaden bandwidth, and ISGW is used to increase gain. First, the transmission characteristics and the effective relative permittivity of ISGW is discussed and calculated, with operation band from 25 to 45 GHz. The antenna has a passband of 24.9–38.1 GHz, that is, almost Ka band, and an average gain of ~9 dB. Further, bandstop filtering (BSF) characteristic is introduced in the above wideband antenna to achieve filtering antennas for 5G millimeter-wave (mm-wave) bands of 24.75–27.5 GHz for China, and 26.5–29.5, 27.5–28.5, and 37–40 GHz for n257, n258, and n260 of 5G new-radio (NR). The BSF is obtained by etching U-shaped CSRR on feeding patch of the antenna. First- and second-order BSF are achieved by etching first and second U-shaped CSRR on the antenna feeding patch, respectively, thus correspondingly one bandstop resonance at 34.6 GHz, and two bandstop resonances at both 32.5 and 34 GHz are obtained. It is found that the passband performance is unchanged, but the stopband radiation drops sharply at the boresight direction. The three antennas (wideband, and first- and second-order BSF antennas) proposed are all fabricated and verified.