A High-Gain Controllable Radiation Nulls SIGW Filtering Antenna With Improved Selectivity for 5G Millimeter-Wave Applications

In this letter, a substrate integrated gap waveguide (SIGW) filtering antenna with controllable radiation nulls, high-gain, and improved selectivity for millimeter-wave applications is proposed. A novel coupling feeding network (CFN) topology using multiple paths based on SIGW is presented to obtain a bandpass filtering response with a center frequency of 31 GHz, which is verified by an equivalent circuit model. The sideband rolloff characteristics of this antenna can be independently tuned by the SIGW and CFN to achieve radiation nulls. Furthermore, the selectivity and gain of the antenna are improved, benefiting from SIGW's frequency cutoff property and suppression of edge electric fields, respectively. The filtering antenna is fabricated, assembled, and measured. The measured results show a suppression level of 19.6 dB, a bandwidth of 14.2%(<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$|S_{11}|$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt; -{\text{10}}$</tex-math></inline-formula> dB), and a peak realized gain of 9.6 dBi.