In this paper, we describe a4 × 4 microstrip patch array antenna with a high gain and low side lobe level (SLL) using a parallel and series combination feed network with different power distribution ratios. Several quarter-wavelength impedance transformers are connected, and the power distribution ratio is controlled by adjusting the characteristic impedance of the feed network. The optimized 4 × 4 microstrip patch array antenna has a S 11 < (-)10 dB impedance bandwidth of 220 MHz which is a fractional bandwidth of 2.1%. At 12.5 GHz, the antenna has a gain of 18.2 dBi and SLLs of-28.0 and-26.5 dB in the x-z and y-z planes, respectively. The size of the array antenna is 100 mm × 100 mm × 0.7874 mm (3.5λ o × 3.5 λ o × 0.028 λ oat 12.5 GHz).
This work was supported in part by Institute for Information & Communications Technology Promotion (IITP) grant funded by the Korea government (MSIP) (No. 2017-0-00959, University ICT Basic Research Lab).
