Gain Enhancement Stretched SIW Slot Antenna Using Higher Order Modes

A stretched substrate integrated waveguide (SIW) slot antenna operating at higher-order modes is proposed and investigated to enhance gain. The concept of stretched higherorder modes is introduced in the SIW slot antenna. Besides, the stretch coefficient is controlled below 1. By genetic algorithm (GA) within a limited range of stretch coefficients, we can calculate optimal values for the stretch coefficient, electric field amplitude ratio, and phase difference of the slots to maximize gain. A stretched SIW slot antenna is fabricated and measured. The measured result shows that the proposed stretched SIW slat antenna has a $\mathbf{- 1 0} \mathrm{dB}$ impedance bandwidth from 20.5 GHz. The measured peak realized gain is $\mathbf{1 0. 2} \mathbf{~ d B i}$ at 20.8