Flexible-Substrate Microstrip Antenna Fed By Substrate Integrated Waveguide That Follows Along Spacer For 5g Sub-6 Band

A feeding structure that consists of a thin flexible substrate integrated waveguide (SIW) fed to a thick microstrip antenna (MSA) is proposed. The flexible-substrate MSA is fed by an SIW that follows along a spacer. The SIW-to-MSA transition is through two lines in differential mode connected to the top and bottom of the MSA. The fabricated MSA has a frequency of 3.6 to 3.7 GHz, which is in the 5G sub-6 band. Excellent return loss and a measured radiation pattern that agrees with the simulation results are shown.