A Low Profile Modulated Metasurface Antenna for Multi-Beam Applications

Modulated metasurface is considered as a good candidate for low-profile multi-beam antennas. Usually, a superposition method of all impedance modulations for different beams is used. However, a limitation of this method is that a very small number of beams can be generated due to the mutual interference of different impedance modulations, which will lead to low gains and high side lobe levels. It is found that the source locations for each beam play a key role in interference suppression. In this paper, instead of using the time consuming full-wave simulation- based optimization, the optimal source locations are obtained by using the aperture fields calculated from the zeroth-order approximation of the currents on the surface. To verify the design concept, a five-beam modulated metasurface antenna has been designed, fabricated and measured, providing an angular coverage up to +/- 30 degrees. Good agreement between the simulation and measurement has been obtained.