Sidelobe Suppression of Metalens Antenna by Amplitude and Phase Controllable Metasurfaces

Amplitude and phase controllable metasurfaces are proposed to suppress the sidelobe levels (SLLs) of a metasurface lens (metalens). The amplitude-control metasurface is responsible for controlling the transmission amplitude with its unit cells' phase shift variation less than +/- 10 degrees. The phase-control metasurface is responsible for transferring the spherical incident waves to plane waves with its unit cell covering 360 degrees transmission phase shift, while the transmittance remains higher than -1 dB. Both the metasurfaces are with symmetrical structures for dual-polarization. By integrating the amplitude and phase controllable metasurfaces, a 9.7 lambda(0) x 9.7 lambda(0) metalens operating at 28 GHz 5G bands is designed and successfully suppresses the SLL. Within the 3 dB gain bandwidth from 26.0 to 29.0 GHz, this metalens antenna achieves the SLL lower than -20.9 dB in H-plane and lower than -17.3 dB in E-plane. The maximum gain is 23.4 dBi at boresight, and the achieved SLL is -16.3 dB as its scanning angle reaches the maximum of +/- 29 degrees. Compared with the phase-only metalens, the proposed metalens antenna realizes the maximum and minimum SLL suppression of 9.8 and 3.4 dB within the 3 dB gain bandwidth at a price of a gain drop of 0.8 dB at the designed frequency.