Dual-Band Transmissive Metasurface With Independent Amplitude and Phase Control for Low Sidelobe Antenna Application

In this letter, a dual-band transmissive metasurface (MS) with independent amplitude and phase control is proposed. The element is formed by three metal layers separated by two substrates. The top and bottom layers are orthogonal metal gratings, and the middle layer is a patch etched with two double-split ring resonators (DSRRs) and an annular slot. By tuning the geometries and orientations of the outer and inner DSRR, the amplitude and phase in lower and higher bands can be regulated, respectively. The annular slot improves the amplitude of the two bands and eliminates the interference between them. Then, two dual-band transmitarrays with phase-only and amplitude/phase modulation MS are fabricated and measured. The former has aperture efficiencies (AEs) of 48.4%/45.8% at (9.2, 17) GHz with 3 dB gain bandwidth of 13% [(8.4 to 9.6) GHz]/7.2% [(16.2 to 17.4) GHz]. The latter achieves AEs of 29.8%/27.0% at (9.1, 17) GHz with 3 dB gain bandwidth of 17.4% [(8.4 to 10) GHz]/7.2% [(16.2 to 17.4) GHz], as its sidelobe levels are suppressed to −24.8 (−22.5 dB)/−26.2 (−24.9 dB) in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">xoz</i>- (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">yoz</i>-) plane.