In this paper, we present the design, simulation, and measurement of a dual-band metamaterial absorber in the microwave region. Simulated and experimental results show that the absorber has two perfect absorption points near 11.15 GHz and 16.01 GHz. Absorptions under different polarizations of incident EM waves are measured with magnitude of over 97% at low-frequency peak and 99% at high-frequency peak respectively. Current distribution at the dual absorptive peaks is also given to study the physical mechanism of power loss. Moreover, it is verified by experiment that the absorptions of this kind of metamaterial absorber remain over 90% at the low-frequency peak and 92% at the high-frequency peak with wide incident angles ranging from 0 • to 60 • for both transverse electric wave and transverse magnetic wave.

The design, fabrication, and measurement of a triple-band metamaterial absorber are presented. The proposed absorber consists of a metallic planar spiral layer and a metallic ground plane separated by a dielectric layer. Experimental results show that the proposed absorber can perform absorption peaks at three resonant frequencies 9.86 GHz, 12.24 GHz, and 15.34 GHz with the absorption of 99.4%, 96.7%, and 99.1%, respectively. In addition, the absorber with the thickness of $\lambda /35$ at the lowest fundamental resonant frequency can operate at a wide range of incident angles under both transverse electric and transverse magnetic polarizations.

A multiple-band metamaterial reflective polarization converter (RPC) is proposed, which is composed of the dielectric substrate sandwiched with U-shaped metallic patterns and continuous metal film. The proposed U-shaped metamaterial RPC (UMM-RPC) can convert a linearly polarized wave to its cross polarized wave at the three resonant frequencies, which also can convert the linearly polarized wave to circularly polarized wave at other three resonant frequencies. Furthermore, the proposed UMM-RPC can maintain the same conversional direction at the three resonant frequencies when incident on a circularly polarized wave. The simulated and measured results are in agreement in the entire frequency range, and the polarization conversion ratio is over 90% for both linear and circular polarizations. The surface current distributions of the UMM-RPC are discussed to look into the physical mechanism. The proposed UMM-RPC has simple geometry but more operating frequency bands compared to the previous designs and can be used in applications such as antenna radome, remote sensors, and radiometer.