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Abstract-This paper presents the design, fabrication and measurement of a polarization insensitive microwave absorber based on metamaterial. The unit cell of the metamaterial consists of four-fold rotational symmetric electric resonator and cross structure printed on each side of a print circuit board to realize both electric and magnetic resonances to achieve efficient absorption of the incident microwave energy. Both the full wave electromagnetic simulation and the measurement on the fabricated absorber demonstrate high microwave absorption up to 97% for different polarized incident electromagnetic waves. To understand the mechanism, analysis is carried out for the electromagnetic field distribution at the resonance frequency which reveals the working mode of the metamaterial absorber. Moreover, it is verified by experiment that the absorption of this kind of metamaterial absorber remains over 90% with wide incident angle ranging from 0 • to 60 • for both transverse electric wave and transverse magnetic wave.

Abstract:We propose a polarization modulation scheme of electromagnetic (EM) waves through reflection of a tunable metamaterial reflector/absorber. By constructing the metamaterial with resonant unit cells coupled by diodes, we demonstrate that the EM reflections for orthogonal polarized incident waves can be tuned independently by adjusting the bias voltages on the corresponding diodes. Owing to this feature, the reflected EM waves can be electrically controlled to a linear polarization with continuously tunable azimuth angle from 0 o to 90 o at the resonant frequency, or an elliptical polarization with tunable azimuth angle of the major axis when off the resonant frequency. The proposed property has been verified through both numerical simulations and experimental measurements at microwave band, which enables us to electrically modulate the polarization state of EM waves flexibly.

In this paper, we analyze the wave propagation in a practical left-handed nonlinear transmission line with series nonlinear capacitance composed of two back-to-back connected varactor diodes. Detailed circuit analysis of the transmission line shows that by properly choosing the circuit parameters, the equation governing the wave envelope evolution can be reduced to a one-dimensional nonlinear Schrödinger equation, which supports dark solitons propagation. By transient circuit simulation, the soliton evolution has been demonstrated both in time and frequency domain with input signal of either a continuous wave or a Gaussian modulated pulse. It is also shown that increasing the dissipation in the transmission line metamaterials is helpful to form steady dark solitons in short transmission lines. The establishing of the Schrödinger solitons also results in the third harmonic generation in the transmission line, which may find practical applications in communication systems.