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In this paper, we propose a real-time reconfigurable metasurface unit-cell working at dual-band with polarization-independent manipulation of reflection and transmission wavefronts. The transmission and reflection phases of the designed digital programmable active element can be dynamically adjusted by the states of the PIN diodes. The unit-cell can be designed to respond to different functions in different frequency bands, which makes it more flexible in radiation characteristics. Both the simulation and experiment show that the element can achieve good reconfigurable performances. This work offers a new method for real-time dynamic control of forward and backward electromagnetic wavefronts in the entire space.

A novel amplifier-based transmissive space-time-coding metasurface is presented to realize strongly nonlinear controls of electromagnetic (EM) waves in both space and frequency domains, which can manipulate the propagation directions and adjust enhancements of nonlinear harmonic waves and break the Lorenz reciprocity due to the nonreciprocity of unilateral power amplifiers. By cascading the power amplifier between patches placed on two sides of the metasurface, the metasurface can transmit the spatial EM waves in the forward direction while blocking it in the backward direction. Two status of power amplifier biased at the standard working voltage and zero voltage are represented as codes "1" and "0," respectively. By periodically setting adequate code sequences and proportions in the temporal dimension, according to the space-time coding strategy, the amplitudes and phases of the harmonic transmission coefficients can be adjusted in a programmable way. A metasurface prototype is fabricated and measured in the microwave frequency to validate the concept and feasibility. The experimental results show good agreement with the theoretical predictions and numerical simulations. The proposed metasurface can achieve controllable harmonic power enhancements for flexibly configuring the power intensities in space, which enlarge and manipulate the quality of transmitting signals.

The reconfigurable metasurface (MS) with tunable electromagnetic scattering properties has had an impact on innovative communication applications. However, the widely studied MS controlled by direct-current (DC) bias requires complex physical control circuits in array wavefront encoding, while the light-controlledapproach of the light-controlled MS MSwith a controlladoes not. In this paper, we report a newble modulation range of reflection phase,and its unit is composed of a reflection phase element based on the varactor and an opticalinterrogation network (OIN) based on the photoresistor so that the phase distribution of eachMS unit could be independently programmed optically. To illustrate our approach, a 2-bit reflection phase MS with 10 × 10 units was fabricated and tested to achieve pencil beam scanning and orbital angular momentum (OAM) beam at microwave frequencies. The simulated and measured results verify the feasibility of the proposed design. Furthermore, all the OINs on the MS are connected in parallel and powered by the same DC voltage source, which simplifies the difficulty of array expansion in MS design with a large-scale array.