Hypersurface is an ultra-thin platform composed of subwavelength artificial units arranged periodically or aperiodically in two-dimensional plane, which shows a strong ability in regulating electromagnetic wave. In particular, the dynamic super surface can regulate the electromagnetic wave artificially and dynamically under the external control signal. At present, most of the dynamic hypersurfaces are tunable and reconfigurable. The function of adjustable hypersurface can achieve fine-tuning, but the function is similar; the reconfigurable hypersurface can obtain significantly different functions, but the number of functions is limited. In order to realize the real-time control and switching of many different functions, Professor Cui Tiejun and others proposed to introduce digital coding representation and field programmable logic gate array (FPGA) into the dynamic hypersurface design in 2014, realizing the field programmable hypersurface. Programmable super surface can realize many different functions on a single platform, and the functions can be switched in real time according to the written program. However, most of the existing programmable hypersurfaces can only show the programmable characteristics under the pre-designed specific polarized electromagnetic wave irradiation, and still show the static characteristics under other polarized electromagnetic wave irradiation. Because the programmable super surface can only be real-time regulated under the irradiation of a single polarized electromagnetic wave, and can only provide an effective information transmission channel, so it can only process multiple tasks on one channel in series, which restricts the ability of parallel processing of multiple tasks. In order to improve the information processing efficiency and multi task processing ability of hypersurface, researchers developed and designed a dual polarized hypersurface, which can show different electromagnetic responses under different polarizations, and then can provide two independent information channels in parallel. Compared with the single polarization hypersurface, the dual polarization hypersurface can realize more complex functions, such as multi-channel information processing, polarization division multiplexing and dual polarization aperture sharing. Therefore, more advanced functional devices can be realized based on the dual polarized super surface. However, the existing dual polarized hypersurfaces are static or only fine-tuning, and their functions cannot be switched by real-time programming, which greatly limits the multi-function of dual polarized hypersurfaces and their application in ultrafast switching and scanning systems.
In order to solve the above problems, the research team of academician Cui Tiejun of Southeast University and Professor Qiu Chengwei of National University of Singapore have designed a dual programmable hypersurface that can independently regulate the x-polarization and y-polarization electromagnetic waves. In order to realize the dual programming hypersurface, the researchers first carefully designed an active hypersurface unit which can independently adjust the reflection phase of x-polarization and y-polarization electromagnetic waves. The active hypersurface element has a special design of metal pattern, and two varactors are integrated in X and Y directions respectively. Through the two bias lines designed, the capacitance of varactors in X and Y directions can be independently controlled, and then the reflection phase of x-polarization and y-polarization electromagnetic waves can be independently controlled. In order to obtain dual programming hypersurface and realize multiple complex electromagnetic functions, the researchers use 24x24 hypersurface cells to array, which contains 48 independent control interfaces. In order to realize the effective control of dual programmable hypersurface with multiple independent control interfaces by a single FPGA, the researchers further designed and implemented the extended interface circuit and DC voltage conversion circuit. The extended interface circuit is mainly composed of decoder and latch, which can expand a few FPGA interfaces exponentially. The voltage conversion circuit is mainly composed of transistors and resistors, which can convert the output voltage of FPGA to the bias voltage required by the varactor in the dual programmable super surface. Therefore, the dual programmable hypersurface platform has rich programmability and can realize multiple complex electromagnetic functions. As an experimental demonstration, the researchers verified three different electromagnetic functions on a single platform: exclusive or logic operation for spin control of circularly polarized waves, constant frequency and large angle dual beam scanning and dual polarized aperture sharing. The researchers believe that the dual programmable super surface provides a new way to realize large-scale and highly integrated electromagnetic devices and systems, and is expected to be applied in advanced devices and systems such as wave based logical operation platform, high-speed scanning radar and multi-channel spatial optical processor. Relevant research results were published online on advanced science (DOI: 10.1002 / advs. 201903382) under the title of "polarization controlled dual programmable metrics". The corresponding authors are Professor Jiang Weixiang, Professor Cui Tiejun of Southeast University and Professor Qiu Chengwei of National University of Singapore. The first author is Zhang Xinge, a doctoral student of Southeast University. Guess you like it
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