In this paper, we propose a dual manipulation on wave-front in the X band based on a reconfigurable water-based metasurface. We design and test a metasurface integrated with a saline-water substrate and PIN diodes. We showed that the wave-front reflected by the metasurface can be modulated by both the degree of salinity and the diode pattern. With these two manipulating methods, the metasurface can not only control the amplitude of the scattered beams but also the beam deflection angles, which promises a more flexible and economical way to manipulate the wave-front. We provide two diode patterns to illustrate the performance. The experimental results agree well with our simulations, further verifying our designs. Superior than the conventional reconfigurable metasurfaces, the proposed metasurface combines both water salinity and diodes, which offers more possibilities in electromagnetic (EM) wave tailoring, as well as potential applications in sensing and detection.
In this paper, a dual-functional tunable coding metasurface is presented at X band based on water substrate, which can realize two different functions of specific scattering pattern and absorption at two different frequency ranges. Besides, by changing the salinity of the saline water substrate, the absorption performance in high frequency can be tuned, while the scattering pattern in low frequency remains unchanged. A coding element is designed with small water cavity in it. Three coding sequences with different radiation patterns are designed to verify these functions, and one of them is fabricated and measured. Experimental results have good accordance with our simulations, which demonstrates our schemes. We believe this work can not only broaden our design manner of metasurfaces, but also have plenty potential applications in biological and medical detection domain.
A tunable magnetically insulated transmission line oscillator (MILO) is put forward and simulated. When the MILO is driven by a 430 kV, 40.6 kA electron beam, high-power microwave is generated with a peak output power of 3.0 GW and frequency of 1.51 GHz, and the relevant power conversion efficiency is 17.2%. The 3-dB tunable frequency range (the relative output power is above half of the peak output power) is 2.25-0.825 GHz when the outer radius of the slow-wave structure (SWS) vanes ranges from 77 mm to 155 mm, and the 3-dB tuning bandwidth is 92%, which is sufficient for the aim of large-scale tuning and high power output.
In this paper, we propose a mechanically reconfigurable coding metasurface for wavefront manipulation to modulate the scattering beams as desired. The phase pattern on the coding metasurface can be harnessed by mechanically adjusting the thickness of the air substrate using four precise stepper motors. When the coding metasurface is illuminated with a plane wave, the magnitude of the scattering beams can be manipulated as desired. In addition, by applying specific coding series, different radiation modes of the coding metasurface can be realized by mechanical manipulation. To realize these functionalities, a square patch unit cell with an air substrate is employed here. The metallic patterns of metasurfaces are fabricated via Flexible Printed Circuit (FPC) technology, whose inherent property is conformality, implying a broader range of potential applications. To demonstrate our schemes, three metasurface patterns are designed and simulated. Two of them are fabricated and measured, showing good agreement with our simulations. Compared with other methods of tunable coding metasurfaces, the mechanically coding metasurface yields lower system complexity, lower cost, and easier fabrication. Besides, flexibility, the intrinsic specialty of FPC, enables the proposed metasurface unparalleled applications, such as security imaging, medical sensing, and various wearable devices.
In this paper, we propose new serial decoding of Luby transform (LT) codes over additive white Gaussian noise channels. LT encoder generates a potentially limitless number of encoded packets, and the decoder incrementally collects the packets to ensure successful recovery of the information. In the proposed algorithm, the newly coming code nodes are the first to pass the messages, and it is their neighboring source nodes that will receive these input messages and update their output messages; then, the next neighboring code nodes that have not been covered are to be included in the updating group; in this greedy way, the message propagation is conducted from neighbors to neighbors. The analysis demonstrates that the proposed algorithm has a faster convergence speed than the conventional ones, and simulation shows that it has an effective bit error rate performance. INDEX TERMS AWGN channel, fountain codes, LT codes, soft decoding.
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