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Abstract-A novel time-reversal subwavelength transmission technique, based on pulse shaping circuits (PSCs), is proposed. Compared to previously reported approaches, this technique removes the need for complex or electrically large electromagnetic structures by generating channel diversity via pulse shaping instead of angular spectrum transformation. Moreover, the pulse shaping circuits (PSCs) are based on Radio Analog Signal Processing (R-ASP), and therefore do not suffer from the wellknown issues of digital signal processing in ultrafast regimes. The proposed PSC time-reversal systems is mathematically shown to offer high channel discrimination under appropriate PSC design conditions, and is experimentally demonstrated for the case of two receivers.

In this paper, split-ring-based metamaterial sheets are designed for the purpose of achieving far-field subwavelength focusing, with the aid of a time-reversal technique. The metamaterial sheets are inserted into a subwavelength array consisting of four element antennas, with the element spacing being as small as 1/15 of a wavelength. Experiments are performed to investigate the effect of the metamaterial sheets on the focusing resolution. The results demonstrate that in the presence of the metamaterial sheets, the subwavelength array exhibits the ability to achieve super-resolution focusing, while there is no super-resolution focusing without the metamaterial sheets. Further investigation shows that the metamaterial sheets are contributive to achieving super-resolution by weakening the cross-correlations of the channel impulse responses between the array elements.

A compact planar sub-wavelength array is proposed, which has planar antenna elements etched with defect oval rings on the surface. The array demonstrates a property of 1/20 wavelength super-resolution combined with time-reversed electromagnetic waves. This design is simple in structure, easy to integrate and convenient for the printing design of circuit boards.Introduction: Time-reversed electromagnetic waves combined with some special microstructures can perform the focusing properties of super-resolution in the far-field region [1-3]. However, the microstructures used in [1] and [2] have metal wires in an inhomogeneous distribution, which is not beneficial to manufacture and production. In this Letter, we propose one planar sub-wavelength array of super-resolution. Its element interval is as small as 1/20 wavelength. This array can be easily integrated on a printed circuit board, and provides reference for sub-wavelength array design for high-performance mobile terminals.

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