Sub-wavelength UWB antenna array design for super-resolution focusing based on time reversal technique

In this paper, a subwavelength UWB antenna array is proposed to achieve far-field super-resolution focusing based on the time reversal (TR) technique. The TR electromagnetic waves have the ability of adaptive temporal focusing and super-resolution spatial focusing. Some subwavelength antenna array loaded with nonuniform distributed metal wires can rebuild evanescent waves and obtain subwavelength information. Here a subwavelength UWB antenna array, which consists of four planar elements with cross-shaped slots instead of metal wires, demonstrates a property of 1/4 wavelength super-resolution. Firstly, a shovel-shaped UWB antenna with the etched cross-shaped slots is designed to work at 3−10.47 GHz. The simulation results show that the bandwidth and radiation pattern of the proposed antenna are roughly the same as those of the traditional monopole patch antenna without the etched slots. The proposed subwavelength array contains the four planar elements overlapped at an interval of λ/4 apart from one another, where λ is the wavelength of the centre frequency. Four UWB antennas as the time reversal mirrors (TRMs) are placed on both sides of the antenna array symmetrically with a distance of 2λ. When one of the antenna elements emits a modulated Gaussian pulse signal with a bandwidth of 4–6 GHz, the four TRMs record the signal. Then the time-domain signals are reversed and emitted from the four TRMs at the same time. The signals received at the elements in the sub-wavelength array are recorded and their peak values are compared. The simulation results show that, combined with the TR technique, only the array whose elements with the etched slots on both radiating patches and grounds demonstrates a property of 1/4 wavelength super-resolution beyond the diffraction limit.