This paper presents a two-dimensional infinite dipole array system with a mushroom-like high-impedance surface (HIS) ground plane with wide-angle scanning capability in the E-plane. The unit cell of the proposed antenna array consists of a dipole antenna and a four-by-four HIS ground. The simulation results show that the proposed antenna array can achieve a wide scanning angle of up to 65$^{\circ}$ in the E-plane with an excellent impedance match and a small $S11$. Floquet mode analysis is utilized to analyze the active impedance and the reflection coefficient. Good agreement is obtained between the theoretical results and the simulations. Using numerical and theoretical analyses, we reveal the mechanism of such excellent wide scanning properties. For the range of small scanning angles, these excellent properties result mainly from the special reflection phase of the HIS ground, which can cause the mutual coupling between the elements of the real array to be compensated by the mutual coupling effect between the real array and the mirror array. For the range of large scanning angles, since the surface wave (SW) mode could be resonantly excited by a high-order Floquet mode $\textrm{TM}_{-1,0}$ from the array and since the SW mode could be converted into a leaky wave (LW) mode by the scattering of the array, the radiation field from the LW mode is nearly in phase with the direct radiating field from the array. Therefore, with help from the special reflection phase of the HIS and the designed LW mode of the HIS ground, the antenna array with an HIS ground can achieve wide-angle scanning performance.
A Self-Matched Leaky-Wave Antenna for Ultrahigh-Field MRI with Low SAR
磁共振成像技术正朝着更高的磁场方向发展，以提高分辨率和对比度。然而，由于波干扰、组织不均匀性和高RF功率沉积，在7 T或甚至更高场的全身成像仍然具有挑战性。如今，在前列腺和心脏MRI中对人体的适当RF激励仅可能通过使用附接到身体的天线的相控阵列（所谓的表面线圈）来实现。出于安全考虑，此类线圈的设计旨在最大限度地降低局部比吸收率（SAR），从而在感兴趣区域保持尽可能高的RF信号。所有先前证明的方法都是基于共振结构，如e。例如，偶极子、电容负载回路、TEM线段。在这项研究中，我们表明，有一个更好的妥协之间的发射信号和局部SAR使用非谐振表面线圈，由于较弱的RF近场在其导体附近。有了这个目标，我们提出并实验证明了第一个漏波表面线圈实现为一个无槽微带传输线。由于其非共振辐射，与最先进的偶极线圈相比，所提出的线圈仅诱导略高于一半的峰值局部SAR，但在7 T下的前列腺成像中具有相同的发射效率。与其他线圈不同，漏波线圈在很宽的频率范围内将其输入阻抗与身体组织的平均波阻抗内在地匹配，这使得它对于7 T MRI的未来临床应用非常有吸引力。
