射电天文用太赫兹三通带频率选择表面设计

Design of triple bandpass frequency selective surface in terahertz wave band for radio astronomy

本文设计一种基于单屏改进型开口谐振环(SRR)的太赫兹频率选择表面(FSS).改进型SRR谐振单元由具有开口缝的金属贴片组成,开口缝的物理尺寸会影响其阶跃特征阻抗特性.本文通过对改进型SRR单元结构建立LC等效电路模型,提取等效电路模型参数,并结合传输线理论,得到FSS的基频计算公式和谐波关系式.相比于传统均匀SRR,本文所提出的改进型SRR多频带传输的控制更为灵活.基于此特点,设计了一款中心频率依次为0.46 THz,0.86 THz和1.03 THz,可应用于射电天文的三通带太赫兹FSS.采用电磁仿真软件对影响该FSS传输特性的关键参数、周期间隔、小型化程度以及入射角敏感性等重要指标进行分析研究.结果表明,改进型SRR三通带FSS在三个通带内的反射系数分别为-37.6 dB,-13 dB和-19.6 dB,在0°-60°范围内均具有稳定的频率响应特性,且具有小型化程度高、损耗低等特点.这种三通带FSS在太赫兹频段射电天文方面有潜在的应用价值.

A single screen terahertz frequency selective surface （FS） using the improved split ring resonators （SRRs） is designed in this paper. The resonance unit of an improved SRR consists of an open seam metal patch, while the physical size of the open seam metal patch will directly affect the stepped impedance characteristics. In the paper, LC equivalent circuit model for the improved SRR unit structure is established to extract the equivalent circuit model parameters. Then the relationship between the fundamental frequency of the FSS formula and the harmonics is obtained from the basic theory of the transmission line. Compared to the traditional uniform SRR, the control of multi-band in the improved SRR is more flexible. It is an outstanding characteristic for multi-band FSS design. Based on this characteristic, the triple-band terahertz FSS centered at 0.46, 0.86 and 1.03 THz respectively is designed successively, which can be used in radio astronomy application. By using HFSS 13.0 electromagnetic software simulation, many important indicators such as the key parameters that affect the transmission characteristics of the FSS, periodic intervals, miniaturization degree and the sensitivity of the incidence angle have been studied and analyzed. Both the theoretical analysis and simulated results demonstrate the validity of the method. The triple-band FSS using the improved SRR has a lot of reformative performances. It is shown that the reflection coe？cients of triple-band FSS using the improved SRR are -37.6 dB,-13 dB, and -19.6 dB, respectively. On the other hand, it owns the stable frequency response characteristics in the 0°—60° range, which is beneficial to a large incidence angle. In addition, a high degree of miniaturization and the low loss characteristics are the another two significant advantages of this FSS. This triple-band FSS with improved SRR has potential applications in the terahertz frequency radio astronomy polarizer, beam splitter, mirror and resonator mirror, etc.