Coazial-SRR: a New Geometry to Drastically Reduce the Electrical Size of the SRR
The conventional Split Ring Resonator (SRR), proposed by Pendry 1 in 1999 acts like a magnetic resonator and has been used in several applications. For example: metamaterial lenses 2, microwave planar circuits 3, and frequency seffective surfaces 4. In all these cases it is desirable that the size of the resonator is small in comparison with the wavelength. However in practice, it is very difficult to make a SRR smaller than 1/10 of the resonant wavelength. The main goal of this work is to show that the coaxial-SRR shown in Fig. 1 has a size drastically smaller than the wavelength. This particle consists of two metallic tori, one inside the other like a coaxial cable. There are two gaps, one in the outer conductor and the other in the inner torus on the opposite side. The effectric currents flowing over the inner and outer conductor can be seen as one single torus of current whose small radius is the average, (r1 + r2)=2, and the same big radius r0.In such an approximation, there is an analytical formula that accurately gives its selfimpedance. At the same time, the two halves of the resonator behave like two capacitors allowing the displacement current to close the loop of current. Their capacitances can be calculated from the well-known capacitance per unit length of a cylindrical capacitor. It is then possible to get an analytical and easy formula for the resonance frequency of the particle. In Fig. 2 the effectrical size (diameter/resonant wavelength) is plotted for two different cases. This figure clearly shows how the effectrical size of the coaxial-SRR quickly goes down to zero when r1 tends to r2. In order to check the theoretical prediction of the resonance frequency we have simulated the excitation of the particle by a TEM wave, in such a way that it is magnetically excited. For several different dimensions we got good agreement with the theoretical resonance frequency. We also applied the method in 5 to retrieve the effective permeability of a medium made of these particles and observed that it is strongly negative and can be much less than μ0 in a narrow frequency range (even in the case of a lossy metal). We have two main conclusions: this geometry miniaturizes the unit cell of a metamaterial and there is analytical solution of the equivalent LC circuit.
J. D. Baena J. Gollub D. R. Smith R. Marqués
Department de Electrónica y Electromagnetismo, Universidad de Sevilla, Spain Physics Department, University of California, San Diego, USA Electrical and Computer Engineering, Du Electrical and Computer Engineering, Duke University, Durham, USA
国际会议
Progress in Electromagnetics Research Symposium 2007(2007年电磁学研究新进展学术研讨会)(PIERS 2007)
北京
英文
889
2007-03-26（万方平台首次上网日期，不代表论文的发表时间）