RESEACH OF - NEGATIVE STRUCTURE BASED ON SPLIT RING RESONATORS AND FERRITE PLATES WITH FREQUENCY CONTROL IN C-BAND Lenyk B. Y.1, Basyuk I. V.2, Chorniy V. S.3, Skripka S. L., Nechyporuk O. Y.4 Faculty of Radio physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv, Glushkova Ave., 4 G, 01601, Kyiv, Ukraine; 1e-mail:
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[email protected] Split ring resonators [1, 2] arouse much interest in the microwave range. The resonant frequency of this type of metamaterial highly depends on the geometry of the structure[3]. The problem of resonant frequency control limits the practical application of the SRR. So it use the models where inductance and capacity of the structure changed by electrically, magnetically, chemically, thermally or optically sensitive material [4 - 6]. We present results which were obtained using electromagnetic simulation and experimental research of split ring resonators (SRR) in the C - band. Also we demonstrate results of experimental research of the frequency adjustment of hybrid structure with three different ferrites in the presence of external dc magnetic field. Moreover we present that with increasing strength of magnetic field resonant frequency of hybrid structure shifts toward higher frequencies. According to the experimental results maximum speed of frequency adjustment is 0.5 MHz/Oe. Thus, without changing the physical characteristics of hybrid structures, but only changing the magnetic field we can achieve the desired resonant properties. Using software from ANSYS HFSS package it was modeled structure to get a resonance frequency within the research range. Thus we select structure which was consisted of 6 metallic NB - SRR rings printed on a dielectric substrate (Fig. 1). It was obtained following parameters of rings: external radius rext = 3.2 mm, inner radius r0 = 1.8 mm, width of the ring w = 0.4 mm. And following parameters of the dielectric substrate (RT/duroid 5880): dielectric permittivity ε = 2.2, thickness of the substrate d = 125 μm, width of the plate b = 8 mm, length a = 48 mm.
a) Fig 1. a) Periodic metastructure of NB – SRR rings, b) NB – SRR ring
b)
According to the modeling of metastructure resonant frequency is f0 = 5.4 GHz, width of resonance (level 3dB) is ∆f = 160 MHz. But we observed experimentally f0 = 5.54 GHz and ∆f = 144 MHz. Research of hybrid structure was made with three type of ferrites. We used YIG (Yttrium iron garnet) with following parameters: saturation magnetization 4πMs = 1780 G, dielectric permittivity ε = 15.1; Niсkel – ferrite with parameters: 4πMs = 5000 G, ε = 13.4; YAG (Yttrium aluminium garnet) with following parameters: 4πMs = 800 G, ε = 14.2. The geometric size of ferrite plates was the same as the dielectric substrate, the thickness was 1 mm. Experimental sample was placed in waveguide with geometrical size (48x24 mm2) and single-mode condition (3.25 – 6.5 GHz), external magnetic field was directed perpendicular to the thinner side of the structure. Using vector analyser we obtained the following magnitude frequency responses for hybrid metastructures (Fig. 2). It should be noted that we didn’t observe frequency of ferromagnetic resonance of each ferrite in the С – band.
а)
b)
c) Fig. 2 Magnitude frequency response of hybrid structure with a) YIG, b) Nickel – ferrite, c) YAG As a result we obtained the ability to control resonant frequency of the structure by changing magnitude of the magnetic field. It should be noted that we observed multiple resonances for all experimental hybrid structures, moreover each frequency resonance differently depended to a magnetic field. Also we observed changing form of the resonance curve. This effect may be associated with domain structure of each ferrite, because we used small values of the magnetic field and ferrite wasn’t in the saturation state. 1. J. B. Pendry. Magnetism from Conductors and Enhanced Nonlinear Phenomena // IEEE Transactions on Microwave Theory and Techniques 1999 – Volume 47. Issue 11. – p. 2075 – 2084. 2. K. Aydin, I. Bulu, K.Guven, M. Kafesaki, C.M. Soukoulis, E. Ozbay. Investigation of magnetic resonances for different split-ring resonator parameters and designs // New Journal of Physics 2005 - Volume 7 – p.168 – 183 3. E. Ekmekci, G. Turhan – Sayan. Comparative investigation of resonance characteristics and electrical size of the double sided SRR, BC – SRR and conventional SRR type metamaterials for varying substrate parameters // Progress in Electromagnetics Research 2009– Vol. 12 –p. 35-62 4. Jeremiah P. Turpin, Jeremy A. Bossard, Kenneth L. Morgan, Douglas H. Werner, and Pingjuan L. Werner. Reconfigurable and Tunable Metamaterials: A Review of the Theory and Applications 2014 – Volume 18 – p. 3 – 4 5. L. Kang, Q. Zhao, H. Zhao, and J. Zhou. Magnetically tunable negative permeability metamaterial composed by split ring resonators and ferrite rods // Optics Express 2008. - vol. 16 - no. 12 - pp. 8825–8834 6. Jonah N. Gollub, Jessie Y. Chin, Tie Jun Cui, and David R. Smith. Hybrid resonant phenomena in a SRR/YIG metamaterial structure // Optics Express 2009 – Volume 17 – Issue 4 – pp.2122 – 2131
