In this paper, a design of very compact microstrip bandstop filters based on complementary split ring resonators (CSRRs) is proposed. Two techniques of metamaterial miniaturization are used to optimize the physical and electrical size of the CSRR. The bandstop filter is produced by an array of miniaturized loaded CSRRs etched on the center line of a microstrip. The size of the proposed filter, is as small as 0.58 cm2, and its electrical length is very small with only 0.08 λ0), compared to a conventional bandstop filter, a miniaturization of a factor 5 while the bandstop performance is maintained. A very good agreement obtained between the measurement and the simulation results.
 J. B. Pendry, A. J. Holden, D. J. Robbins and W. J. Stewart, “Magnetism from Conductors and Enhanced Nonlinear Phenomena,” IEEE Transactions on Microwave Theory and Techniques, Vol. 47, No. 11, 1999, pp. 20752084. doi:10.1109/22.798002
 F. Falcone, T. Lopetegi, J. D. Baena, R. Marqués, F. Martín and M. Sorolla, “Effective Negative Epsilon Stop-Band Microstrip Lines Based on Complementary Split Ring Resonators,” IEEE Microwave and Wireless Components Letters, Vol. 14, 2004, pp. 280-282. doi:10.1109/LMWC.2004.828029
 J. Garcia-Garcia, F. Martin, F. Falcone, J. Bonache, J. D. Baena, I. Gill, E. Amat, T. Lopetegi, M. A. G. Laso, J. A. M. Iturmendi, M. Sorolla and R. Marques, “Microwave Filters with Improved Stopband Based on Sub-Wavelength Resonators,” Microwave and Optical Technology Letters, Vol. 46, 2005, pp. 283-286.
 J. D. Baena, J. Bonache, F. Martin, R. Marqués Sillero, F. Falcone, T. Lopetegi, M. A. Glaso, J. Garcia-Garcia, I. Gil, M. F. Portillo and M. Sorolla, “Equivalent-Circuit Models for Split-Ring Resonators and Complementary Split-Ring Resonators Coupled to Planar Transmission Lines,” IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 4, 2005, pp. 1451-1461. doi:10.1109/TMTT.2005.845211
 K. Aydin, I. Bulu, K. Guven, M. Kafesaki, C. M. Soukoulis and E. Ozbay, “Investigation of Magnetic Resonances for Different Split-Ring Resonator Parameters and Designs,” New Journal of Physics, Vol. 7, No. 1, 2005, p. 168. doi:10.1088/1367-2630/7/1/168
 R. Marques, F. Medina and R. Rafii-El-Idrissi, “Role of Bianisotropy in Negative Permeability and Left-Handed Metamaterials,” Physical Review B, Vol. 65, No. 14, 2002, Article ID: 144440. doi:10.1103/PhysRevB.65.144440
 H. Griguer, H. Lalj and M. Drissi, “SRR Miniaturization for Patch Antenna Stacked with Metamaterial Substrate,” Fourth International Congress on Advanced Electromagnetic Materials in Microwaves and Optics, Karlsruhe, 13-16 September 2010.
 F. Falcone, T. Lopetegi, J. D. Baena, R. Marques, F. Martin and M. Sorolla, “Effective Negative Stop-Band Microstrip Lines Based on Complementary Split-Ring Resonators,” IEEE Microwave and Wireless Components Letters, Vol. 14, 2004, pp. 280-282. doi:10.1109/LMWC.2004.828029'>http://chart.googleapis.com/chart?cht=tx&chl=%5Cepsilon%20" style="border:none;" /> Stop-Band Microstrip Lines Based on Complementary Split-Ring Resonators,” IEEE Microwave and Wireless Components Letters, Vol. 14, 2004, pp. 280-282. doi:10.1109/LMWC.2004.828029