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The electromagnetic theory of diffraction and the Babinet principle are applied to the design of artificial metasurfaces and metamaterials. A new particle, the complementary split rings resonator, is proposed for the design of metasurfaces with high frequency selectivity and planar metamaterials with a negative dielectric permittivity. Applications in the fields of frequency selective surfaces and polarizers, as well as in microwave antennas and filter design, can be envisaged. The tunability of all these devices by an applied dc voltage is also achievable if these particles are etched on the appropriate substrate. DOI: 10.1103/PhysRevLett.93.197401 PACS numbers: 78.20.Ci, 41.20.Jb, 42.25.Fx, 84.40.-x Artificial metamaterials and metasurfaces with special electromagnetic properties have been a subject of growing interest in recent years [1,2]. Most proposed metamaterials make use of split ring resonators (SRRs) [3], or similar geometries, to achieve a negative effective permeability in a certain frequency range. The negative permittivity has been commonly obtained from an array of metallic wires or plates [2,4]. No particles acting as point electric dipoles with negative polarizability have been proposed to the date. In addition to these bulk metamaterial designs, one-and two-dimensional planar microwave circuits which show a left-handed behavior have been recently proposed [5][6][7], some of them making use of the SRR concept [7]. More recently, the application of these concepts to the design of artificial surfaces with special electromagnetic properties has been considered [8].In this Letter we present a new approach for the design of planar metamaterials and metasurfaces, which is based on the Babinet principle. The key element of this new approach is the complementary split ring resonator (CSRR), the complementary screen of the SRR (see Fig. 1). As a first step in our analysis the behavior of a perfectly conducting and infinitely thin SRR in an external electromagnetic field E 0 ; B 0 [see Fig. 2(a)] is considered. The scattered field E 0 ; B 0 is approximately given by the field produced by a resonant magnetic dipole [3]where ! 0 is the frequency of resonance of the SRR and 0 is a geometrical factor. This approximation neglects higher order multipolar fields [2,3]. It also neglects cross-polarization effects [9,10] (these effects are considered later in this Letter). Let us now consider the behavior of the CSRR when it is illuminated from z < 0 by an external electromagnetic field E 0 c ; B 0 c [see Fig. 2(b)].According to the electromagnetic theory of diffraction [11], the field in the shadowed region (z > 0) is the field scattered by the CSRR, E 0 c ; B 0 c . For z < 0, the total field is given by [11]where E 0;r c ; B 0;r c is the field that would be reflected by the metallic screen without the CSRRs etched on it. The scattered fields, E 0 c ; B 0 c and E 0 ; B 0 , must fulfill some symmetries that arise from the fact that they are produced by currents which are confined in the z 0 plane: the compone...

In this article, a novel compact planar diplexer based on the modified SR was proposed. The method of adjusting the stopband filter characteristic has also been demonstrated. The proposed SR structure provides good selectivity and high isolation between very narrow-spaced TX and RX operating channels. The isolation is greater than 30 dB. The insertion losses in the working channel are less than 1.25 dB in the RX band and less than 1.0 dB in the TX band. The return losses on the input ports are below 220 dB. The proposed diplexer has been fabricated using the standard PCB process on RO4003 laminates. Due to the very compact size of the SR embedded in transmission line the proposed diplexer, it is a good solution for applications where compact size, sharp selectivity, and high isolation are required. ABSTRACT: A new compact, low insertion loss, and wide stopband balanced bandpass filter (BPF) with two common-mode (CM) transmission zeros within the differential-mode (DM) passband is designed in this article. The DM filtering topology is formed by two quarterwavelength resonators and a short stub loaded source-load coupling structure which can generate new transmission zeros to improve the selectivity and suppress the harmonic to widen the stopband. The centerloaded step-impedance open stub can be applied to misalign two CM fundamental resonant frequencies, meanwhile adjust one CM transmission zero to the DM passband. To enhance the CM suppression within the DM passband, another CM transmission zero is created by the folded stub loaded in the 50-X input feedline which creates the first DM transmission zero located at 2f d 0 (f d 0 is the center frequency of DM passband) and has little effect on the DM in-band and lower-stopband performance. Finally, a high CM suppression balanced BPF prototype for WLAN application is designed and fabricated. The simulated and measured results show a good agreement.

A metallic planar particle, that will be called spiral resonator ͑SR͒, is introduced as a useful artificial atom for artificial magnetic media design and fabrication. A simple theoretical model which provides the most relevant properties and parameters of the SR is presented. The model is validated by both electromagnetic simulation and experiments. The applications of SR's include artificial negative magnetic permeability media ͑NMPM͒ and left-handed-media ͑LHM͒ design. The main advantages of SR's for such purpose are small electrical size at resonance, absence of magnetoelectric coupling ͑thus avoiding bianisotropic effects in the continuous medium made of these particles͒, and easy fabrication. Experimental confirmation of NMPM and LHM behavior using SR's is also reported.

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In this paper, the behavior at resonance of split ring resonators ͑SRRs͒ and other related topologies, such as the nonbianisotropic SRR and the broadside-coupled SRR, are studied. It is shown that these structures exhibit a fundamental resonant mode ͑the quasistatic resonance͒ and other higher-order modes which are related to dynamic processes. The excitation of these modes by means of a properly polarized time varying magnetic and/or electric fields is discussed on the basis of resonator symmetries. To verify the electromagnetic properties of these resonators, simulations based on resonance excitation by nonuniform and uniform external fields have been performed. Inspection of the currents at resonances, inferred from particle symmetries and full-wave electromagnetic simulations, allows us to predict the first-order dipolar moments induced at the different resonators and to develop a classification of the resonances based on this concept. The experimental data, obtained in SRR-loaded waveguides, are in agreement with the theory and point out the rich phenomenology associated with these planar resonant structures.

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