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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.

In this letter, a planar left-handed propagating medium consisting of a coplanar waveguide ͑CPW͒ inductively coupled to split ring resonators ͑SRR͒ and periodically loaded with narrow metallic wires is proposed. The wires make the structure behave as a microwave plasma with a negative effective permittivity which covers a broad frequency range. The negative permeability required to achieve left-handed wave propagation is provided by the rings in the vicinity of their resonant frequency. The result is a structure which allows negative wave propagation in a narrow frequency band. The transmission coefficient measured in a fabricated prototype device exhibits very low insertion losses in the pass band and high-frequency selectivity. Since rings are much smaller than signal wavelength at resonance and can be easily tuned, SRR-CPW-based structures are of interest for the design of very compact microwave circuits based on left handedness. © 2003 American Institute of Physics. ͓DOI: 10.1063/1.1631392͔The development of artificial materials ͑metamaterials͒ with simultaneously negative permeability and permittivity, or left-handed materials ͑LHMs͒, has been a subject of growing interest in recent years. Apart from its exotic electrodynamic properties ͑such as the reversal of Snell's law, Doppler effect, and Cherenkov radiation͒, pointed out by Veselago more than 30 years ago, 1 key to this interest is the potential applicability of these metamaterials to the fabrication of radio frequency ͑rf͒ and microwave components based on left handedness. Due to negative values of effective permittivity and permeability, LHMs are negative refractive index media with antiparallel phase and group velocities. 2,3 Namely, the wavevector k forms a left-handed triplet with the vectors E and H ͑the electric and magnetic field intensity͒ and wave fronts for propagating electromagnetic ͑EM͒ waves travel toward the source, i.e., opposite to the direction of energy flow.Due to the absence of transparent LHMs in nature, a LHM medium has to be artificially fabricated. This can be achieved by microstructuring a material in a length scale much shorter than the wavelength of EM radiation, so that a continuous medium with effective electromagnetic properties ͑permittivity and permeability͒ is obtained. An artificial LHM operating in the microwave region was reported by Smith et al. 4 The structure was fabricated by combining a periodic array of metal posts with an array of nonmagnetic split ring resonators ͑SRRs͒. Originally proposed by Pendry, 5 SRRs provide a negative effective permeability in the vicinity of the resonant frequency, while metallic wires behave like a two-dimensional ͑2D͒ plasma with negative permittivity up to the plasma frequency. Left-handed wave propagation has been also demonstrated in a one-dimensional ͑1D͒ configuration consisting of a hollow metallic waveguide periodic loaded with SRRs. 6 For EM propagation in the axial direction, the metallic waveguide emulates a lossless plasma whose dielectric permittivity is negative be...

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In this paper, we present a new parallel-coupled-line microstrip bandpass filter with suppressed spurious passband. Using a continuous perturbation of the width of the coupled lines following a sinusoidal law, the wave impedance is modulated so that the harmonic passband of the filter is rejected while the desired passband response is maintained virtually unaltered. This strip-width perturbation does not require the filter parameters to be recalculated and, this way, the classical design methodology for coupled-line microstrip filters can still be used. At the same time, the fabrication of the resulting filter layout does not involve more difficulties than those for typical coupled-line microstrip filters. To test this novel technique, order-3 Butterworth bandpass filters have been designed at 2.5 GHz with a 10% fractional bandwidth and different values of the perturbation amplitude. It is shown that for a 47.5% sinusoidal variation of the nominal strip width, a harmonic rejection of more than 40 dB is achieved in measurement while the passband at 2.5 GHz is almost unaltered.

We explore, both experimentally and theoretically, the existence in the millimeter-wave range of the phenomenon of extraordinary light transmission through arrays of subwavelength holes. We have measured the transmission spectra of several samples made on aluminum wafers by use of an AB Millimetre quasi-optical vector network analyzer in the wavelength range 4.2-6.5 mm. Clear signals of the existence of resonant light transmission at wavelengths close to the period of the array appear in the spectra.