High‐performance wide stop band low‐pass filter using a vertically coupled DGS‐DMS‐resonators and interdigital capacitor

directivity at those frequencies are 0.80, 0.83, and 0.81; 1.27, 1.45, and 1.60; and 1.60, 1.77, and 1.99, respectively. Clearly, the maximum directivity is increasing for a fixed overall size as the resonance wavelength decreases. In summary, the choice of a low-loss substrate and the proper placements of the CLL elements relative to each other and to the driven monopole are the key points that had to be considered for all of the proposed antennas to achieve their noted high radiation efficiencies and prescribed maximum directivity directions while maintaining their electrically small and simple geometries. 4. CONCLUSION We have reported metamaterial-inspired electrically small single-, dual-, and triple-band antennas at the GSM (1.93–1.99 GHz), ISM (2.43–2.4835 GHz), and WIMAX (3.3–3.6 GHz) frequencies. Performance characteristics of these antennas were obtained numerically using HFSS, a commercial full-wave electromagnetic solver. These antennas have planar configurations that include CLLs as their NFRP radiators and a coaxially fed printed dipole as the driven element. In the proposed topology, the number of operating frequencies is determined by the number of CLLs. The proposed antenna structures all operate as magnetic dipoles (directivities � 1.622.0 dB). In addition to having electrically small and geometrically simple topologies, they are nearly completely matched to their 50-X source and have high (� 80%) radiation efficiencies at all of their prescribed operating frequencies. ACKNOWLEDGMENTS