A novel dual-band left-handed metamaterial (LHM) design method is proposed in this paper. Unlike other methods, where the designers focused their attentions on designing single LHM unit with multiple electric/magnetic resonances or combining multiple different LHM units together, the proposed method in this paper introduces an additional magnetic resonance to extract negative permeability, taking advantage of the areas between neighboring units. In this paper, we first designed a single-band single negative metamaterial ( < 0) and then connected neighboring units with metallic wires. This connection introduces a magnetic resonance that extracts another frequency band with negative permeability. With the help of arrayed metallic wires printed on the other side of the substrate, we successfully get a dual-band LHM. The proposed structures are analyzed with equivalent circuits and verified with simulations.

This paper presents a metamaterial-inspired triple-band antenna specified for WLAN and WiMAX applications with a compact size of 24mm × 18mm × 1mm (at 2.4 GHz). It consists of a dual-band left-handed metamaterial (LHM) unit surrounded by a G-style monopole antenna. The LHM is first designed and analyzed with equivalent circuits and simulations. A loop antenna based on the LHM unit is designed and simulated to investigate the radiating performance of the LHM unit structure. We also ran simulations for the G-style monopole. Later, the LHM unit is employed as a near-field resonant parasitic (NFRP) element that surrounded by the G-style monopole. A prototype of this antenna is fabricated. Simulations and measurements were carried out and the results match well, identifying good omni-directional radiating performance. Radiation comparisons with the loop antenna and the G-style monopole indicate that due to NFRP, the G-style monopole’s pass bands are shifted to lower frequencies to satisfy 2.45 GHz and 5.5 GHz bands requirements, meanwhile the LHM unit structure operates a third pass band of 3.5 GHz. The compact size and good radiation properties of the antenna render it suitable for WLAN/WiMAX applications.

Diagonal loading technology is widely used in array antenna beamforming because of its simple method, low computational complexity and the ability to improve the robustness of beamformer. On this basis, this paper proposes a robust adaptive beamforming method based on automatic variable loading technology. The automatic variable loading matrix (AVLM) of the method is composed of two parts. The non-uniform loading matrix dominants when the input signal-to-noise ratio (SNR) is small, effectively control the influence of noise disturbance without affecting the ability of array antenna to suppress interference. The variable diagonal loading matrix dominants when the input SNR is high to improve the output performance of array antenna. Simulated results show that compared to other methods, the proposed method has better output performance for both low and high input SNR cases.

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Surface impedance boundary condition (SIBC) is a potential way to improve the efficiency of the finite‐difference time‐domain (FDTD) method. However, it is still seldom used in FDTD simulations, especially for complicated problems. In this study, the authors propose a novel SIBC, the perfect electric conductor (PEC) backed SIBC (PEC–SIBC). It is a combination of SIBC and PEC. This character makes it possible to integrate PEC–SIBC with the conventional FDTD method. The authors derive the updating equations of PEC–SIBC for a one‐dimensional (1D), 2D and 3D problems. Then, the authors verify the validity of PEC–SIBC with a 1D example and analyse the complexity with a 2D example. The comparison for a 1D configuration indicates that PEC–SIBC is a little more accurate than the traditional SIBC. For a 2D example, the SIBC is used to replace a lossy dielectric medium located in the middle of the problem domain. The complexity analysis indicates that PEC–SIBC is much easier and more practical to use than the traditional SIBC.