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Electronic transport properties in an Al cluster are investigated theoretically in this paper. We propose a possible illustration of Coulomb blockade based on variable electrostatic potential (ESP). Density functional theory (DFT) was used to achieve the global minimum structure and wave function for analyzing the ESP and density of states (DOS) of Al68 in different charged states. Al68 is able to contain multiple electrons. According to the calculation of systematic energy and surface ESP, respectively, the surface of Al68 presents a 0–6.33 eV ESP barrier after electron injection, which is 0 eV at first. The probability density of flow of electrons was calculated under one-dimensional model with double barriers. Expected results were obtained, containing a nonlinear relationship between J and V and flow density steps. Moreover, an assumption is proposed associated with nonlinear conductance phenomenon of zero-dimensional nanomaterials. Significantly, Al films with different thicknesses were prepared by the low vacuum physical vapor deposition (LVPVD) method, exhibiting novel fluorescent behaviors. In addition, the I–V curve of a 25-nm Al film exhibited two steps at 7 and 27 V, respectively, which meant that the step effect was caused by Coulomb blockade, in accordance with the theoretical calculation.

A novel defected ground structure (DGS) with two semicircular defected areas is investigated for low pass filter (LPF) applications. An equivalent lumped L-C circuit model is presented and its corresponding L-C parameters are also extracted by using parametric relationships. With this structure, the effect of the defected parameters on performance is detailed. Based on the equivalent circuit model, a 3-pole LPF, using 2 DGS units, is optimally designed and implemented. The results from experiments confirm that the designed LPF can provide a very wide stop band, which is approximately 3.7 times of the cutoff frequency. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1760–1763, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21750

In this article, several square open-loop resonators with transmission lines are proposed to design the optimized bandpass filters. A compact microstrip filter using an open-loop resonator was designed, fabricated and measured. At the center frequency f0 = 1.80 GHz, a 3-dB bandwidth of 5% can be varied from 1.76 to 1.85 GHz. The filter shows a maximum insertion loss in passband of 0.1 dB. A transmission zero is realized at about 3.1 GHz, and the attenuation at this frequency exceeds 70 dB. When compared with the conventional filters using coupled square open-loop resonators, the proposed filter has a size reduction of 30%. Good agreement between measurements and simulations are obtained. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2755–2757, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22837