NOPR Community:

Novel design of compact wideband planar metal antenna

2016-07-20T04:40:18Z

Title: Novel design of compact wideband planar metal antenna Authors: Mondal, S; Sarkar, P P Abstract: In the present paper, a novel design of compact wideband planar metal antenna has been presented for wireless communication. The proposed antenna is fed by a Coaxial to CPW transition to match with 50 Ω input impedance line. A shorting strip is used to reduce the size of the antenna. The modified CPW feed line is in the same plane with the radiating element to achieve complete planar antenna and bi-directional radiation pattern. The impedance bandwidth for |S11| < 10 dB of the antenna ranges from 1.05 to 25 GHz. So this antenna can work in various frequency bands like WLAN and UWB. A circular hole at the centre of radiating element is introduced to reduce the volume, weight and cost of the antenna. Various characteristics of the proposed antenna have been computed using finite integration technique based commercial software CST studio. The simulated and measured reflection coefficients are in good agreement. Page(s): 851-856

Systematic synthesis of OTA-based Wien oscillators

2016-07-20T04:36:39Z

Title: Systematic synthesis of OTA-based Wien oscillators Authors: Li, Yong-an Abstract: Nodal admittance matrix (NAM) expansion method for systematic synthesis of seven-OTA Wien oscillators is given. The paper presents 32 Wien oscillators using OTAs by means of NAM expansion method. Each oscillator employs seven OTAs and two grounded capacitors, it is easy to be integrated and the oscillation condition and frequency can be tuned electronically, linearly and independently through tuning bias currents of OTAs. The circuit analysis and computer simulation results are in agreement with theory and then the realizability of the derived circuits is verified. Page(s): 846-850

Structure, surface morphology and optical properties of BaTiO₃ powders prepared by wet chemical method

2016-07-20T04:32:47Z

Title: Structure, surface morphology and optical properties of BaTiO₃ powders prepared by wet chemical method Authors: Sengodan, R; Shekar, B Chandar; Sathish, S Abstract: Barium titanate powders were synthesized by the wet chemical method using the starting materials barium chloride (BaCl₂), titanium dioxide (TiO₂) and oxalic acid with different calcinations temperature. The XRD pattern of BaTiO₃calcined at 500 ˚C showed cubic phase whereas BaTiO₃samples calcined at 700 ˚C and above showed tetragonal phase. The crystallite size, strain and dislocation density were calculated from the XRD spectrum. It was found that crystallite size increases with increase of calcination temperature. EDS spectrum was used to identify the composition of the material. Absorption co-efficient (α), extinction co-efficient (K) and optical band gap were estimated from the optical reflectance spectrum. The band gap of the powder was found to be decreasing with the increase of calcination temperature. Nanoparticles of both spherical and rod like in shape were clearly observed in the SEM. Page(s): 839-845

Effect of MoO₃ in the cathode buffer layer on the behaviour of layered organic solar cells

2016-07-20T05:27:17Z

Title: Effect of MoO₃ in the cathode buffer layer on the behaviour of layered organic solar cells Authors: Ouari, K El Assad Zemallach; Jouad, Z El; Benchouk, K; Kouskoussa, B; Cattin, L; Makha, M; Khelil, A; Morsli, M; Addou, M; Bernède, J C Abstract: The behaviour of small-molecule organic solar cells based on copper-phthalocyanine/fullerene with different cathode buffer layer is investigated as a function of air exposure duration. The effect of MoO₃ on the properties of photovoltaic solar cells (OPVCs) when it is introduced in the cathode buffer layer (CBL), has been studied. Photovoltaic performances were measured as a function of time of air exposure. During the first days of air exposure, the efficiency of the OPVCs with MoO₃ in their CBL increases significantly, while it decreases immediately after air exposure in the case of reference OPVCs, i.e. without MoO₃ in the CBL. Nevertheless, the lifetime of the OPVCs with MoO₃ in their CBL is around 60 days, while it is only 10 days in the case of reference OPVCs. The initial increase of the OPVC with MoO₃ in their CBL is attributed to the slow decrease of the work function of MoO₃ due to progressive contamination. Then, the progressive degradation of the OPVCs efficiency is due to water vapour and oxygen contamination of the organic layers. The use of double CBL, Alq₃/MoO₃, allows to interrupt the growth of pinholes, defects and increases the path of permeating gas. Also it can prevent the contamination of the organic layer by Al. All this results in significant increase of the lifetime of the OPVCs. Page(s): 829-838

NOPR Community:

Novel design of compact wideband planar metal antenna

Systematic synthesis of OTA-based Wien oscillators

Structure, surface morphology and optical properties of BaTiO3 powders prepared by wet chemical method

Effect of MoO3 in the cathode buffer layer on the behaviour of layered organic solar cells

Structure, surface morphology and optical properties of BaTiO₃ powders prepared by wet chemical method

Effect of MoO₃ in the cathode buffer layer on the behaviour of layered organic solar cells