A predistortion linearizer using a tunable resonator

In this letter, a novel predistortion topology using a tunable resonator is presented. The core of the circuit is a series tunable resonator employing a reverse biased varactor diode. The junction capacitance of the varactor diode increases with RF input power, effectively shifting the resonant frequency of the circuit. This results in the amplitude and phase deviations at the frequency of operation. A 1.8-GHz power amplifier (PA), with a gain of 9 dB and 21-dBm output power, is linearized based on this technique. A maximum of 11 dB improvement in adjacent channel power ratio and an increase in 1.8 dB for the compression point is measured for the linearized PA.     

Contribution of dielectric and metallic losses in RF/microwave tunable varactors using (Ba,Sr)TiO3 thin films

Abstract

Recently, there has been significant interest in use of (Ba,Sr)TiO₃ (BST) thin films for tunable high frequency (RF and microwave) components. In a previous work we have shown that BST thin films grown by metalorganic chemical vapor deposition (MOCVD) exhibit films very low losses (as low as 0.003–0.004) and tunabilities over 50% at low operation voltages.

In order to integrate BST thin films in tunable devices, the objectives of this work are : (i) study the effect of bottom and top electrode on the performance of thin film based capacitors, (ii) correlate low frequency (10 kHz) and high frequency (45 MHz - 1 GHz) measurements, (iii) separate the contribution of dielectric losses and metallic losses at both low and high frequency and finally (iv) show the potential usefulness of series capacitors structures.     

Tunable barium strontium titanate thin film capacitors for RF andmicrowave applications

The measurement results for thin film barium strontium titanate (BST) based voltage tunable capacitors intended for RF applications are reported. At 9 V DC, BST capacitors fabricated using MOCVD (metalorganic chemical vapor deposition) method achieved 71% (3.4:1) tunability. The measured device quality factor (Q) for BST varactors is comparable with the device Q for commercially available varactor diodes of similar capacitance. The typical dielectric loss tangent was in the range 0.003-0.009 at VHF. Large signal measurement and modeling results for BST thin film capacitors are also presented     

The novel pyridine based symmetrical Schiff base ligand and its transition metal complexes: synthesis,spectral definitions and application in dye sensitized solar cells (DSSCs)

The pyridine based azo-linked symmetrical Schiff base ligand, (E)-2,2′-((1E,1′E)-(pyridine-2,6-diylbis(azanylylidene))bis(methanylylidene))bis(4-((E)-phenyldiazenyl)phenol) (H₂L), and its Co(II), Ni(II) and Pd(II) transition metal complexes were prepared, and defined by using elemental analysis, Fourier transform infrared, UV–visible, mass, nuclear magnetic resonance spectra, molar conductance, magnetic susceptibility and thermal analysis techniques. The conductivity results pointed out the non-electrolytic nature of all metal complexes. Elemental composition, ultraviolet spectra and magnetic susceptibility data showed that the synthesized complexes are in the binuclear structure and square plane geometry. When compared to the characteristic infrared bands for the functional groups of the ligand structure with complex molecules are reached, the ligand binds to the metal atom via phenolic OH and azomethine-nitrogen. Furthermore, the dye-sensitized solar cells (DSSCs) based on H₂L and its metal complexes were fabricated, and photovoltaic properties of these devices were also investigated. The power conversion efficiency of fabricated devices based on ligand H₂L can be improved with the incorporation of the transition metal complex.     

Flexibility and FMS: an empirical analysis

It is shown how the concerns of the managers of firms with flexible manufacturing system projects (FMS) differ from those of manufacturing firms without FMS projects. An economic model is developed from which two hypotheses are obtained. The first hypothesis is that firms were investing in FMS to deal with the variance in their inputs. The second proposition is that firms wished to use FMS to deal with the variance in their outputs. Through an analysis of manufacturing survey data it was found that firms planning to implement FMS were statistically more concerned about vendor quality and vendor lead times than non-FMS implementors. The FMS implementors also thought of their outputs as being too variable. Thus, it appears that the two hypotheses are empirically validated. However, it is also found that FMS implementors are planning on narrowing or standardizing their product lines. The inference drawn from these observations is that manufacturers in North America and Europe are using FMS for its ability to adapt to the variations in the system's inputs and not for product design changes