Design of 5 th-order analog predistorter

This paper presents the design of a 5th-order analog predistorter to suppress the 3rd-and 5th-order intermodulation distortion products (EVTDP3 and EVTDP5) at the output of a base-station power amplifiers (PAs). The predistorter consists of two mixers: one mixer generating the 3rd-order intermodulation (IM3) products and another mixer of same configuration generating the 5th-order intermodulation (IM5) products using the IM3 products generated by the other mixer, thus simplifying the design and hardware implementation. The predistorter is implemented and tested using two-tone and the CDMA (IS-95) signals at 2.2GHz in a practical 10W-PA. The two-tone test results show that the proposed predistorter can suppress the IMDP3 and IMDP5 by 17dB and lldB, respectively. For the CDMA (IS-95) test, results show that the predistorter can improve the adjacent channel power ratio (ACPR) by 10 dB at ± 887 kHz from the center frequency. © 2010 IEEE.published_or_final_versionThe 2010 IEEE Region 10 International Conference (TENCON 2010), Fukuoka, Japan, 21-24 November 2010. In TENCON (IEEE Region 10 Conference) Proceedings, 2010, p. 876-87

A 5 th-order analog predistorter for NADC system

This paper presents the design of a 5th-order analog predistorter using the inband intermodulation (IM) signals for predistortion of base-station high power amplifiers (HPAs) for the North American Digital Cellular (NADC) system. The predistorter employs two mixers with same configuration to generate 3rd-order intermodulation (IM3) products and 5th-order intermodulation (IM5) products, to suppress the 3 rd-and 5th-order intermodulation distortion products (IMDP3 and IMDP5) at the HPA output. The predistorter is implemented and tested using the pi/4-DQPSK signal of the NADC system at 2.2GHz in a practical 100W-HPA. The results show that, at the HPA output powers of 65.6, 56.2, 50 and 41.3 W, the predistorter can suppress the adjacent channel power ratio (ACPR) of the pi/4-DQPSK signal at ± 20 kHz from the center frequency by 15.16, 15.83, 16.17 and 15.17 dB, respectively. © 2010 IEEE.published_or_final_versionThe 12th IEEE International Conference on Communication Systems (ICCS 2010), Singapore, 17-19 November 2010. In Proceedings of 12th ICCS, 2010, p. 19-2

EGFR Tyrosine kinase regulates small conductance Ca2+-activated K+ (hSKCa1) channels expressed in HEK 293 cells

SKCa (small-conductance Ca(2+)-activated K(+)) channels are widely distributed in different tissues, including the brain, pancreatic islets and myocardium and play an important role in controlling electrical activity and cellular functions. However, intracellular signal modulation of SKCa channels is not fully understood. The present study was designed to investigate the potential regulation of hSKCa1 (human SKCa1) channels by PTKs (protein tyrosine kinases) in HEK (human embryonic kidney)-293 cells expressing the hSKCa1 (KCNN1) gene using approaches of whole-cell patch voltage-clamp, immunoprecipitation, Western blotting and mutagenesis. We found that the hSKCa1 current was inhibited by the broad-spectrum PTK inhibitor genistein, the selective EGFR (epidermal growth factor receptor) kinase inhibitors T25 (tyrphostin 25) and AG556 (tyrphostin AG 556), but not by the Src-family kinases inhibitor PP2. The inhibitory effect of these PTK inhibitors was significantly antagonized by the PTP (protein tyrosine phosphatase) inhibitor orthovanadate. The tyrosine phosphorylation level of hSKCa1 channels was reduced by genistein, T25 or AG556. The reduced tyrosine phosphorylation was countered by orthovanadate. Interestingly, the Y109F mutant hSKCa1 channel lost the inhibitory response to T25 or AG556, and showed a dramatic reduction in tyrosine phosphorylation levels and a reduced current density. These results demonstrate the novel information that hSKCa1 channels are inhibited by genistein, T25 and AG556 via EGFR tyrosine kinase inhibition, which is related to the phosphorylation of Tyr(109) in the N-terminus. This effect may affect electrical activity and cellular functions in brain, pancreatic islets and myocardium.postprin

A MIMO antenna for mobile applications

A multiband Multiple-Input Multiple-Output (MIMO) antenna for mobile phones applications in the next generation is proposed. The proposed MIMO antenna consists of two identical elements, each having three branches to generate two frequency bands, a wide higher and narrow lower frequency bands. Simulation results show that these two frequency bands can cover the lower band for Long-Term Evolution (LTE), the DCS1800, PCS1900 and UMTS-2100 bands, the Wibro Band, the 2.4-GHz band for the WLAN system and also the upper band for the WiMAX. By cutting a slit on the printed circuit board (PCB) serving the ground plane, a great enhancement of isolation between the two antenna elements can be achieved for the two frequency bands. © 2013 IEEE.published_or_final_versio

Compensation ratio-dependent concentration of a V InH 4 complex in n-type liquid encapsulated Czochralski InP

The concentration of hydrogen-indium vacancy complex V InH 4 in liquid encapsulated Czochralski undoped and Fe-doped n-type InP has been studied by low-temperature infrared absorption spectroscopy. The V InH 4 complex is found to be a dominant intrinsic shallow donor defect with concentrations up to ∼10 16 cm -3 in as-grown liquid encapsulated Czochralski InP. The concentration of the V InH 4 complex is found to increase with the compensation ratio in good agreement with the proposed defect formation model of Walukiewicz [W. Walukiewicz, Phys. Rev. B 37, 4760 (1998); Appl. Phys. Lett. 54, 2094 (1989)], which predicts a Fermi-level-dependent concentration of amphoteric defects. © 1998 American Institute of Physics.published_or_final_versio

Microwave assisted heterogeneous catalysis: effects of varying oxygen concentrations on the oxidative coupling of methane

The oxidative coupling of methane was investigated over alumina supported La2O3/CeO2 catalysts under microwave dielectric heating conditions at different oxygen concentrations. It was observed that, at a given temperature using microwave heating, selectivities for both ethane and ethylene were notably higher when oxygen was absent than that in oxygen/methane mixtures. The differences were attributed to the localised heating of microwave radiation resulting in temperature inhomogeneity in the catalyst bed. A simplified model was used to estimate the temperature inhomogeneity; the temperature at the centre of the catalyst bed was 85 °C greater than that at the periphery when the catalyst was heated by microwaves in a gas mixture with an oxygen concentration of 12.5% (v/v), and the temperature difference was estimated to be 168 °C in the absence of oxygen

Adaptive frequency sweep analysis for electromagnetic problems using the Thiele interpolating continued fractions

A direct rational approximation method based on Thiele interpolating continued fractions theory is proposed for fast frequency sweep analysis of electromagnetic problems. And an adaptive algorithm is also formed. Compared with the conventional rational approximation method, the proposed method can get a rational approximation directly without a great number of matrix inverse computations and doesn't need to allocate much memory for high derivatives of the dense impedance matrix. Meanwhile, the computation of surface currents by continued fractions can be sped up as compared with the traditional rational approximation. Numerical simulations for broad band scattering analysis of different shaped objects are discussed to shown the effectiveness of the present method. © 2010 IEEE.published_or_final_versionThe 2nd International Conference on Education Technology and Computer (ICETC 2010), Shanghai, China, 22-24 June 2010. In Proceedings of 2nd ICETC, 2010, v. 5, p. 126-12

Thermally induced conduction type conversion in n-type InP

n-type semiconducting InP is changed into p-type semiconducting by short time annealing at 700 °C. Further annealing for a longer time leads to a second conduction-type conversion changing the material back to n type again but with a much higher resistivity. These conduction conversions indicate the formation of both acceptor and donor defects and the progressive variation of their relative concentrations during annealing. © 1999 American Institute of Physics.published_or_final_versio

Transferrin-bound Yb2 uptake by U-87 MG cells and effect of Yb on proliferation of the cells

2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Metal-organic framework composites with luminescent gold(III) complexes. Strongly emissive and long-lived excited states in open air and photo-catalysis

The encapsulation of luminescent gold(III) complexes by metal–organic frameworks (MOFs) lays the groundwork for new phosphorescent materials with activities that are not readily achieved by the host MOF materials or gold(III) complexes alone. In this work, strong phosphorescence with lifetimes of up to ∼50 μs in open air at room temperature has been achieved by incorporation of cationic cyclometalated gold(III) complexes into MOFs with anionic frameworks to form AuIII@MOFs. The AuIII@MOFs display solid state two-photon-induced phosphorescence. Photo-reduction of methyl viologen to the reduced radical was achieved inside AuIII@MOFs and in the presence of Et3N upon excitation at λ > 370 nm under ambient conditions. These AuIII@MOFs comprise a class of reusable and size-selective heterogeneous photo-catalysts for the aerobic oxidation of secondary amines to imines as well as five other reactions, including oxidative C–H functionalization under aerobic conditions.published_or_final_versio