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Xia X.,Institute of Applied Electronics
Open Automation and Control Systems Journal | Year: 2015

Aiming at QPSK modulation digital system with variable rate, a novel implementation method based on field programmable gate array (FPGA) is proposed, which can support 4.88Kbps to 2Mbps and even higher continuous bit rate. The design adopts mixed multiplier, numerically controlled oscillator (NCO) and integral comb filter (CIC), and describes the structure of carrier recovery circuit and signal recovery circuit, which can be ported to any FPGA device. The proposed design has its hardware test in the Xilinx Virtex-5 FPGA platform. The hardware test results show that the proposed demodulator only takes up 15% available logical unit of Xilinx Virtex-5 FPGA device, revealing superior ability in efficiency. © Xiquan Xia. Source

Zhu H.,University of Sichuan | Feng G.,University of Sichuan | Yin M.,University of Sichuan | Gao X.,University of Sichuan | And 5 more authors.
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2011

The output characteristics of misaligned resonator for large-aperture thin disk laser have been studied experimentally and theoretically. A plane output coupler S 1, a concave mirror S 2 and an aperture stop are arranged to define the V-shape resonator. The misalignment sensitivities of the output power are given by means of matrix optics and the misalignment diffraction integral equation. The misalignment effects of the resonator having a variable aperture stop diameter on output power and beam quality have been measured by tilt -angle measurement technique at 200 Hz pump frequency, as well as the output power relationship with the misalignments of mirror S 1 and mirror S 2 at 300 Hz pump frequency. The experimental results show that the output power is a quadratic function of the tilt angle, the misalignment tolerance is directly proportional to mirror diameter and the beam quality factor decreases as the tilt angle increases. Source

Koval V.,Kharkiv Polytechnic Institute | Yasievich Y.,Kharkiv Polytechnic Institute | Dusheyko M.,Kharkiv Polytechnic Institute | Ivashchuk A.,Kharkiv Polytechnic Institute | And 2 more authors.
Nanopages | Year: 2013

Silicon nanocomposites (nc-Si) with rare earth metals (REM) were synthesized by electron-beam evaporation. The structure of nanocomposites was studied by atomic-force microscopy. The size of nanocrystallites was about 10-40 nm. Also chemical composition of obtained material was examined. The distribution of rare earth elements (REE) was uniform in film thickness, but it was characterized by a presence of maximum peak at the interface film-substrate. In the work the electrical and optical properties of nanocomposites Si:REE were investigated. Silicon nanocomposites with Eu or Y were characterized by high sensitivity to visible radiation. The ratio of dark to light resistance was achieved to 2 orders of magnitude, making this material very promising to use in thin-film photosensors. After deposition of nanocomposites Si:REE on silicon substrate, the heterojunction was formed at the interface film-substrate, for which the sensitivity to visible radiation was observed too (1-2 mA/lmV). Also, the presence of photovoltaic effect in such structures was shown, so they can be the basis of cheap thin-film solar cells, using the relevant design solutions. Source

Zhao Z.,Zhejiang University | Dong Y.,Zhejiang University | Pan S.,Zhejiang University | Liu C.,Zhejiang University | And 4 more authors.
Optics Express | Year: 2012

A large aperture fused silica tapered fiber phase conjugate mirror is presented with a maximum 70% stimulated Brillouin scattering (SBS) reflectivity, which is obtained with 1 kHz repetition rate, 15 ns pulse width and 38 mJ input pulse energy. To the best of our knowledge, this is the highest SBS reflectivity ever reported by using optical fiber as a phase conjugate mirror for such high pulse repetition rate (1 kHz) and several tens of millijoule (mJ) input pulse energy. The influences of fiber end surface quality and pump pulse widths on SBS reflectivity are investigated experimentally. The results show that finer fiber end surface quality and longer input pulse widths are preferred for obtaining higher SBS reflectivity with higher input pulse energy. Double passing amplification experiments are also performed. 52 mJ pulse energy is achieved at 1 kHz repetition rate, with a reflected SBS pulse width of 1.5 ns and a M2 factor of 2.3. The corresponding peak power reaches 34.6 MW. Obvious beam quality improvement is observed. © 2012 Optical Society of America. Source

Yu C.,Institute of Applied Electronics | Chen X.,Institute of Applied Electronics | Xue C.,Institute of Applied Electronics | Meng F.,Institute of Applied Electronics
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2010

The near field properties of circular aperture antennas with Gaussian amplitude distribution are analyzed by the aperture field integration method in this paper. The axial near field and gain expressions of the unfocused and focused circular aperture antennas are deduced. The near-axis field distribution of circular aperture antennas is obtained by numeric integration method. The analysis shows that for the circular aperture antennas with Gaussian amplitude distribution, axial near field varies in an oscillatory manner and the near-field gain is related to both aperture distribution and the distance from the antenna. The near-field gain in the focus can achieve the gain in far field and the field intensity near the focus can be enhanced greatly through aperture focusing. Source

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