Articles de revues : « RF Pulse Compressor »

1

Shu, Guan, Feng-Li Zhao, Shi-Lun Pei et Ou-Zheng Xiao. « RF modulation studies on an S band pulse compressor ». Chinese Physics C 40, n^o 3 (mars 2016) : 037002. http://dx.doi.org/10.1088/1674-1137/40/3/037002.

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Li, Zongbin, Wencheng Fang, Qiang Gu et Zhentang Zhao. « RF design of a C-band compact spherical RF pulse compressor for SXFEL ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 863 (août 2017) : 7–14. http://dx.doi.org/10.1016/j.nima.2017.05.017.

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Karsli, Ozlem, Avni Aksoy, Caglar Kaya, Burak Koc, Mustafa Dogan, O. Faruk Elcim et Mehmet Bozdogan. « High power RF operations studies at TARLA facility ». Canadian Journal of Physics 97, n^o 11 (novembre 2019) : 1171–76. http://dx.doi.org/10.1139/cjp-2018-0778.

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Turkish Accelerator and Radiation Laboratory (TARLA) is a facility capable of accelerating an electron beam up to 40 MeV. Two beamlines were proposed to generate free-electron laser radiation and bremsstrahlung. The accelerator employs two normal conducting cavities, so-called buncher cavities: subharmonic buncher (SHB) and fundamental buncher (FB), and two cryomodules that house two TESLA cavities each. SHB operates in 260 MHz and FB in 1.3 GHz, and is powered by 1.5 kW and 500 W radio frequency (RF) amplifiers, respectively. Each TESLA cavity is driven by 18 kW saturated high-power solid-state amplifiers (SSA). In addition, a L band pulse compressor system is designed and implemented at the facility to actively promote high-power RF research. Currently, setup of a resonant ring test bench is approved to test the RF components under high power RF conditions. This paper describes the TARLA high power RF, RF controller, and network structures. High power tests and measurements of the RF components of the TARLA beamline are given. Outcomes from the operation of the L band pulse compressor are explained, and the resonant ring test stand is stated as a summary.

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Shu, Guan, Feng-Li Zhao et Xiang He. « RF study of a C-band barrel open cavity pulse compressor ». Chinese Physics C 39, n^o 5 (mai 2015) : 057005. http://dx.doi.org/10.1088/1674-1137/39/5/057005.

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Fernandes, P., R. Parodi, C. Salvo et B. Spataro. « The design of TE storage cavities for a rf pulse compressor system ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 288, n^o 2-3 (mars 1990) : 549–54. http://dx.doi.org/10.1016/0168-9002(90)90151-u.

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Golubičić, Zoran, Slobodan Simić et Aleksa J. Zejak. « Design and EPGA Implementation of Digital Pulse Compression for Band–Pass Radar Signals ». Journal of Electrical Engineering 64, n^o 3 (1 mai 2013) : 191–95. http://dx.doi.org/10.2478/jee-2013-0028.

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The paper presents fully digitized approach for band-pass discrete coded radar signals. The emphasis is to use one generalized reconfigurable compressor for several different types of signals and different types of receivers. It fits for direct radio frequency receiver (RF) as well as for intermediate frequency (IF) receiver. The system implementation on field programmable gate area (FPGA) let us eliminate special chips previously needed. From the experimental results it is known that this approach appears to work well for matched and mismatched pulse compression and it outstands when timebandwidth product (TB) is of order 1000. A precision of 14 bits has been considered in the input signal and 16 bits in the filter coefficients. It gives the dynamic range of 78 dB and the quantification error less than 0.012%.

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VAN DER GEER, S. B., O. J. LUITEN et M. J. DE LOOS. « DESIGN OF A 2 kA, 30 fs RF-PHOTOINJECTOR FOR WATERBAG COMPRESSION ». International Journal of Modern Physics A 22, n^o 22 (10 septembre 2007) : 4000–4005. http://dx.doi.org/10.1142/s0217751x07037573.

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Because uniformly filled ellipsoidal ‘waterbag’ bunches have linear self-fields in all dimensions, they do not suffer from space-charge induced brightness degradation. This in turn allows very efficient longitudinal compression of high-brightness bunches at sub or mildly relativistic energies, a parameter regime inaccessible up to now due to detrimental effects of non-linear space-charge forces. To demonstrate the feasibility of this approach, we investigate ballistic bunching of 1 MeV, 100 pC waterbag electron bunches, created in a half-cell rf-photogun, by means of a two-cell booster-compressor. Detailed GPT simulations of this table-top set-up are presented, including realistic fields, 3D space-charge effects, path-length differences and image charges at the cathode. It is shown that with a single 10MW S-band klystron and fields of 100 MV/m, 2kA peak current is attainable with a pulse duration of only 30 fs at a transverse normalized emittance of 1.5 μm.

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Zhang, Jingru, Cai Meng, Dazhang Li, Dou Wang, Guoxi Pei, Hua Shi, Jie Gao, Xiang He, Xiaoping Li et Yunlong Chi. « R&D of CEPC injector linac ». International Journal of Modern Physics A 36, n^o 22 (5 août 2021) : 2142013. http://dx.doi.org/10.1142/s0217751x21420136.

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The CEPC includes a main ring and an injector. The injector consists of a booster and a linac. In order to meet the requirements of the booster, the baseline design of the linac is a 10 GeV electron and positron linac. Two alternative linac designs have also been introduced in this paper. For the linac baseline design, one-bunch-per-pulse is adopted. A 1.1 GeV damping ring is used to reduce the transverse emittance of positron beam. The main RF system of the linac adopts normal conducting S-band structure. Some key technologies of linac are development. The S-band structure and pulse compressor have been researched and studied. In the damping ring, two cavities used to provide 2 MV voltage. The preliminary cavity design has finished.

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Krainara, Siriwan, Shuya Chatani, Heishun Zen, Toshiteru Kii et Hideaki Ohgaki. « Manipulation of Laser Distribution to Mitigate the Space-Charge Effect for Improving the Performance of a THz Coherent Undulator Radiation Source ». Particles 1, n^o 1 (7 novembre 2018) : 238–52. http://dx.doi.org/10.3390/particles1010018.

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A THz coherent undulator radiation (THz-CUR) source has been developed at the Institute of Advanced Energy, Kyoto University. A photocathode Radio-Frequency (RF) gun and a bunch compressor chicane are used for generating short-bunch electron beams. When the electron beam energy is low, the space-charge effect strongly degrades the beam quality, such as the bunch length and the energy spread at the high bunch charge condition at around 160 pC, and results in the reduction of the highest frequency and the maximum radiated power of the THz-CUR. To mitigate the space charge effect, we have investigated the dependence of the electron beam quality on the laser distribution in transverse and longitudinal directions by using a numerical simulation code, General Particle Tracer GPT. The manipulation of the laser distribution has potential for improving the performance of the THz-CUR source. The electron bunch was effectively compressed with the chicane magnet when the laser transverse distribution was the truncated Gaussian profile, illuminating a cathode. Moreover, the compressed electron bunch was shortened by enlarging the laser pulse width. Consequently, an enhancement of the radiated power of the THz-CUR has been indicated.

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Junphong, P., V. Ano, B. Lekprasert, D. Suwannakachorn, Thiraphat Vilaithong et H. Wiedemann. « Bunch Compression of a Non-Relativistic 280-keV-He⁺ Beam ». Solid State Phenomena 107 (octobre 2005) : 59–62. http://dx.doi.org/10.4028/www.scientific.net/ssp.107.59.

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At 150 kV-pulsed neutron generator at the Fast Neutron Researh Facility is being upgraded to produce a 280-kV-pulsed-He beam for Time-of-Flight Rutherford Backscattering Spectrometry (TOF RBS). Modification are being done by replacing the existing beamline elements by a 400-kV accelerating tube, 45o-double focusing dipole magnet and quadrupole lens. The beam transport system has to be redesigned based on the new elements. The important part of a good pulsed beam depends on the pulsing system. The two main parts are the chopper and buncher. Radiofrequency (RF) of 2 MHz is used for the chopper and 4 MHz for the buncher. For the buncher the RF amplitude of 13 kV is applied to two gaps, so that the ion pulse is compressed twice. An optimized geometry for the 280-keV pulsed helium ion beam is presented in this paper,. The PARMELA code has been used to optimize the space-charge effect, resulting in a excitated pulse width of less than 2 ns at a target. The calculated distance from a buncher to the target is 4.6 m. Effects of energy spread and phase angle between the chopper and buncher have been included in the optimization of the bunch lengh.

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GNINENKO, S. N. « DESIGN OF A HIGH-EFFICIENCY PULSED POSITRON BEAM FOR EXPERIMENTS WITH ORTHOPOSITRONIUM IN VACUUM ». International Journal of Modern Physics A 19, n^o 23 (20 septembre 2004) : 3939–49. http://dx.doi.org/10.1142/s0217751x04020191.

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A new design of a high-efficiency pulsed slow positron beam for experiments with orthopositronium in vacuum is described. The new method is based on a RF waveform pulse applied to a double gap buncher system for adjusting the time-of-flight of positrons. Simulations show that compression of positrons emitted from the moderator during 300 ns into a pulse of 2 ns width is achievable. Preliminary results on the design and requirements for the pulsing system components are presented.

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Yani, Kalfika, Fiky Y. Suratman et Koredianto Usman. « Design and Implementation Pulse Compression for S-Band Surveillance Radar ». Journal of Measurements, Electronics, Communications, and Systems 7, n^o 1 (30 décembre 2020) : 20. http://dx.doi.org/10.25124/jmecs.v7i1.2631.

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The radar air surveillance system consists of 4 main parts, there are antenna, RF front-end, radar signal processing, and radar data processing. Radar signal processing starts from the baseband to IF section. The radar waveform consists of two types of signal, there are continuous wave (CW) radar, and pulse compression radar [1]. Range resolution for a given radar can be significantly improved by using very short pulses. Pulse compression allows us to achieve the average transmitted power of a relatively long pulse, while obtaining the range resolution corresponding to a short pulse. Pulse compression have compression gain. With the same power, pulse compression radar can transmit signal further than CW radar. In the modern radar, waveform is implemented in digital platform. With digital platform, the radar waveform can optimize without develop the new hardware platform. Field Programmable Gate Array (FPGA) is the best platform to implemented radar signal processing, because FPGA have ability to work in high speed data rate and parallel processing. In this research, we design radar signal processing from baseband to IF using Xilinx ML-605 Virtex-6 platform which combined with FMC-150 high speed ADC/DAC.

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Cai, Xintian, Zhen Wang, Chaoyue Ji, Xuan Wang, Zhiyin Gan et Sheng Liu. « Control of the Longitudinal Compression and Transverse Focus of Ultrafast Electron Beam for Detecting the Transient Evolution of Materials ». Materials 15, n^o 2 (13 janvier 2022) : 571. http://dx.doi.org/10.3390/ma15020571.

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Ultrafast detection is an effective method to reveal the transient evolution mechanism of materials. Compared with ultra-fast X-ray diffraction (XRD), the ultra-fast electron beam is increasingly adopted because the larger scattering cross-section is less harmful to the sample. The keV single-shot ultra-fast electron imaging system has been widely used with its compact structure and easy integration. To achieve both the single pulse imaging and the ultra-high temporal resolution, magnetic lenses are typically used for transverse focus to increase signal strength, while radio frequency (RF) cavities are generally utilized for longitudinal compression to improve temporal resolution. However, the detection signal is relatively weak due to the Coulomb force between electrons. Moreover, the effect of RF compression on the transverse focus is usually ignored. We established a particle tracking model to simulate the electron pulse propagation based on the 1-D fluid equation and the 2-D mean-field equation. Under considering the relativity effect and Coulomb force, the impact of RF compression on the transverse focus was studied by solving the fifth-order Rung–Kutta equation. The results show that the RF cavity is not only a key component of longitudinal compression but also affects the transverse focusing. While the effect of transverse focus on longitudinal duration is negligible. By adjusting the position and compression strength of the RF cavity, the beam spot radius can be reduced from 100 μm to 30 μm under the simulation conditions in this paper. When the number of single pulse electrons remains constant, the electrons density incident on the sample could be increased from 3.18×1012 m−2 to 3.54×1013 m−2, which is 11 times the original. The larger the electron density incident on the sample, the greater the signal intensity, which is more conducive to detecting the transient evolution of the material.

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Yamaguchi, Takashi, Hiroki Morimoto et Hiroyuki Toda. « RF output-power enhancement by optical-pulse compression in photonic-based RF generation ». URSI Radio Science Bulletin 2017, n^o 361 (juin 2017) : 26–33. http://dx.doi.org/10.23919/ursirsb.2017.8113429.

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Berger, Joel A., et W. Andreas Schroeder. « Semianalytic model of electron pulse propagation : Magnetic lenses and rf pulse compression cavities ». Journal of Applied Physics 108, n^o 12 (15 décembre 2010) : 124905. http://dx.doi.org/10.1063/1.3512847.

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Ferrario, Massimo, et Tsumoru Shintake. « High Performance Electron Injectors ». Reviews of Accelerator Science and Technology 03, n^o 01 (janvier 2010) : 221–35. http://dx.doi.org/10.1142/s1793626810000464.

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Fourth generation light sources based on high gain free electron lasers require production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake field effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, and hence the design of the injector and its operation constitute the leading edge for high quality beam production and for the success of the future light sources. RF and DC guns, cathode materials, laser pulse shaping and sub-picosecond synchronization systems are evolving toward a mature technology to produce high quality and stable beams. Nevertheless, reduction of thermal emittance, damping of emittance oscillations and bunch compression are still the main issues and challenges for injector designs. With the advent of energy recovery linacs, superconducting RF guns have been also considered in many new projects as a possible electron source operating in CW mode. An overview of recent advancements and future perspectives of high performance electron injectors are presented in this article.

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Guo, Jiquan, et Sami Tantawi. « Active RF pulse compression using an electrically controlled semiconductor switch ». New Journal of Physics 8, n^o 11 (28 novembre 2006) : 293. http://dx.doi.org/10.1088/1367-2630/8/11/293.

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Sirenko, Kostyantyn, Vadim Pazynin, Yuriy K. Sirenko et Hakan Bağci. « COMPRESSION AND RADIATION OF HIGH-POWER SHORT RF PULSES. I. ENERGY ACCUMULATION IN DIRECT-FLOW WAVEGUIDE COMPRESSORS ». Progress In Electromagnetics Research 116 (2011) : 239–70. http://dx.doi.org/10.2528/pier11022003.

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Artemenko, S. N., S. A. Gorev, V. S. Igumnov et Yu G. Yushkov. « Formation of long nanosecond rectangular pulses in the active RF pulse compression system with a compact resonant cavity ». Journal of Physics : Conference Series 830 (4 mai 2017) : 012030. http://dx.doi.org/10.1088/1742-6596/830/1/012030.

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Zagni, Nicolò, Giovanni Verzellesi et Alessandro Chini. « Temperature-Independent Current Dispersion in 0.15 μm AlGaN/GaN HEMTs for 5G Applications ». Micromachines 13, n^o 12 (17 décembre 2022) : 2244. http://dx.doi.org/10.3390/mi13122244.

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Thanks to high-current densities and cutoff frequencies, short-channel length AlGaN/GaN HEMTs are a promising technology solution for implementing RF power amplifiers in 5G front-end modules. These devices, however, might suffer from current collapse due to trapping effects, leading to compressed output power. Here, we investigate the trap dynamic response in 0.15 μm GaN HEMTs by means of pulsed I-V characterization and drain current transients (DCTs). Pulsed I-V curves reveal an almost absent gate-lag but significant current collapse when pulsing both gate and drain voltages. The thermally activated Arrhenius process (with EA ≈ 0.55 eV) observed during DCT measurements after a short trap-filling pulse (i.e., 1 μs) indicates that current collapse is induced by deep trap states associated with iron (Fe) doping present in the buffer. Interestingly, analogous DCT characterization carried out after a long trap-filling pulse (i.e., 100 s) revealed yet another process with time constants of about 1–2 s and which was approximately independent of temperature. We reproduced the experimentally observed results with two-dimensional device simulations by modeling the T-independent process as the charging of the interface between the passivation and the AlGaN barrier following electron injection from the gate.

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Li, Ming, Rony E. Amaya, Robert G. Harrison et N. Garry Tarr. « X-Parameter Measurement of Pulse-Compression Nonlinear Transmission Lines ». Journal of Electrical and Computer Engineering 2010 (2010) : 1–5. http://dx.doi.org/10.1155/2010/415315.

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X-parameters provide a powerful and eminently practical solution for interoperable measurement, modeling, and simulation of nonlinear microwave and RF components. UsingX-parameters to do large-signal measurements has been brought into the spotlight. This paper introduces a newX-parameter application: measuring large-signal behaviour of pulse-compression nonlinear transmission lines (NLTLs). A specially configured Nonlinear Vector Network Analyzer (NVNA) was used to measure theX-parameters in the frequency-domain, and then the measured data was transformed into a nonlinear time-domain waveform. The results show both rise-time and fall-time reduction (double-edge compression) as expected and indicate that this newly developedX-parameter method implemented with an NVNA could correctly predict NLTLs' pulse-compression performance.

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Xiaoxi Xu, J. Schein, Niansheng Qi, R. R. Prasad, M. Krishnan, T. Fumihiko et S. G. Tantawi. « The development of a diamond switch for RF pulse compression systems ». IEEE Transactions on Plasma Science 29, n^o 1 (2001) : 85–92. http://dx.doi.org/10.1109/27.912946.

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Dong, Yicong, Karen M. Dowling, Stefan P. Hau-Riege, Adam Conway, Lars F. Voss et Shaloo Rakheja. « Design considerations for gallium arsenide pulse compression photoconductive switch ». Journal of Applied Physics 131, n^o 13 (7 avril 2022) : 134504. http://dx.doi.org/10.1063/5.0083672.

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In this paper, we present the physics and design-space exploration of a novel pulse compression photoconductive switch (PCPS) using semi-insulating gallium arsenide (GaAs) operating in the negative differential mobility (NDM) regime of electron transport. We systematically quantify the relationship between the PCPS performance and various design options, including contact separation, laser energy and placement, and trap dynamics. Specifically, we report the full-width at half-maximum and the peak output current generated by the PCPS as a function of applied electrical and optical bias. We discuss the optimal spacing between the electrodes and the distance of the laser spot to the anode to achieve higher electron confinement and superior radio-frequency (RF) metrics. Reducing the laser energy is important to prevent the appearance of secondary peaks due to diffusive transport, but there exists a trade-off between the bandwidth and the maximum current of the PCPS. We also compare the PCPS response with and without trap dynamics and find that the electrostatic screening from the trap-induced space charge is time-independent when the trapping time constant is set larger than the recombination lifetime. Overall, trap dynamics are detrimental to performance, unless the compensation doping scheme to achieve semi-insulating GaAs is carefully selected. Results presented in this paper can be used by experimentalists to fine-tune the PCPS design parameters to meet the specifications of various RF applications. Moreover, our results will provide a strong theoretical basis to the measurements of PCPS devices using GaAs and other NDM materials under investigation.

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Otto, Martin R., Laurent P. René de Cotret, Mark J. Stern et Bradley J. Siwick. « Robust sub-50 fs cavity-laser phase stabilization for ultra-fast electron diffraction instruments ». EPJ Web of Conferences 205 (2019) : 08015. http://dx.doi.org/10.1051/epjconf/201920508015.

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A novel laser-RF cavity synchronization scheme was developed for ultrafast electron diffraction instruments. The approach directly generates a synchronized microwave tone by retrieving a phase-locked high-harmonic by photodetection. The radio-frequency cavity which performs electron pulse compression is detuning compensated using an active phase stabilization loop. Timing stability improved from 100 fs to 5 fs RMS and long-term time-zero stability improved to below our measurement resolution of 50 fs determined by pulse streaking.

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Tantawi, S. G., R. D. Ruth, A. E. Vlieks et M. Zolotorev. « Active high-power RF pulse compression using optically switched resonant delay lines ». IEEE Transactions on Microwave Theory and Techniques 45, n^o 8 (1997) : 1486–92. http://dx.doi.org/10.1109/22.618460.

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Sirenko, Kostyantyn, Vadim Pazynin, Yuriy K. Sirenko et Hakan Bağci. « COMPRESSION AND RADIATION OF HIGH-POWER SHORT RF PULSES. II. A NOVEL ANTENNA ARRAY DESIGN WITH COMBINED COMPRESSOR/RADIATOR ELEMENTS ». Progress In Electromagnetics Research 116 (2011) : 271–96. http://dx.doi.org/10.2528/pier11022004.

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Yang, Jing, Bin Zhao et Bo Liu. « Coherent Pulse-Compression Lidar Based on 90-Degree Optical Hybrid ». Sensors 19, n^o 20 (21 octobre 2019) : 4570. http://dx.doi.org/10.3390/s19204570.

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A coherent pulse-compression lidar system based on a 90-degree optical hybrid is demonstrated in this paper. In amplitude modulation (AM) mode, the returned RF chirp signal will be influenced by a random phase difference between local oscillator and echo light, causing fluctuations in the ranging results, and as a result the detection probability is small. By using the 90-degree optical hybrid, two orthogonal complementary signals are obtained to stabilize the result so as to increase the detection probability. We performed an experiment to measure the distance of a white printed wall which is about 65 m away from the system. The detection probability increased from 65% to 99.88%, and the precision is improved from 0.42 m to 0.27 m.

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Ivanov, O. A., V. A. Isaev, M. A. Lobaev, A. L. Vikharev et J. L. Hirshfield. « A resonance switch employing an explosive-emission cathode for high-power rf pulse compressors ». Applied Physics Letters 97, n^o 3 (19 juillet 2010) : 031501. http://dx.doi.org/10.1063/1.3466911.

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Wang, Xin, Yonglan Yang, Xing Li et Weiwen Zou. « Theoretical and Experimental Optimization of SBS-Based Pulse Compression of RF Broadband Signal ». IEEE Photonics Technology Letters 33, n^o 24 (15 décembre 2021) : 1475–78. http://dx.doi.org/10.1109/lpt.2021.3128135.

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Kim, Hyoung-Jun, Amir Rashidinejad et Andrew M. Weiner. « Low-Loss Ultrawideband Programmable RF Photonic Phase Filter for Spread Spectrum Pulse Compression ». IEEE Transactions on Microwave Theory and Techniques 63, n^o 12 (décembre 2015) : 4178–87. http://dx.doi.org/10.1109/tmtt.2015.2495172.

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Gao, Meng, Hubert Jean-Ruel, Ryan R. Cooney, Jonathan Stampe, Mark de Jong, Maher Harb, German Sciaini, Gustavo Moriena et R. J. Dwayne Miller. « Full characterization of RF compressed femtosecond electron pulses using ponderomotive scattering ». Optics Express 20, n^o 11 (11 mai 2012) : 12048. http://dx.doi.org/10.1364/oe.20.012048.

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Rimjaem, S., V. Jinamoon, N. Kangrang, K. Kusoljariyakul, J. Saisut, C. Thongbai, Thiraphat Vilaithong, M. W. Rhodes, P. Wichaisirimongkol et S. Chumphongphan. « Femtosecond Electron Pulses Production System ». Solid State Phenomena 107 (octobre 2005) : 15–20. http://dx.doi.org/10.4028/www.scientific.net/ssp.107.15.

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The SURIYA project is designed to generate femtosecond (fs) electron pulses at the Fast Neutron Research Facility (FNRF), Thailand. The fs electron pulses production system consists mainly of a thermionic cathode RF-gun, a magnetic bunch compressor in form of an alpha magnet (α-magnet), a linear accelerator (linac), a beam transport line, and various electron beam diagnostic instruments. This system aims to produce a 20-25 MeV electron beam with micropulses of less than 100 fs in length. Theses pulses can be used either for direct experimentation or to produce fs pulses of intense coherent far infrared radiation (FIR) and/or x-ray. In this paper, an overview of the system and characteristics of its major components will be presented.

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Li, Ming, Rony E. Amaya, Robert G. Harrison et N. Garry Tarr. « Investigation of CMOS Varactors for High-GHz-Range Applications ». Research Letters in Electronics 2009 (2009) : 1–4. http://dx.doi.org/10.1155/2009/535809.

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This paper explores a variety of different CMOS varactor structures for RF and MMICs. A typical 0.18 μm CMOS foundry process was used as the study platform. The varactors' capacitance-voltage characteristics and cutoff frequencies have been examined up to 55 GHz. The primary aim of this work is to design varactors that can improve nonlinear-transmission-line (NLTL) pulse-compression circuits. The results should also be valuable for other applications up to millimeter wavelengths.

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Ghelfi, Paolo, Filippo Scotti, Francesco Laghezza et Antonella Bogoni. « Photonic Generation of Phase-Modulated RF Signals for Pulse Compression Techniques in Coherent Radars ». Journal of Lightwave Technology 30, n^o 11 (juin 2012) : 1638–44. http://dx.doi.org/10.1109/jlt.2012.2187879.

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Goodsitt, Mitchell M., Alan R. Bleier et Frank E. Barber. « An Improved Ultrasound Simulation Model : Use in Evaluating Log versus Linear Processing for Lesion Detection ». Ultrasonic Imaging 9, n^o 4 (octobre 1987) : 260–70. http://dx.doi.org/10.1177/016173468700900404.

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This paper reports the development of an improved three-dimensional computer simulation model for evaluation of ultrasonic imaging systems. This model was used to successfully evaluate a signal processing method for improving lesion detection in ultrasound imaging. Linear processing of the rf signal amplitudes from a limited region of tissue was compared with the logarithmic compression employed by most commercial scanners. Two lesions were simulated by spherical distributions of scatterers having backscatter coefficients greater than the scatterers in the surrounding medium. Linear processing improved the differential contrast by a factor of about two. The simulation is based on the three-dimensional distribution of acoustic frequency spectra in a transducer beam and integration of scattered pulses from a corresponding three-dimensional array of scatterers. The simulation reported in previous papers depended upon physical measurement of the impulse response of a transducer. An original contribution described briefly herein, and in more detail in a companion article, is the addition of a model of the transducer's pulse waveform generation. Another new addition is the definition of a specific lesion detection task for objective assessment of a change in image quality following perturbation of some system parameter.

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Katayama, T., A. Itano, A. Noda, M. Takanaka, S. Yamada et Y. Hirao. « Design study of a heavy ion fusion driver, HIBLIC ». Laser and Particle Beams 3, n^o 1 (février 1985) : 9–27. http://dx.doi.org/10.1017/s0263034600001221.

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A heavy ion fusion (HIF) system, named HIBLIC (Heavy Ion Beam and LIthium Curtain) is conceptually designed. The driver system consists of RF linacs (RFQ linacs, IH linacs and Alvarez linacs), storage rings (one accumulator ring and three buncher rings) and beam transport lines with induction beam compressors. This accelerator complex provides 6 beams of 15 GeV208Pb1+ ions to be focused simultaneously on a target. Each beam carries 1·78 kA current with 25 ns pulse duration, i.e., the total incident energy on the target is 4 MJ, 160 TW per shot. Superconducting coils are used in most parts of the magnet system to reduce power consumption.

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Li, Hong Mei, Ying Chao Han et Jing Hui Qiu. « Analytical Investigation of Radiation Characteristic for Radio Frequencies Magnetic Flux Compression Generator ». Applied Mechanics and Materials 143-144 (décembre 2011) : 796–99. http://dx.doi.org/10.4028/www.scientific.net/amm.143-144.796.

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Radio frequencies magnetic flux compression generator is capable of producing and radiating ultra high power electromagnetic pulse by compressing magnetic field. As a maneuverable device, radio frequencies magnetic flux compression generator design has been developed and tested, it has been found widespread use in many fields. The radio performance is one of the most important parameters for radio frequencies magnetic flux compression generator. In this paper, the output current and voltage is given based on equivalent circuit model. In a bid to deliberate the radiation characteristic particularly, ring armature is equivalent to loop antenna in the light of electrically small loop antenna theory. The output voltage is used to feed antenna. Through analysis, the values of radiation strengths around radio frequencies magnetic flux compression generator 10 meters 50 meters 100 meters away are given. On the basis of the above analysis and discussion, the radiation characteristic for RF MFCG could be comprehended precisely.

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Savilov, A. V. « Compression of complicated rf pulses produced from the super-radiant backward-wave oscillator ». Applied Physics Letters 97, n^o 9 (30 août 2010) : 093501. http://dx.doi.org/10.1063/1.3484963.

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ALESINI, D., S. BERTOLUCCI, M. E. BIAGINI, R. BONI, M. BOSCOLO, M. CASTELLANO, A. CLOZZA et al. « The SPARC/X SASE-FEL Projects ». Laser and Particle Beams 22, n^o 3 (juillet 2004) : 341–50. http://dx.doi.org/10.1017/s0263034604223199.

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SPARC and SPARX are two different initiatives toward an ItalianFreeElectronLaser (FEL) source operating in theSelfAmplifiedSpontaneousEmission (SASE) mode, in which several national research institutions are involved. SPARC is a high gain FEL project devoted to provide a source of visible and VUV radiation while exploiting the SASE mechanism. An advanced Photo-Injector system, emittance compensating RF-gun plus a 150 MeV Linac, will inject a high quality e-beam into the undulator to generate high brilliance FEL radiation in the visible region at the fundamental wavelength, (∼500 nm). The production of flat top drive laser beams, high peak current bunches, and emittance compensation scheme will be investigated together with the generation of higher harmonic radiation in the VUV region. SPARX is the direct evolution of such a high gain SASE FEL toward the 13.5 and 1.5 nm operating wavelengths, at 2.5 GeV. To get the required value for the bunch peak current, Ipeak≈ 2.5 kA, the “hybrid” scheme, RF-compression stage plus magnetic chicane, is analyzed and compared with the more standard double stage of magnetic compression. The two options are reviewed considering the tolerance to the drive laser pulse phase jitter.

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Battaglia, Brian, Dave Rice, Phuong Le, Bishnu Gogoi, Mike Purchine, Robert Davies, Walt Wright et al. « A rugged 100 W high-voltage vertical MOSFET L-band radar device ». International Journal of Microwave and Wireless Technologies 1, n^o 4 (19 juin 2009) : 277–84. http://dx.doi.org/10.1017/s1759078709990298.

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The silicon vertical MOSFET RF power amplifier described in this paper is the industry’s first to utilize high-voltage vertical technology. Operating under pulse conditions of 200 µs pulse width and 10% duty cycle, it delivers more than 100 W of peak power. Operating in Class AB with only 50 mA of bias current the device achieves more than 20 dB of gain and 47% power added efficiency at P1dB compression across 200 MHz of bandwidth at L-band from 1.2 to 1.4 GHz. The DC characteristics include a BVdss of 95 V enabling high-voltage operation with a 48 V power supply. The device is inherently rugged and withstands mismatch tolerances of 20:1 voltage standing wave ratio over all phase angles at full rated power and with 3 dB of input power over-drive and 10% greater than nominal voltage.

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Khan, Asif Mehmood, Muhammad Mansoor Ahmed et Umair Rafique. « Experimental Study of RF–Plasma Interaction Using a Low-Pressure DC Glow Discharge Tube for MPC ». Electronics 12, n^o 3 (20 janvier 2023) : 551. http://dx.doi.org/10.3390/electronics12030551.

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This paper aims to perform experimental validation of RF–plasma interaction behaviors for the purposes of wave transmission and reflection. Wave reflection from plasma is of interest as it finds applications in pulse compression and RF polarizer-based systems. Simulations are performed using a combination of Magic3D and COMSOL multiphysics to characterize the plasma–wave interaction and discharge tube properties. The goal is to generate plasma with characteristics that wholly reflect the incident electromagnetic wave. A glass tube of inner diameter 22 mm and length 100 mm, with 12 mm brass electrodes, is fabricated for plasma generation. Argon-based DC glow discharge is sustained at 500 volts at a pressure of 3.8 Torr. Plasma density is calculated to be 2.529×1019 m−3, with a corresponding plasma frequency of 7.18 GHz. Due to this higher frequency, a 3 GHz incident RF wave is reflected, as measured through S-parameter measurements using a network analyzer. Off and on states of the tube correspond to S11=−40 dB and S11=−13 dB, which show wave transmission and reflection, respectively. When the plasma column is ignited, the reflected wave has a phase difference of 180∘.

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Artemenko, S. N. « Formation of nanosecond RF pulses in an autogenerator by resonance compression of microwave energy ». Radiophysics and Quantum Electronics 41, n^o 7 (juillet 1998) : 616–24. http://dx.doi.org/10.1007/bf02675849.

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Tudose, Mihai-Liviu, Andrei Anghel, Remus Cacoveanu et Mihai Datcu. « Pulse Radar with Field-Programmable Gate Array Range Compression for Real Time Displacement and Vibration Monitoring ». Sensors 19, n^o 1 (27 décembre 2018) : 82. http://dx.doi.org/10.3390/s19010082.

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This paper aims to present the basic functionality of a radar platform for real time monitoring of displacement and vibration. The real time capabilities make the radar platform useful when live monitoring of targets is required. The system is based on the RF analog front-end of a USRP, and the range compression (time-domain cross-correlation) is implemented on the FPGA included in the USRP. Further processing is performed on the host computer to plot real time range profiles, displacements, vibration frequencies spectra and spectrograms (waterfall plots) for long term monitoring. The system is currently in experimental form and the present paper aims to prove its functionality. The precision of this system is estimated (using the 3σ approximation) at 0.6 mm for displacement measurements and 1.8 mm for vibration amplitude measurements.

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Hofmann, Ingo. « Principles of non-Liouvillean pulse compression by photoionization for heavy-ion fusion drivers ». Laser and Particle Beams 8, n^o 4 (décembre 1990) : 527–39. http://dx.doi.org/10.1017/s026303460000896x.

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Photoionization of single-charged heavy ions has been proposed recently by Rubbia (1989) as a non-Liouvillean injection scheme from the linac into the storage rings of a driver accelerator for inertial confinement fusion. The main idea of this scheme is the accumulation of high currents of heavy ions without the usually inevitable increase of phase space. Here we suggest the use of the photoionization idea in an alternative scheme: if it is applied at the final stage of pulse compression (replacing the conventional bunch compression by an rf voltage, which always increases the momentum spread), there is a significant advantage in the performance of the accelerator. We show, in particular, that this new compression scheme can potentially relax the tough stability limitations, which were identified in the heavy-ion fusion reactor study HIBALL (Badger et al. 1984). Moreover, it is promising for achieving higher beam power, which is suitable for indirectly driven fusion targets (1016 W/g, in contrast with 1014 W/g for the directly driven targets in HIBALL).The idea of non-Liouvillean bunch compression is to stack a large number of bunches (typically 50–100) in the same phase-space volume during a change of charge state of the ion. A particular feature of this scheme with regard to beam dynamics is its transient nature, since the time required is one revolution per bunch. After the stacking the intense bunch is ejected and directly guided to the target. The present study is a first step in exploring the possibly limiting effect of space charge under the parameter conditions of a full-size driver accelerator. Preliminary results indicate that there is a limit to the effective stacking number (non-Liouvillean “compression factor”), which is, however, not prohibitive. Requirements on the power of the photon beam from a free-electron laser are also discussed. It is seen that resonant cross sections of the order of 10−15 cm2 lead to photon beam powers of a few megawatts.

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Song, Yuxiao, Yu Wang, Jingyang Xie, Yiming Yang, Biao Tian et Shiyou Xu. « Ultra-Low Sidelobe Waveforms Design for LPI Radar Based on Joint Complementary Phase-Coding and Optimized Discrete Frequency-Coding ». Remote Sensing 14, n^o 11 (28 mai 2022) : 2592. http://dx.doi.org/10.3390/rs14112592.

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In this paper, in order to reduce the probability of the radar waveform intercepted by the passive detection system, the time-bandwidth product of the radar waveform is increased, and the detection probability of the radar waveform to the target is improved. This paper tackles the holographic RF stealth radar and proposes a joint coding waveform based on the linear frequency modulation (LFM) waveform. Joint coding uses complementary codes to perform phase-coding, and combines the codewords optimized by genetic algorithm in order to perform discrete frequency-coding waveform. The joint coding waveform model is theoretically analyzed, and the ambiguity function, pulse compression and target detection probability of the joint coding waveform are obtained by numerical simulation. In addition, the complexity of the algorithm and the low probability of intercept (LPI) characteristic of the joint coding waveform are analyzed. The results show that the joint coding waveform has an approximate “pushpin” ambiguity function, ultra-low sidelobe characteristics, better RF stealth and target detection performance. Finally, it has good application prospects in the current battlefield environment.

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Hou, Yidong, Biyang Wen, Yonghuai Yang, Jing Yang et Caijun Wang. « Two-Dimensional River Flow Patterns Observed with a Pair of UHF Radar System ». International Journal of Antennas and Propagation 2017 (2017) : 1–11. http://dx.doi.org/10.1155/2017/4792324.

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A pair of ultrahigh-frequency (UHF) radars system for measuring the two-dimensional river flow patterns is presented. The system consists of two all-digital UHF radars with exactly the same hardware structure, operating separately at 329–339 MHz and 341–351 MHz. The adoption of direct radio frequency (RF) sampling technique and digital pulse compression simplifies the structure of radar system and eliminates the distortion introduced by the analog mixer, which improves the SNR and dynamic range of the radar. The field experiment was conducted at Hanjiang River, Hubei province, China. Over a period of several weeks, the radar-derived surface velocity has been very highly correlated with the measurements of EKZ-I, with a correlation coefficient of 0.958 and a mean square error of 0.084 m/s.

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Atia, Yosi, Yuval Elias, Tal Mor et Yossi Weinstein. « Quantum computing gates via optimal control ». International Journal of Quantum Information 12, n^o 05 (août 2014) : 1450031. http://dx.doi.org/10.1142/s0219749914500312.

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We demonstrate the use of optimal control to design two entropy-manipulating quantum gates which are more complex than the corresponding, commonly used, gates, such as CNOT and Toffoli (CCNOT): A two-qubit gate called polarization exchange (PE) and a three-qubit gate called polarization compression (COMP) were designed using GRAPE, an optimal control algorithm. Both gates were designed for a three-spin system. Our design provided efficient and robust nuclear magnetic resonance (NMR) radio frequency (RF) pulses for 13 C 2-trichloroethylene (TCE), our chosen three-spin system. We then experimentally applied these two quantum gates onto TCE at the NMR lab. Such design of these gates and others could be relevant for near-future applications of quantum computing devices.

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Morgan, David P. « A HISTORY OF SURFACE ACOUSTIC WAVE DEVICES ». International Journal of High Speed Electronics and Systems 10, n^o 03 (septembre 2000) : 553–602. http://dx.doi.org/10.1142/s0129156400000593.

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This paper gives a historical account of the development of Rayleigh-wave, or surface-acoustic-wave (SAW), devices for applications in electronics. The subject was spurred on initially by the requirements of pulse compression radar, and became a practical reality with the planar interdigital transducer, dating from 1965. The accessibility of the propagation path gave rise to substantial versatility, and a huge variety of devices were developed. Passive SAW devices are now ubiquitous, with applications ranging from professional radar and communications systems to consumer areas such as TV, pagers and mobile phones. The paper describes the extensive work, particularly in the 1970s, to investigate SAW propagation in crystalline media, including piezoelectric coupling, diffraction and temperature effects. This led to identification of many suitable materials. Concurrently, many devices began development, including pulse compression filters, bandpass filters, resonators, oscillators, convolvers and matched filters for spread spectrum communications. In the 1970s, many of these became established in professional systems, and the SAW bandpass filter became a standard component for domestic TV. In the 1980s and 90s, SAW responded to the new call for low-loss filters, particularly for mobile phones. With losses as low as 2 dB required (and subsequently achieved) at RF frequencies around 900 MHz, a raft of new technologies was developed. Additionaly, for IF filters special techniques were evolved to reduce the physical size needed for narrow bandwidths. Such devices are now manufactured in very large quantities. In order to satisfy these needs, new types of surface wave, particularly transverse leaky waves, were investigated, and materials using such waves now have their place alongside more traditional materials.

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Zhang, Nai, Asao Terukina, Hiromasa Ito et Humio Inaba. « Compression of picosecond optical pulses from a strongly RF modulated InGaAsP DBR diode laser using a gires-tournois interferometer ». Electronics and Communications in Japan (Part II : Electronics) 71, n^o 12 (1988) : 100–107. http://dx.doi.org/10.1002/ecjb.4420711212.

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Luttikhof, M. J. H., A. G. Khachatryan, F. A. van Goor, K. J. Boller et P. Mora. « Electron bunch injection at an angle into a laser wakefield ». Laser and Particle Beams 27, n^o 1 (8 janvier 2009) : 69–77. http://dx.doi.org/10.1017/s0263034609000093.

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AbstractExternal injection of electron bunches longer than the plasma wavelength in a laser wakefield accelerator can lead to the generation of femtosecond ultra relativistic bunches with a couple of percent energy spread. Extensive study has been done on external electron bunch (e.g., one generated by a photo-cathode RF linac) injection in a laser wakefield for different configurations.In this paper, we investigate a new way of external injection where the electron bunch is injected at a small angle into the wakefield. This way one can avoid the ponderomotive scattering as well as the vacuum-plasma transition region, which tend to destroy the injected bunch. In our simulations, the effect of the laser pulse dynamics is also taken into account. It is shown that injection at an angle can provide compressed and accelerated electron bunches with less than 2% energy spread. Another advantage of this scheme is that it has less stringent requirements in terms of the size of the injected bunch and there is the potential to trap more charge.

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