共查询到20条相似文献,搜索用时 31 毫秒
1.
A. B. Danilov E. M. Il’ina V. P. Kudryashov I. V. Polyakov 《Journal of Communications Technology and Electronics》2013,58(6):551-556
Mathematical expressions showing that the optimum way of suppressing the self-excitation of a backward-wave traveling-wave tube is to decrease the diameter and pitch of the slow-wave structure toward the energy output are obtained. The conditions for the values of the diameter and pitch before and after the decrease are found under which the phase velocities of the minus first spatial harmonic (backward wave) are maximally different, which ensures the maximum suppression of self-excitation, and phase velocities of the zero harmonic are optimal for obtaining the maximum efficiency. 相似文献
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Yu. N. Pchelnikov A. A. Elizarov 《Journal of Communications Technology and Electronics》2009,54(9):1027-1034
The limitations on the output power and operating frequency of the broadband TWTs resulting from a relatively low thermal
stability of helix and the self-excitation at the backward wave at a operating voltage of greater than 10 kV are considered.
The analysis yields the methods to overcome limitations: the application of a bifilar helix with the azimuthally conducting
rings and the application of combined metal-dielectric supports that allow a simultaneous improvement of the heat removal
from the helix and an increase in the TWT band. It is demonstrated that a decrease in the slowing caused by the rings and
a smaller period of the bifilar helix make it possible to shift the threshold of the self-excitation at the backward wave
to 30–40 kV. 相似文献
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Yu. N. Pchelnikov 《Journal of Communications Technology and Electronics》2011,56(4):450-457
On the basis of a physical notions of the specific features of the slow-wave field distribution in the helix structure of
a traveling-wave tube (TWT), various methods for controlling the amount of wave slowing and the slope of the dispersion characteristic
are analyzed. The effect of the dielectric supports and correcting elements placed outside the helix is considered. In addition
to the known methods for correcting dispersion through the use of a dielectric shield and longitudinally conducting elements,
which weaken the interaction with the electron flow, new methods that provide both an efficient interaction with the electrons
and the possibility of operation without backward-wave self-excitation at voltages higher than the voltages used with conventional
helices are proposed and analyzed. With an analysis based on the equivalent-line method, it is shown that the slope of the
helix dispersion characteristic can be decreased by the appropriate use of ring-shaped supports. Design solutions using the
new methods of correction are considered. The history of development of ultrabroadband TWTs, including the work done in the
Soviet Union on tubes with centrifugal electrostatic focusing, whose actual amplification band can be as wide as three octaves,
is partially presented. 相似文献
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《Electron Devices, IEEE Transactions on》1955,2(2):20-31
An experimental study has been made of the filter helix properties of a periodically loaded helix, using a special traveling-wave tube. The filter helix is shown to possess filter-like frequency pass bands and stop bands and a phase velocity characteristic such that forward- and backward-wave phase velocities are separated, making the filter helix a useful circuit for traveling-wave amplification at high ka (ratio of helix circumference to free space wavelength) without danger of backward-wave oscillation. Certain difficulties associated with backward-wave oscillation frequency pushing were found to arise in filter helices, but useful gain was obtained at ka greater than 0.5 using filter helix techniques. 相似文献
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Yu. N. Pchelnikov 《Journal of Communications Technology and Electronics》2011,56(4):404-418
On the basis of a physical notions of the specific features of the slow-wave field distribution in the helix structure of a traveling-wave tube (TWT), various methods for controlling the amount of wave slowing and the slope of the dispersion characteristic are analyzed. The effect of the dielectric supports and correcting elements placed outside the helix is considered. In addition to the known methods for correcting dispersion through the use of a dielectric shield and longitudinally conducting elements, which weaken the interaction with the electron flow, new methods that provide both an efficient interaction with the electrons and the possibility of operation without backward-wave self-excitation at voltages higher than the voltages used with conventional helices are proposed and analyzed. With an analysis based on the equivalent-line method, it is shown that the slope of the helix dispersion characteristic can be decreased by the appropriate use of ring-shaped supports. Design solutions using the new methods of correction are considered. The history of development of ultrabroadband TWTs, including the work done in the Soviet Union on tubes with centrifugal electrostatic focusing, whose actual amplification band can be as wide as three octaves, is partially presented. 相似文献
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《Electron Devices, IEEE Transactions on》1958,5(3):152-156
A 20 to 40-kmc backward-wave oscillator is described which employs a single-tape helix with a mean diameter of 0.039 inch and a length of 1.75 inch supported internally by a triangular sapphire rod. Physically, the helix is mounted in a hole drilled in the ridge of the output ridge waveguide, and a closely spaced hollow beam is located on the outside of the helix. The output from the helix passes through a short section of coaxial line to the ridge waveguide and then along this guide and through the vacuum envelope to an external mating ridge waveguide. The two sections of guide meet the envelope at an angle of 13 degrees. Output is obtained from the oscillator from 18 to 40 kmc with a voltage range of 300 to 2600 volts. The RF output varies relatively smoothly and exceeds 2 milliwatts with 5-ma collector current over the entire band from 21 to 37.5 kmc. The total variation of power over this band is 6 db. It is expected that this tube will be useful for signal-generator-type applications. 相似文献
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Datta S.K. Jain P.K. Narayan M.D.R. Basu B.N. 《Electron Devices, IEEE Transactions on》1999,46(2):420-426
Eulerian hydrodynamics was developed to study the nonlinear problem of second harmonic generation in a helix traveling-wave tube (TWT). A closed-form expression for the second-harmonic component of RF output power was obtained. The method required the specification of the dispersion and interaction impedance characteristics of the helical slow-wave structure (SWS) used in the device, obtainable by the field analysis of the SWS. Care was taken however to restrict the present Eulerian theory to the correct regime, which was found in terms of the RF input power drive and the device interaction length, by validating the theory against the more accurate Lagrangian theory. Within this regime, that was below the saturation level of the device, the effect of the dispersion of the SWS on the second harmonic generated in the device was studied. It was found that, irrespective of whether the dispersion of the SWS is positive or negative, the second harmonic content of the device decreased with the amount of the dispersion. Furthermore, though both the fundamental and the second harmonic content of the device decreased with the distributed loss on the SWS, the second harmonic relative to the fundamental showed a minimum at an optimum value of the distributed loss 相似文献
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V. O. Melikhov M. V. Nazarov V. A. Solntsev 《Journal of Communications Technology and Electronics》2009,54(12):1403-1412
The equations that describe nonlinear nonstationary processes in carcinotrode (backward-wave tube with the emission modulation
in the presence of the field of the output signal fed to the cathode via a feedback loop) are derived. An algorithm and the
corresponding code are developed to solve the equations with allowance for the modulation of emission using nonuniform (with
respect to time) large particles (electrons of equal charge) ejected from the cathode. The effect of the feedback parameter
on the intensity and shape of the carcinotrode oscillations is analyzed. It is demonstrated that the carcinotrode efficiency
can be increased to about 50% upon the generation of harmonic oscillations. A more significant increase in the efficiency
to 70% is possible in the regime of the weak self-modulation of oscillations upon an increase in the feedback coefficient
in the feedback loop involving the slow-wave structure and the cathode and a decrease in the cathode-grid static field. 相似文献
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A highly linear and efficient differential CMOS power amplifier with harmonic control 总被引:3,自引:0,他引:3
Jongchan Kang Jehyung Yoon Kyoungjoon Min Daekyu Yu Joongjin Nam Youngoo Yang Bumman Kim 《Solid-State Circuits, IEEE Journal of》2006,41(6):1314-1322
A 2.45 GHz fully differential CMOS power amplifier (PA) with high efficiency and linearity is presented. For this work, a 0.18-/spl mu/m standard CMOS process with Cu-metal is employed and all components of the two-stage circuit except an output transformer and a few bond wires are integrated into one chip. To improve the linearity, an optimum gate bias is applied for the cancellation of the nonlinear harmonic generated by g/sub m3/ and a new harmonic termination technique at the common source node is adopted along with normal harmonic termination at the drain. The harmonic termination at the source effectively suppresses the second harmonic generated from the input and output. The amplifier delivers a 20.5dBm of P/sub 1dB/ with 17.5 dB of power gain and 37% of power-added efficiency (PAE). Linearity measurements from a two-tone test show that the power amplifier with the second harmonic termination improves the IMD3 and IMD5 over the amplifier without the harmonic termination by maximally 6 dB and 7 dB, respectively. Furthermore, the linearity improvements appear over a wide range of the power levels and the linearity is maintained under -45 dBc of IMD3 and -57dBc of IMD5 when the output power is backed off by more than 5dB from P/sub 1dB/. From the OFDM signal test, the second harmonic termination improves the error vector magnitude (EVM) by over 40% for an output power level satisfying the 4.6% EVM specification. 相似文献
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An X-band rising sun harmonic-generator magnetron has been developed. In order to obtain enhanced second harmonic output power, the magnetron was designed so that the resonant frequency of the second-order π mode was twice the frequency of the first-order π mode. Second harmonic efficiency, the ratio of second harmonic output power to input power, was strongly magnetic field dependent. Large values of second harmonic efficiency and output power occurred for operation in the "valley of efficiency" of the rising sun anode, i.e., for magnetic fields near B=13,000/λ1 gauss where λ1 is the wavelength of the first-order π mode. Maximum second harmonic efficiency and output power at λ2 =1.69 cm were 13 per cent and 46 kw, respectively. For operation at these magnetic fields the ratio of generated second harmonic to fundamental power was of the order unity. This large power ratio can be understood in terms of a phase shift between the fundamental voltage and the current which drives it, together with a modified rotating wave hypothesis where a waving motion, caused by the Γ=0 Hartree component of the azimuthal electric field, is superimposed on the conventional rotation of the space-charge spokes. 相似文献
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《Electron Device Letters, IEEE》1980,1(6):104-106
Both fundamental and second-harmonic output powers have been computed with an axially symmetric three-dimensional model of a helix traveling-wave amplifier. They agree reasonably well with measurements. For three beam power levels, the computed transfer curves show RF drive powers consistently about 3 dB below the measured powers and saturated output powers about 2 dB below the measured values. Inaccuracies in the assumed initial beam radius, density and velocity may have caused these differences. Suppressing the second harmonic raises the computed fundamental output power by 3 dB. The model accurately reproduces a measured 11 dB dip in the second harmonic as the fundamental signal saturates. 相似文献
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《Electron Devices, IEEE Transactions on》1958,5(4):215-222
Results are presented of an experimental study of the spent beam of a backward-wave oscillator. The instantaneous velocity and current of the spent beam are measured using a velocity analyzer built onto the collector of a scaled 80-mc backward-wave oscillator. The tube employs a sheet beam and interdigital line, 12 feet long. It is designed to be representative of large-space-charge tubes. The measured trajectories of the spent beam are examined to deduce the mechanism of interaction between the beam and the circuit along the whole length of the tube. It is deduced that the level of oscillation is determined by nonlinear effects in the convection current. Finally, the RF output efficiency saturation at high beam currents is found to be caused by electrons which fall back in phase from a retarding to an accelerating circuit field. 相似文献
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The problem of second harmonic generation in a helix travelling-wave tube was studied by Eulerian hydrodynamical analysis. The correct regime of applicability of the Eulerian analysis, with respect to the rf input power drive and the interaction length of the device, was found a priori by validating the analysis against the more accurate Lagrangian analysis. Within this regime of applicability, which necessarily corresponds to the backed-off operation of the device, was studied the second harmonic generated in the device, with particular reference to its control by harmonic injection. In particular, the optimum values of the relative amplitude and phase of the additional second harmonic input signal relative to the main input signal were predicted for the minimum second harmonic output of the device. 相似文献
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The temporal dependence, spectral characteristics, and efficiency of a multimode Q -switched ring laser containing an intracavity second harmonic generator is described. Numerical studies show that such lasers are stable and efficient. Comparison with Q-switched lasers (not containing a second harmonic generator) demonstrates that the intracavity second harmonic generation lasers can be even more efficient than the fundamental laser due to nonlinear output coupling. General considerations for the operation of such lasers are described. Spectral characteristics of the output as a function of the gain of the active medium and the spectrum of the injected pulse are discussed. Instabilities at very high second harmonic conversion are observed 相似文献
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Berini P. Desgagne M. Ghannouchi F.M. Bosisio R.G. 《Microwave Theory and Techniques》1994,42(6):943-950
This paper reports an extensive experimental investigation of the effects of second harmonic loading on the performance of microwave GaAs MESFET oscillators; and strongly driven amplifiers. The measurement system used is an active load system based on six-port techniques. Harmonic load pull measurements were obtained for the NE72084 MESFET; the measurements show how the second harmonic load can influence the power gain and the power added efficiency in strongly driven amplifiers. The device line characterization technique was combined with the harmonic load pull technique; the measurement results illustrate how the output power and the DC to RF conversion efficiency of an oscillator depend on the choice of the second harmonic load. Amplifier and oscillator circuits have been designed using these measurements; the circuits have been constructed and measured. The results validate the experimental approach used and clearly illustrate the importance of properly selecting the second harmonic load in amplifier and oscillator circuits. Significant improvements in gain, output power and efficiency have been achieved by properly selecting the second harmonic load 相似文献
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应用粒子模拟软件对设计的二次谐波三腔回旋速调管放大器进行了数值模拟。分析讨论了二次谐波注-波互作用过程中电子群聚的物理图景和特点,并研究了电子注电流和归一化引导中心半径对电子注-波互作用效率的影响。模拟结果表明,本文设计的二次谐波三腔回旋速调管放大器在35GHz频率可获得约293kW的峰值输出功率和约28%的电子效率。 相似文献