共查询到20条相似文献,搜索用时 31 毫秒
1.
An investigation and application of the contrawound helix 总被引:1,自引:0,他引:1
《Electron Devices, IEEE Transactions on》1959,6(2):195-202
An investigation of the contrawound helix and the determination of its characteristics has been completed. By means of a hollow-beam traveling-wave tube and perturbation methods, the fundamental and minus-one space harmonics impedances have been measured and a number of space harmonics of the symmetric and antisymmetric modes identified. The fundamental impedance was measured to be equal or greater than the sheath-helix impedance depending, however, upon the thickness and width of the helix tape. The minus-one space harmonic impedance was measured to be larger than the fundamental impedance for ka > 0.65. The contrawound helix has been employed as a high-power X-band amplifier (8.5-9.5 kmc). The characteristics of the tube described are 25-db gain, power out > 1 kw, efficiency 7-10 per cent. 相似文献
2.
Axial mode helical antennas 总被引:2,自引:0,他引:2
Nakano H. Samada Y. Yamauchi J. 《Antennas and Propagation, IEEE Transactions on》1986,34(9):1143-1148
The radiation characteristics of helical antennas operating in the axial mode are evaluated on the basis of the theoretical current distributions and are verified by experimental work. A comparison between monofilar helix and bifilar helix antennas is made, and a helical antenna with a parasitic helix (HAP) is proposed in order to enhance the power gain. It is found that the gain of the HAP in which the parasitic helix is wound from a point diametrically opposite to that of one and one-half turns of the driven helix is about 1 dB higher than that of the monofilar helix. The ratio of the frequency band in which the HAP radiates a circularly polarized wave within an axial ratio of 3 dB is calculated to be 1:1.8. 相似文献
3.
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
4.
《Electron Devices, IEEE Transactions on》1962,9(3):288-295
An electron beam in the presence of an axial magnetic field supports four transverse waves; two cyclotron waves, and two synchronous waves. A general coupling theory is developed from an electronic equation and a circuit equation to describe how these waves can be coupled to traveling-wave circuits. The polarization and power flow characteristics of the waves are derived. The theory is applied to. the bifilar helix, a circuit which can couple selectively to each of the four modes. A bifilar helix traveling-wave tube was used to investigate experimentally the four beam modes and provide a quantitative check of the coupling theory. 相似文献
5.
6.
《Electron Devices, IEEE Transactions on》1956,3(1):18-24
The modes of the sheath helix are shown to be related closely to the space harmonics of real helices. Multiwire helices propagate many modes, the principal space-harmonic component of each approaching more closely the appropriate sheath helix mode as the number of wires is increased. Each mode can be excited by a certain phase sequence of exciting currents for the wires in one transverse plane. Experimental verification of the theory is reported using a bifilar helix tube. Phase velocities and impedances are measured, using Kompfner's null method and the start of backward-wave oscillations for the principal forward and backward components respectively. 相似文献
7.
本文提出一种用双线背射螺旋作馈源的新式背射天线。这种天线具有结构简单,馈电方便,增益较高,易于产生圆极化波等优点。 相似文献
8.
《Electron Devices, IEEE Transactions on》1957,4(3):246-264
An important aspect of the design of traveling-wave amplifiers and backward-wave oscillators for frequencies below 500 mc is the problem of obtaining a tube of reasonably small physical dimensions. Hollow beams of greater perveance than is obtainable with solid beams offer one method of reducing the size of such tubes by permitting operation at a lower voltage and greater gain per wavelength, for a specified beam power, than is possible in a solid beam tube. Some aspects of the design of minimum size hollow-beam forward-wave amplifiers using single helix circuits and backward-wave oscillators using bifilar helix circuits are presented. Several tubes of these types for operation below 500 mc have been built. Amplifier bandwidths and oscillator tuning ranges in excess of four to one in frequency have been obtained experimentally. Amplifier efficiencies in excess of 20 per cent and oscillator efficiencies in excess of 10 per cent have been achieved. 相似文献
9.
Shunkang Liu 《Journal of Infrared, Millimeter and Terahertz Waves》1997,18(6):1317-1321
Backward wave oscillations are easy occurred in high power helix millimeter wave traveling wave tubes (MMW TWT’s), owing to larger ka value and higher operating voltage. The start current of backward wave is calculated for helix TWT in Ka band. It is shown that start current will increase by used a tapered helix. Backward wave oscillations can be suppressed in tube. The design method of the tapered helix is given in this paper. 相似文献
10.
The current distribution, the near field, and the far field of helical antennas are examined. It is found that the application of the helix as an endfire radiator is dependent on two higher Order modes of the helix wave functions. This differs from the application of the helix as a slow wave structure in a traveling wave tube where the lowest order mode of the helix wave functions is utilized. 相似文献
11.
Mukesh Kumar Alaria A. Bera A. K. Sinha V. Srivastava 《Journal of Infrared, Millimeter and Terahertz Waves》2009,30(3):211-216
This paper describes the analysis of helix slow-wave structure (SWS) for a high efficiency space traveling wave tube that
is carried out using Ansoft HFSS and CST microwave studio, which is a 3D electromagnetic field simulators. Two approaches
of simulating the dispersion and impedance characteristics of the helix slow wave structure have been discussed and compared
with measured results. The dispersion characteristic gives the information about axial propagation constant (Beta). Which
in turn yields the phase velocity at a particular frequency. The dispersion and impedance characteristics can be used in finding
the pertinent design parameters of the helix slow-wave structure. Therefore a new trend has been initiated at CEERI to use
Ansoft HFSS code to analysis of the helix slow wave structure in its real environment. The analysis of the helix SWS for Ku-band
140W space TWT has been carried out and compared with experimental results, and found is close agreement. 相似文献
12.
Efficiency Enhancement Of Helix Traveling Wave Tube Based On εMulti-Objective Evolutionary Algorithm
Guo-chao Li Pu-kun Liu Liu Xiao Bao-liang Hao 《Journal of Infrared, Millimeter and Terahertz Waves》2010,31(4):500-509
A two-dimensional non-linear helix traveling wave tube (TWT) theory in frequency-domain is described in this article and the
theory is integrated with ε Multi-Objective Evolutionary Algorithm(MOEA). The efficiency optimization of a helix TWT with
phase taper has been done. The optimization results was verified by a three dimensional nonlinear model. The results show
the feasibility and reliability of the optimization algorithm and the two-dimensional nonlinear theory. The integrated program
can provide calculable parameters for the design of helix TWT. It can also accelerate development process and reduce test
costs. 相似文献
13.
Shunkang Liu 《Journal of Infrared, Millimeter and Terahertz Waves》2002,23(6):899-906
The efficiency enhancement methods for helix and coupled cavity traveling wave tube (TWT) in millimeter wave (MMW) are described. The interaction efficiency has been reached 14.56% by dynamic velocity taper in Ka-band TWT. Efficiency improvement has been carried out by used copper helix for broadband MMW TWT. Owing to a ferruleless coupled cavity TWT used phase-adjusted taper, the interaction efficiency has been increased from 9.6 to 22.6%. Finally, enhancing collector efficiency used multistage depressed collectors is discussed in the paper. These concept and technology of the approach are very useful for tube designer. 相似文献
14.
In order to improve the radiation characteristics of a backfire bifilar helical antenna, a means of terminating the arm ends with a resistor is numerically and experimentally investigated. Owing to the reduction of reflected current, the present backfire helix realises an excellent front-to-back ratio and axial ratio, while maintaining inherent absolute gain. 相似文献
15.
16.
Zhaoyun Duan Yubin Gong Yanyu Wei Wenxiang Wang Minzhi Huang 《International Journal of Electronics》2013,100(5):309-318
In order to enhance the power capability of the helix travelling wave tube, a novel tape helix slow wave structure (SWS), which is supported by helically arrayed radial dielectric-support posts, is developed. Each dielectric post can be easily brazed with the tape helix and the metal envelope by means of a special soldering. This kind of supporting mode can protect the dielectric supporting posts from being broken by the thermal stress in the case of high temperature. A hybrid model is set up in consideration of the influences of both the radial thickness of the tape helix and these discrete dielectric-support posts. The dispersion equation and interaction impedance of the helical SWS are obtained. The calculated results using this hybrid model presented in the paper show good agreements with the HFSS simulation results. All the results presented here can provide a good basis for designing the novel tape helix SWS. 相似文献
17.
The bifilar scanning helical antenna is analyzed by considering the structure to carry a single traveling wave. It is shown that the relative phase velocity (v/c) must equal unity to yield the scanning features shown by numerical experiment. This is at complete odds with monofilament helices (Kraus), which display a slow wave structure 相似文献
18.
An extensive study aiming at analyzing the effect of rod shapes and dimensions on the gain of helix traveling wave tubes (TWTs) is performed. The evaluation of tube small-signal gain is obtained by making use of a rigorous field analysis which takes into account the helix tape model and the dielectric inhomogeneous loading conditions. Computing time to perform the analysis is extremely low compared with the time required in the case of a full wave, three-dimensional (3-D) electromagnetic simulator. The accuracy of the simulation approach has been extensively verified in a previous paper. A novel expression for the attenuation constant has been introduced in the model to improve the quality of results. The proposed study allows a better understanding of tube behavior before fabrication highlighting the contribution of the shape, the mechanical tolerances and the ϵr variation of the rods to the small-signal gain 相似文献
19.
20.
Some aspects of circuit power dissipation in high power CW helix traveling-wave tubes, part I: General theory 总被引:2,自引:0,他引:2
《Electron Devices, IEEE Transactions on》1969,16(9):813-820
This paper describes the basic theory underlying calculations of the thermal behavior of helix-type slow wave circuits used in high power traveling-wave tubes. Typically, the helix is supported by means of three ceramic rods in a metal shell with the helix brazed to the rods. At the highest power levels the support rods are also brazed to the tube shell. The results of calculations on specific structures are presented which show the use of different support rod and helix materials, of beam interception, and of brazing the support rods to the shell. Of particular interest is the conclusion that the temperature difference between the hottest and coldest parts of the helix can be significantly larger than the temperature drop across the support rods when using high thermal conductivity ceramic materials brazed to the tube shell. 相似文献