共查询到20条相似文献,搜索用时 15 毫秒
1.
I. B. Esipov O. E. Popov G. V. Kenigsberger I. I. Sizov 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(10):1209-1217
This work considers the capabilities of a hydroacoustic antenna based on principles of nonlinear acoustics to perform hydrophysical studies on long-distance paths. The antenna is described and results from initial experiments at sea are reported. The antenna is installed at a depth of 40 m at the site of investigations by the Hydrophysical Institute, Abkhazia Academy of Sciences. At a pumping frequency of 20 kHz, it allows the medium to be probed in the 300–3000 Hz range of parametric radiation on long-distance routes. The sharp directional pattern (2° angular resolution) of the broadband parametric radiation ensures single-mode excitation of the marine waveguide throughout the frequency band. Generation of a specific signal by a parametric antenna provides conditions for using the frequency dispersion of the velocity of acoustic signal propagation in the marine waveguide to compress the signal as it travels along a long-distance path. 相似文献
2.
利用机械调节波导宽边尺寸可变化波导波长,从而实现变频波束扫描相同的效果,针对窄边辐射波导行波阵的波束扫描特性进行了分析,以实现宽角波束扫描为目标,着重分析了不同辐射缝隙间距下变化宽边所能得到的最大波束扫描范围。设计了通过变化宽边尺寸实现宽角扫描的X波段窄边辐射波导缝隙阵,设计波束扫描范围指向波导馈入端,避开阵列法向辐射(此方向辐射效率较低),实现了29°的连续波束扫描范围,在波束扫描范畴内增益下降小于3 dB,辐射效率大于62%;设计缝隙宽度3 mm, 波导长度约1 m(缝隙数40),单根波导缝隙天线可实现高功率微波功率容量70 MW。 相似文献
3.
Brian G. Ruth Christian D. R. Schlesiger Robert K. Dahlstrom 《International Journal of Infrared and Millimeter Waves》1989,10(7):869-878
This paper addresses the radiation patterns launched from circular waveguide radiators as the first step in the design of a Vlasov-type mode convertor that will function at high power levels in the X-band frequency range (8 to 12 GHz). The radiating ends of the radiators are each cut at a specific angle relative to the center axis of the waveguide to form the waveguide launcher component of a Vlasov-type mode convertor. The far-field radiation patterns for three radiators were measured with an antenna pattern-mapping system.ATTN: SLCHD-NW-RS 相似文献
4.
E. A. Gevorkyan 《Optics and Spectroscopy》2017,122(2):276-281
We have considered transient radiation of a charged particle in an anisotropic magnetodielectric plate placed into a regular waveguide. It is assumed that the charged particle passes through the plate moving at a constant velocity perpendicularly to the waveguide axis. Wave equations and analytical expressions for transverse electric (TE) and transverse magnetic (TM) fields in different regions of the waveguide have been obtained. Energies of transient radiation of the moving particle have been calculated. The properties of transient radiation and Vavilov–Cherenkov radiation have been analyzed for the case of a rectangular waveguide. Energies of transient radiation have been calculated for the case of a “thin” plate in the waveguide, when the wavelength in the plate is much greater than the length of the plate. 相似文献
5.
The possibilities of using the decomposition of natural waveguide modes in a shallow-water sea in case there is a sound velocity
gradient into sinusoidal modes of an ideal waveguide is grounded. The applicability range of such decomposition is shown.
Dispersion in signals of the modes presented in such a way is determined by mathematical reversal without a test source. The
structure of discrete modes in a natural waveguide is determined without utilizing the bottom parameters and sound velocity’s
distribution over the waveguide depth. The coefficient of the mode signal’s correlation with the measured parameters of the
mode signal and a real signal, introduced into it, is shown to be 0.973. The signals from a point emitter positioned at the
depth of 50 m in the frequency range of 90–280 Hz in a shallow-water sea (the Barents Sea, a 120 m depth, a 7 km distance),
received by a vertical antenna array comprising 32 receivers spaced equidistantly with a 3-m step are used in the experiment.
A real signal has been successfully reversed using a mathematical model. 相似文献
6.
Heikkinen J.A. Irzak M.A. Shcherbinin O.N. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(1):26-35
The radiation spectra of a dielectric-filled waveguide (DWG) and a folded waveguide (FWG) antenna in the ion cyclotron range of frequencies are evaluated for tokamaks with the waveguide codes, which model the coupling of the waveguide modes to the plasma waves with outward radiating boundary conditions. The codes provide a self-consistent calculation of the fields across the waveguide apertures for various antenna phasings taking into account a complete set of waveguide eigenmodes including the reflected modes and, in the case of DWG, an arbitrary orientation of the antenna to the plasma magnetic field. In the studied cases, the spectra are found to be well described by a model which is based on a simplified wave field pattern determined by the antenna aperture geometry. Comparison to the corresponding loop antenna is carried out 相似文献
7.
V. M. Kudryashov 《Acoustical Physics》2000,46(5):580-587
An antenna array placed in an arctic-type acoustic waveguide is considered. The guided sound field consists of a signal generated by a point source and an isotropic interfering noise produced by the ice cover. The array is operated in a specific regime: the output signals correspond to individual modes of the sound field. The signal received by the array is subjected to correlation processing with a finite averaging time. It is shown that, depending on the processing method, the signal-to-noise ratio can reach 40–60 dB for a realization duration of 1 min, and the quality of the signal detection is increased. 相似文献
8.
介绍了一种低成本高效率的W波段4×4基片集成波导(SIW)缝隙阵天线。天线阵为双层结构,上层为辐射层,采用宽边纵向偏移缝隙驻波阵,可以实现高的辐射功率,下层为馈电层,采用SIW串联缝隙馈电方式,减小了传统功分网络带来的传输损耗和实现难度。对天线阵进行了优化设计,采用标准低成本PCB工艺制作了天线阵实物样品并进行测试。测试结果与仿真结果吻合较好,天线阵在94 GHz时,最大增益为16.8 dB,反射系数-30.1 dB,-10 dB带宽为92.6~96 GHz,副瓣电平19.5 dB,天线阵口径效率为83%。 相似文献
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The results of calculations performed in the framework of the approximate approach developed by the authors are presented for the diffraction of sound waves by a stiff spheroid in an acoustic waveguide. The scattered sound field is analyzed as a function of the following parameters of the problem: the spheroid dimensions, its position relative to the sound source and the receiver, the vertical profile of sound velocity in the waveguide, and the acoustic parameters of the waveguide bottom. 相似文献
13.
A. V. Serov 《Journal of Experimental and Theoretical Physics》2005,101(2):224-229
A scheme of a generator of electromagnetic-wave radiation is proposed in which a radiating region moves along a radiator with a velocity greater than the velocity of light in vacuum. The superlight motion of the generating region leads to the situation in which the resulting radiation has the properties of Vavilov-Cherenkov radiation. The electron beam of a superlight source is formed while the particles travel across a waveguide along which an electromagnetic wave propagates. The construction of the generator makes it possible to vary the velocity of the radiating region, the radiation pattern, and the radiation beamwidth. Calculations are performed that allow one to evaluate the parameters of the generator and the characteristics of radiation. 相似文献
14.
Yu. I. Papkova 《Acoustical Physics》2017,63(1):54-62
An analytic representation is constructed for a nonaxially symmetric sound field to simulate a hydroacoustic waveguide the bottom of which is hard and has an axially symmetric relief. A numerical analytic method for finding the velocity potential is proposed, for which undetermined coefficients for normal modes are determined from a corresponding infinite system of algebraic equations. The sound fields are studied with for variations of the problem parameters. 相似文献
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扇形波导可作为高功率微波圆柱共形波导缝隙阵天线的基本单元。分析了扇形波导中主模场分量,根据实际情况对主模场进行了合理近似。采用互易定理推导由波导主模横向场分量和缝隙场分量表示的波导场分量的前向或后向散射系数。根据波导传输线理论,将波导宽边纵缝等效为并联导纳,再根据波导边界条件得到扇形波导宽边谐振纵缝的归一化电导与波导散射系数之间的关系式。根据缝隙天线与振子天线的互补关系得到扇形波导谐振缝隙的辐射阻抗,结合波导功率平衡关系得到由波导横向场散射系数表示的缝隙辐射功率表达式,得到归一化电导的与谐振宽边纵缝的偏移位置、缝隙宽度、波导波长以及扇形波导尺寸参数之间的解析表达式。给出了算例,在波导中间区域,通过商用软件计算得到的电导与理论公式结果基本吻合。 相似文献
17.
Davies J.A. Davidson R.C. Johnston G.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(3):286-300
A linear analysis is presented for pulse shapes produced by a spatial and temporal delta-function disturbance of cyclotron-resonance-maser modes for the case where the initial equilibrium state is free of radiation. A pinch-point analysis based on the theory of R.J. Briggs (1964) and A. Bers (1983) is employed. Numerical and analytical techniques are developed for the straightforward calculation of pinch-point coordinates in a reference frame moving with arbitrary velocity in the axial direction. Examples analyzed include the absolute instability in the waveguide operating mode, in higher harmonics of the operating mode, and in lower-frequency waveguide modes when the operating mode is a higher-order waveguide mode. Effects of waveguide wall resistance on pulse shapes and the effectiveness of such resistance in suppressing or reducing the growth rates of absolute instabilities are also analyzed 相似文献
18.
G. L. Komissarova 《Acoustical Physics》2009,55(3):319-328
The properties of harmonic surface waves in an elastic cylinder filled with a liquid are studied. The case of elastic material for which the shear wave velocity is higher than the sound velocity in a liquid is considered. The wave motion is described based on the complete system of equations of the dynamic theory of elasticity and the equation of motion of an ideal compressible liquid. The asymptotic analysis of the dispersion equation in the region of large wave numbers and qualitative analysis of the dispersion spectrum showed that in such a waveguiding system there exist two surface waves, the Stoneley and the Rayleigh waves. The lowest normal wave forms the Stoneley wave on the internal surface of the cylinder. In this waveguide phase, velocities of all normal waves, except for the lowest one, have the velocity of sound in the liquid as their limit. Therefore, the Rayleigh wave on the external surface of the cylinder is formed by all normal waves in the range of frequencies and wave numbers in which phase velocities of normal waves of the composite waveguide and the lowest normal wave of the elastic hollow cylinder coincide. 相似文献
19.
A model problem of seismic hydroacoustics is studied for a piston radiator inserted in an impedance screen that coincides with the lower boundary of a Pekeris waveguide. The radiation resistance of the piston is numerically calculated as a function of the screen type and parameters of the radiator and the waveguide. 相似文献