Spark plasma antenna

The plasma of spark gaps that connect capacitors in the Marx circuit is studied as an element of a transmitting antenna. It is demonstrated that two closely located electrical circuits consisting of capacitors that are series-connected via spark gaps form a guiding structure allowing the propagation of electromagnetic waves and their emission into the ambient space.     

Physical principles of plasma antenna operation

Basic principles of operation of plasma antennas based on volume and surface plasma waves are presented. It is demonstrated that the efficiency of plasma antennas does not yield to that of metal antennas and that the controllability (frequency tuning for reception and transmission) and radar invisibility (a small radar cross section) are significantly higher. Plasma antennas of two types are considered: dipole antennas operating based on the surface plasma wave, and slotted waveguide antennas operating based on the volume plasma wave.     

Slot antenna impedance for plasma layers

The rectangular cavity or waveguide backed slot is covered by a plasma layer of finite thickness. The longitudinal variation of the voltage across the slot is obtained from the variational solution of an integral equation. The solution for plasma layer of finite thickness is obtained from the free space Green's function by the method of images. The fields outside the slot depend on the surface integral of the fields over the slot plane and over the surface of the plasma layer. If the thickness of the plasma layer is large compared with the wavelength, the fields on the surface of the plasma may be related to the voltage distribution along the slot by plane wave reflection coefficients. This leads to an integral equation that is reduced to a form suitable for machine computations. These calculations show the slot admittance to remain almost constant for plasma layers of various thicknessesh. The slot conductance tends to increase forh/ lambda <0.5. The presence of a plasma layer affects the voltage distribution along the slot for a center excited slot. The field distribution along the waveguide excited slot differs only slightly from the principal mode field distribution in the guide.     

A loop antenna in a compressible plasma

An analysis is made of the radiation of an electron plasma wave from a circular-loop antenna with an arbitrary dimension immersed in a compressible plasma. The radiation resistance due to plasma-wave radiation is calculated and is compared with that due to electromagnetic-wave radiation.     

等离子体天线的原理与设计

介绍了几种等离子体天线的工作原理，详细论述了单极表面波驱动等离子体天线的阻抗、效率及噪声情况，以及高压脉冲等离子体天线中等离子的产生及激励产生电磁波的过程。     

实用型等离子体天线的研制与测试

为了解决等离子天线增益低、噪声大、体积大、质量重、功耗高等问题.在天线增益取得突破性进展的基础上,通过重新设计天线激励源和各主要腔体等措施,研制了一款新型等离子体天线样机,该样机尺寸小、质量轻,并实现了低噪声和较低的功耗.在外场测试中,该样机达到与金属天线相近的增益水平.     

等离子体天线的噪声测量及分析

分析了利用等离子体天线代替金属天线时,射频系统通讯过程中噪声的来源、大小及其对系统的影响,并采用不同的测量方法通过无线电综合测量仪和频谱仪两种仪器得到等离子体天线馈端在HF/VHF不同频段的系统等效噪声温度.实验结果表明等离子体天线可以代替金属天线用于射频通讯.     

等离子体天线的基本特性仿真

等离子体天线具有隐身、动态重构等不同于金属天线的独特的物理性质,在卫星遥感、通信、导航领域具有潜在的应用前景。为了研究等离子体频率对天线特性的影响,采用三维电磁仿真软件建立了柱形等离子体天线模型,在此基础上,针对等离子体频率对等离子体天线的S11曲线、方向图、增益等性能的影响进行了仿真分析,并给出了相关结论。     

光生等离子体栅扫描天线研究进展

毫米波和太赫兹(THz)波天线扫描技术已经成为当前电磁领域研究的热点,光生等离子体栅(PIPG)扫描天线技术作为一种低成本的快速扫描技术为操控毫米波和THz波提供了新的方法和思路。本文将对PIPG扫描天线的原理、结构、效率和方向图等主要研究进展做详细的论述,并且对PIPG扫描天线的研究意义和存在的主要问题进行讨论和展望,希望对PIPG扫描天线的研究和应用提供参考。     

等离子智能天线阵列的特性研究

设计了一种等离子半波天线构成的智能天线阵列。通过仿真分析,当选择合适的等离子特征频率和碰撞频率时,等离子天线阵列和金属构成的天线阵列具有相似的辐射特性。但是当等离子体停止激发时,等离子天线阵列有着比金属天线阵列低的RCS值,从而具有隐身的性能。     

Current distribution on a cylindrical antenna in a plasma

A general solution for the current distribution on a cylinder in a cold magnetoplasma has been obtained. It is complicated, but for practical applications several simplifications occur. We present an outline of this solution and a sample of results.     

Measurement of antenna current distribution in an anisotropic plasma

The current distribution along a cylindrical antenna immersed in a magnetized plasma has been measured. It has been observed that the standing wavelength along the antenna wire is substantially shortened to a greater degree with increasing plasma frequency under the presence of the dc magnetic field. The gyroresonance has also been observed in the current distribution.     

Current distribution on a dipole antenna in a warm plasma

A cylindrical dipole antenna having finite dimensions, and surrounded by a homogeneous warm plasma, has been treated as a boundary-value problem. The current on the antenna has been determined and has been found to possess an oscillatory component, the fluctuations of which have approximately the wavelength of the surface wave on a corresponding infinite cylinder immersed in a warm plasma.     

Measurements of dipole antenna impedance in an isotropic laboratory plasma

The impedances of relatively long dipoles in an isotropic laboratory plasma have been measured at 9.2 GHz (Xband). A helium plasma was generated by discharging a capacitor between electrodes in a cylindrical container ten free-space wavelengths in diameter. Impedance measurements were made in the decaying afterglow plasma at electron densities both above and below the critical electron density (10^{12}cm^-3). The dipole antennas were fed from miniature solid-jacketed coaxial cables attached to a waveguide on which the voltage reflection coefficient was measured. The effect of plasma on the impedance of the dipole antenna was derived theoretically by treating the dipole as a dissipative transmission line. The theory described in a qualitative fashion the observed impedance variation with electron density for all the dipoles investigated. The measurements indicated certain antenna impedance properties, due to the plasma, which were not accounted for by the simple theory.     

Impedance of a short dipole antenna in a cold plasma

This paper presents the analysis of the impedance of a short dipole antenna in a cold plasma using a quasi-static approach. Two radically different current distributions on the antenna are considered and their influences on the antenna impedance are studied. These distributions include a one-dimensional (1-D) triangular distribution and a three-dimensional (3-D) exponential current distribution. Balmain (1964) analytically solved the first problem. Staras (1964) proposed the second one. In this paper, we offer an analytical solution for the second one as proposed by Staras. We compare both distributions and find that impedances resulting from them are remarkably close. We conclude that the impedance of a short antenna, as derived using the quasi-static approximation, is insensitive to the choice of current distribution. Therefore, any of these two theories can be used when analyzing data from an impedance probe immersed in a space plasma     

Resonantly h.f.-sustained plasma around an antenna

When sufficient h.f. power is fed to a plasma-coated antenna, the plasma becomes resonantly sustained. The superposition of the resonance patterns at frequencies ?, 2? and 3? is investigated, and it explains most of the observed facts.     

Radiation from a spherical aperature antenna immersed in a compressible plasma

The exterior boundary-value problem for a sphere immersed in a compressible plasma medium is solved. The model is a perfectly conducting sphere excited by an aperture, in its surface, which has a specified distribution of the tangential electric field. The configuration is such that Maxwell's equations, when combined with the continuum theory of fluid dynamics, are separable. The sheath at the interface with the plasma is characterized by an absorptive boundary condition which assumes a linear relationship between the pressure and the mean velocity of the electrons. It is shown that the TM (transverse magnetic) waves are coupled with the electroacoustic waves, while the TE (transverse electric) waves are decoupled. Some numerical results are presented which show, in quantitative manner, the relative fraction of the total power which is radiated in the form of electroacoustic waves.     

Radiation from a center-fed cylindrical antenna surrounded by a plasma sheath

The radiation field of a plasma-clad cylindrical antenna fed across an infinitesimal gap has been derived. The limitations on the validity of the far-field pattern have been stated. In the vicinity of the antenna, but in the region far from the gap, an expression is derived for the surface wave contribution which is the major source of field strength in this region. Analysis of the contour integration and discussion of the location of the various types of poles of the integrand on their appropriate Riemann sheets are presented. Numerical computations of far-field patterns and surface wave fields are presented graphically.