Enhancing the natural frequency doublet splitting in almostperiodic azimuthally corrugated cavities

A symmetry of a corrugated periodic structure can be broken due to loading or/and fabrication defects so that frequency doublets may appear, whose frequencies are just slightly splitted. In this letter, we study the potentials to enhance this splitting by enhancing the asymmetry of the cavity. This is provided by a single (loaded) resonator which differs in its geometry from other resonators. The initial causes of the asymmetry are not taken into account. The used characteristic matrix equation is obtained by a mode-matching technique. It is shown that the doublet splitting can reach several percent due to a convenient choice of the geometry of the loaded resonator     

ANALYSIS OF N-SLOT STRUCTURE CORRUGATED HORN

On the space harmonics technique general formulas are derived of the characteristicequation and the equivalent wall admittance of corrugated horns with N-slot structure(each periodhas N slots whose shape and depth may be the same or different).As an example,the calculatedradiation patterns for a corrugated horn having dual-depth corrugations show good agreementwith the measured ones.     

Analysis ofN-slot structure corrugated horn

On the space harmonics technique general formulas are derived of the characteristic equation and the equivalent wall admittance of corrugated horns withN-slot structure(each period hasN slots whose shape and depth may be the same or different). As an example, the calculated radiation patterns for a corrugated horn having dual-depth corrugations show good agreement with the measured ones.     

N槽结构波纹喇叭的理论分析

本文利用空间谐波法导出了N槽结构(每个周期有N个槽)波纹喇叭的特征方程和等效壁导纳的普遍公式,并把这些公式应用于双槽深波纹喇叭,给出了其等效壁导纳的表达式。文章还对一个双槽深波纹喇叭的等效壁导纳、特征值、口面模比和辐射方向图进行了数值计算,并与实验结果比较,两者吻合得很好。     

Hybrid modes in corrugated conical horns with narrow flare angle and arbitrary length

By comparing the modified field equations of a corrugated conical horn of narrow flare angle (and arbitrary length) with those of a corrugated cylindrical waveguide, a technique to solve the characteristic equation of the horn is developed. It is also shown that the expressions for the far-field radiation pattern of the waveguide are applicable to the horn, except that the propagation constants must be modified.     

The Characteristic Equation of Corrugated Square Groove Waveguides

When the periodic spacing of corrugated wavesguides is much less than wavelength λ, the slot width d≈L, and the space harmonics are neglected, the characteristic equation of corrugated square groove waveguides is formulated based on Maxwell's equations and boundary conditions.     

The Characteristic Equation of Corrugated Circular Groove Guide

Using the mode matching technique and neglecting the space harmonics, the characteristic equation of corrugated circular groove guide is given.     

Determination of the roots of the characteristic equation forcorrugated and dielectric loaded circular waveguides

An algorithm is developed for the numerical determination of the roots of the characteristic equation for corrugated and dielectric loaded circular waveguides. The algorithm, based on geometrical properties of the characteristic equation and on the identification of the interval of existence of each root, assures a fast and precise determination of all the roots, real or complex, in a given interval     

Compact dual-profile corrugated circular waveguide horn

A new type of corrugated horn is presented. It is designed to have a dual-profile corrugation, yielding a more compact structure with respect to standard linear or sinusoidal profiled horns. It is also shown that the new design has some interesting features in terms of the phase centre location and its level of variation over the operating bandwidth     

High-Q resonances due to surface waves and their effects on theperformances of corrugated horns

We present a study of high-Q resonance phenomena that occur in corrugated horn structures. It is found that high-Q resonances occur within certain frequency bands where two types of modes, i.e., space-wave and surface-wave modes, simultaneously propagate. A simple model is presented to explain the resonance mechanism. The model yields the conditions for resonance, explains the Q of the resonance, and provides the associated resonant frequency. Approximate formulas for the upper and lower bound frequencies of a resonant band are obtained. It is found that the high-Q resonances deteriorate the gain and crosspolar performances of a horn even if the return losses are acceptable at some resonant frequencies. Rectangular corrugated horns are more susceptible to these resonances than circular corrugated horns, and the reasons for such a difference are explained     

基于小波熵技术的波纹管压浆质量无损检测

提出了一种基于小波熵的波纹管超声无损检测方法,通过对回波信号进行小波熵技术处理和对熵值的不同来判断波纹管压浆相对密实程度。利用有限元进行了理论模拟仿真,研究了声场,通过仿真数据进行熵分析,结果表明,缺陷处的小波熵值较小,且缺陷越大熵值越小。通过实际制作模型并测量,得到了与仿真一致的结果。     

Characteristic equation and properties of electron waves in periodic structures

The finite-difference theory of excitation of periodic waveguides is used to derive the characteristic equation for electron waves formed during interaction of an electron beam with forward and counter-propagating electromagnetic waves of periodic waveguides (slow-wave structures). The derived characteristic equation describes interaction of electrons and waves in passbands and stopbands of periodic waveguides and contains known solutions for ??smooth?? slow-wave structures and resonator slow-wave structures near cutoff frequencies as particular cases. Several analytical solutions allowing comparison of amplification and propagation properties of electron waves inside and at the edges of passbands and stopbands of periodic waveguides are found.     

三站时差定位模糊问题解决方法

三站时差定位系统对辐射源进行定位过程中会出现定位模糊及无解的情况,通过对模糊无解特征的研究,发现了长期对时差定位模糊无解认识存在的误区.基于模糊无解的特征,提出了模糊问题的解决方法.仿真结果表明,不需增加系统复杂性,即可有效的解决定位模糊问题.     

Analysis of the instability in relativistic traveling wave tube

The relativistic traveling wave tube is an important high power microwave source. The corrugated cylindrical waveguide is usually used as slow wave structure of this device. Starting from wave equation and using boundary conditions, dispersion relation is derived for the corrugated waveguide, in which an intense relativistic electron beam propagates along the axis. Two cases which are shorter period and longer period are discussed in this paper respectively. The small signal gain of the relativistic traveling wave tube is analyzed and some conclusions are drawn. The analysis method presented in this paper can be extended to other types of slow wave structures of relativistic traveling wave tube.     

Compound-taper feed horn for NASA 70-m antennas

A compound taper feed horn structure is described that was used to move the phase center of a corrugated feed horn without any significant degradation in its other major characteristics. Based on this technique, an X-band feed horn has been designed for use in the National Aeronautics and Space Administration's (NASA) 70-m antennas. The compound taper structure consists of a conventional corrugated flared section (a standard 22-dB feed horn) and a corrugated straight section. This feed horn is designed to move the phase center of the standard feed horn to a desired location without the addition of significant loss to the system. The feed horn was checked extensively by a computer program. Excellent agreement between theoretical and measured results was established, and the feed horn was shown to perform as well as the standard feed horn for all practical purposes     

基于行波法对螺旋波纹波导色散特性的仿真

为研究螺旋波纹波导的色散曲线特性,利用阻抗微扰法对螺旋波纹波导色散方程进行求解,并分析了波导尺寸的变化对色散特性的影响。针对目前采用谐振法仿真色散曲线时存在模式分割以及谐振点的选取问题,利用行波法(不属于波纹波导理论体系下的新方法)对不同频率下的色散值进行仿真求解。研究结果表明,基于行波法仿真得到的色散曲线与由Matlab计算得到的理论色散曲线吻合度好,计算过程不涉及波纹波导理论体系下谐振点的选取问题,相比传统的谐振法,整个仿真计算过程更简洁。     

The strip-loaded hybrid-mode feed horn

A novel typed of hybrid-mode feed horn is presented. It comprises a hollow conical dielectric waveguide whose outer surface is metallized, and whose inner surface is coated with circumferentially oriented conducting strips. It may be designed to have mimimal cross polarization at two arbitrarily separated frequencies, as for a dual depth corrugated horn. Compared to the corrugated horn, it has the potential of lower weight and lower price. Small horns will have some cross polarization due to undesired radiation from the fields transmitted within the dielectric.     

低损耗波纹波导的传输特性

为了降低太赫兹波传输的损耗,研究了波纹波导中传输太赫兹波时的损耗特性,得到波纹波导的衰减常数的理论计算公式,在数值计算基础上设计了220 GHz低损耗波纹波导,并通过电磁仿真对数值计算结果进行验证,HE11模式实现了仿真与理论结果的相互吻合。     

Broadbanding of corrugated conical horns by means of the ring-loaded corrugated waveguide structure

Broadbanding of corrugated conical horns is investigated with the ring-loaded corrugated circular waveguide (RCWG) structure devised by the authors. The useful frequency bandwidth in which the corrugated horn is effective for the improvement of antenna properties is limited by the frequency characteristics of the horn-aperture field and input VSWR of the horn. By the precise analysis of the RCWG, the maximum frequency range in which the desirable field is obtained is much wider than that in the conventional corrugated circular waveguide, and is achieved almost independent of ring thickness, when ring width is about 20 percent of slot depth. The characteristic impedance of the RCWG is nearly equal to that of the homogeneous circular waveguide when ring thickness becomes large. Therefore, a good transformer between the RCWG and the homogeneous circular waveguide is achieved by increasing ring thickness from the RCWG toward the homogeneous waveguide. From the above investigations, it is found that in the ring-loaded corrugated horn, the useful bandwidth is 1.35 times broader than that in the conventional corrugated horn. The theoretical results are verified by the experimental results.     

Spectral domain analysis of a coupled slot antenna

The characteristics of a coupled slot resonator suitable for novel design of an integrated planar antenna are analyzed. The analysis is based on the spectral domain immittance matrix approach, and all the wave phenomena associated with the structure are incorporated. The resonant frequencies in the even and odd resonance modes are evaluated from the numerical solution of the characteristic equation, and the radiation patterns are calculated. The numerical results are compared with experimental data with good agreement