Mode orthogonality in chirowaveguides

The orthogonality relations for modes supported by a general cylindrical chirowaveguide are derived. These waveguiding structures are cylindrical waveguides containing chiral materials. It is pointed out that one of these relations is valid for lossless waveguides, whereas the other holds for the lossy as well as the lossless case. It is demonstrated that the orthogonality relations can be used to express an arbitrary electric or magnetic field within a chirowaveguide in terms of the mode functions. As in conventional waveguides, the orthogonality relations reported can be used to expand an arbitrary E or H field within a chirowaveguide in terms of a complete set of mutually orthogonal modes in the waveguide     

Propagation analysis of chirowaveguides using the finite-elementmethod

Propagation analysis of chirowaveguides, i.e. waveguides including chiral media, are calculated using a generalization of the full vector finite-element formulation in terms of the electric and magnetic fields. The formulation permits numerous inhomogeneous waveguide structures of arbitrary linear composition, including chiral media, to be analyzed without any nonphysical, spurious modes. In the proposed formulation both the necessary conditions on the tangential field components and the additional conditions on the normal field components are automatically satisfied by the trial functions. In this way the dimension of the resulting sparse generalized eigenvalue problem is significantly reduced. The straightforward extension to the novel class of chirowaveguides, which exhibit a number of interesting new features, demonstrates the versatility of the formulation. The advantageous numerical properties are thus preserved. Numerical examples on both metal and dielectric chirowaveguides are given. The finite-element results are compared with exact solutions, and the correspondence is found to be excellent     

Guided modes on open chirowaveguides

Surface wave modes on an open chiral rod and a planar chiral slab are studied. It is shown that the effect of chirality is to split each mode in the nonchiral case to a pair of modes, the cutoff frequencies of which are above and below that of the nonchiral case. The mode with the lower cutoff frequency is dominantly right circularly polarized (RCP) mode while the mode with the higher cutoff frequency is dominantly left circularly polarized (LCP) mode near their respective cutoff frequencies. At sufficiently higher frequencies, all modes tend to become RCP (assuming a right handed chiral medium). Closed form expressions for modal cutoff frequencies on the planar chiral slab and chiral circular rod are derived. The surface wave modes are classified as HE and EH modes and a suitable definition for these mode types, that reduces to well known definitions in the nonchiral case, is proposed     

THE COMBINED EFFECTS OF GYROTROPY AND CHIRALITY IN CIRCULAR FARADAY CHIROWAVEGUIDES

Based on the method of separating variables and the technique of Muller's calculating roots, the propagation characteristics of hybrid modes in homogeneous and inhomogeneous circular Faraday chirowaveguides are examined in detail. Numerical results are presented to demonstrate the combined effects of different constitutive parameters on the mode bifurcation, symmetry and nonreciprocity, backward-wave and attenuation of hybrid modes, which are different from the cases of ordinary gyrotropic and reciprocal chiral waveguides.     

Guided electromagnetic waves in gyrotropic chirowaveguides

The propagation characteristics of hybrid modes in the circular cylindrical and coaxial line gyrotropic chirowaveguides are studied using the technique of separation variables. First, the transverse components of electric and magnetic fields are expressed in terms of the longitudinal components of E and H¯. Then, numerical results are presented for the dispersion behavior and cut-off frequencies as well as the field distributions of hybrid EH_0,1 and HE_n,1, with the effects of different electromagnetic parameters of gyrotropic chiral material taken into consideration. It is shown that the process of mode bifurcation also takes place in the gyrotropic chirowaveguides; this is similar to the cases of reciprocal chirowaveguides. But, gyrotropic chirowaveguides are nonreciprocal bianisotropic devices     

Mode orthogonality relations and field structure in chirowaveguides

By analyzing the vector and scalar equations for chirowaveguides, two forms of mode orthogonality relations are obtained: the vector formulated orthogonality and the scalar formulated orthogonality. The first one is applicable to the general case of open chiroplasma or chiroferrite waveguides. It is shown that for two parallel-plate isotropic chirowaveguides, these two forms of orthogonality relations differ. Based on mode orthogonality relations, it is shown that in chirowaveguides the polarization of so-called complex modes differs from that of propagating or evanescent modes. The correlation between field components of two complex modes that transfer active power flow in chirowaveguides is obtained     

A comprehensive study of discontinuities in chirowaveguides

We provide a comprehensive study of two- and three-dimensional discontinuities in chirowaveguides. The multimode coupled-mode method is an effective numerical approach to analyze this problem. After obtaining the coupled-mode equations, we diagonalize the coupling matrix to obtain a multimode scattering matrix rather than the usual two-mode approximation. We calculate the scattering properties of coaxial waveguides partially filled with lossy chiral media. Excellent agreement is observed between our results and those obtained by the mode-matching method. We also compare our results in the achiral case for dielectric material partially filled rectangular waveguide with experimental data and results obtained by the mode-matching method. Excellent agreement is again found. Based on our analysis, numerical and analytical results are displayed to provide physical insight into the problem. First, we discuss the effects of the chirality admittance on scattering properties and find that the sensitivity of the scattering parameters to chirality admittance increases as the chirality admittance increases. Second, we find the dielectric constant has a great influence on the scattering parameters. Third, we find the relative influence of height and width of chiral obstacles in rectangular waveguides.     

A new radial transmission line network approach for symmetrical modes in circular chirowaveguides

In this paper, the dispersion characteristics of symmetrical modes in circular chirowaveguides are analyzed by a new equivalent transmission line network method. Radial transmission lines in the transverse cross section are introduced. In the transmission line network, the right-circularly polarized (RCP) wave and the left-circularly polarized (LCP) wave can propagate independently in the uniform regions and couple only at the interface. Therefore, this method brings a clear physical picture into the wave propagation phenomena. Based on the analysis, two interesting effects due to mode coupling and leakage are carefully studied.     

On two different formulations of the Coupled Mode Method: Application to 3D rectangular chirowaveguides

This paper develops two different formulations of the Coupled Mode Method (CMM), called EH-indirect and EH-direct formulations, for rectangular waveguides nonhomogeneously loaded with bi-isotropic media. The results of the EH-indirect formulation are compared with the more usual EH-direct formulation, and its range of applicability is established. When the EH-indirect or EH-direct formulations of the CMM are combined with the classical Mode Matching Method (MMM) a hybrid technique is obtained that is capable of solving three-dimensional (3D) discontinuities without restriction in number. The results of the generalized scattering matrix for the two formulations are compared and it is concluded that the indirect formulation gives more accurate results than the direct formulation.     

The interactions between ergodic theory and information theory

Information theorists frequently use the ergodic theorem; likewise entropy concepts are often used in information theory. Recently, the two subjects have become partially intertwined as deeper results from each discipline find use in the other. A brief history of this interaction is presented in this paper, together with a more detailed look at three areas of connection, namely, recurrence theory, blowing-up bounds, and direct sample-path methods     

The theory of bandpass sampling

The sampling of bandpass signals is discussed with respect to band position, noise considerations, and parameter sensitivity. For first-order sampling, the acceptable and unacceptable sample rates are presented, with specific discussion of the practical rates which are nonminimum. It is shown that the minimum sampling rate is pathological in that any imperfection in the implementation will cause aliasing. In applying bandpass sampling to relocate signals to a base-band position, the signal-to-noise ratio is not preserved owing to the out-of-band noise being aliased. The degradation in signal-to-noise ratio is quantified in terms of the position of the bandpass signal. For the construction of a bandpass signal from second-order samples, the cost of implementing the interpolant (dynamic range and length) depends on Kohlenberg's sampling factor (1953) k, the relative delay between the uniform sampling streams. An elaboration on the disallowed discrete values of k shows that some allowed values are better than others for implementation     

关于超辐射的经典理论

综述了超辐射的经典理论。从原子的阻尼振子模型和光波波动方程出发，求出了超辐射脉冲的表达式，并讨论了超辐射的寿命、最短寿命、辐射强度、方向性和激励脉冲。     

The theory of broadside arrays

The general King-Sandler array theory has been examined in detail for the case of broadside arrays. Since it is not necessary to assume identical current distributions on every element in the array, a distinction is made between specified base currents and voltages. The driving-point impedances for specified base currents and voltages are presented for arrays of up to 25 elements. The effect of interaction between the element currents in the base impedances and radiation patterns is clearly shown for the broadside array. The results indicate that the major effect of unequal current distributions in the broadside array is to cause important variations in the driving-point impedances and little effect in the radiation patterns.     

The theory of endfire arrays

The general King-Sandler array theory has been examined in detail for the case of endfire arrays. Since it is not necessary to assume identical current distributions, a distinction is made between specification of the base voltages and currents. The driving-point impedances for specified base voltages and currents are presented for arrays of up to 25 elements. The effect of interaction between the element currents in distorting the radiation pattern is shown for the 15-element endfire array. The results indicate that the unequal current distributions have a pronounced effect in determining the driving-point impedances, sidelobe levels and back-to-front ratios of endfire arrays.     

The physical theory of slope diffraction

The physical theory of diffraction (PTD) has been expanded for the case of slope diffraction, when an incident wave is zero but its derivative is not zero in the direction of a perfectly conducting scattering edge. High frequency asymptotics are found both for elementary edge waves and for the total edge waves scattered by arbitrary curved edges. Great attention is given to fields created by the nonuniform (diffraction) component of edge currents. These fields are usually called ptd corrections to the Physical Optics approach. These corrections are found for diffraction fields in ray regions and in diffraction regions such as the vicinities of shadow boundaries, smooth caustics, and foci.     

有属性的散射中心理论及应用

讨论了基于物理光学和几何绕射理论的散射中心模型，对有属性的散射中心理论进行了详细的介绍推导，并对散射中心模型的各个参数在图像城进行了估计。结果验证了参数估计方法的有效性和散射中心理论模型的实用性。     

The theory of twisted transverse-wave couplers

The coupled-mode theory of a class of transverse-wave couplers in which the plane of polarization of the electric field rotates along the length of the coupler is described. The synchronism conditions between the circuit wave and the beam that lead to strong interaction with one or more of the transverse beam waves are given and the case of equal interaction with the two cyclotron waves is discussed in detail. It is observed that any two transverse waves of opposite polarization can be excited equally in a twisted coupler, or that coupling to one of two waves with the same phase velocity but opposite polarizations can be achieved.     

The theory of the long-channel MOSFET

The most rigorous model of a long channel MOSFET is that of Pao and Sah; it incorporates contributions to the drain current from diffusion as well as drift and from both the weakly and strongly inverted sections of the channel. Its principal drawback with regard to circuit applications is the necessity for evaluating numerically a two variable integral. Brews has replaced this complicated expression with an analytical formula based on several approximations, one of which is that the channel can be regarded as a very thin layer containing a negligable amount of charge. We show in this paper that the Brews charged-sheet and Pao-Sah exact models predict identical current-voltage characteristics (to within a fraction of a per cent) and we give the analytic and numerical reasons for this agreement. Comparisons are made with experimental curves, the physical basis for the approximations is examined, and we consider extensions of the charged-sheet model.