Shielded suspended dielectric guide

The dispersion characteristics of a shielded suspended dielectric are computed using mode matching technique. From the dispersion characteristics the dielectric and conductor loss, quality factor and wave impedances are derived. The dimensions of shielded suspended dielectric are same as that of a rectangular metallic wave guide at K_a band.     

Nonlinear pulse propagation in a monomode dielectric guide

We derive the nonlinear wave equation for an envelope of an electromagnetic wave in a monomode dielectric waveguide. Concrete examples are given for a single-mode optical fiber where the coefficients of resultant nonlinear Schrödinger equation with higher-order dispersion and dissipation (both linear and nonlinear) are given in terms of properties of the eigenfunction of the guided wave as well as of the material nonlinearity and dispersion. Using a newly-developed perturbation method, we show that the higher-order dispersions (linear and nonlinear) perserve the profile of a single soliton but to split up a boundNsoliton (N geq 2) into individual solitons with different heights which propagate at different velocities. We also show that the higher-order nonlinear dissipation due to the induced Raman effect downshifts the carrier frequency of a single soliton in proportion to the distance of propagation and to the fourth power of the soliton amplitude.     

Analysis of coupled inset dielectric guide structure

The propagation and coupling characteristics of the inset dielectric guide coupler are theoretically considered in this paper. Rigorous solutions for the dispersion relation and the coupling coefficient are presented in a rapidly convergent series. Numerical computations illustrate the behaviors of dispersion, coupling, and field distribution in terms of frequency and coupler geometry     

Non-radiative de-excitation of deep centres

We develop a quantitative theory of the ratio R of radiative to non-radiative de-excitation based on the Dexter-Klick-Russell criterion for the occurrence of luminescence. The model invokes three essential elements: a promoting mode, an accepting mode, and a set of lattice modes which ultimately absorb the vibrational energy. The ratio R is determined by the relative population of the relaxed excited and ground states. We show that Rn_x^(a)/n_g(a), where n_x^(a) and n_g^(a) are the numbers of vibrational quanta in the accepting mode associated with the excited state and the ground state, respectively, at the crossing of their adiabatic potential energy curves. The result is consistent with experiment.     

On the resonant scattering at guide dielectric windows

The effect of output wave resonant scattering at vacuum window of a microwave device caused by high-quality dielectric window eigenmodes excitation is studied. These negative resonant effects can seriously influence the device operation. The numerical calculation results are confirmed by a model experiment.     

Very wideband operation of twin-layer inset dielectric guide

An inset dielectric guide (IDG) with a multilayer dielectric filling is studied, using the transverse resonance diffraction, technique. The convergence and numeric efficiency of the analysis are good, and comparisons with experimental measurements of phase constant show the validity of the data produced. Those aspects of the IDG structure that limit its monomode bandwidth when it is filled with a single dielectric are investigated. It is shown how the monomode bandwidth of such an IDG may be made greater than that of rectangular metal waveguide by appropriate choice of aspect ratio. It is also shown how the simple use of two dielectric layers in the IDG slot can yield a guide whose monomode bandwidth is 66%, which is much greater than the typical operating bandwidth of a standard double ridge waveguide (40%). In the maximum bandwidth configuration, variation in the position of the boundary between the dielectrics produces little change in bandwidth. Hence, it appears that multilayer IDG is an attractive transmission media for wideband applications at both microwave and millimeter-wave frequencies     

一种基于插入介质波导的新型滤波结构

提出一种基于插入介质波导的新型滤波结构.采用微带线对插入介质波导进行馈电,使馈电结构更加易于实现.在插入介质波导中引入U形不连续结构,并通过人工神经网络模型算法提取相应的等效集总电路参数,从而实现带通滤波器的设计.最后,设计并实际加工了一款带通滤波器的测试样品.实测结果与设计要求基本吻合,说明了该新型滤波结构是可行的.     

Strip dielectric wave guide antenna-for the measurement of dielectric constant of low-loss materials

The value of dielectric constant are the most important parameters in material science technology. In micro-wave and millimeter wave circuits using dielectric materials the values of this parameters should be known accurately. It is observed that the number of methods are reported in litrature, however these methods impose difficulties in experimentation and are not very accurate. In this paper a novel approach to the measurement of the dielectric constant of low loss materials at micro-wave and millimeter wave frequencies has been discussed. In this method by using antenna theory, a metallic strip dielectric guide is taken in to constideration and band reject phenomenon of dielectric antenna is used. Frequency response of an antenna in band reject mode is a function of the dimensional parameters, such as the metallic strip period, the profile of the metallic strip and the dielectric constant of the material used. Hence if one measure the frequency responce of the antenna in band reject mode, the dielectric constant of the material is determined provided all other parameters are known. This method gives a direct measure of dielectric constant and is quite accurate as computer techniques are used for evaluating the dielectric constant. This method verified experimentally also.     

Non-radiative recombination losses in polymer light-emitting diodes

We present a quantitative analysis of the loss of electroluminescence in light-emitting diodes (LEDs) based on poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylenevinylene] (MEH-PPV) due to the combination of non-radiative trap-assisted recombination and exciton quenching at the metallic cathode. It is demonstrated that for an MEH-PPV LED the biggest efficiency loss, up to 45%, arises from extrinsic non-radiative recombination via electron traps. The loss caused by exciton quenching at the cathode proves only to be significant for devices thinner than 100 nm. Removal of electron traps by purification is expected to enhance the efficiency of polymer LEDs by more than a factor of two.     

Variation of wave impedance of shielded suspended dielectric guide

A shielded suspended dielectric guide is a dielectric rectangular slab enclosed by regular metallic side walls from all the sides. This type of structure is used in dual mode phase shifter where the size of the normal rectangular wave guide is reduced at the ends, where a dielectric material is embeded in ferrite core. Hence impedance variation of a phase shifter at its transition may be easily calculated using shielded suspended dielectric guide which is a prime parameter for optimum efficiency of wave launching.     

Wave propagation through a hollow rectangular anisotropic dielectric guide

Wave propagation through a hollow rectangular dielectric guide with anisotropic surrounding is studied here. It has been shown that anisotropy can be utilized to reduce the loss in resonating structure of the gas laser system.     

Broadband overlaid inset dielectric guide coupler with very flatcoupling

In this paper overlaid parallel coupled inset dielectric guides are proposed for broadband applications to directional couplers. This structure provides much flatter and higher coupling than the conventional one without an overlay. The propagation and coupling characteristics of the coupled guides are obtained by using the integral equation formulation and Galerkin's procedure. Numerical results for two limiting cases are compared with available measured data, showing good agreement. Effects of thickness and dielectric constant of the overlay are examined on coupling and bandwidth. It is found that by suitable choice of these parameters very flat coupling can be achieved for a wide frequency range which is still within the fundamental-mode bandwidth. Examples of couplers with the bandwidth exceeding 45% for the coupling of 3±0.25 dB are presented     

Analysis of the propagation properties in an inverted strip dielectric guide

In this paper the conditions are derived which the three lowest modes satisfy respectively in an inverted strip dielectric guide (ISDG). The method of optimal design is dealt with for five parameters selected by the Orthogonal Array Table (OAT), which affect the propagation properties including the single-mode bandwidth, the external field divergence, the conductor and the dielectric losses. Many sets of parameters are presented, for which the ISDG s have optimal propagation properties.     

Broadside coupled strip inset dielectric guide and its directionalcoupler application

A theoretical and numerical method is presented for the analysis of broadside-coupled strip inset dielectric guide. The method of analysis is based on an integral equation formulation and Galerkin's procedure. Besides propagation constants for two fundamental and higher order modes, the characteristic impedances for the two fundamental modes are calculated using the total propagating power and the longitudinal strip currents. The propagation characteristics of the two fundamental modes are then used to compute 4-port circuit parameters that are essential for accurate analysis and design of coupled line circuits. The effects of various structural parameters on the S-parameters are investigated and it is found that this broadside coupled strip IDG structure is useful for the realization of the directional couplers. Examples of strong and weak directional couplers are given. Furthermore, the propagation constants and S-parameters of coaxially excited coupled strips are measured, and are in good agreement with the theoretical analysis     

Metal wave-guide to dielectric image guide transition using exponential taper

A unique metal wave guide to dielectric image guide transition has been developed using exponential taper in dielectric wave guide. The propagation characteristics have been computed theoretically and taper impedance for the different cross-sections have been evaluated, so as to match it with the metal wave guide for efficient mode conversion. Transmission loss and return loss for triangular and exponentail taper with frequency for same dimensional parameters have been measured.     

Measurement of quality factor of the coupled nonradiative dielectric guide

The dispersion characteristics of non radiative coupled dielectric guide have been computed using mode matching technique. From dispersion characteristics the conductor and dielectric losses have been evaluated and thus knowing the total losses, the quality factor of the coupled non radiative dielectric guide is evaluated in Ka band.     

Image guide couplers with dielectric coupling elements and radiation reduction

Directional couplers in image guide technique for millimeter-wave circuits are discussed, and steps to improve their properties are demonstrated. The simple two-line-9 dB coupler with periodical coupling is compared to a design with an intermediate dielectric coupling element to reduce the frequency dependence. Radiation from the waveguide bends can be reduced significantly by inserting absorber materials at critical points. Experimental results for a-3 dB coupler are also given.     

TE wave properties of slab dielectric guide bounded by nonlinearnon-Kerr-like media

TE wave properties of slab dielectric waveguides with nonlinear non-Kerr-like substrate and cladding are presented. The guide can support even- and odd-symmetric modes in asymmetrical substrate and asymmetrical modes in completely symmetrical substrate. Dispersion relations and electric field profiles are illustrated and analytically discussed in detail     

Full-wave nonlinear analysis of nonradiative dielectric guide circuits including lumped elements

This paper describes the full-wave numerical analysis of complex nonradiative dielectric (NRD) guide structures including linear or nonlinear lumped elements. The numerical results described in this paper, validated through experimentation, show that the method is suitable for NRD guide and similar circuits. Nonlinear analysis of a single-ended NRD guide mixer is carried out, and the results are experimentally verified. Nonlinear harmonic-balance analysis of a novel leaky-wave balanced mixer circuit with very good tolerance of manufacturing inaccuracies in NRD guide configuration in Ka-band is then carried out. Due to curved segments, and orders of magnitude difference in the dimensions of different parts, the analysis of this component requires certain simplifying assumptions. How these can be implemented without sacrificing much accuracy is described. Until now, the design of NRD guide components, especially those using nonlinear effects, has been mostly trial-and-error-based. Here we demonstrate that a more systematic approach is possible.