摘要:

AbstractA two‐dimensional solver combining the finite‐element method (FEM) with the boundary‐element method (BEM) has been implemented and results have previously been compared to analytical solutions using canonical problems. The code has now been applied to predict scattering from electromagnetically larger, inhomogeneous, and lossy objects of more complex shape, including a coated aerofoil, and the results are compared to analytical as well as experimental data. The cross sections modeled were up to 15 wavelengths in Size. © 1994 John Wiley&Son

ISSN:0895-2477    

DOI:10.1002/mop.4650070402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA simple Kirchhoff‐based approximation is presented to account for the mode conversion at discontinuities such as bends and steps in open‐ended waveguide ducts. Comparisons with other more numerically exact approaches and with experimental results for a variety of two‐ and three‐dimensional inlet duct configurations show that this approximation is surprisingly accurate when the transverse dimension of the duct is above 5 wavelengths. This approximation reduces the computational burden of predicting the scattering from large inlet ducts. © 1994 John Wiley&S

ISSN:0895-2477    

DOI:10.1002/mop.4650070403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA 4‐GHz phase shifter based on a hybrid coupler terminated with reverse‐biased UHF general‐purpose diodes is shown capable of providing excellent tuning responses, adequate for noncritical applications. The assembly demonstrates that considerable component specijcation relaxation can be implemented for low microwave frequencies. © I994 John Wiley&Son

ISSN:0895-2477    

DOI:10.1002/mop.4650070404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn this article we establish a symmetry condition for nonuniform pupils with different transmission functions to produce the same response along the axis. Besides, these pupils can produce different effects in the transverse response like apodization or hyperresolution. We also show the relation that different annular pupils have to satisfy in order to produce identical axial behavior. Some results of annular color filters that fulfill this condition are given. © 1994 John Wiley&Sons, Inc

ISSN:0895-2477    

DOI:10.1002/mop.4650070405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA rigorous analysis of two‐dimensional scattering of a dielectric slab eigenmode from a penetrable cylinder is carried out by an integral equation method. A new procedure for reduction of an initial integral equation system to a well‐conditioned matrix equation is developed. Numerical results are presented for cylinders with different cross‐section shapes. A physical explanation of the revealed effects is proposed. © 1994 John Wiley&Son

ISSN:0895-2477    

DOI:10.1002/mop.4650070406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAn original model for timing jitter estimation in optical‐fiber PPM is developed and used to examine the performance impairment due to imperfect slot synchronization. An original expression that predicts the spectral properties in the presence of jitter is presented. The extracted slot clock timing variance is evaluated in terms of the PPM parameters such as the number of slots and the modulation index, and the effects of the other parameters such as the phase‐locked loop (PLL) bandwidth and the fiber bandwidth are examined and used to optimize the slot clock timing variance. Original results are presented for the system wrong slot error (WSE) probability due to imperfect synchronization. The results indicate that this probability can be maintained well below the 10−9system operating error rate. The model enables the identification of the set of optimum PPM, PLL, and fiber parameters for a given required performance. © 1994 John Wiley&Son

ISSN:0895-2477    

DOI:10.1002/mop.4650070407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn this article a spectral‐domain decoupling method of electromagnetic waves propagating and radiating of sources in bianisotropic gyroelectromagnetic chiral media is presented, and the general transmission‐line‐like equations for the description of field quantities (IE‐, VE, VM, IM) are obtained using the technique of matrix transformation, which has been developed by Tsalamengas. As a practical application, the propagation behavior of electromagnetic waves in multilayered bianisotropic gyroelectromagnetic parallel‐plate chirowaveguides is investigated, and it is shown that in such a nonreciprocal chirowaveguide, propagating modes are always hybrid (EH and HE). Especially, the dyadic Green's function of sources in a grounded bianisotropic gyroelectromagnetic chiral superstrate‐substrate structure is derived, and it can be directly used to analyze the radiation characteristics of gyroelectromagnetic chirostrip antennas. © 1994 John Wil

ISSN:0895-2477    

DOI:10.1002/mop.4650070408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA closed‐form expression is obtained for the directivity of a uniformly spaced broadside array of collinear half‐wave dipoles with similar excitations. The directivity is then optimized and the amplitude distribution is obtained for various spacings of the dipoles and different numbers of elements. A comparison between the optimum and nominal directivity is presented. It is observed that for increased separation, the optimum and the nominal directivities are practically the same. © 1994 John Wiley&Sons,

ISSN:0895-2477    

DOI:10.1002/mop.4650070409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn this article we will describe a concept that we call active splitting. It is based on an extension of an existing structure. The primary advantages to active splitting are that it provides large frequency bandwidth and cascadability. Additionally, active splitting produces gain rather than loss. This feature allows us to design cells with multiple (more than two) in‐phase outputs and to adjust gain by using bias points on the same coplanar structure. © 1994 John Wiley&Sons, I

ISSN:0895-2477    

DOI:10.1002/mop.4650070410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Pruppacher‐and‐Pitter (PP) raindrop model has been well accepted as a realistically distorted raindrop model. To employ this model for the investigation of radio wave attenuation by rain requires tedious numerical calculations. In this Letter a simple mathematical formula is used to simplify and improve the expression of the nonaxisymmetric distorted raindrop shapes, enabling the scattered field by rain to be derived analytically. The coefficients in the formula are determined for different raindrop sizes by translating the polar coordinates vertically and fitting the shapes of the Pruppacher‐and‐Pitter‐form raindrops to the shapes discussed in this Letter. Using the least‐squares method, a general expression for the coefficients in terms of the raindrop sizes is obtained. A comparison of the raindrop shapes obtained from the Pruppacher and Fitter expression and the expression in this Letter demonstrates the validity of the simplified formula for realistically distorted raindrops. © 1994 John Wil

ISSN:0895-2477    

DOI:10.1002/mop.4650070411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY