摘要:

We consider the diffraction of a plane wave by an infinite set of parallel equidistant half planes. On each plate the total field vanishes on one side, and the normal derivative vanishes on the other side. A closed‐form solution to this new canonical diffraction problem is presented for Bragg angle incidenc

ISSN:0048-6604    

DOI:10.1029/RS017i003p00453

年代:1982

数据来源: WILEY

摘要:

We generalize the technique of using spin‐weighted spheroidal harmonics to calculate electromagnetic scattering cross sections of spheroidal conductors for axially incident radiation. This paper extends the method to waves of arbitrary polarization and angle of incidence, and serves as the foundation for numerical work to be reported in a second paper in this serie

ISSN:0048-6604    

DOI:10.1029/RS017i003p00463

年代:1982

数据来源: WILEY

摘要:

The radiation pattern of a parallel‐plate waveguide with adjacent guides of finite depth is calculated by ray‐optical methods. The pattern may be adjusted by changing the width and depth of the parasitic guides. Experiments with a longHplane sectoral horn at about 12 GHz show good agreement with the the

ISSN:0048-6604    

DOI:10.1029/RS017i003p00473

年代:1982

数据来源: WILEY

摘要:

The horizontal circular loop antenna near a planar interface between two materials is analyzed theoretically for both the transmitting and the receiving cases. For the transmitting antenna the distribution of current, input admittance, and electric field in both media are obtained by applying a limiting process to the previously obtained results for the eccentrically insulated circular loop antenna. The receiving formulation is for an electromagnetic plane wave incident at an arbitrary angle from either side of the interface, i.e., incident from either the region that contains or the region that does not contain the loop. Parametric studies are used to investigate the effect of the interface on the input admittance of the loop and the directive properties for the electric field of the loop in both media. Measured input admittances and electric field patterns of model loop antennas above and below an interface between air and fresh water are in good agreement with the theoretical calculations.

ISSN:0048-6604    

DOI:10.1029/RS017i003p00483

年代:1982

数据来源: WILEY

摘要:

The propagation of electromagnetic waves in media with various horizontal layers has been analyzed. The electromagnetic fields outside the source region were obtained from the dyadic Green's functions for the case of media with three and four layers and for horizontal and vertical electric dipoles. These results agree with those obtained using Hertz potentials. One of the major results is a generalization of the dyadic Green's functions for solving the problem of media withNhorizontal layers.

ISSN:0048-6604    

DOI:10.1029/RS017i003p00503

年代:1982

数据来源: WILEY

摘要:

The TM wave due to a horizontal magnetic dipole is first expanded in terms of a series of integrals, each of which is interpreted as due to an image source. Each of the image source integrals possesses a branch point and a high‐order pole which can be close to the saddle point. To facilitate uniform asymptotic approximation, the branch point is first removed by a transformation, which results in an integral with a high‐order pole near three saddle points. The uniform asymptotic approximation of such an integral is obtained through the use of the generalized Weber's function. The result agrees with numerical integration much better than the geometrical optics approximations (GOA). For the case of TE waves, the pole is far away, and our analysis reduces to the three‐saddle‐point analysis where the behavior of the wave can be approximated by parabolic cylinder functions. We show that in such a case our result agrees better with the experiment than GOA. The uniform asymptotic approximation of the waves extends the domain of validity of the image source representation, which is extremely useful when the layer i

ISSN:0048-6604    

DOI:10.1029/RS017i003p00509

年代:1982

数据来源: WILEY

摘要:

This paper presents a practical method for computing radio fields in regions of strong focusing, using ray intercept data provided by a standard ray‐tracing program. The procedure extends the usefulness of the ray trace by allowing fields to be computed near caustics and cusps where ray density calculations fail. Using a plane wave decomposition of the field components, phase integrals are computed by curve‐fitting intercepts of rays traced through ionospheric or tropospheric media whose refractive indices vary arbitrarily with altitude. A numerical algorithm is described for performing the plane wave angular spectral integrations. This procedure avoids the complications associated with higher‐order asymptotic techniques, allowing a broad range of refractive‐index profiles to be analyzed by a single method. It is applied to two sample profiles, and the results agree very closely with higher‐order stationary‐phase estimates in caustic regions. Moreover, the computer code runs efficiently, despite the presence of highly oscillatory integrands. The method is capable of including the effects of weak collisions, the spherical earth, and azimuthally dependent transmitter con

ISSN:0048-6604    

DOI:10.1029/RS017i003p00514

年代:1982

数据来源: WILEY

摘要:

A new simple formula is derived as an approximation for the general exact integrals for the radial component of the electric field generated by a horizontal electric dipole in a half‐space of water or earth near its boundary with air. The field in the water or earth is investigated as a function of radial distance from the source for εr= 80, 20, and 4, over wide ranges of conductivities and frequencies. Special attention is paid to the ranges in which the direct wave from the dipole produces an interference pattern of standing waves when it interacts with the lateral wave. For selected values of the parameters the radial electric field computed from the new simple formula is compared with the field evaluated numerically from the exact integrals. The agreement is excellent when the ratio of wave numbers characteristic of the denser half‐space and air is large, quite good even when this ratio is as small

ISSN:0048-6604    

DOI:10.1029/RS017i003p00521

年代:1982

数据来源: WILEY

摘要:

New simple formulas are derived as an approximation for the exact general integrals for the transverse and vertical components of the electric field generated by a horizontal electric dipole in a half‐space of water or earth near its boundary with air. These formulas supplement the earlier derivation of the more important radial componen

ISSN:0048-6604    

DOI:10.1029/RS017i003p00532

年代:1982

数据来源: WILEY

摘要:

A homogeneous multilayer approximation is applied to a two‐dimensional transversely nonuniform cold plasma waveguide. As a result, the homogeneous multilayer modeling for an inhomogeneous slab is shown to be invalid for such plasma waveguides. The propagation constant of the TM mode supported by a multilayered plasma slab is found to diverge at a series of the extended Tonks resonance frequencies corresponding to a series of layer boundaries, that is, plasma density discontinuities. It is indicated that the inhomogeneous multilayer modeling having no density discontinuities can eliminate the above difficult

ISSN:0048-6604    

DOI:10.1029/RS017i003p00539

年代:1982

数据来源: WILEY