摘要:

An analysis is presented of a finite-length cylindrical antenna which extends through the center of a circular aperture in a perfectly conducting screen separating two dissimilar half-spaces. The screen is planar and of infinite extent while the half-spaces are homogeneous, of semi-infinite extent, and possibly lossy. The screen and the cylinder are perpendicular. The cylinder is excited by the traditional slice generator. Coupled integral equations for the cylinder current and aperture electric field are derived and solved numerically. The effect of the PEC screen on the antenna current distribution is investigated as is the effect of the dissimilar properties of the two half-spaces. It is also pointed out that, for a sufficiently large aperture, the cylinder current is a good approximation of that on the ground stake antenna. Data are presented for cases of interest and are compared with special-case results available in the literature.

ISSN:0920-5071    

DOI:10.1163/156939394X00010

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this paper the Uniform Theory of Diffraction (UTD) is used to calculate the electric field strength near perfectly conducting obstacles. In case suppression of an interfering radio wave is wanted, a parameter of interest is the site shielding factor, which expresses the attenuation of an electromagnetic wave that propagates around an obstacle. Site shielding results are presented for a thin screen and a block-type obstacle, and good agreement between theory and experiment is found for both cases. Another application of the site shielding concept is the prediction of the field strength in an urban environment. For this application the use of a versatile block-type obstacle seems more appropriate. To demonstrate the capability of the models presented, the field strength near a cluster of obstacles is calculated. It is explained how communication parameters such as the Doppler and the delay-Doppler spectrum can be derived from the wave analysis. The model proposed can be of use for the planning and analysis of (future) telecommunications systems and the understanding of the behavior of the (mean) signal strength in urban environments.

ISSN:0920-5071    

DOI:10.1163/156939394X00029

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The perturbed field by a dielectric sphere near a grounded plane bounding a uniform field is given so as to fill the gap between the solution of the case where the sphere is resting on the grounded plane and the case where the sphere is away from the grounded plane. We can now calculate the perturbed field when the sphere is located near the grounded plane. The case of a conducting sphere is studied and used as a check.

ISSN:0920-5071    

DOI:10.1163/156939394X00038

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Metallic gratings have long been used as frequency selective surfaces for applications ranging from beam splitters to polarization filters. These gratings are generally modeled as an infinite array of evenly spaced metallic strips. These structures are usually modeled by assuming that each of the strips in the grating has an infinite conductivity or that all strips are made of the same finite conductivity. In this work, various strip conductivity profiles are analyzed for their effect on the radar cross section area (RCS). The induced currents on each strip are solved to calculate the scattered field.

ISSN:0920-5071    

DOI:10.1163/156939394X00047

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Measurement distance requirements for electrically large, broad beam antennas are investigated in this paper. Design guidelines are developed for determining far-field measurement distances for various pattern types. Results show that while the popular 2D2/λ measurement distance usually ensures accurate measurements of broad beam antenna patterns, measurement distances less than 2D2/λ can provide acceptable results.

ISSN:0920-5071    

DOI:10.1163/156939394X00056

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The use of gradiometer antennas for detection of long conductors in tunnels is analyzed. For reception in vertical boreholes, the gradiometer consists of two vertical magnetic dipoles with a vertical separation. The source is a vertical magnetic dipole located in an adjacent vertical borehole. Both sum and difference responses are useful, but the difference response has the potential advantage of suppressing the primary field and making the scattered field easier to detect. The difference response is most effective in suppressing the primary field for a parallel scan where the transmitting antenna and receiving gradiometer are always at the same height.

ISSN:0920-5071    

DOI:10.1163/156939394X00065

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A full-wave spectral domain formulation for the probe-fed rectangular microstrip antenna is presented. The source is modelled by a magnetic-current frill and multiple modes are used in the probe surface current to account for axial and azimuthal variations. To facilitate computation, the attachment mode for the patch current is represented by a fast converging series. Results are compared with measurements in the literature and several features concerning thick substrate effects are noted.

ISSN:0920-5071    

DOI:10.1163/156939394X00074

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939394X00083

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939394X00092

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor