摘要:

A rigorous mode matching technique combined with Floquet's theorem is applied to analyze a variety of periodically loaded dielectric waveguides. Characteristic equations of the structures are derived. Dispersion relations and the phase/group velocities are determined by solving the characteristic equations. Numerical results including the passband/stopband characteristics, slowing down of phase velocities, and a backward wave phenomenon are presented. The dependence of the dispersion curves on the structures' parameters is discussed. Properties of complex modes existing in the prohibited frequency bands are also explored. These structures have potential applications in microwave and millimeter wave filter networks and slow wave or backward wave structures for traveling wave tubes devices.

ISSN:0920-5071    

DOI:10.1163/156939391X00590

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A (bi)anisotropic scattering object is imbedded in a plane-stratified anisotropic or bianisotropic medium. Scattering matrix elements Sαβ(kt, kt) relate amplitudes of outgoing eigenmodes α of the host medium to incoming eigenmodes β, and are defined in terms of the projections of the incident and scattered wave vectors, k and k', , on the stratification plane. If the media of the scattering object and its environment are replaced by the Lorentz-adjoint media, and all modes are time-reversed, so that an outgoing wave in the given medium becomes an incoming wave in the the adjoint medium, it is found that the time-reversed modes are eigenmodes of the Lorentz-adjoint medium. Furthermore, the scattering matrix S(L)(-kt, -kt') in this medium equals the transposed scattering matrix ST(kt', kt) in the given medium. In the limiting case where the (bi)anisotropic medium becomes homogeneous this yields a straightforward eigenmode generalization of a scattering theorem due to Kerns.

ISSN:0920-5071    

DOI:10.1163/156939391X00608

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The coupled-wave theory is generalized to analyze the diffraction of waves by chiral gratings for arbitrary angles of incidence and polarizations. Numerical results are illustrated for the Stokes parameters of diffracted Floquet modes versus the thickness of chiral gratings with various chiralities. Both horizontal and vertical incidences are considered for illustration. The diffracted waves from chiral gratings are in general elliptically polarized; and in some particular instances, it is possible for chiral gratings to convert a linearly polarized incident field into two nearly circularly polarized Floquet modes propagating in different directions.

ISSN:0920-5071    

DOI:10.1163/156939391X00617

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The problem of electromagnetic scattering byathree-dimensionalapertureformed by a cavity in a ground plane is formulated via the equivalenceprinciple andintegral equation approach. The resulting coupled integral equations are solved via Galerkin's method using piecewise constant and piecewise linear surface basis functions.Thenumerical and analytical aspects of the implementationarediscussed and some representative scattering patterns arepresented forvalidationpurposes.

ISSN:0920-5071    

DOI:10.1163/156939391X00626

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In this paper we present a novel algorithm for radiometric and polarimetric calibration of complex quadpolarization SAR data. It is based partially upon known targets in the image and partially upon the assumption of reciprocity of all other scatterers; no other assumptions about background scatterer statistics are required. The only manmade targets required by the basic algorithm are a trihedral-dihedral corner reflector pair for calibration at each range (a more general technique which requires two arbitrary passive targets is outlined as well). The algorithm presented here is an improvement over previous ones in that it does not require three known targets or azimuthal symmetry of the background to solve the polarimetric calibration problem. Results are presented using airborne SAR data.

ISSN:0920-5071    

DOI:10.1163/156939391X00635

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

For an elliptically polarized wave propagating through a forested canopy a polarimetric propagation model has been developed to account for frequency, incidence angle, polarization, leaf orientation distribution, leaf size and moisture content. In this model the canopy is considered as a layer of randomly oriented scatterers. Then the loss and the depolarization factors for such a canopy are obtained via the coherent field and the coherent intensity approaches. The two approaches are shown to give identical expressions for the loss and the depolarization factor. For a coniferous canopy modeled as a layer of randomly oriented cylinders of finite length, the model gives values for the loss factor in agreement with the measurements. Numerical simulation is conducted at X-band to calculate the microwave transmission loss within a coniferous forest canopy. The simulation study reveals that the vegetation orientation distribution plays an important role in the transmission properties of an elliptically polarized wave. In addition, it was observed that the loss factor for a linearly polarized field was canopy-type-independent when the angle between the vertical axis and the incident electric field was around 50°.

ISSN:0920-5071    

DOI:10.1163/156939391X00644

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00653

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00662

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0920-5071    

DOI:10.1163/156939391X00671

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor