摘要:

A rigorous analysis of the problem of scattering from an incidentE-polarised wave on a dielectric-loaded perfectly conducting strip is presented for a line source and plane wave excitations. The vector Green's theorem is used to derive an integral equation for the unknown electric and magnetic field components. The singular component of the magnetic field is then cancelled out by properly choosing the auxiliary fields and boundary conditions. The unknown expansion coefficients of the scattered electric field are determined by numerically solving an infinite set of simultaneous linear equations after truncation. The accuracy of the proposed solution is verified for the loaded and unloaded strip by comparing the resulting values of the scattered field with those based on the method of moments. For the loaded strip, the dependence of the scattered field as well as the scattering cross-sections on the strip width, dielectric constant and angle of incident wave is investigated and presented for plane wave incidence.

DOI:10.1049/ip-h-2.1989.0035

出版商:IEE    

年代:1989

数据来源: IET

摘要:

By using the Green's function/variational formulation with a new form of charge distribution, expressions for the characteristic impedance and electric (E-) field are obtained for an asymmetric TEM cell. The main details of a series of computer programs to implement an optimum design of theE-field distribution are presented in this paper.

DOI:10.1049/ip-h-2.1989.0036

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The propagation and radiation behaviour from a partly filled (with dielectric) elliptical waveguide is considered. From an approximate analysis we investigate the potential of such a waveguide for radiating a pure circularly polarised shaped beam. We also establish a quantitative measure of the deterioration in linear cross polarisation performance of a balanced hybrid mode with loss of circularity.

DOI:10.1049/ip-h-2.1989.0037

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Among the geometries used for acquiring the near-fields of microwave antennas, the plane-polar geometry is the most recent. This contribution describes far-field predictions obtained on a recently built plane-polar facility. The procedure for the transformation of the near-field to the far-field uses a fast algorithm for the calculation of the radiation integral and is presented in the form of a cross correlation which is carried out using the fast Fourier transform. Predictions of the far-field patterns of two antennas are shown. A numerical algorithm for the interpolation of the near-field from the plane-polar grid to the cartesian grid is derived and the interpolated data is used to predict the far-field patterns of the two antennas. A direct result of the interpolation to a cartesian grid is the adaptability of the near-field to processing for antenna metrology, enabling the surface diagnosis of antennas under test from measured plane-polar data. A technique for phase drift compensation is presented and verified. The phase drift compensation procedure is particularly suited for the plane-polar geometry.

DOI:10.1049/ip-h-2.1989.0038

出版商:IEE    

年代:1989

数据来源: IET

摘要:

First-order scatter from statistically inhomogeneous and periodic random rough surfaces is treated by the boundary perturbation technique. The single array of rough strips on a perfectly conducting plane and the complementary arrays of rough strips are examined. Using a sampling approach, it is proved that scatter is produced through a multiple Bragg resonance mechanism. The scattering behaviour of the single array of rough strips is investigated numerically. Scatter for the corresponding surface which is covered throughout by roughness is used as reference. The numerical results indicate that the incidence/scattering directions are related to the orientation of the strips while the sensing radio wavelength is related to the strips width and period. Possible applications for this class of scatterers are discussed.

DOI:10.1049/ip-h-2.1989.0039

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Simple and effective models for the equivalent circuit parameters of waveguideE-plane metal septum are presented. It makes the design ofE-plane bandpass filters very easy. The computer-predicted frequency responses were found to be in good agreement with the measurements.

DOI:10.1049/ip-h-2.1989.0040

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Matching using a coaxial double slug transformer particularly in relation to measurements on microwave transistors at 0.5–2 GHz, is described. The limits arising from tuner loss and the correction to transistor gain which needs to be applied are determined analytically. The correction is compared with that deduced from reflection measurements, good agreement being obtained. The use of parallel plate line is investigated and from itsQ-factor is shown to be a possible lower loss alternative to coaxial line in this application, provided that small radiation effects can be suppressed.

DOI:10.1049/ip-h-2.1989.0041

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A rigorous field analysis of the problem of two identical perfectly conducting parallel wedges with dented edges loaded with a dielectric cylinder, and excited by an electric or magnetic line current in the upper sector, is given in this paper. The dielectric medium is assumed to be linear, homogeneous, isotropic and free from losses, whereas the mediums of the upper and lower sectors are free space. A field equivalence theorem is used to derive, for each excitation, a system of coupled integral equations for the equivalent magnetic currents on the dielectric interfaces, which is later solved using Galerkin's method. The fields and powers transmitted into the lower sector, hence the transmission coefficients, for both polarisations are subsequently determined in terms of the equivalent magnetic currents on the lower dielectric interface. The analysis is then specialised to the problem of a slit loaded with a dielectric cylinder, as well as to the case of plane wave excitation. Sample numerical results for the dielectric-loaded double dented wedge and slit problems in the case of plane wave excitation are also given.

DOI:10.1049/ip-h-2.1989.0042

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The method of moments is often used when solving for the mutual coupling in arrays of aperture antennas. For elements that are waveguides or gradually flared horns the aperture fields can be approximated by a finite sum of waveguide modal functions. To solve for the flared horn case an approximation for the aperture impedances of the modes in the horn is needed. The WKB approach can be used to find these impedances, but this technique has an important limitation. It is known to fail in the vicinity of it's turning points. The turning point is the cutoff point of the mode being considered. To overcome this limitation a different technique, the spherical mode approach, is discussed. This approach has no cutoff problems and works well for conical and pyramidal horns. Comparisons between the impedances and the resulting dominant mode reflection coefficient found using the two techniques are presented to illustrate this point.

DOI:10.1049/ip-h-2.1989.0043

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A previously derived asymptotic expression for the reflection coefficient at the feed of a paraboloidal reflector antenna covered with a paraboloidal radome is shown to be valid, with suitable modifications, for general reflector-radome configurations. This generalisation is illustrated through the particular choice of a paraboloidal reflector covered with a spherical radome. The generalised asymptotic expression for this geometry agrees very well with the numerically calculated integral expression obtained by the power coupling theorem.

DOI:10.1049/ip-h-2.1989.0044

出版商:IEE    

年代:1989

数据来源: IET