摘要:

Theoretical studies of open and closed surface-wave resonators have been carried out to demonstrate that these structures can be used to perform permittivity measurements on tubular-shaped dielectrics. Some measurements on dielectrics have been made giving experimental results that confirm the theoretical predictions.

DOI:10.1049/ip-h-2.1986.0076

出版商:IEE    

年代:1986

数据来源: IET

摘要:

In the paper simple and compact expressions for the dyadic Green's function in the spectral domain for microstrip-like transmission lines on anisotropic substrates are developed. The method can be used in microstrip and related structure analysis, with the unique assumption that the direction perpendicular to the ground plane of the line must also be a main axis of substrate anisotropy. Hence, the scope of the method covers microstrip-like lines on biaxial and uniaxial dielectric substrates, provided the condition mentioned above is fulfilled, as well as plasma and ferrite substrates magnetised in the direction perpendicular to the ground plane. As a first application, some original structures, i.e microstrip and bilateral finlines printed on an uniaxial substrate, are numerically analysed.

DOI:10.1049/ip-h-2.1986.0077

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A quasi-optical seven-port reflectometer is described and experimental results in the 26–40 GHz frequency range are given.

DOI:10.1049/ip-h-2.1986.0078

出版商:IEE    

年代:1986

数据来源: IET

摘要:

In a previous paper, a practical design method was presented for a circularly polarised printed array antenna composed of strip dipoles and slots (CP-PASS). Although the design method was useful for linear-array type CP-PASS with medium sidelobe levels, the determination procedure for the dimensions of the radiating elements was rather complicated. The paper describes an improved design method for CP-PASS to realise the lower sidelobe levels specified and to provide a much clearer determination procedure for the element dimensions. Some improved points in the array design are described and a generalised design procedure for lineararray type CP-PASS is presented. Finally, a Cheb$$$chev-array CP-PASS with a −20 dB sidelobe level is designed and measured at S-band. Experimental results demonstrate the validity of the improved design method.

DOI:10.1049/ip-h-2.1986.0079

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper presents and analyses a simple and fast adaptive array based on the Davies null-steering beamformer [1]. The use of perturbation algorithms on this beamformer is investigated. The convergence time constants and misadjustment are derived. It is shown that, if the feedback factors for these algorithms are appropriately normalised, the time constants can be roughly equalised, resulting in fast convergence behaviour.

DOI:10.1049/ip-h-2.1986.0080

出版商:IEE    

年代:1986

数据来源: IET

摘要:

A novel combination of a microstrip patch antenna and a truncated dielectric sphere having a relative permittivity 2.2 to 2.5 is analysed using a magnetic line source model for the printed patch and assuming that dielectric resonator action is a second-order effect for the cases considered. Measurements substantiate the computed gain and co-polar pattern characteristics as a function of sphere size, truncation depth and material losses. Optimal illumination of the sphere, and hence maximum gain, is approached only for spheres of radius less than 1.5 free-space wavelengths together with small truncation depths, as is also evident from simple ray tracing. The new element offers greater freedom of design as regards equality ofE- andH-bandwidths, control of co- and cross-polarisation characteristics for a given bandwidth and creation of sparse element arrays with reduced feeder line radiation and losses. Detailed results are given for the application of the element as a reflector antenna feed and in arrays at microwave and millimetre wavelengths. Some ideas for future development concerning radomes and beam scanning are briefly noted, and it is concluded that the new element offers many advantages at the cost of some increase in antenna depth and constructional detail.

DOI:10.1049/ip-h-2.1986.0081

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The paper describes a family of theoretical curves for the rough surface reflection coefficient and an envelope in which these curves lie. One of these curves fits the experimental data well; other experimental data points lie within the envelope.

DOI:10.1049/ip-h-2.1986.0082

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The far-field distribution of a travelling type triangular array of slots on a circular waveguide is evaluated experimentally. The efficacy of the antenna as a satellite onboard antenna is examined, and it is found that such an antenna can indeed be characterised as a good telemetry antenna. With the dominating mode propagating in the guide, the radiation pattern of a single slot, array of slots and array of arrays is obtained experimentally. The experimentally obtainedE-plane radiation pattern of a single slot in the illuminated region compared with the theoretically obtainedresults of geometrical optics and Shafai and Hassan's modematching technique. In a similar manner GTD is used to confirm the experimentally obtained results in the transition and deep shadow regions. The comparison is found to be very good.

DOI:10.1049/ip-h-2.1986.0083

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The backscattering coefficients of a layer of vegetation over a fiat ground using discrete scatter model is studied. The vegetation layer is assumed to consist of randomly oriented leaves. The leaves are modelled by fiat, circular, dielectric discs. The distorted Born procedure is used for computing the mean field in the layer region which is due to an obliquely incident plane wave. Thebackscattering coefficients are then calculated by employing single scattering theory. In performing the necessary averaging, leaves are assumed to have orientation statistics that are azimuthally symmetric with respect to the layer normal. Numerical results for the skin depth of the mean wave and the backscattering coefficients are obtained for vegetation layer which consist of leaves onlyin the Rayleigh and geometric optics regimes.

DOI:10.1049/ip-h-2.1986.0084

出版商:IEE    

年代:1986

数据来源: IET

摘要:

The four dyadic Green's functions of electric and magnetic type for the parallel-plate transmission line are considered. From the expression of the dyadic Green's impedance in the form of a full modal expansion, two terms, diverging at the source point, are extracted and expressed in closed form. The first term represents the quasi-static approximation of the dyadic impedance and coincides with its irrotational part which contains the dominant singularity; the second term represents the lowfrequency approximation of the solenoidal part of the Green's impedance and is singular too. The remaining modal series, which represents a dyadic finite at the source point takes into account wave propagation and converges rapidly everywhere, even when the observation and the source points are very close to each other. Similar expressions are found for the other dyadic Green's functions.

DOI:10.1049/ip-h-2.1986.0085

出版商:IEE    

年代:1986

数据来源: IET