摘要:

By using the theoretical relationship between attenuation and depolarisation, a cumulative distribution of depolarisation can be predicted from a distribution of attenuation at the same frequency. In the case of earth-space paths, however, it was found that there is poor correlation between measured attenuation and XPD because of so called ice depolarisation. This implies that the predicted XPD value for an earthspace path includes an error if the theoretical relationship between rain attenuation and XPD is used.In this paper, a new method of predicting cumulative distributions of XPD is proposed in which the effects of the ice depolarisation are taken into consideration by using the factor of ‘ice depolarisation ratio’. The applicability of this depolarisation prediction method is verified by using attenuation and depolarisation statistics which have been measured in some wave propagation experiments along earth-space paths.

DOI:10.1049/ip-h-2.1990.0060

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The impedance properties of a dual concentric annular ring microstrip patch antenna are described. This patch operates at two frequency bands which may be closely spaced. The TM12 mode is primarily investigated but other modes are also treated. An equivalent circuit model for the input impedance is presented together with experimental verification. Surface waves are found to be important even for very thin substrates and these are included in the model. Factors which influence the ring design are discussed.

DOI:10.1049/ip-h-2.1990.0061

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The admittance characteristics of a system consisting of two centre-fed dipole antennas of arbitrary orientation are investigated. Each antenna is modelled by a very thin prolate spheroid which is centrally fed by a gap voltage. By using the equivalence principle, each spheroidal dipole is replaced by a solid spheroidal conductor of the same size without a gap, encircled by a corresponding filamentary ring carrying magnetic current of proper magnitude. The associated electric and magnetic fields are expanded in terms of appropriate vector spheroidal eigenfunctions and the boundary conditions at the surface of each spheroid are imposed by using the rotational-translational addition theorems for vector spheroidal wave functions. The solution of the resulting set of algebraic equations gives the unknown scattered field expansion coefficients. Numerical results are presented for the mutual admittance of two centre-fed thin spheroidal dipole antennas of arbitrary orientation, for various centre displacements. In addition, theEandHplane patterns are computed for the system of two dipole antennas in various configurations, with one dipole being parasitic.

DOI:10.1049/ip-h-2.1990.0062

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The problem of a centred-inclined radiating slot cut in a broad wall of a rectangular waveguide and excited by a TE10mode wave is considered. Pertinent integral equations for the slot aperture electric field are solved using the method of moments. Scattering characteristics of the slot are then analysed including resonant length and the equivalent series impedance. Numerical results on resonant length and the normalised series impedance in a universal form are obtained over a range of values of tilt, slot width, waveguide height, wall thickness and frequency. These results should find applications in the design of arrays of centred-inclined slots.

DOI:10.1049/ip-h-2.1990.0063

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The array synthesis problem is of utmost importance and therefore a large number of papers have been devoted to it. A new synthesis method based on the intersection approach is presented: the synthesis is viewed as the problem of finding the intersection of sets. This is a more natural, flexible and effective formulation of the problem but despite this it has not previously received much attention. The search for a point belonging to the intersection of two sets allows a very effective solution procedure, based on the projector concept and on a suitable choice of the starting point of the iteration. A number of one and two dimensional examples are presented to highlight the various aspects of the method. Emphasis is put on constrained array synthesis which is important when the practical realisation of the synthesised array is of concern. The method permits the synthesis of constrained patterns without appreciable degradation of the pattern desired.

DOI:10.1049/ip-h-2.1990.0064

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Infinite arrays of two-dimensional printed elements are analysed using the finite difference method. Grid models accounting for dielectric discontinuities and current continuity at rectangular junctions are developed. The procedure is used to study the behaviour of three configurations of planar strips over dielectric substrates in an infinite array environment. These configurations include the ‘dipole’ element, the ‘microstrip’ element and the ‘microstrip’ element over an inhomogeneous substrate. For each configuration, calculated results are presented with special attention given to the correctness of antenna characteristics such as input impedance and scan performance. The results accurately predict antenna performance and comparison with published data confirms the method.

DOI:10.1049/ip-h-2.1990.0065

出版商:IEE    

年代:1990

数据来源: IET

摘要:

A matching slot pair which radiates all the incident power in a circularly-polarised wave is proposed and analysed for use as a terminal in a leaky-wave slotted waveguide array. The position and size of the slots are numerically optimised to suppress reflection and to realise a desired polarisation in the tilted beam direction, which contributes to improving the antenna efficiency. It is verified experimentally that the return loss is below –15 dB over 0.1 GHz at the 4 GHz band and the 3 dB axial ratio bandwidth is about 5% in the tilted beam direction.

DOI:10.1049/ip-h-2.1990.0066

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Based on the one-dimensional finite element method reported in References 1 and 2, a general formulation is presented for the calculation of the conductorQ-factor,Qc, associated with metallic losses of cylindrical cavity resonators loaded axisymmetrically with dielectrics. The formulation is employed to accurately determineQcrelating to the first few modes of the cylindrical cavity resonator loaded with a hollow cylindrical dielectric as well as to obtainQcrelating to the fundamental mode (TE01δ) of the ring resonator on a microstrip substrate.

DOI:10.1049/ip-h-2.1990.0067

出版商:IEE    

年代:1990

数据来源: IET

摘要:

An extension of the multiport network modelling technique applied to rectangular microstrip patches on thin substrates covered with a dielectric layer is reported. The edge admittance networks for the radiating edges and the mutual coupling network for the external interaction between the two radiating edges are obtained from the spectral domain solution for fields of a magnetic current element placed on a conducting ground and covered with a dielectric layer. Results of the analysis for single-port and two-port patches are compared with experimental results. The good agreement validates the model and the analysis procedure proposed.

DOI:10.1049/ip-h-2.1990.0068

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The Lorentz gauge is the preferred gauge when problems in electromagnetic scattering and diffraction are solved by a classical Maxwell equation potential function approach. The free space magnetic vector and scalar potentials subject to the Coulomb gauge are obtained in the paper. It is shown that the Coulomb gauge vector potential dyadic Green's function can be extracted from the well known Lorentz gauge free space vector potential Green's function. The electric field mixed potential integral equation (MPIE) for a straight, circular, finite-length, narrow conducting cylinder scatterer is formulated and solved in both the Lorentz and Coulomb gauges and results are presented in terms of the cylinder surface current. The merits and drawbacks of the Coulomb gauge formulation are discussed.

DOI:10.1049/ip-h-2.1990.0069

出版商:IEE    

年代:1990

数据来源: IET