摘要:

An accurate field theory solution for calculating the hybrid eigenmodes of quasiplanar structures is introduced which includes both the influence of the finite strip thickness and waveguide housing grooves. Using the transverse resonance method the size of the characteristic matrix equation is kept constant even for an increasing number of discontinuities. Dispersion characteristics of various structures consisting of at least one isolated strip are presented. The fundamental EH0-modes mainly depend on the finite strip thickness, while increasing waveguide grooves lead to a significant reduction of higher-order-mode cutoff frequencies.

DOI:10.1049/ip-h-2.1985.0001

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Results are presented of the application of the finite-element method to evaluate the resonant frequency and externalQ-factorQeof a cylindrical dielectric resonator operating in the TE01δ-mode, taking into account the effects of the conducting shield and the supporting substrate. Normalised design charts covering a wide range of practical geometrical and physical parameters are presented. Measured values of the resonant frequency and externalQ-factor compare well with the theory.

DOI:10.1049/ip-h-2.1985.0002

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Embedding networks such as bias or feedback elements etc. modify the noise performance of a twoport. This influence is investigated for both lumped and distributed embedding networks and formulas are derived for noise parameters of the embedded network.

DOI:10.1049/ip-h-2.1985.0003

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Phase constant characteristics of generalised asymmetric three-coupled microstrip lines are presented and discussed. The influence of various structural parameters, as well as the effects of dispersion, are incorporated to show the behaviour of three fundamental guided modes.

DOI:10.1049/ip-h-2.1985.0004

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A measuring system for determining the complex permittivity of low-loss solids using a frequencytuned TE01cavity resonator of fixed length is described. Its mechanical construction is simple, and measurements, in particular of the real part ε' of the permittivity, can be performed within a relatively short measuring time with high precision ($$$δε'/ε'|< 7 × 10−4), for a large number of frequencies in a given frequency band. The method is compared with the standard method where a length-tuned resonator is involved. Theoretical error investigations and practical measurements at frequencies of about 10 GHz on polymers and fused silica are carried out showing that the uncertainties have comparable values in both methods.

DOI:10.1049/ip-h-2.1985.0005

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Bradley and Dudeney's model of the vertical distribution of the ionospheric electron concentration consists of three distinct sections. Both theE-region andF2-region are described by parabolic variations. A linear increase is assumed to exist between theE-region peak and theF2-region. This model is currently recommended by the International Radio Consultative Committee (CCIR) for use in long-term HF sky-wave prediction work. If a slightly modified electron-concentration profile is adopted, it is possible to derive exact expressions which describe some important characteristics of oblique ray paths in the model ionosphere. Ground range, group path, phase path and apogee height can all be computed using this technique. Collisions and the effect of the earth's magnetic field are ignored. These expressions have been used for several applications where a knowledge of multipath structure on ionospheric paths is necessary.

DOI:10.1049/ip-h-2.1985.0006

出版商:IEE    

年代:1985

数据来源: IET

摘要:

Owing to the interest raised by the precipitation effects in the design of satellite and terrestrial microwave radiolinks, it is necessary to have a simple and valuable mathematical model which can represent, with good accuracy, the whole rain-rate distribution, from lowest rain-rate values to the tail of this distribution. Previously the author suggested a two-parameter model which adequately represents the rainfall intensity cumulative distributions for several hydrometeorological zones of the world. This model has log-normal asymptotic behaviour for low rainfall rates, and gamma asymptotic behaviour for the high ones. The present paper deals with a further improvement by expressing both parameters as a function of the rainfall rate exceeded during 0.01% of the time, and recommended by the CCIR to evaluate the availability of microwave radio links.

DOI:10.1049/ip-h-2.1985.0007

出版商:IEE    

年代:1985

数据来源: IET

摘要:

An analytic solution to the problem of array pattern synthesis having null and norm constraints is given. We show that the required complex weight vector can be obtained by finding the eigenvector corresponding to the maximum eigenvalue of a Hermitian matrix. The generality of the method is illustrated by applying it to synthesise patterns with multiple look directions.

DOI:10.1049/ip-h-2.1985.0008

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A new description of the profiles of the main reflector and subreflector of a dual-reflector antenna is given in terms of a single parameter, the angle subtended by the normal to the main reflector and the axis of the system. It is shown that the same parameter describes the nature of the focusing in both the illuminating beam and the image space. Hence, quite general illumination, focusing and main reflector profiles can be considered. The results are illustrated for subreflectors in the concave hemisphere and paraboloid, for axial illumination and offset conditions, and the application of the method to amplitude shaping or the Abbe sine condition is discussed.

DOI:10.1049/ip-h-2.1985.0009

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A modification of Prony' method, in which an attempt is made to constrain the roots of the polynomial to the unit circle, is used to resolve a number of plane waves illuminating a uniformly spaced line array. A least squares method based on the eigenstructure of a certain correlation matrix is developed to handle the overdetermined case when there are excess numbers of antenna elements. Angle estimate variance is compared to the Cramer-Rao lower bound and with the forward-backward linear predictor method.

DOI:10.1049/ip-h-2.1985.0010

出版商:IEE    

年代:1985

数据来源: IET