摘要:

The paper presents an application of the boundary element method (BEM) to the calculation of the resonant frequencies of a cavity resonator. A three-dimensional vector boundary integral equation suitable for the cavity resonator problem is first given and then discretised resulting in a generalised eigenvalue equation with resonant frequencies as its eigenvalues. The method is applicable to an arbitrarily shaped cavity and the numerical computation is easy to carry out. To demonstrate the accuracy and the feasibility of the method, several numerical examples are presented.

DOI:10.1049/ip-h-2.1988.0076

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A pattern synthesis procedure is developed for a planar aperture with a circular boundary. A (Ø-symmetric continuous distribution is assumed and required to produce a flat-topped beam with controlled ripple, surrounded by ring side lobes of controlled height. WithMfilled-in nulls in the shaped region, there are 2Msolutions for the aperture distribution. Sampling can yield the excitation of a circular grid planar array. Linear stretching extends the results to an elliptical boundary.

DOI:10.1049/ip-h-2.1988.0077

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A quadratic programming method is described for studying simultaneous sum and difference synthesis compromises, and establishing performance bounds, under the restriction of a two-section array feed network. A composite objective function is minimised, subject to a union of separate sets of sidelobe constraints, for the sum and difference modes of operation, to avoid a conflicting constraint set. Examples are given to illustrate the principal features of the method.

DOI:10.1049/ip-h-2.1988.0078

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The paper presents a new technique for synthesising antenna array pattern with controlled synthesising antenna array pattern with controlled integrate the power response of the array over a spatial region of interest and force it to be less than or equal to a small quantity. The optimal weight vector is obtained by minimising the weight vector norm subject to a linear and aquadratic constraint. Numerical techniques based on matrix factorisation are proposed to reduce the computational complexity. Subsequently, a set of linear constraints, also known as eigenvector constraints, are used to approximate the effect of the quadratic constraint in order to maintain a broad null over the spatial region of interest. This set of eigenvectors can be viewed as an efficient representation of array signals of specified angular occupancy.

DOI:10.1049/ip-h-2.1988.0079

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A design of an inexpensive multi-mode tracking feed antenna, for a circularly polarised signal is described. It uses the TE11and TM01modes, in a smooth circular waveguide, to obtain the sum and difference patterns. The higher order mode, TM01generated within the feed is separated from the dominant mode, TE11by using the resonant mode filter printed on a thin dielectric material. The design of the resonant mode filter is described in some detail. The use of a printed resonant ring with a dual mode horn makes the design particularly inexpensive. Sum and difference patterns with both the dual mode and the corrugated horn are presented for comparison.

DOI:10.1049/ip-h-2.1988.0080

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Rain attenuation data at 19.5 GHz, obtained in a Japanese satellite wave propagation experiment at a measuring rate of 1 sample per second, are analysed. Short term duration statistics of attenuation and statistics of attenuation occurring in available periods, defined in CCITT [1] are derived. In deriving the attenuation statistics during available periods, the total period is divided into periods of available and unavailable times, for several attenuation threshold levels in accordance with the CCITT definition.

DOI:10.1049/ip-h-2.1988.0081

出版商:IEE    

年代:1988

数据来源: IET

摘要:

It is shown that by using Chebyshev weights for the sum pattern while forcing the difference pattern to have the same nulls except for one pair next to the main beam, the performance of a monopulse phased array in direction finding is improved in the sense that the angular accuracy is less affected by the measurement errors of the sum and difference signal power and the sidelobe levels of both the sum and difference patterns are reduced.

DOI:10.1049/ip-h-2.1988.0082

出版商:IEE    

年代:1988

数据来源: IET

摘要:

A method of evaluating mutual impedances between thin dipoles is presented. They may be free or printed ones. It involves an asymptotic expansion of a bidimensional Fourier integral. Very simple algebraic expressions are derived, which are convenient for hand calculations. The numerical results are more accurate than previously. The technique is extended to include the presence of an infinite ground plane. Then, using the stationary phase method, simple coupling equations are derived for microstrip elements.

DOI:10.1049/ip-h-2.1988.0083

出版商:IEE    

年代:1988

数据来源: IET

摘要:

We present an efficient and flexible method for the optimal synthesis of a shaped beam linear array in the paper. This method is capable of dealing with unconstrained as well as constrained synthesis problems. It is based on an iterative process, whose convergence depends on a proper choice of the first approximation. This choice is discussed in detail, and some examples are presented which show the effectiveness of the method in finding the optimal array for a given power pattern.

DOI:10.1049/ip-h-2.1988.0084

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Using an accurate mutual coupling array analysis technique, a theoretical study of the design aspects of an array fed contour beam reflector antenna of the INTELSAT VI type is made. Emphasis is given to the determination of allowable tolerances on the antenna and BFN design parameters, whilst remaining within the main performance constraints of the antenna system. Both single mode and dual mode horn element arrays are considered and their relative merits compared.

DOI:10.1049/ip-h-2.1988.0085

出版商:IEE    

年代:1988

数据来源: IET