摘要:

The propagation characteristics of guided waves in a rectangular waveguide with transverse corrugations on all four walls is investigated both theoretically and experimentally. The theoretical solution obtained is an improvement on an earlier analysis, providing a basis for the assumption that the corrugated side walls of the guide act, very approximately, like a smooth metal-walled guide. It is also shown that the new solution, in contrast to the earlier solution, satisfies the impedance compatibility relation.

DOI:10.1049/ip-h-2.1985.0074

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A novel method is presented for determining the large singleSparameters of transistors under drive conditions using data obtained from load-pull measurements. The technique uses a load which can have a variable amplitude and phase, and can thus control the amplitude and phase of the signal at the device output. A mathematical analysis of the method is presented and typical results for the large-signalSparameters of an X-band FET are given. The gain compression and AM/PM conversion limits of a linearised power amplifier are then calculated.

DOI:10.1049/ip-h-2.1985.0075

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper deals with the dynamic analysis of microstrip structures. It is shown that the mixed-potential integral equation for stratified media, which was introduced in a previous publication, provides a rigorous and powerful approach. The Green's functions belonging to the kernel of the integral equation are expressed as Sommerfeld integrals, in which surface wave effects are automatically included. A two-dimensional moment's method using subsectional basis functions has been chosen. Thus, microstrip patches of any shape can be analysed at any frequency and for any substrate. Practical numerical aspects are carefully discussed, and special numerical devices are introduced to reduce computation time without loss of accuracy. Complete results for a rectangular patch and for a slotted patch are given and compared with measured values. Radiation patterns corresponding to the ideal situation of a substrate with infinite transverse dimensions are presented for a rectangular patch.

DOI:10.1049/ip-h-2.1985.0076

出版商:IEE    

年代:1985

数据来源: IET

摘要:

A numerical method is used to investigate the radiation from undulated microstrip line antennas. The undulated line is assumed to be suspended over a ground plane and its current distribution is determined using a moment method type solution. This current distribution is then used to compute the co-polar and cross-polar radiation fields. It is found that the current distribution has an oscillating behaviour along the line, with a frequency which is twice the number of undulations. The cross-polarisation is found to be high and relatively independent of the undulating shape. Its relative level, however, is reduced for large arrays, due to the array factor affecting the co-polar field. A procedure for the reduction or elimination of the cross-polarisation is then proposed, which is based on utilising two undulated lines with mutually inverted undulations. A design method for achieving low sidelobe levels is also proposed and a design example with sidelobes around the −40 dB range is presented.

DOI:10.1049/ip-h-2.1985.0077

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The study of interference due to scattering by hydrometeors within the common volume of two antenna beams, has centred previously on the scattering characteristics of the hydrometeors. Little attention has been paid to the nature of the common volume and its modelling, which can have order of magnitude effects on the magnitude of the interfering signal in extreme cases. The paper compares two existing models of the common volume which are currently in use with more accurate models developed within the text. Results are given for a variety of geometries in terms of the effective common volume; the common volume weighted by the antenna gain patterns. These demonstrate the severe limitations of the existing models. All current models assume the antennas to be aligned exactly, such that the beam axes intersect. A model is developed within the paper that allows for cases where the axes do not intersect. Results are presented for this arrangement showing that significant common volumes exist, provided the distance of closest approach of the axes is small.

DOI:10.1049/ip-h-2.1985.0078

出版商:IEE    

年代:1985

数据来源: IET

摘要:

An RF holographic technique was deployed as a diagnostic aid to ascertain whether the frequency range of an existing antenna could be increased. A simple economical subreflector was subsequently built to compensate for the observed astigmatism. A further holographic test was carried out to align the new subreflector, and the new antenna now operates satisfactorily in the 11 GHz band in Cassegrain mode.

DOI:10.1049/ip-h-2.1985.0079

出版商:IEE    

年代:1985

数据来源: IET

摘要:

In the paper, the method of alternating orthogonal projections is derived for the problem of array pattern synthesis with multiple null constraints. The required complex weight vector is obtained via an iterative algorithm starting from the known ‘look direction’. The projection operators required in the algorithm are shown to be easily computed from the ‘look direction’ vector and the null-constraint vectors. A lower bound on the rate of convergence of the algorithm is also established.

DOI:10.1049/ip-h-2.1985.0080

出版商:IEE    

年代:1985

数据来源: IET

摘要:

In a microstrip antenna, the resonant frequency of a particular mode is determined by the shape and size of the conducting patch, the relative permittivity of the substrate and, to some extent, the thickness of the substrate. If the resonant frequency is to be changed, a new antenna is usually needed. Recently, Lee and Dahele have shown that the resonant frequencies of microstrip antennas can be changed by introducing an adjustable airgap between the substrate and the ground plane. In addition to providing a means for tuning the resonant frequencies, the airgap also has the effect of increasing the bandwidth of the antenna. The purpose of the paper is to present a comprehensive report on our research on microstrip antennas with airgaps. First, experimental results obtained by introducing an airgap in (i) circular-discs, (ii) annular-rings and (iii) dual-frequency stacked-disc microstrip antennas are presented. Secondly, the theories that have been developed are described. Thirdly, comparison between theoretical and experimental results is given.

DOI:10.1049/ip-h-2.1985.0081

出版商:IEE    

年代:1985

数据来源: IET

摘要:

General penetrable-edge conditions are derived from a new approach to diffraction by a dielectric wedge. The increased computational efficiency, to be expected from satisfying these edge conditions explicitly, is illustrated with numerical evaluations of the surface fields on wedge cylinders, and by comparison of measured and computed resonant frequencies of cylindrical cavities loaded with dielectric sectors. Additional evidence is provided for the apparent validity of our recently suggested technique for calculating the E-polarised field scattered from the vicinity of the apex of a penetrable wedge.

DOI:10.1049/ip-h-2.1985.0082

出版商:IEE    

年代:1985

数据来源: IET

摘要:

The paper describes a calibration technique for multiport reflectometers using only four different short-circuit terminations and a matched load. The calibration constants that are evaluated are the constants associated with the bilinear relationship which holds between the waves at the relevant measurement ports.

DOI:10.1049/ip-h-2.1985.0083

出版商:IEE    

年代:1985

数据来源: IET