摘要:

The baluns used in broadband microwave mixers are often in the form of suspended microstrip circuits with tapered conductors. These structures have been analysed using TEM theory of the even and odd modes and results are presented for typical cross-sections. Tapers were approximated by cascading short lengths of uniform line and calculations and measurements were carried out on various tapers. The performance of the baluns is poor at frequencies where the even mode resonates. Between the resonances, the tapers perform better as a balun than a similar structure using uniform strips of equal width. The resonances can be damped by suitably loading the even mode.

DOI:10.1049/ip-h-2.1988.0015

出版商:IEE    

年代:1988

数据来源: IET

摘要:

This paper presents a method for analysing harmonic injection frequency dividers, one that can be used to determine the locking range with any injection power. The method is proved, with an example in which an analysis is made of a divider by three constructed with a GaAs MESFET. Certain conclusions on design are also included.

DOI:10.1049/ip-h-2.1988.0016

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Perforated screens can be used as frequency selective surfaces when a high pass frequency response is required. In this paper, a spectral characterisation of perforated screens is presented. The analysis yields the generalised scattering matrix of each screen, which is a useful tool for studying composite structures. Numerical results, relative to single and double screens with periodical distributions of circular apertures, are discussed.

DOI:10.1049/ip-h-2.1988.0017

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Rainfall-rate data acquired from the UK Meteorological Office are analysed to obtain spatial correlation properties of rainfall rates at 23 locations in the UK. Correlation coefficients of the rainfall rates between two locations are derived, and dependences of separation distance, season, and integration time on the coefficients are clarified. Conditional correlation coefficients, obtained from rainfall-rate data only larger than 1 mm/h at both locations simultaneously, are obtained and related to the nonconditional coefficients. Finally, joint probability distributions of rainfall rates at two locations are approximated by a bivariate log-normal distribution function, in which a modified correlation coefficient is used.

DOI:10.1049/ip-h-2.1988.0018

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The Vivaldi antenna and its feeding transition is investigated. A tapered transition from microstrip to symmetric double sided slot line, fabricated on a low dielectric constant substrate, exhibits a very wide operating frequency range, with no need for a shorting hole. The parameters of the antenna which influence the constancy of beamwidth with frequency are discussed, and the ability to determine the required beamwidth by controlling the antenna length is shown.

DOI:10.1049/ip-h-2.1988.0020

出版商:IEE    

年代:1988

数据来源: IET

摘要:

Anechoic chamber reflection levels, as much as 50 dB down, can be measured at frequencies up to a few gigahertz, with broadband information derived from a single time-domain measurement. The technique has an advantage over frequency-domain methods because it can separate different reflections from each other, allowing any particular area of the walls to be studied in detail. The source of a particular reflection can be identified by its distance from the antennas, as well as direction, so that improvements can be made to the absorber arrangement.

DOI:10.1049/ip-h-2.1988.0021

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The goal of the paper is to improve the log-periodic dipole antenna (LPDA) design procedure introduced by Carrel. A computer-aided design technique is introduced, providing an easyto-use design method of LPDAs. Corrections to Carrel's design contours, and new constant input resistance and truncation coefficients diagrams are presented. The influence of the feeder characteristic impedance, and dipole length-to-diameter ratio on LPDA parameters is studied. Design diagrams for LPDA's typical of HF communications are included.

DOI:10.1049/ip-h-2.1988.0022

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The complex electromagnetic problem of a dielectrically loaded curved wire antenna is formulated in terms of two coupled integral equations. The equations are solved by the method of moments to obtain the circuit and radiation characteristics of the antenna. The numerical algorithm is applied to the study of dielectrically loaded linear, loop, and helical wire antennas. The computed results are compared with experimental data.

DOI:10.1049/ip-h-2.1988.0023

出版商:IEE    

年代:1988

数据来源: IET

摘要:

An alternative approach to the design of narrowband antenna array processors with a specific broadband capability is presented. The approach consists of two parts. In the first part, the processor is constrained to have a unity gain in the desired look direction at the centre frequency of the frequency band of interest. In the second part, an additional set of linear constraints are used to ensure that the gradient of the response of the processor can be approximated to have a zero slope, in the minimum mean-square sense, over the frequency band of interest. Computer simulation results show that the approach is very effective for designing narrowband array processors with broadband capability. The basic approach can also be used to design broadband antenna array processors without the need of presteering time delays.

DOI:10.1049/ip-h-2.1988.0024

出版商:IEE    

年代:1988

数据来源: IET

摘要:

The scattering of a long dipole antenna field by many conducting infinitely long circular cylinders has many engineering applications, such as the simulation of a cylindrical reflector antenna by circular cylinders, in which the feed is a long dipole. The dipole field is considered as incident on the cylinders, resulting in multiply-scattered fields between the cylinders, as well as between each cylinder and the dipole. A self-consistent method is employed for calculating the multiplyscattered fields among the cylinders, while an iterative procedure is used for the multiple scattering between the cylinders and the dipole. Examples illustrating the radiation pattern of simulated parabolic cylindrical, and corner reflector, antennas are shown. The field of a long dipole antenna perturbed by one or two cylinders is given. The paper also shows how one can improve the simulated reflector pattern over the solid reflector by proper choice of the radii and positions of the simulating cylinders along the reflector trajectory.

DOI:10.1049/ip-h-2.1988.0025

出版商:IEE    

年代:1988

数据来源: IET