摘要:

This paper deals with a robust adaptive antenna which suppresses the interference with good protection of the broadband desired signal under imperfect setting of directional constraint. The new guiding principle adopted to control the adaptive antenna is to minimise the output power under the constraint on the cross correlation between the desired signals at the input and output of the array. Accordingly, the principle is named correlation-constrained minimisation of power (CCMP) method. The constraint to protect the desired signal is determined by thea prioriknowledge of the characteristics of the desired signal in terms of its direction of arrival and frequency spectrum. The performances of CCMP and its modified version (improved CCMP) are demonstrated by numerical calculation. The results show that the improved CCMP method achieves high SINR (signal-to-interference-plus noise ratio) and low distortion of the output desired signal even when the desired signal is broadbanded and signal direction is not exact. The limit of the pointing error where the system can function satisfactorily is also discussed.

DOI:10.1049/ip-h-2.1989.0017

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A single directional constrained adaptive array using symmetric amplitude control is presented. The adaptive algorithm is based on the method of projection gradient. The steady-state and transient performances of the array are investigated. Detailed transient analysis for the case of one interference source is performed to get further insight. Results are compared with those obtained with conventional complex weights. It is shown that the new array has a faster real-time convergent rate and its optimal output SNIR is less susceptible to pointing errors.

DOI:10.1049/ip-h-2.1989.0018

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Square loop, meander dipole and spiral antennas printed on grounded dielectric substrates, are numerically analysed using Sommer-feld type integrals. The square loop is found to have a radiation pattern in which cross-polarisation is negligible and zero in theE-plane and theH-plane, respectively. The results obtained for the meander dipole demonstrate that such an antenna can be made small with no deterioration in the radiation pattern. The analysis of the spiral antenna fed from the outer arms shows that the spiral can radiate a circularly polarised wave with a purely resistive input impedance.

DOI:10.1049/ip-h-2.1989.0019

出版商:IEE    

年代:1989

数据来源: IET

摘要:

Rainfall rate data acquired from the UK Meteorological Office are analysed to investigate the statistical stability of cumulative distributions of rainfall rate. Information on the statistical stability of rainfall rate is useful for the design of reliable radio relay systems using frequencies above 10 GHz. By using the rainfall rate data measured at 10 typical locations which have nearly the same long-term cumulative distributions of rainfall rate, distributions of yearly and worst-month cumulative time percentages at several rainfall rate threshold levels are derived. The distributions of the yearly and the worst-month time percentages are approximated by the Gamma distribution and log-normal distribution, respectively. It is found that the parameters used in these distributions depend on the rainfall rate threshold level. By using this empirical result, a concept of a prediction risk is introduced. The dependence of the cumulative distribution on this risk is discussed.

DOI:10.1049/ip-h-2.1989.0020

出版商:IEE    

年代:1989

数据来源: IET

摘要:

An analysis of infinite arrays of rectangular microstrip patches with each element fed by one or two coaxial probes is presented. The probe self-impedance and the rapidly varying patch current near the feed connection point are rigorously included in the analysis by using an attachment mode derived from the corresponding cavity model solution. Two-probe-fed patches are analysed for both reduced cross-polarisation and circular-polarisation applications, and the effect of probe-to-probe coupling in the unit cell is determined. The theory generates results in excellent agreement with waveguide simulator measurements over a wide range of substrate dielectric constants and thicknesses for both one- and two-probe-fed patches, overcoming the drawbacks of previous solutions that used an idealised probe feed model. Similar solutions can be developed for other types of patch antennas and arrays.

DOI:10.1049/ip-h-2.1989.0021

出版商:IEE    

年代:1989

数据来源: IET

摘要:

This paper describes a computationally simple multiquasiparabolic (MQP) model which is largely defined in terms of standard scaled ionospheric parameters. The model gives analytic expressions for ground range estimation. Its results compare favourably with those obtained using numerical ray-tracing through a Dudeney ionosphere. In its present form the MQP model is suitable for use in operational single site location HF direction finding systems at geomagnetic mid-latitudes.

DOI:10.1049/ip-h-2.1989.0022

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A technique is described for steering an antenna beam from boresight using a pair of dielectric wedges. The technique has been developed particularly for the application of a direct broadcast satellite television receive antenna, but would also be usable in other applications. A practical version has been designed and constructed, and the measured performance of this is compared with predictions.

DOI:10.1049/ip-h-2.1989.0023

出版商:IEE    

年代:1989

数据来源: IET

摘要:

It is shown in this paper that low side-lobes, low cross-polarisation and, if desired, symmetrical radiation patterns, can be achieved for horn antennas by placing a properly designed magnetic coating on the inner walls of a horn. The magnetic coating over an electric conductor is, in effect, a simultaneously electric and magnetic conductor in these designs. By choosing appropriate horn flare angles, good antenna performance close to that of corrugated horns was achieved for the magnetically coated horns except for antenna gain reduction due to dissipative loss.

DOI:10.1049/ip-h-2.1989.0024

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The general problem of a cavity-backed aperture radiator is formulated for the tangential electric field in the aperture. The result is used to obtain an integro-differential equation for the special case of a narrow slot backed by a rectangular cavity resonator. This equation is then solved numerically by the method of moments with the proper choice of piecewise sinusoidal basis and testing functions to remove the differential operator in the integrand. Typical numerical results are presented to show the effect of various cavity and slot dimensions on quantities such as voltage distribution along the slot, input impedance, resonance frequency and bandwidth of the antenna.

DOI:10.1049/ip-h-2.1989.0025

出版商:IEE    

年代:1989

数据来源: IET

摘要:

A new vectorial technique, in the sense that data are complex magnitudes and are also treated as complex magnitudes, is presented for the complete characterisation of resonators. This technique is based on fitting the experimental data to the expressions relating them to the parameters which characterise the resonator. We have applied this technique to dielectric resonators coupled to a microstrip line, measuring the transmission coefficient. The values of the transmission coefficient measured at different frequencies near the resonant frequency are fitted to a circumference, which enables us to find the coupling coefficient. The quotient between the imaginary part and real part of the transmission coefficient has a linear relation to the frequency, which enables us to obtain the loaded quality factor and resonant frequency. The results obtained in characterising a dielectric resonator are presented and compared with results obtained by another method. Errors in calculating the coupling coefficient and quality factors are in the order of 1% and for the resonant frequency approximately one part in 106.

DOI:10.1049/ip-h-2.1989.0026

出版商:IEE    

年代:1989

数据来源: IET