摘要:

A broadband method for measuring the dielectric constant of liquids is presented. The method utilises both an automatic network analyser and a computer. It is based upon measurements of resonance frequencies andQ-factors in resonators filled with the liquid. First the physical shape and the calculation model are described, then practical measurements of unrefined oil from the North Sea are presented. They show that the relative real part of the dielectric constant drops from approximately 2.17 to 2.15 and that the relative imaginary part falls from about 40 × 10−3to 9 × 10−3in the frequency range 300 MHz – 12 GHz.

DOI:10.1049/ip-h-2.1989.0088

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The radial variation of refractive index in the Maxwell fish-eye can be derived from the stereographic projection of the geodesies of the uniform sphere, as shown originally by Luneburg. This produces a perfect focus at the point diametrically opposite the source point. The generalisation of this is a refractive index law that provides for repetitive refocusing at points equispaced about the circle and for a medium which is axisymmetric. It is shown that this can be derived as the stereographic projection of a nonuniform sphere on which the latitudinal refractive index is such that the same form of focusing is obtained about the equator. The method in reverse then gives the surface law on the sphere corresponding to any radial variation in the plane and is illustrated for the Luneburg lens itself.

DOI:10.1049/ip-h-2.1989.0089

出版商:IEE    

年代:1989

数据来源: IET

摘要:

The paper deals with the electronic tuning of a 950 MHz shielded dielectric resonator (DR) operating in its fundamental mode by use of a loop-varactor circuit. It is shown that this tuning mechanism leads to considerable degradation of unloadedQand jumps in resonant frequency. A tuning range of 1 MHz with unloadedQin excess of 9,000 were obtained.

DOI:10.1049/ip-h-2.1989.0090

出版商:IEE    

年代:1989

数据来源: IET