摘要:

A procedure which extracts the coupling factor profile from S-parameter measurements of a tapered directional coupler is presented. The difference between implemented and theoretical coupling is used together with knowledge of the cross-sectional dimensions of the coupler to produce a refined coupler design with a more ideal frequency response. Results showing the performance improvements using this technique are presented for a 3 dB quadrature coupler covering 750 MHz–26.5 GHz.

DOI:10.1049/ip-h-2.1992.0032

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A numerical technique has been developed which enables the open-ended coaxial line sensor to be used for measurements on laminar dielectric specimens which are backed by a conducting plane. The theory, which allows the reflection coefficient of the sensor to be computed from the complex permittivity of the specimen, has been tested using an automatic network analyser for measurements on reference liquids at frequencies between 10 MHz and 3 GHz. The discrepancies between theory and measurement do not exceed the estimated measurement uncertainties, provided that the specimen is sufficiently lossy to render reflections from its perimeter negligible. The ability to measure laminar specimens is an important extension to the applications of the sensor in dielectric metrology.

DOI:10.1049/ip-h-2.1992.0033

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A finite-difference time domain scheme for the analysis ofH-plane waveguide discontinuities is described. The two-dimensional treatment of this kind of discontinuities and the use of a non-monochromatic excitation allow us to develop an efficient algorithm with a low demand of computer resources. The method is tested by comparing the numerical results for a right corner bend and a T-junction, the choice of the absorbing boundary conditions is discussed for each case.

DOI:10.1049/ip-h-2.1992.0034

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Static image theory for a homogeneous dielectric sphere, recently formulated by one of the authors, is generalised to the problem of a multilayer dielectric sphere in terms of a line-image charge. The imageline source is seen in this case to be in relation to the so-called static reflection coefficient that could be labelled as a finite Mellin transformation. This transformation is discussed and a Table of corresponding transforming functions is given. The result can be applied in a more complete quasistatic analysis of interactions of layered dielectric spherical particles in an artificial dielectric media. More closely, a two-layer sphere is considered with special cases of a thin layer, and that of a low contrast between the layers. Numerical results are calculated for the radiowave propagation problem of attenuation due to melting hail particles, assumed to be composed of a spherical ice core with a spherical water shell.

DOI:10.1049/ip-h-2.1992.0035

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The problem of electromagnetic scattering from a perfectly electrically conducting cylinder in the presence of a slot in a parallel-plate waveguide is considered. A two-dimensional slot in one of the walls of the parallel-plate guide opens into a half-space in which the twodimensional conducting cylinder resides. The excitation for this structure is an incident TEM wave from within the waveguide, and/or a magnetic line source which produces an incident TEywave in the exterior half-space. Coupled integral equations for the aperture electric field and the cylinder current are derived from first principles and are solved numerically for cylinders of various cross-section, size, and location relative to that of the slot aperture. From knowledge of the aperture electric field and cylinder current, all other quantities of interest may be determined. For TEM excitation from within the guide, the reflection coefficient and radiation pattern data are presented along with the aperture electric field and cylinder current. For external excitation, data are presented that illustrate how the cylinder serves as a shield for the aperture. From this data one can assess the effectiveness of a conducting shield placed over, but not in contact with, the guide aperture.

DOI:10.1049/ip-h-2.1992.0036

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A phase shifter has been designed to give a constant phase over the octave bandwidth 70-140 GHz in dielectric guide. The phase shifter was designed for use in a multistate reflectometer in dielectric guide, though other applications are possible. The multistate reflectometer required two less power meters than a previous six-port reflectometer. The whole device enabled very accurate measurement of phase and amplitude in the range 70-140 GHz for little more than the cost of a swept source.

DOI:10.1049/ip-h-2.1992.0037

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A lossless microwave (dielectric resonator (DR)) active filter is presented. Equivalent circuits for a dielectric resonator coupled to a microstrip line or to another dielectric resonator are developed from an electromagnetic analysis. With the overall electrical model of the passive and active filters described by a microwave CAD program, simulations and sensitivity analysis can be obtained. In the active filter circuit a feedback active loop (composed of a variable gain amplifier and a phase shifter) is coupled to the central DR of the passive filter to compensate for its losses. Measurements of temperature performance, power handling, third-order intermodulation product and noise level are included.

DOI:10.1049/ip-h-2.1992.0038

出版商:IEE    

年代:1992

数据来源: IET