摘要:

This paper proposes an extension of the source operating noise temperature and the introduction of a load operating noise temperature. These new operating noise temperatures are based on extensions of the traditional operating noise temperature and allow active as well as passive port, source and load immittances, where active and passive denote immittances with negative and positive real parts, respectively. Determination of the operating noise temperatures through the use of extended effective output noise temperatures is discussed.

DOI:10.1049/ip-h-2.1992.0022

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The influences of tensor parameters on the characteristics of microstrip structures on layered ferrite-dielectric substrates for phase shifter applications are investigated. By fully incorporating the permeability tensor into the numerical model, it is found that the propagation constant, and particularly the characteristic impedance values, are substantially lower than those commonly calculated under the scalar permeability assumption. The variation of the characteristic impedance is presented with respect to magnetisation levels, saturation magnetisations and the thickness of the ferrite layer.

DOI:10.1049/ip-h-2.1992.0023

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A simplified and improved approach for the one-dimensional nonlinear multisignal analysis of a complete helix TWT has been developed. The model takes into account both the loss and circuit variation along a tube and the inherent backward wave and reflections due to mismatch at the input and output couplers. The model is generalised to consider any number of simultaneous signals, including generation of higher-order harmonics and intermodulation components. It is fast, for interactive use, and takes less than two minutes on a Micro-Vax computer to determine the detailed characteristics of a typical tube for four-signal operation with frequencies separated by nearly 10%. The energy balance factor is satisfied within ±1%, even at saturation. The accuracy of the model was checked by comparing computed results with published and experimental results for different types of helix TWT.

DOI:10.1049/ip-h-2.1992.0024

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The results of an experimental study of two compound parabolic reflector antennas are reported. The reflectors were designed to have equal beamwidths at two separate frequency bands. The inner region of the reflector was formed as a conducting metallic surface; the outer region was a frequency-selective surface designed to be highly reflecting at the lower frequency band, and transmitting at the higher band. The performance of the compound reflector is compared with that of an equivalent wholly metallic paraboloid.

DOI:10.1049/ip-h-2.1992.0025

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A numerical parametric study is presented, of a circularly polarised square hard horn realised by dielectric-filled longitudinal corrugations. The horn is analysed as an open waveguide. The attenuation introduced by losses in the dielectric material is calculated from the characteristic equation of the modifiedTE10mode. The far field, including radiation from the walls, is found from the electric vector potential. The attenuation, aperture efficiency and crosspolar sidelobe level are presented for different dielectric linings and waveguide sizes, and are compared with the performance of the smooth-walled horn.

DOI:10.1049/ip-h-2.1992.0026

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A near-field far-field transformation technique involving the amplitude of the measured data has been recently proposed. It requires two sets of near-zone amplitude measurements and relies upon a mean-square fitting of the measured amplitude by an iterative projection algorithm. In the paper the method is applied to the case of cylindrical scanning, for which all the details are explicitly worked out. Furthermore the probe effect is accounted for and the relative correction procedure is considered. The relevance of a rough phase estimate and/or a general knowledge of the source is also discussed to overcome the difficulties related to the presence of local minima which can trap the procedure. Numerical examples validating the effectiveness of the technique are provided.

DOI:10.1049/ip-h-2.1992.0027

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The low surface resistance of high temperature superconductors enables the construction of resonators which have significantly higherQs than equivalent resonators made out of conventional conductors. Resonators are widely used in microwave work in many different applications, and it is therefore important to assess the performance of different types of resonant device to ascertain the improvement which is possible for each particular type. Experimental results on four different resonators are reported here, the cylindrical cavity, coaxial cavity, helical cavity and a coplanar resonator. The resonators have been constructed out of different high-temperature superconducting materials.

DOI:10.1049/ip-h-2.1992.0028

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A simple, single fed structure consisting of a pair of crossed dipoles connected to two angular branches which easily produces circular polarisation is proposed. This antenna, with a director, placed over a ground plane is analysed and a design example is realised and measured at 2 GHz.

DOI:10.1049/ip-h-2.1992.0029

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The technique of solving integral equations describing a microstrip antenna structure using the method of moments is well known and widely used. In the paper an efficient procedure is given to determine subsectional edge expansion functions (SEEFs) containing the correct singularities of the currents at the edges of a rectangular patch (both the current parallel to and the current normal to an edge). It is proven that the use of these SEEFs considerably improves the convergence of the calculated resonant frequency. For one configuration calculated results are compared with measured values.

DOI:10.1049/ip-h-2.1992.0030

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The dispersion curves of circular open chirowaveguides have been obtained by two different methods. The first is based on the fulfillment of the boundary conditions at the surface of the guide. The second is based on the expansion of the electromagnetic fields in the chiral guide in terms of the modes propagating in the dielectric guide having the same geometry, permittivity ε and permeability μ. It is assumed that the chirality admittance is much smaller than □(ε/μ). The frequency behaviour of the dispersion curves and the coupling processes occurring between the modes along the guide are analysed.

DOI:10.1049/ip-h-2.1992.0031

出版商:IEE    

年代:1992

数据来源: IET