摘要:

A new definition of the effective input noise temperature which allows negative real part source and port imittances and multiresponse systems is proposed. This extended effective input noise temperature is used to modify the Friis formula to include cascading of a large class of multiresponse stages with possibly negative real part source and port imittances.

DOI:10.1049/ip-h-2.1992.0055

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The problem of electromagnetic scattering by a uniaxially anisotropic sphere is studied for both dielectric and absorbing cases. The fields of the TM rořwave inside a uniaxial sphere can be derived to be expressed in series of Bessel functions, as in the isotropic case, but with the order of function determined by the anisotropic ratio (AR =εθ/εr). For the TE tořwave, the uniaxial medium can be treated as an isotropic material characterised byεθonly, which is the permittivity parallel to the boundary surface of the medium. Wave propagation is not affected by the f directed permittivity. The effects of uniaxial anisotropy on the radar cross section (RCS) are also considered. It is found that the uniaxial anisotropy greatly influences the scattering behaviour of a spherical dielectric object. For an absorbing sphere, however, the uniaxial anisotropy no longer plays a significant role as in a dielectric sphere, and the dependance of the RCS on uniaxial anisotropy is found to be predictable. Details of theoretical treatment and numerical results are presented.

DOI:10.1049/ip-h-2.1992.0056

出版商:IEE    

年代:1992

数据来源: IET

摘要:

Planar junction circulators using weakly magnetised disc, wye, triangular and hexagonal resonators have by now been described in the literature. Another resonator that has the symmetry of the 3-port junction circulator is the ring resonator. Since the degenerate and split frequencies in this type of gyromagnetic resonator have already been established in the literature, an understanding of its complex gyrator circuit requires only a definition of its susceptance slope parameter. The purpose of this effort is to tackle this problem.

DOI:10.1049/ip-h-2.1992.0057

出版商:IEE    

年代:1992

数据来源: IET

摘要:

In the paper, by taking into account both diffraction and ohmic losses, a complete analysis of the excitation of an open resonator is developed. The coupling between the rectangular feeding waveguide and the cavity is fully considered, by taking into account all the relevant modes in the waveguide and the open cavity, in order to derive the coupling coefficients. A simple equivalent circuit which accurately describes the cavity excitation as well as the waveguide-cavity coupling, is also derived and validated.

DOI:10.1049/ip-h-2.1992.0058

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The paper describes a technique for characterising an FET or an HEMT chip and the enclosing package without the need to separate the two physically. The standard approach of characterising the two parts separately leads to an inaccurate description of the contribution the package makes to the overall electrical characteristics of the packaged device.

DOI:10.1049/ip-h-2.1992.0059

出版商:IEE    

年代:1992

数据来源: IET

摘要:

New developments in the adaptation of microwave holographic imaging to assess the intermodulation product (IMP) performance of microwave reflectors are described. In particular, a method of assessment of reflecting materials such as wire meshes and carbon fibres that have the potential to generate IMP signals across large areas is given. Identification and location of the apparent IMP sources are provided.

DOI:10.1049/ip-h-2.1992.0060

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A three-dimensional computation of the magnetic and electric fields in a caesium beam frequency standard microwave cavity is performed. The presented method allows determination of a precise distribution of the fields in the junction between the rectangular cavity and a waveguide at cutoff. The formulation uses the electric field, and the Maxwell equations are discretised with edge elements.

DOI:10.1049/ip-h-2.1992.0061

出版商:IEE    

年代:1992

数据来源: IET

摘要:

A simplified tape model has been proposed to obtain the dispersion relation for helical slow-wave structures loaded in a complex manner. It combines the tape model results of field analysis for a helix in free space with the sheath model results of equivalent circuit analysis of the structure with complex loading, which are available in the literature. The dispersion relation obtained by the proposed model, for a helix supported by arbitrarily shaped dielectric support bars in a vanemetal envelope, is found to be identical with that obtained using the tape model of Sensiper for helix in free space extended to the case of a loaded helix. The structure considered is quite general. It includes both anisotropic as well as inhomogeneous loading of the helix. Any specific structure of interest may be interpreted as a special case of this structure. The theoretical results are compared with experimental results reported in the literature.

DOI:10.1049/ip-h-2.1992.0062

出版商:IEE    

年代:1992

数据来源: IET

摘要:

The method of minimal autonomous blocks is briefly described. A universal code computing reflectivity and transmissivity of discontinuities in waveguide structures was developed on the basis of the MAB method. This technique is applied to the solution of dielectric cylinders, metal ridges and bandpass filters in a rectangular waveguide, as well as on shunt posts in a microstrip line. Special attention was given to E-plane tee junctions in rectangular waveguides; scattering matrices are evaluated and approximated by the proper function with dependence on frequency and branch waveguide height.

DOI:10.1049/ip-h-2.1992.0063

出版商:IEE    

年代:1992

数据来源: IET

摘要:

One of the most important tasks for the practical use of nonsinusoidal waves in radar is the design of radiators. Just like resonating radiators for sinusoidal waves, they must efficiently transform a driving current and voltage into electromagnetic waves. However, in addition, the distortions caused by the buildup and decay of the energy stored in the near zone must be avoided, a task not required of the radiators of steady-state sinusoidal waves.

DOI:10.1049/ip-h-2.1992.0064

出版商:IEE    

年代:1992

数据来源: IET