摘要:

The analysis of radiowave propagation through, and radar scattering from, the melting layer requires a model of the melting ice particles with appropriate statistics of shape, size, and orientation distributions. Previous studies have indicated that the melting layer can be modelled by a collection of wet snow spheroids in air, of which the effective permittivity and the volume fraction are the most important parameters. It is proposed that the distribution of spheroid shapes can be modelled by a flat probability density of depolarisation parameter λ3between a minimum and a maximum value. The location of the average λ3is crucial; the width is less important.

DOI:10.1049/ip-h-2.1990.0070

出版商:IEE    

年代:1990

数据来源: IET

摘要:

A simple and broadband orthomode transducer (OMT) is presented. It can be machined or moulded in two almost identical parts which implies a potentially cheap design. Both the mechanical construction and the principle of operation are described. The paper also presents results both from some preexperimentations and for the complete OMT. These results show that the isolation between the ports for the complete OMT is better than approximately 50 dB and the return loss less than −20 dB in the frequency range 10.0–15.0 GHz.

DOI:10.1049/ip-h-2.1990.0071

出版商:IEE    

年代:1990

数据来源: IET

摘要:

A simple moment solution is presented for the problem of electromagnetic transmission through a small radome of arbitrary shape. The radome is excited by either a plane wave (receive mode) or an elementary dipole inside the radome (transmit mode). The equivalence principle is used to replace the radome by a set of equivalent electric and magnetic surface currents radiating into an unbounded medium. A set of coupled integral equations involving the surface currents is obtained by enforcing the boundary conditions on the tangential components of the total electric and magnetic fields. The method of moments is used to solve the integral equations. The surfaces of the radome are approximated by planar triangular patches and linearly varying vector functions are used for both expansion and testing functions. Some of the limitations of the method are briefly discussed. In the receive mode, the total field inside the radome is computed along a number of straight lines and in the transmit mode the far transmitted field is computed. A spherical and a Von Karman radome are studied. The computed results are in excellent agreement with the exact or other available published data.

DOI:10.1049/ip-h-2.1990.0072

出版商:IEE    

年代:1990

数据来源: IET

摘要:

This paper presents a moment method analysis of a rectangular slot coupled transition between two dissimilar rectangular waveguides. The effect of the finite thickness of the metallic wall, in which the slot is milled, is taken into account by considering the coupling slot as a small section of a rectangular waveguide. The reflection coefficient and VSWR are evaluated for a transition between WR-90 and WR-112 rectangular waveguides. A comparison between the theoretical and experimental results on the variations of the magnitude and phase of the reflection coefficient is presented for the limiting case when the two waveguides are identical.

DOI:10.1049/ip-h-2.1990.0073

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The rigorous spectral domain method is applied to analyse the resonant frequency characteristics of rectangular resonators in three broadside-coupled suspended stripline configurations. These are (a) broadside-coupled suspended stripline with a single dielectric, (b) broadside-coupled suspended stripline with double dielectrics and (c) broadside-coupled suspended stripline with double inverted dielectrics. Computed dominant even-and odd-mode resonant frequencies of rectangular resonators in the above broadside-coupled configurations are presented as a function of various structural parameters. These characteristics are distinct from those obtained for conventional edge-coupled microstrip resonators. The computed resonant frequencies using simple basis functions are compared with the experimental values in the frequency range 5–13 GHz. The results presented in this paper should find application in the design of microwave and millimeter wave integrated circuit components.

DOI:10.1049/ip-h-2.1990.0074

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Although six-port ANA theory requires that the input impedances of power detectors remain constant with incident power, this is not generally the case if diode detectors are used. Consequently, uncertainties in the measurement of the unknown load reflection coefficient appear. Measurements of the variations of diode input impedances are used in a computer simulation to estimate these uncertainties.

DOI:10.1049/ip-h-2.1990.0075

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The condition for circularly polarised radiation fields from waveguide apertures is discussed. It is shown that ideal circular polarisation cannot be achieved in practice for elliptical hybrid-mode waveguides, neither for corrugated nor for partly filled dielectric (dielcore) waveguides. The crosspolar performance of the elliptical dielcore waveguide supporting the fundamental hybrid-mode is calculated accurately, confirming its good crosspolar performance which has been previously shown by experiments.

DOI:10.1049/ip-h-2.1990.0076

出版商:IEE    

年代:1990

数据来源: IET