摘要:

The classical multipath model of mobile communications is reviewed and the importance of phase derivatives with respect to space and frequency is emphasised. Using an analogy it is shown that the group delay follows a Student'st-distribution, delay spread as the determining parameter, and does not depend on the details of the power delay profile. The delay spread is the second central moment of the average power delay profile. The distribution is important for frequency selective effects of datacommunication over a narrowband channel.

DOI:10.1049/ip-h-2.1990.0039

出版商:IEE    

年代:1990

数据来源: IET

摘要:

An efficient numerical approach, based on the boundary element method, for the analysis of electromagnetic field distributions in twodimensional tunnels with discontinuities such as L-bends, T-junctions, and cross-junctions is described. The side walls of the tunnels are assumed to be lossy dielectric and the surface impedance approximation is used to determine the boundary condition on the side walls. A computer program has been developed for tunnels excited by a line current or a TE dominant mode. A comparison of the numerical results with the experimental results using microwave simulation shows a good agreement except in the vicinity of the inner wall of the output tunnel perpendicular to the excited tunnel.

DOI:10.1049/ip-h-2.1990.0040

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Resonators are coupled to external circuits in different ways. It is possible to measure several magnitudes in each configuration, e.g., the transmission or reflection coefficients. There are different expressions that relate the measured magnitudes to the resonator's characteristic parameters. In the paper the authors reduce many of these expressions to two basic forms, a scalar or vectorial expression, that permits a similar treatment. A brief description of a method for the processing each expression and some results are presented.

DOI:10.1049/ip-h-2.1990.0041

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The paper presents digital memory based predistortion circuits for direct microwave PSK modulation with data prefiltering. The required predistortion for a slotline microstrip transmission type BPSK modulator and a microstrip reflection type BPSK modulator is computed. The measured spectrum and eye diagram results prove the effectiveness of the proposed method

DOI:10.1049/ip-h-2.1990.0042

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The computation of the scattering matrix of a junction between two coaxial lines is described. Scattering matrix derivatives with respect to geometrical characteristics, permittivity and frequency, can also be obtained using the same method. It then becomes possible to optimise the structure under test. The equations are solved using the finite element method. The formulation uses Maxwell's equation by considering electromagnetic fields as vector distributions.

DOI:10.1049/ip-h-2.1990.0043

出版商:IEE    

年代:1990

数据来源: IET

摘要:

A model is proposed for the frequency conversion mechanism in hot carrier harmonic mixers. The model can be easily incorporated in any complete circuit analysis program and can provide an improved analysis for hot carrier harmonic mixing.

DOI:10.1049/ip-h-2.1990.0044

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Dyadic Green's functions for a rectangular waveguide with an E-plane dielectric slab are derived using the Ohm–Rayleigh method. As discontinuities exist in the transverse direction, the Hausen vectors are constructed so that they correspond to either the LE or LM mode of this configuration.

DOI:10.1049/ip-h-2.1990.0045

出版商:IEE    

年代:1990

数据来源: IET

摘要:

The design and optimisation of a rugged 94 GHz balanced mixer is described. The mixer is of the crossbar type and incorporates novel millimetre wave integrated circuitry. Two monolithic, balanced Schottky diodes are used as the nonlinear elements. The diodes, together with the associated antenna coupling structure, are fabricated using planar processing techniques. Broad band operation is possible, with a double sideband conversion loss of 6.5 dB and a noise temperature of less than 1000 K measured at 90 GHz with a 4 GHz IF at room temperature. The mixer structure is analysed using scale modelling techniques which indicate how this performance can be improved

DOI:10.1049/ip-h-2.1990.0046

出版商:IEE    

年代:1990

数据来源: IET

摘要:

Principles for wide bandwidth antenna arrays are presented. The performance is illustrated theoretically and experimentally with an eight element planar array of Archimedean spirals. The performance goal of a clean main beam and acceptable sidelobes over at least two octaves was achieved.

DOI:10.1049/ip-h-2.1990.0047

出版商:IEE    

年代:1990

数据来源: IET