摘要:

Some radiation characteristics of a narrow nonresonant slot close to, or straddling, the centre line of a notched-wall dual-mode waveguide are presented, and compared with the behaviour of similar slots in the corresponding single-mode guide. The theoretical results have been evolved using Bethe's small-hole diffraction theory. They are supported by some experimental evidence.

DOI:10.1049/ij-moa.1978.0031

出版商:IEE    

年代:1978

数据来源: IET

摘要:

Membrane waves at ultrasonic frequencies can be excited in thin stretched foils. In this paper the effects of surrounding air load on the propagation and attenuation properties of membrane waves are discussed. The air-mass loading makes the membrane waves slightly dispersive. Attenuation, in the case where the membrane wave does not radiate to the air, is mainly due to the viscous and thermal-conductivity losses in a thin boundary layer on the membrane surface. The electrostatic-excitation method is discussed in detail and includes the derivation of the voltage-transfer function. Theoretical results are compared with the measurements.

DOI:10.1049/ij-moa.1978.0032

出版商:IEE    

年代:1978

数据来源: IET

摘要:

The problem of broadband matching of a high-QresonantRLCload to a resistive source which often arises in microwave circuits is considered. A coupled uniform quarter-wave transmission line is suggested as the matching network. An approximate procedure for determining the parameters of the coupled line to achieve broadband matching is described.

DOI:10.1049/ij-moa.1978.0033

出版商:IEE    

年代:1978

数据来源: IET

摘要:

The efficiency of lossless volume holograms in converting plane and cylindrical waves into each other is analysed and the results are plotted as a function of the normalised thickness of the hologram. A coupler consisting of two separate holograms, and capable of converting a divergent cylindrical wave into a convergent cylindrical wave, is also investigated, and it is shown that under favourable conditions an overall efficiency of 98.3% may be obtained.

DOI:10.1049/ij-moa.1978.0034

出版商:IEE    

年代:1978

数据来源: IET

摘要:

The time-averaged electric energy density near the focus of a lens or mirror system with annular aperture is calculated. The distribution shows greater difference from the paraxial approximation than for the full circular aperture. The vector distribution of the polarisation after focusing greatly affects the field near the focus. In particular, a mirror with annular aperture which deflects a plane-polarised wave through a small angle gives a distribution in the focal plane which exhibits bright rings around a dark centre. The field distribution of an annular system is found to consist of just two modes of free space.

DOI:10.1049/ij-moa.1978.0035

出版商:IEE    

年代:1978

数据来源: IET

摘要:

Some of the new filters which have been developed in the past decade to meet the exacting requirements of satellite communication are reviewed. The principles of a number of novel filters are outlined, their most significant characteristics are described, and their advantages in satellite applications are discussed.

DOI:10.1049/ij-moa.1978.0036

出版商:IEE    

年代:1978

数据来源: IET