摘要:

The amplitudes of the spurious modes due to a small step in an over-moded circular waveguide are computed, assuming that one of the waveguides is fed by a pure H01mode. It is shown that the amplitude of the H02mode is the largest of the spurious modes.For the reduction of the conversion losses, a simple transducer is designed. Its radius is the geometrical mean of the radii of the two waveguides to be connected. Its length is one-half beat-wavelength of the H01and H02modes.

DOI:10.1049/pi-b-2.1959.0026

出版商:IEE    

年代:1959

数据来源: IET

摘要:

A new centre-excited type of rectangular TE10to circular TE01mode transducer has been devised and its characteristics have been investigated both theoretically and experimentally. This transducer is an improved form of the directional-coupler type. The centre excitation—the magnetic excitation along the axis of a circular waveguide—excites few modes except the circular TE0mones (wheremis an integer), so that the coupling of the rectangular TE10mode to the circular TE01mode can be tightened and that to unwanted modes decreased. Design formulae, effects of unwanted modes and measured characteristics of the new mode transducer are given. The insertion loss of this transducer was from 0.35 to 0.7 dB over a 2 Gc/s band in the region of 24 Gc/s, which is considered to be satisfactory. This transducer is expected to have wide-band characteristics.

DOI:10.1049/pi-b-2.1959.0027

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The theoretical and experimental aspects of a new type of frequency-selective H01-mode transducer in a large pipe are described. The transducer can launch a substantially pure H01-mode in a frequency-selective manner, and may be used for channel insertion.

DOI:10.1049/pi-b-2.1959.0028

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Experimental and theoretical results are presented for a single-conductor launcher consisting of a narrow annular slot concentric with the conductor. It is shown that such launchers can be compared with super-gain aerials, and the implications of this similarity are discussed with reference to surface-wave launchers and launchers for low-loss waveguides.

DOI:10.1049/pi-b-2.1959.0029

出版商:IEE    

年代:1959

数据来源: IET

摘要:

A theoretical analysis of circular electric wave propagation in slightly curved, and slightly non-circular and non-uniform helix waveguide is the basis for design considerations. A radial wave impedance at the helix interface is used to calculate the effect of composite jacket structures.Three different applications of the helix waveguide for circular electric wave transmission are discussed. As a mode filter the helix waveguide should have a lossy jacket which causes a high transmission loss for all unwanted modes. For sharp intentional bends with tapered curvature the helix waveguide should have a jacket of low-loss dielectric material surrounded by a highly conducting coaxial shield. For an all-helix waveguide, in order to reduce both mode conversion-reconversion effects at imperfections and loss in curvature, the jacket should be medium lossy and also surrounded by a metallic shield. The distance between helix and shield should, in all applications, be about a quarter of the radial wavelength in the material. Measurements have been made on unwanted mode transmission in mode filters, TE01loss in intentional bends of low-loss shielded helix waveguide and TE01loss in bends of lossy shielded helix waveguide. Intentional bends of a 2 in-internal-diameter low-loss helix waveguide increase the TE01loss at 55 Gc/s by about 0.001 dB per degree change in direction. In a lossy helix waveguide of 2 in internal diameter a radius of curvature of about 300 ft doubles the TE01loss at 55 Gc/s.

DOI:10.1049/pi-b-2.1959.0032

出版商:IEE    

年代:1959

数据来源: IET

摘要:

A laboratory method of making helical waveguides suitable for short-term field tests has been devised and used to produce an experimental run of waveguide. The method involves the use of an extractable mandrel and a winding process in which the turns, as they are wound, move the winding carriage along automatically. The wound helix is set in a plastic jacket.Problems connected with the manufacture have been analysed and means of improving the final product devised.The waveguides are joined by sticking after being aligned with a precision mandrel.

DOI:10.1049/pi-b-2.1959.0033

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Low-loss circular electric mode transmission over long distances imposes special requirements on waveguide structure. In addition to close dimensional tolerances, small random deviations in straightness approximating the 2 or 3 ft beat wavelength must be prevented to avoid unwanted mode conversions. This made it necessary to improve methods for manufacturing solid-walled copper and copper-lined steel waveguide tubing. Helix waveguide with improved mechanical and electrical transmission properties has also been developed. This is made experimentally by winding a coil of fine wire on a mandrel, applying a lossy jacket over it, encapsulating the assembly in a steel tube with a thermosetting resin and finally extracting the mandrel. Techniques for joining sections into long test runs involve accurately threaded butt joints with vacuum and pressure-tight couplings. Facilities for testing such waveguide systems have been installed at the Holmdel Laboratory.

DOI:10.1049/pi-b-2.1959.0034

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0037

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The problems connected with the design of waveguides suitable for long-distance transmission are briefly analysed, and features peculiar to this transmission medium are contrasted with those of the more conventional kind.All known types of waveguides are discussed and their properties are analysed in detail; it is demonstrated conclusively that the only waveguides suitable for long-distance transmission are the dielectric-coated waveguide and the anisotropic waveguide, of which there are several distinct types. Design formulae for these are given and analysed at length.An extensive quantitative discussion of typical waveguide discontinuities is given, and the mechanism of mode conversion-reconversion, responsible in large measure for signal distortion, is explained. It is shown how to design suitable waveguides (dielectric coated or anisotropic) to counteract these effects successfully.The paper concludes with examples.

DOI:10.1049/pi-b-2.1959.0038

出版商:IEE    

年代:1959

数据来源: IET

DOI:10.1049/pi-b-2.1959.0039

出版商:IEE    

年代:1959

数据来源: IET