Browse Prior Art Database

Surface Wave Coupler

IP.com Disclosure Number: IPCOM000094786D
Original Publication Date: 1965-Jun-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Vinding, JP: AUTHOR

Abstract

This coupling device is for use between a coaxial line and a surface wave line. The coupling device provides impedance matching by multiple quarter-wave transformers. The coaxial line is, for example, of 50 ohm impedance with confined electric and magnetic fields. The surface wave line, for example, a G-string, is of 350 ohm impedance with fields theoretically extending to infinity.

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Surface Wave Coupler

This coupling device is for use between a coaxial line and a surface wave line. The coupling device provides impedance matching by multiple quarter- wave transformers. The coaxial line is, for example, of 50 ohm impedance with confined electric and magnetic fields. The surface wave line, for example, a G- string, is of 350 ohm impedance with fields theoretically extending to infinity.

Coupler 10 connects coaxial line 12 to G-string 14 and includes a 3-section transformer arrangement ED, DC, CB. Each section is a quarter wavelength long. The characteristic impedance for each is chosen to give the selected response, e. g., maximally flat, equal ripple, binomial, or other. The number of sections required depends on the desired bandwidth and the impedance ratio. The increasing thickness of dielectric 16 tends to concentrate the fields, but a significant part is still likely to be outside the dielectric at C.

In order to control these fields, a new surface wave line is formed by coating outer conductor 18 with dielectric 20 and terminating it at B with a short circuit formed by conductive flange 22. Since the distance CB is a quarter wavelength, the short circuit at B is transformed into an open circuit at C where it is connected in parallel with line 12. The thickness of dielectric 20 is chosen as a compromise between the requirement for small field extension, to keep the flange size down, and high characteristic impedance, to keep the useful ban...