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Transmission Line With Windowed Ground Plane

IP.com Disclosure Number: IPCOM000101838D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Hayward, M: AUTHOR

Abstract

A stripline balanced transmission line is disclosed, in which the line's characteristic impedance can be tailored by the use of a windowed ground plane.

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This is the abbreviated version, containing approximately 72% of the total text.

Transmission Line With Windowed Ground Plane

       A stripline balanced transmission line is disclosed, in
which the line's characteristic impedance can be tailored by the use
of a windowed ground plane.

      A stripline balanced transmission line, as shown in Fig. 1,
comprises two conductors 10 side by side on one surface of a
dielectric lamina 20 (for example, a flexible polyimide lamina).  On
the other surface of the lamina there may be a conductive ground
plane 30.  The ground plane is not required for radiation shielding,
since the far-field radiation from the balanced line is effectively
zero. Instead, the ground plane has an effect on the characteristic
impedance of the transmission line.

      A line with no ground plane would have a particularly high
impedance and would therefore be susceptible to induced interference.
Conversely, if a continuous ground plane were used the line's
impedance would be very low and a high current would be needed to
drive the line.  A characteristic impedance between these two
extremes is therefore desirable.

      It is known that the characteristic impedance of a stripline
transmission line may be increased by reducing the width of
conductors 10.  However, to increase the impedance of the line with a
continuous ground plane to a satisfactory value the conductors would
have to be extremely narrow. This would lead to manufacturing and
reliability problems.

      Fig. 2 shows a plan view of a balanced strip...