Browse Prior Art Database

Grated Ground Plane

IP.com Disclosure Number: IPCOM000037362D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Smith, AA: AUTHOR

Abstract

Disclosed is a ground plane constructed of parallel metal strips which improves the accuracy of radiation measurements by reducing reflections of electromagnetic waves from the sides of the ground plane.

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Grated Ground Plane

Disclosed is a ground plane constructed of parallel metal strips which improves the accuracy of radiation measurements by reducing reflections of electromagnetic waves from the sides of the ground plane.

Radiated emissions from products are measured over metal ground planes to determine compliance with regulatory requirements, such as the FCC Rules. Conventional ground planes are made of solid metal or wire mesh. See Fig. 1. The product (or source) 1 is placed on the ground plane 2 and a receiving antenna 3 is placed a specified distance away (usually 3, 10 or 30 meters).

Theoretically accurate measurements of the fields radiated by the product would be obtained on an ideal ground plane, defined as a perfectly conducting plane of infinite extent. Reflections from the edges of finite size ground planes add or subtract from the direct wave and cause the fields to differ from those on an ideal ground plane, resulting in errors in the field strength measurements, especially for vertically polarized fields.

A ground plane constructed of parallel metal strips 4 aligned in the direction of the source-antenna axis offers a low impedance to waves flowing in the direction of the source-antenna axis and a high impedance in a direction normal to this axis. This results in a reduction of the reflections from the sides of the ground plane and more accurate measurements of the fields radiated from the product.

The grated ground plane can be smaller in size t...