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Browse Prior Art Database

RFI Measurements on Free Field Site

IP.com Disclosure Number: IPCOM000062702D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Lanham, TE: AUTHOR [+2]

Abstract

When measurements are made of radio frequency interference (RFI) or electromagnetic interference (EMI) from equipment under test (EUT) on a free field site, it is required to distinguish between signals from the EUT and unwanted ambient signals. Direction finding (DF) techniques with two antennas oriented for minimum response from the EUT are used to identify sources of ambient signals which do not originate from the position of the EUT. Ambient signals from broadcast stations, mobiles, general interference, etc., can be difficult to distinguish from EUT emissions, due to the lack of directivity of a receiving antenna. An existing method used to distinguish equipment signals from ambient signals simply switches off the EUT and note which signals disappear.

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RFI Measurements on Free Field Site

When measurements are made of radio frequency interference (RFI) or electromagnetic interference (EMI) from equipment under test (EUT) on a free field site, it is required to distinguish between signals from the EUT and unwanted ambient signals. Direction finding (DF) techniques with two antennas oriented for minimum response from the EUT are used to identify sources of ambient signals which do not originate from the position of the EUT. Ambient signals from broadcast stations, mobiles, general interference, etc., can be difficult to distinguish from EUT emissions, due to the lack of directivity of a receiving antenna. An existing method used to distinguish equipment signals from ambient signals simply switches off the EUT and note which signals disappear. A disadvantage of this method is that ambient signals can disappear at the same time the equipment is turned off. Furthermore, some equipment takes a long time to power up and re-program. A alternative technique is to perform measurements at times when most ambients do not exist, such as 0200- 0600 hours. The problem here is that some ambients never go off, and the limited test time and unsocial hours are also a disadvantage. The system, as shown in the diagram, consists of two DT antennae, DF1 and DF2, symmetrically placed on each side of a line through the EUT and the receiving antenna. In the example shown, the antennae are placed on lines at 45OE to the line of symmetry....