95_E_measurempdf - 1955 I RE T R ~ ~ I ~ S A C ' T I O ~ ~...

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1955 IRE TR~~I~SAC'TIO~~S--,JNTE~~~'AS A,VD PROPAGATION Measurement of Electric Field Distributions* 177 R. JUSTICE? AND Summay-The usual method of measuring electric field dis- tributions comprises a receiving antenna at the point observation, connected by means a transmission line to receiving apparatus at some distant point. The principal advantage of the method described here is that it eliminates the transmission line and thus makes possi- ble many measurements which cannot be done by the usual method. It is based on the fact the echo from a thin straight conducting wire is proportional to square the component of electric field parallel to the wire. The practical application at centimeter wave- lengths is described. The method has proven most valuable in a variety problems involving flush mounted directional antennas, radomes, artiiicial transmission lies, etc. INTRODUCTION H UYGESS' Principle applied antenna radia- tion problems states radiation pattern of any source is determined by distribution of the tangential components of electric or magnetic field intensity on any surface which encloses source.lS2 This well-known result is particularly useful in concerning radiating apertures in perfectly conducting closed surfaces such as a slot mounted an infinite cylinder or in an infinite ground plane, more generally, mathematically closed sur- face. In such instances patterns are de- termined E in the aperture. The consider- able interest in such antennas shows importance of a system for measuring accurate117 electric field distribu- tions in the vicinity of such sources of radiation. Con- ventional probing techniques frequently impractical since they introduce disturbing elements into field than can be tolerated. In particular transmis- sion line from the the receiving ap- paratus may so disturb the field as invalidate measurement. Furthermore, in making phase measure- ments, is necessary to transmit rf signal picked up the moving probe back to the fixed receiving ap- paratus, and thus involve passing the rf through a flexible transmission line (or waveguide). The distortion of the rf signal caused by flexing the transmission line is a further objection to the usual method which is serious at short wavelengths (e.g., 3 cm). purpose of this paper is to describe a reflection method of meas- uring electric field distributions vicinity of the source: its principal advantage is the elimination of the * Original manuscript received by the PGAP, December 20, 1954; $ University of Illinois, Urbana, Ill.; formerly at Ohio State Uni- t Ohio State Univ., Columbus, Ohio. 1 Larmor, London Muth. SOL. Proceedings, vol. 1, p. 1; 1904. 4 S. A. Schelkunoff, Bell Sys. Tech. Jour., vol. 15, p. 92; 1936. revised manuscript received, April 1, 1955. versity. IT. H. RUMSEYZ transmission line from the receiving antenna to the re- ceiving apparatus.
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This note was uploaded on 06/11/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

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95_E_measurempdf - 1955 I RE T R ~ ~ I ~ S A C ' T I O ~ ~...

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