US 3,940,858 AGranted

Method of measuring antenna reflector surface accuracy

AssigneeInternational Telephone and Telegraph Corporation

InventorsEmmanual J. Perrotti, Donald Roy Leger

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Abstract

The antenna reflector whose surface is to be measured is mounted on a moderately level surface. A relatively thin full diameter template is located sequentially at n different locations in the antenna reflector. Spacers are disposed between the template and the reflector surface at each of the n locations. A graduated target is mounted on the template at the certral vertical axis of the reflector. A bench scope is supported and levelled on a table disposed a convenient distance from the target and sighted at the target at each of the n locations. At each of the n locations a height reading is made and measurements of the spacing between the template and reflector surface are made at m intervals along the template. These readings and measurements are recorded in a matrix of n rows and (m + 1) columns. The change in height reading is calculated for each position of the template and used to weight the associated m spacing measurements. The height readings and weighted spacing measurements are employed in a number of equations to obtain the root mean square error of the reflector surface.

A method of measuring antenna reflector surface accuracy comprising the steps of:

a. mounting said antenna reflector whose surface is to be measured on a moderately level surface;
b. centrally locating a relatively thin full diameter template having a curved edge conforming to the desired curvature of said reflector surface and a straight edge in said antenna reflector at a selected location;
c. placing spacers of selected thickness between said curved edge and said reflector surface to space said curved edge from said reflector surface a given amount;
d. mounting a graduated target on said straight edge at the central vertical axis of said antenna reflector;
e. supporting a bench scope on a table disposed at a convenient distance from said target;
f. levelling said bench scope on said table;
g. aiming said bench scope at said target;
h. employing said bench scope to read a height from said target with said template at said selected location;
i. measuring the spacing between said curved edge and said reflector surface at m intervals along said template at said selected location, where m is an integer greater than one;
j. repeating steps (b), (c), (g), (h) and (i) for (n - 1) other different positions of said template, where n is an integer greater than one;
k. recording said n height readings and said m spacing measurements of steps (h), (i) and (j) in the form of a matrix having n rows corresponding to said n positions of said template and (m + 1) columns corresponding to said m spacing measurements and said height reading for each of said n positions of said template;
l. calculating an average template height from each of said n height readings;
m. calculating a change in template height for each of said height readings from said height reading for each of a particular row of said matrix and said average template height;
n. weighting said m spacing measurements of each of said n rows of said matrix by an associated one of said change in template heights;
o. calculating an average of said m weighted spacing measurement from said m weighted spacing measurements for each of said n rows of said matrix;
p. calculating a change in spacing between said curved edge and said reflector surface for each of said m weighted spacing measurement in each of said n rows by said matrix from each of said m weight spacing measurements in each of said N rows of said matrix and said average of said m spacing measurements;
and
q. calculating said surface accuracy by calculating a root mean square reflector surface error from said change in spacing

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Abstract

Claims12