12.02.2014 Views

Radar System Engineering

Radar System Engineering

Radar System Engineering

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

294 ANTENNAS, SCANNERS, AND STABILIZATION [SEC. 9.13<br />

width (or the phasing) by means of screw adjustments on the toggles of<br />

the squeeze mechanism. The a dimension is adjusted within a few<br />

FIG. 9.21.—Endview of AN/APQ-7 scanner.<br />

thousandths of an inch as measured by an inside micrometer, after which<br />

the antenna is set up and its gain maximized by adjustment of the toggle<br />

screws.<br />

All the dipoles shown in Figs.<br />

9.19 and 9.22 are horizontal and<br />

therefore radiate energy polarized<br />

horizontally; but alternate dipoles are<br />

reversed end-for-end in assembling<br />

the array. The spacing between<br />

the centers of adjacent dipoles is<br />

one-half the guide wavelength when<br />

the guide is 1.200 in. wide. Therefore<br />

in each adjacent pair the dipoles<br />

are excited in phase opposition; but<br />

because of the reversal of one of them<br />

they radiate in phase, producing a<br />

broadside beam. If alternate dipoles<br />

FXG.9.22.—Constructionof dipoles used<br />

were absent the beam would<br />

in AN/APQ.7 antenna. still be formed, but would be accompanied<br />

by other strong beams comparable to undesired orders of diffraction<br />

from an optical diffraction grating. As it is, the side lobes are<br />

from 2 to 5 per cent as intense as the main besm.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!