Radiation Intensity of the PAVE PAWS Radar System (1979) / Chapter Skim
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'Antenna Pattern'
'Antenna Pattern'
Pages 12-19
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From page 12... ...
Finally, controls must exist to hold the antenna elements within tolerances, and to detect departures from satisfactory operation. Given the tolerance limits for, or statistical descriptions of, the amplitude and phase of the excitation at each radiating element, straightforward calculations can be made with great accuracy of the limits of departures of the antenna pattern from the ideal.
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From page 13... ...
A particular transmitting module simply adds the phase-shifts given by its row and column instructions to determine the phase-shift it then introduces into the signal applied to its input. Were this process carried out with perfect precision and were the individual radiators themselves emitting spherically symmetrical waves, the resulting field would constitute a discrete approximation to a plane wave leaving the antenna face in a direction determined by the phase-shifts.
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From page 14... ...
o Manufacturing tolerances are set on the cables and phase shifters as well as on amplifier gains^ o During operation, the antenna is systematically tested to verify that performance in gain and phase remains within specified tolerances. The intent of the elements of control in combination is to make it possible to think of the antenna pattern as composed of the ideal pattern plus a sum of error signals from the various radiators that are not only individually small but also have no coherent or systematic pattern across the antenna aperture.
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From page 15... ...
Quite apart from the design calculations, measurements have been made to validate the design, and further measurements will be made during operation of the radar. In one part of the contractor's test program the transmitting antenna pattern is probed by tracking satellites: with the receiver pattern fixed so that the satellite appears on the receiving main beam, two transmissions are made, one with the satellite on the main transmitting beam to calibrate the roundtrip loss, and a second with the transmitting beam directed in another direction .
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From page 16... ...
In the case of PAVE PAWS, at a point on the ground where such a maximum occurs,_ if that point is not illuminated by significant radiation from a secondary sidelobe of the unperturbed antenna, the flux density from the error pattern is 5dB below that of an unperturbed secondary sidelobe -- i.e., 35dB below the main lobe-. If the error lobe falls exactly at a point already illuminated by the maximum of a secondary sidelobe and if the error signal adds constructively to the unperturbed sidelobe at that point (constructive addition cannot be ruled out)
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From page 17... ...
Individual transmitting modules can be tested by this same procedure, but that process is not done during the normal cycle of operation. Figure 4 shows that the specific severe malfunction examined earlier, the simultaneous failure of one to several rows of modules, is a most unlikely event unless it results from the simultaneous turning off of about l2 subarrays.
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From page 18... ...
l8 Figure 4 Subarray Positions Courtesy of the United States Air Force
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From page 19... ...
Such a deflection has no effect on the estimates of radiation intensity from the sidelobes that are discussed here. A sufficiently severe random component in the accumulation of ice could increase sidelobes.
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