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'Pulse Patterns and Peak Power'
Pages 20-28

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From page 20...
... It is in the nature of high gain antennas that the sidelobe pattern is "spiky" in the sense that it is characterized by narrow lobes separated by deep nulls. Designed as the PAVE PAWS antenna is, with particular attention to minimizing the large lobes, a pattern may have a few tens of lobes with peaks within 5dB of the design maximum (i.e., for PAVE PAWS, between 30 and 35dB below the main lobe)
From page 21...
... Table III exhibits for comparison purposes the relevant quantities expressed for a point that is at a distance R in km from the antenna. The reference levels in Table III represent conditions on the axis of a secondary sidelobe- At any point that receives energy only from secondary sidelobes, they describe upper bounds to the measurements that would be made of the indicated quantities.
From page 22...
... 22 Table III ESTIMATES OF RADIATION AND FIELD INTENSITY ON THE AXIS OF A SECONDARY SIDEL'OBE R > .5km " Nominal Worst-Case Maximum flux density, watts/ 3.3 x l05 4.6 x l05 steradian Maximum flux density at distance R km, in yW/cm2 33 R-2 46 R-2 Power-equivalent peak potential gradient at distance R km, in volts/m ll R-l l3 R-l Maximum energy density in one pulse, at R km, in joules/cm2 5.3 x l0-7R~2 7.4 x l0~7R-2 Average power density, at R km, in pW/cm2 8.2 R~2 ll R-2
From page 23...
... In this case, the entries in Table III are not necessarily upper bounds. To state absolute upper bounds for the most unfavorably situated points on the ground near the radar, to which R > .5km, multiply the power entries in Table III by 4 and the peak potential gradient by 2.
From page 24...
... The most nearly regular and systematic operating mode of the radar is called enhanced search. In this mode, the main beam visits successively l20 different positions at 3° .above the horizon, seeking targets at maximum range.
From page 25...
... . From this comparison one is encouraged to believe that Table III, as it refers to average power, is highly conservative and that the model of a "spiky" sidelobe pattern provided by the single curve of Figure 5 is probably not grossly raisrepresentative of the statistics of sidelobe gain seen at a fixed point on the ground as the main beam executes enhanced search.
From page 26...
... O IU CO m \ -40 Main Beam at 3° Elev., 0° Az. RMS= -36.6 dB Al .1 .2 .4 .5 .6 SIDELOBE PATTERNS .7 .8 .9 1.0 Figure 5 Calculated Radiation Intensity During Enhanced Search Courtesy of the United States Air Force
From page 27...
... When measurements are made under standard operating conditions -- i.e., with the antenna searching and tracking and carrier frequencies being shifted -- much longer intervals will be needed to get representative data on either maximum power or average power. Quite apart from the relation between peak values and average values, it is of interest to examine the modulation that appears at a fixed point on the ground on the envelope of the radio frequency carrier (a nominal 435MHz)
From page 28...
... A basic fluctuation fairly regular in peak amplitude at about 0.4yW/cm^ showed a periodicity of two per second; superposed on this was a regular sequence of spikes regular in amplitude at about l.4yW/cm2, having a period of four per l0 seconds. These records were taken with the radar scanning in a search pattern resembling the enhanced search discussed above but containing only 60 beam positions rather than 120.


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