MIL-STD-2071A(AS)
APPENDIX
4.4.1.2 Shadow graph. Calculate and plot the shadow graph of first level statistics for discrete chaff units and continuous chaff trails in each of the sampling gates for 35 GHz and each radar band or band set from 2-18 GHz (see figure 3). The shadow graph processing technique depicts RCS as a function of time and shall be used to determine when the chaff is in the radar resolution cell being measured and to define the size of any significantly weak or strong points along the chaff cloud. Upon determination of data that meets these requirements, the pulse-to- pulse information shall be omitted or included in the first and second level data processing depending upon the performance requirements of the detailed specification sheet or purchase description for the applicable chaff type. The saturation level (solid black line) of the shadow graph shall be chosen such that no more than 15 percent of the pulses will be shown as saturated. The number of pulses per second that are printed on the shadow graph shall vary between 0 and
300 based upon the following sequence:
Radar PRF of 0 to 300 - every pulse
Radar PRF of 301 to 600 - alternate pulses Radar PRF of 601 to 900 - every third pulse Radar PRF of 901 to 1200 - every fourth pulse Radar PRF of 1201 to 1500 - every fifth pulse etc.
4.4.1.3 First level statistics. Calculate and print out or display the first level statistics of the RCS values for each of the discrete chaff units or samples of continuous chaff in each of the sampling gates (see figure 4). The first level statistics shall include: the average RCS values of all of the pulses processed in that test group; the standard deviation; the maximum RCS value for any pulse in that group; the minimum RCS value, the RCS value which was equaled or exceeded by
90 percent, 70 percent, 50 percent, 30 percent, and 10 percent of the pulses; and the number of pulses included in the group.
4.4.1.4 Second level statistics. Calculate and print out or display the second level statistics of RCS values for each type of discrete chaff unit or chaff sample that was tested under the same conditions (see figure 5). The statistics shall be the same as those listed in 4.4.1.3 of this appendix except that the inputs will be first level averages instead of the pulse-to-pulse RCS data.
4.4.1.5 Growth curve. Calculate and plot the chaff growth curve (the second level average
RCS values in each of the sample gates, see figure 6).
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