现在假设雷达发射一系列脉冲串，每个脉冲串在前一次脉冲串结束后100毫秒开始。
Now suppose that theradar transmits a series of pulse bursts, each one starting 100 ms after theprevious burst.
此时，飞机#1和#2在相邻CPI之间的角度变化为2 mrad，大于了1.5 mrad的角度去相关间隔。
The angular changebetween aircraft #1 and #2 from one CPI to the next is then 2 mrad, which isgreater than the 1.5 mrad decorrelation interval.
因此，预计相邻CPI之间的飞机RCS是不相关的。
Consequently, it isexpected that the aircraft RCS during a given CPI will be uncorrelated withthat during other CPIs.
图2.16b使用另一个10×5 m随机复杂目标模型说明了以上类似的影响，其中的雷达和运动参数与上述描述相同。
Figure 2.16billustrates these effects using another 10 × 5 m random complex target model with the radar and motionparameters just described.
对每个脉冲上的目标观察RCS绘制了五个CPI的数据。
The RCS observed forthe target on each pulse is plotted for five CPIs.
注意，RCS在每个CPI内几乎都是常量。
Notice that the RCSis nearly constant within each CPI.
CPI内部最大的RCS变化只有0.4dB左右。
The greatestintra-CPI variation is only about 0.4 dB.
而相邻CPI之间的RCS变化明显很大，本例子中约为9dB。
Significantly greatervariation is seen from one CPI to the next, with the total range in thisexample being approximately 9 dB.
因此，可以通过从指数PDF中选择一个随机值来表示每个CPI的RCS，从而合理地模拟五个CPI的完整RCS数据集。
Consequently, thefull set of five CPIs of data could reasonably be modeled by drawing one randomvalue of RCS from an exponential PDF to represent each CPI.
一个CPI内的所有脉冲都使用相同的RCS值。
The same RCS value isused for all pulses within a CPI.
如果使用脉冲间频率捷变且频率步进超过式（2.63）规定的30 MHz，则预计每个单独脉冲的RCS与所有其它脉冲不相关，但仍可以从指数PDF中选择随机数据。
If pulse-to-pulsefrequency agility was used with a frequency step exceeding the 30 MHz dictatedby Eq. (2.63), the RCS of each individual pulse would be expected to beuncorrelated with all of the other pulses, though still drawn from theexponential PDF.
通常在雷达中，当一组非相干组合的N个测量值彼此完全相关，但与随后的一组新的N个测量值不相关时，它们被称为扫描间去相关。
Traditionally inradar, when a set of N measurements that are to be noncoherently combined arecompletely correlated with one another but are uncorrelated with a subsequent,new set of N measurements, they are said to exhibit scan-to-scan decorrelation.
当每个单独的测量值与所有其它测量值不相关时，就说它们之间显示出脉冲间去相关。
When each individualmeasurement is uncorrelated with all of the others, they are said to exhibitpulse-to-pulse decorrelation.
这个术语可能来源于图2.15a中的场景。
This terminologyprobably originates from scenarios like that of Fig. 2.15a.
进行组合的N个测量值是从经过目标的雷达扫描中获得的N个脉冲。
The N measurements tobe combined are the N pulses obtained from one scan of the radar past thetarget.
如果目标移动得足够慢，一次扫描中的N个脉冲将反射相同的RCS值，但移动速度足够快，以至于当雷达扫描一整圈并再次返回照射目标时，下一组N个脉冲将反射不同的RCS值，则术语“扫描间去相关”的描述非常贴切。
If the target movesslowly enough that the N pulses from one scan reflect the same RCS value, butfast enough that by the time the radar scans through a full circle and returnsto the target again the next group of N pulses reflects a different RCS value,then the term “scan-to-scan decorrelation” would be very descriptive.
如果使用频率捷变或雷达目标运动和数据采集时间使每个脉冲回波显示出不同的RCS值，则术语“脉冲间去相关”将是合适的。
If frequency agilitywere used or radar target motion and collection time were such that each pulseexhibits a different RCS value, the term “pulse-to-pulsedecorrelation” would be apt.
“扫描与扫描之间”和“脉冲与脉冲之间”的术语在使用非相干积累的雷达性能分析中有着悠久的历史。
The"scan-to-scan" and “pulse-to-pulse” terminology has a longlegacy in performance analysis of radars using noncoherent integration.
这些术语在许多经典文献中被使用，但在现代相干雷达中，它往往与实际使用的数据采集和处理方法不太相关。
It is used in much ofthe classical literature, but in modern coherent radars it often does notrelate well to the actual data collection and processing methods used.
——本文译自Mark A. Richards所著的《Fundamentals of Radar Signal Processing（Second edition）》
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