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发表于 2009-3-30 18:16:30
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loop configurations. The decision-directed loop , exhibits a 2 -dB sensitivity im-
provement as compared to other types of PLLs. Bandwidth and root deviation caused by
bilinear or boxcar transforms are solved by implementing a root-controled method. Using
this design makes the bandwidth of the digital loop close to desired values, and thus im-
proves carrier tracking by another 1 to 2 dB. A Kalman Filter adopts a soft-mode to deal
with the bit sign uncertainty and adjusts the bandwidth to minimize the mean square car-
rier tracking error. This leads to a 4 dB and 7 dB sensitivity improvement during weak
and strong amplitude ionospheric scintillations, respectively. |
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