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Why does Costa's loop PLL bandwidth need to be narrow? Text books mention that and yet give no explanation


marked as duplicate by lennon310, Marcus Müller, jojek Jul 30 '18 at 15:58

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The main purpose of a phase synchronization system, whether Costas loop or a PLL, is to track the phase of an input signal. The bandwidth of a PLL determines whether the signal falls within the range it can track or suppress. If the signal can pass through and the bandwidth is narrow, less noise enters the system increasing the loop SNR, while a wider bandwidth allows more noise deteriorating the tracking performance. But do remember that the narrower the bandwidth, the longer the acquisition time due to the smaller variation injected by the PLL.

  • $\begingroup$ Thank Qasim. So what are the loop BW limitations as far as frequency tracking and data rates are concerned? $\endgroup$ – Hatem Tawfik Jul 29 '18 at 21:09
  • $\begingroup$ This is highly dependent on the system you need to design. Roland Best's PLL book is a good reference to start with. $\endgroup$ – Qasim Chaudhari Jul 30 '18 at 1:25

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