Difference between revisions of "Costas Loop"

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== Example Flowgraph ==
== Example Flowgraph ==
Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI.  Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately.  The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.
See [[Guided_Tutorial_PSK_Demodulation#Phase_and_Fine_Frequency_Correction]]
== Source Files ==
== Source Files ==

Latest revision as of 13:22, 6 June 2020

A Costas loop carrier recovery module, great for synchronizing to BPSK, QPSK, and 8PSK. The Costas loop locks to the center frequency of a signal and downconverts it to baseband.

  • When order=2: used for BPSK where the real part of the output signal is the baseband BPSK signal and the imaginary part is the error signal.
  • When order=4: can be used for QPSK where both I and Q (real and imaginary) are outputted.
  • When order=8: used for 8PSK.

The Costas loop can have two output streams:

  1. stream 1 (required) is the baseband I and Q;
  2. stream 2 (optional) is the normalized frequency of the loop

There is a single optional message input for a noise floor estimate used to calculate the SNR of a sample.

More details can be found online:

J. Feigin, "Practical Costas loop design: Designing a simple and inexpensive BPSK Costas loop carrier recovery circuit," RF signal processing, pp. 20-36, 2002.


(R): Run-time adjustable

Loop Bandwidth (R)
Internal 2nd order loop bandwidth (~ 2pi/100)
The loop order, either 2, 4, or 8, see above.
Use or ignore SNR estimates (from noise message port) in measurements; also uses tanh instead of slicing.

Example Flowgraph[edit]

See Guided_Tutorial_PSK_Demodulation#Phase_and_Fine_Frequency_Correction

Source Files[edit]

C++ files
Header files
Public header files
Block definition