Costas Loop

A Costas loop carrier recovery module. 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.

Parameters

(R): Run-time adjustable

Loop Bandwidth (R)

Internal 2nd order loop bandwidth (~ 2pi/100)

Order

The loop order, either 2, 4, or 8, see above.

Use SNR

Use or ignore SNR estimates (from noise message port) in measurements; also uses tanh instead of slicing.

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.

Source Files

C++ files

TODO

Header files

TODO

Public header files

TODO

Block definition

TODO