# Costas loop in HRPT receiver

**URL:** <https://www.ruby-forum.com/t/costas-loop-in-hrpt-receiver/241189>\
**Category:** GNU Radio\
**Created:** [May 16, 2014, 6:02pm UTC](https://www.ruby-forum.com/t/costas-loop-in-hrpt-receiver/241189 "2014-05-16T18:02:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\
**Post date:** [May 16, 2014, 6:02pm UTC](https://www.ruby-forum.com/t/costas-loop-in-hrpt-receiver/241189/1 "2014-05-16T18:02:26Z")

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Hello,

Ive heard about costas loop to obtain the carrier of a PSK signal. But I  
dont know how it is implemented the carrier recovery in the hrpt example  
of  
gr-noaa in order to demodulate the BPSK signal. I would appreciate some  
help  
with this topic.

Regards,

Pablo.

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**Author:** ![pablo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/ad7895/32.png) [@pablo](https://www.ruby-forum.com/u/pablo)\
**Post date:** [May 19, 2014, 3:03pm UTC](https://www.ruby-forum.com/t/costas-loop-in-hrpt-receiver/241189/2 "2014-05-19T15:03:11Z")

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On Fri, May 16, 2014 at 12:00 PM, Pablo Fernández Alonso \<  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)\> wrote:

> Regards,
> 
> Pablo.

Pablo,

The Costas loop is implemented using a standard second-order control  
loop,  
which means it tracks the phase and the phase change (frequency). You  
can  
find more about how these loops here (and in plenty of text books on  
phase  
locked loops and such):

> **[Control Loop Gain Values — Rondeau Research](http://www.trondeau.com/blog/2011/8/13/control-loop-gain-values.html)**
>
> I have recently been working on updating our digital modulation capabilities in GNU Radio. This has involved making a gr-digital namespace, moving all relevant digital modulation work over, and going through and fixing up a number of the algorithms....

Tom