# Pi/4 Mod-Demod

**URL:** <https://www.ruby-forum.com/t/pi-4-mod-demod/232460>\
**Category:** GNU Radio\
**Created:** [October 10, 2014, 12:06pm UTC](https://www.ruby-forum.com/t/pi-4-mod-demod/232460 "2014-10-10T12:06:54Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [October 10, 2014, 12:06pm UTC](https://www.ruby-forum.com/t/pi-4-mod-demod/232460/1 "2014-10-10T12:06:54Z")

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All,

I’m interested in, and looking into the Pi/4 QPSK modulation technique  
([Phase-shift keying - Wikipedia](http://en.wikipedia.org/wiki/Phase-shift_keying#.CF.80_.2F4.E2.80.93QPSK)).

Has anyone worked on this before and does anyone have any blocks or code  
that I could use for reference while making my own? Any help, links,  
blocks or code would be greatly appreciated!

Thanks,  
Luke

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**Author:** ![PEEL\_Luke](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/9fc29f/32.png) [@PEEL\_Luke](https://www.ruby-forum.com/u/PEEL_Luke)\
**Post date:** [October 10, 2014, 12:13pm UTC](https://www.ruby-forum.com/t/pi-4-mod-demod/232460/2 "2014-10-10T12:13:55Z")

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Hi,

> I’m interested in, and looking into the Pi/4 QPSK modulation technique  
> ([Phase-shift keying - Wikipedia](http://en.wikipedia.org/wiki/Phase-shift_keying#.CF.80_.2F4.E2.80.93QPSK)).
> 
> Has anyone worked on this before and does anyone have any blocks or code  
> that I could use for reference while making my own? Any help, links, blocks  
> or code would be greatly appreciated!

Just rotate it by pi/4 using a rotator block, then treat it as QPSK  
(for which there are GR blocks).

It’s not a GR block but I work with pi/4 whithin the osmo-gmr project.

What’s the target application ? Is it bursts or a continuous signal ?

Cheers,

Sylvain

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**Author:** ![PEEL\_Luke](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/9fc29f/32.png) [@PEEL\_Luke](https://www.ruby-forum.com/u/PEEL_Luke)\
**Post date:** [October 10, 2014, 12:16pm UTC](https://www.ruby-forum.com/t/pi-4-mod-demod/232460/3 "2014-10-10T12:16:50Z")

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Osmo-Tetra uses Pi/4-DQPSK:

> **[Osmo-tetra - OsmocomTETRA - Open Source Mobile Communications](https://osmocom.org/projects/tetra/wiki/osmo-tetra)**
>
> Redmine

Mike

–  
Mike J. M0MIK BSc MIET  
Email: removed\_email\_address@domain.invalid  
Web: [http://scanoo.com](http://scanoo.com)

On Fri, Oct 10, 2014 at 11:05 AM, PEEL Luke  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)