Re: [Discuss-gnuradio] CPFSK mod/demod + strange behavior

Sorry for the inconvenience,

1 - Yes I tried, BUT ! the only way I manage to make this works is by plugging the following blocks : File source -> RS encoder -> packed to unpacked -> CPFSK -> Quad demod -> binary slicer -> unpacked to packed -> RS Decoder -> File sink . All of this work only if I set Samples/symbols to 1 in the CPFSK block. I've been told before that it cannot work like this on a real transmission because with Samples/symbols set to 1, you can't do any pulse shaping.

2- look at the pic joined in this e-mail. I don't understand why there's only one spike in the spectrum???

3 - I need +/-312.5 kHz of deviation with a modulation index of 0,6. I need a bit rate of 1041667 Mbps. I set a sampling rate of 6.25 M only because it's 6 times the bit rate so, samples/symbols in CPFSK block will be set to 6.

All this is due to the spec sheets of the UAT I'm trying to develop. This is the aviation industry's standards and I need to respect them to be approved. If someone would like to see the specs, I have a PDF that explains it all and I would be glad to share it with you !

Thank you

Olivier

2016-06-09 11:37 GMT-04:00 Marcus Müller <address@hidden>:

Hi Olivier,

trying to catch up with you here. I've got a few questions! Please excuse if they've been answered by you before; it's not really easy to navigate your emails – hint: it gets easier for us to help you if you use the "reply" button in your email client, so that things get clearly sorted into some kind of discussion thread. Also, less emails with condensed questions might be easier to get answers to. You see, I think very few of us currently get the "big picture".

Have you verified this works in a simulation-only environment, ie. when you replace the USRP sink/source with a direct GNU Radio stream?

Can you post a comparison of Spectrum after the CPFSK modulator (before the RRC) and after the RRC? Just to verify the low-pass characteristics of that pulse shaper don't "eat" the FSK.

Could you enlighten us a bit about your design goals, i.e. what's the frequency deviation you want to achieve with the CPFSK?

Best regards,
Marcus

On 09.06.2016 16:50, Olivier Goyette wrote:
There's something wrong at Tx again. Look at the waterfall I joined, we only see one stripe at -312.5 kHz and the signal seems to be going like on/off. Don't know what's going on ??
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From:	Olivier Goyette
Subject:	Re: [Discuss-gnuradio] CPFSK mod/demod + strange behavior
Date:	Thu, 9 Jun 2016 11:59:56 -0400