Bfsk

GNU Radio
1

Would someone please recommend a book that steps through the
implementation
used in GNU Radio for the Frequency Mod and Quadrature Mod blocks? I’ve
looked at the source code and I have seen posts trying to explain what
sensitivity and gain are, but my lack of background knowledge is making
those sources not very helpful.

Really appreciated,
Rich

2

Hi Richard,

I suffered through understanding the quadrature mod/demod block settings
a
while back. I provide some links to that information below. I provide
a
formula for the settings for both digital and audio applications. As
you
can see (from the reading), the settings can be derived from
samples-per-symbol and modulation index or deviation and baud rate. Or
just peak deviation and sample rate for audio.

The quadrature demod gain is really just a gain, btw. If you set it
right,
your demodulated audio will have unity gain, which is nice/necessary for
most of the clock synchronizers.

Thread:
http://lists.gnu.org/archive/html/discuss-gnuradio/2013-07/msg00058.html
Wiki Summary:
http://gnuradio.org/redmine/projects/gnuradio/wiki/SignalProcessing

Very Respectfully,

Dan CaJacob

On Mon, Nov 17, 2014 at 2:09 PM, Richard B. [email protected]

3

If you’re interested in the workings of the CPM modulators (but it seems
like Dan’s response might be more appropriate), a very complete
description can be found in “Anderson, Aulin and Sundberg; Digital Phase
Modulation”, as quoted in
http://gnuradio.org/doc/doxygen/classgr_1_1analog_1_1cpm.html#ab9e2018801fc5c8a82c02226a9cadceb

M

4

On Mon, Nov 17, 2014 at 11:09:14AM -0800, Richard B. wrote:

Would someone please recommend a book that steps through the
implementation used in GNU Radio for the Frequency Mod and Quadrature
Mod blocks?

I discuss the algorithm implemented in the Quadrature Demod block in
this video:

http://greatscottgadgets.com/sdr/7

If you aren’t very familiar with complex numbers, you may want to watch
this one first:

http://greatscottgadgets.com/sdr/6

I’ve looked at the source code and I have seen posts trying to explain
what sensitivity and gain are

It’s a scaling of the output of the demodulator (or the input of the
modulator).

Mike