Fwd: Upper Sideband Demodulation

GNU Radio
1

Hi everyone, I have a question regarding the USB demodulation which I
have
conducted on a sample wav file which I have recorded. I would like to
know
if there are any solutions to eliminate the audio underrun issue which
is
shown in attachment “test1”.

I would also like to ask if there are any other better USB demodulation
method other than weaver’s method. Would be great if there is any
feedback
for the USB demodulation which I have done as I feel that there are
something wrong with it which I could not pin-point out.

PS: I am using ettus X310 system, with computer system ubuntu 14.04, UHD
version 3.8.1 and gnuradio version 3.7.6. I am new to gnuradio and is
trying to learn how to apply it to digital signal processing theory.

Thanks in advance for any feedback by you guys.

Regards,
Wen Bin

2

Hi,

I sent you a response just yesterday on the usrp-users mailing list
suggesting you remove the throttle. Did you try that, and did it not
help?

M

3

Hi Martin,

Sorry for the late reply. After reading on throttle usage and removing
the
throttle, it did solve the audio underrun issue. Thanks you.

However, I would also like to know if there are any other better and
efficient USB demodulation method.

Regards,
Wen Bin

4

Hello Wen Bin,

for me, “upper side band” modulation implies the following, assuming
we’re already in complex baseband, with the middle between USB and LSB
shifted to 0 Hz: (imagine this is a frequency axis):

<---- -f_sample/2 — LSB — f_center==0Hz — USB — +f_sample/2
---->

If I understand you correctly, you only want to see positive
frequencies; Weaver’s method (or its inverse) would simply shift USB by
-f_sample/4 and apply a low pass filter or f_sample/4 passband. If the
filtering was done perfectly, then the newly generated complex baseband
signal will contain exactly the information originally in your USB. If
that suits your needs completely depends on what you actually are
transmitting in your USB and what you want to do with it. So: No one can
tell you whether there’s a better method other than you :wink: because you
know what you need.

Regarding efficiency: Doing the frequency shift, the low pass filtering
and a decimation can be done at once using the xlating FIR filter block.
Try it, you’ll like it; it’s heavily optimized.

Greetings,
Marcus

5

Hi Marcus,

Thanks for the advice. I will try it out and see if it will provide the
signal that I need.

Regards,
Wen Bin