# Fwd: Upper Sideband Demodulation

**URL:** <https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721>\
**Category:** GNU Radio\
**Created:** [January 6, 2015, 8:03am UTC](https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721 "2015-01-06T08:03:56Z")\
**Posts on this page:** 5\
**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:** [January 6, 2015, 8:03am UTC](https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721/1 "2015-01-06T08:03:56Z")

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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

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**Author:** ![Wenbin\_Toh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/b9e5f3/32.png) [@Wenbin\_Toh](https://www.ruby-forum.com/u/Wenbin_Toh)\
**Post date:** [January 6, 2015, 9:10am UTC](https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721/2 "2015-01-06T09:10:06Z")

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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

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**Author:** ![Wenbin\_Toh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/b9e5f3/32.png) [@Wenbin\_Toh](https://www.ruby-forum.com/u/Wenbin_Toh)\
**Post date:** [January 7, 2015, 3:21pm UTC](https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721/3 "2015-01-07T15:21:09Z")

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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

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**Author:** ![Wenbin\_Toh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/b9e5f3/32.png) [@Wenbin\_Toh](https://www.ruby-forum.com/u/Wenbin_Toh)\
**Post date:** [January 7, 2015, 3:33pm UTC](https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721/4 "2015-01-07T15:33:37Z")

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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 😉 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

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<div class="post-metadata">

**Author:** ![Wenbin\_Toh](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/b9e5f3/32.png) [@Wenbin\_Toh](https://www.ruby-forum.com/u/Wenbin_Toh)\
**Post date:** [January 8, 2015, 1:44am UTC](https://www.ruby-forum.com/t/fwd-upper-sideband-demodulation/233721/5 "2015-01-08T01:44:11Z")

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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