Hi Yan,
The threshold block converts your signal to 1 if you've been above the "high" value, unless it has fallen below "low" again. Everywhere else, it's 0. See the "documentation" tab in the block properties, or the GNU Radio doxygen manual [1]. But: Parseval's theorem states that energy in frequency and in time domain are directly proportional, so your stream to vector -> FFT->complex to mag²-> vector to stream>moving average can simply be replaced with a complex to mag²->moving average if detecting the average energy in your signal is all you want , which seems probable, seeing that length(average)≈length(FFT). I'm not quite sure what your original intention was when storing (FFT->mag²->average) samples in test_sensor/out.dat; the signal after moving averaging is neither really frequency nor time domain. Out of curiosity: what do you want with that data? There's very valid applications for frequency domain filters (a moving average is actually but a low pass FIR filter, in principle), but the convolution that filtering usually means is often replaced with a multiplication in time domain, which is much less CPU-intense and mathematically equivalent! Best regards, Marcus [1] https://gnuradio.org/doc/doxygen/classgr_1_1blocks_1_1threshold__ff.html#details ¹ For new applications, I recommend Qt rather than WX -- the latter isn't going to be around forever. On 12.02.2016 12:02, Yan Huang wrote: > > Hi all, > > > > I’m using USRP B210 to do spectrum sensing, and the flow graph as > attached file. It can get a result that there is a peak at 5.8 GHz > which is the receiving signal frequency. > > > > But if I change the Moving Average block to a threshold, there is no > output like previous one. > > > > I want to ask how can I get a result have a peak at 5.8 GHz in > frequency domain using threshold. I can only get 1 or 0 in time domain > not in frequency domain. > > > > Is there anyone can give me some advice? Thanks in advance. > > > > > > Yours Sincerely > > > > Yan > > > > This message and any attachment are intended solely for the addressee > and may contain confidential information. If you have received this > message in error, please send it back to me, and immediately delete it. > > Please do not use, copy or disclose the information contained in this > message or in any attachment. Any views or opinions expressed by the > author of this email do not necessarily reflect the views of the > University of Nottingham. > > This message has been checked for viruses but the contents of an > attachment may still contain software viruses which could damage your > computer system, you are advised to perform your own checks. Email > communications with the University of Nottingham may be monitored as > permitted by UK legislation. > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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