Hi all, I've been slowly working to understand/isolate an issue with a strange voltage pulse at all freqs and on USRP N210 with 50 Ohm load.
I posted about it on StackExchange here, and there are more details at this link: http://stackoverflow.com/questions/27968237/semi-consistent-voltage-pulse-from-usrp-when-using-simple-gnu-radio-flowgraph Since then, I've further isolated it as a UHD issue by completely removing the GNU Radio scheduler from the equation and simply using the finite_acquisition function on UHD to pull samples directly into Python. Here is the code I'm using to produce this output http://i.imgur.com/c3YWA22.png: An interesting thing is that when using the UHD driver is used outside a flowgraph (uhd.finite_acquisition), I get the strange pulse consistently, whereas when used in a flowgraph it was inconsistent (see the StackExchange question). import numpy as np import matplotlib.pyplot as plt FREQ = 800e6 RATE = 1e6 NSAMPS = 100 usrp = uhd.usrp_source(device_addr="", stream_args=uhd.stream_args('fc32')) usrp.set_center_freq(FREQ) usrp.set_samp_rate(RATE) fig, (freqplot, timeplot) = plt.subplots(2, sharex=True) freqplot.set_title("Frequency domain") timeplot.set_title("Time domain") def plot(): data = np.array(usrp.finite_acquisition(NSAMPS)) shifted_fft = np.fft.fftshift(np.fft.fft(data)) dBm = 20*np.log10(np.abs(shifted_fft)) - 30 freqplot.plot(dBm) timeplot.plot(np.abs(data)) def run_tb(times=25): for _ in range(times): plot() plt.show(block=False) Douglas Anderson | Intern DOC/NTIA/ITS-T | 325 Broadway St., Boulder, CO 80305 | P: 303 497 3582
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