Re: Determining peak instantaneous power in waveform
Hi Ron -- Your papr.c program looks like it will do just what I want. I'll grab it. Thanks again for the help you provide! John On 5/18/22 00:23, Ron Economos wrote: I have a block that may be useful for you. It just prints the peak IQ level. It's usually placed just before a hardware sink block. https://github.com/drmpeg/gr-iqlevels The output looks like this: peak real = +1.631239e-01, -1.961090e-01, 0, 0 peak imag = +2.698523e-01, -1.962542e-01, 0, 0 It's printing the maximum I and Q level in both positive and negative directions and the total number of times they exceeded +/- 1.0. I also have an offline program that does PAPR calculations. It just takes a float IQ file as input. https://github.com/drmpeg/dtv-utils/blob/master/papr.c The output looks like this: Peak magnitude = 0.869561 average power = 0.040009514, peak power = 0.756135583 @ 121986288 Maximum PAPR = 12.764364 percentage above 0 dB = 36.79375350 percentage above 1 dB = 28.40112150 percentage above 2 dB = 20.49609423 percentage above 3 dB = 13.58977407 percentage above 4 dB = 8.10234174 percentage above 5 dB = 4.22610082 percentage above 6 dB = 1.86289176 percentage above 7 dB = 0.66361316 percentage above 8 dB = 0.18129208 percentage above 9 dB = 0.03537920 percentage above 10 dB = 0.00439378 percentage above 11 dB = 0.00032525 percentage above 12 dB = 0.1121 peak real positive = 0.840840, peak imaginary positive = 0.798450 peak real negative = -0.791407, peak imaginary negative = -0.821772 peak real positive @ 1703752736, peak imaginary positive @ 1624430697 peak real negative @ 1846543928, peak imaginary negative @ 2753521145 Ron On 5/17/22 12:44, John Ackermann N8UR wrote: Hi -- I have broadband HF data recorded off the air (ham radio bands 384 kHz wide) and am trying to figure out what sort of gain settings I need to play it back on a USRP without distortion. My worry is the way multiple fairly strong signals could add together in phase to create momentary spikes way higher than the visible average (I think this is called crest factor in digital signals?). Is there a (relatively) straightforward way to measure this with Gnuradio blocks? If so, can anyone point me in the right direction to build a GRC flow graph to read an IQ file and print out the peak instantaneous power seen in the file, relative to 100% (ie, I don't need calibrated numbers, just to know how to set the gain in Gnuradio for undistorted playback). Thanks! John
Re: Determining peak instantaneous power in waveform
I have a block that may be useful for you. It just prints the peak IQ level. It's usually placed just before a hardware sink block. https://github.com/drmpeg/gr-iqlevels The output looks like this: peak real = +1.631239e-01, -1.961090e-01, 0, 0 peak imag = +2.698523e-01, -1.962542e-01, 0, 0 It's printing the maximum I and Q level in both positive and negative directions and the total number of times they exceeded +/- 1.0. I also have an offline program that does PAPR calculations. It just takes a float IQ file as input. https://github.com/drmpeg/dtv-utils/blob/master/papr.c The output looks like this: Peak magnitude = 0.869561 average power = 0.040009514, peak power = 0.756135583 @ 121986288 Maximum PAPR = 12.764364 percentage above 0 dB = 36.79375350 percentage above 1 dB = 28.40112150 percentage above 2 dB = 20.49609423 percentage above 3 dB = 13.58977407 percentage above 4 dB = 8.10234174 percentage above 5 dB = 4.22610082 percentage above 6 dB = 1.86289176 percentage above 7 dB = 0.66361316 percentage above 8 dB = 0.18129208 percentage above 9 dB = 0.03537920 percentage above 10 dB = 0.00439378 percentage above 11 dB = 0.00032525 percentage above 12 dB = 0.1121 peak real positive = 0.840840, peak imaginary positive = 0.798450 peak real negative = -0.791407, peak imaginary negative = -0.821772 peak real positive @ 1703752736, peak imaginary positive @ 1624430697 peak real negative @ 1846543928, peak imaginary negative @ 2753521145 Ron On 5/17/22 12:44, John Ackermann N8UR wrote: Hi -- I have broadband HF data recorded off the air (ham radio bands 384 kHz wide) and am trying to figure out what sort of gain settings I need to play it back on a USRP without distortion. My worry is the way multiple fairly strong signals could add together in phase to create momentary spikes way higher than the visible average (I think this is called crest factor in digital signals?). Is there a (relatively) straightforward way to measure this with Gnuradio blocks? If so, can anyone point me in the right direction to build a GRC flow graph to read an IQ file and print out the peak instantaneous power seen in the file, relative to 100% (ie, I don't need calibrated numbers, just to know how to set the gain in Gnuradio for undistorted playback). Thanks! John
Determining peak instantaneous power in waveform
Hi -- I have broadband HF data recorded off the air (ham radio bands 384 kHz wide) and am trying to figure out what sort of gain settings I need to play it back on a USRP without distortion. My worry is the way multiple fairly strong signals could add together in phase to create momentary spikes way higher than the visible average (I think this is called crest factor in digital signals?). Is there a (relatively) straightforward way to measure this with Gnuradio blocks? If so, can anyone point me in the right direction to build a GRC flow graph to read an IQ file and print out the peak instantaneous power seen in the file, relative to 100% (ie, I don't need calibrated numbers, just to know how to set the gain in Gnuradio for undistorted playback). Thanks! John
