Simple symmetrical wave RMS DEMO using awk. Post: 303002987

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Operating Systems OS X (Apple) Simple symmetrical wave RMS DEMO using awk. Post 303002987 by wisecracker on Wednesday 6th of September 2017 09:04:12 AM

09-06-2017

Registered User

Hi JM...
(Thanks for the reply.)
Apologies for any typos, and hope it is lucid enough.

Quote:

Originally Posted by jim mcnamara

It looks to me like you have a granularity problem. Four dots as a sample can fit a lot of functions, with intermediate datapoints from increased sampling rates you could then use fft to get good sine waves, for example.

You can code fft.c then call it using the system() function in awk. I think your awk supports that call.

A google for 'fft.c' got me 10 first page hits that looked respectably good. There are sites with an array of algorithmic variants to meet differing needs.

fft is gold standard for fitting data sampling output.

Apologies for the delay, I have not been around for a while. My triangle wave is more or less hypothetical as sampling a real time random triangle wave that......
1) starts at the 0 point,
2) is initially positive going,
3) has 4 samples, or any number of the same 4 samples,
......is close to impossible.
But a file CAN be so easily be created as shown in the single cycle version in the code.
Although I was aware of the errors that creep in when creating the RMS values I was NOT aware of this one off bizarre situation, (and could find nothing on the WWW about it), so after creating the simple code I made a point of there being a reference to this anomaly.

As the RMS value(s) are near the exact value(s) for that of a sinewave hence my point.

In the days of Debian 6 and PCLinuxOS 2009, (my two main OSes in those days), when '/dev/dsp' was available, recreating the waveforms through '/dev/dsp' would result in a triangle wave as the sound system interpolation was Linear, this was also true for some Windows machines of bygone days. I am not sure what interpolations are used in current OSes and sound systems but it sure looks trigonometric to me, so I would guess that a sinewave would be recreated as a result.

I am happy with the idea of the RMS code at this point but looking more towards True RMS but would probably need to rethink my approach.

But to re-iterate for others, be aware of this anomaly.

LBNL, for any FFT work needed, I would do it through Python and SciPy as the heavy lifting is done already, see previous uploads of AudioScope.sh for the AF Spectrum display...

Bazza...

Last edited by wisecracker; 09-06-2017 at 12:18 PM.. Reason: Modify for error...

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LEARN ABOUT DEBIAN

uhd_siggen

UHD_SIGGEN(1)							   User Commands						     UHD_SIGGEN(1)

NAME

       uhd_siggen - Signal Generator using UHD hardware

SYNOPSIS

       uhd_siggen: [options]

DESCRIPTION

       Command-line signal generator application.

OPTIONS

       -h, --help
	      show this help message and exit

       -a ARGS, --args=ARGS
	      UHD device address args , [default=]

       --spec=SPEC
	      Subdevice of UHD device where appropriate

       -A ANTENNA, --antenna=ANTENNA
	      select Rx Antenna where appropriate

       -s SAMP_RATE, --samp-rate=SAMP_RATE
	      set sample rate (bandwidth) [default=1000000.0]

       -g GAIN, --gain=GAIN
	      set gain in dB (default is midpoint)

       -f FREQ, --tx-freq=FREQ
	      Set carrier frequency to FREQ [default=mid-point]

       -x WAVEFORM_FREQ, --waveform-freq=WAVEFORM_FREQ
	      Set baseband waveform frequency to FREQ [default=0]

       -y WAVEFORM2_FREQ, --waveform2-freq=WAVEFORM2_FREQ
	      Set 2nd waveform frequency to FREQ [default=none]

       --sine Generate a carrier modulated by a complex sine wave

       --const
	      Generate a constant carrier

       --offset=OFFSET
	      Set waveform phase offset to OFFSET [default=0]

       --gaussian
	      Generate Gaussian random output

       --uniform
	      Generate Uniform random output

       --2tone
	      Generate Two Tone signal for IMD testing

       --sweep
	      Generate a swept sine wave

       --amplitude=AMPL
	      Set output amplitude to AMPL (0.0-1.0) [default=0.15]

       -v, --verbose
	      Use verbose console output [default=False]

SEE ALSO

       uhd_siggen_gui(1)

uhd_siggen 3.5							   December 2011						     UHD_SIGGEN(1)