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/*
* File psdcmean.c
*
* Calculates mean powerspectrum of complex input data
* using blocklength lblock and nblocks as number
* of blocks to be processed.
*
* Author M.Bos - PA0MBO
* Date Feb 21st 2009
*
* resulting power spectral density of complex input
* signal in rsbuf is stored in cpsd[]
* length of datablock to be processed is lblock
* nblocks is the nuber of blocks of input data
* to be processed.
*
*/
/*************************************************************************
*
* PA0MBO
*
* COPYRIGHT (C) 2009 M.Bos
*
* This file is part of the distribution package RXAMADRM
*
* This package is free software and you can redistribute is
* and/or modify it under the terms of the GNU General Public License
*
* More details can be found in the accompanying file COPYING
*************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <sys/types.h>
#include <malloc.h>
void cfft(float *, int, int);
void psdcmean(float *rsbuf, float *cpsd, int lblock, int nblocks)
{
float *pinput;
int i, j;
float tmpinbuf[2048];
float result[512];
/* check space */
if (lblock > 1024)
{
printf("not enough temp space\b");
exit(EXIT_FAILURE);
}
/* clear array result before accumulating new data */
for (i = 0; i < (lblock / 2); i++)
{
result[i] = 0.0;
}
/* loop over all blocks taking care to keep track of ptr in input */
pinput = rsbuf;
for (j = 0; j < nblocks; j++)
{
/* Now fill tmpinbuf with converted data from input */
for (i = 0; i < lblock; i++)
{
tmpinbuf[i * 2] = pinput[2 * i];
tmpinbuf[i * 2 + 1] = pinput[2 * i + 1];
}
cfft(tmpinbuf, lblock / 2, 1);
for (i = 1; i < lblock / 2; ++i)
{
result[i] +=
sqrt(tmpinbuf[i * 2] * tmpinbuf[i * 2] +
tmpinbuf[i * 2 + 1] * tmpinbuf[i * 2 + 1]);
}
pinput += 2 * lblock; /* update pointer in input data */
}
for (i = 0; i < lblock / 2; i++)
{
result[i] = (float) (10.0 * log(result[i] + 1.0e-8) / 2.305 - 14.0);
}
/* interchange halfs of cpsd buffer as in matlab code from
plot_input_spectrum in diorama */
for (i = 1; i < lblock / 4; i++)
{
cpsd[i] = result[lblock / 4 + i];
cpsd[i + lblock / 4 - 1] = result[i];
}
}
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