iqbal: Import new module to deal with IQ balance correction/optimization
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
parent
f352adfde5
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@ -18,6 +18,9 @@ AM_CONDITIONAL(HAVE_DOXYGEN, test $DOXYGEN != false)
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AC_CONFIG_MACRO_DIR([m4])
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dnl checks for libraries
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PKG_CHECK_MODULES(FFTW3F, fftw3f >= 3.2.0)
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dnl checks for header files
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AC_CHECK_HEADERS([complex.h fcntl.h math.h stdio.h stdlib.h string.h unistd.h sys/mman.h sys/types.h sys/stat.h],,
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AC_MSG_ERROR([Missing required header files.]))
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@ -1,3 +1,3 @@
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osmodsp_HEADERS = cfile.h cxvec.h cxvec_math.h
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osmodsp_HEADERS = cfile.h cxvec.h cxvec_math.h iqbal.h
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osmodspdir = $(includedir)/osmocom/dsp
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@ -0,0 +1,77 @@
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/*
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* iqbal.h
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*
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* IQ balance correction / estimation utilities
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*
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* Copyright (C) 2013 Sylvain Munaut <tnt@246tNt.com>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef __OSMO_DSP_IQBAL_H__
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#define __OSMO_DSP_IQBAL_H__
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/*! \defgroup iqbal IQ balance utilities
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* @{
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*/
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/*! \file iqbal.h
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* \brief Osmocom IQ balance utils header
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*/
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#include <complex.h>
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#include <osmocom/dsp/cxvec.h>
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/* IQ balance correction and estimation */
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void osmo_iqbal_fix(float complex *out, float complex *in, unsigned int len,
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float mag, float phase);
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struct osmo_cxvec *
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osmo_iqbal_cxvec_fix(const struct osmo_cxvec *in, float mag, float phase,
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struct osmo_cxvec *out);
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float
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osmo_iqbal_estimate(const float complex *data,
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int fft_size, int fft_count);
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float
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osmo_iqbal_cxvec_estimate(const struct osmo_cxvec *sig,
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int fft_size, int fft_count);
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/* IQ balance optimization */
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/*! \brief Processing options for the IQ balance optimization algorithm */
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struct osmo_iqbal_opts {
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int fft_size; /*!< \brief FFT size to use */
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int fft_count; /*!< \brief Number of FFT to use */
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int max_iter; /*!< \brief Max # iterations per pass */
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int start_at_prev; /*!< \brief Use prev values as starting point */
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};
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extern const struct osmo_iqbal_opts osmo_iqbal_default_opts;
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int
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osmo_iqbal_cxvec_optimize(const struct osmo_cxvec *sig, float *mag, float *phase,
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const struct osmo_iqbal_opts *opts);
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/*! @} */
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#endif /* __OSMO_DSP_IQBAL_H__ */
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@ -3,9 +3,9 @@
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LIBVERSION=0:0:0
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INCLUDES = $(all_includes) -I$(top_srcdir)/include
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AM_CFLAGS = -Wall -ffast-math
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AM_CFLAGS = -Wall -ffast-math $(FFTW3F_CFLAGS)
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lib_LTLIBRARIES = libosmodsp.la
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libosmodsp_la_SOURCES = cfile.c cxvec.c cxvec_math.c
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libosmodsp_la_LDFLAGS = -version-info $(LIBVERSION)
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libosmodsp_la_SOURCES = cfile.c cxvec.c cxvec_math.c iqbal.c
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libosmodsp_la_LDFLAGS = -version-info $(LIBVERSION) $(FFTW3F_LIBS)
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@ -0,0 +1,301 @@
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/*
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* iqbal.c
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*
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* IQ balance correction / estimation utilities
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*
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* Copyright (C) 2013 Sylvain Munaut <tnt@246tNt.com>
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*
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/*! \addtogroup iqbal
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* @{
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*/
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/*! \file iqbal.c
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* \brief IQ balance utils implementation
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*/
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#include <complex.h>
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#include <stdlib.h>
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#include <string.h>
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#include <fftw3.h>
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#include <osmocom/dsp/cxvec.h>
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#include <osmocom/dsp/cxvec_math.h>
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#include <osmocom/dsp/iqbal.h>
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/* ------------------------------------------------------------------------ */
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/* IQ balance correction and estimation */
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/* ------------------------------------------------------------------------ */
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/*! \brief Apply IQ balance correction to a given complex buffer
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* \param[out] out Complex output buffer
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* \param[in] in Complex input buffer
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* \param[in] len Number of complex samples to process
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* \param[in] mag Magnitude correction (approximated)
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* \param[in] phase Phase correction (approximated)
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*
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* The input and output buffers can be the same for in-place modification.
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*
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* The exact applied is out[i] = (a * (1 + mag)) + (b + phase * a) * i
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* (with in[i] = a+bi).
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*/
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void
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osmo_iqbal_fix(float complex *out, float complex *in, unsigned int len,
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float mag, float phase)
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{
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int i;
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for (i=0; i<len; i++) {
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float complex v = in[i];
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out[i] = (crealf(v) * (1.0f + mag)) +
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(cimagf(v) + phase * crealf(v)) * I;
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}
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}
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/*! \brief Apply IQ balance correction to a given complex vector
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* \param[in] in Complex input vector
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* \param[in] mag Magnitude correction (approximated)
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* \param[in] phase Phase correction (approximated)
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* \param[out] out Complex output vector (can be NULL or equal to 'in')
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* \returns The output complex vector (or NULL if error)
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*
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* If the 'out' parameter is NULL, a new vector will be allocated
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* See \ref osmo_iqbal_fix for details of the correction applied.
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*/
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struct osmo_cxvec *
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osmo_iqbal_cxvec_fix(const struct osmo_cxvec *in, float mag, float phase,
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struct osmo_cxvec *out)
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{
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if (!out)
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out = osmo_cxvec_alloc(in->len);
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if (!out || out->max_len < in->len)
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return NULL;
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osmo_iqbal_fix(out->data, in->data, in->len, mag, phase);
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out->len = in->len;
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out->flags = in->flags;
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return out;
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}
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/*! \brief Objectively estimate IQ balance in a given complex buffer
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* \param[in] data Input complex buffer (at least fft_size * fft_count samples)
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* \param[in] fft_size Size of the FFT to use internally
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* \param[in] fft_count The number of consecutive FFT to use internally
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* \returns A number >= 0.0f estimating the IQ balance (the lower, the better)
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*/
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float
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osmo_iqbal_estimate(const float complex *data, int fft_size, int fft_count)
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{
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float complex *fft;
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float est = 0.0f;
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fftwf_plan fft_plan;
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int i, j;
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fft = malloc(sizeof(float complex) * fft_size);
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fft_plan = fftwf_plan_dft_1d(fft_size, fft, fft, FFTW_FORWARD, FFTW_ESTIMATE);
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for (i=0; i<fft_count; i++)
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{
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float complex corr = 0.0f;
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memcpy(fft, &data[i*fft_size], sizeof(float complex) * fft_size);
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fftwf_execute(fft_plan);
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for (j=1; j<fft_size/2; j++)
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corr += fft[fft_size-j] * conjf(fft[j]);
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est += osmo_normsqf(corr); /* / (fft_size / 2); */
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}
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/* est /= fft_count; */
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fftwf_destroy_plan(fft_plan);
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free(fft);
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return est;
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}
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/*! \brief Objectively estimate IQ balance in a given complex vector
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* \param[in] sig Input complex vector (at least fft_size * fft_count samples)
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* \param[in] fft_size Size of the FFT to use internally
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* \param[in] fft_count The number of consecutive FFT to use internally
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* \returns A number >= 0.0f estimating the IQ balance (the lower, the better)
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*/
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float
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osmo_iqbal_cxvec_estimate(const struct osmo_cxvec *sig,
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int fft_size, int fft_count)
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{
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if (sig->len < fft_size * fft_count)
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return -1.0f;
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return osmo_iqbal_estimate(sig->data, fft_size, fft_count);
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}
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/* ------------------------------------------------------------------------ */
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/* IQ balance optimization */
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/* ------------------------------------------------------------------------ */
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/*! \brief Default values for the optimization algorithm */
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const struct osmo_iqbal_opts osmo_iqbal_default_opts = {
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.fft_size = 1024,
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.fft_count = 8,
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.max_iter = 25,
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.start_at_prev = 1,
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};
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/*! \brief Internal state structure for the IQ balance optimization algorithm */
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struct _iqbal_state
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{
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const struct osmo_iqbal_opts *opts; /*!< \brief Options */
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const struct osmo_cxvec *org; /*!< \brief Original vector */
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struct osmo_cxvec *tmp; /*!< \brief Temporary vector */
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int feval; /*!< \brief # of function evaluation */
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};
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/*! \brief Optimization objective function - Value
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* \param[in] state Current state object of optimization loop
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* \param[in] x An array of 2 float for (mag,phase) point to evaluate at
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* \returns The value of the objective function at point 'x'
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*/
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static inline float
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_iqbal_objfn_value(struct _iqbal_state *state, float x[2])
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{
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state->feval++;
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osmo_iqbal_cxvec_fix(state->org, x[0], x[1], state->tmp);
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return osmo_iqbal_cxvec_estimate(state->tmp,
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state->opts->fft_size, state->opts->fft_count);
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}
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/*! \brief Optimization objective function - Gradient estimation
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* \param[in] state Current state object of optimization loop
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* \param[in] x An array of 2 float for (mag,phase) point to evaluate at
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* \param[in] v The value of the objective function at point 'x'
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* \param[out] grad An array of 2 float for the estimated gradient at point 'x'
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*/
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static void
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_iqbal_objfn_gradient(struct _iqbal_state *state, float x[2], float v, float grad[2])
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{
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#define GRAD_STEP 0.001f
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float xd[2], vd[2];
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xd[0] = x[0] + GRAD_STEP; xd[1] = x[1];
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vd[0] = _iqbal_objfn_value(state, xd);
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xd[0] = x[0]; xd[1] = x[1] + GRAD_STEP;
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vd[1] = _iqbal_objfn_value(state, xd);
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grad[0] = (vd[0] - v) / GRAD_STEP;
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grad[1] = (vd[1] - v) / GRAD_STEP;
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}
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/*! \brief Optimization objective function - Value & Gradient estimation
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* \param[in] state Current state object of optimization loop
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* \param[in] x An array of 2 float for (mag,phase) point to evaluate at
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* \param[out] grad An array of 2 float for the estimated gradient at point 'x'
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* \returns The value of the objective function at point 'x'
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*/
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static inline float
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_iqbal_objfn_val_gradient(struct _iqbal_state *state, float x[2], float grad[2])
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{
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float v = _iqbal_objfn_value(state, x);
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_iqbal_objfn_gradient(state, x, v, grad);
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return v;
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}
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/*! \brief Finds the best IQ balance correction parameters for a given signal
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* \param[in] sig The input signal to optimize for
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* \param[in,out] mag Magnitude correction (See \ref osmo_iqbal_fix)
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* \param[in,out] phase Phase correction (See \ref osmo_iqbal_fix)
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* \param[in] opts Options of the optimization process (See \ref osmo_iqbal_opts)
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*
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* The mag and phase parameters are pointers to float. If in the options,
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* the 'start_at_prev' is enabled, the initial values of those will be used
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* and so they should be initialized appropriately.
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*/
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int
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osmo_iqbal_cxvec_optimize(const struct osmo_cxvec *sig, float *mag, float *phase,
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const struct osmo_iqbal_opts *opts)
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{
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struct _iqbal_state _state, *state = &_state;
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float cv, nv, step;
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float cx[2], nx[2];
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float cgrad[2];
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float p;
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int i;
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if (!opts)
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opts = &osmo_iqbal_default_opts;
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if (sig->len < (opts->fft_size * opts->fft_count))
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return -1;
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state->org = sig;
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state->tmp = osmo_cxvec_alloc(sig->len);
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state->opts = opts;
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state->feval = 0;
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if (opts->start_at_prev) {
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cx[0] = *mag;
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cx[1] = *phase;
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} else {
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cx[0] = 0.0f;
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cx[1] = 0.0f;
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}
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cv = _iqbal_objfn_val_gradient(state, cx, cgrad);
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step = 0.1f * cv / (fabs(cgrad[0]) + fabs(cgrad[1]));
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for (i=0; i<opts->max_iter; i++)
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{
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nx[0] = cx[0] - step * cgrad[0];
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nx[1] = cx[1] - step * cgrad[1];
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nv = _iqbal_objfn_value(state, nx);
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if (nv < cv) {
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p = (cv - nv) / cv;
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if (p < 0.01f)
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break;
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cx[0] = nx[0];
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cx[1] = nx[1];
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cv = nv;
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_iqbal_objfn_gradient(state, cx, cv, cgrad);
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} else {
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step /= 2.0f;
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}
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}
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osmo_cxvec_free(state->tmp);
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*mag = cx[0];
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*phase = cx[1];
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return 0;
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}
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/*! @} */
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