GNU Radio Manual and C++ API Reference
3.9.1.0
The Free & Open Software Radio Ecosystem
quadrature_demod_cf.h
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/* -*- c++ -*- */
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/*
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* Copyright 2004,2012 Free Software Foundation, Inc.
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*
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* This file is part of GNU Radio
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*
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* SPDX-License-Identifier: GPL-3.0-or-later
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*
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*/
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#ifndef INCLUDED_ANALOG_QUADRATURE_DEMOD_CF_H
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#define INCLUDED_ANALOG_QUADRATURE_DEMOD_CF_H
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#include <
gnuradio/analog/api.h
>
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#include <
gnuradio/sync_block.h
>
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namespace
gr
{
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namespace
analog {
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/*!
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* \brief quadrature demodulator: complex in, float out
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* \ingroup modulators_blk
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*
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* \details
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* This can be used to demod FM, FSK, GMSK, etc. The input is complex
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* baseband, output is the signal frequency in relation to the sample
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* rate, multiplied with the gain.
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*
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* Mathematically, this block calculates the product of the one-sample
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* delayed input and the conjugate undelayed signal, and then calculates
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* the argument of the resulting complex number:
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*
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* \f$y[n] = \mathrm{arg}\left(x[n] \, \bar x [n-1]\right)\f$.
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*
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* Let \f$x\f$ be a complex sinusoid with amplitude \f$A>0\f$, (absolute)
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* frequency \f$f\in\mathbb R\f$ and phase \f$\phi_0\in[0;2\pi]\f$ sampled at
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* \f$f_s>0\f$ so, without loss of generality,
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*
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* \f$x[n]= A e^{j2\pi( \frac f{f_s} n + \phi_0)}\f$
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*
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* then
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*
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* \f{align*}{ y[n] &= \mathrm{arg}\left(A e^{j2\pi\left( \frac f{f_s} n + \phi_0\right)}
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* \overline{A e^{j2\pi( \frac f{f_s} (n-1) + \phi_0)}}\right)\\
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* & = \mathrm{arg}\left(A^2 e^{j2\pi\left( \frac f{f_s} n + \phi_0\right)} e^{-j2\pi(
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* \frac f{f_s} (n-1) + \phi_0)}\right)\\
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* & = \mathrm{arg}\left( A^2 e^{j2\pi\left( \frac f{f_s} n + \phi_0 - \frac f{f_s} (n-1)
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* - \phi_0\right)}\right)\\
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* & = \mathrm{arg}\left( A^2 e^{j2\pi\left( \frac f{f_s} n - \frac f{f_s}
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* (n-1)\right)}\right)\\
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* & = \mathrm{arg}\left( A^2 e^{j2\pi\left( \frac f{f_s}
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* \left(n-(n-1)\right)\right)}\right)\\
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* & = \mathrm{arg}\left( A^2 e^{j2\pi \frac f{f_s}}\right) \intertext{$A$ is real, so is
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* $A^2$ and hence only \textit{scales}, therefore $\mathrm{arg}(\cdot)$ is invariant:} &=
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* \mathrm{arg}\left(e^{j2\pi \frac f{f_s}}\right)\\
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* &= \frac f{f_s}\\
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* &&\blacksquare
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* \f}
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*/
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class
ANALOG_API
quadrature_demod_cf
:
virtual
public
sync_block
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{
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public
:
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// gr::analog::quadrature_demod_cf::sptr
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typedef
std::shared_ptr<quadrature_demod_cf>
sptr
;
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/* \brief Make a quadrature demodulator block.
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*
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* \param gain Gain setting to adjust the output amplitude. Set
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* based on converting the phase difference between
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* samples to a nominal output value.
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*/
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static
sptr
make(
float
gain);
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virtual
void
set_gain(
float
gain) = 0;
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virtual
float
gain()
const
= 0;
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};
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}
/* namespace analog */
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}
/* namespace gr */
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#endif
/* INCLUDED_ANALOG_QUADRATURE_DEMOD_CF_H */
ANALOG_API
#define ANALOG_API
Definition:
gr-analog/include/gnuradio/analog/api.h:18
gr::analog::quadrature_demod_cf::sptr
std::shared_ptr< quadrature_demod_cf > sptr
Definition:
quadrature_demod_cf.h:64
gr::sync_block
synchronous 1:1 input to output with history
Definition:
sync_block.h:25
gr::analog::quadrature_demod_cf
quadrature demodulator: complex in, float out
Definition:
quadrature_demod_cf.h:60
sync_block.h
gr
GNU Radio logging wrapper for log4cpp library (C++ port of log4j)
Definition:
basic_block.h:29
api.h
gr-analog
include
gnuradio
analog
quadrature_demod_cf.h
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