--- /dev/null
+## Copyright (C) 2003 David Bateman
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 3 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'amdsb-tc',offset)
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'amdsb-sc')
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'amssb')
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'amssb/time',@var{num},@var{den})
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'qam')
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'fm',@var{dev})
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},@var{Fs},'pm',@var{dev})
+## @deftypefnx {Function File} {@var{y} =} amodce (@var{x},[@var{Fs},@var{iphs}],@var{...})
+##
+## Baseband modulator for analog signals. The input signal is specified by
+## @var{x}, its sampling frequency by @var{Fs} and the type of modulation
+## by the third argument, @var{typ}. The default values of @var{Fs} is 1 and
+## @var{typ} is 'amdsb-tc'.
+##
+## If the argument @var{Fs} is a two element vector, the the first element
+## represents the sampling rate and the second the initial phase.
+##
+## The different types of modulations that are available are
+##
+## @table @asis
+## @item 'am'
+## @itemx 'amdsb-tc'
+## Double-sideband with carrier
+## @item 'amdsb-sc'
+## Double-sideband with suppressed carrier
+## @item 'amssb'
+## Single-sideband with frequency domain Hilbert filtering
+## @item 'amssb/time'
+## Single-sideband with time domain filtering. Hilbert filter is used by
+## default, but the filter can be specified
+## @item 'qam'
+## Quadrature amplitude modulation
+## @item 'fm'
+## Frequency modulation
+## @item 'pm'
+## Phase modulation
+## @end table
+##
+## Additional arguments are available for the modulations 'amdsb-tc', 'fm,
+## 'pm' and 'amssb/time'. These arguments are
+##
+## @table @code
+## @item offset
+## The offset in the input signal for the transmitted carrier.
+## @item dev
+## The deviation of the phase and frequency modulation
+## @item num
+## @itemx den
+## The numerator and denominator of the filter transfer function for the
+## time domain filtering of the SSB modulation
+## @end table
+##
+## @end deftypefn
+## @seealso{ademodce,dmodce}
+
+function y = amodce (x, Fs, typ, varargin)
+
+ if (nargin < 1)
+ help("amodce");
+ elseif (nargin < 2)
+ Fs = 1;
+ typ = "am";
+ elseif (nargin < 3)
+ typ = "am";
+ endif
+
+ if (isempty(Fs))
+ Fs = 1;
+ iphs = 0;
+ elseif (isscalar(Fs))
+ iphs = 0;
+ else
+ if ((max(size(Fs)) != 2) || (min(size(Fs)) != 1))
+ error ("amodce: sampling frequency must be a scalar or 2-element vector");
+ endif
+ Fs = Fs(1);
+ iphs = Fs(2);
+ endif
+
+ ## Pass the optional arguments
+ offset = min(x(:));
+ dev = 1;
+ num = [];
+ den = [];
+ narg = 1;
+ if (!ischar(typ))
+ error ("amodce: modulation type must be a string");
+ elseif (strcmp(typ,"am") || strcmp(typ,"amdsb-tc"))
+ if (length(varargin) > 0)
+ offset = varargin{1};
+ narg = narg + 1;
+ endif
+ elseif (strcmp(typ,"fm") || strcmp(typ,"pm"))
+ if (length(varargin) > 0)
+ dev = varargin{1};
+ narg = narg + 1;
+ endif
+ endif
+ if (length(varargin) == narg)
+ error ("amodce: must specify must numerator and denominator of transfer function");
+ elseif (length(varargin) == narg+1)
+ num = varargin{narg};
+ den = varargin{narg+1};
+ elseif (length(varargin) != narg - 1)
+ error ("amodce: too many arguments");
+ endif
+
+ if (strcmp(typ,"am") || strcmp(typ,"amdsb-tc"))
+ y = (x + offset) * exp(1i * iphs);
+ elseif (strcmp(typ,"amdsb-sc"))
+ y = x * exp(1i * iphs);
+ elseif (strcmp(typ,"amssb"))
+ if (!isreal(x))
+ error ("amodce: SSB modulated signal must be real");
+ endif
+ ## Damn, must treat Hilbert transform row-by-row!!!
+ y = zeros(size(x));
+ for i=1:size(x,2)
+ y(:,i) = hilbert(x(:,i)) * exp(1i * iphs);
+ end
+ elseif (strcmp(typ,"amssb/time"))
+ if (isempty(num) || isempty(dem))
+ error ("amodce: have not implemented Hilbert transform in time domain yet");
+ endif
+ y = zeros(size(x));
+ for i=1:size(x,2)
+ y(:,i) = filter(num, den, x(:,i));
+ y(:,i) = (x(:,i) + 1i*y(:,i)) * exp(1i * iphs);
+ end
+ elseif (strcmp(typ,"qam"))
+ if (isreal(x))
+ if (floor(size(x,2)/2) != (size(x,2)/2))
+ error ("amodce: QAM modulation must have an even number of columns for real signals");
+ endif
+ y = (x(:,1:2:size(x,2)) + 1i * x(:,2:2:size(x,2)));
+ else
+ y = x;
+ endif
+ y = y * exp(1i * iphs);
+ elseif (strcmp(typ,"pm"))
+ y = exp(1i * (dev*x + iphs));
+ elseif (strcmp(typ,"fm"))
+ ## To convert to PM signal, need to evaluate
+ ## p(t) = \int_0^t dev * x(T) dT
+ ## As x(t) is discrete and not a function, the only way to perform the
+ ## above integration is with Simpson's rule. Note \Delta T = 2 * pi / Fs.
+ pm = pi / Fs * dev * (cumsum([zeros(1,size(x,2));x(1:size(x,1)-1,:)]) ...
+ + cumsum(x));
+ y = exp(1i * (pm + iphs));
+ else
+ error ("amodce: unknown modulation specified");
+ endif
+
+endfunction
+
git://git.creatis.insa-lyon.fr / CreaPhase.git / blobdiff