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-- Copyright (C) 2002 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs 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 2 of the License, or (at
-- your option) any later version.
-- VESTs 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 VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
library ieee, ieee_proposed;
use ieee_proposed.electrical_systems.all;
use ieee.std_logic_1164.all;
use ieee.math_real.all;
entity bfsk is
generic ( fc : real := 1.0e6; -- mean carrier frequency
delta_f : real := 5.0e3; -- difference between low and high
-- carrier frequencies
amp : voltage := 1.0; -- amplitude of modulated signal
offset : voltage := 0.0 ); -- output offset voltage
port ( signal d_in : in std_logic; -- digital input
terminal a_out : electrical ); -- output terminal
end entity bfsk;
----------------------------------------------------------------
architecture behavioral of bfsk is
quantity vout across iout through a_out; -- output branch
quantity phi : real; -- free quantity angle in radians
constant wc : real := math_2_pi * fc; -- convert fc to rad/s
constant delta_w : real := math_2_pi * delta_f; -- convert delta_f to rad/s
begin
if To_X01(d_in) = '0' use
phi'dot == wc; -- set to carrier frequency
elsif To_X01(d_in) = '1' use
phi'dot == wc + delta_w; -- set to carrier frequency + delta
else
phi'dot == 0.0;
end use;
break on d_in;
vout == offset + amp * sin(phi); -- create sinusoidal output using phi
end architecture behavioral;
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