Package that creates I and Q samples to test the IQ Correction block

library ieee;
use ieee.std_logic_1164.all;
use ieee.math_real.all;
use ieee.numeric_std.all;
use work.normal_distribution_random_noise.all;

--by MEP 22 February 2011
--usage:
--these are functions, which means they can be on the right-hand side
--of an assignment. These functions create an I and Q sample.
--The arguments are
--a natural number standing for the index of the sample,
--a real number that provides a way to have many samples per period,
--a real number standing for the standard deviation of the normally distributed
noise added to the sample,
--a real number standing for the amplitude of the signal,
--a natural number indicating the width of the vector holding the returned
value,
--a real number indicating the gain error of Q with respect to I,
--and a real number indicating the phase error of Q with respect to I
--
--create_I_sample(n_dat, freq, sgma, amplitude, return_width);
--create_Q_sample(n_dat, freq, sgma, amplitude, return_width, e1, a1);
--

package create_sample is

function create_I_sample(
n_dat : integer;
freq : real;
sgma : real;
amplitude : real;
return_width : natural)
return signed;

function create_Q_sample(
n_dat : integer;
freq : real;
sgma : real;
amplitude : real;
return_width : natural; --x1_tb'LENGTH
e1 : real; --gain error
a1 : real) --phase error
return signed;

end package create_sample;

package body create_sample is

function create_I_sample(
n_dat : integer;
freq : real;
sgma : real;
amplitude : real;
return_width : natural) --x1_tb'LENGTH
return signed is

variable local_x1 : real;
variable int_x1: integer;
variable returned_x1 : signed(return_width downto 0);

begin

local_x1 := amplitude*sin(2.0*math_pi*(real(n_dat))*freq) +
random_noise(sgma);
--report "local_x1 inside CREATE_I_SAMPLE function is " &
real'image(local_x1) & ".";

--AGC scaling. Scaling factor is maximum value the signal can take.
local_x1 := local_x1/(1.11);
--report "local_x1 after AGC inside CREATE_I_SAMPLE function is " &
real'image(local_x1) & ".";

int_x1 := integer(trunc(local_x1*((2.0**31.0)-1.0))); --scaled
--report "integer version of x1 inside CREATE_I_SAMPLE function is " &
integer'image(int_x1) & ".";

returned_x1 := (to_signed(int_x1, return_width+1));

return returned_x1;
end function;

function create_Q_sample(
n_dat : integer;
freq : real;
sgma : real;
amplitude : real;
return_width : natural; --x1_tb'LENGTH
e1 : real; --gain error
a1 : real)
return signed is

variable local_y1 : real;
variable int_y1: integer;
variable returned_y1 : signed(return_width downto 0);

begin
local_y1 := amplitude*(1.0 + e1)*cos(2.0*math_pi*(real(n_dat))*freq +
a1) + random_noise(sgma);
--report "local_y1 first created CREATE_Q_SAMPLE function is " &
real'image(local_y1) & ".";

--AGC scaling. Scaling factor is maximum value the signal can take.
local_y1 := local_y1/(1.11);
--report "local_y1 after AGC inside CREATE_Q_SAMPLE function is " &
real'image(local_y1) & ".";

int_y1 := integer(trunc(local_y1*((2.0**31.0)-1.0))); --scaled
--report "integer version of y1 inside CREATE_Q_SAMPLE function is " &
integer'image(int_y1) & ".";

returned_y1 := (to_signed(int_y1, return_width+1));

return returned_y1;
end function;
end package body create_sample;