5ndft_vhdl/mult_blk_5ndft.vhd

LIBRARY ieee;
USE ieee.std_logic_1164.ALL;
USE ieee.numeric_std.ALL;
USE work.FIVEn_DFT_PKG.ALL;

-- purpose : deledate the multiplication and the addition witn the complex
-- exponential Wn to this bloc
ENTITY MULT_BLK_5nDFT IS
  GENERIC(
    w_in   : natural;
    w_mult : natural
    );
  PORT(i_clk     : IN  std_logic;
       i_data_re : IN  smpl_out_radix2;
       i_data_im : IN  smpl_out_radix2;
       i_cos     : IN  smpl_cos_sin_wb;
       i_sin     : IN  smpl_cos_sin_wb;
       o_data_re : OUT smpl_out_radix2;
       o_data_im : OUT smpl_out_radix2
       );
END MULT_BLK_5nDFT;

ARCHITECTURE Mult_Path OF MULT_BLK_5nDFT IS

  SIGNAL data_mult_re_cos_signed : smpl_out_signed_radix2;  -- intermediate result re*cos
  SIGNAL data_mult_im_cos_signed : smpl_out_signed_radix2;  -- intermediate result im*cos
  SIGNAL data_mult_re_sin_signed : smpl_out_signed_radix2;  -- intermediate result im*sin,!i*i=-1!
  SIGNAL data_mult_im_sin_signed : smpl_out_signed_radix2;  -- intermediate result re*sin
  SIGNAL sin_signed              : smpl_cos_sin_signed_wb;  -- signed input sin
  SIGNAL cos_signed              : smpl_cos_sin_signed_wb;  -- signed input cos
  SIGNAL data_re_signed          : smpl_out_signed_radix2;  -- signed input data im
  SIGNAL data_im_signed          : smpl_out_signed_radix2;  -- signed input data re


BEGIN

  -- assign the signed signals before doing any operation
  data_re_signed(w_in-1 DOWNTO 0) <= signed(i_data_re(w_in-1 DOWNTO 0));
  data_im_signed(w_in-1 DOWNTO 0) <= signed(i_data_im(w_in-1 DOWNTO 0));
  cos_signed                      <= signed(i_cos);
  sin_signed                      <= signed(i_sin);


  
  -- purpose: multiply the real and imag part with the cos ans isin part of the
  -- exponential, and add the results of real parts and imag ones together.
  -- Needs 2 clock edges to process the whole mult result
  -- inputs: signed data(im & re), signed exponential (cos & sin)
  -- outputs: o_data_re, o_data_im
  mult : PROCESS(i_clk)
  BEGIN
    IF rising_edge(i_clk) THEN
      data_mult_re_cos_signed(w_in+w_mult-1 DOWNTO 0) <= data_re_signed(w_in-1 DOWNTO 0) * cos_signed;
      data_mult_im_cos_signed(w_in+w_mult-1 DOWNTO 0) <= data_im_signed(w_in-1 DOWNTO 0) * cos_signed;
      data_mult_im_sin_signed(w_in+w_mult-1 DOWNTO 0) <= data_re_signed(w_in-1 DOWNTO 0) * sin_signed;
      data_mult_re_sin_signed(w_in+w_mult-1 DOWNTO 0) <= data_im_signed(w_in-1 DOWNTO 0) * sin_signed;

      o_data_re(w_in+w_mult DOWNTO 0) <= std_logic_vector(unsigned(signed(data_mult_re_cos_signed(w_in+w_mult-1)&data_mult_re_cos_signed(w_in+w_mult-1 DOWNTO 0)) - signed(data_mult_re_sin_signed(w_in+w_mult-1)&data_mult_re_sin_signed(w_in+w_mult-1 DOWNTO 0))));-- i*i=-1
      o_data_im(w_in+w_mult DOWNTO 0) <= std_logic_vector(unsigned(signed(data_mult_im_cos_signed(w_in+w_mult-1)&data_mult_im_cos_signed(w_in+w_mult-1 DOWNTO 0)) + signed(data_mult_im_sin_signed(w_in+w_mult-1)&data_mult_im_sin_signed(w_in+w_mult-1 DOWNTO 0))));
    END IF;

  END PROCESS;

END Mult_Path;