analytic_filter_h_a1.vhd

The Hilbert Transform is an important component in communication systems, e.g. for single sideband m

-- Implementation of Filter H_a1(z)
-- 
-- 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/>.

-- Package Definition

library ieee;
use ieee.std_logic_1164.all;
use IEEE.STD_LOGIC_arith.all;

package analytic_filter_h_a1_pkg is
component analytic_filter_h_a1
	generic(
		input_data_width : integer;
		output_data_width : integer;
		filter_delay_in_clks : integer  --delay of hilbert filter
	);
	port(
    clk_i : in std_logic;
    rst_i : in std_logic;
    data_str_i : in std_logic;
    data_i : in std_logic_vector(input_data_width-1 downto 0);
    data_i_o : out std_logic_vector(output_data_width-1 downto 0);
    data_q_o : out std_logic_vector(output_data_width-1 downto 0);
    data_str_o : out std_logic
	);
end component; 
end analytic_filter_h_a1_pkg;

package body analytic_filter_h_a1_pkg is
end analytic_filter_h_a1_pkg;

-- Entity Definition

library ieee;
use ieee.std_logic_1164.all;
use IEEE.STD_LOGIC_arith.all;
use work.const_delay_pkg.all;
use work.hilbert_filter_pkg.all;

entity analytic_filter_h_a1 is
	generic(
		input_data_width : integer := 16;
		output_data_width : integer := 16;
		filter_delay_in_clks : integer  := 7 --delay of hilbert filter (including pipeline delay)
	);
	port(
	    clk_i : in std_logic;
	    rst_i : in std_logic;
	    data_str_i : in std_logic;
	    data_i : in std_logic_vector(input_data_width-1 downto 0);
	    data_i_o : out std_logic_vector(output_data_width-1 downto 0);
	    data_q_o : out std_logic_vector(output_data_width-1 downto 0);
	    data_str_o : out std_logic
	);
end analytic_filter_h_a1; 

architecture analytic_filter_h_a1_arch of analytic_filter_h_a1 is

  function maximum_int(
    x1 : integer;
    x2 : integer
    ) return integer is
  begin
    if x1 > x2 then
      return x1;
    else
      return x2;
    end if;
  end maximum_int;

constant max_data_width : integer := maximum_int(input_data_width,output_data_width);
signal const_delay_data_i, const_delay_data_o : std_logic_vector(max_data_width-1 downto 0);

begin

const_delay_data_i(max_data_width-1 downto max_data_width-input_data_width) <= data_i;

zero_pad: if max_data_width-input_data_width > 0 generate
	const_delay_data_i(max_data_width-input_data_width-1 downto 0) <= (others => '0');
end generate;

data_i_o <= const_delay_data_o(max_data_width-1 downto max_data_width-output_data_width);

in_phase_channel : const_delay
	generic map(
		data_width    => max_data_width,
		delay_in_clks => filter_delay_in_clks
	)
	port map(
	    clk_i => clk_i,
	    rst_i => rst_i,
	    data_i => const_delay_data_i,
	    data_str_i => data_str_i,
	    data_o => const_delay_data_o,
	    data_str_o => data_str_o
	);
	
quadrature_phase_channel : hilbert_filter
  generic map(
    input_data_width    => input_data_width,
    output_data_width => output_data_width,
    internal_data_width => max_data_width
  )
   port map( 
	   clk        => clk_i,
	   clk_enable => data_str_i,
	   reset      => rst_i,
	   filter_in  => data_i,
	   filter_out => data_q_o
   );

	
end analytic_filter_h_a1_arch;