Subversion Repositories astron_wb_fft

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--

-- Copyright 2020

-- ASTRON (Netherlands Institute for Radio Astronomy) <http://www.astron.nl/>

-- P.O.Box 2, 7990 AA Dwingeloo, The Netherlands

-- 

-- Licensed under the Apache License, Version 2.0 (the "License");

-- you may not use this file except in compliance with the License.

-- You may obtain a copy of the License at

-- 

--     http://www.apache.org/licenses/LICENSE-2.0

-- 

-- Unless required by applicable law or agreed to in writing, software

-- distributed under the License is distributed on an "AS IS" BASIS,

-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

-- See the License for the specific language governing permissions and

-- limitations under the License.

--

--------------------------------------------------------------------------------

-- Purpose: The fft_r2_wide unit performs a complex FFT that is partly pipelined 

--          and partly parallel. 

--

-- Description:

--  The fft_r2_wide supports:

--

--  * Complex input

--    For complex input use_separate = false.

--

--    When use_reorder=true then the output bins of the FFT are re-ordered to 

--    undo the bit-reversed (or bit-flipped) default radix 2 FFT output order.

--    The fft_r2_wide then outputs first 0 Hz and the positive frequencies

--    and then the negative frequencies. The use_reorder is performed at both

--    the pipelined stage and the parallel stage.

--

--    When use_fft_shift=true then the fft_r2_wide then outputs the frequency

--    bins in incrementing order, so first the negative frequencies, then 0 Hz

--    and then the positive frequencies.

--    When use_fft_shift = true then also use_reorder must be true.

--

--  * Two real inputs:

--    When use_separate=true then the fft_r2_wide can be used to process two

--    real streams. The first real stream (A) presented on the real input, the

--    second real stream (B) presented on the imaginary input. The separation

--    unit outputs the spectrum of A and B in an alternating way.

--    When use_separate = true then also use_reorder must be true.

--    When use_separate = true then the use_fft_shift must be false, because

--    fft_shift() only applies to spectra for complex input.

--

-- Remarks:

-- . This fft_r2_wide also support wb_factor = 1 (= only a fft_r2_pipe

--   instance) or wb_factor = g_fft.nof_points (= only a fft_r2_par instance).

--   Care must be taken to properly account for guard_w and out_gain_w,

--   therefore it is best to simply use a structural approach that generates

--   seperate instances for each case:

--   . wb_factor = 1                                  --> pipe

--   . wb_factor > 1 AND wb_factor < g_fft.nof_points --> wide

--   . wb_factor = g_fft.nof_points                   --> par

-- . This fft_r2_wide uses the use_reorder in the pipeline FFT, in the parallel

--   FFT and also has reorder memory in the fft_sepa_wide instance. The reorder

--   memories in the FFTs can maybe be saved by using only the reorder memory

--   in the fft_sepa_wide instance. This would require changing the indexing in

--   fft_sepa_wide instance.

-- . The reorder memory in the pipeline FFT, parallel FFT and in the

--   fft_sepa_wide could make reuse of a reorder component from the reorder

--   library instead of using a dedicated local solution.

library ieee, common_pkg_lib, common_components_lib, common_requantize_lib, rTwoSDF_lib;

use IEEE.std_logic_1164.all;

use common_pkg_lib.common_pkg.all;

use rTwoSDF_lib.rTwoSDFPkg.all;

use work.fft_pkg.all;

entity fft_r2_wide is

  generic (

    g_fft          : t_fft := c_fft;                   -- generics for the FFT

    g_pft_pipeline : t_fft_pipeline := c_fft_pipeline; -- For the pipelined part, from rTwoSDF_lib.rTwoSDFPkg

    g_fft_pipeline : t_fft_pipeline := c_fft_pipeline  -- For the parallel part, from rTwoSDF_lib.rTwoSDFPkg

  );

  port (

    clk        : in  std_logic;

    rst        : in  std_logic := '0';

    in_re_arr  : in  t_fft_slv_arr(g_fft.wb_factor-1 downto 0); -- = time samples t3, t2, t1, t0

    in_im_arr  : in  t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

    in_val     : in  std_logic := '1';

    out_re_arr : out t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

    out_im_arr : out t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

    out_val    : out std_logic

  );

end entity fft_r2_wide;

architecture rtl of fft_r2_wide is

  type t_fft_arr is array(integer range <> ) of t_fft;  -- An array of t_fft's generics. 

  ----------------------------------------------------------

  -- This function creates an array of t_fft generics 

  -- for the pipelined fft's of the first stage.The array is 

  -- based on the g_fft generic that belongs to the 

  -- fft_r2_wide entity. 

  -- Most imortant in the settings are twiddle_offset and 

  -- the nof_points.

  ----------------------------------------------------------

  function func_create_generic_for_pipe_fft(input : t_fft) return t_fft_arr is

    variable v_nof_points : natural := input.nof_points/input.wb_factor;                 -- The nof_points for the pipelined fft stages

    variable v_return     : t_fft_arr(input.wb_factor-1 downto 0) := (others => input);  -- Variable that holds the return values

  begin

    for I in 0 to input.wb_factor-1 loop

      v_return(I).use_reorder    := input.use_reorder; -- Pass on use_reorder

      v_return(I).use_fft_shift  := false;             -- FFT shift function is forced to false

      v_return(I).use_separate   := false;             -- Separate function is forced to false. 

      v_return(I).twiddle_offset := I;                 -- Twiddle offset is set to the order number of the pipelined fft. 

      v_return(I).nof_points     := v_nof_points;      -- Set the nof points 

      v_return(I).in_dat_w       := input.stage_dat_w; -- Set the input width  

      v_return(I).out_dat_w      := input.stage_dat_w; -- Set the output width. 

      v_return(I).out_gain_w     := 0;                 -- Output gain is forced to 0

      v_return(I).guard_w        := 0;                 -- Set the guard_w to 0 to enable scaling at every stage. 

      v_return(I).guard_enable   := false;             -- No input guard. 

    end loop;

    return v_return;

  end;

  ----------------------------------------------------------

  -- This function creates t_fft generic for the 

  -- parallel fft stage, based on the g_fft generic that 

  -- belongs to the fft_r2_wide entity. 

  ----------------------------------------------------------

  function func_create_generic_for_par_fft(input : t_fft) return t_fft is

    variable v_return         : t_fft   := input;  -- Variable that holds the return value

  begin

      v_return.use_reorder    := input.use_reorder;    -- Pass on use_reorder

      v_return.use_fft_shift  := input.use_fft_shift;  -- Pass on use_fft_shift

      v_return.use_separate   := false;                -- Separate function is forced to false, because it is handled outside the parallel fft

      v_return.twiddle_offset := 0;                    -- Twiddle offset is forced to 0, which is also the input.twiddle_offset default

      v_return.nof_points     := input.wb_factor;      -- Set the number of points to wb_factor

      v_return.in_dat_w       := input.stage_dat_w;    -- Specify the input width

      v_return.out_dat_w      := input.stage_dat_w;    -- Output width 

      v_return.out_gain_w     := 0;                    -- Output gain is forced to 0, because it is handled outside the parallel fft

      v_return.guard_w        := input.guard_w;        -- Set the guard_w here to skip the scaling on the last stages

      v_return.guard_enable   := false;                -- No input guard. 

    return v_return;

  end;

  constant c_pipeline_remove_lsb : natural := 0;

  constant c_fft_r2_pipe_arr  : t_fft_arr(g_fft.wb_factor-1 downto 0) := func_create_generic_for_pipe_fft(g_fft);

  constant c_fft_r2_par       : t_fft                                 := func_create_generic_for_par_fft(g_fft);

  constant c_in_scale_w       : natural := g_fft.stage_dat_w - g_fft.in_dat_w - sel_a_b(g_fft.guard_enable, g_fft.guard_w, 0);

  constant c_out_scale_w      : integer := c_fft_r2_par.out_dat_w - g_fft.out_dat_w - g_fft.out_gain_w;  -- Estimate number of LSBs to throw away when > 0 or insert when < 0

  signal in_fft_pipe_re_arr   : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal in_fft_pipe_im_arr   : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal out_fft_pipe_re_arr  : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal out_fft_pipe_im_arr  : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal in_fft_par_re_arr    : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal in_fft_par_im_arr    : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal fft_pipe_out_re      : std_logic_vector(g_fft.out_dat_w-1 downto 0);

  signal fft_pipe_out_im      : std_logic_vector(g_fft.out_dat_w-1 downto 0);

  signal fft_out_re_arr       : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal fft_out_im_arr       : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal fft_out_val          : std_logic;

  signal sep_out_re_arr       : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal sep_out_im_arr       : t_fft_slv_arr(g_fft.wb_factor-1 downto 0);

  signal sep_out_val          : std_logic;

  signal int_val              : std_logic_vector(g_fft.wb_factor-1 downto 0);

  signal out_cplx             : std_logic_vector(c_nof_complex*g_fft.stage_dat_w-1 downto 0);

  signal in_cplx              : std_logic_vector(c_nof_complex*g_fft.stage_dat_w-1 downto 0);

begin

  -- Default to fft_r2_pipe when g_fft.wb_factor=1

  gen_fft_r2_pipe : if g_fft.wb_factor=1 generate

    u_fft_r2_pipe : entity work.fft_r2_pipe

    generic map (

      g_fft      => g_fft,

      g_pipeline => g_pft_pipeline

    )

    port map (

      clk        => clk,

      rst        => rst,

      in_re      => in_re_arr(0)(g_fft.in_dat_w-1 downto 0),

      in_im      => in_im_arr(0)(g_fft.in_dat_w-1 downto 0),

      in_val     => in_val,

      out_re     => fft_pipe_out_re,

      out_im     => fft_pipe_out_im,

      out_val    => out_val

    );

    out_re_arr(0) <= resize_fft_svec(fft_pipe_out_re);

    out_im_arr(0) <= resize_fft_svec(fft_pipe_out_im);

  end generate;

  -- Default to fft_r2_par when g_fft.wb_factor=g_fft.nof_points

  gen_fft_r2_par : if g_fft.wb_factor=g_fft.nof_points generate

    u_fft_r2_par : entity work.fft_r2_par

    generic map (

      g_fft      => g_fft,

      g_pipeline => g_fft_pipeline

    )

    port map (

      clk        => clk,

      rst        => rst,

      in_re_arr  => in_re_arr,

      in_im_arr  => in_im_arr,

      in_val     => in_val,

      out_re_arr => out_re_arr,

      out_im_arr => out_im_arr,

      out_val    => out_val

    );

  end generate;

  -- Create wideband FFT as combinination of g_fft.wb_factor instances of fft_r2_pipe with one instance of fft_r2_par

  gen_fft_r2_wide : if g_fft.wb_factor>1 and g_fft.wb_factor<g_fft.nof_points generate

    ---------------------------------------------------------------

    -- PIPELINED FFT STAGE

    ---------------------------------------------------------------

    -- Inputs are prepared/scaled for the pipelined ffts

    gen_fft_pipe_inputs : for I in 0 to g_fft.wb_factor-1 generate

      in_fft_pipe_re_arr(I) <= scale_and_resize_svec(in_re_arr(I), c_in_scale_w, c_fft_slv_w);

      in_fft_pipe_im_arr(I) <= scale_and_resize_svec(in_im_arr(I), c_in_scale_w, c_fft_slv_w);

    end generate;

    -- The first stage of the wideband fft consist of the generation of g_fft.wb_factor

    -- pipelined fft's. These pipelines fft's operate in parallel.   

    gen_pipelined_ffts : for I in g_fft.wb_factor-1 downto 0 generate

      u_pft : entity work.fft_r2_pipe

      generic map (

        g_fft      => c_fft_r2_pipe_arr(I),   -- generics for the pipelined FFTs

        g_pipeline => g_pft_pipeline          -- pipeline generics for the pipelined FFTs

      )

      port map (

        clk       => clk,

        rst       => rst,

        in_re     => in_fft_pipe_re_arr(I)(c_fft_r2_pipe_arr(I).in_dat_w-1 downto 0),

        in_im     => in_fft_pipe_im_arr(I)(c_fft_r2_pipe_arr(I).in_dat_w-1 downto 0),

        in_val    => in_val,

        out_re    => out_fft_pipe_re_arr(I)(c_fft_r2_pipe_arr(I).out_dat_w-1 downto 0),

        out_im    => out_fft_pipe_im_arr(I)(c_fft_r2_pipe_arr(I).out_dat_w-1 downto 0),

        out_val   => int_val(I)

      );

    end generate;

    ---------------------------------------------------------------

    -- PARALLEL FFT STAGE

    ---------------------------------------------------------------

    -- Create input for parallel FFT

    gen_inputs_for_par : for I in g_fft.wb_factor-1 downto 0 generate

      in_fft_par_re_arr(I) <= resize_fft_svec(out_fft_pipe_re_arr(I)(c_fft_r2_pipe_arr(I).out_dat_w-1 downto 0));

      in_fft_par_im_arr(I) <= resize_fft_svec(out_fft_pipe_im_arr(I)(c_fft_r2_pipe_arr(I).out_dat_w-1 downto 0));

    end generate;

    -- The g_fft.wb_factor outputs of the pipelined fft's are offered

    -- to the input of a single parallel FFT. 

    u_fft : entity work.fft_r2_par

    generic map (

      g_fft      => c_fft_r2_par,           -- generics for the FFT

      g_pipeline => g_fft_pipeline          -- pipeline generics for the parallel FFT

    )

    port map (

      clk        => clk,

      rst        => rst,

      in_re_arr  => in_fft_par_re_arr,

      in_im_arr  => in_fft_par_im_arr,

      in_val     => int_val(0),

      out_re_arr => fft_out_re_arr,

      out_im_arr => fft_out_im_arr,

      out_val    => fft_out_val

    );

    ---------------------------------------------------------------

    -- OPTIONAL: SEPARATION STAGE

    ---------------------------------------------------------------

    -- When the separate functionality is required:

    gen_separate : if g_fft.use_separate generate

      u_separator : entity work.fft_sepa_wide

      generic map (

        g_fft      => g_fft

      )

      port map (

        clk        => clk,

        rst        => rst,

        in_re_arr  => fft_out_re_arr,

        in_im_arr  => fft_out_im_arr,

        in_val     => fft_out_val,

        out_re_arr => sep_out_re_arr,

        out_im_arr => sep_out_im_arr,

        out_val    => sep_out_val

      );

    end generate;

     -- In case no separtion is required, the output of the parallel fft is used. 

    no_separate : if g_fft.use_separate=false generate

      sep_out_re_arr <= fft_out_re_arr;

      sep_out_im_arr <= fft_out_im_arr;

      sep_out_val    <= fft_out_val;

    end generate;

    ---------------------------------------------------------------

    -- OUTPUT QUANTIZER

    ---------------------------------------------------------------

    gen_output_requantizers : for I in g_fft.wb_factor-1 downto 0 generate

      u_requantize_output_re : entity common_requantize_lib.common_requantize

      generic map (

        g_representation      => "SIGNED",

        g_lsb_w               => c_out_scale_w,

        g_lsb_round           => TRUE,

        g_lsb_round_clip      => FALSE,

        g_msb_clip            => FALSE,

        g_msb_clip_symmetric  => FALSE,

        g_pipeline_remove_lsb => c_pipeline_remove_lsb,

        g_pipeline_remove_msb => 0,

        g_in_dat_w            => g_fft.stage_dat_w,

        g_out_dat_w           => g_fft.out_dat_w

      )

      port map (

        clk        => clk,

        in_dat     => sep_out_re_arr(I),

        out_dat    => out_re_arr(I),

        out_ovr    => open

      );

      u_requantize_output_im : entity common_requantize_lib.common_requantize

      generic map (

        g_representation      => "SIGNED",

        g_lsb_w               => c_out_scale_w,

        g_lsb_round           => TRUE,

        g_lsb_round_clip      => FALSE,

        g_msb_clip            => FALSE,

        g_msb_clip_symmetric  => FALSE,

        g_pipeline_remove_lsb => c_pipeline_remove_lsb,

        g_pipeline_remove_msb => 0,

        g_in_dat_w            => g_fft.stage_dat_w,

        g_out_dat_w           => g_fft.out_dat_w

      )

      port map (

        clk        => clk,

        in_dat     => sep_out_im_arr(I),

        out_dat    => out_im_arr(I),

        out_ovr    => open

      );

    end generate;

    u_out_val : entity common_components_lib.common_pipeline_sl

    generic map (

      g_pipeline => c_pipeline_remove_lsb

    )

    port map (

      rst     => rst,

      clk     => clk,

      in_dat  => sep_out_val,

      out_dat => out_val

    );

  end generate;

end rtl;