Rename c_wpfb_lofar2_subbands_* constants. Added func_wpfb_sst_level().

libraries/dsp/wpfb/src/vhdl/wpfb_pkg.vhd

@@ -75,40 +75,55 @@ package wpfb_pkg is
   -----------------------------------------------------------------------------
 
   -- Fsub settings:
-  -- . Settings used until at least March 2022
-  constant c_wpfb_lofar2_subbands_2021 : t_wpfb := (1, 1024, 0, 6,
-                                                    16, 0, 14, 17, 16,
-                                                    true, false, true, 17, 18, 0, 22, 1, true, 54, 2, 195313,
-                                                    c_fft_pipeline, c_fft_pipeline, c_fil_ppf_pipeline);
+  -- . Settings used on LTS and DTS until at least March 2022
+  constant c_wpfb_lofar2_subbands_lts_2021 : t_wpfb := (1, 1024, 0, 6,
+                                                        16, 0, 14, 17, 16,
+                                                        true, false, true, 17, 18, 0, 22, 1, true, 54, 2, 195313,
+                                                        c_fft_pipeline, c_fft_pipeline, c_fil_ppf_pipeline);
 
-  constant c_wpfb_lofar2_subbands_2022 : t_wpfb := (1, 1024, 0, 6,
-                                                    16, 1, 14, 0, 16,
-                                                    true, false, true, 0, 19, 1, 24, 1, true, 56, 2, 195313,
-                                                    c_fft_pipeline, c_fft_pipeline, c_fil_ppf_pipeline);
+  -- . Settings used on DTS in 2022 with fft_out_dat_w = 18b, to have same levels as with c_wpfb_lofar2_subbands_lts
+  --   - use fil_backoff_w to avoid overshoot and fft_out_gain_w = 1 to compensate to keep output level
+  --   - use stage_dat_w = 24 --> fil_out_dat_w = fft_in_dat_w = 23
+  constant c_wpfb_lofar2_subbands_dts_18b : t_wpfb := (1, 1024, 0, 6,
+                                                       16, 1, 14, 23, 16,
+                                                       true, false, true, 23, 18, 1, 24, 1, true, 54, 2, 195313,
+                                                       c_fft_pipeline, c_fft_pipeline, c_fil_ppf_pipeline);
 
-  constant c_wpfb_lofar2_subbands      : t_wpfb := c_wpfb_lofar2_subbands_2022;
+  -- . Settings used on DTS with fft_out_dat_w = 19b, to preserve FFT processing gain of 4.5 bits
+  --   - use stage_dat_w = 25 --> fil_out_dat_w = fft_in_dat_w = 24
+  --   - with fft_out_dat_w = 19 --> stat_data_w = 2*19 + 18 = 56 b
+  constant c_wpfb_lofar2_subbands_dts_19b : t_wpfb := (1, 1024, 0, 6,
+                                                       16, 1, 14, 24, 16,
+                                                       true, false, true, 24, 19, 1, 25, 1, true, 56, 2, 195313,
+                                                       c_fft_pipeline, c_fft_pipeline, c_fil_ppf_pipeline);
 
-  -- DC gain of WPFB FIR filter with Coeffs16384Kaiser-quant.dat used in LOFAR1.
-  -- . Calculated with applications/lofar2/model/run_pfir_coef.m using application = 'lofar_subband'
-  -- . Not used in RTL, only used in test benches to verify expected subband levels
-  constant c_wpfb_lofar1_fir_filter_dc_gain    : real := 0.994817;
+  constant c_wpfb_lofar2_subbands : t_wpfb := c_wpfb_lofar2_subbands_dts_18b;
 
   -- The FFT output has more bits to be able to preserve the sensitivity of
   -- the processing gain of the FFT. The FFT has a processing gain of
   -- sqrt(N_sub = N_fft / 2 = 512), so 4.5 bits. Therefore choose
   -- fft_out_dat_w = fil_in_dat_w + 5 = 14 + 5 = 19b. Using fft_out_gain_w =
-  -- 1 compensates for the fil_backoff_w = 1. The func_wpfb_subband_scale_w
-  -- then thus returns 19 + 1 - (14 + 1) = 5 bits.
+  -- 1 compensates for the fil_backoff_w = 1 of the FIR filter. The
+  -- func_wpfb_subband_scale_w then thus returns 19 + 1 - (14 + 1) = 5 bits.
   function func_wpfb_subband_scale_w(wpfb : t_wpfb) return natural;
 
   -- The WPFB subband gain is the expected factor between subband amplitude
-  -- and real signal input amplitude. The WPFB subband gain consists of:
-  -- . the FFT gain for a real input and
-  -- . the extra bits to preserve the sensitivity of the FFT processing gain.
+  -- A_sub and real signal input amplitude A_sp, so:
+  --   A_sub = A_sp * func_wpfb_subband_gain()
+  -- The WPFB subband gain consists of:
+  -- . DC gain of the FIR filter (= fir_filter_dc_gain ~= 1.0),
+  -- . the FFT gain for a real input (= c_fft_real_input_gain_sine = 0.5) and
+  -- . the extra bits to preserve the sensitivity of the FFT processing gain
+  --   (derived from wpfb).
   -- For example:
-  -- . func_wpfb_subband_gain() =  8 for c_wpfb_lofar2_subbands_2021
-  -- . func_wpfb_subband_gain() = 16 for c_wpfb_lofar2_subbands_2022
-  function func_wpfb_subband_gain(wpfb : t_wpfb) return real;
+  -- . func_wpfb_subband_gain() ~=  8 for c_wpfb_lofar2_subbands_lts_2021 and
+  --                                  for c_wpfb_lofar2_subbands_dts_18b
+  -- . func_wpfb_subband_gain() ~= 16 for c_wpfb_lofar2_subbands_dts_19b
+  function func_wpfb_subband_gain(wpfb : t_wpfb; fir_filter_dc_gain : real) return real;
+
+  -- The expected WPFB SST level for subband amplitude A_sub and an integration
+  -- interval of N_int subband blocks (periods).
+  function func_wpfb_sst_level(A_sub : real; N_int : natural) return real;
 
   -----------------------------------------------------------------------------
   -- Apertif application specfic settings
@@ -236,9 +251,14 @@ package body wpfb_pkg is
     return wpfb.fft_out_dat_w + wpfb.fft_out_gain_w - (wpfb.fil_in_dat_w + wpfb.fil_backoff_w);
   end;
 
-  function func_wpfb_subband_gain(wpfb : t_wpfb) return real is
+  function func_wpfb_subband_gain(wpfb : t_wpfb; fir_filter_dc_gain : real) return real is
+  begin
+    return fir_filter_dc_gain * c_fft_real_input_gain_sine * 2.0**real(func_wpfb_subband_scale_w(wpfb));
+  end;
+
+  function func_wpfb_sst_level(A_sub : real; N_int : natural) return real is
   begin
-    return c_fft_real_input_gain * 2.0**real(func_wpfb_subband_scale_w(wpfb));
+    return A_sub ** 2.0 * REAL(N_int);
   end;
 
   function func_wpfb_maximum_sop_latency(wpfb : t_wpfb) return natural is