From e13b6b5fb9dde25e649e6ef4a6256a3eb1b53ee2 Mon Sep 17 00:00:00 2001
From: Eric Kooistra <kooistra@astron.nl>
Date: Tue, 5 Apr 2022 14:50:15 +0200
Subject: [PATCH] Rename c_wpfb_lofar2_subbands_* constants. Added
func_wpfb_sst_level().
---
libraries/dsp/wpfb/src/vhdl/wpfb_pkg.vhd | 68 +++++++++++++++---------
1 file changed, 44 insertions(+), 24 deletions(-)
diff --git a/libraries/dsp/wpfb/src/vhdl/wpfb_pkg.vhd b/libraries/dsp/wpfb/src/vhdl/wpfb_pkg.vhd
index 2f47ccaf17..71d3145036 100644
--- a/libraries/dsp/wpfb/src/vhdl/wpfb_pkg.vhd
+++ b/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
--
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