-- g_fft_out_gain_w : NATURAL := 1; -- = 1, output gain factor applied after the last stage output, before requantization to out_dat_w
-- g_fft_stage_dat_w : NATURAL := 18; -- = c_dsp_mult_w = 18, number of bits that are used inter-stage
-- g_fft_guard_w : NATURAL := 1 -- = 2
-- g_r2_mul_extra_w : NATURAL := 0 -- = 0, extra bits at rTwoWMul output in rTwoSDFStage to improve rTwoSDFStage output requantization in fft_r2_pipe in wpfb_unit_dev