Hi,
I've generated a MAC-FIR Filter, using Xilinx' Core Generator (MAC FIR
5.1) from the Web Pack. The coefficients have been determined via Matlab and the filter has been simulated there, all fine. To verify my implemented filter I compared the out put gains at different frequencies, and obtained:
step input f=0 x=128,000 y=128,370 sinusodial input f=70kHz xmax=128,000 ymax=115,209 sinusodial input f=100kHz xmax=128,000 ymax= 9,780
which results in a stop band attenuation of about 23dB. However I designed it for a stop band attenuation of 80dB! What I'm doing wrong? What's your experience with the core generator?
filter characteristic low pass, fpass=70kHz, fstop=90kHz, fsampling=720kHz, 8 channels, fclock = 92.16MHz, 122 taps, data and coeff width 18 bits, output width 42 bits.
I've an open discussion to this topic in comp.dsp too, but more related to signal processing.
This is my coe file:
radix=10; coefdata = 80, 233, 276, 336, 250, 77, -168, -372, -440, -302, 19, 403, 673, 668, 329, -243, -811, -1091, -887, -205, 704, 1432,
1585, 984, -204, -1493, -2263, -2050, -796, 1050, 2674, 3243, 2311, 101, -2500, -4277, -4231, -2102, 1389, 4745, 6299, 5000, 1024, -4118,
-8099, -8761, -5183, 1661, 9031, 13395, 11938, 4022,
-8061,-19461,-24283,-17740, 1813, 31799, 65789, 95295,112416,112416, 95295, 65789, 31799,
1813,-17740,
-24283,-19461, -8061, 4022, 11938, 13395, 9031, 1661, -5183, -8761,
-8099, -4118, 1024, 5000, 6299, 4745, 1389, -2102, -4231, -4277, -2500, 101, 2311, 3243, 2674, 1050, -796, -2050, -2263, -1493, -204, 984,
1585, 1432, 704, -205, -887, -1091, -811, -243, 329, 668, 673, 403, 19, -302, -440, -372, -168, 77, 250, 336, 276, 233, 80;