I’m using gnuradio-3.3.0 with GRC.
I’ve builded a graph with a Complex cosine (8Ms/s of sample rate
and 1 MHz of frequency), the fractional interpolator with 12/8 value
for interpolation and a FFT sink with 12MS/s of sample rate. (throttle
block included).
I’m expecting to see a 1MHz cosine with the FFT, but i see a
2.25MHz cosine. If i put 8/12 (the inverse) i see the (correct) 1MHz
cosine.
Why?
If i use the Rational resampler, with interpolation 12 and
decimation 8, i see the correct 1MHz cosine. What’s wrong with
fractional interpolator block?