I guess I may have a misunderstanding on the usage of
firdes.root_raised_cosine (double gain, double sampling_freq, double symbol_rate, double alpha, int ntaps) function.
In the flowgraph, the parameters are set up as follows:
samp_rate = 32k;
upsampling_rate (sps) = 4;
# of pylyphase filter in Polyphase Clock Sync block nfilts = 32;
ntaps = 11*4*32;
If I set the gain as 1.0/float(sps) = 1.0/4.0, the rrc_taps for Polyphase Clock Sync should be (equation 1):
firdes.root_raised_cosine (1.0/4.0, 32000, 32000/4, 0.35, 11*4*32).
firdes.root_raised_cosine(nfilts, nfilts, 1.0/float(sps), 0.35, 11*sps*nfilts), which works great for the mpsk_stage4.grc. Could somebody explain why this rrc_taps shouldn't be as in equation 1?