Just commit.

applications/lofar2/model/rtdsp/firfilter.py

@@ -77,6 +77,8 @@ def square_root_raised_cosine_response(Ntaps, Nsps, roBeta):
     . Ntaps : FIR filter length
     . Nsps: symbol period Tsymbol in number of samples per symbol
     . roBeta : Roll off factor in [0, 1.0]
+       - roBeta = 0.0: rectangular spectrum with BW = 1 / Tsymbol
+       - roBeta = 1.0: sqrt cosine spectrum with BW = 2 / Tsymbol
     Return:
     . hSrRc : impulse response of the square root raised cosine filter.
     """
@@ -160,7 +162,7 @@ def design_fir_low_pass_filter(method,
                                Ncoefs, fpass, fstop, fcutoff=0, cutoffGain=0.5, rippleWeights=[1, 1],
                                kaiserBeta=0, fs=1.0,
                                cutoffBW=0):
-    """Derive FIR coefficients for prototype low pass filter
+    """Derive FIR coefficients for low pass filter
 
     Use method 'firls' or 'remez', fs = 1.0
 
@@ -218,7 +220,7 @@ def design_fir_low_pass_filter(method,
         if is_even(N):
             N = N - 1
     if method == 'remez':
-        NRemezMax = 1024
+        NRemezMax = 512
         Q = ceil_div(Ncoefs, NRemezMax)
         N = Ncoefs // Q
 
@@ -339,3 +341,16 @@ def prototype_fir_low_pass_filter(method='firls',
     # Design subband filter
     h = design_fir_low_pass_filter(method, Ncoefs, fpass, fstop, fcutoff, cutoffGain, rippleWeights, kaiserBeta, fs)
     return h
+
+
+###############################################################################
+# Filterbank transfer function for prototype LPF
+###############################################################################
+
+def derive_filterbank_transfer(HFprototype, Npoints):
+    Lprototype = len(HFprototype)
+    Lbin = Lprototype / Npoints
+    HFbank = np.zeros(Lprototype, dtype='cfloat')
+    for bi in range(Npoints):
+        HFbank += np.roll(HFprototype, bi * Lbin)
+    return HFbank

applications/lofar2/model/rtdsp/fourier.py

@@ -133,6 +133,10 @@ def dtft(coefs, Ndtft=None, zeroCenter=True, fftShift=True):
     return h, f, HF
 
 
+###############################################################################
+# Estimate f for certain gain or estimate gain for certain frequency
+###############################################################################
+
 def estimate_gain_at_frequency(f, HF, freq):
     """Find gain = abs(HF) at frequency in f that is closest to freq.