mirror of https://github.com/hb9fxq/gr-digitalhf
79 lines
2.7 KiB
Python
79 lines
2.7 KiB
Python
## -*- python -*-
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import numpy as np
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CONST_DTYPE=np.dtype([('points', np.complex64),
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('symbols', np.int32)])
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SYMB_SCRAMBLE_DTYPE=np.dtype([('symb', np.complex64),
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('scramble', np.complex64)])
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def n_psk(n,x):
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"""n-ary PSK constellation"""
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return np.complex64(np.exp(2j*np.pi*x/n))
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def freq_est(z):
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"""Data-Aided Frequency Estimation for Burst Digital Transmission,
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Umberto Mengali and M. Morelli, IEEE TRANSACTIONS ON COMMUNICATIONS,
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VOL. 45, NO. 1, JANUARY 1997"""
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L0 = len(z)
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N = L0//2
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R = np.zeros(N+1, dtype=np.complex64)
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for i in range(N+1):
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R[i] = 1.0/(L0-i)*np.sum(z[i:]*np.conj(z[0:L0-i])) ## eq (3)
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m = np.arange(N+1, dtype=np.float32)
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w = 3*((L0-m)*(L0-m+1)-N*(L0-N))/(N*(4*N*N - 6*N*L0 + 3*L0*L0-1)) ## eq (9)
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mod_2pi = lambda x : np.mod(x-np.pi, 2*np.pi) - np.pi
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return np.sum(w[1:] * mod_2pi(np.diff(np.angle(R)))) ## eq (8)
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class Depuncturer(object):
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def __init__(self, repeat=1, puncture_pattern=['1','1']):
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assert(repeat >= 1)
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self._repeat = repeat
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self._num_patterns = num_patterns = len(puncture_pattern)
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assert(num_patterns >= 2)
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assert(all([len(puncture_pattern[0]) == len(p) for p in puncture_pattern[1:]]))
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m = np.array([x=='1' for y in puncture_pattern for x in y])
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self._num_unpacked = len(m)
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self._num_packed = np.sum(m)
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self._pattern = m.reshape(num_patterns, self._num_unpacked//num_patterns).transpose().reshape(1, self._num_unpacked)[0]
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self._range_packed = np.arange(self._num_packed)
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self._range_unpacked = np.arange(self._num_unpacked)
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def process(self, x):
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n = len(x)
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assert(n%(self._num_packed * self._repeat) == 0)
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## (1) unpack
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xd = np.zeros(n * self._num_unpacked // self._num_packed, dtype=np.float64)
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i = 0
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j = 0
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while i < len(xd):
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xd[(i + self._range_unpacked)[self._pattern]] += x[j + self._range_packed]
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j += self._num_packed
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i += self._num_unpacked
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assert(j == n)
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assert(i == len(xd))
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if self._repeat == 1:
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return xd
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## (2) combine repeated data
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xu = np.zeros(len(xd) // self._repeat, dtype=np.float64)
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i = 0
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j = 0
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m = self._num_patterns
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r = np.arange(m)
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while i < len(xu):
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for k in range(self._repeat):
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xu[i + r] += xd[j + r]
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j += m
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i += m
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assert(i == len(xu))
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assert(j == len(xd))
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return xu
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if __name__ == '__main__':
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idx=np.arange(3)
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z=np.exp(1j*idx*0.056+1j)
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print(freq_est(z)/0.056)
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