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106 lines
2.7 KiB
Python
106 lines
2.7 KiB
Python
import numpy as np
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import itertools
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import recv
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import common
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class Filter(object):
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def __init__(self, b, a):
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self.b = b
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self.a = a
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self.x = [0] * len(b)
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self.y = [0] * len(a)
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def __call__(self, x):
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self.x = [x] + self.x[:-1]
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assert len(self.x) == len(self.b)
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assert len(self.y) == len(self.a)
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y = np.dot(self.x, self.b) - np.dot(self.y, self.a)
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self.y = [y] + self.y[:-1]
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return y
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def overlap_iter(x, n, overlap=0):
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assert overlap >= 0
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assert overlap < n
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res = []
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x = iter(x)
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while True:
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res.extend(itertools.islice(x, n - len(res)))
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if len(res) < n:
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break
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yield tuple(res)
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res = res[n - overlap:]
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def test_overlap():
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assert list(overlap_iter(range(7), 3, 1)) == [(0,1,2), (2,3,4), (4,5,6)]
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assert list(overlap_iter(range(7), 3, 0)) == [(0,1,2), (3,4,5)]
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def calib(S):
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for S0, S1 in overlap_iter(S, 2, overlap=1):
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dS = S1 / S0
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yield dS
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class Interpolator(object):
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def __init__(self, resolution=1000, width=20):
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self.width = width
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self.resolution = resolution
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self.N = resolution * width
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u = np.arange(-self.N, self.N, dtype=float)
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window = (1 + np.cos(0.5 * np.pi * u / self.N)) / 2.0
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h = np.sinc(u / resolution) * window
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self.filt = []
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for index in range(resolution): # split into multiphase filters
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self.filt.append(h[index::resolution])
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def get(self, x, offset):
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k = int(offset)
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j = np.round((offset - k) * self.resolution)
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h = self.filt[(self.resolution - int(j)) % self.resolution]
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offset = np.ceil(offset)
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begin, end = offset - self.width, offset + self.width
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return np.dot(h, x[begin:end])
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class Sampler(object):
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def __init__(self, src, frame_size):
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self.src = src
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self.freq = 1.0
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self.offset = 0
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self.frame_size = frame_size
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self.buff = []
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def frame(self):
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self.buff.extend()
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def
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if __name__ == '__main__':
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import pylab
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if 0:
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f0 = 10e3
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t, x = common.load('recv_10kHz.pcm')
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S = recv.extract_symbols(x, f0)
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S = np.array(list(S))
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y = S #np.array(list(calib(S)))
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pylab.subplot(1,2,1)
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pylab.plot(y.real, y.imag, '.'); pylab.axis('equal')
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pylab.subplot(1,2,2)
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pylab.plot(np.unwrap(np.angle(y)))
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pylab.grid('on')
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t = np.arange(64) * common.Ts
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x = np.sin(2 * np.pi * 3.456e3 * t)
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r = Interpolator()
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# pylab.figure()
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y = []
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k = 32 + np.linspace(-5, 5, 1001)
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for offset in k:
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y.append( r.get(x, offset) )
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pylab.figure()
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pylab.plot(t, x, '.', k * common.Ts, y, '-')
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pylab.show()
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