def update_descriptors(self):
if self.kernel.value is None:
raise ValueError("Integrator was passed kernel None")
logger.debug(
'Updating KernelIntegrator "%s" descriptors based on input descriptor: %s.',
self.name, self.sink.descriptor)
record_length = self.sink.descriptor.axes[-1].num_points()
if self.simple_kernel.value:
time_pts = self.sink.descriptor.axes[-1].points
time_step = time_pts[1] - time_pts[0]
kernel = np.zeros(record_length, dtype=np.complex128)
sample_start = int(self.box_car_start.value / time_step)
sample_stop = int(self.box_car_stop.value / time_step) + 1
kernel[sample_start:sample_stop] = 1.0
# add modulation
kernel *= np.exp(2j * np.pi * self.frequency.value * time_step *
time_pts)
else:
kernel = eval(self.kernel.value.encode('unicode_escape'))
# pad or truncate the kernel to match the record length
if kernel.size < record_length:
self.aligned_kernel = np.append(
kernel,
np.zeros(record_length - kernel.size, dtype=np.complex128))
else:
self.aligned_kernel = np.resize(kernel, record_length)
# Integrator reduces and removes axis on output stream
# update output descriptors
output_descriptor = DataStreamDescriptor()
# TODO: handle reduction to single point
output_descriptor.axes = self.sink.descriptor.axes[:-1]
output_descriptor.exp_src = self.sink.descriptor.exp_src
output_descriptor.dtype = np.complex128
for os in self.source.output_streams:
os.set_descriptor(output_descriptor)
os.end_connector.update_descriptors()
def update_descriptors(self):
logger.debug(
'Updating Channelizer "%s" descriptors based on input descriptor: %s.',
self.name, self.sink.descriptor)
# extract record time sampling
time_pts = self.sink.descriptor.axes[-1].points
self.record_length = len(time_pts)
self.time_step = time_pts[1] - time_pts[0]
logger.debug("Channelizer time_step = {}".format(self.time_step))
# convert bandwidth normalized to Nyquist interval
n_bandwidth = self.bandwidth.value * self.time_step * 2
n_frequency = self.frequency.value * self.time_step * 2
# arbitrarily decide on three stage filter pipeline
# 1. first stage decimating filter on real data
# 2. second stage decimating filter on mixed product to boost n_bandwidth
# 3. final channel selecting filter at n_bandwidth/2
# anecdotally don't decimate more than a factor of eight for stability
self.decim_factors = [1] * 3
self.filters = [None] * 3
# first stage decimating filter
# maximize first stage decimation:
# * minimize subsequent stages time taken
# * filter and decimate while signal is still real
# * first stage decimation cannot be too large or then 2omega signal from mixing will alias
d1 = 1
while (d1 < 8) and (2 * n_frequency <=
0.8 / d1) and (d1 < self.decimation_factor.value):
d1 *= 2
n_bandwidth *= 2
n_frequency *= 2
if d1 > 1:
# create an anti-aliasing filter
# pass-band to 0.8 * decimation factor; anecdotally single precision needs order <= 4 for stability
b, a = scipy.signal.cheby1(4, 3, 0.8 / d1)
b = np.float32(b)
a = np.float32(a)
self.decim_factors[0] = d1
self.filters[0] = (b, a)
# store decimated reference for mix down
ref = np.exp(2j * np.pi * self.frequency.value * time_pts[::d1],
dtype=np.complex64)
self.reference_r = np.real(ref)
self.reference_i = np.imag(ref)
# second stage filter to bring n_bandwidth/2 up
# decimation cannot be too large or will impinge on channel bandwidth (keep n_bandwidth/2 <= 0.8)
d2 = 1
while (d2 < 8) and ((d1 * d2) < self.decimation_factor.value) and (
n_bandwidth / 2 <= 0.8):
d2 *= 2
n_bandwidth *= 2
n_frequency *= 2
if d2 > 1:
# create an anti-aliasing filter
# pass-band to 0.8 * decimation factor; anecdotally single precision needs order <= 4 for stability
b, a = scipy.signal.cheby1(4, 3, 0.8 / d2)
b = np.float32(b)
a = np.float32(a)
self.decim_factors[1] = d2
self.filters[1] = (b, a)
# final channel selection filter
if n_bandwidth < 0.1:
raise ValueError(
"Insufficient decimation to achieve stable filter")
b, a = scipy.signal.cheby1(4, 3, n_bandwidth / 2)
b = np.float32(b)
a = np.float32(a)
self.decim_factors[2] = self.decimation_factor.value // (d1 * d2)
self.filters[2] = (b, a)
# update output descriptors
decimated_descriptor = DataStreamDescriptor()
decimated_descriptor.axes = self.sink.descriptor.axes[:]
decimated_descriptor.axes[-1] = deepcopy(self.sink.descriptor.axes[-1])
decimated_descriptor.axes[-1].points = self.sink.descriptor.axes[
-1].points[self.decimation_factor.value -
1::self.decimation_factor.value]
decimated_descriptor.axes[
-1].original_points = decimated_descriptor.axes[-1].points
decimated_descriptor.exp_src = self.sink.descriptor.exp_src
decimated_descriptor.dtype = np.complex64
for os in self.source.output_streams:
os.set_descriptor(decimated_descriptor)
if os.end_connector is not None:
os.end_connector.update_descriptors()
