def beamx(self, feed, freq):
"""Beam for the x polarisation feed.
Parameters
----------
feed : integer
Index for the feed.
freq : integer
Index for the frequency.
Returns
-------
beam : np.ndarray
Healpix maps (of size [self._nside, 2]) of the field pattern in the
theta and phi directions.
"""
beampert = int(self.beamclass[feed] / 2)
if beampert == 0:
return cylbeam.beam_x(self._angpos, self.zenith,
self.cylinder_width / self.wavelengths[freq], self.fwhm_e, self.fwhm_h)
elif beampert == 1:
beam0 = cylbeam.beam_x(self._angpos, self.zenith,
self.cylinder_width / self.wavelengths[freq], self.fwhm_e, self.fwhm_h)
beam1 = cylbeam.beam_x(self._angpos, self.zenith,
self.cylinder_width / self.wavelengths[freq], self.fwhm_e * 1.01, self.fwhm_h)
dbeam = (beam1 - beam0) / (0.01 * self.fwhm_e)
return dbeam
def beamx(self, feed, freq):
"""Beam for the x polarisation feed.
Parameters
----------
feed : integer
Index for the feed.
freq : integer
Index for the frequency.
Returns
-------
beam : np.ndarray
Healpix maps (of size [self._nside, 2]) of the field pattern in the
theta and phi directions.
"""
beampert = int(self.beamclass[feed] // 2)
if beampert == 0:
return cylbeam.beam_x(
self._angpos,
self.zenith,
self.cylinder_width / self.wavelengths[freq],
self.fwhm_e,
self.fwhm_h,
)
elif beampert == 1:
beam0 = cylbeam.beam_x(
self._angpos,
self.zenith,
self.cylinder_width / self.wavelengths[freq],
self.fwhm_e,
self.fwhm_h,
)
beam1 = cylbeam.beam_x(
self._angpos,
self.zenith,
self.cylinder_width / self.wavelengths[freq],
self.fwhm_e * 1.01,
self.fwhm_h,
)
dbeam = (beam1 - beam0) / (0.01 * self.fwhm_e)
return dbeam
def beamx(self, feed, freq):
return cylbeam.beam_x(
self._angpos,
self.zenith,
self.cylinder_width / self.wavelengths[freq],
self.fwhm_e,
self.fwhm_h,
)
def beamx(self, feed, freq):
return cylbeam.beam_x(self._angpos, self.zenith,
self.cylinder_width / self.wavelengths[freq], self.fwhm_e, self.fwhm_h)
def beam(self, feed, freq, angpos=None):
"""Primary beam implementation for the CHIME/Pathfinder.
This only supports normal CHIME cylinder antennas. Asking for the beams
for other types of inputs will cause an exception to be thrown. The
beams from this routine are rotated by `self.rotation_angle` to account
for the CHIME/Pathfinder rotation.
Parameters
----------
feed : int
Index for the feed.
freq : int
Index for the frequency.
angpos : np.ndarray[nposition, 2], optional
Angular position on the sky (in radians).
If not provided, default to the _angpos
class attribute.
Returns
-------
beam : np.ndarray[nposition, 2]
Amplitude vector of beam at each position on the sky.
"""
# # Fetch beam parameters out of config database.
feed_obj = self.feeds[feed]
# Check that feed exists and is a CHIME cylinder antenna
if feed_obj is None:
raise ValueError(
"Craziness. The requested feed doesn't seem to exist.")
if not tools.is_array(feed_obj):
raise ValueError("Requested feed is not a CHIME antenna.")
# If the angular position was not provided, then use the values in the
# class attribute.
if angpos is None:
angpos = self._angpos
# Get the beam rotation parameters.
yaw = -self.rotation_angle
pitch = 0.0
roll = 0.0
rot = np.radians([yaw, pitch, roll])
# We can only support feeds angled parallel or perp to the cylinder
# axis. Check for these and throw exception for anything else.
if tools.is_array_y(feed_obj):
beam = cylbeam.beam_y(
angpos,
self.zenith,
self.cylinder_width / self.wavelengths[freq],
self.fwhm_ey[freq],
self.fwhm_hy[freq],
rot=rot,
)
elif tools.is_array_x(feed_obj):
beam = cylbeam.beam_x(
angpos,
self.zenith,
self.cylinder_width / self.wavelengths[freq],
self.fwhm_ex[freq],
self.fwhm_hx[freq],
rot=rot,
)
else:
raise RuntimeError(
"Given polarisation (feed.pol=%s) not supported." %
feed_obj.pol)
# Normalize the beam
if self._beam_normalization is not None:
beam *= self._beam_normalization[freq, feed, np.newaxis, :]
return beam
