def beam(self, feed, freq):
"""Beam for a particular feed.
Parameters
----------
feed : integer
Index for the feed.
freq : integer
Index for the frequency.
Returns
-------
beam : np.ndarray
A Healpix map (of size self._nside) of the beam. Potentially
complex.
"""
if self._bc_freq != freq or self._bc_nside != self._nside:
sigma = np.radians(self.fwhm) / (8.0 * np.log(2.0))**0.5 / (
self.frequencies[freq] / 150.0)
pointing = np.array(
[np.pi / 2.0 - np.radians(self.pointing), self.zenith[1]])
x2 = (1.0 - coord.sph_dot(self._angpos, pointing)**2) / (4 *
sigma**2)
self._bc_map = np.exp(-x2)
self._bc_freq = freq
self._bc_nside = self._nside
return self._bc_map
def beam(self, feed, freq):
"""Beam for a particular feed.
Parameters
----------
feed : integer
Index for the feed.
freq : integer
Index for the frequency.
Returns
-------
beam : np.ndarray
A Healpix map (of size self._nside) of the beam. Potentially
complex.
"""
if self._bc_freq != freq or self._bc_nside != self._nside:
sigma = np.radians(self.fwhm) / (8.0*np.log(2.0))**0.5 / (self.frequencies[freq] / 150.0)
pointing = np.array([np.pi / 2.0 - np.radians(self.pointing), self.zenith[1]])
x2 = (1.0 - coord.sph_dot(self._angpos, pointing)**2) / (4*sigma**2)
self._bc_map = np.exp(-x2)
self._bc_freq = freq
self._bc_nside = self._nside
return self._bc_map
def horizon(sph_arr, zenith):
r"""The horizon function at particular location.
Parameters
----------
sph_arr : np.ndarray
Angular positions (in spherical polar co-ordinates).
zenith : np.ndarray
The zenith vector in spherical polar-coordinates.
Returns
-------
horizon : np.ndarray
The horizon function (including an angular projection term at
each position).
"""
proj = coord.sph_dot(sph_arr, zenith)
return np.signbit(-proj)
def horizon(sph_arr, zenith):
r"""The horizon function at particular location.
Parameters
----------
sph_arr : np.ndarray
Angular positions (in spherical polar co-ordinates).
zenith : np.ndarray
The zenith vector in spherical polar-coordinates.
Returns
-------
horizon : np.ndarray
The horizon function (including an angular projection term at
each position).
"""
proj = coord.sph_dot(sph_arr, zenith)
return np.signbit(-proj)
def beam_circular(angpos, zenith, uv_diameter):
"""Beam pattern for a circular dish.
Parameters
----------
angpos : np.ndarray
Array of angular positions
zenith : np.ndarray
Co-ordinates of the zenith.
uv_diameter : scalar
Diameter of the dish (in units of wavelength).
Returns
-------
beam : np.ndarray
Beam pattern at each position in angpos.
"""
x = (1.0 - coord.sph_dot(angpos, zenith)**2)**0.5 * np.pi * uv_diameter
return 2*jinc(x)
def beam_circular(angpos, zenith, uv_diameter):
"""Beam pattern for a circular dish.
Parameters
----------
angpos : np.ndarray
Array of angular positions
zenith : np.ndarray
Co-ordinates of the zenith.
uv_diameter : scalar
Diameter of the dish (in units of wavelength).
Returns
-------
beam : np.ndarray
Beam pattern at each position in angpos.
"""
x = (1.0 - coord.sph_dot(angpos, zenith) ** 2) ** 0.5 * np.pi * uv_diameter
return 2 * jinc(x)
def beam_circular(angpos, zenith, diameter):
"""Beam pattern for a uniformly illuminated circular dish.
Parameters
----------
angpos : np.ndarray
Array of angular positions
zenith : np.ndarray
Co-ordinates of the zenith.
diameter : scalar
Diameter of the dish (in units of wavelength).
Returns
-------
beam : np.ndarray
Beam pattern at each position in angpos.
"""
def jinc(x):
return 0.5 * (jn(0, x) + jn(2, x))
x = (1.0 - coord.sph_dot(angpos, zenith)**2)**0.5 * np.pi * diameter
return 2 * jinc(x)
def beam_circular(angpos, zenith, diameter):
"""Beam pattern for a uniformly illuminated circular dish.
Parameters
----------
angpos : np.ndarray
Array of angular positions
zenith : np.ndarray
Co-ordinates of the zenith.
diameter : scalar
Diameter of the dish (in units of wavelength).
Returns
-------
beam : np.ndarray
Beam pattern at each position in angpos.
"""
def jinc(x):
return 0.5 * (jn(0, x) + jn(2, x))
x = (1.0 - coord.sph_dot(angpos, zenith)**2)**0.5 * np.pi * diameter
return 2*jinc(x)
def gaussian_beam(angpos, pointing, fwhm):
sigma = np.radians(fwhm) / (8.0*np.log(2.0))**0.5
x2 = (1.0 - coord.sph_dot(angpos, pointing)**2) / (4*sigma**2)
return np.exp(-x2)
def gaussian_beam(angpos, pointing, fwhm):
sigma = np.radians(fwhm) / (8.0 * np.log(2.0))**0.5
x2 = (1.0 - coord.sph_dot(angpos, pointing)**2) / (4 * sigma**2)
return np.exp(-x2)
