# -*- coding: utf-8 -*-
from abc import abstractmethod
import numpy as np
from ...base import Property, Base
[docs]class BeamShape(Base):
"""Base class for beam shape"""
peak_power: float = Property(doc="peak power of the main lobe in Watts")
[docs] @abstractmethod
def beam_power(self, azimuth, elevation, beam_width, **kwargs):
"""beam power sent in the direction of the target.
azimuth = elevation = 0 for center of beam"""
raise NotImplementedError
[docs]class Beam2DGaussian(BeamShape):
r"""The beam is in the shape of a 2D gaussian in the azimuth and elevation.
The width at half the maxima is the beam width. It is described by:
.. math::
P = P_p\exp \left( 0.5 \times \left(\left(\frac{2.35\,az}{B_w}\right)
^2 +\left(\frac{2.35\,el}{B_w}\right)^2 \right) \right)
where :math:`az` and :math:`el` are the azimuth and elevation angles away
from the centre. :math:`B_w` is the beam width and :math:`P_p` is the peak
power.
"""
# Full width half maximum
FWHM = 2 * np.sqrt(2 * np.log(2))
[docs] def beam_power(self, azimuth, elevation, beam_width, **kwargs):
"""
Parameters
----------
azimuth : `float`
The angle of the target away from the boresight of the radar in
azimuth
elevation : `float`
The angle of the target away from the boresight of the radar in
elevation
beam_width: `float`
The width of the radar beam
Returns
-------
`float`
the power directed towards the target
"""
return self.peak_power * np.exp(
-0.5 * ((azimuth/beam_width*self.FWHM)**2 + (elevation/beam_width*self.FWHM)**2))