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from __future__ import division
import meep as mp
import math
import numpy as np
import unittest
## compute the Poynting flux of an Ez-polarized dipole point source
## from the fields in 3 arrangements:
## (1) bounding box of the near fields
## (2) bounding circle of the far fields
## (3) bounding box of the far fields
class TestAntennaRadiation(unittest.TestCase):
def test_farfield(self):
resolution = 50
sxy = 4
dpml = 1
cell = mp.Vector3(sxy+2*dpml,sxy+2*dpml)
pml_layers = mp.PML(dpml)
fcen = 1.0
df = 0.4
sources = mp.Source(src=mp.GaussianSource(fcen,fwidth=df),
center=mp.Vector3(),
component=mp.Ez)
symmetries = [mp.Mirror(mp.X),
mp.Mirror(mp.Y)]
sim = mp.Simulation(cell_size=cell,
resolution=resolution,
sources=[sources],
symmetries=symmetries,
boundary_layers=[pml_layers])
nearfield_box = sim.add_near2far(fcen, 0, 1,
mp.Near2FarRegion(mp.Vector3(y=0.5*sxy), size=mp.Vector3(sxy)),
mp.Near2FarRegion(mp.Vector3(y=-0.5*sxy), size=mp.Vector3(sxy), weight=-1),
mp.Near2FarRegion(mp.Vector3(0.5*sxy), size=mp.Vector3(y=sxy)),
mp.Near2FarRegion(mp.Vector3(-0.5*sxy), size=mp.Vector3(y=sxy), weight=-1))
flux_box = sim.add_flux(fcen, 0, 1,
mp.FluxRegion(mp.Vector3(y=0.5*sxy), size=mp.Vector3(sxy)),
mp.FluxRegion(mp.Vector3(y=-0.5*sxy), size=mp.Vector3(sxy), weight=-1),
mp.FluxRegion(mp.Vector3(0.5*sxy), size=mp.Vector3(y=sxy)),
mp.FluxRegion(mp.Vector3(-0.5*sxy), size=mp.Vector3(y=sxy), weight=-1))
sim.run(until_after_sources=mp.stop_when_fields_decayed(50, mp.Ez, mp.Vector3(), 1e-8))
near_flux = mp.get_fluxes(flux_box)[0]
r = 1000/fcen # radius of far field circle
npts = 100 # number of points in [0,2*pi) range of angles
E = np.zeros((npts,3),dtype=np.complex128)
H = np.zeros((npts,3),dtype=np.complex128)
for n in range(npts):
ff = sim.get_farfield(nearfield_box,
mp.Vector3(r*math.cos(2*math.pi*n/npts),
r*math.sin(2*math.pi*n/npts)))
E[n,:] = [np.conj(ff[j]) for j in range(3)]
H[n,:] = [ff[j+3] for j in range(3)]
Px = np.real(E[:,1]*H[:,2]-E[:,2]*H[:,1])
Py = np.real(E[:,2]*H[:,0]-E[:,0]*H[:,2])
Pr = np.sqrt(np.square(Px)+np.square(Py))
far_flux_circle = np.sum(Pr)*2*np.pi*r/len(Pr)
rr = 20/fcen # length of far field square box
far_flux_square = (nearfield_box.flux(mp.Y, mp.Volume(center=mp.Vector3(y=0.5*rr), size=mp.Vector3(rr)), resolution)[0]
- nearfield_box.flux(mp.Y, mp.Volume(center=mp.Vector3(y=-0.5*rr), size=mp.Vector3(rr)), resolution)[0]
+ nearfield_box.flux(mp.X, mp.Volume(center=mp.Vector3(0.5*rr), size=mp.Vector3(y=rr)), resolution)[0]
- nearfield_box.flux(mp.X, mp.Volume(center=mp.Vector3(-0.5*rr), size=mp.Vector3(y=rr)), resolution)[0])
print("flux:, {:.6f}, {:.6f}, {:.6f}".format(near_flux,far_flux_circle,far_flux_square))
self.assertAlmostEqual(near_flux, far_flux_circle, places=2)
self.assertAlmostEqual(far_flux_circle, far_flux_square, places=2)
self.assertAlmostEqual(far_flux_square, near_flux, places=2)
if __name__ == '__main__':
unittest.main()
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