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authorRuben Undheim <ruben.undheim@gmail.com>2019-02-10 08:20:54 +0000
committerRuben Undheim <ruben.undheim@gmail.com>2019-02-10 08:20:54 +0000
commitffda26309128be5d112df61a03e4827e47ecfac8 (patch)
tree7552a0f13b6873dbf98c41b84cb81bac0f220ca7 /openEMS/python/Tutorials/Bent_Patch_Antenna.py
parent086965becc2a02254e3441a1d97b61ccab2d66ea (diff)
Import GIT HEAD of openEMS sub-project (with Python interface)
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+# -*- coding: utf-8 -*-
+"""
+ Bent Patch Antenna Tutorial
+
+ Tested with
+ - python 3.4
+ - openEMS v0.0.33+
+
+ (C) 2016 Thorsten Liebig <thorsten.liebig@gmx.de>
+
+"""
+
+### Import Libraries
+import os, tempfile
+from pylab import *
+from mpl_toolkits.mplot3d import Axes3D
+
+from CSXCAD import CSXCAD
+
+from openEMS.openEMS import openEMS
+from openEMS.physical_constants import *
+
+
+### Setup the simulation
+Sim_Path = os.path.join(tempfile.gettempdir(), 'Bent_Patch')
+
+post_proc_only = False
+
+unit = 1e-3 # all length in mm
+
+f0 = 2.4e9 # center frequency, frequency of interest!
+lambda0 = round(C0/f0/unit) # wavelength in mm
+fc = 0.5e9 # 20 dB corner frequency
+
+# patch width in alpha-direction
+patch_width = 32 # resonant length in alpha-direction
+patch_radius = 50 # radius
+patch_length = 40 # patch length in z-direction
+
+#substrate setup
+substrate_epsR = 3.38
+substrate_kappa = 1e-3 * 2*pi*2.45e9 * EPS0*substrate_epsR
+substrate_width = 80
+substrate_length = 90
+substrate_thickness = 1.524
+substrate_cells = 4
+
+#setup feeding
+feed_pos = -5.5 #feeding position in x-direction
+feed_width = 2 #feeding port width
+feed_R = 50 #feed resistance
+
+# size of the simulation box
+SimBox_rad = 2*100
+SimBox_height = 1.5*200
+
+### Setup FDTD parameter & excitation function
+FDTD = openEMS(CoordSystem=1) # init a cylindrical FDTD
+f0 = 2e9 # center frequency
+fc = 1e9 # 20 dB corner frequency
+FDTD.SetGaussExcite(f0, fc)
+FDTD.SetBoundaryCond(['MUR', 'MUR', 'MUR', 'MUR', 'MUR', 'MUR']) # boundary conditions
+
+### Setup the Geometry & Mesh
+# init a cylindrical mesh
+CSX = CSXCAD.ContinuousStructure(CoordSystem=1)
+FDTD.SetCSX(CSX)
+mesh = CSX.GetGrid()
+mesh.SetDeltaUnit(unit)
+
+### Setup the geometry using cylindrical coordinates
+# calculate some width as an angle in radiant
+patch_ang_width = patch_width/(patch_radius+substrate_thickness)
+substr_ang_width = substrate_width/patch_radius
+feed_angle = feed_pos/patch_radius
+
+# create patch
+patch = CSX.AddMetal('patch') # create a perfect electric conductor (PEC)
+start = [patch_radius+substrate_thickness, -patch_ang_width/2, -patch_length/2 ]
+stop = [patch_radius+substrate_thickness, patch_ang_width/2, patch_length/2 ]
+CSX.AddBox(patch, priority=10, start=start, stop=stop, edges2grid='all') # add a box-primitive to the metal property 'patch'
+
+# create substrate
+substrate = CSX.AddMaterial('substrate', epsilon=substrate_epsR, kappa=substrate_kappa )
+start = [patch_radius , -substr_ang_width/2, -substrate_length/2]
+stop = [patch_radius+substrate_thickness, substr_ang_width/2, substrate_length/2]
+substrate.AddBox(start=start, stop=stop, edges2grid='all')
+
+# save current density oon the patch
+jt_patch = CSX.AddDump('Jt_patch', dump_type=3, file_type=1)
+start = [patch_radius+substrate_thickness, -substr_ang_width/2, -substrate_length/2]
+stop = [patch_radius+substrate_thickness, +substr_ang_width/2, substrate_length/2]
+jt_patch.AddBox(start=start, stop=stop)
+
+# create ground
+gnd = CSX.AddMetal('gnd') # create a perfect electric conductor (PEC)
+start = [patch_radius, -substr_ang_width/2, -substrate_length/2]
+stop = [patch_radius, +substr_ang_width/2, +substrate_length/2]
+gnd.AddBox(priority=10, start=start, stop=stop, edges2grid='all')
+
+# apply the excitation & resist as a current source
+start = [patch_radius , feed_angle, 0]
+stop = [patch_radius+substrate_thickness, feed_angle, 0]
+port = FDTD.AddLumpedPort(1 ,feed_R, start, stop, 'r', 1.0, priority=50, edges2grid='all')
+
+### Finalize the Mesh
+# add the simulation domain size
+mesh.AddLine('r', patch_radius+np.array([-20, SimBox_rad]))
+mesh.AddLine('a', [-0.75*pi, 0.75*pi])
+mesh.AddLine('z', [-SimBox_height/2, SimBox_height/2])
+
+# add some lines for the substrate
+mesh.AddLine('r', patch_radius+np.linspace(0,substrate_thickness,substrate_cells))
+
+# generate a smooth mesh with max. cell size: lambda_min / 20
+max_res = C0 / (f0+fc) / unit / 20
+max_ang = max_res/(SimBox_rad+patch_radius) # max res in radiant
+mesh.SmoothMeshLines(0, max_res, 1.4)
+mesh.SmoothMeshLines(1, max_ang, 1.4)
+mesh.SmoothMeshLines(2, max_res, 1.4)
+
+## Add the nf2ff recording box
+nf2ff = FDTD.CreateNF2FFBox()
+
+### Run the simulation
+if 0: # debugging only
+ CSX_file = os.path.join(Sim_Path, 'bent_patch.xml')
+ if not os.path.exists(Sim_Path):
+ os.mkdir(Sim_Path)
+ CSX.Write2XML(CSX_file)
+ os.system(r'AppCSXCAD "{}"'.format(CSX_file))
+
+
+if not post_proc_only:
+ FDTD.Run(Sim_Path, verbose=3, cleanup=True)
+
+### Postprocessing & plotting
+f = np.linspace(max(1e9,f0-fc),f0+fc,401)
+port.CalcPort(Sim_Path, f)
+Zin = port.uf_tot / port.if_tot
+s11 = port.uf_ref/port.uf_inc
+s11_dB = 20.0*np.log10(np.abs(s11))
+
+figure()
+plot(f/1e9, s11_dB)
+grid()
+ylabel('s11 (dB)')
+xlabel('frequency (GHz)')
+
+P_in = 0.5*np.real(port.uf_tot * np.conj(port.if_tot)) # antenna feed power
+
+# plot feed point impedance
+figure()
+plot( f/1e6, real(Zin), 'k-', linewidth=2, label=r'$\Re(Z_{in})$' )
+grid()
+plot( f/1e6, imag(Zin), 'r--', linewidth=2, label=r'$\Im(Z_{in})$' )
+title( 'feed point impedance' )
+xlabel( 'frequency (MHz)' )
+ylabel( 'impedance ($\Omega$)' )
+legend( )
+
+
+idx = np.where((s11_dB<-10) & (s11_dB==np.min(s11_dB)))[0]
+if not len(idx)==1:
+ print('No resonance frequency found for far-field calulation')
+else:
+ f_res = f[idx[0]]
+ theta = np.arange(-180.0, 180.0, 2.0)
+ print("Calculate NF2FF")
+ nf2ff_res_phi0 = nf2ff.CalcNF2FF(Sim_Path, f_res, theta, 0, center=np.array([patch_radius+substrate_thickness, 0, 0])*unit, read_cached=True, outfile='nf2ff_xz.h5')
+
+ figure(figsize=(15, 7))
+ ax = subplot(121, polar=True)
+ E_norm = 20.0*np.log10(nf2ff_res_phi0.E_norm/np.max(nf2ff_res_phi0.E_norm)) + nf2ff_res_phi0.Dmax
+ ax.plot(np.deg2rad(theta), 10**(np.squeeze(E_norm)/20), linewidth=2, label='xz-plane')
+ ax.grid(True)
+ ax.set_xlabel('theta (deg)')
+ ax.set_theta_zero_location('N')
+ ax.set_theta_direction(-1)
+ ax.legend(loc=3)
+
+ phi = theta
+ nf2ff_res_theta90 = nf2ff.CalcNF2FF(Sim_Path, f_res, 90, phi, center=np.array([patch_radius+substrate_thickness, 0, 0])*unit, read_cached=True, outfile='nf2ff_xy.h5')
+
+ ax = subplot(122, polar=True)
+ E_norm = 20.0*np.log10(nf2ff_res_theta90.E_norm/np.max(nf2ff_res_theta90.E_norm)) + nf2ff_res_theta90.Dmax
+ ax.plot(np.deg2rad(phi), 10**(np.squeeze(E_norm)/20), linewidth=2, label='xy-plane')
+ ax.grid(True)
+ ax.set_xlabel('phi (deg)')
+ suptitle('Bent Patch Anteanna Pattern\nFrequency: {} GHz'.format(f_res/1e9), fontsize=14)
+ ax.legend(loc=3)
+
+ print( 'radiated power: Prad = {:.2e} Watt'.format(nf2ff_res_theta90.Prad[0]))
+ print( 'directivity: Dmax = {:.1f} ({:.1f} dBi)'.format(nf2ff_res_theta90.Dmax[0], 10*np.log10(nf2ff_res_theta90.Dmax[0])))
+ print( 'efficiency: nu_rad = {:.1f} %'.format(100*nf2ff_res_theta90.Prad[0]/real(P_in[idx[0]])))
+
+show()
+