150 lines
4.4 KiB
Python
150 lines
4.4 KiB
Python
# -*- coding: utf-8 -*-
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"""
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Created on Fri Dec 18 20:56:53 2015
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@author: thorsten
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"""
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### Import Libraries
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import os, tempfile
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from pylab import *
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from CSXCAD import ContinuousStructure
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from openEMS import openEMS
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from openEMS.physical_constants import *
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### General parameter setup
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Sim_Path = os.path.join(tempfile.gettempdir(), 'Simp_Patch')
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post_proc_only = False
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# patch width (resonant length) in x-direction
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patch_width = 32 #
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# patch length in y-direction
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patch_length = 40
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#substrate setup
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substrate_epsR = 3.38
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substrate_kappa = 1e-3 * 2*pi*2.45e9 * EPS0*substrate_epsR
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substrate_width = 60
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substrate_length = 60
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substrate_thickness = 1.524
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substrate_cells = 4
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#setup feeding
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feed_pos = -6 #feeding position in x-direction
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feed_R = 50 #feed resistance
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# size of the simulation box
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SimBox = np.array([200, 200, 150])
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# setup FDTD parameter & excitation function
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f0 = 2e9 # center frequency
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fc = 1e9 # 20 dB corner frequency
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### FDTD setup
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## * Limit the simulation to 30k timesteps
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## * Define a reduced end criteria of -40dB
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FDTD = openEMS(NrTS=30000, EndCriteria=1e-4)
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FDTD.SetGaussExcite( f0, fc )
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FDTD.SetBoundaryCond( ['MUR', 'MUR', 'MUR', 'MUR', 'MUR', 'MUR'] )
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CSX = ContinuousStructure()
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FDTD.SetCSX(CSX)
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mesh = CSX.GetGrid()
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mesh.SetDeltaUnit(1e-3)
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mesh_res = C0/(f0+fc)/1e-3/20
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### Generate properties, primitives and mesh-grid
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#initialize the mesh with the "air-box" dimensions
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mesh.AddLine('x', [-SimBox[0]/2, feed_pos, SimBox[0]/2])
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mesh.AddLine('y', [-SimBox[1]/2, SimBox[1]/2] )
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mesh.AddLine('z', [-SimBox[2]/3, SimBox[2]*2/3] )
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# create patch
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patch = CSX.AddMetal( 'patch' ) # create a perfect electric conductor (PEC)
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start = [-patch_width/2, -patch_length/2, substrate_thickness]
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stop = [ patch_width/2 , patch_length/2, substrate_thickness]
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pb=patch.AddBox(priority=10, start=start, stop=stop) # add a box-primitive to the metal property 'patch'
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pb.AddEdges2Grid('xy', metal_edge_res=mesh_res/2)
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# create substrate
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substrate = CSX.AddMaterial( 'substrate', epsilon=substrate_epsR, kappa=substrate_kappa)
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start = [-substrate_width/2, -substrate_length/2, 0]
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stop = [ substrate_width/2, substrate_length/2, substrate_thickness]
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sb=substrate.AddBox( priority=0, start=start, stop=stop )
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# add extra cells to discretize the substrate thickness
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mesh.AddLine('z', linspace(0,substrate_thickness,substrate_cells+1))
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# create ground (same size as substrate)
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gnd = CSX.AddMetal( 'gnd' ) # create a perfect electric conductor (PEC)
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start[2]=0
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stop[2] =0
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gb=gnd.AddBox(start, stop, priority=10, edges2grid='all')
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# apply the excitation & resist as a current source
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start = [feed_pos, 0, 0]
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stop = [feed_pos, 0, substrate_thickness]
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port = FDTD.AddLumpedPort(1 ,feed_R, start, stop, 'z', 1.0, priority=5, edges2grid='all')
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mesh.SmoothMeshLines('all', mesh_res, 1.4)
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# Add the nf2ff recording box
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nf2ff = FDTD.CreateNF2FFBox()
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### Run the simulation
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if 0: # debugging only
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CSX_file = os.path.join(Sim_Path, 'simp_patch.xml')
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if not os.path.exists(Sim_Path):
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os.mkdir(Sim_Path)
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CSX.Write2XML(CSX_file)
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os.system(r'AppCSXCAD "{}"'.format(CSX_file))
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if not post_proc_only:
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FDTD.Run(Sim_Path, verbose=3, cleanup=True)
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### Post-processing and plotting
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f = np.linspace(max(1e9,f0-fc),f0+fc,401)
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port.CalcPort(Sim_Path, f)
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s11 = port.uf_ref/port.uf_inc
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s11_dB = 20.0*np.log10(np.abs(s11))
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figure()
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plot(f/1e9, s11_dB, 'k-', linewidth=2, label='$S_{11}$')
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grid()
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legend()
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ylabel('S-Parameter (dB)')
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xlabel('Frequency (GHz)')
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idx = np.where((s11_dB<-10) & (s11_dB==np.min(s11_dB)))[0]
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if not len(idx)==1:
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print('No resonance frequency found for far-field calulation')
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else:
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f_res = f[idx[0]]
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theta = np.arange(-180.0, 180.0, 2.0)
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phi = [0., 90.]
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nf2ff_res = nf2ff.CalcNF2FF(Sim_Path, f_res, theta, phi, center=[0,0,1e-3])
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figure()
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E_norm = 20.0*np.log10(nf2ff_res.E_norm[0]/np.max(nf2ff_res.E_norm[0])) + nf2ff_res.Dmax[0]
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plot(theta, np.squeeze(E_norm[:,0]), 'k-', linewidth=2, label='xz-plane')
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plot(theta, np.squeeze(E_norm[:,1]), 'r--', linewidth=2, label='yz-plane')
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grid()
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ylabel('Directivity (dBi)')
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xlabel('Theta (deg)')
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title('Frequency: {} GHz'.format(f_res/1e9))
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legend()
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Zin = port.uf_tot/port.if_tot
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figure()
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plot(f/1e9, np.real(Zin), 'k-', linewidth=2, label='$\Re\{Z_{in}\}$')
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plot(f/1e9, np.imag(Zin), 'r--', linewidth=2, label='$\Im\{Z_{in}\}$')
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grid()
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legend()
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ylabel('Zin (Ohm)')
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xlabel('Frequency (GHz)')
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show()
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