125 lines
3.3 KiB
Python
125 lines
3.3 KiB
Python
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# -*- coding: utf-8 -*-
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"""
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Created on Tue Dec 29 15:40:23 2015
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Tutorials / Rect_Waveguide
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Describtion at:
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http://openems.de/index.php/Tutorial:_Rectangular_Waveguide
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Tested with
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- python 3.4
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- openEMS v0.0.33+
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(C) 2015-2016 Thorsten Liebig <thorsten.liebig@gmx.de>
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"""
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import os, tempfile
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from pylab import *
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from CSXCAD import CSXCAD
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from openEMS.openEMS import openEMS
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from openEMS.physical_constants import *
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Sim_Path = os.path.join(tempfile.gettempdir(), 'Rect_WG')
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## setup the simulation ###################################################
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post_proc_only = False
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unit = 1e-6; #drawing unit in um
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# waveguide dimensions
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# WR42
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a = 10700; #waveguide width
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b = 4300; #waveguide heigth
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length = 50000;
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# frequency range of interest
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f_start = 20e9;
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f_0 = 24e9;
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f_stop = 26e9;
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lambda0 = C0/f_0/unit;
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#waveguide TE-mode definition
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TE_mode = 'TE10';
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#targeted mesh resolution
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mesh_res = lambda0/30
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## setup FDTD parameter & excitation function #############################
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FDTD = openEMS(NrTS=1e4);
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FDTD.SetGaussExcite(0.5*(f_start+f_stop),0.5*(f_stop-f_start));
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# boundary conditions
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FDTD.SetBoundaryCond([0, 0, 0, 0, 3, 3]);
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## setup CSXCAD geometry & mesh
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CSX = CSXCAD.ContinuousStructure()
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FDTD.SetCSX(CSX)
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mesh = CSX.GetGrid()
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mesh.SetDeltaUnit(unit)
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mesh.AddLine('x', [0, a])
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mesh.AddLine('y', [0, b])
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mesh.AddLine('z', [0, length])
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## apply the waveguide port ###################################################
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ports = []
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start=[0, 0, 10*mesh_res];
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stop =[a, b, 15*mesh_res];
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mesh.AddLine('z', [start[2], stop[2]])
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ports.append(FDTD.AddRectWaveGuidePort( 0, start, stop, 'z', a*unit, b*unit, TE_mode, 1))
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start=[0, 0, length-10*mesh_res];
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stop =[a, b, length-15*mesh_res];
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mesh.AddLine('z', [start[2], stop[2]])
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ports.append(FDTD.AddRectWaveGuidePort( 1, start, stop, 'z', a*unit, b*unit, TE_mode))
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mesh.SmoothMeshLines('all', mesh_res, ratio=1.4)
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## define dump box... #####################################################
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Et = CSX.AddDump('Et', file_type=0, sub_sampling=[2,2,2])
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start = [0, 0, 0];
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stop = [a, b, length];
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CSX.AddBox(Et, start, stop);
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## Write openEMS compatoble xml-file ######################################
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if 0: # debugging only
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CSX_file = os.path.join(Sim_Path, 'rect_wg.xml')
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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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### postproc ###############################################################
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freq = linspace(f_start,f_stop,201)
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for port in ports:
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port.CalcPort(Sim_Path, freq)
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s11 = ports[0].uf_ref / ports[0].uf_inc
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s21 = ports[1].uf_ref / ports[0].uf_inc
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ZL = ports[0].uf_tot / ports[0].if_tot
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ZL_a = ports[0].ZL # analytic waveguide impedance
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## plot s-parameter #######################################################
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figure()
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plot(freq*1e-6,20*log10(abs(s11)),'k-',linewidth=2, label='$S_{11}$')
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grid()
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plot(freq*1e-6,20*log10(abs(s21)),'r--',linewidth=2, label='$S_{21}$')
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legend();
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ylabel('S-Parameter (dB)')
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xlabel(r'frequency (MHz) $\rightarrow$')
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## compare analytic and numerical wave-impedance ##########################
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figure()
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plot(freq*1e-6,real(ZL), linewidth=2, label='$\Re\{Z_L\}$')
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grid()
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plot(freq*1e-6,imag(ZL),'r--', linewidth=2, label='$\Im\{Z_L\}$')
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plot(freq*1e-6,ZL_a,'g-.',linewidth=2, label='$Z_{L, analytic}$')
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ylabel('ZL $(\Omega)$')
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xlabel(r'frequency (MHz) $\rightarrow$')
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legend()
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show()
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