# -*- coding: utf-8 -*- """ Tutorials / CRLH_Extraction Describtion at: http://openems.de/index.php/Tutorial:_CRLH_Extraction Tested with - python 3.4 - openEMS v0.0.34+ (C) 2016 Thorsten Liebig """ ### Import Libraries import os, tempfile from pylab import * from CSXCAD import ContinuousStructure from openEMS import openEMS from openEMS.physical_constants import * ### Class to represent single CRLH unit cells class CRLH_Cells: def __init__(self, LL, LW, Top, Bot, GLT, GLB, SL, SW, VR): self.LL = LL # Line length self.LW = LW # Line width self.Top = Top # top signal height self.Bot = Bot # bottom signal height self.GLT = GLT # gap length top self.GLB = GLB # gap length bottom self.SL = SL # stub length self.SW = SW # stub width self.VR = VR # via radius self.props = dict() # property dictionary self.edge_resolution = None def createProperties(self, CSX): for p in ['metal_top', 'metal_bot', 'via']: self.props[p] = CSX.AddMetal(p) def setEdgeResolution(self, res): self.edge_resolution = res def createCell(self, translate = [0,0,0]): def append_mesh(mesh1, mesh2): for n in range(3): if mesh1[n] is None: mesh1[n] = mesh2[n] elif mesh2[n] is None: continue else: mesh1[n] += mesh2[n] return mesh1 translate = array(translate) start = [-self.LL/2 , -self.LW/2, self.Top] + translate stop = [-self.GLT/2, self.LW/2, self.Top] + translate box = self.props['metal_top'].AddBox(start, stop, priority=10) mesh = box.GetGridHint('x', metal_edge_res=self.edge_resolution, down_dir=False) append_mesh(mesh, box.GetGridHint('y', metal_edge_res=self.edge_resolution) ) start = [+self.LL/2 , -self.LW/2, self.Top] + translate stop = [+self.GLT/2, self.LW/2, self.Top] + translate box = self.props['metal_top'].AddBox(start, stop, priority=10) append_mesh(mesh, box.GetGridHint('x', metal_edge_res=self.edge_resolution, up_dir=False) ) start = [-(self.LL-self.GLB)/2, -self.LW/2, self.Bot] + translate stop = [+(self.LL-self.GLB)/2, self.LW/2, self.Bot] + translate box = self.props['metal_bot'].AddBox(start, stop, priority=10) append_mesh(mesh, box.GetGridHint('x', metal_edge_res=self.edge_resolution) ) start = [-self.SW/2, -self.LW/2-self.SL, self.Bot] + translate stop = [+self.SW/2, self.LW/2+self.SL, self.Bot] + translate box = self.props['metal_bot'].AddBox(start, stop, priority=10) append_mesh(mesh, box.GetGridHint('xy', metal_edge_res=self.edge_resolution) ) start = [0, -self.LW/2-self.SL+self.SW/2, 0 ] + translate stop = [0, -self.LW/2-self.SL+self.SW/2, self.Bot] + translate self.props['via'].AddCylinder(start, stop, radius=self.VR, priority=10) start[1] *= -1 stop [1] *= -1 self.props['via'].AddCylinder(start, stop, radius=self.VR, priority=10) return mesh if __name__ == '__main__': ### Setup the simulation Sim_Path = os.path.join(tempfile.gettempdir(), 'CRLH_Extraction') post_proc_only = False unit = 1e-6 # specify everything in um feed_length = 30000 substrate_thickness = [1524, 101 , 254 ] substrate_epsr = [3.48, 3.48, 3.48] CRLH = CRLH_Cells(LL = 14e3, LW = 4e3, GLB = 1950, GLT = 4700, SL = 7800, SW = 1000, VR = 250 , \ Top = sum(substrate_thickness), \ Bot = sum(substrate_thickness[:-1])) # frequency range of interest f_start = 0.8e9 f_stop = 6e9 ### Setup FDTD parameters & excitation function CSX = ContinuousStructure() FDTD = openEMS(EndCriteria=1e-5) FDTD.SetCSX(CSX) mesh = CSX.GetGrid() mesh.SetDeltaUnit(unit) CRLH.createProperties(CSX) FDTD.SetGaussExcite((f_start+f_stop)/2, (f_stop-f_start)/2 ) BC = {'PML_8' 'PML_8' 'MUR' 'MUR' 'PEC' 'PML_8'} FDTD.SetBoundaryCond( ['PML_8', 'PML_8', 'MUR', 'MUR', 'PEC', 'PML_8'] ) ### Setup a basic mesh and create the CRLH unit cell resolution = C0/(f_stop*sqrt(max(substrate_epsr)))/unit /30 # resolution of lambda/30 CRLH.setEdgeResolution(resolution/4) mesh.SetLines('x', [-feed_length-CRLH.LL/2, 0, feed_length+CRLH.LL/2]) mesh.SetLines('y', [-30000, 0, 30000]) substratelines = cumsum(substrate_thickness) mesh.SetLines('z', [0, 20000]) mesh.AddLine('z', cumsum(substrate_thickness)) mesh.AddLine('z', linspace(substratelines[-2],substratelines[-1],4)) # create the CRLH unit cell (will define additional fixed mesh lines) mesh_hint = CRLH.createCell() mesh.AddLine('x', mesh_hint[0]) mesh.AddLine('y', mesh_hint[1]) # Smooth the given mesh mesh.SmoothMeshLines('all', resolution, 1.2) ### Setup the substrate layer substratelines = [0] + substratelines.tolist() start, stop = mesh.GetSimArea() for n in range(len(substrate_thickness)): sub = CSX.AddMaterial( 'substrate_{}'.format(n), epsilon=substrate_epsr[n] ) start[2] = substratelines[n] stop [2] = substratelines[n+1] sub.AddBox( start, stop ) ### Add the feeding MSL ports pec = CSX.AddMetal( 'PEC' ) port = [None, None] x_lines = mesh.GetLines('x') portstart = [ x_lines[0], -CRLH.LW/2, substratelines[-1]] portstop = [ -CRLH.LL/2, CRLH.LW/2, 0] port[0] = FDTD.AddMSLPort( 1, pec, portstart, portstop, 'x', 'z', excite=-1, FeedShift=10*resolution, MeasPlaneShift=feed_length/2, priority=10) portstart = [ x_lines[-1], -CRLH.LW/2, substratelines[-1]] portstop = [ +CRLH.LL/2 , CRLH.LW/2, 0] port[1] = FDTD.AddMSLPort( 2, pec, portstart, portstop, 'x', 'z', MeasPlaneShift=feed_length/2, priority=10) ### Run the simulation if 1: # debugging only CSX_file = os.path.join(Sim_Path, 'CRLH_Extraction.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) ### Post-Processing f = linspace( f_start, f_stop, 1601 ) for p in port: p.CalcPort( Sim_Path, f, ref_impedance = 50, ref_plane_shift = feed_length) # calculate and plot scattering parameter s11 = port[0].uf_ref / port[0].uf_inc s21 = port[1].uf_ref / port[0].uf_inc plot(f/1e9,20*log10(abs(s11)),'k-' , linewidth=2, label='$S_{11}$') plot(f/1e9,20*log10(abs(s21)),'r--', linewidth=2, label='$S_{21}$') grid() legend(loc=3) ylabel('S-Parameter (dB)') xlabel('frequency (GHz)') ylim([-40, 2]) ### Extract CRLH parameter form ABCD matrix A = ((1+s11)*(1-s11) + s21*s21)/(2*s21) C = ((1-s11)*(1-s11) - s21*s21)/(2*s21) / port[1].Z_ref Y = C Z = 2*(A-1)/C iZ = imag(Z) iY = imag(Y) fse = interp(0, iZ, f) fsh = interp(0, iY, f) df = f[1]-f[0] fse_idx = np.where(f>fse)[0][0] fsh_idx = np.where(f>fsh)[0][0] LR = 0.5*(iZ[fse_idx]-iZ[fse_idx-1])/(2*pi*df) CL = 1/(2*pi*fse)**2/LR CR = 0.5*(iY[fsh_idx]-iY[fsh_idx-1])/(2*pi*df) LL = 1/(2*pi*fsh)**2/CR print(' Series tank: CL = {:.2f} pF, LR = {:.2f} nH -> f_se = {:.2f} GHz '.format(CL*1e12, LR*1e9, fse*1e-9)) print(' Shunt tank: CR = {:.2f} pF, LL = {:.2f} nH -> f_sh = {:.2f} GHz '.format(CR*1e12, LL*1e9, fsh*1e-9)) ### Calculate analytical wave-number of an inf-array of cells w = 2*pi*f wse = 2*pi*fse wsh = 2*pi*fsh beta_calc = real(arccos(1-(w**2-wse**2)*(w**2-wsh**2)/(2*w**2/CR/LR))) # plot figure() beta = -angle(s21)/CRLH.LL/unit plot(abs(beta)*CRLH.LL*unit/pi,f*1e-9,'k-', linewidth=2, label=r'$\beta_{CRLH,\ 1\ cell}$' ) grid() plot(beta_calc/pi,f*1e-9,'c--', linewidth=2, label=r'$\beta_{CRLH,\ \infty\ cells}$') plot(real(port[1].beta)*CRLH.LL*unit/pi,f*1e-9,'g-', linewidth=2, label=r'$\beta_{MSL}$') ylim([1, 6]) xlabel(r'$|\beta| p / \pi$') ylabel('frequency (GHz)') legend(loc=2) show()