153 lines
4.5 KiB
Python
153 lines
4.5 KiB
Python
# -*- coding: utf-8 -*-
|
|
"""
|
|
Created on Fri Dec 18 20:56:53 2015
|
|
|
|
@author: thorsten
|
|
"""
|
|
|
|
### Import Libraries
|
|
import os, tempfile
|
|
from pylab import *
|
|
|
|
from CSXCAD import ContinuousStructure
|
|
from openEMS import openEMS
|
|
from openEMS.physical_constants import *
|
|
|
|
### General parameter setup
|
|
Sim_Path = os.path.join(tempfile.gettempdir(), 'Simp_Patch')
|
|
|
|
post_proc_only = False
|
|
|
|
# patch width (resonant length) in x-direction
|
|
patch_width = 32 #
|
|
# patch length in y-direction
|
|
patch_length = 40
|
|
|
|
#substrate setup
|
|
substrate_epsR = 3.38
|
|
substrate_kappa = 1e-3 * 2*pi*2.45e9 * EPS0*substrate_epsR
|
|
substrate_width = 60
|
|
substrate_length = 60
|
|
substrate_thickness = 1.524
|
|
substrate_cells = 4
|
|
|
|
#setup feeding
|
|
feed_pos = -6 #feeding position in x-direction
|
|
feed_R = 50 #feed resistance
|
|
|
|
# size of the simulation box
|
|
SimBox = np.array([200, 200, 150])
|
|
|
|
# setup FDTD parameter & excitation function
|
|
f0 = 2e9 # center frequency
|
|
fc = 1e9 # 20 dB corner frequency
|
|
|
|
### FDTD setup
|
|
## * Limit the simulation to 30k timesteps
|
|
## * Define a reduced end criteria of -40dB
|
|
FDTD = openEMS(NrTS=30000, EndCriteria=1e-4)
|
|
FDTD.SetGaussExcite( f0, fc )
|
|
FDTD.SetBoundaryCond( ['MUR', 'MUR', 'MUR', 'MUR', 'MUR', 'MUR'] )
|
|
|
|
|
|
CSX = ContinuousStructure()
|
|
FDTD.SetCSX(CSX)
|
|
mesh = CSX.GetGrid()
|
|
mesh.SetDeltaUnit(1e-3)
|
|
mesh_res = C0/(f0+fc)/1e-3/20
|
|
|
|
### Generate properties, primitives and mesh-grid
|
|
#initialize the mesh with the "air-box" dimensions
|
|
mesh.AddLine('x', [-SimBox[0]/2, SimBox[0]/2])
|
|
mesh.AddLine('y', [-SimBox[1]/2, SimBox[1]/2] )
|
|
mesh.AddLine('z', [-SimBox[2]/3, SimBox[2]*2/3] )
|
|
|
|
# create patch
|
|
patch = CSX.AddMetal( 'patch' ) # create a perfect electric conductor (PEC)
|
|
start = [-patch_width/2, -patch_length/2, substrate_thickness]
|
|
stop = [ patch_width/2 , patch_length/2, substrate_thickness]
|
|
patch.AddBox(priority=10, start=start, stop=stop) # add a box-primitive to the metal property 'patch'
|
|
FDTD.AddEdges2Grid(dirs='xy', properties=patch, metal_edge_res=mesh_res/2)
|
|
|
|
# create substrate
|
|
substrate = CSX.AddMaterial( 'substrate', epsilon=substrate_epsR, kappa=substrate_kappa)
|
|
start = [-substrate_width/2, -substrate_length/2, 0]
|
|
stop = [ substrate_width/2, substrate_length/2, substrate_thickness]
|
|
substrate.AddBox( priority=0, start=start, stop=stop )
|
|
|
|
# add extra cells to discretize the substrate thickness
|
|
mesh.AddLine('z', linspace(0,substrate_thickness,substrate_cells+1))
|
|
|
|
# create ground (same size as substrate)
|
|
gnd = CSX.AddMetal( 'gnd' ) # create a perfect electric conductor (PEC)
|
|
start[2]=0
|
|
stop[2] =0
|
|
gnd.AddBox(start, stop, priority=10)
|
|
|
|
FDTD.AddEdges2Grid(dirs='xy', properties=gnd)
|
|
|
|
# apply the excitation & resist as a current source
|
|
start = [feed_pos, 0, 0]
|
|
stop = [feed_pos, 0, substrate_thickness]
|
|
port = FDTD.AddLumpedPort(1, feed_R, start, stop, 'z', 1.0, priority=5, edges2grid='xy')
|
|
|
|
mesh.SmoothMeshLines('all', mesh_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, 'simp_patch.xml')
|
|
if not os.path.exists(Sim_Path):
|
|
os.mkdir(Sim_Path)
|
|
CSX.Write2XML(CSX_file)
|
|
from CSXCAD import AppCSXCAD_BIN
|
|
os.system(AppCSXCAD_BIN + ' "{}"'.format(CSX_file))
|
|
|
|
if not post_proc_only:
|
|
FDTD.Run(Sim_Path, verbose=3, cleanup=True)
|
|
|
|
|
|
### Post-processing and plotting
|
|
f = np.linspace(max(1e9,f0-fc),f0+fc,401)
|
|
port.CalcPort(Sim_Path, f)
|
|
s11 = port.uf_ref/port.uf_inc
|
|
s11_dB = 20.0*np.log10(np.abs(s11))
|
|
figure()
|
|
plot(f/1e9, s11_dB, 'k-', linewidth=2, label='$S_{11}$')
|
|
grid()
|
|
legend()
|
|
ylabel('S-Parameter (dB)')
|
|
xlabel('Frequency (GHz)')
|
|
|
|
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)
|
|
phi = [0., 90.]
|
|
nf2ff_res = nf2ff.CalcNF2FF(Sim_Path, f_res, theta, phi, center=[0,0,1e-3])
|
|
|
|
figure()
|
|
E_norm = 20.0*np.log10(nf2ff_res.E_norm[0]/np.max(nf2ff_res.E_norm[0])) + nf2ff_res.Dmax[0]
|
|
plot(theta, np.squeeze(E_norm[:,0]), 'k-', linewidth=2, label='xz-plane')
|
|
plot(theta, np.squeeze(E_norm[:,1]), 'r--', linewidth=2, label='yz-plane')
|
|
grid()
|
|
ylabel('Directivity (dBi)')
|
|
xlabel('Theta (deg)')
|
|
title('Frequency: {} GHz'.format(f_res/1e9))
|
|
legend()
|
|
|
|
Zin = port.uf_tot/port.if_tot
|
|
figure()
|
|
plot(f/1e9, np.real(Zin), 'k-', linewidth=2, label='$\Re\{Z_{in}\}$')
|
|
plot(f/1e9, np.imag(Zin), 'r--', linewidth=2, label='$\Im\{Z_{in}\}$')
|
|
grid()
|
|
legend()
|
|
ylabel('Zin (Ohm)')
|
|
xlabel('Frequency (GHz)')
|
|
|
|
show()
|