NawfalMotii79
256 lines
9.3 KiB
Python
256 lines
9.3 KiB
Python
# openems_quartz_slotted_wg_10p5GHz.py
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# Full script: geometry, mesh (no GetLine calls), S-params/impedance sweep, 3D pattern & gain.
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# Requires: openEMS (Python bindings), CSXCAD (Python), matplotlib, numpy.
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import os
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import tempfile
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import numpy as np
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import matplotlib.pyplot as plt
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from CSXCAD import ContinuousStructure, AppCSXCAD_BIN
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from openEMS import openEMS
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from openEMS.physical_constants import C0
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# -------------------------
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# User controls
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# -------------------------
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view_geom_in_AppCSXCAD = True # True => launch AppCSXCAD to view 3D geometry
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simulate = True # False => skip FDTD run
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threads = 0 # 0 => auto/max
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# Far-field angular sampling
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n_theta, n_phi = 91, 181 # theta 0..180, phi 0..360
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# -------------------------
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# Band & element sizing
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# -------------------------
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f0 = 10.5e9
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f_span = 2.0e9
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f_start, f_stop = f0 - f_span/2, f0 + f_span/2
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# Quartz-filled rectangular waveguide (full dielectric block)
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er_quartz = 3.8
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# Array-driven constraints (λ0/2 column pitch, 1 mm septum) ⇒ a ~ 13.28 mm
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a = 13.28 # mm (broad wall, internal)
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b = 6.50 # mm (narrow wall, internal; comfortable to machine)
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L = 281.0 # mm (≈32-slot column incl. λg/4 margins at 10.5 GHz)
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# Slot starters (tune in EM for taper)
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slot_w = 0.60 # mm (across x)
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lambda0_mm = (C0/f0) * 1e3
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fc10 = (C0/(2.0*np.sqrt(er_quartz))) * (1.0/(a*1e-3)) # Hz
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lambda_d = (C0/f0) / np.sqrt(er_quartz) # m
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lambda_g = lambda_d / np.sqrt(1.0 - (fc10/f0)**2) # m
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lambda_g_mm = lambda_g * 1e3
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slot_s = 0.5*lambda_g_mm
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slot_L = 0.47*lambda_g_mm
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margin = 0.25*lambda_g_mm
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Nslots = 32
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delta0 = 0.90 # mm offset from centerline (± alternated)
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# Metal & air padding for the radiation domain
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t_metal = 0.8 # mm wall thickness
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air_x = 10.0 # mm on each side
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air_y = 40.0 # mm above slots
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air_z = 15.0 # mm front/back
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# Mesh resolution target (mm)
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mesh_res = min(0.5, lambda0_mm/30.0)
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# -------------------------
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# Build FDTD & CSX
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# -------------------------
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unit = 1e-3 # mm
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Sim_Path = os.path.join(tempfile.gettempdir(), 'openems_quartz_slotted_wg')
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FDTD = openEMS(NrTS=int(6e5), EndCriteria=1e-5)
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FDTD.SetGaussExcite(0.5*(f_start+f_stop), 0.5*(f_stop-f_start))
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FDTD.SetBoundaryCond(['PML_8']*6)
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FDTD.SetOverSampling(4)
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FDTD.SetTimeStepFactor(0.95)
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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(unit)
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# -------------------------
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# Geometry extents (mm)
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# -------------------------
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x_min, x_max = -air_x, a + air_x
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y_min, y_max = -5.0, b + t_metal + air_y
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z_min, z_max = -air_z, L + air_z
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# Slot centers and edges (mm)
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z_centers = margin + np.arange(Nslots)*slot_s
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x_centers = (a/2.0) + np.array([+delta0 if i%2==0 else -delta0 for i in range(Nslots)])
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x_edges = np.concatenate([x_centers - slot_w/2.0, x_centers + slot_w/2.0])
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z_edges = np.concatenate([z_centers - slot_L/2.0, z_centers + slot_L/2.0])
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# -------------------------
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# Mesh lines — EXPLICIT (no GetLine calls)
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# -------------------------
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x_lines = sorted(set([x_min, -t_metal, 0.0, a, a+t_metal, x_max] + list(x_edges)))
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y_lines = [y_min, 0.0, b, b+t_metal, y_max]
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z_lines = sorted(set([z_min, 0.0, L, z_max] + list(z_edges)))
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mesh.AddLine('x', x_lines)
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mesh.AddLine('y', y_lines)
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mesh.AddLine('z', z_lines)
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# Optional smoothing to max cell size around ~mesh_res
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mesh.SmoothMeshLines('all', mesh_res, ratio=1.4)
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# -------------------------
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# Materials
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# -------------------------
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pec = CSX.AddMetal('PEC')
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quartz = CSX.AddMaterial('QUARTZ'); quartz.SetMaterialProperty(epsilon=er_quartz)
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air = CSX.AddMaterial('AIR') # explicit for slot holes
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# -------------------------
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# Solids: quartz block + metal walls + slots
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# -------------------------
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# Quartz full block (inside tube)
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quartz.AddBox([0, 0, 0], [a, b, L])
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# PEC tube: left/right/bottom/top (top will be perforated by slots)
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pec.AddBox([-t_metal, 0, 0], [0, b, L]) # left
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pec.AddBox([a, 0, 0], [a+t_metal,b, L]) # right
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pec.AddBox([-t_metal,-t_metal,0],[a+t_metal,0, L]) # bottom
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pec.AddBox([-t_metal, b, 0], [a+t_metal,b+t_metal,L]) # top
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# Slots = AIR boxes overriding the top metal
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for zc, xc in zip(z_centers, x_centers):
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x1, x2 = xc - slot_w/2.0, xc + slot_w/2.0
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z1, z2 = zc - slot_L/2.0, zc + slot_L/2.0
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prim = air.AddBox([x1, b, z1], [x2, b+t_metal, z2])
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prim.SetPriority(10) # ensure it cuts the metal
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# -------------------------
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# Ports: Rectangular WG TE10, z-directed
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# -------------------------
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port_thick = max(4*mesh_res, 2.0) # mm
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p1_start = [0, 0, max(0.5, 10*mesh_res)]
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p1_stop = [a, b, p1_start[2] + port_thick]
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FDTD.AddRectWaveGuidePort(port_nr=1, start=p1_start, stop=p1_stop,
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p_dir='z', a=a*unit, b=b*unit, mode_name='TE10', excite=1)
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p2_stop = [a, b, L - max(0.5, 10*mesh_res)]
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p2_start = [0, 0, p2_stop[2] - port_thick]
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FDTD.AddRectWaveGuidePort(port_nr=2, start=p2_start, stop=p2_stop,
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p_dir='z', a=a*unit, b=b*unit, mode_name='TE10', excite=0)
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# -------------------------
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# NF2FF setup (surround the radiator region)
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# -------------------------
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def create_nf2ff(FDTD_obj, name, start, stop, frequency):
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"""Compat wrapper: older/newer openEMS builds may expose NF2FF creation differently."""
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try:
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return FDTD_obj.CreateNF2FFBox(name=name, start=start, stop=stop, frequency=frequency)
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except AttributeError:
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# Fallback: try AddNF2FFBox returning a handle-like object
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return FDTD_obj.AddNF2FFBox(name=name, start=start, stop=stop, frequency=frequency)
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nf2ff = create_nf2ff(
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FDTD,
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name='nf2ff',
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start=[x_min+1.0, y_min+1.0, z_min+1.0],
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stop =[x_max-1.0, y_max-1.0, z_max-1.0],
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frequency=[f0]
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)
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# -------------------------
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# (Optional) view geometry
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# -------------------------
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if view_geom_in_AppCSXCAD:
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os.makedirs(Sim_Path, exist_ok=True)
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csx_xml = os.path.join(Sim_Path, 'quartz_slotted_wg.xml')
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CSX.Write2XML(csx_xml)
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os.system(f'"{AppCSXCAD_BIN}" "{csx_xml}"')
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# -------------------------
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# Run FDTD
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# -------------------------
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if simulate:
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FDTD.Run(Sim_Path, cleanup=True, verbose=2, numThreads=threads)
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# -------------------------
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# Post-processing: S-params & impedance
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# -------------------------
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freq = np.linspace(f_start, f_stop, 401)
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ports = [p for p in FDTD.ports] # Port 1 & Port 2 in creation order
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for p in ports:
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p.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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Zin = ports[0].uf_tot / ports[0].if_tot
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plt.figure(figsize=(7.6,4.6))
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plt.plot(freq*1e-9, 20*np.log10(np.abs(S11)), lw=2, label='|S11|')
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plt.plot(freq*1e-9, 20*np.log10(np.abs(S21)), lw=2, ls='--', label='|S21|')
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plt.grid(True); plt.legend(); plt.xlabel('Frequency (GHz)'); plt.ylabel('Magnitude (dB)')
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plt.title('S-Parameters: Slotted Quartz-Filled WG')
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plt.figure(figsize=(7.6,4.6))
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plt.plot(freq*1e-9, np.real(Zin), lw=2, label='Re{Zin}')
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plt.plot(freq*1e-9, np.imag(Zin), lw=2, ls='--', label='Im{Zin}')
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plt.grid(True); plt.legend(); plt.xlabel('Frequency (GHz)'); plt.ylabel('Ohms')
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plt.title('Input Impedance (Port 1)')
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# -------------------------
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# Far-field @ f0 and 3D pattern
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# -------------------------
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theta = np.linspace(0, np.pi, n_theta)
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phi = np.linspace(0, 2*np.pi, n_phi)
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# Compatibility: some builds expect nf2ff.CalcNF2FF(...), others FDTD.CalcNF2FF(nf2ff,...)
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try:
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res = nf2ff.CalcNF2FF(Sim_Path, [f0], theta, phi)
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except AttributeError:
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res = FDTD.CalcNF2FF(nf2ff, Sim_Path, [f0], theta, phi)
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# Max directivity (linear) & realized gain estimate
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idx_f0 = np.argmin(np.abs(freq - f0))
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Dmax_lin = float(res.Dmax[0]) # at f0
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mismatch = 1.0 - np.abs(S11[idx_f0])**2 # (1 - |S11|^2)
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Gmax_lin = Dmax_lin * float(mismatch)
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Gmax_dBi = 10*np.log10(Gmax_lin)
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print(f"Max directivity @ {f0/1e9:.3f} GHz: {10*np.log10(Dmax_lin):.2f} dBi")
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print(f"Mismatch term (1-|S11|^2) : {float(mismatch):.3f}")
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print(f"Estimated max realized gain : {Gmax_dBi:.2f} dBi")
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# 3D normalized pattern
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E = np.squeeze(res.E_norm) # shape [f, th, ph] -> [th, ph]
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E = E / np.max(E)
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TH, PH = np.meshgrid(theta, phi, indexing='ij')
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R = E
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X = R * np.sin(TH) * np.cos(PH)
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Y = R * np.sin(TH) * np.sin(PH)
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Z = R * np.cos(TH)
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fig = plt.figure(figsize=(7.2,6.2))
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ax = fig.add_subplot(111, projection='3d')
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ax.plot_surface(X, Y, Z, rstride=2, cstride=2, linewidth=0, antialiased=True, alpha=0.92)
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ax.set_title(f'Normalized 3D Pattern @ {f0/1e9:.2f} GHz\n(peak ≈ {Gmax_dBi:.1f} dBi)')
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ax.set_box_aspect((1,1,1))
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ax.set_xlabel('x'); ax.set_ylabel('y'); ax.set_zlabel('z')
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plt.tight_layout()
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# Quick 2D geometry preview (top view at y=b)
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plt.figure(figsize=(8.4,2.8))
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plt.fill_between([0,a], [0,0], [L,L], color='#dddddd', alpha=0.5, step='pre', label='WG aperture (top)')
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for zc, xc in zip(z_centers, x_centers):
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plt.gca().add_patch(plt.Rectangle((xc - slot_w/2.0, zc - slot_L/2.0),
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slot_w, slot_L, fc='#3355ff', ec='k'))
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plt.xlim(-2, a+2); plt.ylim(-5, L+5)
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plt.gca().invert_yaxis()
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plt.xlabel('x (mm)'); plt.ylabel('z (mm)')
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plt.title('Top-view slot layout (y=b plane)')
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plt.grid(True); plt.legend()
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plt.show()
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