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PLFM_RADAR/5_Simulations/Antenna/openems_quartz_slotted_wg_10p5GHz.py
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2026-04-12 14:21:03 +05:45

330 lines
10 KiB
Python

# openems_quartz_slotted_wg_10p5GHz.py
# Slotted rectangular waveguide (quartz-filled, εr=3.8) tuned to 10.5 GHz.
# Builds geometry, meshes (no GetLine calls), sweeps S-params/impedance over 9.5-11.5 GHz,
# computes 3D far-field, and reports estimated max realized gain.
import os
import tempfile
import numpy as np
import matplotlib.pyplot as plt
import time
# --- openEMS / CSXCAD bindings ---
from openEMS import openEMS
from openEMS.physical_constants import C0
try:
from CSXCAD import ContinuousStructure, AppCSXCAD_BIN
HAVE_APP = True
except ImportError:
from CSXCAD import ContinuousStructure
AppCSXCAD_BIN = None
HAVE_APP = False
#Set PROFILE to "sanity" first; run and check [mesh] cells: stays reasonable.
#If it's small, move to "balanced"; once happy, go "full".
#Toggle VIEW_GEOM=True if you want the 3D viewer (requires AppCSXCAD_BIN available).
# =========================
# USER SETTINGS / PROFILES
# =========================
PROFILE = "sanity" # choose: "sanity" | "balanced" | "full"
VIEW_GEOM = False # True => launch AppCSXCAD viewer (if available)
SIMULATE = True # False => skip FDTD (for quick post-proc dev)
THREADS = 0 # 0 => all cores
# --- profiles tuned for i5-1135G7 + 16 GB ---
profiles = {
"sanity": {
"Nslots": 12, "mesh_res": 0.8,
"air_x": 6.0, "air_y": 20.0, "air_z": 10.0,
"n_theta": 61, "n_phi": 121, "freq_pts": 201, "pml": 6
},
"balanced": {
"Nslots": 24, "mesh_res": 0.6,
"air_x": 8.0, "air_y": 30.0, "air_z": 12.0,
"n_theta": 91, "n_phi": 181, "freq_pts": 301, "pml": 8
},
"full": {
"Nslots": 32, "mesh_res": 0.5,
"air_x": 10.0, "air_y": 40.0, "air_z": 15.0,
"n_theta": 91, "n_phi": 181, "freq_pts": 401, "pml": 8
}
}
cfg = profiles[PROFILE]
# =====================
# BAND & WAVEGUIDE SPEC
# =====================
f0 = 10.5e9
f_span = 2.0e9
f_start, f_stop = f0 - f_span/2, f0 + f_span/2
er_quartz = 3.8 # fused silica/quartz
# Array constraint (λ0/2 pitch, 1 mm septum) => internal a ~ 13.28 mm
lambda0_mm = (C0/f0) * 1e3
a = 13.28 # mm (broad wall, internal)
b = 6.50 # mm (narrow wall, internal) <-- comfortable machining
# Slot starters (tune later for taper)
slot_w = 0.60 # mm across x
# --- guide wavelength at 10.5 GHz (TE10) ---
fc10 = (C0/(2.0*np.sqrt(er_quartz))) * (1.0/(a*1e-3)) # Hz
lambda_d = (C0/f0) / np.sqrt(er_quartz) # m
lambda_g = lambda_d / np.sqrt(1.0 - (fc10/f0)**2) # m
lambda_g_mm = lambda_g * 1e3
# --- slots geometry (from λg) ---
slot_s = 0.5*lambda_g_mm
slot_L = 0.47*lambda_g_mm
margin = 0.25*lambda_g_mm
# ===================================
# FDTD / CSX / MESH (explicit lines)
# ===================================
unit_mm = 1e-3
Sim_Path = os.path.join(tempfile.gettempdir(), f'openems_quartz_slotted_wg_{PROFILE}')
FDTD = openEMS(NrTS=int(6e5), EndCriteria=1e-5)
FDTD.SetGaussExcite(0.5*(f_start+f_stop), 0.5*(f_stop-f_start))
FDTD.SetBoundaryCond([f'PML_{cfg["pml"]}']*6)
FDTD.SetOverSampling(4)
FDTD.SetTimeStepFactor(0.95)
CSX = ContinuousStructure()
FDTD.SetCSX(CSX)
mesh = CSX.GetGrid()
mesh.SetDeltaUnit(unit_mm)
# Pads & extent
t_metal = 0.8 # mm metal wall thickness
air_x = cfg["air_x"]
air_y = cfg["air_y"]
air_z = cfg["air_z"]
mesh_res = cfg["mesh_res"]
# Length from Nslots
Nslots = cfg["Nslots"]
guide_length_mm = margin + (Nslots-1)*slot_s + margin
# Simulation extents (mm)
x_min, x_max = -air_x, a + air_x
y_min, y_max = -5.0, b + t_metal + air_y
z_min, z_max = -air_z, guide_length_mm + air_z
# Slot centers and edges (mm)
z_centers = margin + np.arange(Nslots)*slot_s
delta0 = 0.90 # mm offset from centerline (± alternated)
x_centers = (a/2.0) + np.array([+delta0 if i%2==0 else -delta0 for i in range(Nslots)])
x_edges = np.concatenate([x_centers - slot_w/2.0, x_centers + slot_w/2.0])
z_edges = np.concatenate([z_centers - slot_L/2.0, z_centers + slot_L/2.0])
# Mesh lines: explicit (NO GetLine calls)
x_lines = sorted({x_min, -t_metal, 0.0, a, a + t_metal, x_max, *list(x_edges)})
y_lines = [y_min, 0.0, b, b+t_metal, y_max]
z_lines = sorted({z_min, 0.0, guide_length_mm, z_max, *list(z_edges)})
mesh.AddLine('x', x_lines)
mesh.AddLine('y', y_lines)
mesh.AddLine('z', z_lines)
# Print complexity and rough memory (to help stay inside 16 GB)
Nx, Ny, Nz = len(x_lines)-1, len(y_lines)-1, len(z_lines)-1
Ncells = Nx*Ny*Nz
mem_fields_bytes = Ncells * 6 * 8 # rough ~ (Ex,Ey,Ez,Hx,Hy,Hz) doubles
dx_min = min(np.diff(x_lines))
dy_min = min(np.diff(y_lines))
dz_min = min(np.diff(z_lines))
# Optional smoothing to limit max cell size
mesh.SmoothMeshLines('all', mesh_res, ratio=1.4)
# =================
# MATERIALS & SOLIDS
# =================
pec = CSX.AddMetal('PEC')
quartzM = CSX.AddMaterial('QUARTZ')
quartzM.SetMaterialProperty(epsilon=er_quartz)
airM = CSX.AddMaterial('AIR')
# Quartz full block
quartzM.AddBox([0, 0, 0], [a, b, guide_length_mm])
# PEC tube walls
pec.AddBox([-t_metal, 0, 0], [0, b, guide_length_mm]) # left
pec.AddBox([a, 0, 0], [a+t_metal,b, guide_length_mm]) # right
pec.AddBox([-t_metal,-t_metal,0],[a+t_metal,0, guide_length_mm]) # bottom
pec.AddBox(
[-t_metal, b, 0], [a + t_metal, b + t_metal, guide_length_mm]
) # top (slots will pierce)
# Slots (AIR) overriding top metal
for zc, xc in zip(z_centers, x_centers, strict=False):
x1, x2 = xc - slot_w/2.0, xc + slot_w/2.0
z1, z2 = zc - slot_L/2.0, zc + slot_L/2.0
prim = airM.AddBox([x1, b, z1], [x2, b+t_metal, z2])
prim.SetPriority(10) # ensure cut
# =========
# WG PORTS
# =========
port_thick = max(4*mesh_res, 2.0) # mm
p1_start = [0, 0, max(0.5, 10*mesh_res)]
p1_stop = [a, b, p1_start[2] + port_thick]
FDTD.AddRectWaveGuidePort(port_nr=1, start=p1_start, stop=p1_stop,
p_dir='z', a=a*unit_mm, b=b*unit_mm, mode_name='TE10', excite=1)
p2_stop = [a, b, guide_length_mm - max(0.5, 10*mesh_res)]
p2_start = [0, 0, p2_stop[2] - port_thick]
FDTD.AddRectWaveGuidePort(port_nr=2, start=p2_start, stop=p2_stop,
p_dir='z', a=a*unit_mm, b=b*unit_mm, mode_name='TE10', excite=0)
# =========
# NF2FF BOX
# =========
def create_nf2ff(FDTD_obj, name, start, stop, frequency):
try:
return FDTD_obj.CreateNF2FFBox(name=name, start=start, stop=stop, frequency=frequency)
except AttributeError:
return FDTD_obj.AddNF2FFBox(name=name, start=start, stop=stop, frequency=frequency)
nf2ff = create_nf2ff(
FDTD,
name='nf2ff',
start=[x_min+1.0, y_min+1.0, z_min+1.0],
stop =[x_max-1.0, y_max-1.0, z_max-1.0],
frequency=[f0]
)
# ==========
# VIEW GEOM
# ==========
if VIEW_GEOM and HAVE_APP and AppCSXCAD_BIN:
os.makedirs(Sim_Path, exist_ok=True)
csx_xml = os.path.join(Sim_Path, f'quartz_slotted_wg_{PROFILE}.xml')
CSX.Write2XML(csx_xml)
os.system(f'"{AppCSXCAD_BIN}" "{csx_xml}"')
# ... right before the FDTD run:
t0 = time.time()
FDTD.Run(Sim_Path, cleanup=True, verbose=2, numThreads=THREADS)
t1 = time.time()
# ... right before NF2FF (far-field):
t2 = time.time()
try:
res = nf2ff.CalcNF2FF(Sim_Path, [f0], theta, phi) # noqa: F821
except AttributeError:
res = FDTD.CalcNF2FF(nf2ff, Sim_Path, [f0], theta, phi) # noqa: F821
t3 = time.time()
# ... S-parameters postproc timing (optional):
t4 = time.time()
for p in ports: # noqa: F821
p.CalcPort(Sim_Path, freq) # noqa: F821
t5 = time.time()
# =======
# RUN FDTD
# =======
if SIMULATE:
FDTD.Run(Sim_Path, cleanup=True, verbose=2, numThreads=THREADS)
freq = np.linspace(f_start, f_stop, profiles[PROFILE]["freq_pts"])
ports = list(FDTD.ports) # Port 1 & 2 in creation order
for p in ports:
p.CalcPort(Sim_Path, freq)
S11 = ports[0].uf_ref / ports[0].uf_inc
S21 = ports[1].uf_ref / ports[0].uf_inc
Zin = ports[0].uf_tot / ports[0].if_tot
plt.figure(figsize=(7.6,4.6))
plt.plot(freq*1e-9, 20*np.log10(np.abs(S11)), lw=2, label='|S11|')
plt.plot(freq*1e-9, 20*np.log10(np.abs(S21)), lw=2, ls='--', label='|S21|')
plt.grid(True)
plt.legend()
plt.xlabel('Frequency (GHz)')
plt.ylabel('Magnitude (dB)')
plt.title(f'S-Parameters (profile: {PROFILE})')
plt.figure(figsize=(7.6,4.6))
plt.plot(freq*1e-9, np.real(Zin), lw=2, label='Re{Zin}')
plt.plot(freq*1e-9, np.imag(Zin), lw=2, ls='--', label='Im{Zin}')
plt.grid(True)
plt.legend()
plt.xlabel('Frequency (GHz)')
plt.ylabel('Ohms')
plt.title('Input Impedance (Port 1)')
# ==========================
# POST: 3D FAR-FIELD / GAIN
# ==========================
n_theta, n_phi = cfg["n_theta"], cfg["n_phi"]
theta = np.linspace(0, np.pi, n_theta)
phi = np.linspace(0, 2*np.pi, n_phi)
try:
res = nf2ff.CalcNF2FF(Sim_Path, [f0], theta, phi)
except AttributeError:
res = FDTD.CalcNF2FF(nf2ff, Sim_Path, [f0], theta, phi)
idx_f0 = np.argmin(np.abs(freq - f0))
Dmax_lin = float(res.Dmax[0])
mismatch = 1.0 - np.abs(S11[idx_f0])**2
Gmax_lin = Dmax_lin * float(mismatch)
Gmax_dBi = 10*np.log10(Gmax_lin)
# Normalized 3D pattern
E = np.squeeze(res.E_norm) # [th, ph]
E = E / np.max(E)
TH, PH = np.meshgrid(theta, phi, indexing='ij')
R = E
X = R * np.sin(TH) * np.cos(PH)
Y = R * np.sin(TH) * np.sin(PH)
Z = R * np.cos(TH)
fig = plt.figure(figsize=(7.2,6.2))
ax = fig.add_subplot(111, projection='3d')
ax.plot_surface(X, Y, Z, rstride=2, cstride=2, linewidth=0, antialiased=True, alpha=0.92)
ax.set_title(f'Normalized 3D Pattern @ {f0/1e9:.2f} GHz\n(peak ≈ {Gmax_dBi:.1f} dBi)')
ax.set_box_aspect((1,1,1))
ax.set_xlabel('x')
ax.set_ylabel('y')
ax.set_zlabel('z')
plt.tight_layout()
# ==========================
# QUICK 2D GEOMETRY PREVIEW
# ==========================
plt.figure(figsize=(8.4,2.8))
plt.fill_between(
[0, a],
[0, 0],
[guide_length_mm, guide_length_mm],
color='#dddddd',
alpha=0.5,
step='pre',
label='WG top aperture',
)
for zc, xc in zip(z_centers, x_centers, strict=False):
plt.gca().add_patch(plt.Rectangle((xc - slot_w/2.0, zc - slot_L/2.0),
slot_w, slot_L, fc='#3355ff', ec='k'))
plt.xlim(-2, a + 2)
plt.ylim(-5, guide_length_mm + 5)
plt.gca().invert_yaxis()
plt.xlabel('x (mm)')
plt.ylabel('z (mm)')
plt.title(f'Top-view slot layout (N={Nslots}, profile={PROFILE})')
plt.grid(True)
plt.legend()
plt.show()