mirror of
https://github.com/NawfalMotii79/PLFM_RADAR.git
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sim(antenna): add 4x4 probe-fed array model — mutual coupling characterisation
Single-port-driven, 15-port-terminated FDTD sim built on the same v3 patch
design point (W=7.854, L=6.56, FEED_OFFSET=2.14) at the Gerber pitch
(14.27 mm X / 15.01 mm Y). Reads out S_jd for all elements when port
(DRIVEN_X, DRIVEN_Y) is excited. Configurable array size + driven port via
env vars; default = 4x4, drive inner element (1,1).
Result at PROFILE=balanced, drive (1,1):
Active S11 @ 10.5 GHz : -16.7 dB, Z = 45.7 + j13.5 Ω
Active -10 dB BW : 190 MHz (10.44-10.63 GHz; ≈ single-element 180)
Nearest-neighbour coupling:
-x edge neighbour (0,1): -18.3 dB (strongest — edge element loads less)
-y/+y in-array : -22 dB
+x interior neighbour : -24.7 dB
Diagonal : -32 dB
Far corners : -45 to -53 dB
Outputs: coupling_grid.png heatmap + S_matrix.csv (all S_jd full sweep) +
S11_data.csv (driven-port only).
Known limitation: port box must align with mesh lines; SmoothMeshLines may
sub-cell-shift seed lines, causing some DRIVEN_X/DRIVEN_Y choices to give
"Unused primitive" warning + zero excitation. Default (1,1) is verified;
other choices are best-effort. Documented inline.
This commit is contained in:
Jason
358
5_Simulations/Antenna/probe_fed_array_aeris10_v3.py
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358
5_Simulations/Antenna/probe_fed_array_aeris10_v3.py
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#!/usr/bin/env python3
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# probe_fed_array_aeris10_v3.py
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#
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# 4x4 (default; configurable) probe-fed patch array sim for AERIS-10. Built
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# on the same single-element design point as probe_fed_aeris10_v3.py but
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# placed on the 8x16 Gerber pitch (14.27 mm X / 15.01 mm Y).
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#
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# Purpose: characterise mutual coupling between elements. Each patch has its
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# own probe-via port; only one port is excited per sim run, the other 15 are
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# terminated in 50 Ω. From this we read:
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# - S_dd (active S11 of the driven element with array loaded)
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# - S_jd for all other ports j (coupling driven → j)
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# Pattern of |S_jd| dB values across the array tells us nearest-neighbour vs
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# diagonal vs skip-one coupling, edge vs interior asymmetry, etc.
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#
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# Per-element design (matches probe_fed_aeris10_v3.py iter#3):
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# PATCH_W = 7.854 mm PATCH_L = 6.56 mm FEED_OFFSET = 2.14 mm
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# Substrate: 0.508 mm RO4350B (εr=3.48, tanδ=0.0037)
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# Pitch: 14.27 mm × 15.01 mm (X-pitch ~λ₀/2 at 10.5 GHz, Y-pitch ~1.05·λ₀/2)
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#
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# Run:
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# cd /tmp && DYLD_LIBRARY_PATH=/Users/ganeshpanth/opt/openEMS/lib \
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# PROFILE=sanity \
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# /Users/ganeshpanth/radar_venv/bin/python \
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# /Users/ganeshpanth/PLFM_RADAR/5_Simulations/Antenna/probe_fed_array_aeris10_v3.py
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#
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# Env overrides:
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# ARRAY_NX ARRAY_NY (default 4, 4)
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# PITCH_X_MM PITCH_Y_MM (default 14.27, 15.01 from Gerber)
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# DRIVEN_X DRIVEN_Y (0-indexed; default = inner element 1,1)
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# PATCH_W_MM PATCH_L_MM FEED_OFFSET_MM (default v3 design point)
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#
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# Output (in /tmp/aeris10_array_v3/):
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# S_matrix.csv — driven-column S parameters (mag dB + phase deg) at 10.5 GHz
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# S11_data.csv — driven port full sweep
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# coupling_grid.png — heatmap of |S_jd| dB at 10.5 GHz across array
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import os
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import sys
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import time
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import csv
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import numpy as np
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import matplotlib
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matplotlib.use("Agg")
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import matplotlib.pyplot as plt
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from openEMS import openEMS
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from openEMS.physical_constants import C0
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from CSXCAD import ContinuousStructure
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from CSXCAD.SmoothMeshLines import SmoothMeshLines
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# ============================================================================
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# PROFILES
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# ============================================================================
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PROFILE = os.environ.get("PROFILE", "sanity")
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profiles = {
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"sanity": {"mesh_lambda_div": 18, "n_timesteps": 50000, "end_dB": -30},
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"balanced": {"mesh_lambda_div": 25, "n_timesteps": 80000, "end_dB": -40},
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}
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cfg = profiles[PROFILE]
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# ============================================================================
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# BAND
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# ============================================================================
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F0 = 10.5e9
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F_SPAN = 4.0e9
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F_START = F0 - F_SPAN/2
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F_STOP = F0 + F_SPAN/2
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# ============================================================================
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# STACKUP
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# ============================================================================
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T_CU = 0.035
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H_PATCH_SUB = 0.508
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EPS_RO4350B = 3.48
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TAN_RO4350B = 0.0037
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Z_GND = 0.0
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Z_PATCH = Z_GND + T_CU + H_PATCH_SUB
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Z_TOP = Z_PATCH + T_CU
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# ============================================================================
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# PATCH (per-element, from v3 iter#3)
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# ============================================================================
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PATCH_W = float(os.environ.get("PATCH_W_MM", "7.854"))
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PATCH_L = float(os.environ.get("PATCH_L_MM", "6.56"))
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FEED_OFFSET_MM = float(os.environ.get("FEED_OFFSET_MM", "2.14"))
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# ============================================================================
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# ARRAY
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# ============================================================================
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N_X = int(os.environ.get("ARRAY_NX", "4"))
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N_Y = int(os.environ.get("ARRAY_NY", "4"))
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PITCH_X = float(os.environ.get("PITCH_X_MM", "14.27"))
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PITCH_Y = float(os.environ.get("PITCH_Y_MM", "15.01"))
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DRIVEN_X = int(os.environ.get("DRIVEN_X", str(N_X // 2 - (N_X+1) % 2))) # inner element
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DRIVEN_Y = int(os.environ.get("DRIVEN_Y", str(N_Y // 2 - (N_Y+1) % 2)))
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# Array footprint extent (centre patch on origin)
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ARRAY_X_HALF = (N_X-1)/2 * PITCH_X + PATCH_W/2
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ARRAY_Y_HALF = (N_Y-1)/2 * PITCH_Y + PATCH_L/2
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# Substrate / ground extents (~λ/2 margin around array)
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GND_MARGIN = 14.3
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GND_X_HALF = ARRAY_X_HALF + GND_MARGIN
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GND_Y_HALF = ARRAY_Y_HALF + GND_MARGIN
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# Air box
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AIR_ABOVE = 14.3
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AIR_BELOW = 14.3
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AIR_X_HALF = GND_X_HALF + 8.0
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AIR_Y_HALF = GND_Y_HALF + 8.0
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OUT_DIR = "/tmp/aeris10_array_v3"
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os.makedirs(OUT_DIR, exist_ok=True)
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def patch_center(i, j):
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"""Centre coordinate of patch at array index (i,j), origin at array centre."""
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x = -(N_X-1)/2 * PITCH_X + i * PITCH_X
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y = -(N_Y-1)/2 * PITCH_Y + j * PITCH_Y
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return x, y
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# ============================================================================
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# Build + run
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# ============================================================================
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def run_case(sim_path, profile_cfg):
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fdtd = openEMS(NrTS=profile_cfg["n_timesteps"],
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EndCriteria=10**(profile_cfg["end_dB"]/20.0))
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fdtd.SetGaussExcite(F0, F_SPAN/2.0)
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fdtd.SetBoundaryCond(["MUR"]*6)
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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(1e-3)
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# ---- materials ----
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eps0 = 8.854e-12
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patch_sub = CSX.AddMaterial("RO4350B",
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epsilon=EPS_RO4350B,
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kappa=2*np.pi*F0*EPS_RO4350B*eps0*TAN_RO4350B)
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copper = CSX.AddMetal("Copper")
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# ---- substrate (full board extent) ----
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patch_sub.AddBox([-GND_X_HALF, -GND_Y_HALF, Z_GND + T_CU],
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[+GND_X_HALF, +GND_Y_HALF, Z_PATCH], priority=1)
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# ---- L2: full ground plane ----
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copper.AddBox([-GND_X_HALF, -GND_Y_HALF, Z_GND],
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[+GND_X_HALF, +GND_Y_HALF, Z_GND + T_CU], priority=10)
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# ---- L1: 4x4 patch array + ports ----
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ports = []
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feed_locs = []
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for i in range(N_X):
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for j in range(N_Y):
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cx, cy = patch_center(i, j)
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copper.AddBox([cx - PATCH_W/2, cy - PATCH_L/2, Z_PATCH],
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[cx + PATCH_W/2, cy + PATCH_L/2, Z_PATCH + T_CU],
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priority=10)
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feed_x = cx
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feed_y = cy - PATCH_L/2 + FEED_OFFSET_MM
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feed_locs.append((feed_x, feed_y, i, j))
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# ---- mesh ----
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lambda_min_mm = (C0 / F_STOP) * 1000.0
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res = lambda_min_mm / profile_cfg["mesh_lambda_div"]
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# X mesh: array extent + air, plus patch edges + feed locations
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xlines = [-AIR_X_HALF, -GND_X_HALF, +GND_X_HALF, +AIR_X_HALF]
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for i in range(N_X):
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cx, _ = patch_center(i, 0)
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xlines += [cx - PATCH_W/2, cx, cx + PATCH_W/2]
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# Y mesh
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ylines = [-AIR_Y_HALF, -GND_Y_HALF, +GND_Y_HALF, +AIR_Y_HALF]
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for j in range(N_Y):
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_, cy = patch_center(0, j)
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ylines += [cy - PATCH_L/2, cy, cy + PATCH_L/2,
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cy - PATCH_L/2 + FEED_OFFSET_MM] # feed y location
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# Z mesh: 6 cells in substrate
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air_below = list(np.arange(Z_GND - T_CU - AIR_BELOW, Z_GND - T_CU, res))
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air_above = list(np.arange(Z_TOP + res, Z_TOP + AIR_ABOVE + res, res))
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sub_interior = list(np.linspace(Z_GND + T_CU, Z_PATCH, 7)[1:-1])
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zlines = sorted(set(air_below + [
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Z_GND - T_CU, Z_GND, Z_GND + T_CU,
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Z_PATCH, Z_PATCH + T_CU,
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] + sub_interior + air_above))
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xlines = SmoothMeshLines(np.array(xlines), res)
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ylines = SmoothMeshLines(np.array(ylines), res)
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zlines = np.array(zlines)
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mesh.AddLine("x", xlines)
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mesh.AddLine("y", ylines)
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mesh.AddLine("z", zlines)
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n_cells = len(xlines) * len(ylines) * len(zlines)
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# ---- ports (one excited, 15 terminated 50Ω) ----
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# NOTE: each port box must land exactly on existing mesh lines. The seed
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# mesh includes feed_x (= patch centre cx) and feed_y for each (i,j) — so
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# this normally works — but SmoothMeshLines can sub-cell-shift seed lines
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# in some configurations and a port box ends up between two mesh lines,
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# leaving openEMS without an excitation cell ("Unused primitive" warning,
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# zero energy). The DRIVEN=(1,1) inner-element case has been verified to
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# land on the mesh; other driven-port choices are best-effort. If you see
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# NaN/zero results for a different DRIVEN_X/DRIVEN_Y, that's the cause.
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for (feed_x, feed_y, i, j) in feed_locs:
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port_num = i * N_Y + j + 1
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excite_amp = 1.0 if (i == DRIVEN_X and j == DRIVEN_Y) else 0.0
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port = fdtd.AddLumpedPort(port_num, 50,
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[feed_x, feed_y, Z_GND + T_CU],
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[feed_x, feed_y, Z_PATCH],
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'z', excite=excite_amp, priority=5)
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ports.append(((i, j), port))
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# ---- run ----
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print(f"[case] {N_X}x{N_Y} array, driven=({DRIVEN_X},{DRIVEN_Y}), "
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f"cells={n_cells:,}, sub={H_PATCH_SUB}mm, pitch={PITCH_X}x{PITCH_Y}mm")
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t0 = time.time()
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fdtd.Run(sim_path, verbose=0, cleanup=True)
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dt = time.time() - t0
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# ---- post-process ----
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freq = np.linspace(F_START, F_STOP, 401)
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driven_port = next(p for (idx, p) in ports if idx == (DRIVEN_X, DRIVEN_Y))
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for (idx, p) in ports:
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p.CalcPort(sim_path, freq)
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# S_jd (j is each port, d is driven). For driven port, S_dd = uf_ref/uf_inc.
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# For other ports, S_jd = uf_ref_j / uf_inc_d (no incident wave at j from
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# its own source since port j is unexcited).
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S = {}
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for (idx, p) in ports:
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if idx == (DRIVEN_X, DRIVEN_Y):
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S[idx] = p.uf_ref / p.uf_inc
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else:
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S[idx] = p.uf_ref / driven_port.uf_inc
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return freq, S, dt, ports
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# ============================================================================
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# MAIN
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# ============================================================================
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sim_path = os.path.join(OUT_DIR, "single")
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freq, S, dt, ports = run_case(sim_path, cfg)
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# At 10.5 GHz
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i_op = int(np.argmin(np.abs(freq - F0)))
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# Print coupling grid
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print()
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print("=" * 70)
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print(f" 4x4 probe-fed array — driven port at ({DRIVEN_X},{DRIVEN_Y})")
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print(f" Substrate: {H_PATCH_SUB} mm RO4350B, pitch {PITCH_X}x{PITCH_Y} mm")
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print(f" Sim time: {dt:.1f} s")
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print("=" * 70)
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print()
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print(f" S parameters at {F0/1e9:.2f} GHz (|S_j,driven| in dB):")
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print()
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# Layout grid as visual array (i is x-direction, j is y-direction)
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# Print y high to low so it matches usual visual orientation
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header = " " + "".join(f" i={i:1d} " for i in range(N_X))
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print(header)
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for j in reversed(range(N_Y)):
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row = f" j={j:1d}: "
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for i in range(N_X):
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val = abs(S[(i, j)][i_op])
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dB = 20*np.log10(val + 1e-30)
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row += f"{dB:>7.1f}"
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print(row)
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print()
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# Driven port S11 vs frequency
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S_dd = S[(DRIVEN_X, DRIVEN_Y)]
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S_dd_dB = 20*np.log10(np.abs(S_dd) + 1e-30)
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zin_d = 50.0 * (1 + S_dd) / (1 - S_dd) # Z = Z0·(1+S)/(1-S)
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print(f" Driven port active S11:")
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print(f" @ 10.5 GHz : {S_dd_dB[i_op]:.2f} dB Z = {zin_d[i_op].real:.1f} + j{zin_d[i_op].imag:.1f} Ω")
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# -10 dB BW around f0
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below = S_dd_dB <= -10.0
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if below[i_op]:
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lo, hi = i_op, i_op
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while lo > 0 and below[lo-1]:
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lo -= 1
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while hi < len(below)-1 and below[hi+1]:
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hi += 1
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print(f" -10 dB BW : {(freq[hi]-freq[lo])/1e6:.0f} MHz "
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f"({freq[lo]/1e9:.2f} – {freq[hi]/1e9:.2f} GHz)")
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else:
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print(f" -10 dB BW : <none at 10.5 GHz>")
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# Worst-case coupling (excluding driven port itself)
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couplings = [(idx, abs(S[idx][i_op])) for idx in S.keys() if idx != (DRIVEN_X, DRIVEN_Y)]
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couplings.sort(key=lambda x: -x[1])
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print()
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print(f" Top-5 strongest couplings to driven port at 10.5 GHz:")
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for idx, val in couplings[:5]:
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di = idx[0] - DRIVEN_X
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dj = idx[1] - DRIVEN_Y
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dB = 20*np.log10(val + 1e-30)
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print(f" ({idx[0]},{idx[1]}) Δ=({di:+d},{dj:+d}) |S| = {dB:>6.1f} dB")
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print("=" * 70)
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# Save S matrix CSV (full-band)
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with open(os.path.join(OUT_DIR, "S_matrix.csv"), "w", newline="") as f:
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w = csv.writer(f)
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header = ["freq_Hz"]
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keys = sorted(S.keys())
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for idx in keys:
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header += [f"S({idx[0]},{idx[1]})_dB", f"S({idx[0]},{idx[1]})_phase_deg"]
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w.writerow(header)
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for k in range(len(freq)):
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row = [freq[k]]
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for idx in keys:
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mag_dB = 20*np.log10(np.abs(S[idx][k]) + 1e-30)
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phase = np.angle(S[idx][k], deg=True)
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row += [mag_dB, phase]
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w.writerow(row)
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# Save driven-port S11 CSV
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with open(os.path.join(OUT_DIR, "S11_data.csv"), "w", newline="") as f:
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w = csv.writer(f)
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w.writerow(["freq_Hz", "S11_dB", "Zin_real", "Zin_imag"])
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for k in range(len(freq)):
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w.writerow([freq[k], S_dd_dB[k], zin_d[k].real, zin_d[k].imag])
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# Coupling heatmap at 10.5 GHz
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fig, ax = plt.subplots(figsize=(6.5, 6))
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grid = np.zeros((N_Y, N_X))
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for (i, j) in S.keys():
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grid[j, i] = 20*np.log10(abs(S[(i,j)][i_op]) + 1e-30)
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# Driven port floor (S11 is just one number, not a coupling) — set to NaN to highlight
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grid[DRIVEN_Y, DRIVEN_X] = np.nan
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im = ax.imshow(grid, origin='lower', cmap='viridis', aspect='equal')
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ax.set_xticks(range(N_X))
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ax.set_yticks(range(N_Y))
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ax.set_xlabel('i (x-pitch direction)')
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ax.set_ylabel('j (y-pitch direction)')
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ax.set_title(f'AERIS-10 4x4 array — coupling |S_j,({DRIVEN_X},{DRIVEN_Y})| at {F0/1e9:.2f} GHz')
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# Annotate cells
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for j in range(N_Y):
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for i in range(N_X):
|
||||
if (i, j) == (DRIVEN_X, DRIVEN_Y):
|
||||
ax.text(i, j, "DRIVEN", ha='center', va='center', color='red',
|
||||
fontsize=9, fontweight='bold')
|
||||
else:
|
||||
ax.text(i, j, f"{grid[j,i]:.1f}\ndB", ha='center', va='center',
|
||||
color='white', fontsize=8)
|
||||
plt.colorbar(im, ax=ax, label='|S| (dB)', shrink=0.7)
|
||||
fig.tight_layout()
|
||||
fig.savefig(os.path.join(OUT_DIR, "coupling_grid.png"), dpi=140)
|
||||
plt.close(fig)
|
||||
|
||||
print(f"[out] {OUT_DIR}/coupling_grid.png")
|
||||
print(f"[out] {OUT_DIR}/S_matrix.csv")
|
||||
print(f"[out] {OUT_DIR}/S11_data.csv")
|
||||
Reference in New Issue
Block a user