Audit of how the ADAR1000 is actually steered in production. Reproduces
main.cpp:initializeBeamMatrices() (PHASE_DIFFERENCES, matrix1, matrix2,
vector_0) verbatim in Python and runs the patterns through the same array-
factor pipeline used for the firmware-vs-correct comparison.
Key findings — context for fixing the setBeamAngle() bug without regression:
1) setBeamAngle() is DEAD CODE in production. grep for callers across the
whole tree returns only the definition itself (ADAR1000_Manager.cpp:215),
the header declaration (line 58), and one comment in ADAR1000_AGC.cpp
referencing the sign convention. main.cpp does NOT call it. The 4-phase
broadcast bug exposed in commit 2f4d45c is therefore latent, not active.
Fixing setBeamAngle() has zero risk of changing production behaviour.
2) Production path: initializeBeamMatrices() (main.cpp:467) computes
matrix1[bp][el] = degTo7Bit(el * phase_differences[bp]) for all 16
elements properly (no 4-broadcast). main.cpp's runRadarPulseSequence()
then calls setCustomBeamPattern16(matrix1[bp], TX/RX) → 16-element
progressive phase reaches the chips correctly. This part is right.
3) HOWEVER — the production tables themselves have separate concerns:
a) SIGN CONVENTION MISLABEL: comment says "matrix1 = positive steering
angles" but math+sim show positive phase_diff steers to NEGATIVE θ.
matrix1[bp=0] (phase_diff=+160°) → actual peak -62°.
Either the comment is wrong, or hardware wiring inverts what's
labeled "+elevation" — needs a hardware test to confirm.
b) ASYMMETRIC INDEXING: matrix2 uses phase_differences[bp + 16] which
gives matrix2[bp=0]=-3.4° while matrix1[bp=0]=-62°. So as bp goes
0→14, matrix1 zooms in toward broadside (-62°→-4°) while matrix2
zooms out (+4°→+62°) — they're NOT mirror images. Symmetric mirror
would be phase_differences[30 - bp].
c) NON-UNIFORM COVERAGE: phase_differences[] follows 160/n pattern
(160, 80, 53.33, 40, 32, ...). After sin⁻¹ this gives 17 unique
scan angles spanning -62°..+62° with a 36° GAP between -62° and
-26°, but 2° spacing near broadside. May be intentional (oversample
near nominal target line) but flag for confirmation.
d) WORST-CASE SLL at extreme scan (matrix1[0] → -62°): only -2.9 dB.
Main beam barely clears sidelobes — typical at near-grazing scan
due to embedded element pattern roll-off.
e) initializeBeamMatricesWithSteeringAngles() (main.cpp:1611) is also
dead code. It computes the same thing two different ways. Safe to
remove or merge during cleanup.
Recommendation for fix sequence (low → high risk):
i. Fix setBeamAngle() to call setCustomBeamPattern16() with proper
16-element table (or mark deprecated). Zero production risk.
ii. Add unit test that runs setBeamAngle and verifies the resulting
phase codes match a known-good 16-element progression.
iii. Update the misleading comments in initializeBeamMatrices() to say
what the matrices ACTUALLY do (the sign convention).
iv. Hardware test BEFORE touching matrix2 indexing or phase_differences
distribution — these may be deliberately tuned to platform mounting.
PART 1 — edge_fed_row_nf2ff_aeris10_v3.py:
Far-field analysis of the 1x8 series-fed row at 10.520 GHz to discriminate
broadside from scanned operation. Adds an nf2ff probe box to the verified
TX-centered design point (CONN_LEN=8.15) and computes the radiation pattern.
Result: E-plane (along array y) main lobe at θ=0.0°, BW3dB=14°
H-plane (perpendicular) main lobe at θ=0.0°, BW3dB=44°
First sidelobe -12 dB at ±18° (theoretical N=8 uniform: -13 dB)
→ BROADSIDE CONFIRMED at the operating mode.
openEMS NF2FF API notes baked into the script:
- CalcNF2FF expects theta/phi in DEGREES, converts internally.
- Prad/Dmax are sign-buggy in this version; pattern shape (E_norm) is
what we use for broadside identification.
- EndCriteria is 10·log10 energy ratio (so -40 dB → EndCriteria=1e-4).
PART 2 — array_factor_adar1000_aeris10.py:
Phased-array beam-forming verification using the ADAR1000 firmware's actual
phase-shifter codes. Combines the cached single-row embedded-element pattern
with a 16-element x-axis array factor at d=λ/2=14.286 mm pitch (matches
firmware's `element_spacing = wavelength/2` constant).
Replicates ADAR1000_Manager.cpp:714-729 (calculatePhaseSettings) and the
setBeamAngle() loop that broadcasts the 4-phase pattern to all 4 chips.
Compares against the correct 16-element progressive phasing.
CRITICAL FIRMWARE BUG SURFACED BY THE SIM:
setBeamAngle(angle) computes only 4 phases (one per chip channel), then
applies the same 4-phase pattern to all 4 chips. The intended 16-element
beam-steering never actually happens.
At cmd 15°, the firmware writes: [0, 17, 33, 50] × 4 = repeating pattern
Correct 16-elem progression: [0, 17, 33, 50, 66, 83, 99, 116, 5, 21,
38, 54, 71, 87, 104, 120]
Sim consequences (H-plane peak vs commanded):
cmd +0° → fw peaks +0° (correct) / correct +0°
cmd +5° → fw peaks +0° (NO STEERING) / correct -4°
cmd +10° → fw peaks +0° (NO STEERING) / correct -10°
cmd +15° → fw peaks +0° (NO STEERING) / correct -14°
cmd +20° → fw peaks -28° (locked grating) / correct -20°
cmd +30° → fw peaks -30° (coincidence) / correct -30°
cmd +45° → fw peaks -30° (locked) / correct -44°
Why: the same 4-elem pattern broadcast to 4 chips = effective super-pitch
d_super = 4d = 2λ, which generates grating lobes at sin(θ_g)=±0.5±sin(θ_0).
For |cmd|<18° those grating lobes coincide with the fixed broadside peak,
so the array radiates broadside regardless of commanded angle. For larger
commands the beam jumps to ±30° (the grating-lobe direction), not the
intended target.
The proper function setCustomBeamPattern16() (ADAR1000_Manager.cpp:636)
exists but isn't called by setBeamAngle(); fix is to either route through
it from a host-computed 16-element table, or extend calculatePhaseSettings
to produce 16 phases. Tracking under a separate beam-forming PR (not
antenna sim).
Other radar-engineer checks (all PASS for the antenna with proper phasing):
- Phase quantization: 7-bit (2.8125°/LSB) adds <0.2 dB SLL degradation
- Grating lobes: d=λ/2 → none in real space at any scan angle 0..90°
- Scan loss: matches cos(θ) ideal up to ~45°, then EEP roll-off dominates
- Beam pointing: sign-flipped cmd↔peak (cmd +X° peaks at -X°) — wiring
convention; either negate phase_shift in firmware or invert in host
- Null steering: phase-only synthesis places -30 dB null at θ=20° while
keeping main beam at broadside — confirmed feasible
Sweep CONN_LEN at PROFILE=balanced to land the operating-mode dip on the
chirp-band center instead of 60 MHz above it. Sensitivity is df/dCONN ≈
-0.20 GHz/mm (longer line → lower op freq).
CONN=8.00 → dip 10.560 GHz, S11@10.520 = -12.6 dB (above TX)
CONN=8.15 → dip 10.520 GHz, S11@10.520 = -18.8 dB (TX-centered)
CONN=8.20 → dip 10.510 GHz, S11@10.510 = -18.4 dB (TX low edge)
CONN=8.25 → dip 10.500 GHz, S11@10.500 = -18.4 dB (LO-centered)
CONN_LEN=8.15 wins because the radar TX 10.510-10.530 GHz sees -17 to -19 dB
symmetrically across the band, with -15 dB margin at the LO frequency. -10 dB
BW spans 10.470-10.580 GHz (110 MHz). Pitch 15.10 mm vs old Gerber 15.01 mm.
Daisy-chain validation for 2-layer 0.508 mm RO4350B stackup. Row of 8 patches
edge-connected via 8.0 mm microstrip segments (pitch 14.95 mm matches old
Gerber). With direct edge feed on patch 0 (no inset; inset would drop the row
input Z to ~6 Ω), the natural input impedance at the operating mode is ~80 Ω,
close enough to 50 Ω for direct match without a quarter-wave transformer.
Topology behaves as a finite periodic resonator with N=8 modes (~0.5 GHz
spacing) and a stopband centered on the patch self-resonance. Operating point
is the top-below-stopband mode at 10.56 GHz: S11 = -22.5 dB, Zin = 79.9 - j3 Ω.
-10 dB BW spans 10.51-10.61 GHz (100 MHz), covering the 10.510-10.530 GHz
chirp band with S11 = -10.4 to -14.6 dB across that interval.
Mesh sensitivity: sanity profile (lambda/18) gave a misleading deepest-dip at
11.4 GHz; balanced (lambda/25) is required to land the operating-mode
characterization correctly. PROFILE=balanced is now the documented run mode.
Validates the "Option C" hardware path: keep the old 8x16 Gerber's series-fed
edge-fed topology, just thicken the patch substrate from 0.102 mm to 0.508 mm
RO4350B. Single-element edge-fed with inset notch matched to 50 Ω microstrip.
Verified at PROFILE=balanced (λ/25 mesh):
W = 7.854 mm (preserved from old Gerber → array compatible)
L = 6.95 mm (tuned for f_res = 10.5 GHz on 0.508 mm sub)
inset_depth = 3.40 mm (~49 % of L)
inset_gap = 0.30 mm (each side of feed line, in the inset notch)
feed_W = 1.16 mm (50 Ω microstrip on 0.508 mm RO4350B)
feed_lead = 15.5 mm (= 1·λ_g at 10.5 GHz → port sees true antenna Z)
Result:
f_res = 10.509 GHz, S11 @ 10.5 = -18.5 dB, VSWR = 1.27
Z @ 10.5 = 61.8 + j3.2 Ω
-10 dB BW = 180 MHz (10.41-10.59 GHz, 1.71 %)
This is identical BW to probe_fed_v3 — confirming BW is set by substrate
thickness alone, not feed method. Edge-fed Option C is therefore the simpler
2-layer hardware path: same series-fed-row architecture as the old Gerber,
single PCB stackup, no probe vias / antipads / back-board splitter complexity.
Next step: extend to a 1x8 series-fed row to verify the daisy-chain topology
still gives in-phase feeding at the new substrate's λ_g.
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.
Single-element OpenEMS sim for a 2-layer probe-fed patch on 0.508 mm RO4350B.
Verified at PROFILE=balanced (λ/25 mesh): f_res = 10.51 GHz, S11 = -21.8 dB,
VSWR 1.18, -10 dB BW = 180 MHz (10.40-10.58 GHz). Direct 50 Ω match — no port
matching cap needed.
Design point baked into defaults:
PATCH_W = 7.854 mm (preserved from old 8x16 Gerber → array compatible)
PATCH_L = 6.56 mm (tuned for f_res = 10.5 GHz at 0.508 mm sub)
FEED_OFFSET = 2.14 mm (probe via, from -y radiating edge)
Why probe-fed: aperture-coupled v2 (4-layer Stack_Hybrid) capped at ~60 MHz BW
because the 0.11 mm L4 acts as a near-short reflector — beneficial for slot
coupling but creates an L2-L4 cavity that's the BW ceiling. Tested removing L4
(open-back aperture-coupled): coupling collapsed, R stayed >1000 Ω regardless
of patch tuning. Probe-fed has no slot bottleneck; physics BW = 1.7% on h=0.508
matches sim 180 MHz directly.
Hardware change required to deploy: 2-layer stackup (patch on top, ground on
bottom, probe vias with antipads). Old 8x16 Gerber was edge-fed; v3 is probe-
fed → top-layer feed network goes away, ADAR1000 carrier on a separate board
with SMP RF launches. Stackup signoff with antenna designer needed before PCB.
aperture_coupled_v2 retained as the 4-layer fallback (with the 0.043 pF cap)
if 2-layer redesign isn't approved.
10-iteration analytic-tune sweep (no DE optimizer — that was a wrong
direction for this topology) on the Stack_Hybrid 4-layer stackup. Key
findings from the sweep are baked into the script defaults and header.
Best design point @ 10.5 GHz (now the env-var defaults):
patch W=9.55 mm L=7.77 mm
slot L=3.00 mm W=0.50 mm (centered under patch)
stub L=4.16 mm (= λ_g/4 in feed sub at f0)
feed lead=12.34 mm W=0.25 mm
total feed length = 1·λ_g at 10.5 GHz, line transparent at f0
Result: Z ≈ R + j350 Ω at 10.5 GHz, R = 33–51 across reruns (sanity-profile
convergence drift; X is stable). R is within matching range; the +j350
inductive residual is fundamental to the topology (L4 backshort under the
antenna footprint), not a tuning artifact. Two production-grade fixes:
(a) Series cap at port C ≈ 0.043 pF — drops S11 to ≈ -40 dB
(b) Open L4 backshort under antenna — restores standard open-back
aperture-coupled, stub naturally tunes X
Three real bugs fixed in the underlying sim (without these, the baseline
script was measuring artifacts, not the antenna):
1. Z mesh under-density. Default SmoothMeshLines at λ/18 gave the 0.11 mm
feed substrate ~0.1 cells vertically — microstrip Z0 was a pure mesh
artifact. Now built explicitly with ≥5 substrate-interior lines per
dielectric (bypassing SmoothMeshLines collapse for z-axis only). Fine
substrate cells visible via MESH_DEBUG=1.
2. SLOT_Y_OFF_MM env var was read but never applied to the L2 slot box,
silently making the parameter inert. Slot is now correctly offset in y.
3. FEED_LEAD_L was hardcoded at 14.0 mm, making total feed length 18.16 mm
= exactly 1·λ_g at 9.5 GHz (in feed substrate). This created a parasitic
feed-line full-wave standing wave in-band that masked the patch as a
persistent "9.4 GHz resonance" regardless of patch dimensions. Now
parameterized via FEED_LEAD_L_MM with default 12.34 mm so total feed =
1·λ_g at 10.5 GHz instead — line is transparent at the operating freq
and sim measures the actual antenna impedance at the port.
Sweep grids updated to span ±1 step around the iter #6 design point.
Re-simulation infrastructure for the new 4-layer aperture-coupled antenna
stackup (Stack_Hybrid.png, committed 1de2296). Renders the full multilayer
geometry (L1 patch / L2 slot ground / L3 microstrip feed / L4 backplane)
on the actual substrate stack (RO4350B 0.508 mm + RO4450F 1.2 mm + RO4350B
0.11 mm) and runs FDTD via openEMS to characterize S11 vs frequency.
Geometry interpolated from existing 2-layer Gerber:
patch W from Gerber (7.854 mm, set by εr only)
patch L re-tunable for new substrate (env var PATCH_L_MM, default 7.25 mm)
slot/feed/stub fully parameterized via env vars
Run modes:
PROFILE=sanity : single run, λ/18 mesh, ~30 s
PROFILE=balanced : single run, λ/25 mesh, ~60 s
PROFILE=sweep : 5×5 grid over slot_L × stub_L, ~25 min
Env overrides for parametric exploration:
PATCH_W_MM, PATCH_L_MM, SLOT_L_MM, SLOT_W_MM, STUB_L_MM, SLOT_Y_OFF_MM
Setup: openEMS Python bindings built from source against /opt/openEMS for
Python 3.12 in radar_venv; run with
DYLD_LIBRARY_PATH=~/opt/openEMS/lib ~/radar_venv/bin/python
under cwd != openEMS-Project/openEMS/python (avoids CSXCAD shadow import).
Status: simulation infrastructure verified end-to-end; patch resonates at
10.4 GHz with W=9.0 / L=5.5–6.0 mm. Full 50 Ω impedance match not yet
converged — the L4 backplane (non-standard for aperture-coupled) reduces
slot coupling vs textbook formulas; needs proper EM optimizer (scipy
wrapping or CST/HFSS handoff) to fully tune. ~150 MHz baseline BW
predicted from substrate physics; 30/40 MHz chirp target comfortably
under any plausible match outcome.
Resolve all 374 ruff errors across 36 Python files (E501, E702, E722,
E741, F821, F841, invalid-syntax) bringing `ruff check .` to zero
errors repo-wide with line-length=100.
Rewrite CI workflow to use uv for dependency management, whole-repo
`ruff check .`, py_compile syntax gate, and merged python-tests job.
Add pyproject.toml with ruff config and uv dependency groups.
CI structure proposed by hcm444.
Jason