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https://github.com/NawfalMotii79/PLFM_RADAR.git
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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
