Reflection |Γ| vs frequency — Salisbury screen (sheet ‖ shorted spacer)

|Γ| this design −10 dB (90% absorbed) Protected band (≤ −10 dB)
Salisbury screen design
Spacer depth d7.5 mm
Sheet Rs377 Ω/□
Fundamental null f₀
—
f₀ = c / (4d)
Band coverage
—
of 2–18 GHz ≤ −10 dB
Protected sub-bands (GHz)
—
—
One resonant layer is a promise kept at exactly one frequency. Doubling d buys the low band but hands X-band — where fire-control threats live — right back.

Signal level vs range — one-way (R²) vs two-way (R⁴)

Radar echo at radar (1/R⁴) Radar signal at RWR (1/R²) Detection thresholds Detect-before-detected band
Engagement geometry
Range R80 km
Echo at radar
—
two-way, 1/R⁴
Signal at RWR
—
one-way, 1/R²
Radar threshold
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RWR threshold
—
—
Block 2 → Block 3: the radar pays R⁴ to see you; you pay R² to hear it. Shaping and RAM shrink σ, but the one-way advantage is what buys detect-before-detected.