ADR-091: Stand-off Radar Tier Research — 77 GHz High-Power and 100–200 GHz Coherent Sub-THz

1. Context

1.1 Why this question now

On Good Friday 3 April 2026 the press reported a CIA system called "Ghost Murmur" — a Lockheed Skunk Works NV-diamond + AI sensor reportedly used in the recovery of an F-15E pilot in southern Iran. President Trump publicly suggested detection ranges in the "tens of miles" against a single human heartbeat. RuView shipped a research spec (16-ghost-murmur-ruview-spec.md) which (a) reality-checked the press claims against published physics, (b) mapped the honestly-scoped version onto the existing RuView three-tier mesh, and (c) explicitly deferred one modality — high-power and sub-THz coherent radar — as out of scope. From §6.3 of that spec:

77 GHz automotive radars at higher power and 100–200 GHz coherent sub-THz radars can resolve cardiac micro-Doppler at 50–500 m in clear LOS. These are not COTS at the $15 price point and are not in the RuView stack today. They are also subject to ITAR / export-control review and explicitly out of scope for this open-source project.

That sentence is the trigger for this ADR. We need a written, citable record of why the decision is "out of scope today", what would change the decision, and — crucially — what shape any future research entry into this band would take, given that even the research itself touches dual-use territory.

1.2 What gap a higher-frequency / higher-power tier would close

RuView's existing modality coverage (per the CLAUDE.md crate table):

The ceiling of this stack on cardiac micro-Doppler in clear line-of-sight is ~10 m (60 GHz tier, ADR-021 / spec §6.1). A higher-frequency / higher-power tier would, in principle, close the 10–500 m gap that the published radar literature has already explored. The two candidate bands:

1. 77–81 GHz at higher than typical commercial EIRP — the same band as automotive radar, where the FCC ceiling is 50 dBm average / 55 dBm peak EIRP under 47 CFR §95.M, and where published academic work has measured HR at ranges beyond the typical 1–3 m used by COTS automotive sensors.
2. 100–200 GHz coherent sub-THz radar — where λ ≈ 1.5–3 mm gives sub-millimetre chest-wall displacement resolution and where atmospheric transmission windows at 94 GHz, 140 GHz, and 220 GHz make stand-off sensing physically possible (with caveats on humidity, antenna gain, and integration time).

This ADR examines both bands — the SOTA, the COTS reality, the regulatory envelope, the physics ceiling, the export-control posture, and the open-source ethics — and lands at a build / research / skip recommendation per row.

2. SOTA: 77–81 GHz automotive radar at higher power

2.1 Current COTS chips at the $20–$200 price point

The 76–81 GHz band is now densely populated with single-chip CMOS / SiGe transceivers. Representative parts:

COTS evaluation boards (TI AWR1843BOOST, AWR2243 cascade kits) sit in the $300–$3,000 range; single-board production costs trend toward $20–$100 at volume. None of these chips is, by itself, export-controlled at typical configurations — the band is allocated for civilian automotive use under FCC Part 95 Subpart M and ETSI EN 301 091 in Europe.

EIRP envelope: 47 CFR §95.M (and the historical §15.253 it replaced) caps the 76–81 GHz band at 50 dBm average / 55 dBm peak EIRP measured in 1 MHz RBW (Federal Register notice 2017, eCFR 47 CFR Part 95 Subpart M). That is roughly 100 W EIRP average, 316 W peak. COTS automotive radars typically operate well below this — single-digit dBm transmit power is multiplied by ~25–30 dBi antenna gain to land at 33–40 dBm EIRP.

2.2 What "higher power" actually means in regulatory terms

Three regulatory paths exist for an open-source project that wants to push beyond typical commercial deployment power:

1. Stay inside FCC Part 95 §95.M caps (50 dBm avg / 55 dBm peak EIRP) — licence-by-rule, no application, no individual approval. The headroom from typical automotive EIRP (~33–40 dBm) to the cap (50 dBm avg) is real: ~10 dB of additional EIRP is available without changing licence class, purely by using a higher-gain dish or higher Tx power within the existing chip. This is the upper bound of "stand-off radar that is still part-95 legal".
2. FCC Part 5 experimental licence — needed for transmit power, antenna gain, or duty-cycle that exceeds §95.M. Application-based, time-bounded, non-renewable beyond limits. Typical academic radar ranges (e.g. the long-range cardiac measurements in §2.3 below) operate under this regime.
3. No US authorisation at all — only legal as receive-only, or as a simulator. Any unlicensed transmission above §95.M at 76–81 GHz is a prohibited emission under 47 CFR §15.5 / §95.335.

For an open-source mesh node shipping to anonymous users worldwide, only path (1) is defensible. Anything that requires an individual experimental licence cannot be "ship a binary and let people flash it".

2.3 Published cardiac micro-Doppler at 77 GHz beyond 5 m

The 77 GHz cardiac literature is dominated by short-range work (0.3–2 m), e.g.:

• Chen et al. (2024). "Contactless and short-range vital signs detection with doppler radar millimetre-wave (76–81 GHz) sensing firmware." Healthcare Technology Letters. (PMC11665778, Wiley HTL 2024) — TI IWR1443BOOST at 0.30–1.20 m, suggested 0.6 m.
• Wang et al. (2020). "Remote Monitoring of Human Vital Signs Based on 77-GHz mm-Wave FMCW Radar." Sensors 20, 2999. (PMC7285495, MDPI Sensors 2020) — typically short-range bench measurements.
• Liu et al. (2022). "Real-Time Heart Rate Detection Method Based on 77 GHz FMCW Radar." Micromachines 13, 1960. (PMC9693980, MDPI) — 2.925% mean HR error, short-range.
• Iyer et al. (2022). "mm-Wave Radar-Based Vital Signs Monitoring and Arrhythmia Detection Using Machine Learning." Sensors. (PMC9104941)

The most cited long-range radar cardiac measurement is at 24 GHz, not 77 GHz:

• Massagram, W., Lubecke, V. M., Høst-Madsen, A., Boric-Lubecke, O. (2013). "Parametric Study of Antennas for Long Range Doppler Radar Heart Rate Detection." IEEE EMBC / republished in PMC. (PMC4900816, PubMed 23366747) — measured human HR at distances of 1, 3, 6, 9, 12, 15, 18, 21 m and respiration to 69 m with a PA24-16 antenna at 24 GHz CW Doppler. This is the ceiling reference for "what's achievable with serious antenna gain in clear LOS, low band, with subject cued and stationary".

We could not find an equivalent peer-reviewed cardiac measurement at 77 GHz beyond ~5 m with a verifiable antenna gain × power × integration-time budget. The work that exists at 77 GHz is overwhelmingly bench-scale (≤ 2 m). This is itself informative: it suggests that the open published frontier at 77 GHz beyond 5 m is sparse, not because it's impossible, but because the research community working at automotive bands has been focused on automotive problems (collision avoidance, in-cabin occupancy) where 5 m suffices, and because higher-range cardiac work has historically used 24 GHz where the antenna size for a given gain is more practical.

2.4 Detection range as a function of antenna gain × power × integration time

The radar equation for chest-wall displacement detection scales roughly as:

SNR ∝ (P_t · G_t · G_r · σ_chest) / (R^4 · k T B · NF) · √(t_int / T_coh)

where σ_chest ≈ 10⁻³–10⁻² m² for the cardiac scatterer at 77 GHz, NF ≈ 10–15 dB on COTS chips, and integration time t_int is bounded by T_coh ≈ 0.5–1 s (physiological coherence — the heart period itself).

Doubling range requires 12 dB of system gain (4-th power dependence on R, two-way). At the part-95 §95.M ceiling (50 dBm avg EIRP) and a generous 30 dB antenna gain (a ~30 cm dish at 77 GHz), the addressable HR detection range in clear LOS is roughly 15–30 m for a stationary cued subject, dropping to 3–10 m for an uncued subject in light clutter. Pushing to 100 m+ in an open field would require either (a) a much larger antenna (60+ cm dish), (b) out-of-band EIRP beyond §95.M (experimental licence territory), or (c) much longer integration (incompatible with cardiac coherence times).

The 2013 Massagram paper achieves 21 m at 24 GHz with a high-gain antenna under tightly controlled conditions. Pushing the same setup to 77 GHz with the same antenna aperture would actually help (smaller beamwidth, same free-space path loss), but the chest-wall RCS at 77 GHz is comparable, and clutter / multipath are much harsher. We have no public reference for a 77 GHz cardiac measurement at 21 m that we could find with the same rigour.

2.5 Cost ceiling for an open-source mesh node

An open-source mesh node spec implies "ships in a kit, does not require individual licensing, fits the existing PoE / mini-PC edge model". That implies:

• Single-chip transceiver at $20–$100 BOM.
• Antenna assembly at $50–$200 (high-gain dish or printed array).
• Mini-PC or Pi 5 host at $80.
• Total under $500 to be plausible.

The chip cost is already met by COTS. The antenna and host are met. The bottleneck is not hardware cost — it is regulatory exposure, dual-use ethics, and the fact that the addressable range at part-95 ceilings (15–30 m) is only marginally beyond what the existing 60 GHz tier already does for $15. The marginal technical benefit of jumping to 77 GHz at the part-95 ceiling, for a civilian opt-in mesh, does not clear the marginal governance cost.

3. SOTA: 100–200 GHz coherent sub-THz radar

3.1 Why sub-THz

At 140 GHz, λ ≈ 2.14 mm. A coherent radar with this wavelength can resolve chest-wall displacement at the sub-millimetre level by direct phase tracking, which makes the cardiac micro-Doppler signal-to-clutter ratio fundamentally better than at 60 or 77 GHz for the same integration time. Atmospheric windows at 94 GHz, 140 GHz, and 220 GHz — between the strong oxygen absorption peaks at 60 GHz and 119 GHz and the water vapour peaks at 22, 183, and 325 GHz — make stand-off operation physically possible per ITU-R Recommendation P.676 (ITU-R P.676-11, ITU-R P.676-9).

3.2 Atmospheric attenuation table (clear-air, ITU-R P.676)

Order-of-magnitude values for one-way attenuation through standard atmosphere at sea level, taken from ITU-R P.676-11 Annex 1 / 2 figures (approximate values; consult the recommendation for precise numbers at any (T, P, ρ)):

For a 100 m one-way clear-LOS link at 140 GHz in 7.5 g/m³ humidity, atmospheric attenuation alone is ~0.15 dB — negligible compared to free-space path loss (~115 dB at 100 m) and target RCS. The atmosphere is not the limiting factor for sub-THz cardiac sensing inside ~100 m. Beyond ~1 km in humid conditions, atmospheric absorption dominates and the budget breaks down quickly, especially at 220 GHz and above.

3.3 COTS chipsets and academic platforms

The sub-THz commercial landscape in 2026 is sparse and expensive:

• Analog Devices HMC8108 — 76–81 GHz transceiver. Not sub-THz; named here only to anchor "the most COTS-friendly mmWave part Analog Devices ships".
• Virginia Diodes WR- multipliers and mixers* — the dominant lab-grade source for 140–500 GHz work. Module prices are $5,000–$50,000 each; building a coherent transceiver typically requires $30,000–$150,000 of VDI hardware plus a stable phase reference and an external RF source.
• Wasa Millimeter Wave imagers — passive imagers around 90 / 220 / 380 GHz. Receive-only.
• imec 140 GHz FMCW transceiver in 28 nm CMOS — reported at IEEE ISSCC and in Microwave Journal (2019), centred at 145 GHz with 13 GHz RF bandwidth giving 11 mm range resolution, on-chip antennas, integrated Tx / Rx in 28 nm bulk CMOS. (Microwave Journal 2019, imec magazine May 2019) This is the most COTS-relevant sub-THz cardiac chip published to date, but it is not a buyable part — it is a research demo.
• Academic platforms at Tampere University, FAU Erlangen-Nürnberg, Bell Labs / Nokia, MIT Lincoln Lab, and the various US NSF / DARPA-funded sub-THz programmes have produced sub-THz radars in the 100–300 GHz band. None of these is a ship-it part.

3.4 Coherent vs. incoherent

A coherent sub-THz radar maintains phase reference between Tx and Rx (and ideally across multiple Tx / Rx channels for MIMO or multistatic operation). Coherent processing buys:

• Matched-filter SNR scaling: SNR improves linearly with integration time t (vs. √t for incoherent), bounded by the cardiac coherence time T_coh.
• Phase-based displacement extraction: chest-wall displacement at the micrometre level becomes directly observable as Δφ = 4π·Δd / λ.
• MIMO / multistatic phase coherence: multiple Tx / Rx phase-coherent channels enable beamforming gain that scales as N_Tx × N_Rx instead of √(N_Tx × N_Rx).

It costs:

• Sub-picosecond clock distribution between channels at sub-THz frequencies (a 1 ps clock skew at 140 GHz is 50° of phase error).
• Phase-locked LO distribution — the LO must be coherent across the array; this is non-trivial at 140 GHz (typical solution: distribute a low GHz reference and multiply locally, with cm-precision cable matching).
• Calibration burden — phase-coherent arrays need per-channel calibration drift correction.

For a single-aperture monostatic radar (one Tx, one Rx, one chip), coherence is nearly free (the LO is shared on-die). For a mesh of coherent sub-THz nodes, the engineering cost is significant — and would require RuView to develop sub-ns mesh clock-synchronisation it does not have today.

3.5 Published cardiac micro-Doppler at sub-THz

The published peer-reviewed cardiac literature at 100–300 GHz is sparse but not empty:

• Mostafanezhad & Boric-Lubecke (2014). "Benefits of coherent low-IF for vital signs monitoring." IEEE Microw. Wireless Compon. Lett. 24. — anchor for coherent CW vital-signs radar; not specifically sub-THz, but establishes the coherent-IF advantage.
• imec (2019) — 140 GHz FMCW transceiver demonstration. Reported real-time measurement of micro-skin motion reflecting respiration and heartbeat at short range using an integrated 28 nm CMOS transceiver with on-chip antennas. Cited above; engineering demo, not a published systematic range study. (Microwave Journal 2019)
• Yamagishi et al. (2022). "A new principle of pulse detection based on terahertz wave plethysmography." Scientific Reports 12, 2022. (Nature SREP) — THz-band plethysmography demonstrator, contactless pulse detection at very short range using THz transmission/reflection through skin. Not a stand-off radar paper, but the only widely-cited THz-cardiac primary source.
• Zhang et al. (2021). "Non-Contact Monitoring of Human Vital Signs Using FMCW Millimeter Wave Radar in the 120 GHz Band." Sensors 21. (PMC8070581) — 120 GHz band, FMCW, short-range cardiac extraction.

Honest assessment: published primary work on cardiac micro-Doppler at beyond a few meters in the 100–300 GHz band is limited. The imec / EU-funded demonstrators have shown that the chip exists; the systematic range studies that exist for 24 GHz (Massagram 2013) and 60–77 GHz (Adib / Wang / Liu) do not yet have published sub-THz analogues. Some of this work may exist in the classified or US-Government / EU defence-funded literature; it is not in the open record at the level of detail required for a build decision.

4. Physics ceiling for RuView's heartbeat-mesh use case

4.1 Cardiac signal vs. distance, multi-band comparison

For a stationary, cued, line-of-sight subject with chest-wall displacement ~0.2 mm at the heart fundamental and ~5 mm at the breathing fundamental, order-of-magnitude HR-detection range estimates at three bands (compiled from the radar equation, Massagram 2013, ITU-R P.676, and standard chest-RCS estimates):

The phase-displacement resolution improves with frequency (Δφ for the same displacement scales as 1/λ), but the link budget degrades (R⁻⁴ in two-way path loss, plus atmospheric absorption, plus higher noise figure on sub-THz LNAs). The two effects partially cancel; the net result is that every doubling in frequency above 60 GHz buys roughly a factor of 2–4× in plausible HR range when antenna aperture is held constant — but only if the system noise figure and Tx power can be maintained at levels comparable to the lower-band part. Sub-THz CMOS NF is typically 10 dB worse than 77 GHz CMOS, which eats much of the apparent gain.

4.2 Two-way path loss + atmospheric absorption

Observations:

• At 1 km, 220 GHz loses 9 dB more to atmosphere than 77 GHz; at 10 km it loses 90 dB more. Sub-THz is fundamentally a sub-1-km modality in humid air.
• At 65 km (the "40 miles" in the press), atmospheric absorption alone makes 220 GHz cardiac detection physically impossible at any plausible Tx power. 140 GHz needs 200+ dB of antenna gain on each end to close the link in humid air — far beyond any deployable antenna.
• 77 GHz is the only band where 1 km cardiac sensing is physically plausible in the open air. It is also the band that is closest to civilian COTS.

4.3 Required antenna gain × power × integration time

Holding integration time at 0.5 s (half a cardiac cycle, the rough coherence limit), and assuming a 10 dB SNR target at 0.2 mm displacement, the required EIRP × antenna-gain product to detect HR at various ranges in clear LOS at 77 GHz:

Bottom line: 30 m is the honest ceiling for cardiac sensing inside FCC §95.M power limits with a 30 cm dish at 77 GHz. Anything beyond ~30 m is either experimental-licence territory or military.

4.4 Fold-over with the Ghost Murmur "tens of miles" claim

The press claim of HR detection at "40 miles" (65 km) corresponds to a one-way path loss at 77 GHz of roughly 168 dB (free space) plus ~65 dB of atmospheric absorption (humid). Closing this link to detect a 0.2 mm chest-wall displacement would require:

• Required EIRP: roughly 200 dBm (10²⁰ W) in the simplest analysis. For context, the entire global average solar flux is ~1.4 kW/m². A 65 km radar would need to deliver more transmit power, focused onto a single human chest, than the sun delivers to that chest by daylight.
• Required antenna: even with 100 dB of combined two-way antenna gain (a 6 m dish at 77 GHz), the EIRP requirement is unphysical.
• Required atmospheric conditions: dry, stable, no rain, no fog, no intervening terrain.

The honest reading: HR detection at "tens of miles" against a single heartbeat is not consistent with any physically realisable open-air radar system at any band the laws of physics allow. The claim either refers to cued detection (i.e., a survival beacon or IR thermal already pinpointed the target, the radar is just confirming "alive"), or it is press-release hyperbole. RuView is not in a position to either confirm or contest the operational reality; we are in a position to say that the modality alone — "detect a heartbeat at 40 miles with a radar" — is not what closed the loop.

This is consistent with the Ghost Murmur spec's analysis (§4 of doc 16) and with nvsim's magnetic-field falloff calculations (1/r³ — even more brutal than radar's 1/r⁴).

5. Regulatory + ethics

5.1 FCC envelope summary

For an open-source civilian project, only the unlicensed and part-95 licensed-by-rule categories are defensible. The moment a node would need an individual experimental-licence application to operate legally, it cannot be "flash and ship".

5.2 ITAR / EAR posture

• ECCN 6A008 controls radar systems and components under the EAR (BIS Commerce Control List Cat. 6). The general radar control sub-paragraph 6A008.e covers "radar systems, having any of the following characteristics" — including high power, specific frequency / coherence properties, and certain processing capabilities. The exact thresholds change from revision to revision; the current authoritative source is the BIS Interactive Commerce Control List.
• USML Category XI(c) (ITAR) covers radar that is specifically designed or modified for military application. Sub-THz coherent radar with the combination of frequency, coherence, and antenna gain that would matter for stand-off cardiac sensing tends to fall in or near this category.
• EAR99 / no-licence-required thresholds for low-power 60–77 GHz automotive radar are clear. Sub-THz coherent radar above certain thresholds (ECCN 6A008) requires an export licence for many destinations. Some open-source firmware that implements such a radar may be subject to "publicly available" exemptions; some may not.
• Open-source publication. EAR §734.7 / §734.8 ("publicly available information") exempts most code that has been or will be published openly. However, this exemption has limits — particularly for "specially designed" technology supporting controlled commodities, and for encryption / certain munitions categories. The line for radar firmware is not fully clear, and the safe path for an open-source project is: do not publish firmware whose primary purpose is to push a controlled-radar configuration.

The correct posture for RuView is: assume the worst case. If RuView shipped firmware that drove a 140 GHz coherent sub-THz cardiac mesh, even without the hardware in the workspace, that firmware itself could fall within ECCN 6A008 / USML XI(c), particularly if it implemented the matched-filter / coherent-array signal processing that distinguishes controlled radars from uncontrolled ones. We do not ship that firmware.

5.3 Open-source ethics and dual-use risk

The Ghost Murmur spec (§9) is explicit about RuView's civilian-only ethics framing:

1. Civilian, opt-in deployments only.
2. No directional pursuit.
3. Data minimisation.
4. PII detection on the wire.
5. Adversarial-signal detection.
6. No export-controlled hardware.

Stand-off radar at 77 GHz with §95.M-ceiling EIRP and a 30 cm dish can be used for through-wall surveillance, biometric tracking, target acquisition. Sub-THz coherent radar can do the same with finer resolution. Even research into these modalities — building a simulator, publishing range / sensitivity analyses, contributing to the open literature — pushes the open-source ecosystem closer to capabilities that the press already (correctly, in the sense of "physically possible") associates with covert military intelligence.

Two specific dual-use risks if RuView research were to ship anything beyond this ADR:

• Through-wall surveillance: high-power 77 GHz radar with a wide-band FMCW chirp can resolve human presence and coarse pose through interior drywall at tens of meters. This is the literal Ghost Murmur use case at short range. RuView already discloses this capability for the existing 60 GHz tier; pushing it to 77 GHz at higher power expands the addressable surveillance distance.
• Biometric tracking at distance: cardiac and respiratory micro-Doppler signatures are individually identifying enough for re-identification across short occlusions (this is part of the AETHER / re-ID work in ADR-024). Combining higher-power radar with re-ID at 30+ m is surveillance at distance.
• Target acquisition: this is the use case RuView explicitly does not build for. Period.

6. Build / Research / Skip decision matrix

The recommendation density is intentional: most of the matrix lands on "skip" or "research only". Only one row (77 GHz at the §95.M ceiling) sits near a build decision, and even that one is gated on a use case that does not exist in RuView today.

7. If we research: what does RuView ship?

7.1 Mirror the nvsim pattern

ADR-089 / 090 established the precedent: when a sensing modality is physically interesting but not buildable today, RuView ships a deterministic forward simulator, not hardware. The simulator becomes the design tool for fusion algorithms, the sanity check for press-release physics, and the honest answer to "what would you actually need to build this?"

Applied to this ADR, the corresponding artifact would be a sub-THz radar forward simulator crate, working name subthz-radar-sim. Scope:

• Forward-model the 77 GHz / 140 GHz / 220 GHz radar equation including ITU-R P.676 atmospheric attenuation, free-space path loss, antenna gain patterns, and chest-RCS models.
• Simulate cardiac micro-Doppler displacement → received-signal phase modulation in the FMCW or CW-Doppler regime.
• Add deterministic noise (thermal + 1/f LO phase noise + chest-RCS fluctuation) seeded from rand_chacha for byte-identical outputs across runs.
• Emit RadarFrame-shaped output with magic distinct from 0xC51A_6E70 (nvsim's MagFrame) and 0xC511_0001 (CSI frames).
• SHA-256 witness for end-to-end determinism, mirroring nvsim::Pipeline::run_with_witness.

7.2 Hard constraints on what the crate can ship

• No firmware. Not for ESP32, not for any SDR, not for any FPGA. The crate is host-side only. No executable binary capable of driving a sub-THz transmitter is published.
• No matched-filter / coherent-array signal processing that exceeds ECCN 6A008 thresholds. The crate documents the physics and simulates the forward path. It does not implement the inverse / processing pipeline at the level that would constitute a controlled radar processor.
• No beamforming primitives for actively-steered phased arrays. Simulating a fixed-pattern dish is fine; simulating a steerable phased array used for targeted person-of-interest tracking is not.
• No re-identification across the simulated radar stream. AETHER-style re-ID exists in ruvector/viewpoint/; it must not be wired to the sub-THz radar simulator's output.
• Documented dual-use posture. The crate's README starts with a section titled "What this crate is not for", linking to this ADR.

7.3 What the simulator answers

The same questions nvsim answers for NV-diamond, the sub-THz simulator would answer for radar:

• "If a 140 GHz transceiver has noise figure 12 dB and Tx power 0 dBm with a 35 dBi antenna, what's the joint posterior P(human alive at (x, y)) given my CSI + 60 GHz + 77 GHz + 140 GHz radar evidence at 5 m, 30 m, 100 m?"
• "What sensitivity does my hypothetical 220 GHz radar need to add useful information beyond the 60 GHz tier at 10 m? And does the answer change in 7.5 g/m³ humidity vs. 1 g/m³ dry air?"
• "What does my published witness change if I swap the receiver noise figure from 8 dB to 15 dB? From 15 dB to 25 dB?"

These are pre-build sanity checks. They cost CI time, not export-control exposure, not dual-use risk, not regulatory exposure.

7.4 Conditional triggers (mirror ADR-090's pattern)

Promotion of any "research only" row in §6 to "build" requires all three of:

1. A COTS sub-THz transceiver drops below $1k at the chip level, with datasheet-confirmed phase coherence and an evaluation board buildable on open hardware. (Today: nothing.)
2. A clear non-export-controlled application emerges — most plausibly medical: contactless vital-sign monitoring at clinical bedside or ambulatory ranges (1–3 m), regulated by the FDA as a medical device, with the commercial / regulatory path paved by another vendor. RuView would then be one of many open-source contributors to a medical sensing modality already cleared for civilian use.
3. RuView core team agrees by RFC, with explicit sign-off on the dual-use review and the ethics framing in §5.3.

If any one of those three is missing, this ADR remains Proposed indefinitely and the modality stays in the simulator-only tier.

If only condition (1) fires — sub-$1k chip with no medical clearance and no RFC sign-off — RuView still does not ship. The simulator might be expanded; no firmware ships.

8. Related work / cross-references

8.1 ADRs

• ADR-021 — Vital-sign detection via 60 GHz mmWave + WiFi CSI. The tier immediately below this ADR; defines the 1–10 m HR ceiling that a stand-off tier would extend.
• ADR-029 — RuvSense multistatic sensing mode. Defines the cross-viewpoint fusion that any future radar tier would feed. The mathematical framework for combining radar + CSI + NV evidence is already in ruvector/viewpoint/.
• ADR-089 — nvsim NV-diamond pipeline simulator. The architectural precedent: ship a deterministic forward simulator when the modality is interesting but not buildable. Same proof / witness pattern applies here.
• ADR-090 — nvsim Lindblad / Hamiltonian extension. Same "Proposed conditional" pattern with explicit trigger conditions and a deferred build. This ADR follows the same shape.
• ADR-040 — PII detection gates. Any future stand-off radar output stream would need to flow through PII gates before crossing the local mesh boundary, identical to existing CSI / vitals streams.
• ADR-024 — AETHER contrastive embedding. Cross-references the re-identification work that must not be combined with stand-off radar.
• ADR-028 — ESP32 capability audit + witness verification. The deterministic-witness pattern applies to any new simulator crate.

8.2 Research docs

• docs/research/quantum-sensing/16-ghost-murmur-ruview-spec.md — the Ghost Murmur reality-check spec. §6.3 is the explicit boundary that triggered this ADR. §7–§9 establish the architecture, ethics, and legal framework that this ADR inherits.

8.3 Primary literature (radar at 24 / 77 / 120–140 GHz)

• Massagram, W., Lubecke, V. M., Høst-Madsen, A., Boric-Lubecke, O. (2013). "Parametric Study of Antennas for Long Range Doppler Radar Heart Rate Detection." IEEE EMBC 2013. (PMC4900816) — HR @ 21 m, respiration @ 69 m at 24 GHz CW.
• Mostafanezhad, I., Boric-Lubecke, O. (2014). "Benefits of Coherent Low-IF for Vital Signs Monitoring." IEEE Microw. Wireless Compon. Lett. 24(10), 711–713.
• Adib, F. et al. (2015). "Smart Homes that Monitor Breathing and Heart Rate." Proc. CHI 2015. Short-range through-wall.
• Wang, G. et al. (2020). "Remote Monitoring of Human Vital Signs Based on 77-GHz mm-Wave FMCW Radar." Sensors 20(10), 2999. (PMC7285495)
• Liu, J. et al. (2022). "Real-Time Heart Rate Detection Method Based on 77 GHz FMCW Radar." Micromachines 13(11), 1960. (PMC9693980)
• Chen, J. et al. (2024). "Contactless and Short-Range Vital Signs Detection with Doppler Radar Millimetre-Wave (76–81 GHz) Sensing Firmware." Healthcare Technology Letters 11. (Wiley HTL)
• Iyer, S. et al. (2022). "mm-Wave Radar-Based Vital Signs Monitoring and Arrhythmia Detection Using Machine Learning." Sensors. (PMC9104941)

8.4 Primary literature (sub-THz)

• imec / Peeters et al. (2019). Integrated 140 GHz FMCW Radar Transceiver in 28 nm CMOS for Vital Sign Monitoring and Gesture Recognition. Microwave Journal 2019-06-09; imec magazine May 2019. (Microwave Journal, imec magazine)
• Zhang, Q. et al. (2021). "Non-Contact Monitoring of Human Vital Signs Using FMCW Millimeter Wave Radar in the 120 GHz Band." Sensors 21. (PMC8070581)
• Yamagishi, H. et al. (2022). "A new principle of pulse detection based on terahertz wave plethysmography." Scientific Reports 12, 2022. (Nature SREP)
• ITU-R Recommendation P.676-11 (2016). "Attenuation by atmospheric gases." International Telecommunication Union. (P.676-11 PDF)
• 47 CFR Part 95 Subpart M — The 76–81 GHz Band Radar Service. (eCFR)
• US Department of Commerce, Bureau of Industry and Security. Commerce Control List Category 6 — Sensors and Lasers, ECCN 6A008. (BIS CCL Cat. 6)

8.5 Reviews

• Li, C. et al. (2024). "Radar-Based Heart Cardiac Activity Measurements: A Review." Sensors. (PMC11645089)
• Frontiers in Physiology (2022). "Radar-based remote physiological sensing: Progress, challenges, and opportunities." (Frontiers)

9. Open questions

These are the questions that, if answered differently, could move a row of the §6 decision matrix:

1. Does a published, peer-reviewed cardiac micro-Doppler measurement at 77 GHz beyond 5 m exist that we missed? A rigorous Massagram-style parametric study at 77 GHz with explicit antenna-gain × Tx-power × integration-time budgets would change the picture for the "77 GHz higher power" row from "research only" toward "build (simulator + reference implementation)".
2. Does a sub-$1k 140 GHz coherent transceiver chip exist or appear in the next 12 months? The imec 28 nm CMOS demo from 2019 has not yet led to a buyable part; it is unclear whether this is an engineering / yield issue or a market issue. If a part appears, condition (1) of §7.4 fires.
3. Is there a clear medical FDA-cleared application for sub-THz cardiac sensing? This is the single most important gating condition. If a commercial vendor clears a 140 GHz contactless vital-sign monitor as a Class II medical device, the entire ethical framing of "open-source contribution to a medical sensing modality" opens up. Without that clearance, RuView remains in the simulator-only tier.
4. Are there current ECCN 6A008 thresholds we should be more concerned about for the simulator itself than the §5.2 analysis suggests? The simulator is forward-only and emits IQ samples and a SHA-256 witness. It does not implement matched-filter / coherent-array processing that would be characteristic of controlled radars. We believe this is on the right side of the line; a formal export-control review by counsel would confirm.
5. Should RuView contribute the sub-THz simulator to a neutral upstream (e.g., an open-source academic group's repository) rather than shipping it in the wifi-densepose workspace? Decoupling the simulator from RuView reduces the risk that future RuView capability work is interpreted as building toward a stand-off cardiac mesh.
6. What's the right venue for the deterministic-proof bundle for the sub-THz simulator? Same question that ADR-089 left open. Probably the same answer: in-tree fixture + tagged release artifact.

10. Decision summary

This ADR is Proposed — Research only. The decision matrix in §6 lands on:

• Skip permanently: 77 GHz beyond §95.M, 220 GHz coherent stand-off hardware, 380+ GHz imaging.
• Research only (simulator-class artifact): 77 GHz higher-power experimental (≤ §95.M ceiling), 100 GHz coherent mesh, 140 GHz coherent stand-off.
• Build now: nothing.

If RuView builds anything in this space, it builds a sub-THz forward simulator (subthz-radar-sim) following the nvsim pattern: deterministic, host-side, witness-verified, with explicit "what this is not for" framing and no firmware. The simulator does not ship until conditions §7.4 (1)–(3) all fire; the hardware does not ship under any conditions current as of 2026-04-26.

The ADR's job is to make these decisions citable, defensible, and reversible only via explicit RFC. It is not a build commitment.