Passive Bistatic / Multistatic Radar
Detection system that exploits ambient RF signals (FM broadcast, DVB-T, cellular, Starlink) reflecting off airborne targets. Emits nothing itself: invisible to adversary SIGINT and immune to anti-radiation drones. Among the few sensors that reliably detect RF-silent fiber-optic and fully autonomous drones.
How It Works
Receivers in dispersed positions compare the direct path of an illuminator (e.g. an FM tower) with the delayed reflection off a target. Time-difference-of-arrival and Doppler give 3D track. Networked multistatic geometry rejects clutter and extracts very low-RCS targets. Unlike active radar, no emission means no warning to the adversary.
Technical Specifications
Advantages
- + Zero emission: undetectable, immune to ARM/HARM-class threats
- + Detects fiber-optic and fully autonomous drones (no RF link required)
- + Hard to jam: adversary must jam the underlying broadcast/cellular network
- + Wide-area persistent surveillance
Disadvantages
- − Depends on local RF illumination environment (weak in remote terrain)
- − Long integration times: slower track update than active radar
- − Complex calibration and clutter rejection
- − High system cost per coverage area
Tactical Deployment Tips
- ▸ Position around rear-area HVTs (airfields, depots, CPs) where ambient RF is rich
- ▸ Cue to active sensors / effectors only when needed; this preserves passive advantage
- ▸ Combine multiple illuminators for redundancy if adversary takes one down
Limitations & Vulnerabilities
- ⚠ Poor performance in low-illumination environments (deep field, maritime)
- ⚠ Low-altitude clutter still degrades detection of nap-of-earth FPVs
Drones It Defeats
Drone types ranked by how well this system defeats them, tap any drone for detailsi
⚠ How Adversaries Defeat This System
Active enemy adaptations observed in the field, distinct from passive limitations above
- ▸ Adversary destroying or jamming the underlying broadcast illuminators
- ▸ Very low-altitude terrain-masked flight paths
- ▸ Stealth shaping / RAM coatings on high-end UCAVs