Physics / mechanism
Sub-THz covers roughly 100 GHz–1 THz; 6G standardisation targets 100–300 GHz sub-bands (D-band: 110–170 GHz, H-band: 220–330 GHz). Propagation follows free-space path loss ∝ f², so link budgets tighten fast — 10 dB/km atmospheric absorption peaks near 183 GHz and 325 GHz water-vapour lines. Available channel bandwidths reach 10–100 GHz, enabling >100 Gbps point-to-point at short range (<1 km). Key enablers: III-V HEMTs (InP, GaN) pushing fT/fmax above 500/700 GHz; SiGe BiCMOS reaching ~300 GHz fmax at lower cost; photonic-assisted THz generation via uni-travelling-carrier photodiodes hitting 1 mW+ at 300 GHz. IMT-2030 (6G) candidate bands lock in circa 2025–2026.
Competitive landscape
The primary competition is millimetre-wave 5G (24–71 GHz FR2), which has established ecosystem, lower path loss, and mature CMOS support. Optical FSO (free-space optical) competes for the same high-capacity short-haul backhaul use case with lower absorption but weather sensitivity. Within sub-THz, InP dominates performance, SiGe BiCMOS attacks cost, and GaN targets power. Integrated photonic approaches (III-V on Si) threaten to commoditise signal generation.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.