What frequency bands above 100 GHz are being studied for 6G wireless communication?
6G Sub-THz Bands
Sub-THz communications is the defining technology challenge for 6G. The bandwidth available at 100-300 GHz (tens of GHz per channel) dwarfs the bandwidth available at 5G mmWave (100-400 MHz per channel), enabling data rates of 100+ Gbps per link.
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
- Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture
- Margin allocation: include sufficient design margin to account for manufacturing tolerances and aging effects
Frequently Asked Questions
What data rates are possible?
Data rates at sub-THz frequencies: with 10 GHz of bandwidth (a single wideband channel at D-band): using 64-QAM modulation: 10 GHz × 6 bits/symbol = 60 Gbps (single polarization, single stream). With 2×2 MIMO and dual polarization: 240 Gbps. With higher-order modulation (256-QAM): 320 Gbps. Research demonstrations: NTT has demonstrated 100 Gbps at 300 GHz. Samsung has demonstrated 5.23 Gbps at 140 GHz. University of Stuttgart has demonstrated 100+ Gbps at 230 GHz. These data rates are 10-100× higher than what 5G mmWave achieves, and are needed for: holographic communications, digital twins, immersive XR, and high-fidelity wireless backhaul.
What are the main challenges?
Main challenges for sub-THz communications: high path loss (the Friis free-space loss increases as f^2; at 150 GHz: 20 dB more loss than at 28 GHz for the same distance). Limited transmit power (current semiconductor technology produces limited output power at 100-300 GHz: InP HEMT: 10-100 mW at 150 GHz. SiGe BiCMOS: 1-10 mW at 150 GHz. CMOS: less than 1 mW at 150 GHz). Atmospheric absorption (water vapor and oxygen absorption lines create frequency-dependent attenuation that limits range). Semiconductor noise (the noise figure of amplifiers increases at higher frequencies, reducing sensitivity). Packaging (waveguide-to-chip transitions, antenna-IC integration, and thermal management at these frequencies are extremely challenging).
What semiconductor technologies are used?
Semiconductor technologies for sub-THz: InP HEMT (Indium Phosphide High Electron Mobility Transistor): the highest performance at 100-300 GHz. f_T greater than 700 GHz. Used by: research labs, defense, and early 6G prototypes. Very expensive, limited foundry access. SiGe BiCMOS: reaching usable performance at 100-200 GHz with advanced nodes (130nm and 55nm). f_T: 300-500 GHz. Lower cost than InP, better integration capability. CMOS: 28nm and below CMOS can amplify at 100-200 GHz (f_T: 250-350 GHz). The lowest cost and highest integration but: lowest output power and highest noise figure. GaN HEMT: being explored for sub-THz power amplification (higher power than InP but currently limited to 100-150 GHz). The trend: SiGe and CMOS will likely dominate commercial 6G sub-THz transceivers due to cost and integration advantages, while InP will be used for the highest-performance applications.