C-Band
Understanding C-Band
C-band was the original satellite communication frequency band. It remains important for international broadcasting, backbone telecommunications, and tropical-region services where rain attenuation at higher frequencies would be unacceptable.
C-Band Allocations
- Satellite downlink: 3.7-4.2 GHz (extended: 3.4-4.2 GHz)
- Satellite uplink: 5.925-6.425 GHz
- 5G/LTE: 3.3-4.2 GHz (n77, n78 bands). Major growth area for mid-band 5G.
- Weather radar: 5.3-5.7 GHz (C-band weather radar systems)
C-Band Advantages
- Rain resilience: Minimal rain attenuation (< 0.5 dB at 25 mm/hr). Ideal for tropical regions.
- Mature technology: Decades of proven satellite and terrestrial equipment.
- Wide coverage beams: Moderate antenna gain enables wide beam footprints for broadcast.
C-Band vs 5G Conflict
The FCC cleared 280 MHz of C-band spectrum (3.7-3.98 GHz) for 5G use, requiring satellite operators to move services to the upper portion (4.0-4.2 GHz) or other bands. This transition represents one of the largest spectrum reallocation efforts in history.
Wavelength: 7.5 - 3.75 cm
Standard waveguide: WR-137 (5.85-8.20 GHz)
Dimensions: 1.372 x 0.622 inches
FSPL at 6 GHz, 36,000 km (GEO): 199.5 dB
Rain attenuation at 6 GHz: negligible
Frequently Asked Questions
What is C-band used for?
C-band (4-8 GHz) is used for satellite communications (especially in tropical regions), weather radar, long-distance microwave links, and recently 5G cellular services in the 3.7-4.2 GHz range.
Why is C-band important for satellites?
C-band has minimal rain attenuation, providing high availability in tropical climates where Ku- and Ka-band links would suffer significant rain fade. It was the first satellite communication band and has extensive deployed infrastructure worldwide.
What happened with C-band and 5G?
The FCC reallocated 280 MHz of C-band spectrum (3.7-3.98 GHz) from satellite downlink to 5G cellular use. Satellite operators transitioned to the upper portion (4.0-4.2 GHz) and received compensation. This provides critical mid-band spectrum for 5G coverage and capacity.