Active Antenna System
Understanding Active Antenna Systems
AAS represents the convergence of radio and antenna technologies. By putting the radio directly behind the antenna elements, AAS eliminates the biggest loss (feeder cable) in the radio link and enables advanced beamforming impossible with traditional passive antennas.
AAS Architecture
- Traditional: Radio at tower base, long feeder cable (2-3 dB loss at 2 GHz, 5+ dB at mmWave), passive antenna at top.
- RRH: Radio at tower top, short cable to passive antenna. Eliminated feeder loss. Standard for 4G.
- AAS: Radio integrated into antenna. No external cable. Each element has its own T/R chain. Enables digital beamforming.
5G Massive MIMO AAS
- 64T64R: 64 transceivers, 192 antenna elements (cross-pol dual-band). Standard for sub-6 GHz 5G.
- 32T32R: Cost-reduced variant for capacity-limited deployments.
- mmWave AAS: 256-1024 elements. Hybrid beamforming. Required for FR2 (28/39 GHz).
Frequently Asked Questions
What is an AAS?
An AAS integrates radio hardware directly into the antenna enclosure, eliminating feeder cables. In 5G, AAS units contain 64-256 elements with individual T/R chains for digital beamforming and Massive MIMO. The standard for 5G base stations.
Why is AAS better than traditional radio + antenna?
AAS eliminates 2-3 dB feeder cable loss (equivalent to doubling TX power for free), enables per-element beamforming (impossible with passive antenna), and reduces installation complexity (one unit instead of radio + cable + antenna).
What is 64T64R?
64T64R means 64 transmit and 64 receive chains. With dual-polarization and potentially dual-band elements, this translates to 192 physical antenna elements. This is the standard Massive MIMO configuration for sub-6 GHz 5G base stations.