5G millimeter wave radio: from trials to commercial reality

FWA suburban Fixed wireless access – base station on pole/tower, outdoor CPE. High EIRP (>65 dBm) to extend range. NLOS path loss ~135 dB at 200m range. 256 elements at gNB, 64 at CPE support 64 QAM downlink and 16 QAM uplink.

Dense urban Street-level small cells – mounted on building facades or lampposts. Needs vertical scanning, lower EIRP (50-60 dBm) but higher beam steering flexibility. Outdoor-to-indoor penetration remains challenging (low‑E glass).

Key takeaway: deployment scenario drives beamforming architecture, and architecture defines RF technology choice.

Analog beamforming – single RF path, phase shifters, one beam per user. Simple but limited flexibility.
Digital beamforming – maximum capacity and multi-user MIMO, but high DC power and complexity at mmWave.
Hybrid beamforming (most practical today) – combines digital pre‑coding with analog phase shifting. Supports 2 to 8 digital streams. Enables spatial multiplexing, beam reuse, and efficient use of spectrum. Sub‑array based hybrid beamforming is the preferred implementation for 5G mmWave base stations.

5G mmWave requires 1 GHz+ channel bandwidth and supports 64 QAM (256 QAM in future). Low phase noise and excellent EVM are mandatory. The following proven signal chain handles 8x100 MHz NR carriers at 28 GHz with outstanding performance.

Required EIRP determines antenna size and semiconductor technology. For 60 dBm EIRP (typical FWA), optimum array size is 128–256 elements. Lower element count uses GaAs power amplifiers; higher element count enables fully integrated silicon beamforming (SiGe BiCMOS or RF SOI).

• Handsets / UE: CMOS integration, low element count, power efficient.
• Small cells & CPE: SiGe BiCMOS offers best balance between output power and integration.
• Wide area macro cells: GaAs or GaN for highest power, though advanced SiGe can reach 60 dBm EIRP with larger arrays.

Industry continues to improve PA efficiency, enabling higher integration for high-power mmWave radios.

Modern mmWave base stations reuse the same bits-to-mmWave radio with different beamforming front-ends. The analog or hybrid beamforming section (phase shifters, PAs, LNAs) can be customized for coverage and power: from fully integrated silicon for compact cells to high-power GaAs front‑ends for wide area. The core wideband transceiver stays consistent, reducing development risk and time‑to‑market.

• ✔ 5G mmWave is moving from field trials to first commercial deployments (FWA and urban cells).
• ✔ No single architecture fits all – hybrid beamforming provides the best balance of performance, cost, and power.
• ✔ Wideband bits-to-mmWave radios now support 1 GHz+ bandwidth and 64 QAM using advanced silicon data converters and up/down converters.
• ✔ Frequency synthesis with ultra-low phase noise is critical for high-order modulation and low EVM.
• ✔ Reusing the same radio with scalable front‑ends (128–256 elements, Si or III-V) allows operators to address multiple deployment scenarios.