5G NR defines two frequency ranges in 3GPP specifications: FR1 (sub-7 GHz in current releases) and FR2 (millimeter-wave bands, starting around 24 GHz). The RF front-end implications differ significantly.

FR1
- Conventional architectures: discrete or module-based PAs, LNAs, filters and switches per band.
- Filters (SAW, BAW) are critical due to dense band allocations and carrier aggregation.
- Massive MIMO base stations use many transceiver chains, typically with digital beamforming.
- Conducted RF requirements (power, ACLR, EVM, sensitivity) are tested at antenna connectors for many equipment classes.

FR2
- High path loss per antenna element and blockage drive the use of antenna arrays with beam steering.
- Hybrid or analog beamforming: phase shifters and gain control per element, integrated in beamformer ICs close to the antenna.
- Antenna-in-package (AiP) and antenna-on-board solutions because routing mmWave signals is lossy.
- Requirements are radiated: test is over-the-air (OTA) using metrics such as EIRP and EIS, often measured in compact antenna test ranges.
- Thermal design matters: many elements in a small area.

Common to both
- High PAPR OFDM waveforms push PA back-off, so efficiency enhancement and DPD remain important.
- Phase noise has a stronger impact at FR2 carrier frequencies, which is one reason NR includes phase-tracking reference signals (PT-RS).
- Wider channel bandwidths increase the demands on converters and linearization bandwidth.

Recommended references: the 3GPP TS 38.101 (UE) and TS 38.104 (base station) series define bands and RF requirements. Read the current release since band lists and limits evolve.