Overview
5G networks demand phase-aligned, low-jitter timing across distributed radio units. Precision oscillators—primarily TCXO and OCXO—stabilize local PLLs, maintain clock integrity under temperature and load transients, and provide holdover when GNSS is unavailable. These requirements mirror timing challenges in adjacent domains like Industrial Automation & Robotics and Test & Measurement Equipment, and rely on GNSS-centric practices captured in our TCXO for GNSS Applications.
5G Timing Requirements
- Time Accuracy (TAE) @ air interface: ±1.5 μs (typical for TDD alignment)
- Short-term jitter (SyncE/EEC context): < 50 ps
- Frequency stability for holdover: ±5–20 ppb over temperature, aging < 1 ppb/day
- Phase noise (RF LO chain reference): < −150 dBc/Hz @ 10 kHz offset (application-dependent)
Common references: 10 MHz OCXO (GPSDO/SyncE), 19.44/25/50/100/125 MHz SyncE/Ethernet, 30.72/61.44/122.88 MHz radio basebands; metrics incl. MTIE/TDEV (wander) and ITU-T G.8273.2 (telecom boundary clocks).
See also: Industrial Automation Timing · Test & Measurement Timing · GNSS TCXO Guide
Oscillator Selection & KPIs
| Class | Typical Stability | Phase Noise (example) | Power / Size | Where It Fits |
|---|---|---|---|---|
| TCXO | ±0.1–0.5 ppm | ≈ −150 dBc/Hz @ 10 kHz | Very low / miniature | Small cells, RRH with GNSS/1588 present, short holdover |
| OCXO (FOC Series) | ±5–20 ppb | ≈ −160 dBc/Hz @ 100 Hz | Higher / ovenized | gNodeB baseband, microwave backhaul, SDH/SONET timing |
| PRTC / Atomic (external) | ±1 ppb (source) | N/A | External reference | Primary reference time clocks, network grandmasters |
Not sure whether to choose TCXO or OCXO? Read: TCXO vs OCXO — Timing Comparison.
System Clock Architecture
Typical chain: GPSDO → jitter-cleaning PLL → local OCXO/TCXO holdover → IEEE 1588v2 PTP / SyncE (ITU-T G.8262) distribution. Robust designs partition clock domains, constrain wander at boundary/transparent clocks, and budget TIE to meet end-to-end alignment.
CPRI/eCPRI Fronthaul
Fronthaul links depend on clean reference clocks for EVM budgets in higher-order modulation (e.g., 256-QAM). A low-jitter TCXO module works when GNSS/PTP are available; an OCXO for base stations extends holdover, smoothing temperature swings and supply ripple.
Recommended Models
TCXO — Low Jitter, Compact, Wide Temperature
- FVT-9S-LN — Low-phase-noise TCXO; typical stability ±0.5–1.0 ppm; sub-ps to few-ps RMS jitter (band-limited). Ideal for eCPRI radios/small cells with continuous PTP/GNSS. When to prefer TCXO vs OCXO.
- FVT-3S — 3.2×2.5 mm miniature TCXO; stability up to ±0.5 ppm; low power and fast start for compact RRH modules.
- FVT-5S — Ultra-low-power TCXO; ±1.0 ppm (typ. options); wide voltage range for power-sensitive radios.
OCXO — Holdover, Low ADEV, Ovenized Stability
- FOC Series (10 MHz) — SC-cut OCXO family with typical ±5–20 ppb stability, excellent retrace/warm-up and low Allan deviation; suited for gNodeB baseband, microwave backhaul, and SyncE EEC/SSU roles.
- FOC Miniature — Compact OCXO variants where board height and power are constrained yet ppb-class holdover is required.
VCXO — Tunability (EFC) for Alignment & Agile Synthesis
- VCXO Lineup — Pull ranges (e.g., ±25/±50 ppm options), optimized EFC sensitivity and linearity for calibration or frequency alignment in PLL chains while maintaining low residual phase noise.
Need PN→jitter integration, ADEV plots, or EFC/tuning specs for GPSDO/holdover? Contact our engineers.
Technical FAQ
- How much holdover is practical without GNSS?
- Designs commonly target ±5–20 ppb over temperature with aging < 1 ppb/day using an OCXO, sustaining minutes to hours of acceptable phase alignment depending on profile.
- Where is TCXO preferred over OCXO?
- In power-sensitive radios or compact small cells with continuous PTP/GNSS availability and short holdover expectations.
- Which metric best predicts RF performance?
- Close-in phase noise near carrier strongly correlates with EVM and adjacent-channel leakage; select references with low close-in noise and adequate spur suppression.
Authoritative References
Explore more: Timing Devices · FVT-9S-LN · OCXO Series
5G fronthaul/backhaul clocks hinge on phase noise — see the XTAL phase-noise & jitter guide
