※The image is for illustration purposes.

Introduction

The 5G network, often referred to as the cornerstone of next-generation communication, demands exceptional quality and reliability. Behind the scenes, a critical component supporting these requirements is the OCXO (Oven Controlled Crystal Oscillator). In this article, we explore the role and importance of OCXOs in 5G base stations, as well as key considerations when selecting one.

Communication Base Stations and Frequency Stability

Mobile phones and IoT devices communicate using radio waves.

These waves have frequencies. In the case of 5G, higher frequencies such as sub-6 GHz and millimeter wave bands are used. Because frequency directly impacts communication stability and speed, extremely precise control is required.

Base stations handle high-frequency signals and must transmit and receive data with accurate timing. As a result, the precision of the internal clock greatly affects communication performance. Crystal oscillators play a key role in this process, and OCXOs (Oven Controlled Crystal Oscillators), known for their high frequency stability, are often adopted.

What is an OCXO?

OCXO stands for "Oven Controlled Crystal Oscillator". It is a type of oscillator that achieves extremely high frequency stability by maintaining the crystal unit in a constant and controlled environment.

Compared to general crystal oscillators such as SPXO and TCXO, OCXOs are much less affected by external environmental changes and temperature variations. This allows them to maintain precise signal accuracy over long periods of time.

 In the OCXO, there is a compact temperature-controlled chamber equipped with a heater, which keeps the crystal unit at a constant temperature at all times. As a result, even under fluctuating ambient temperatures, OCXOs provide exceptionally stable frequency performance.

Why Are OCXOs Essential in Base Stations?

In communication base stations, network-wide time and frequency synchronization is essential. For example, the following situations require the performance characteristics of OCXOs:

1. Requirement of Phase Noise Characteristics：To ensure the accurate transmission of large volumes of data, especially in high-frequency modulation, signal purity is critical. Therefore, low jitter and low phase noise performance are essential.
2. GNSS (Global Navigation Satellite System for holdover performance during signal loss)：OCXO supports network stability by autonomously maintaining high precise clock, even under the condition of GNSS signal loss .
3. Synchronization Between Base Stations (TDD Method)：In the TDD method which transmit and receive data alternately, a highly accurate reference clock is required to prevent communication errors caused by timing mismatches between base stations. 

Key Points for selecting an OCXO

For 5G base station application, the following key points are important when selecting an OCXO.

1. Phase noise：It is important to reduce the phase noise, which tends to affect high-speed communication.
2. Frequency Stability in Terms of Temperature Variations and Long-Term Performance：High frequency stability that matches the system requirements is essential.
3. Compact size and low power consumption：More compact and low-power OCXOs are required to meet the trend toward smaller equipment in 5G base stations.

Introduction of NDK Crystal Oscillators Optimized for 5G Base Stations

We have developed two high-precision OCXOs (Oven Controlled Crystal Oscillators), the NH7050XA and NH9070XB, which are among the smallest in the world※1.

Their key features are outlined below. For further detail, please refer to the press release titled:
" Development of the World's Smallest Class OCXO for 5G Base Stations and Data Centers, with +105°C Support : NH7050XA and NH9070XB."
※1.　Based on our internal research as of February 2025.

Product features

・Compact size（7.2ｘ5.3ｘ3.3mm、9.5ｘ7.3ｘ4.1mm）
・Low phase noice
・High-temperature support up to +105°C

Applications・Markets

・5G Radio Unit

・Small Cell

・SyncE and IEEE1588

・Switch and Router

・SONET, OTN, Stratum3

・AI Server, Time Card

Sample・Mass Production Schedule

・Sample available
・Mass Production Schedule：Expected in July, 2025

In Conclusion

The OCXO used in 5G base stations is not merely a "crystal oscillator", but a core component that quietly supports overall network stability and communication quality behind the scenes. As modern communication infrastructure continues to demand ever-higher frequency accuracy and reliability, the importance of OCXO is expected to grow further in the years ahead.

Contact Information

Inquiry related to our product

Inquiry related to our product　TEL : 03-5453-6723

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Inquiry related to IR　TEL : 03-5453-6702

E-Mail：newsrelease@ndk.com