Introduction
5G commercial deployment is accelerating globally. As a new generation of mobile communication technology, 5G, with its characteristics of high speed, low latency, and massive connectivity, is profoundly changing all aspects of the social economy. The large-scale construction of 5G networks has driven the comprehensive development of the communication industry chain. RF connectors, as indispensable key components in base station systems, have also ushered in new market opportunities and technical challenges. Starting from the changes in 5G base station architecture, this article provides an in-depth analysis of the demand characteristics, technical requirements, and market development trends of RF connectors for 5G communication base stations.
1. 5G Base Station Architecture Evolution and Connection Demand Changes
Compared with 4G, 5G base stations have undergone significant architectural changes, which directly affect the demand pattern and technical requirements of RF connectors.
From 4G to 5G: Three Major Changes in Base Station Architecture
1. Active Antenna Unit (AAU) Becoming Mainstream
Base stations in the 4G era mainly adopted a distributed architecture, consisting of BBU (Baseband Processing Unit) + RRU (Remote Radio Unit) + antenna, with RRU and antenna connected via feeder cables. In the 5G era, to support Massive MIMO (Multiple-Input Multiple-Output), the RRU and antenna are integrated into an Active Antenna Unit (AAU), with the RF front-end and antenna highly integrated.
This change reduces the demand for traditional long-distance high-power RF feeder cables, but significantly increases the number of RF connection points inside the AAU. With hundreds of channels in large-scale array antennas, each channel requires RF connectors to connect power amplifiers, filters, phase shifters, and other devices, significantly increasing the per-unit usage of RF connectors.
2. Baseband Unit Split and Centralization
5G splits the original BBU into CU (Centralized Unit) and DU (Distributed Unit). The CU processes non-real-time high-layer protocols, while the DU handles physical layer and real-time functions. The CU can be deployed centrally, with multiple base stations sharing one CU, thereby improving resource utilization. At the same time, the DU and AAU are connected via the eCPRI interface, using optical fiber transmission to replace some traditional RF connections.
Architectural changes have made the types of connections between and within base stations more diverse, including both traditional RF connectors and high-speed optical and data connections.
3. Frequency Band Diversification and Antenna Miniaturization
The frequency bands used by 5G are richer, including Sub-6GHz mid-low frequency bands and mmWave (millimeter wave) high-frequency bands. Different frequency bands have very different performance requirements for RF connectors. Meanwhile, 5G base station forms are more diverse, from traditional macro base stations to small base stations, pico base stations, and indoor distribution systems, with varying requirements for connector size and power.
Changes in RF Connector Usage in 5G Base Stations
The impact of changes in 5G base station architecture on RF connector usage is two-way:
Reduced Part: The number of main feeder cables from RRU to antenna is greatly reduced, and the usage of traditional 7/8-inch and 1/2-inch feeder connectors has declined. Optical fiber transmission has replaced some RF coaxial connections.
Increased Part: Massive MIMO technology increases the number of channels from 4 channels and 8 channels to 32 channels, 64 channels or even more. Each channel requires RF connections, and the usage of RF connectors inside the AAU multiplies. In addition, the dense deployment of small base stations also brings a large demand for connectors.
Overall, both the per-unit usage and total market size of RF connectors are growing in the 5G era, but the product structure has changed, with faster growth in demand for low-power, miniaturized, multi-channel RF connectors.
2. Main Types and Applications of RF Connectors in 5G Base Stations
There are many types of RF connectors used in 5G base stations. According to different application positions and functions, they can be divided into the following major categories:
Base Station Antenna-Feed Side Connectors
Antenna-feed side connectors are mainly used for RF signal connection of antenna systems and are one of the most used RF connectors in 5G base stations.
- DIN Type Connectors (7/16-inch): High-power RF connections between large base station equipment, such as connections between RRU/AAU and main feeder cables. Characterized by large power capacity and high reliability, mainly used in low-frequency bands and large macro base stations. Still widely used in 5G mid-low frequency macro stations.
- N-Type Connectors: Medium-power applications, commonly used in test instruments, base station equipment, etc. Power capacity and size are between DIN type and SMA.
- SMA Connectors: Small screw-type RF connectors and the most commonly used RF connector type inside 5G base stations. SMA connectors are heavily used for connections between power amplifiers, filters, and antenna arrays inside AAUs. SMA has small size, reliable performance, and applicable frequencies up to 18GHz or higher.
- SMB/SMC Connectors: Push-on or screw-type connectors smaller than SMA, used in space-constrained situations.
- 4.3-10 Connectors: An emerging low-PIM connector in recent years, more compact and lightweight compared to traditional 7/16 DIN type, while having excellent passive intermodulation (PIM) performance. Increasingly used in 5G base stations, especially in tower-top and AAU connection scenarios.
Board-Level RF Connectors
Board-level RF connectors are used for RF signal transmission and connection on PCB boards and are important components inside AAUs.
- Board-End SMA/MMCX: RF connectors soldered on PCB boards, used for board-to-board or board-to-cable RF connections.
- Board-to-Board RF Connectors: Directly connect RF signals on two PCB boards without cables, with compact structure and low loss. Heavily used in highly integrated AAUs.
- RF Coaxial Switch Connectors: Used for RF signal switching and testing.
High-Speed Digital Connectors
In addition to RF signals, 5G base stations also need to transmit a large number of high-speed digital signals:
- SFP/SFP+ Connectors: Used for access of optical fiber modules, standard optical interfaces between base stations and transmission networks, and between CU and DU.
- QSFP+/QSFP28 Connectors: Higher density optical module interfaces for high-speed data transmission.
- High-Speed Backplane Connectors: High-speed signal connections between boards inside BBU/DU equipment.
3. Elevated Technical Requirements for RF Connectors in 5G Era
RF signals in the 5G era have characteristics such as higher frequency, wider bandwidth, more channels, and higher integration, putting forward higher requirements for RF connector performance.
Operating Frequency Range Expansion
5G includes not only Sub-6GHz mid-low frequency bands but also mmWave frequency bands above 24GHz. The increase in operating frequency puts forward higher requirements for RF connector design:
- High-Frequency Performance Optimization: In the mmWave frequency band, any minor structural discontinuity in the connector can cause severe signal reflection and loss. The dimensional accuracy, material selection, and impedance control of connectors need to reach higher levels.
- Low Loss Requirements: High-frequency signals inherently have high loss, and the insertion loss of connectors must be strictly controlled to ensure overall system performance. Low-loss dielectric materials and precision structural design are key.
- Miniaturization Trend: Higher frequencies mean shorter wavelengths, and connector sizes can be made smaller, but machining precision requirements are also higher.
Bandwidth and Signal Integrity
The bandwidth of 5G signals has greatly increased, with single-carrier bandwidth rising from 20MHz in the 4G era to 100MHz or even higher, requiring RF connectors to maintain consistent performance over a wider frequency range:
- Wide Band Design: Connectors need to maintain good VSWR and insertion loss characteristics over a wide frequency range.
- Phase Consistency: Massive MIMO systems have very high requirements for phase consistency between channels, and the phase deviation of the same batch of connectors must be controlled within a very small range.
- Low Passive Intermodulation (PIM): 5G systems are very sensitive to PIM, especially in TDD systems and large-scale antenna arrays. The PIM performance of connectors directly affects the receiving sensitivity of the system. The design and manufacturing of low-PIM connectors require special process control, including material selection, contact structure design, surface treatment, etc.
Integration and Density Enhancement
Inside 5G AAUs, dozens or even hundreds of channels are integrated, and the installation density of RF connectors is greatly increased:
- Miniaturization: Installing more connectors in limited space requires smaller connector volumes. Usage of small connectors such as SMP and MMCX increases.
- High-Density Arrangement: When multiple connectors are arranged in rows or matrices, the problems of electromagnetic interference and coupling between each other become more prominent, requiring careful design of shielding structures.
- Weight Control: AAUs are installed on towers, and weight is an important design constraint. Connectors need to be as lightweight as possible while ensuring performance.
Environmental Adaptability and Reliability
5G base station equipment is exposed to outdoor environments for long periods, imposing extremely high requirements on the environmental adaptability of connectors:
- Wide Temperature Operation: From -40C to +85C or even higher temperatures, connectors need to maintain stable performance.
- Waterproof and Dustproof: Outdoor base station connectors usually need to reach IP65, IP67 or higher protection ratings.
- Corrosion Resistance: Connectors need to withstand outdoor salt spray, moisture, and other corrosive environments, with high requirements for plating and shell materials.
- Anti-Vibration and Anti-Shock: Antennas installed on towers must withstand wind load vibration and accidental impacts.
4. Competitive Landscape and Domestic Replacement Progress
International Major Players
High-end RF connector technology has long been dominated by European, American, and Japanese manufacturers:
- United States: Amphenol, TE Connectivity, Molex, etc., with strong technical strength and complete product lines, occupy a dominant position in the global high-end RF connector market.
- Germany: Rosenberger and others, enjoying high reputation in communication testing and high-end RF connection fields.
- Japan: Hirose, JAE, etc., with strong capabilities in small precision RF connectors.
Domestic Replacement Progress
In recent years, domestic RF connector manufacturers have developed rapidly, and the domestic replacement process has been accelerating:
- Basically Achieved Domestic Replacement in Mid-to-Low-End Market: In mature product fields such as SMA and N-type, domestic manufacturers already have strong competitiveness. Product quality and reliability can fully meet market demand, with obvious cost advantages.
- Accelerated Breakthrough in Mid-to-High-End Market: In mid-to-high-end product fields such as 4.3-10, low-PIM connectors, and board-to-board RF connectors, leading domestic enterprises have achieved technological breakthroughs and gradually entered the supply chain of mainstream equipment vendors.
- Layout in Cutting-Edge Fields such as mmWave: Targeting 5G mmWave and future 6G technology, domestic manufacturers are also actively deploying and developing high-frequency high-performance RF connector products.
- Policy Support and Industrial Chain Collaboration: The country’s strong support for new infrastructure such as 5G and the rise of domestic communication equipment manufacturers have provided good development opportunities for domestic RF connectors. Collaborative innovation across the industrial chain is also continuously strengthening.
5. Future Development Trends
Looking at the future development of 5G RF connectors, the following trends are noteworthy:
- Higher Frequencies: With the deployment of 5G mmWave and future 6G technology R&D, the operating frequency of RF connectors will develop toward higher directions, posing new challenges to design and manufacturing processes.
- Higher Integration: RF connectors will be further integrated with other components, such as connectors with integrated filtering functions, multi-channel integrated connectors, etc., reducing system volume and cost.
- Fiber Replacing Copper Continues: In long-distance and high-speed transmission fields, optical fiber connections will continue to replace coaxial connections, and RF connectors will be more concentrated in equipment internal and short-distance connections.
- Intelligent and Digital: Smart connectors with identification and status monitoring functions may appear, providing more data support for base station operation and maintenance.
- Green Energy Saving: Low-loss, high-efficiency RF connectors help reduce base station energy consumption, in line with the development direction of green communication.
Conclusion
The large-scale construction of 5G networks has brought huge development opportunities to the RF connector market, while also putting forward higher technical requirements. From multi-channel connections in Massive MIMO to high-frequency challenges of mmWave, from low-PIM performance to harsh environmental adaptability requirements, 5G RF connectors are evolving toward high performance, miniaturization, high density, and high reliability.
RXSY closely follows the development of 5G communication technology, actively deploying RF connector and communication equipment connector product lines, committed to providing high-quality, cost-effective domestic connection solutions for the communication industry. For more information on communication equipment connector products, please refer to the RXSY product series. We will continue to invest in technology R&D to help the development of China’s communication industry.
