With the rapid deployment of 5G in indoor environments, Distributed Antenna Systems (DAS) have become a critical solution to ensure reliable signal coverage. Although passive RF components in DAS are non-powered, their performance directly affects signal transmission quality and overall system stability. Selecting and optimizing these passive components is key to enhancing indoor 5G network coverage.

This article shares practical insights and key optimization points for passive components in 5G DAS, helping equipment manufacturers and integrators address common coverage and signal quality challenges.

1. Minimize Insertion Loss to Ensure Sufficient Signal Power

In DAS systems, signals pass through multiple passive components for distribution and transmission, each introducing some insertion loss. Accumulated losses reduce the signal power at the antenna, shrinking coverage area and causing signal dead zones.

Recommendations:

• Choose passive components such as power splitters and combiners with low insertion loss, especially for higher frequency bands (3.5 GHz and above);

• Prefer components made from high-quality copper and precision manufacturing to avoid extra losses caused by poor materials or workmanship;

• Plan distribution branches carefully to avoid unnecessary multi-stage splitting, which adds to signal loss.

2. Ensure Strict Impedance Matching to Reduce Reflections and Interference

Impedance mismatch causes signal reflections, increasing Voltage Standing Wave Ratio (VSWR), leading to wasted signal energy and unstable system performance.

Recommendations:

• All passive components should be designed to standard 50 Ω impedance;

• Use a network analyzer during installation to verify VSWR at each node is below 1.5;

• Employ adjustable components if needed for fine impedance tuning, ensuring consistent signal flow.

3. Improve Isolation to Prevent Signal Crosstalk and Intermodulation

5G networks often run multiple frequency bands concurrently, making signal intermodulation interference more sensitive. Passive components with poor isolation allow adjacent signals to interfere, degrading user experience.

Recommendations:

• Select components such as power splitters and couplers with isolation ≥ 30 dB to minimize interference between signal paths;

• Carefully plan frequency bands and component placement to avoid co-channel interference and excessive coupling;

• Use combined devices with built-in filtering capabilities in critical links to enhance signal purity.

4. Use Attenuators Judiciously to Achieve Balanced Coverage

Indoor environments are complex, and uneven antenna distribution often causes hotspots or weak coverage areas.

Recommendations:

• Deploy variable attenuators to adjust signal power in different branches according to need, achieving balanced coverage;

• Regularly measure signal power distribution and dynamically adjust attenuator settings;

• Choose attenuators with good linearity and wide frequency coverage to avoid degrading signal quality.

5. Select High-Quality Connectors and Cables for Stable Transmission

Connectors and RF cables are critical links in the signal chain; poor quality or improper installation leads to additional losses and potential failures.

Recommendations:

• Use low-loss, impedance-stable connectors like SMA or N-type that meet 5G frequency band requirements;

• Select low-loss coaxial cables suitable for the target frequency range;

• Pay attention to proper connector tightening and strain relief during installation to prevent performance degradation from mechanical stress or environmental factors.

6. Conduct Regular Maintenance and Testing to Prevent Failures

Passive components may degrade over time due to environmental factors or aging, impacting overall system performance.

Recommendations:

• Perform routine testing of key nodes with RF test equipment (e.g., network analyzers) to check insertion loss, isolation, and VSWR;

• Replace or repair components showing abnormal loss or reduced isolation promptly;

• Keep detailed maintenance records to track device lifespan and avoid unexpected failures.