Distributed antenna systems are used to extend public cellular wireless network coverage throughout large buildings.

DAS systems don’t generate signals; they capture signals from a source and distribute them within the building. The performance mainly depends on the type of technology employed.

They amplify the signal and extend its coverage throughout the area. Depending on your signal boosting needs, different types of DAS may be required.

Understanding the different types of distributed antenna systems and your coverage requirements is crucial to choosing the right solution. Let us dive deeper to understand the different types of DAS systems:

 

1. Passive DAS

Passive DAS uses components such as coaxial cables, couplers, and splitters. This system is mostly used in small and medium-sized buildings. It is easier to install and maintain. When designing a passive DAS, calculating link budgets is crucial to ensure the output power is equal at each antenna.

Pros
• Easier to maintain compared to other DAS systems.
• No need for additional expensive equipment for installation.

Cons
• Long cables can result in signal degradation.
• They produce weaker connections.

2. Active DAS

This system is typically used in large spaces and venues to capture and distribute signals. A series of antennas are deployed, making it complex. Advanced fiber optic technologies are employed to enhance the transportation of RF signals. Active DAS systems digitize the signal, which improves performance but also increases the overall cost.

The converted signals are transmitted over Ethernet or fiber optic cables to Remote Radio Units (RRUs). The RRUs convert the digital signals back to RF signals.

Pros
• Use of fiber and Ethernet cables ensures lower loss and better coverage.
• Better suited for large venues and buildings.

Cons
• More expensive than other DAS systems.

3. Hybrid DAS

Hybrid DAS is a combination of active and passive DAS, using both RRUs and coaxial cables. A typical hybrid DAS design/build includes an RRU on each floor to convert digital signals into analog RF signals. Coaxial cables are then used to connect the analog RF signal to antennas on the floor. Hybrid DAS systems are used in medium and large buildings for cellular or Public Safety Radio (PSR) applications.

Pros
• Hybrid DAS systems require fewer RRUs, making them cheaper compared to active DAS.
• Not limited by the lengths of coaxial cable runs.

Cons
• Due to the mix of fiber optic and coaxial cable, the installation process is complicated.

4. Digital DAS

Digital DAS is another type of hybrid distributed antenna system that converts analog signals into digital before transmitting them over fiber optic cables. Digital DAS is less susceptible to interference, but is also more costly than other types.

Pros
• Less susceptible to interference.
• Better performance.

Cons
• More expensive than analog systems.

 

Conclusion:

Whether a passive, active, or hybrid distributed antenna system is required depends on the specific application. Typically, an RF survey is conducted to determine which type of DAS design/build will be better suited for the application. When it comes to different DAS systems, coverage, capacity, and price are the key differentiators.