4 Types of Distributed Antenna Systems – Active, Passive, Hybrid & Digital
Distributed antenna systems are used to extend public cellular wireless network coverage throughout a large area of building.
DAS systems don’t generate signal; they capture the signal from somewhere and distribute it throughout the building. The performance depends mainly on the type of technology employed.
They amplify the signal and extend its coverage to distribute it throughout the area. Depending on your signal boosting needs, you may need different types of DAS.
Understanding different types of distributed antenna systems and your coverage requirements is important to choose 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 calculation of link budgets plays a pivotal role to ensure the output power is equal at each antenna.
• Easier to maintain compared to other DAS systems.
• No need for extra expensive equipment for installation.
• Long cables can result in breakdowns.
• They produce weaker connections.
2. Active DAS
This system is usually used in larges spaces and venues to capture and distribute signals. A series of antennas are deployed which makes it complex. Advanced fiber optic technologies are employed to enhance the transportation of RF signals. Active DAS systems digitize the signal which improves the performance but also adds to the overall cost.
The converted signals are transmitted over ethernet or fiber optic cables to RRUs (remote radio units). The RRUs convert the digital signals back to RF signal.
• Uses of fiber and ethernet cables ensures lower loss and better coverage.
• Better suited for large venues and buildings
• Active DAS is more expensive
3. Hybrid DAS
It 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 signal into analog RF signal. 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 PSR applications.
• Hybrid DAS system require fewer RRUs which make them cheaper compared to active DAS
• They are not limited by the lengths of coaxial cable runs.
• Due to the mix of fiber optic and coaxial cable, the installation process is complicated.
4. Digital DAS
It is another type of hybrid Distributed Antenna Systems, that converts analog signals into digital before transmitting over fiber optic cable. Digital DAS is less susceptible to interference. But they are also more costly than other types.
• Less susceptible to interference.
• Better performance.
• More expensive than analog systems.
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.