Passive Distributed Antenna Systems in 3G
Various internal antenna solution can meet the different needs of the deployment. DAS solution distributes a plurality of antenna nodes throughout the coverage area. Each antenna assembly can transmit and receive signals 3G. The uplink signals from all the antenna units are collected in a central point, the point of attachment to the wireless communication system. At the same time, the downlink signals from the radio are divided and distributed to each antenna assembly for transmission. In general, DAS, either passive or active.
DAS composed of carrier combiner, coaxial cables, bridges, power splitters, directional couplers, attenuators, terminators adapters / connectors and internal antennas. Combiner carriers normally used in general DAS, which is closed distribution system, which is common operator or different radio access technologies. Shared DAS is sometimes referred to as a neutral host system. Deployment and optimization of compounded with a neutral host system, because different radio technologies have different budgets Link. Thus, they can benefit from the various output and possibly different places antenna.
Optimization of one service can affect the performance of another service that also uses the system. Furthermore, maintaining acceptable performance of intermodulation various technologies may increase the cost DAS. On the other hand, sharing of DAS operators may reduce the capital cost of equipment and installation and maintenance.
If combiner carrier used is generally the first main component to be connected to a wireless communication system. It combines and separates the signals in both directions (downlink and uplink) in different frequency bands while preserving the required isolation high (typically> 70 dB) and low intermodulation (typically <-140 dB) between the various systems connected to different ports . Insertion loss is low, about 6 to 8 dB, depending on the number of system ports to adder multicarrier signal.
Coaxial cables connect radio systems and internal antennas distributed over several locations in the target building. In the passive systems, these coaxial cables are building to achieve internal antennas in different places. They should have a fire-resistant jackets, and if exposed to sunlight, UV radiation, as well as jackets. They must also comply with building regulations. It is important to choose the size of the coaxial cable of appropriate diameter to minimize losses and meet the design DAS losses. However we must ensure that the building of pipelines are large enough to accommodate that type of filing.
Passive power splitting device allows the radio signal to reach the antenna nodes in different places. Many passive power splitting devices exist, the specifications for different uses. Equal power splitting devices (duplex 3 dB tripartite: 4.8 dB; four directions: 6 dB, and so on) are usually called power dividers or partitions. In fact, these devices are somewhat higher insertion loss figures (further 0.1 to 0.5 dB) than the ideal splitting loss due to losses in the apparatus. In some cases, unequal division of power levels must balance the input power to different antennas are connected through feeders
This can be done using directional couplers which bind only a part of the power, and only in one direction of propagation. Unbalanced power splitters are also available, which send unequal amounts of energy in different parts of the building. For example, 60:30 power splitter sends the 1/3 power in one output port, and 2/3 of the capacity of the second output port. Combining splitters and couplers loss in the system can be arranged so that all the antennas have almost equal output Downlink Power levels. It becomes the criterion for making passive indoor DAS: specify the cable losses and coupler / splitter to distribute the energy loss for each antenna unit at the desired level.
If this is done, the antenna may be located at some distance from the Node B equipment. To start optimization, it must be confirmed that each internal antenna assembly generates said output DL, and not only to the antenna as well as the target coverage area, while the UE transmit power is within an allowable range. This dynamic range of over 70 dB in accordance with the standard. For a typical class 3 UE, the transmission power will be from -46 dBm to +24 dBm. If conditions require UE RF control below the latter condition, the UE is not properly controlled power and will generate UL interference.