rf circulator

rf circulator

About 70 – 80% of mobile traffic from inside buildings. This is particularly true in urban settings where the focus is on Mobile User types high data. 3G mobile network for serving only the macro base station a few hundred yards from the building can provide enough RF signal to maintain the inner voice and data. In Realty, only a few buildings fall into this category. Soft handover in the 3G network will further increase the traffic load on the network because each mobile phone can be repaired by more than one macro-cells (base stations). To provide high speed within the mobile data services such as HSPA (High Speed Packet Access) and EVDO (Evolution – Data Optimized) services, the only solution is an indoor distributed antenna systems (DAS).

DAS is used to distribute the RF signal uniformly strong enough within a building to provide 3G voice and data. DAS can be used to isolate the internal network of cells used in outdoor macro to eliminate smooth delivery of mobile movement inside. This will reduce the traffic load and increase the speed of the 3G network. For the HSPA high speed data service within the DAS can also provide isolation between active and cells do not serve in external network. This means less co-channel interference HSPA used in the cell and result in higher transmission speeds of HSPA. To master the building with an indoor coverage, directional antennas can be deployed on the front and corners of the building and pointing toward the center of the building. The total area covered is dominated by the cell inside and at the same time, minimize leakage in the macro network.

DAS distributes a uniform dominant RF signal inside the building by dividing the signal base station within several antennas inside to ensure coverage throughout the building. DAS can be classified as passive or active. Passive DAS uses passive components for RF signal distribution. These passive components are coaxial cable, splitters, terminators, attenuators, circulators, couplers and filters (printing on both face, diplexer and Triplexer). Planning DAS includes the calculation of the maximum loss for each base station antenna system and link budget for the region, especially that each antenna covers. The design is passive DAS adapt to the restrictions on construction restricting where and how heavy coaxial cable can be installed. A survey on-site construction of retail to be done to ensure the availability of cable channels for all antennas.

Active DAS has the ability to automatically compensate for the losses of the cables interconnecting the components in the system using the internal calibration signals and amplifiers. Few regardless of the distance between the antenna and base station, all the antennas in an active DAS will have the same performance (noise figure and power same downlink). DAS assets consist of a central unit (MU) connected to multiple expansion units (EU) with optical fiber up to 6 km long. Each in his own time, the EU is connected to several remote control units (RU) with coaxial cable or CAT5 cable up to 400 meters long. The MU controls and monitors the performance of the DAS. ENI are distributed throughout the building and EF have been installed near the antenna. The active DAS can provide broadband services multiple radio, GSM, PCS, UMTS, EVDO, WiFi and WiMax.

Because of the loss and mitigation in the coaxial cable and passive components, passive DAS is only used in the construction of small antennas inside covers some to keep the degrading effect on the minimum performance HSPA. To expand the building, the active DAS is used because it has no component cable loss and improves performance up to HSPA. Solve problems related to passive DAS is difficult, and any failure in the system does not raise the alarm to the base station, because there is no error handling in the system. Active DAS monitors all units of the system and in case of malfunction, an alarm is sent to the base station that allows the operator to identify the source of the problem. Therefore, Active DAS is the preferred solution for a large building with lots of indoor antennas.

About the Author:

Paul Ngai is an engineering consultant specialized in Telecommunications Network and Systems. He is also the principal of Network Systems Technologies LLC, a telecommunications consulting firm provides planning, analysis, design, testing and operation support services.

Article Source: ArticlesBase.com – Distributed Antenna Systems for Indoor Cellular Network