Smart Antenna

Topics: Smart antenna, Phased array, Radio frequency antenna types Pages: 5 (1587 words) Published: May 7, 2013
Smart Antennas
A Smart Antenna is an antenna system which dynamically reacts to its environment to provide better signals and frequency usage for wireless communications. There are a variety of smart antennas which utilize different methods to provide improvements in various wireless applications. This report aims to explain the main types of smart antennas and there advantages and disadvantages. Smart Antennas

Contrary to the name smart antennas consist of more than an antenna. A smart antenna is a system involving multiple antenna elements and a signal processor (Usually digital) to adjust the radiation and or elements of the antenna (IEC 2004). Smart antennas usually use arrays of antennas linked to a control unit or digital signal processor (Lehne et al. 1999, p. 4). Current efforts into smart antenna development are for wireless digital networks, for use with mobile telephones and computer networks. The smart antennas developed for mobile telephone networks are focused on replacing standard base station antennas to communicate with standard antenna mobile phones, however in the future mobile phone handsets may also contain smart antennas. [pic]

Fig 1 Smart Antenna System
The theory behind smart antennas has been around for some time. The technique of two parties ‘targeting’ each other with there transmissions being used in world war II to prevent jamming and eavesdropping form third parties. However smart antennas have recently become a viable option for large digital networks as computer processors now have sufficient computational power to process wireless signals in real time. (004p3) Conveniently the emergence of powerful enough processors has also coincided with the need by communications carriers to be able to use their frequency space more efficiently. As the frequency space is limited and expensive to purchase carriers needed a way to support more users within the same frequency space. Smart antennas work on the premise that interferes (devices which are also transmitting on the same frequency) are rarely in the same physical location as another device. Smart antennas exploit this by targeting antenna gain (sensitivity) in the direction individual devices (004p3). This means that signals from interferers are not received or much weaker than the signal we are transmitting and receiving with the desired device. Targeting devices also reduces the interference radiated to other devices, this means that other devices can use the same frequency. Having more than one set of devices using a frequency means that the capacity of the frequency space is effectively increased. A smart antenna is similar in function to a switch on a traditional wired computer network, sending signals only to the intended recipients. [pic]

Fig 2 Device with interfering device
There are several advantages and disadvantages to the use of smart antennas, which have been expanded upon below. Advantages
Increased number of users
Due to the targeted nature of smart antennas frequencies can be reused allowing an increased number of users. More users on the same frequency space means that the network provider has lower operating costs in terms of purchasing frequency space.(Lehne et al. 1999, p. 5),(SYMENA 2004, p. 5) Increased Range

As the smart antenna focuses gain on the communicating device, the range of operation increases. This allows the area serviced by a smart antenna to increase. This can provide a cost saving to network providers as they will not require as many antennas/base stations to provide coverage.(Lehne et al. 1999, p. 5) Geographic Information

As smart antennas use ‘targeted’ signals the direction in which the antenna is transmitting and the gain required to communicate with a device can be used to determine the location of a device relatively accurately. This allows network providers to offer new services to devices. Some services include, guiding emergency services to your location, location based games...
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