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Smart Antenna array selection
Jul 05, 2017

Adaptive antenna is the main type of smart antenna, you can achieve omni-directional antenna, you can also achieve directional antenna, the completion of a variety of environmental conditions, the user signal reception and transmission.

The array elements are linear, flat, ring and three-dimensional. Three-dimensional antenna array due to the complexity and accuracy of calibration and deployment of more difficult, so less practical occasions. In general, linear and planar are more likely to achieve directional coverage of the base station. Moreover, the base station location problems are more flexible, linear and planar antenna array can be easily placed in the side of tall buildings, can also be placed in rod-like buildings such as poles. The ring antenna array is more suitable for placement in the tower or the top of the building, so more convenient to provide omnidirectional coverage. It should be noted that the ring antenna array antenna calibration difficulty than the linear and flat type to be large.

W-CDMA and CDMA2000 and TD-SCDMA systems can be used in the above-mentioned different occasions, linear, flat, ring antenna array. In October 2001 held in Beijing International Wireless Communications Exhibition, Datang Telecom exhibited TD-SCDMA base station is used in circular antenna.

The adaptive array antenna generally adopts 4 ~ 16 antenna array element structure. In the FDD, if the array spacing is too large, if the element spacing is too large, the degree of correlation of the received signals decreases, too small will form unnecessary in the pattern Of the grating, it is generally taken half-wavelength. In the TDD, such as the United States ArrayComm company in the PHS system adaptive array antenna array spacing of 5 wavelengths. Wide pitch and narrow beam, and PHS system using TDD mode, which is easier to locate processing. But because of the narrow characteristics of the beam, the current adaptive array antenna in TDD technology, such as PHS and ArrayComm company launched I-BURST wireless Data technology has been able to achieve space division multiple access SDMA technology.

W-CDMA and CDMA2000 base stations, an antenna of 4 antennas, 8 antennas and even 12 antennas may be used. The greater the number of antenna elements, the higher the system gain. Assuming that the number of antenna elements is M and the diversity gain is D, the capacity gain of M * D times and the coverage gain of M * D2 / g times (g is the propagation factor) can be given to the system according to the theoretical calculation The If the downlink transmit power is kept constant, increasing the number of elements to M, theoretically, the downlink can bring the same capacity gain and coverage gain. But in reality it is necessary to consider the performance improvement, but also consider the cost. The increase in the number of elements will increase the RF channel accordingly, thus causing the base station cost to rise too much. According to 3G equipment manufacturers and operators of the comprehensive consideration, the first commercial smart antenna base station will be 4G antenna array base station.