Smart Antennas: What are they?

An overview, summary, or tutorial about the basics of smart antennas or the adaptive antenna array and smart antenna technology used with SDR, cognitive radio, MIMO, and other new technologies.

Smart Antenna Technology Includes:
Smart antenna basics Beamforming & beamsteering

Smart antennas and smart antenna technology using an adaptive antenna array are being introduced increasingly with the development of other technologies including the software defined radio, cognitive radio, MIMO and many others.

Smart antenna technology or adaptive antenna array technology enables the performance of the antenna to be altered to provide the performance that may be required to undertake performance under specific or changing conditions.

The smart antennas include signal processing capability that can perform tasks such as analysis of the direction of arrival of a signal and then the smart antenna can adapt the antenna itself using beam-forming techniques to achieve better reception, or transmission. In addition to this, the overall antenna will use some form of adaptive antenna array scheme to enable the antenna to perform is beam formation and signal direction detection.

Smart antenna functions

While the main purposes of standard antennas are to effectively transmit and receive radio signals, there are two additional functions that smart antennas or adaptive antennas need to fulfil:

Direction of arrival estimation: In order for the smart antenna to be able provide the required functionality and optimisation of the transmission and reception, they need to be able to detect the direction of arrival of the required incoming signal. The information received by the antenna array is passed to the signal processor within the antenna and this provides the required analysis.
Beam steering: With the direction of arrival of the required and any interfering signals analysed, the control circuitry within the antenna is able to optimise the directional beam pattern of the adaptive antenna array to provide the required performance.

Types of smart antenna

With considerable levels of functionality being required within smart antennas, two main approaches or types of smart antenna technology have been developed:

Switched beam smart antennas: The switched beam smart or adaptive antennas are designed so that they have several fixed beam patterns. The control elements within the antenna can then select the most appropriate one for the conditions that have been detected. Although this approach does not provide complete flexibility it simplifies the design and provides sufficient level of adaptivity for many applications.
Adaptive array smart antennas: Adaptive antenna arrays allow the beam to be continually steered to any direction to allow for the maximum signal to be received and / or the nulling of any interference.

Both types of antenna are able to provide the directivity, although decisions need to be made against cost, complexity and the performance requirements regarding which type should be used.

Summary

With many applications including MIMO, Software Defined Radio - SDR, and Cognitive Radio - CR requiring antenna systems to be more adaptive and provide greater levels of adaptivity, Smart antenna technology or adaptive antenna technology will become more widely used.