Smart Antenna Fundamentals – Introduction For Wireless Communications
Smart antennas are comprised of a number of individual antennas and associated signal processors which provide the “smart” portion. These are also referred to as adaptive array antennas, switched beam antennas and MIMO antennas.
Smart antennas are used on either, or both, the signal transmission side and the signal reception side. A well designed system in a typical environment can be expected to achieve up to 10 dB to 15 dB gain, with existing technology. This is anticipated to double within the next 5 years.
For more in-depth information on the specifics for each of these smart antenna configurations, please refer to our related articles:
Multiple-Input Multiple-Output Antennas
Beam Forming and Adaptive Array Antennas
The major benefits to using a smart, active antenna system come from a reduction in overall system power, reduction in communication interference, increase in system capacity and increase in power efficiency.
The antenna itself can be nearly anything from a simple copper trace on a printed circuit board, to a wire, to a much more complex set of sensors. It is worth noting that the actual antennas used in a smart system can be exactly the same as those in a standard system. The architectural differences are in the number of antenna elements and the real-time signal processing behind the antennas.
Using a smart antenna at the receiver provides for a reduction of signal loss in multipath fading, which in turn means a more overall robust signal quality independent of the variations of the transmitted signal due to the physical environment and other electromagnetic interferences. For mobile applications, there are fewer dropped calls, reduced areas of low-signal / no-signal (e.g., “dead zones”), better reception within buildings and consistently higher data rates.
Aside Note – Multipath refers to multiple versions of the same transmitted signal arriving at the receiver from different paths. This occurs, for example, when a signal bounces off of multiple buildings, walls, clouds, etc.. Due to the bounces or reflections, each of these multiple signals now has a different distance, or path, to reach the receiver. This call also be thought of as the same transmitted signal arriving repeatedly at slightly different times.
For transmission from a central station or fixed location, the signal processing algorithms are used to calculate beam forming vectors. As the name implies, beam forming creates a transmission signal with a spatial signature to maximize signal reception at the receiver.
If there is two way communication from the receiver back to the transmitter, this can also enable location and tracking of the receiver. This is critical for mobile applications such as wireless / cellular communications (e.g., consumer phones, tablets, laptops, etc.) as well as for communications with all types of vehicles (e.g., automobiles, trains, ships, planes, etc.).
Smart antenna design also benefits hand-held / mobile transmitters with longer battery life, or smaller battery for the same usage, since the transmitted signal strength output can be lower when compared with a system not using smart antennas.
In conjunction with beam forming, software, algorithms and processing at the transmitter use Direction Of Arrival (DOA) estimation algorithms to optimize the transmission signal.
It is becoming more critical for wireless phone and data providers to develop methods to provide increased coverage and higher data rates to consumers, while reducing their own operating costs. There is also a scarcity of sites where operators can install additional cell / transmission towers which is driving them to utilize a greater number of smaller, lower transmission power “micro-cells” and “pico-cells”. This technique is referred to as “cell splitting” in which multiple smaller base stations, each covering a smaller geographic area, are used in place of a higher powered station.
However, this creates a problem in itself as each cell is using the same frequency spectrum for communications. The numerous small cells are now effectively becoming a source of interference to the other cells as well as the mobile customers.
Taking all of these instances into account, smart antenna design has been the most cost effective method to provide consistent, continuous and comprehensive wireless communications.
If you would like a more in-depth treatment on smart antenna and antenna design, may we suggest the following books available through Amazon:
Practical Antenna Handbook ($29.96 – paperback)
A Student’s Guide to Maxwell’s Equations ($30.22 – paperback)
Antenna Design for Mobile Devices ($155.00 – hardcover)
Smart Antennas with MATLAB ($106.25 – hardcover)
Smart Antennas ($168.00 – hardcover)
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