Smart Antenna refers to a system of antenna arrays with smart signal processing algorithms that are used to identify the direction of arrival (DOA) of the signal, and use it to calculate beamforming vectors, to track and locate the antenna beam on the mobile/target. The antenna could optionally be any sensor. A giant phased-array radar in Alaska In telecommunication, a phased array is a group of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and... In signal processing literature, direction of arrival denotes the direction from which usully a propagating wave arrives at a point, where usually a set of sensors are located. ... Beamforming is a signal processing technique used to make a collection of fixed simple antennas act like a single, highly focused, movable antenna. ...

Smart antenna techniques are used notably in acoustic signal processing, track and scan RADAR, Radio astronomy and Radio telescopes Radio Telescopes, and mostly in cellular systems like W-CDMA and UMTS. This long range radar antenna, known as ALTAIR, is used to detect and track space objects in conjunction with ABM testing at the Ronald Reagan Test Site on the Kwajalein atoll[1]. Radar is a system that uses radio waves to detect, determine the distance of, and map, objects such... 3G (or 3-G) is short for third-generation technology. ... W-CDMA (Wideband Code Division Multiple Access) is a type of 3G cellular network. ... Universal Mobile Telecommunications System (UMTS) is one of the third-generation (3G) mobile phone technologies. ...

Smart antennas have two main functions

1. DOA estimation
2. Beamforming

DOA estimation

The smart antenna system estimates the direction of arrival of the signal, using any of the techniques like MUSIC (Multiple Signal Classification) or ESPRIT (Estimation of Signal Parameters via Rotational Invariant Techniques) algorithms, or their derivatives. They involve finding a spatial spectrum of the antenna/sensor array, and calculating the DOA from the peaks of this spectrum. MUSIC involves calculation of eigenvalues and eigenvectors of an autocorrelation matrix of the input vectors from the receiving antenna array. These calculations are computationally intensive. In mathematics, a number is called an eigenvalue of a matrix if there exists a nonzero vector such that the matrix times the vector is equal to the same vector multiplied by the eigenvalue. ... In linear algebra, the eigenvectors (from the German eigen meaning own) of a linear operator are non-zero vectors which, when operated on by the operator, result in a scalar multiple of themselves. ... Autocorrelation is a mathematical tool used frequently in signal processing for analysing functions or series of values, such as time domain signals. ...

Beamforming

Beamforming is the method used to create the radiation pattern of the antenna array by adding constructively the phases of the signals in the direction of the targets/mobiles desired, and nulling the pattern of the targets/mobiles that are undesired/interfering targets. We basically implement a simple FIR tapped delay line filter to do this. The weights of this FIR filter may also be changed adaptively, and used to provide optimal beamforming, in the sense that it reduces the MMSE between the desired and actual beampattern formed. Typical algorithms are the steepest descent, and LMS algorithms. Beamforming is a latest technology being used for various purposes. In telecommunication, the term radiation pattern has the following meanings: 1. ... A finite impulse response (FIR) filter is a type of a digital filter. ... Minimum mean-square error (MMSE) relates to an estimator having estimates with the minimum mean squared error possible. ... Gradient descent is an optimization algorithm that approaches a local maximum of a function by taking steps proportional to the gradient (or the approximate gradient) of the function at the current point. ...

References

1. http://sarg.stanford.edu : Smart Antenna Research Group.
2. http://www.mprg.org : Virginia Tech, Mobile and Portable & Radio research group
3. http://smartantennas.googlepages.com : Personal Webpage, Chen SUN

See also

• Antenna (radio)
• Array processing
• Phased array