Smart antennas (also known as adaptive array antennas,

digital antenna array Digital antenna array (DAA) is a smart antenna with multi channels digital beamforming, usually by using fast Fourier transform (FFT). The development and practical realization of digital antenna arrays theory started in 1962 under the guidanc ...

s, multiple antennas and, recently, MIMO) are

antenna array An antenna array (or array antenna) is a set of multiple connected antenna (radio), antennas which work together as a single antenna, to transmit or receive radio waves. The individual antennas (called ''elements'') are usually connected to a s ...

s with smart

signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as audio signal processing, sound, image processing, images, Scalar potential, potential fields, Seismic tomograph ...

algorithm In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algo ...

s used to identify spatial signal signatures such as the direction of arrival (DOA) of the signal, and use them to calculate

beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles ...

vectors which are used to track and locate the antenna beam on the mobile/target. Smart antennas should not be confused with reconfigurable antennas, which have similar capabilities but are single element antennas and not antenna arrays. Smart antenna techniques are used notably in acoustic signal processing, track and scan

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

radio astronomy Radio astronomy is a subfield of astronomy that studies Astronomical object, celestial objects using radio waves. It started in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way. Subsequent observat ...

and

radio telescope A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...

s, and mostly in cellular systems like W-CDMA,

UMTS The Universal Mobile Telecommunications System (UMTS) is a 3G mobile cellular system for networks based on the GSM standard. UMTS uses Wideband Code Division Multiple Access, wideband code-division multiple access (W-CDMA) radio access technolog ...

, and LTE and 5G-NR. Smart antennas have many functions: DOA estimation,

, interference nulling, and constant modulus preservation.

Direction of arrival (DOA) estimation

The smart antenna system estimates the direction of arrival of the signal, using techniques such as

MUSIC Music is the arrangement of sound to create some combination of Musical form, form, harmony, melody, rhythm, or otherwise Musical expression, expressive content. Music is generally agreed to be a cultural universal that is present in all hum ...

(MUltiple SIgnal Classification), estimation of signal parameters via rotational invariance techniques (ESPRIT) algorithms, Matrix Pencil method or one of their derivatives. They involve finding a spatial spectrum of the antenna/

sensor array A sensor array is a group of sensors, usually deployed in a certain geometry pattern, used for collecting and processing electromagnetic or acoustic signals. The advantage of using a sensor array over using a single sensor lies in the fact that an ...

, and calculating the DOA from the peaks of this spectrum. These calculations are computationally intensive. Matrix Pencil is very efficient in case of real time systems, and under the correlated sources.

Beamforming

Beamforming Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles ...

is the method used to create the

radiation pattern In the field of antenna design the term radiation pattern (or antenna pattern or far-field pattern) refers to the ''directional'' (angular) dependence of the strength of the radio waves from the antenna or other source.Constantine A. Balanis: " ...

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. This can be done with a simple Finite Impulse Response (FIR) tapped delay line filter. The weights of the FIR filter may also be changed adaptively, and used to provide optimal beamforming, in the sense that it reduces the Minimum Mean Square Error between the desired and actual beampattern formed. Typical algorithms are the

steepest descent Gradient descent is a method for unconstrained mathematical optimization. It is a :First order methods, first-order Iterative algorithm, iterative algorithm for minimizing a differentiable function, differentiable multivariate function. The ide ...

, and

Least Mean Squares Least mean squares (LMS) algorithms are a class of adaptive filter used to mimic a desired filter by finding the filter coefficients that relate to producing the least mean square of the error signal (difference between the desired and the actua ...

algorithms. In digital antenna arrays with multi channels, use the digital beamforming, usually by DFT or FFT.

Types of smart antennas

Two of the main types of smart antennas include switched beam smart antennas and adaptive array smart antennas. Switched beam systems have several available fixed beam patterns. A decision is made as to which beam to access, at any given point in time, based upon the requirements of the system. Adaptive arrays allow the antenna to steer the beam to any direction of interest while simultaneously nulling interfering signals. Beamdirection can be estimated using the so-called direction-of-arrival (DOA) estimation methods. In 2008, the United States

NTIA The National Telecommunications and Information Administration (NTIA) is a bureau of the United States Department of Commerce that serves as the President of the United States, president's principal adviser on Telecommunications policy of the U ...

began a major effort to assist consumers in the purchase of digital television converter boxes. Through this effort, many people have been exposed to the concept of smart antennas for the first time. In the context of consumer electronics, a "smart antenna" is one that conforms to the EIA/

CEA-909 CEA-909 is the ANSI standard for 8VSB/ATSC smart antennas. The basic concept is that the smart antenna either physically rotates toward the signal, or is stationary, but has elements pointed in different directions and uses only those elements that ...

Standard Interface. In 2017, the Israeli Aerospace Industries unveiled an adaptive array antenna called ADA, and stated that it is already operational and shall be fitted onto "major platforms" used by the

Israel Defense Forces The Israel Defense Forces (IDF; , ), alternatively referred to by the Hebrew-language acronym (), is the national military of the State of Israel. It consists of three service branches: the Israeli Ground Forces, the Israeli Air Force, and ...

Limited choice of EIA/CEA-909A smart antennas in the marketplace

Prior to the final transition to ATSC

digital television Digital television (DTV) is the transmission of television signals using Digital signal, digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an ...

in the United States on 11 June 2009, two smart antenna models were brought to market: * RCA ANT2000 – no longer available from retailers * DTA-5000 – manufactured by Funai Electric, marketed under the "DX Antenna" brand name, sometimes associated with the Sylvania brand name; no longer available from retailers And two models are causing consumer confusion: * Although the Apex SM550 is capable of connecting to a CEA-909 port for the purpose of drawing electrical power, it is not a true smart antenna. * The Channel Master 3000A and CM3000HD SMARTenna series are otherwise-conventional amplified omnidirectional antennas, not steerable smart antennas. * ADA - An adaptive antenna produced by MLM factory of the

Israel Aerospace Industries Israel Aerospace Industries (IAI; ), is Israel's major aerospace and aviation manufacturer, producing aerial and astronautic systems for both military and civilian usage. It has 14,000 employees as of 2021. IAI is state-owned by the government ...

References

External links

Smart Antenna Research Group
at Stanford
Virginia Tech, Mobile and Portable & Radio research group
{{North American DTV Smart devices Radio frequency antenna types Antennas (radio)