Smart antenna
Encyclopedia
Smart antennas are antenna array
s with smart signal processing algorithms used to identify spatial signal signature such as 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.
Smart antenna techniques are used notably in acoustic signal processing, track and scan RADAR
, radio astronomy
and radio telescope
s, and mostly in cellular systems
like W-CDMA
and UMTS.
Smart antennas have two main functions: DOA estimation and Beamforming.
(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, 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.
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.
This can be done with a simple 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 MMSE between the desired and actual beampattern formed. Typical algorithms are the steepest descent, and LMS algorithms [4].
In 2008, the United States NTIA
began a major effort to assist consumers in the purchase of digital television converter boxes
.http://www.dtv2009.gov/ 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
Standard Interface.
in the United States on June 11, 2009, two smart antenna models were brought to market:
And two models are causing consumer confusion:
Antenna array
Antenna array may refer to:*Antenna array a group of isotropic radiators such that the currents running through them are of different amplitudes and phases*Interferometric array of radio telescopes used in radio astronomy...
s with smart signal processing algorithms used to identify spatial signal signature such as the direction of arrival
Direction of arrival
In signal processing literature, direction of arrival denotes the direction from which usually a propagating wave arrives at a point, where usually a set of sensors are located. This set of sensors forms what is called a sensor array. Often there is the associated technique of beamforming which...
(DOA) of the signal, and use it to calculate beamforming
Beamforming
Beamforming is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in the array in a way where signals at particular angles experience constructive interference and while others experience destructive...
vectors, to track and locate the antenna beam on the mobile/target. The antenna could optionally be any sensor.
Smart antenna techniques are used notably in acoustic signal processing, track and scan RADAR
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
, radio astronomy
Radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
and radio telescope
Radio telescope
A radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
s, and mostly in cellular systems
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...
like W-CDMA
W-CDMA
W-CDMA , UMTS-FDD, UTRA-FDD, or IMT-2000 CDMA Direct Spread is an air interface standard found in 3G mobile telecommunications networks. It is the basis of Japan's NTT DoCoMo's FOMA service and the most-commonly used member of the UMTS family and sometimes used as a synonym for UMTS...
and UMTS.
Smart antennas have two main functions: DOA estimation and Beamforming.
Direction of arrival (DOA) estimation
The smart antenna system estimates the direction of arrival of the signal, using techniques such as MUSICMultiple signal classification
MUltiple SIgnal Classification is an algorithm used for frequency estimation and emitter location.- MUSIC algorithm :In many practical signal processing problems, the objective is to estimate from measurements a set of constant parameters upon which the received signals depend...
(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, 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
BeamformingBeamforming
Beamforming is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in the array in a way where signals at particular angles experience constructive interference and while others experience destructive...
is the method used to create the radiation pattern
Radiation pattern
In the field of antenna design the term radiation pattern most commonly refers to the directional dependence of the strength of the radio waves from the antenna or other source ....
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 FIR
Finite impulse response
A finite impulse response filter is a type of a signal processing filter whose impulse response is of finite duration, because it settles to zero in finite time. This is in contrast to infinite impulse response filters, which have internal feedback and may continue to respond indefinitely...
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 MMSE between the desired and actual beampattern formed. Typical algorithms are the steepest descent, and LMS algorithms [4].
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 [3]. Beamdirection can be estimated using the so-called direction-of-arrival (DOA) estimation methods [6].In 2008, the United States NTIA
National Telecommunications and Information Administration
The National Telecommunications and Information Administration is an agency of the United States Department of Commerce that serves as the President's principal adviser on telecommunications policies pertaining to the United States' economic and technological advancement and to regulation of the...
began a major effort to assist consumers in the purchase of digital television converter boxes
Coupon-eligible converter box
A coupon-eligible converter box was a digital television adapter that met eligibility specifications for subsidy "coupons" from the United States government...
.http://www.dtv2009.gov/ 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
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 pointed toward the signal...
Standard Interface.
Limited Choice of EIA/CEA-909A Smart Antennas in the Marketplace
Prior to the final transition to ATSC Digital televisionDigital television
Digital television is the transmission of audio and video by digital signals, in contrast to the analog signals used by analog TV...
in the United States on June 11, 2009, two smart antenna models were brought to market:
- RCA ANT2000 -- no longer available from retailers
- DTA-5000 -- 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.http://www.avsforum.com/avs-vb/showthread.php?p=16553780
- The unfortunately-named Channel Master 3000A SMARTenna is a conventional antenna, not a smart antenna.http://webcache.googleusercontent.com/search?q=cache:AuWXatS9qWUJ:www.solidsignal.com/pview.asp%3Fp%3Danc3000+%22does+not+have+SMART+ANTENNA+Technology%22&cd=1&hl=en&ct=clnk&gl=us
Extension of smart antennas
Smart antenna systems are also a defining characteristic of MIMO systems, such as the IEEE 802.11n standard. Conventionally, a smart antenna is a unit of a wireless communication system and performs spatial signal processing with multiple antennas. Multiple antennas can be used at either the transmitter or receiver. Recently, the technology has been extended to use the multiple antennas at both the transmitter and receiver; such a system is called a multiple-input multiple-output (MIMO) system. As extended Smart Antenna technology, MIMO supports spatial information processing, in the sense that conventional research on Smart Antennas has focused on how to provide a beamforming advantage by the use of spatial signal processing in wireless channels. Spatial information processing includes spatial information coding such as Spatial multiplexing and Diversity Coding, as well as beamforming.See also
- Antenna (radio)Antenna (radio)An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
- Array processingArray processingArray processing is signal processing of the outputs of an array of sensors to:* Enhance the signal-to-interference-plus-noise ratio compared to that of a single sensor using conventional or adaptive beamforming....
- Phased arrayPhased arrayIn wave theory, a phased array is an array 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 suppressed in undesired directions.An antenna array...
- CEA-909CEA-909CEA-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 pointed toward the signal...
- Mimax
- diversity combiningDiversity combiningDiversity combining is the technique applied to combine the multiple received signals of a diversity reception device into a single improved signal.- Various techniques :Various diversity combining techniques can be distinguished:...