Choosing the right antenna to match your system requirements is critical for maximizing the range, data through-put, reliability and overall-robustness Antenna selection is often one of the last stages in the design cycle for many wireless products. However, choosing the right antenna to match your system requirements is critical for maximizing the range, data through-put, reliability and overall-robustness.
It’s also important at the beginning of the systems specification phase to determine what overall data through-put rates will be required and what antenna configuration best meets that requirement. This often determines which chip or chip-set is needed for the wireless application (please see related article Marvell Avastar 88W8897 MIMO Wi-Fi Combo chip ).
Starting with the desired application to chose the chip, this determines the possible antenna configurations. This will also determine the RF frequency of operation for the system. Standard bands for terrestrial applications are:
260 – 470 MHz
860 – 960 MHz
1.557 GHz (GPS specific)
800 MHz – 2.2 GHz (Cellular specific)
2.4 GHz – 2.5 GHz
4.9 GHz – 5.875 GHz
The majority of consumer devices including mobile devices, video gaming consoles, smart television and wireless routers operate in either the ~2.5 GHz, ~5 GHz or dual-band using either or both of these frequencies
Depending on the design requirements and application, the antenna may be as simple as a strip line of copper on the printed circuit board, an internal wire, externally mounted assembly or a combination. Earliest products used a single antenna, now referred to as Single Input, Single Output (SISO) technology. Products that use SISO can only send or receive a single spatial data stream at one time.
Today’s system typically employ a Multiple Input, Multiple Output (MIMO) technology in which 2, 4, 6, 9 or more antennas are used. Common configurations are 2×2 (two transmitting, two receiving), 2×3 (two transmitting, three receiving) and 3×3 (three transmitting, three receiving). Newer systems are incorporating “MU-MIMO” configurations, for Multiple Users (MU). Multi-user MIMO algorithms are developed to enhance MIMO systems when the number of users or connections is greater than one.
MIMO is a wireless technology that uses multiple transmitters and receivers to transfer to increase the amount of data transmitted / received, or to boost the relative signal strength for less errors in the data stream or a combination of the two. This technology takes advantage of a radio-wave phenomenon called multipath where transmitted information bounces off walls, ceilings, and other objects, reaching the receiving antenna multiple times via different angles and at slightly different times.
Using multiple, “smart” transmitters and receivers the system can send and receive multiple data streams at the same time. Electronics in the receivers combine data streams arriving from different paths and at different times to effectively increase receiver signal-capturing power.
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
A Student’s Guide to Maxwell’s Equations
Antenna Design for Mobile Devices
Smart Antennas with MATLAB
Antennas suppliers are:
Laird – IAS
Laird Technologies – Wireless
M2M Linx Technologies
Multi-Tech Systems, Inc.
Roving Networks, Inc.
TE Connectivity AMP, formerly Tyco Electronics AMP
Würth Electronics, Inc.
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