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So you've been handed the hot project of adding wireless capability
to your product? RF can be tricky. And now it's on your shoulders.
You're under pressure to get to market quickly and cheaply, but
you need the highest confidence in your design. And you want to
be assured that it will pass stringent approvals.
Impossible?
AeroComm can help. Since 1990,
we've commanded the RF industry with consistent price and performance
breakthroughs for both industrial and commercial applications.
First, review the online resources provided here. Then contact
AeroComm's sales and engineering team with your RF questions.
Toll-free 1-800-492-2320, email wirelesssystems@lairdtech.com.
Radio Frequency Explained
Radio Frequency (RF) refers
specifically to the electromagnetic field, or radio wave, that
is generated when an alternating current is input to an antenna.
This field can be used for wireless broadcasting and communications
over a significant portion of the electromagnetic radiation spectrum
-- from about 9 kilohertz (kHz) to thousands of gigahertz (GHz)
-- referred to as the RF spectrum. As the frequency is increased
beyond the RF spectrum, electromagnetic energy takes the form
of infrared, visible light, ultraviolet, X rays and gamma rays.
Many types of wireless devices make use of RF fields: radio, television,
cordless phones, cell phones, satellite comm systems, and many
measuring and instrumentation systems used in manufacturing. Some
wireless devices, such as remote control boxes and cordless mice,
operate at infrared or visible light frequencies.
The RF spectrum is divided into several ranges, or bands. Each
of these bands, other than the lowest frequency segment, represents
an increase of frequency corresponding to an order of magnitude
(power of ten). FCC rules, combined with the continuing evolution
of digital technology, sparked the development of spread spectrum
data communication radios. These radios offer significant performance
and operation benefits to end-users.
The conventional radio signal which these devices use is referred
to as narrow-band, which means that it contains all of its power
in a very narrow portion of the radio frequency bandwidth. Due
to the relatively small portion of the radio band that an individual
radio transmission occupies, the FCC has traditionally favored
these conventional radios. However, as a result of the very narrow
frequency, these radios are often prone to interference (a single
interfering signal at or near their frequency can easily render
the radio inoperable).
Spread spectrum is a technique that takes a narrow band signal
and spreads it over a broader portion of the radio frequency band,
offering the operational advantage of being resistant it interference.
Spread spectrum radios are inherently more noise-immune than conventional
radios. Thus they will operate with higher efficiency than conventional
technology.
In performing spread spectrum, the transmitter takes the input
data and spreads it in a predefined method. Each receiver must
understand this predefined method and despread the signal before
the data can be interpreted. There are two basic methods to performing
the spreading: frequency hopping (FHSS) and direct sequence (DSSS).
FHSS spreads its signals by "hopping" the narrow band
signal as a function of time. DSSS its signal by expanding the
signal over a broad portion of the radio band.
The FCC allows the use of spread spectrum technology in three
radio bands, 902-928 MHz, 2400-2483.5 MHz and 5752.5-5850 MHz
for transmission under 1 Watt of power. This power limit prevents
interference within the band over long distances. Spread spectrum
requires no FCC site license; the FCC grants a one-time license
on the radio product. After that license is granted, the product
can be sold anywhere in the U.S.
"Radio Frequency Explained"
is provided by Spread
Spectrum Scene, your complete online RF and spread spectrum
resource.
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