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藍芽無線通訊網路天線 |
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Bluetooth Basics
Bluetooth wireless technology is
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short-range communications
technology intended to replace the cables connecting
portable and/or fixed devices while maintaining high levels
of security. The key features of Bluetooth technology are
robustness, low power, and low cost. The Bluetooth
specification defines a uniform structure for a wide range
of devices to connect and communicate with each other.
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Bluetooth technology has
achieved global acceptance such that any Bluetooth enabled
device, almost everywhere in the world, can connect to other
Bluetooth enabled devices in proximity. Bluetooth enabled
electronic devices connect and communicate wirelessly
through short-range, ad hoc networks known as pico-nets.
Each device can simultaneously communicate with up to seven
other devices within a single pico-net. Each device can also
belong to several pico-nets simultaneously. Pico-nets are
established dynamically and automatically as Bluetooth
enabled devices enter and leave radio proximity.
A fundamental Bluetooth wireless
technology strength is the ability to simultaneously handle
both data and voice transmissions. This enables users to
enjoy variety of innovative solutions such as a hands-free
headset for voice calls, printing and fax capabilities, and
synchronizing PDA, laptop, and mobile phone applications to
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Transmit Range
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Spectrum
Bluetooth technology operates in the unlicensed industrial,
scientific and medical (ISM) band at 2.4 to 2.485 GHz, using
a spread spectrum, frequency hopping, full-duplex signal at
a nominal rate of 1600 hops/sec. The 2.4 GHz ISM band is
available and unlicensed in most countries.
Interference
Bluetooth technology’s adaptive frequency hopping (AFH)
capability was designed to reduce interference between
wireless technologies sharing the 2.4 GHz spectrum. AFH
works within the spectrum to take advantage of the available
frequency. This is done by detecting other devices in the
spectrum and avoiding the frequencies they are using. This
adaptive hopping allows for more efficient transmission
within the spectrum, providing users with greater
performance even if using other technologies along with
Bluetooth technology. The signal hops among 79 frequencies
at 1 MHz intervals to give a high degree of interference
immunity.
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The operating range depends on
the device class:
•Class 3 radios – have a range of up to 1 meter
•Class 2 radios – most commonly found in mobile devices –
have a range of 10 meters
•Class 1 radios – used primarily in industrial use cases –
have a range of 100 meters |
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Power
The most commonly used radio is Class 2 and uses 2.5 mW of
power. Bluetooth technology is designed to have very low
power consumption. This is reinforced in the specification
by allowing radios to be powered down when inactive.
Data Rate
1 Mbps for Version 1.2; Up to 3 Mbps supported for Version
2.0 + EDR |
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