| 单词 | dBm (deciBels referenced to a milliWatt) |
| 释义 | dBm (deciBels referenced to a milliWatt) A unit of measure used to reference signal strength to electrical power level. Unlike dB, which is a relative measure, dBm is an absolute measure, and can be used to express very small values (dBm) and very large values (dBW). The baseline reference relationship is 1mW = 0 dBm. A doubling of signal power yields an increase of approximately 3 dBm (2mW = 3 dBm) and halving of signal power yields a loss of approximately 3 dBm (500 µW = -3 dBm. Similarly, a tenfold increase in signal power yields an increase of approximately 10 dBm (10mW = 10 dBm) and a decrease of 90 percent of signal power yields a loss of approximately 10 dBm (100 µW = -10 dBm).The dBm measurement is used extensively in radio and fiber optics networking. Bluetooth Class 1 radios operate at a maximum 100 mW (20 dBm) and have a nominal link range of 100 meters (300 feet). Bluetooth Class 3 radios operate at a maximum of 1 mW (0 dBm) and have a nominal range of 1 meter (3 feet). A typical 100Base-FX Ethernet LAN might use a fiber optic laser with an operating wavelength of 1550 nm and a launch power range from a maximum of 0 dBm and minimum –5 dBm and a receiver with a sensitivity of –34 dBm. See also 100Base-FX, Bluetooth, dB, Ethernet, laser, signal, and wavelength. |
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