decibels relative to one millivoltdBmV (decibels relative to one millivolt) is a measure of the signal strength in wires and cables at RF and AF frequencies. A millivolt is 1/1000 of a volt (0.001 V or 10 -3 V). This unit is defined in terms of root-mean-square ( rms ) alternating current ( AC ) signal voltages in circuits in which the impedance is a pure resistance of some specified value. The dBmV increment is based on the decibel , a logarithm ic measure of relative signal strength. Suppose a signal has an rms voltage of E mV. Then the signal strength in dBmV, symbolized S dBmV , is: S dBmV = 20 log 10 E A 1-mV signal across a pure resistance has a level of 0 dBmV. Signals weaker than 1 mV have negative dBmV values; signals stronger than 1 mV have positive dBmV values, assuming the impedance remains a pure resistance and remains constant.
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| Last updated on:
Apr 05, 2005 |
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