分贝毫瓦的概念(外国英语资料).docVIP

分贝毫瓦的概念 DBm (2009-09-09 08:39:36) on the label: DBm means decibels of decibels. Decibel a referenced (deciBels to mW) refers to the use of logarithmic form of power measurement, dBm to 1mW as a reference. Power unit and P (Watt) conversion formula: (10*P) dBm= (10*P) dB-30dB (P: watts) First of all, DB is a pure counting unit: for power, dB = 10*lg (A/B). For voltage or current, dB = 20*lg (A/B).DB in fact again simple, is a large (followed by a long string of 0) or small (in front of a long string of 0) the number of relatively brief representation. Such as: X=1000000000000000 (how many?) 10lgX=150dB X=0.000000000000001 10lgX=-150 dB DBm defines miliwatt. 0 dBm=10lg1mw; DBw defines watt. 0 dBw = 10lg1, W = 10lg1000, Mw = 30, dBm. The DB always defines power units by default, with 10lg as the gauge. Of course, in some cases signal power (Amplitude) can be used to describe the work and power, and this time the 20lg is used. This is true in both the control and signal processing areas. For example, sometimes you can see the expression of dBmV. In dB and dBm computing, pay attention to the basic concepts. For example, the previous said 0dBw = 10lg1W = 10lg1000mw = 30dBm; and, for example, using one dBm minus another dBm, the result is dB. Such as: 30dBm - 0dBm = 30dB. Generally speaking, in engineering, between dB and dB not only addition and subtraction, multiplication and division. Which is the most used method: dBm minus dBm is actually two phase power, signal power and noise power is the division of signal-to-noise ratio (SNR). DBm plus dBm is actually a multiplication of two powers, which is rare (I only know this in power spectral convolution calculations). What is dBm by dBm, and 1mW by 1mW? In addition to the students who write to me so that I can almost keep pace with Gerd Bachs expression, Ive lived for so many years, and I havent seen any engineering areas to play with this. The dB is the unit of power gain that represents a relative value. When the power of