一分贝(dB)表示单元信号强度的相对差异。其比率的基础对数为10,,如dB = 10 x Log10 (P1/P2)。
基础10对数规则:
对数系统中有如下运算:
1 mW | 1 mW/1mW=1 | 0 dbm = 10 x Log10 (1) |
2 mW | 2 mW/1mW=2 | 3 dbm = 10 x Log10 (2) |
4 mW | 4 mW/1mW=4 | 6 dbm = 10 x Log10 (4) |
10 mW | 10 mW/1mW=10 | 10 dbm = 10 x Log10(10) |
0.1 W | 100 mW/1mW=100 | 20 dbm = 10 x Log10(100) |
1W | 1000 mW/1mW=1000 | 30 dbm = 10 x Log10 (1000) |
10 W | 10000mW/1mW=10000 | 40 dbm = 10 x Log10 (10000) |
dbm = dB毫瓦特= 10 x Log10 (电源mW/1mW)
电源 | 比率 | dbm = 10 x Log10 (电源在兆瓦mW/1mW) |
1 mW | 1 mW/1mW=1 | 0 dbm = 10 x Log10 (1) |
2 mW | 2 mW/1mW=2 | 3 dbm = 10 x Log10 (2) |
4 mW | 4 mW/1mW=4 | 6 dbm = 10 x Log10 (4) |
10 mW | 10 mW/1mW=10 | 10 dbm = 10 x Log10(10) |
0.1 W | 100 mW/1mW=100 | 20 dbm = 10 x Log10(100) |
1W | 1000 mW/1mW=1000 | 30 dbm = 10 x Log10 (1000) |
10 W | 10000mW/1mW=10000 | 40 dbm = 10 x Log10 (10000) |
dbw = dB瓦特= 10 x Log10 (电源W/1W)
电源 | 比率 | dbm = 10 x Log10 (电源W/1W) |
1W | 1与1 W = 1 | 0 dbw = 10 x Log10 (1) |
2 W | 2与1 W = 2 | 3 dbw = 10 x Log10 (2) |
4 W | 4与1 W = 4 | 6 dbw = 10 x Log10 (4) |
10 W | 10与1 W = 10 | 10 dbw = 10 x Log10(10) |
100 W | 0,1与1 W = 0,1 | -10 dbw = -10 x Log10(10) |
10 W | 0,01与1 W = 1/100 | -20 dbw = -10 x Log10(100) |
1 W | 0,001W/1W=1/1000 | -30 dbw = -10 x Log10 (1000) |
在射频信号中,0dBm=1mW,每3dB功率信号翻倍,每10dB功率信号变为10倍;对电压信号,则是每6dB电压信号翻倍,每20dB电压信号变为10倍