decibel - 1% 时的总信道功率为 -33.9 dBm

Question

如果功率计测量总通道功率的 1% 为 -33.9dBm，那么总通道功率是多少？

标签： decibel

Answer 1

The key concept here is that dBs enable the use of addition vs. multiplication:

Pt[in Watts] = 100 * Pm[in Watts]  ==>
Pt[in dBm's] = 10 log10(100) + Pm[in dBm's] =
               20            + -33.9 =
-13.9dBm

Check:
Pm = (10^(-33.9dBm/10))*0.001 = 0.000000407380278 Watts
Pt = (10^(-13.9dBm/10))*0.001 = 0.00004073802778 Watts

Pt[in milliWatts] = 100 * Pm[in milliWatts] =
0.00004073802778 =? 100 * 0.000000407380278 =
0.0000407380278