dBm 是以 1mW為參考基準
輸出為10 dBm，所以輸出功率
10 = `10 log (P_o/(1m))`
1 = ` log (P_o/(1m))`
10 = `(P_o/(1m))`
`P_o` = 10mW
`P = V^2/R`
10m = `V^2/25`
`V^2`=0.25
`V`=0.5 V
