There is a Trace Functions in the Network Analyzer which allow us to display current measurement data, memory data and also some mathematic application of current linear measurement.

I am having problem on getting the formula for the subtraction of 2 –dB value. The formula below which I get from other website only applied to the +ve value.

For example, adding 2 levels 94+96+98:

L = 10log10(10^9.4+10^9.6 +10^9.8 ) =101.1

If I would like to have a subtraction on -22.699 and -22.406, I could not use the formula above. Anyone know how the subtraction being done on –ve value?

I am having problem on getting the formula for the subtraction of 2 –dB value. The formula below which I get from other website only applied to the +ve value.

For example, adding 2 levels 94+96+98:

L = 10log10(10^9.4+10^9.6 +10^9.8 ) =101.1

If I would like to have a subtraction on -22.699 and -22.406, I could not use the formula above. Anyone know how the subtraction being done on –ve value?

And to subtract logs you use dividers. Convert -22 to linear using N1=10^(-22/20). Convert -22.6 dB to linear using N2=10^(-22.6/20). Subtract the linear terms; N1-N2. Then, set the format to LogMag, and the formatter will compute 20*Log(N1-N2) and you will see -45.51. Note, I use 20Log(A) not 10Log(A) because I am assuming these are S-parameters and not powers. Equation editor always operates on the underlying linear complex data.

ON the other hand, if you would like the result to be 0.6 dB (the dB difference) then take 20Log(N1/N2).