3.0 Interpreting RL Sweepscont. 
3.5 Cable Impedancecont. 
Now determine if the valley or peak is closer to the RL reading. The readings were obtained from figure 3.5.1. 
The valley is at 17.4 dB, using the formula: 
Dev_{v}=Read_{v}RL_{v}=17.416.098=1.302 
The peak is at 12.56 dB, using the formula: 
Dev_{p}=Read_{p}RL_{p}=16.14812.56=3.588 
It is obvious that the valley is the point of minimum deviation. The valley will now be refered to as the min point and the peak will be the max point. 
Note: it is very important not to confuse these points during the remaining calculations! 
4. Determine the rho of the pad. This can be found by the following formula: 
Rho_{pad}=10^^{(2xPadloss/20)} 
In the case of a 6.00 dB pad this works out to Rho=0.251 
5. Calculate the pad impedance from Rho: 
Z_{pad}=((1+rho>/(1rho))*50 
Z_{pad}=((1+.251>/(1.251))*50=83.51 
6. The next step is to calculate out the portion of the loss attributable to the cable. This is because we only want to see the transformation impedance. Since the cable loss adds to the return loss both coming and going it is multiplied by two. 
RL_{mincor}=RL_{min}2xLoss_{min} 
RL_{mincor}=17.42x2.094=13.301 
Repeat the operation for the max point 
RL_{maxcor}=R_{Lmax}2xLoss_{max} 
RL_{maxcor}=12.562x2.074=8.128 
7. Convert the return loss to rho. Using rho makes the math simpler in the subsequent equations. Use the following formulas: 
Rho_{min}=10^(RL_{mincor}/20) 
=10^(13.301/20)=.216 
Rho_{max}=10^(RL_{maxcor}/20) 
>=10^(8.128/20)=.380 
8. Develop a correction factor by subtracting Rho_{min}from the rho of the pad. 
CF=Rho_{pad}Rho_{min}=0.2510.216=0.035 
This correction factor corrects for an error term that occurs due to the mismatch losses of the coaxial cable under test. 
