### Q

I am interested in a build a Vector Network Analyzer but AD8302 can onlydetect +-90 degrees.

To make a good Vector Network Analyzer its not necessary to detect +-180

degrees?

### A

IN fact the AD8302 allows you to measure 0 to 180deg phase but there is nosimple way to determine direction of phase.

One possibility is to temporarily insert a known phase shift into one of the

signal paths and then observe the way in which the VPHS output changes. When

slope of the VPHS output is determined, then one can determine in which

quadrant the angle lies.

For narrow band applications (which obviously does not describe this

application) two AD8302's can be used. The INPA's for each of the AD8302's are

connected to the same signal, via transmission lines of equal electrical

length. One of the INPB inputs is connected to the other signal of interest.

The second INPB is connected to the same signal, but via a transmission line

that is 90 degrees linger. Then, the VPHS outputs can be compared to each

other to determine the phase angle anywhere between 0 and 360 degrees.