spent 3 hours on thinking and made the angle indicator. i used a rod with 172mm. so for 1 degree of change, the distance it will move is:
did few data but the data seem to be unusual. calibrate the network analyser and found that the analyser is not correct.
since the microwave reflection signal is not as usual, i reset the microwave system. but it did not correct the reflection signal.
found that 1.6us is not a 90 degree pulse. it may be due to the magnetic field changed.