On a reader embedding MFRC630+, after matching the antenna, we saw that the measured pulse shape according to ISO14443A is not conform.
**** Without any tag near the reader
t1=3us, t2=0us, t3=2.4 us and t4=0.4us
**** With a tag near the reader
t1=3us, t2=1.34us, t3=1.8us and t4=0.6us
1. When should be measured the pulse shape? with or without tag?
2. What could be the impacts when the pulse shape is not good?
3. How to improve this pulse shape?