I am using ADL5382 to build an transceiver for UHF RFID. The board is designed by myself. I had a problem on the I positive/negative channels.
A -20dBm 900MHz signal is input as the RF signal and -4dBm 902MHz signal is input as the LO. I expected to see the 180 degrees phase shift between the I positive channel and I negative channel. However, in my case there is no phase shift on the P and N channels at all. It works all fine on the Q positive and Q negative channels. And one more observation is that phase **** is increasing with the decrease of the mixed signal (frequency of LO minus frequency of the RF), which means if I use the same frequency for RF and LO, the mixed result from I is positive DC and the mixed result from Q negative is negative DC.
I suspect the error is coming from the soldering problem which I will recheck it.
Would anybody tell me some other possible reasons which could cause this problem and the solution to debug this problem?
Thanks very much!