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AD9361 - TX EVM value interfered by RX frequency setting

Question asked by nsuzuki Employee on Sep 22, 2014
Latest reply on Sep 26, 2014 by tlili


I'm using IIO Oscilloscope to evaluate TX performance of AD9361.
When I measured EVM values of TX, I found a problem that the EVM values was interfered by setting of RX frequency.
One example of procedure to see the problem was below.
Step 1. Set TX to 6000MHz and LTE 64QAM signal.  Then, measure EVM value.
Step 2. Set RX frequency to 3000MHz.  Then, measure EVM value of TX again.
Step 3. Compare EVM values between above step 1 and 2.
As the result, the EVM value of Step 2 was worse than Step 1.

Since RX input is open, it doesn't receive any signal.

This problem was seen when RX frequency is 375MHz, 750MHz, 1500MHz, 3000MHz, 6000MHz in the case of TX frequency = 6000MHz.

Does anyone advise me the reason of this behavior?