variation in Transmit power for different frequencies for AD9361 TX port in "ADI RF SOM" board

We use ADI-RFSOM(picozed) hardware.

When we pass our TX signals(BPSK modulated signal with 2.4 MHz bandwidth) to the AD9361, and observing the o/p at TX ports, the o/p power level varies for different frequencies

For same settings in HW and same signals sent to the AD9361 data port, the TX power for BPSK modulated signal is

-3dBm at 70MHz

+7dBm at 800MHz

+2dBm at 2.4 GHz

Why this variation is happening.

How we can get the  power levels as mentioned in the data sheet

Thank you