I want to use the AD9361 to implement WIFI data frame transceiver.My Interface Mode is CMOS、DDR、SinglePort，data_clk is 40MHz.
We use pulse mode to control the AD9361 ENSM.When the ENSM goes to the TX state from the ALERT state.
If we wait 9us to preserent the first data sample, the transmit EVM can be -35dbm(BPSK modulation).
If we shorten it to 6us, the EVM goes down to -27dbm。
Then I used agilent VSA to demod the AD9361 RF transmit signal.Found that at the beginning of each Frame,there is a slow rising lasting about 10us in time domain( shown below).
My Question is
What can cause the slow rising？
How to make the rising time at the beginning of the frame shorter（2us is the best ）
Thanks a lot！