The frequency of the templates FFT on VisualAnalog using Evaluation Board for AD9278 & AFE HSC_ADC_EVALC has regular errors

niqilulu on Aug 19, 2019

Hi,

We brought your AD9278 Evaluation Board and AFE HSC_ADC_EVALC board , and following the "AD9278_79_EVB_User_Guide.pdf" , setting power, setting the SPI control. Then we using an signal synthesizer generate one 1MHz / Vpp=5V sine wave , input to the CH_A, then we run the FFT test on VisualAnalog, but the result show the highest energy signal frequency is around 0.76MHz, at the meantime ,there is no signal around 1MHz.

We also test 5MHz, the final analysis results show the highest energy signal frequency is around 3.8MHz, and the 10MHz input sine signal , final show 7.6MHz signal.

we read the UG sevral times, but still cannot solve this problem , so we need your help.

0 AshrafS

on Aug 19, 2019 2:24 PM
5Vpp is too high and will saturate the LNA. Please check the max input voltage based on the LNA gain setting Table 1.
Cancel
Up 0 Down

Reply

Verify Answer

Cancel
0 niqilulu on Aug 20, 2019 2:22 AM in reply to AshrafS

change the Vpp = 160mV, but the frequency problem still exist。
Cancel
Up 0 Down

Reply

Verify Answer

Cancel
0 niqilulu on Aug 20, 2019 2:41 AM in reply to AshrafS

we find some rules, if we input 1.3 Mhz Vpp = 160mv, the FFT show the input frequency is around 1MHz; and 2.6MHz input , show 2MHz; 7.8MHz show 6MHz finally.

seems the final analysis results show the signal frequency multiply 1.3 = actual input frequency.
Cancel
Up 0 Down

Reply

Verify Answer

Cancel