I use AD9467-200 ADC in SDR-receiver and I have some troubles with SFDR.
Sampling frequency is 197.5 MHz and according to datasheet SFDR must be about 90 dB with 170 MHz input signal.
IF band in my SDR receiver is 140 MHz ± 10 MHz and there is antialiasing filter at the input of ADC.
When signal with 141.07143 MHz is applied to the ADC, I can see many of spurs from highest Nyquist zones in the narrow band. And the largest one is about -40 dBc - so SFDR is just 40 dB instead of 90 dB(see attachment picture).
ADC is not overdrived - signal level to spur level ratio is equally when signal is less.
What are the possible causes of this problem? Is it schemotechnical or PCB routing defects or just ADC feature?
Can somebody examine this ADC on evaluating board with the following parameters: Fclk=197.5MHz, Fin=141.07143MHz, Vin = Vfs-1dB?
Thank you for your attention.