As recommended by the AD7760 datasheet, I use the driving circuit shown as below.
The values of resistors and capacitors for differential amplifier configuration are as in Table 8.
For the AD8021, R = 50 Ohm.
Then I use signal generator to generate and input sine wave to test the ADC. The result I received shows that the output data of the ADC always get shifted about 160000 over 0 level.
Here are the result with sine wave input,
and the result without signal (only noise),
Any ideas why this might be happening? Should I change something in the design?