The Question of AD9625 Sample Clock


    I have some questions with AD9625, We set the sample clock at 2.4GHz with AD9516 and ADCLK948, but the ad9625

cannot work correctly, the rx_sync and rx_tvalid go low always . we measure the swing of sample clock, it is 1100mv VPP at the source (ADCLK948), but it decline to 200mv VPP at the target (AD9625). we do not know why. is there some wrong with the termination?  With this sample clock ,we use  200ohm pull down resistor at source (adclk948) ,0.1uf AC couple capacitor and 100ohm resistor placed betweeen P and target(ad9625).

     is there some wrong? Des AD9625 require 500mv or 250mv differential  swing.sample clock? By the way, why AD9625 has 40Kohm input resistor?

Thanks very much !