Dear support,
I'm using an LTC2194 ADC to convert a 75 MHz RF signal 50 ohm coupled single-ended.
To interface the LTC2194 to the input signal I implemented the Figure 4. Recommended Front-End Circuit for Input Frequencies from 5MHz to 150MHz:
Even if the RF signal source i disconnected, is the noise floor of the ADC increase when the input transformer (T1) is connected to ground (as reported in fig. 4) with respect to the case when it is left floating (removing the ground connection by removing 0.1uF input cap). THe noise flore increase of more tha 10 dB when the input transformer is ground connected w.r.t. the case when the input transformer is left floating.
The increased noise does not depends on the source, the ADC shows an increased noise level also when the RF analog source is disconnected.
Is there something more to consider in order to interface the ADC with an RF single-ended signal? Maybe, some common-mode noise?
Some ADC register to configure?
