Hi
As you have probably found, the RF suffix is used on one group of 12 bit GSPS ADC devices, specifically the ADC12D500RF, ADC12D800RF, ADC12D1000RF, ADC12D1600RF and ADC12D1800RF to distringuish them from the earlier released non-RF suffix 12 bit products (ADC12D1000, ADC12D1600, ADC12D1800).
The key difference between the RF and non-RF 12 bit products are improvements to the front end circuitry to improve noise floor and linearity in the RF family. This results in slightly better SNR and better SFDR particularly with high frequency input signals. You are probably referring to this previous post: http://e2e.ti.com/support/data_converters/high_speed_data_converters/f/68/p/233756/821637.aspx
The ADC08D1520 ADC will provide very good performance with high frequency inputs as well. Typical performance versus Fin can be found in the Typical Performance Plots in the ADC08D1520 product datasheet. The key to implementing an RF sampling system with this device will be choosing signal path components that do not degrade the RF signal quality prior to capture at the ADC inputs. The recommended Balun components listed in the ADC12D1800RF product datasheet would also be good fits in an 8 or 10 bit application.
I hope this is helpful.
Best regards,
JIm B