A/D converter specifications for a receiver are fairly straightforward. you want as many bit's as you can afford. more bits translates to a higher dynamic range, which is a key receiver specification. In addition, with a higher dynamic range, you can ease the analog filtering requirements and the receiver gain control range.
At a minimum, you need to have enough dynamic range to digitize the complete dynamic range of the input signal.
• Receiver PAR. While this isn't an issue with a system such as GSM, with EDGE/WCDMA/WiMAX, the received signal has some amplitude variation that contains data, and needs to be captured. This Peak to Average ratio needs to be allowed for in the budget.
• Fading margin-The A/D converters needs to allow for some fading in the channel. This will be dependent on the system. For example, an system with non-mobile transmitters and receivers doesn't need as much fading margin as a highly mobile system such as a handset.
• Interfering channel. Having a higher A/D converter dynamic range allows the receiver filtering to move more into the digital domain from the Analog domain.
Dave
www.keystoneradio.com