Specifications for A/D Converters in Cellular and Connectivity Receivers

The design of a receiver system asks for relations between system level choices, and their impact on the specifications of the different receiver building blocks, to come to an optimized system partitioning. This chapter will relate system level specifications to the RF front-end and ADC requirements. The chapter starts with a discussion about the relation between the choice of IF frequency and the receiver image rejection, DC offset, and 1/f noise requirements. Next, the ADC DR will be calculated by determining its top and bottom-end. The top-end of the ADC DR will be calculated as a function of antenna input signals, their crest factor, and the RF front-end selectivity. The gain of the receiver will be related to the maximum ADC input signal, and the maximum input swing possible within the ADC supply. The bottom-end of the ADC DR will be related to the modulation scheme, the wanted signal at sensitivity, the receiver and RF front-end noise figure, and the receiver gain. Furthermore, various performance parameters of the RF front-end like 1/f-thermal noise corner, NF, and IP2/3 will be related to the ADC 1/f corner, DR and IM2/3 respectively. The last part of this chapter describes an example of the performance parameter trade-offs between RF front-end and ADC for a GSM receiver.