Passive Sigma-Delta Modulators with Built-in Passive Mixers for Mobile Communications

The push towards implementing radio receivers in a power efficient and cost-effective manner has led to the development of new circuits and architectures, especially for IF digitization. Conventionally baseband digitization is performed only after the second IF stage because of speed and power constraints imposed by the ADC. Pushing the analog/digital boundary to ever higher frequency allows more filtering functions (e.g. channel selection) to be performed digitally, which leads to further simplification of system, reduction of power consumption, higher degree of integration and lower cost.