OFDM Transform-Domain Receivers for Multi-Standard Communications
Digital deep-submicron CMOS architectures for wideband receivers are highly desirable for their flexibility, scalability, and programmability properties. However, while these technologies aid digital circuit design, they make more difficult the design of conventional analog circuits. Hence, there is a need to shift the complexity to the digital domain. This requires either front-end topologies where the analog-to-digital converter (ADC) is close to the antenna or analog circuit schemes that are intensively digital. Pushing the ADC toward the antenna imposes very high tracking bandwidths and dynamic ranges which become prohibitively area- and power-expensive in wideband applications. On the other hand, digital-intensive radio-frequency (RF) front ends not only take advantage of deep-submicron CMOS but also relax the ADC requirements. At this end, successful examples of narrowband digital RF front ends have been reported in , where switched Gm-C filters and passive switched capacitor circuits are used to implement charge-sampling finite and infinite impulse response (FIR and IIR) filters in a narrowband direct RF-sampling receiver with built-in antialiasing for GSM and Bluetooth standards. A bank of this circuit topology has been proposed to address multi-narrowband standards . However, receivers that can cope as well with ...