Digital-intensive analog circuits for highly-digitized RF receivers

In this paper, digital-intensive analog circuits suitable for nano-scale CMOS process are presented for highly-digitized RF receivers. Unlike conventional RF receivers that use voltage-domain analog-to-digital converters (ADCs), we review the use of time-domain ADCs that employ delay cells and flip-flops, such as voltage-controlled oscillator (VCO)-based ADCs. Examples of VCO-based ADCs used in direct conversion receiver and direct RF sampling receiver will be presented, together with digital-intensive circuit techniques to implement high-order filtering. In addition, the techniques for the VCO nonlinearity is investigated.