A 70 MHz CMOS band-pass sigma-delta analog-to-digital converter for wireless receivers

Analog-to-digital converters play an essential role in modern RF receiver design. Conventional Nyquist converters require analog components that are precise and highly immune to noise and interference. In contrast, oversampling converters can be implemented using simple and high-tolerance analog components. Moreover, sampling at high frequency eliminates the need for abrupt cutoffs in the analog antialiasing filters. A technique of noise shaping is used in Σ∆ converters in addition to oversampling to achieve a high-resolution conversion. A significant advantage of the method is that analog signals are converted using simple and high-tolerance analog circuits, usually a 1-bit comparator, and analog signal processing circuits having a precision that is usually much less than the resolution of the overall converter. In this thesis, a technique to design the Σ∆ converters for 70 MHz will be described. Impulse-invariant-transformation is used to transform a discrete-time (z-domain) loop-filter transfer function into continuous-time (s-domain). The continuous-time loop-filter is then implemented using a transconductor-capacitor filter. A latched-type

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