LOW-IF TOPOLOGIES FOR HIGH-PERFORMANCE ANALOG FRONT-ENDS OF FULLY INTEGRATED RECEIVERS

When it comes to integratability, the zero-intermediate frequency (IF) receiver is an alternative for the heterodyne or IF receiver, In rece nt years, the zero-IF receiver has been introduced in several applicat ions, but its performance cannot be compared to that of the TP receive r yet, This lower performance is closely related to its baseband opera tion, resulting in filter saturation and distortion, both caused by DC -offsets and self-mixing at the inputs of the mixers, The low-IF recei ver has a topology which is closely related to the zero-IF receiver, b ut it does not operate in the baseband, only near the baseband, The co nsequences are that, as for the zero-IF receiver, the implementation o f a low-IF receiver can be done with a high degree of integration, how ever, its performance can be better, in. this paper, the fundamental p rinciples of the low-IF receiver topology are introduced. Different lo w-IF receiver topologies are synthesized and fully analyzed in this pa per, This is done by applying the complex signal technique-a technique used in digital applications to the Study of analog receiver front en ds.