LOW IF Receiver


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the low-IF or digital IF receiver. A low-
IF receiver downconverts the desired spectrum directly from RF to some very low-IF
(typically < few 10s of MHz). The advantages of using a low-IF over a zero-IF is that this eliminates the issues of DC offsets and reduces susceptibility to 1/f noise. Low- IF receivers can also be highly integrated, since filtering can be done on-chip while maintaining high performance . In addition, the down converted spectrum is at a low enough frequency that it can be easily sampled by low-power analog-to-digital converters (ADC), and is thus also known as digital IF. The spectrum may then be converted to baseband using digital signal processing (DSP). However, with low-IF receivers, as with heterodyne receivers, comes the issue of image rejection. Due to the difficulties in achieving sharp-cutoff analog BPFs with low-power consumption for image rejection, designers have pursued image-cancelling architectures. Two popular image-cancellation receivers are the Hartley and Weaver architectures.




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