Analysis of Third-order Intermodulation in Receiver Down-Converter Employing Multiband Feedback

This paper presents an analysis of the third-order intermodulation characteristics of a recently reported receiver down-converter with multiband feedback and current reuse. This design not only achieves very a high gain with a low-current requirement but also provides an inherent cancellation mechanism for enhancing the linearity of the topology. By employing the signal feedback scheme, the inherent second-order nonlinearity of the tail current sources of differential pairs that are used to provide gain at baseband can be used to cancel the third-order intermodulation distortion resulting from the same devices. Circuit simulation using 0.13-μm RF CMOS process shows an IIP3 improvement of 4 dB in comparison to its normal cascaded counterpart.