Differential source-pull on the WCDMA receiver

A practical approach to source-pull differential input LNA is presented using a single-ended RF tuner adapted by a balun. The adaptation only considers balun's differential mode S-parameters for the reference plane extension. Error analysis on neglecting common mode S-parameters provides guidelines to choose proper balun for better adaptation accuracy: a) higher common-mode rejection ratio, b) less reflection on the unbalanced port and c) less insertion loss. The approach is applied to the NF optimization on a cellular WCDMA receiver. The resultant source pull estimation correlates well with the final optimal matching network. The minimum NF is achieved at 2.3dB.