Third Order Non Linear Distortion from Modulated Blockers in WCDMA Receivers

In WCDMA receivers third order non-linear distortion due to inter-modulation between the leaked transmitter (TX) signal and external blockers can be quite significant. Previous published work has qualitatively shown that the distortion noise increases with increase in the number of physical channels in the leaked transmitter signal as well as the modulated blocker signal. However the exact quantitative relation between the distortion noise and the number of channels has not been derived. In a recent work by us, a quantitative formulation between the exact number of channels in the transmitter and blocker signals and the distortion noise was derived. This quantitative formulation was supported with theoretical proof and time-domain simulation results. In this paper we report results of measurement of third order distortion noise on a WCDMA receiver chip, which matches well with the quantitative formulation.