WCDMA cross modulation effects and implications for receiver linearity requirements

Cross modulation is an important effect in mobile handsets used in both CDMA and WCDMA systems. The full duplex operation of these systems requires that the transmitter and the receiver operate simultaneously. When a handset is operating at maximum distance from the base station within a given cell, the high transmitter output power necessary to communicate with the distant base station is in direct conflict with the receiver operating at maximum sensitivity. The transmitter leakage power through the duplexer is usually significantly higher than the desired signal channel through the first few elements of the receiver. As a result, the transmitter leakage becomes the dominating effect for nonlinearities for the first LNA (low noise amplifier) in the receiver chain. This paper focuses on the effects of cross modulation in a WCDMA system.