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Future handsets will employ uplink carrier aggregation to increase transmit data rates. This can lead to significant receiver desensitization for a number of LTE band combinations, because of the cross-modulation products created by the nonlinearity of antenna switches and duplexers in the RF front end. To mitigate this effect, an all-digital cancellation algorithm is proposed that relies solely on the digital representation of the signals, a peak covariance search for time alignment, and an adaptive distortion canceller. The recursive least squares (RLS) algorithm is used to find the optimal coefficients for the adaptive filter. Employing the distortion canceller improved the signal-to-interference-plus-noise ratio (SINR) and error-vector-magnitude (EVM) of the desired received signal by up to 20 dB.

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Future handsets employing uplink carrier aggregation to increase transmit data rates will experience severe degradation in receiver sensitivity due to intermodulation products created by the nonlinearity of switches and duplexers in the RF front end for a number of LTE band combinations. To maintain the same receiver sensitivity an all-digital cancellation algorithm is proposed that relies solely on the digital representation of the signals, a peak covariance search for time alignment, and a recursive least squares (RLS) adaptive filter. This technique provides up to 20 dB improvement of signal-tointerference-plus-noise ratio (SINR), for 5-MHz LTE signals.Index Terms -adaptive filters, least mean square, intermodulation distortion, uplink carrier aggregation.

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