Digital front-end design for carrier aggregation in next-generation cellular user equipment

Carrier aggregation (CA) in latest 4G standards and beyond demands either multiple narrow-band RX branches or a single wide-band RX branch followed by efficient channelizer architectures in the digital front-end (DFE). The small number of simultaneously received component carriers favors the use of a single wide-band ADC in conjunction with a per-channel carrier extraction. However, the computational complexity of the digital extraction is high due to the mixing operation for each of the aggregated carriers. In this work, we show how the complexity of the per-channel approach can be reduced by employing DFE architectures using cascaded integrator comb (CIC) based filter stages. Promoting a joint configuration approach for the ADC and subsequent filter stages, the different low-complexity filter architectures are analyzed, evaluated and compared. By an LTE-Advanced non-contiguous CA design example, the feasibility of the addressed designs is demonstrated and the approach with the best performance-complexity trade-off is identified.