A 2TX supply modulator for envelope-tracking power amplifier supporting intra- and inter-band uplink carrier aggregation and power class-2 high-power user equipment

Abstract

Uplink carrier aggregation (UL-CA) and high-power user equipment (HPUE) are proposed in the recent 3GPP standard [1]. UL-CA increases data-rate by aggregating intra-or inter-band carriers, and requires a supply modulator (SM) IC to generate two independently modulated supply voltages for the separate transmitter (TX) paths. Power Class 2, a new HPUE standard intended for TD-LTE Band41, allows 26dBm output power, which is 3dB higher than typical Power Class 3. To achieve 26dBm output, an SM must provide an RF power amplifier (PA) with larger current and boosted voltage above battery range. However, conventional Sm-ICs support only Power Class 3 PAs with intra-band contiguous CA up to 40MHz bandwidth in an envelope-tracking (ET) operation [2]. In order to support non-contiguous intra- and inter-band CA, a typical ET system needs two SMs with double the external components, occupying great PCB area in a cellular handset. This paper presents a single-chip SM-IC with two independently controlled TX outputs supporting Power Class 2. In this way, the SM-IC saves the BOM cost and the PCB area while achieving high system-power efficiency and low receiver-band noise.