Stephan Leuschner

9.2 A single-chip HSPA transceiver with fully integrated 3G CMOS power amplifiers

The increasing complexity and cost pressure of advanced radios for mobile communication devices dictates further integration of front-end components into the transceiver (TRX) in order to reduce bill-of-material (BoM), printed-circuit-board (PCB) area and system cost. In [1] a fully-digital polar modulator is presented, which enables a SAW-less 2G/3G transmitter, in particular by solving the transmitter (TX) noise in receive (RX) band issues at various duplex distances (45/80/190/400MHz). Removing the TX SAW filter by adopting innovative transmitter topologies not only reduced the amount of external components, but also paved the way for monolithic power amplifier (PA) integration into the CMOS transceiver IC. This step poses additional challenges in terms of RX-TX cross-talk, self-heating and remodulation (unwanted frequency modulation of local oscillator by modulated output signal, very critical in IQ direct modulators, much less pronounced in polar modulators). The first integration of a PA with external matching network into a TRX SoC product has been presented in [2] for DECT cordless phones using GFSK modulation. PAs are also successfully integrated into a Wi-Fi TRX SoC, delivering linear transmit power up to 22dBm [3]. Following these earlier examples, this work proposes to fully integrate a PA capable of delivering more than 0.5W of linear RF power for the demanding 3G cellular applications.

13.2 A digital multimode polar transmitter supporting 40MHz LTE Carrier Aggregation in 28nm CMOS

The evolving trend for increasing data rates in cellular communication systems with limited and fragmented frequency spectrum requires enhanced spectral efficiency of todays and future communication standards. The resulting need for high-order modulation schemes with large peak-to-average power ratio results in stringent requirements on in-channel linearity and SNR. At the same time FDD operation in SAW filter-less designs enforces very demanding limits for out-of-band and spurious emissions. Digital polar TX concepts have demonstrated low power consumption combined with low out-of-band noise in moderate bandwidth applications like WCDMA [1]. However, the implementation of 4G wideband polar systems with 20MHz RF bandwidth and above is very challenging due to the nonlinear conversion from cartesian to polar coordinates extending the effective signal bandwidth even further. A digital quadrature TX concept with up to 80MHz bandwidth, low EVM and moderate power efficiency has been shown in [2]. More than 30% power-added efficiency has been demonstrated in a 20MHz polar TX based on a switched-capacitor digital PA [3]. However, [2,3] suffer from low resolution and limited out-of-band noise performance.