An integrated closed-loop polar transmitter with saturation prevention and low-IF receiver for quad-band GPRS/EDGE

This paper describes a 2.5G cellular transceiver with standard DigRF interface, implemented in a low-cost 0.13mum CMOS process. This is the first CMOS single-chip, polar closed-loop transmitter, excluding the power amplifier (PA). This transmitter achieves an efficiency of 26% in EDGE mode by linearizing a saturated PA in a closed-loop feedback system. This is much higher than the typical 15-to-18% efficiency of systems using a linear PA. Typical high-band/low-band performance of -62/-64Bc in 30 kHz for 400 kHz offset spectral mask and 1.4/1.7% EVM in EDGE mode are significantly better than those reported earlier. Using a low-noise quadrature mixer topology, the receiver, including T/R switch and SAW filters, achieves a sensitivity of -110 dBm. The RF solution, consisting of PAs in a multi-chip integrated antenna switch module, SAW filters with integrated matching components and the transceiver is the smallest form factor available in the market today.