A WCDMA/WLAN Digital Polar Transmitter With Low-Noise ADPLL, Wideband PM/AM Modulator, and Linearized PA

This paper presents a single-chip digital-intensive polar transmitter for WCDMA and WLAN integrating a low-phase-noise all-digital phase-locked loop (ADPLL), a digitally-controlled wideband phase/amplitude modulator, and a calibration-free high-linearity power amplifier. From the ADPLL, the 1.7-2.5 GHz LO signal is generated together with a ÷1.5 frequency divider to eliminate DCO pulling. The phase noise of the ADPLL is optimized by using a linearized stochastic TDC with 3 ps resolution and a Class-C quadrature DCO (QDCO) with embedded quadrature phase shifter and quantization-noise filter. A 2-segment ΣΔ switching phase modulator enhances the PM bandwidth up to 200 MHz, and a digital polar amplifier employs AM-replica linearization to eliminate AM pre-distortion. The TX achieves a -1 dB output compression point of 22.8 dBm with an overall system efficiency of 27.6% and measures EVM of 4% for a 20 MHz 64-QAM signal at an output power of 13.8 dBm.