A Wideband Energy-Efficient Multi-Mode CMOS

Abstract

This article presents a wideband, energy-efficient digital transmitter (DTX) suitable for multi-mode/multi-band wireless communication applications. It features various oper- ation modes comprising Cartesian (Modes-1/-2) and multi-phase (Modes-3/-4) configurations utilizing LO clocks with different duty cycle in the interleaving/non-interleaving configurations. The multi-phase operation compromises polar and Cartesian features by mapping the I/ Q signals into two non-orthogonal basis vectors with a 45 ◦ relative phase difference and a 3-bit phase selector scheme. The different operation modes are exten- sively analyzed and compared. Fabricated in a 40-nm CMOS process with an off-chip matching network, the proposed DTX occupies a core area of 0.72 mm 2 and delivers 23.18-dBm RF peak power at 2.1 GHz from a 0.95-V supply voltage with drain/system efficiencies of 66.26%/52.59%, respectively. Utilizing a simple memory-less digital pre-distortion (DPD) for a 160-MHz four-channel 64-quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) sig- nal, the DTX delivers an average P Out of 13.5/11.4/7.7/9.4 dBm, achieving an adjacent channel leakage (power) ratio (ACL(P)R) of better than −42/−40/−40/−38 dBc and an average error vector magnitude (EVM) of −36/−34/−34/−32 dB, operating in Modes-1/-2/-3/-4, respectively. While transmitting a 200-MHz single-channel 256 (1024)-QAM OFDM signal at 2.4 GHz in Modes-1/-4, the average delivered output power is 14.11/9.29