Title :
A Sub-mW All-Digital Signal Component Separator With Branch Mismatch Compensation for OFDM LINC Transmitters
Author :
Chen, Tsan-Wen ; Tsai, Ping-Yuan ; Yu, Jui-Yuan ; Lee, Chen-Yi
Author_Institution :
Dept. of Electron. Eng. & Inst. of Electron., Nat. Chiao-Tung Univ., Hsinchu, Taiwan
Abstract :
Linear amplification with nonlinear components (LINC) is an attractive technique for achieving linear amplification with high efficiency. This paper presents a sub-mW all-digital signal component separator (SCS) design for OFDM LINC transmitters, including a phase calculator and a digital-control phase shifter (DCPS) pair. In addition, a digital mismatch compensation scheme is proposed and integrated into the SCS to reduce the design complexity of the power amplifier. This chip is manufactured in a 90 nm standard CMOS process with an active area of 0.06 mm2. The DCPS can generate phase-modulated signals at 100 MHz with 8-bit resolution and RMS error 9.33 ps (0.34°). The phase calculation can be performed at a maximum speed of 50 MHz using a 0.5 V supply voltage, resulting in a 73.88% power reduction. Comparing to state-of-the-art, the power consumption of the overall SCS is only 949.5 μW which minimizes the power overhead for an LINC transmitter. This SCS with the branch mismatch compensation provides a 0.02 dB gain and 0.15° phase fine-tune resolution without adding additional front-end circuits. Considering 1 dB gain and 10° phase mismatch, the system EVM of - 29.81 dB and ACPR of - 34.56 dB can still be achieved for 5 MHz bandwidth 64-QAM OFDM signals.
Keywords :
CMOS digital integrated circuits; OFDM modulation; low-power electronics; nanoelectronics; power amplifiers; source separation; transmitters; OFDM LINC transmitters; OFDM signals; branch mismatch compensation; digital mismatch compensation scheme; digital-control phase shifter pair; frequency 5 MHz to 100 MHz; phase calculator; phase-modulated signals; power 949.5 muW; power amplifier; power consumption; standard CMOS process; sub-mW all-digital signal component separator; voltage 0.5 V; Baseband; Calculators; Delay; Digital signal processing; Gain; OFDM; Transmitters; Branch imbalance; LINC; OFDM; SCS; efficiency; mismatch; outphasing;
Journal_Title :
Solid-State Circuits, IEEE Journal of
DOI :
10.1109/JSSC.2011.2164133