A 90-nm CMOS Power Amplifier for 802.16e (WiMAX) Applications

In this paper, we demonstrate a single-stage 90-nm CMOS power amplifier (PA) for 2.3-2.7-GHz WiMAX (802.16e) band applications. An integrated balun is used to match the output to 50-Omega load. The PA gain and saturated power (P-SAT) are +18 and +32 dBm, respectively, working from a 3.3-V supply, with a peak power-added efficiency of 48%. A digital-predistortion technique is used to enhance the PA linearity. The measured error vector magnitude for a 64 quadrature amplitude modulation orthogonal frequency-division multiplexing signal is improved from -24 to -30 dB at +25-dBm output power. Compliance with the 802.16e standard 10-MHz WiMAX mask and Federal Communications Commission regulations is demonstrated at +25-dBm of output power with power efficiency of similar to 25% and with a measured second harmonic level of -31 dBm/MHz. Using a crest factor reduction technique, mask compliance is achieved at +27 dBm with tradeoff on EVM = -dB, sufficient for quadrature phase-shift keying.