Abstract-This paper presents a 29-to-57GHz (65% BW) AM-PM compensated class-AB power amplifier tailored for 5G phased arrays. Designed in 0.9V 28nm CMOS without RF thick top metal, the PA achieves a Psat=15.1dBm±1.6dB and │AM-PM│<1° from 29-to-57GHz, with a peak PAE of 24.2%. Techniques are studied to realize the required load impedance and distortion cancellation over the wide band of operation, while allowing 2-way power combining to further increase the delivered POUT. The very low AM-PM distortion of the realized PA enables up to 10.1, 8.9, 5.9dBm average POUT while amplifying a 1.5, 3, 6Gb/s 64-QAM respectively at 34GHz with EVM/ACPR better than -25dBc/-30dBc, without any digital pre-distortion.Index Terms-5G mobile communication, power amplifiers, AM-PM, broadband, wideband, coupled resonators, gain-bandwidth product, GBW, mm-Wave, CMOS.
I. INTRODUCTIONThe frequency spectrum above 24GHz will be a key enabler for future Gb/s fifth generation (5G) wireless communication systems [1,2]. To maximize the data rate, high order modulation schemes (e.g. 64-QAM) with large RF bandwidth (>100MHz) will be adopted. At the transmitter side, this implies several design challenges. 1) A wideband PA is needed to cover several channels, amplify wideband signals and ensure robust performance against PVT variations. 2) Modulated signals with high spectral efficiency show large peak-to-average-powerratio, challenging the linearity vs. efficiency trade-off for a given average P OUT . 3) Digital pre-distortion is not easily applicable when several PAs are integrated in an array [1]. Therefore, techniques to compensate AM-PM distortion over a large bandwidth are desirable to improve both inband and out-of-band linearity (i.e. EVM and ACPR).Recently, the work in [1] has shown the feasibility of 28GHz CMOS PAs with outstanding efficiency. However, the BW, average P OUT and ACPR under modulated signal considerably limit the achievable link distance and coexistence with adjacent channels. 2
