A 29-to-57GHz AM-PM compensated class-AB power amplifier for 5G phased arrays in 0.9V 28nm bulk CMOS

Abstract

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

Load-Modulation-Based IMD3 Cancellation for Millimeter-Wave Class-B CMOS Power Amplifiers Achieving EVM < 1.2%

“…Using the detection bias voltage of the envelope detector (V det ), the load modulation can be configured to operate in three modes: 1) a conventional efficiency enhancement for a DPA; 2) the proposed IMD3 cancellation (LLPA); and 3) two standard class-B PAs whose loads are always equal to R opt and simply power-combined through the Doherty passive network. Moreover, two pMOS varactors at the input of the DA and PA improve the AM-PM profile, which was mainly set by nonlinear nMOS capacitors [4].…”

“…Four dominant IMD3 contributors are present in a CMOS PA: 1) the 3rd-order transconductance (g m3 ); 2) the gain compression due to drain voltage clipping; 3) the voltage-dependent nonlinear parasitic capacitors (e.g., gate-source C gs , gate-drain C gd , and gate-bulk C gb ); and 4) the 2nd-order mixing products. Enhanced 2nd-harmonic termination [2], [3], pMOS varactor-based amplitude-to-phase (AM-PM) compensation [4], [5], hybrid nMOS/pMOS PA structures [6]- [8], and transformer-based AM-PM correction [9] are proposed to improve the mm-wave PAs' linearity, deteriorated by the 2nd-order mixing products and nonlinear capacitors. Moreover, adaptive biasing, multi-gate transistor, and antiphase [10]- [18] techniques are proposed for IMD3 cancellation.…”

Dual‐mode linearity enhanced power amplifier with wideband AM‐PM compensation for 5–6‐GHz FeLAA applications

“…To realize broadband AM-PM compensation, the PMOS varactor was presented in [7]. This work presents a novel input matching network (IMN) for resolving the contradiction between AM-PM compensation and AM-AM compensation, resulting that the AM-PM distortion can be ameliorated in wideband operation without deteriorating the AM-AM.…”

Harmonic‐tuned high‐efficiency GaN power amplifier with precise AM‐AM and AM‐PM characteristics

“…In addition, it is important to consider the constraints of phase distortion, especially in targeting the nonlinearities of high-order complex modulation schemes. 7 Thus, parallelly combined GaN HEMTs with opposite magnitudes can be employed to minimize AM-PM distortion effects. 4,6 Besides, it is also shown in Alt et al 8 that additional care is needed for optimal input matching network (IMN) and supply voltage as these can also be the other sources of AM-AM and AM-PM distortions (AM/PM).…”