A Highly Linear Wideband Polar Class-E CMOS Digital Doherty Power Amplifier

Abstract

This paper presents the first application of a digital-intensive intrinsically linear digitally-controlled class-E technique in a Doherty configuration. By careful nonlinear segmentation and multiphase RF-clocking along with overdrive-voltage control and automatic duty-cycle correction, it is shown that even the nonlinearities related to Doherty operation can be fully handled by the underlying design such that digital predistorion DPD can be in principle omitted. The nonlinearity behaviour of the whole digital Doherty PA is analyzed and closed-form equations are given to predict the AM-AM and AM-PM curves. In addition, time/phase mismatch between the Peak and Main branches and the AM and PM signals are accurately compensated. In order to achieve maximum intrinsic linearity, two separate chips with the same architecture, but different design parameters, are fabricated as the Main and Peak amplifiers in 40nm bulk CMOS. To achieve a large RF bandwidth and high passive combiner efficiency, a differential low-loss, wideband Marchand balun-based Doherty power combiner, implemented using re-entrant coupled lines with independent 2 nd harmonic control is proposed, and together with the matching network is fabricated on a two-layer PCB. The measured peak / 6 dB power-back-off P OUT , drain efficiency / power-added efficiency at 2.4 GHz are 17.5 / 12.2 dBm, 57 / 52 % and 36 / 25 % with VDD Main / Peak = 0.6 / 0.7 V. Measured results without using DPD show-41 dBc ACPR and-36 dB EVM for a 16 MHz OFDM signal at 2.5GHz. By using DPD, the measured ACPR and EVM of a 16 / 32 MHz OFDM signals are-52 /-48 dBc and-50 /-48 dB respectively.

A Wide-Band High-Gain Doherty Power Amplifier With Class-AB HEMT Amplifiers

“…/Pdc]*100 (7) DE(%)= (Pout(W) )/Pdc)*100 (8) With Compared the results of the schematic test and the Layout test of the DPA, it is clear that there has always been some loss in the circuit, which has led to a decrease in the Layout test parameters compared to the schematic test results, which is due to losses of ideal devices, RF frequency and stress voltages.…”

“…DPAs by different circuit structure, such as hybrid [6] or multi-way circuits [7], also increase output power and efficiency. The use of switching mode PAs [8] in the position of the main PA is often seen in articles in this field that have improved PA performance. It should be noted that switching mode amplifiers, due to their switching performance, add to the non-ideal circuit conditions, because the existence of non-zero transistor time and non-zero resistance, etc.…”

Studies on Selected Topics in Radio Frequency Digital-to-Analog Converters

“…Digital power amplifiers that combine the analog conversion and the power amplification, are also one of the interesting areas for the RF DAC topic and it has recently received attention [13,53]. Although, the current state-ofthe-art in this direction can provide watt-level RF output power and seems very challenging for wide-area and macro classic base stations, in a centralized massive MIMO design, where the total output RF power is divided to the total number of antenna elements, it can be an interesting solution, particularly due to its integration capability in a large-scale massive MIMO.…”

Millimeter-Wave Quadrature Mixed-Mode Transmitter With Distributed Parasitic Canceling and LO Leakage Self-Suppression

“…The DPA operating at the switching mode features high efficiency. The high-efficiency DPAs are usually developed for sub-6 GHz in recent year [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39]. The current-mode DPAs based on Class-E [24], [25] and inverse Class-D [26], [27] are reported with high efficiency.…”

“…The high-efficiency DPAs are usually developed for sub-6 GHz in recent year [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39]. The current-mode DPAs based on Class-E [24], [25] and inverse Class-D [26], [27] are reported with high efficiency. However, current-mode DPA introduces significant AM-AM and AM-PM distortions, which requires the digital pre-distortion (DPD) for linearity enhancement.…”