A 28-/37-/39-GHz Linear Doherty Power Amplifier in Silicon for 5G Applications

Abstract

This paper presents the first multiband mm-wave linear Doherty PA in silicon for broadband 5G applications. We introduce a new transformer-based on-chip Doherty power combiner, which can reduce the impedance transformation ratio in power back-off (PBO) and thus improve the bandwidth and power-combining efficiency. We also devise a "driver-PA codesign" method, which creates power-dependent uneven feeding in the Doherty PA and enhances the Doherty operation without any hardware overhead or bandwidth compromise. For the proof of concept, we implement a 28/37/39-GHz PA fully integrated in a standard 130-nm SiGe BiCMOS process, which occupies 1.8mm 2 . The PA achieves a 52% −3-dB small-signal S21 bandwidth and a 40% −1-dB large-signal saturated output power (Psat) bandwidth. At 28/37/39GHz, the PA achieves +16.8/+17.1/+17-dBm Psat, +15.2/+15.5/+15.4-dBm P1dB, and superior 1.72/1.92/1.62 times efficiency enhancement over class-B operation at 5.9/6/6.7-dB PBO. Moreover, the PA demonstrates multi-Gb/s data rates with excellent efficiency and linearity for 64QAM in all the three 5G bands. This PA advances the state of the art for Doherty, wideband, and 5G silicon PAs in mm-wave bands. It supports drop-in upgrade for current PAs in existing mm-wave systems and opens doors to compact system solutions for future multiband 5G massive MIMO and phased-array platforms.

A 28 GHz Linear Power Amplifier Based on CPW Matching Networks with Series-Connected DC-Blocking Capacitors

“…The PA fabricated in 90 nm SOI CMOS technology demonstrates a high linearity and a relatively compact size. The small signal gain and the saturated output power are comparable with [5,6,13]. The peak PAE of the developed PA is partly limited by the adopted class-A operation mode.…”

“…A great deal of efforts has been made by researchers to get an accurate model of lumped inductors and metal-insulator-metal (MIM) capacitors for the Mm-Wave PAs in CMOS technology is well suited for fully integrated 5G phased array transceivers due to low cost and high integrity. To date, significant progress in this field has been made [5][6][7][8][9]. However, the high substrate-induced loss is still a critical challenge for mm-Wave circuits in bulk Si CMOS, which limits the gain and the power efficiency of the PA [6].…”

“…Because of the wide available bandwidth, the mm-Wave technique will play a key role in these emerging demands to achieve multi-gigabit-per-second data rates [1][2][3]. Figure 1a shows the spectra proposed by different regions in the world for 5G service, and frequency bands allocated around 28 GHz are one of the most promising candidates [4,5]. Moreover, the spectral efficiency and link range can be further improved by massive multiple-input multiple-output (MIMO) and phased array techniques.…”

“…In Reference [5] and [6], the K-band matching networks are designed by transformers and metal-oxide-metal (MOM) capacitors, and the capacitors are carefully simulated and measured to evaluate the influence. The coplanar waveguide (CPW) technique with DC-blocking capacitors only is widely used in mm-Wave applications [12][13][14][15].…”

A broadband Doherty power amplifier based on the two-port networks method

“…With the development of wireless communication technology, the amount of data transmitted is greatly increasing. Therefore, high peak-to-average modulation signals are often used to improve data transmission capacity [1,2,3,4,5]. Traditional power amplifiers (PAs) often only maintain high efficiency at saturation, and are not suitable for amplifying the high peak-to-average ratio signals [6,7,8,9,10].…”