Millimeter-wave Power Amplifier Research Articles

RF circuit techniques for transition to 5G advanced

Abstract Worldwide adoption of 5G mobile devices has been one of the main driving engines behind semiconductor industry. Since the initial release in 2020, 5G-enabled devices have surpassed the market penetration of 3G/4G smartphones. 5G brings higher data capacity, low latency, and new applications. These are possible due to lower feature nodes such as FinFET 3 nm/5 nm but also due to improvements of the 5G radio frequency (RF)front-end circuitry. This paper presents 5G RF front-end architectures with novel circuits and measurement details which will be part of future 5G advanced and 6G mobile devices and are easier to be controlled using digital circuitry. The paper presents an envelope-controlled power amplifier (PA) principle, along with a novel simplified calibration architecture designed for 5G/5G+ operating under 6 GHz, as well as for frequency range 2 millimeter-wave PAs. An earlier version of this paper was presented at the 2023 53rd European Microwave Conference and was published in the Proceedings [Balteanu F, Thoomu K, Pingale A, Venimadhavan S, Sarkar S, Choi Y, Modi H, Drogi S, Lee J and Agarwal B (2023) Enabling RF circuit techniques for 5G and beyond In 53rd European Microwave Conference (EuMC), Berlin, Germany, 22–25].

Millimeter-Wave GaAs Ultra-Wideband Medium Power Amplifier and Broadband High-Power Power Amplifier for 5G/6G Applications

Millimeter-Wave GaAs Ultra-Wideband Medium Power Amplifier and Broadband High-Power Power Amplifier for 5G/6G Applications

A Linear Millimeter-Wave GaN MMIC Doherty Power Amplifier With Improved AM-AM and AM-PM Characteristics

A Linear Millimeter-Wave GaN MMIC Doherty Power Amplifier With Improved AM-AM and AM-PM Characteristics

Deep-Learning-Based Inverse-Designed Millimeter-Wave Passives and Power Amplifiers

Deep-Learning-Based Inverse-Designed Millimeter-Wave Passives and Power Amplifiers

A Wideband Power Amplifier in 65 nm CMOS Covering 25.8 GHz–36.9 GHz by Staggering Tuned MCRs

Broadband millimeter-wave power amplifiers have attracted much attention and have wide applications for 5G communication, satellite communication, radar, sensing, etc. Yet, it is challenging to design a power amplifier with broadband small-signal gain and power performance simultaneously. In this study, a transformer-based symmetrical magnetically coupled resonator (MCR) matching network for broadband output matching and stagger-tuned MCRs are used to achieve both broadband small- and large-signal performance. Also, to enhance the gain for the power amplifier, a three-stage common-source pseudo-differential structure is adopted to mitigate the low-gain issue due to stagger tuning, and the shunt resistors aimed to decrease the Q factor of the MCRs. We used the in-phase two-way current combined with microstrip transmission lines to increase the output power. Designed in 65 nm bulky CMOS technology, the power amplifier presents a 3 dB small-signal gain bandwidth from 25.8 GHz to 36.9 GHz, indicating a peak gain of 25.87 dB at 30.5 GHz. The power amplifier demonstrates a 17.84 dBm saturated output power (Psat) at 31 GHz and a 24.37% peak power added efficiency (PAEmax) at 28 GHz. The power amplifier achieves a flat Psat of 17.44 ± 0.4 dBm, a PAEmax of 22.59 ± 1.78%, and an OP1dB of 13.78 ± 0.31 dBm from 26 GHz to 36 GHz.

A Coupler Balun Load-Modulated Power Amplifier With Extremely Wide Bandwidth

Next-generation millimeter-wave (mm-Wave) power amplifiers (PAs) need to support multistandard communication systems with wide bandwidth, complex modulation, and high energy efficiency. Most existing mm-Wave PA architectures with power backoff (PBO) efficiency enhancement, such as Doherty and outphasing PAs, typically only support limited carrier bandwidth. In this work, we propose and demonstrate that a 180° coupler balun structure can serve as an extremely wideband active load modulation network for broadband PBO efficiency enhancement and further realize a coupler balun load-modulated PA (CBMA). Moreover, compared to load-modulated balanced amplifiers (LMBAs), the proposed CBMA supports natural single-ended-to-differential balun conversion, differential power cells, and wideband capacitive neutralization, ideal for integrated mm-Wave PAs. Furthermore, we propose a continuous-mode CBMA operation with role exchanges to attain a nearly 3:1 carrier bandwidth. A prototype CBMA is designed and fabricated in a 45-nm RF CMOS SOI process, which achieves an OP1 dB PAE of 39.9%–20.4% with OP1 dB of over 21.6–18.3 dBm from 26 to 60 GHz. The PA also achieves a 32.8%–13.4% 6-dB PBO (from OP1 dB) efficiency with its best <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.75\times /3.51\times $ </tex-math></inline-formula> efficiency enhancement over an ideal Class-B/-A PA. Using a single-carrier 64-QAM signal with 0.5 GSym/s (3 Gb/s), the PA supports an average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {out}}$ </tex-math></inline-formula> of 15.8–11.3 dBm with an average PAE of 27.15%–8.58% with −23-dB rms error vector magnitude (EVM) over 26–60 GHz. The PA also supports 5G NR modulation using 5G new radio (NR) FR2 200-MHz 1-CC 64-QAM signals, achieving 18.22%–6.55% average PAE at 10.72–7.1-dBm average <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm {out}}$ </tex-math></inline-formula> with rms EVM of −23 dB over 26–60 GHz.

PACOSYT: A Passive Component Synthesis Tool Based on Machine Learning and Tailored Modeling Strategies Towards Optimal RF and mm-Wave Circuit Designs

In this paper, the application of regression-based supervised machine learning (ML) methods to the modeling of integrated inductors and transformers is examined. Different ML techniques are used and compared to improve accuracy. However, it is demonstrated that none of the ML techniques considered provided good results unless a smart modeling strategy, tailored to the specific design problem, is used. Taking advantage of these modeling strategies, high accuracy can be obtained when compared to full-wave electromagnetic (EM) simulations (less than 2% error) and experimental measurements (less than 5% error). The most accurate model, obtained by the appropriate combination of an ML technique and modeling strategy, has been integrated into a tool called PACOSYT. The tool uses optimization algorithms to allow the designer to obtain an inductor/transformer with optimal performances in just seconds while keeping the accuracy of EM simulations. Furthermore, the tool provides the passive component S parameter description file for seamless use in circuit simulations. The tool can be used standalone or integrated with design frameworks, like Cadence Virtuoso or AIDASoft, a framework for circuit optimization. To illustrate the different usages of the tool, several passive devices are synthesized, and hundreds of millimeter-wave power amplifiers are synthesized using AIDASoft together with PACOSYT. The tool has been developed using open-source Python frameworks and does not use any closed-source licenses. PACOSYT, which also allows other designers to create their models for different technologies, is made publicly available.

Record RF Power Performance at 94 GHz From Millimeter-Wave N-Polar GaN-on-Sapphire Deep-Recess HEMTs

In this article, N-polar GaN-on-sapphire deep-recess metal–insulator–semiconductor (MIS)-high-electron-mobility transistors (HEMTs) with a breakthrough performance at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${W}$ </tex-math></inline-formula> -band are presented. Compared with prior N-polar GaN MIS-HEMTs, a thin GaN cap layer and atomic layer deposition (ALD) ruthenium (Ru) gate metallization were used along with high-quality GaN-on-sapphire epitaxy from Transphorm Inc. Before SiN passivation, 94 GHz large signal load–pull shows that the transistor obtains a record-high 9.65 dB linear transducer gain and demonstrated 42% power-added efficiency (PAE) with associated 4.4 W/mm of output power density at 12 V drain bias. By biasing the drain at 8 V, the device shows an even higher PAE of 44% with an associated 2.6 W/mm of output power density. After SiN passivation, the fabricated N-polar GaN-on-sapphire HEMTs show a high PAE of 40.2% with an associated 4.85 W/mm of output power density. Furthermore, a very high output power density of 5.83 W/mm with 38.5% PAE is demonstrated at a 14 V drain bias. This power performance shows significant efficiency improvement over previous N-polar GaN-on-SiC and demonstrates a combined efficiency and power density beyond what has been reported for Ga-polar devices, in spite of the low-thermal-conductivity sapphire substrate. This shows that N-polar GaN-on-sapphire technology is an attractive candidate for millimeter-wave power amplifier applications with simultaneous high efficiency and power density.

A Wideband Balanced Amplifier Using Edge-Coupled Quadrature Couplers in 0.13-μm SiGe HBT Technology

In this work, a wideband millimeter-wave (mm-wave) power amplifier (PA) is reported. To provide excellent input/output impedance matching across broadband, sufficient output power and high power-added efficiency (PAE), a balanced amplifier (BA)-based architecture is used in designing this PA. In particular, an edge-coupled quadrature coupler is designed as its RF-power-division/combination block, and its performance in terms of magnitude/phase balance error is minimized throughout a relatively wide bandwidth. A PA prototype is fabricated in 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> SiGe HBT technology and tested. Under a 1.6-V power supply, the variation of small-signal gain is less than 3 dB within 20-40 GHz, which is equivalent to more than 66% fractional 3-dB bandwidth. Within this frequency range, at least 15.8 dBm saturated output power could be delivered with the peak PAE higher than 16.8%. The designed PA supports a single-carrier 200-MHz 64-quadrature amplitude modulation (QAM) with higher than 12.8-dBm average output power, while still maintaining an error vector magnitude (EVM) below −25 dB at 30 GHz. The size of the designed compact-size PA, including all pads, is only 0.7 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.3$ </tex-math></inline-formula> mm.

Stacked Common-Base vs Common-Emitter mmWave PA Cells and 68–105 GHz Broadband Asymmetrical PA in 250nm InP HBT

In this paper, we perform a comparative analysis between stacked common-emitter (SCE) and stacked common-base topologies (SCB) for high efficiency and broadband millimeter-Wave (mmWave) power amplifiers (PAs) in 250 nm InP-based heterojunction bipolar transistor (HBT) technology. We propose an analytical approach to design stacked PA cells accounting for complex load impedance and intra-matching between stacked transistors to allow optimal loadpull operation of both the devices in the stack. We demonstrate how SCB cell can allow higher gain, mitigated power and efficiency trade-off and linearity, when compared to more well-established SCE cells at higher mmWave frequencies. The designed SCB and SCE cells achieve a measured gain of 11.8 dB/6dB gain, 33%/34% peak PAE, 16.8%/14.5% PAE at 6-dB back-off, and Psat of 18.7 dBm/19.6 dBm at 90 GHz. The SCB PA demonstrates superior linearity, and achieves an EVM of 2.38% at 11.8-dBm average power supporting 3 Gbps 64-QAM. The SCB PA achieves 17.9-18.9-dBm Psat across 80–110 GHz and is one of the highest efficiency, broadband and linear PAs in W-band using InP technology. Utilizing the PA cells, we demonstrate an asymmetrical broadband power combining circuit for high efficiency combining across a large relatively bandwidth. The PA operates across a 68–105 GHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{sat,3dB}$ </tex-math></inline-formula> bandwidth with 21.5 dBm peak saturation power and 24% peak PAE.

Coupled Embedding Networks for 7-dB Gain-per-Stage at 130–140 GHz in a 20-dBm Gallium Nitride Power Amplifier

We propose a coupled embedding network (CEN) as a portable, robust design technique to simultaneously introduce gain boosting and loadline matching in millimeter-wave power (mm-wave) amplifiers (PAs). The approach uses directional couplers as an abstraction for the embedding network and produces straightforward design equations to achieve optimal input-stability margins for any specified gain. We demonstrate the design process and implementation using a 40-nm Gallium Nitride (GaN) process technology through simulated and measured performance of the PA with and without the embedding network. The output power is greater than 20 dBm and remains above 18 dBm over an 8 GHz bandwidth. Peak power added efficiency (PAE) is 6.5%. The 3-stage PA achieves 21 dB of gain at 137 GHz offering 7.1-dB gain per device. The measured gain is 8 dB higher than the common-emitter design with the same number of stages. To our knowledge, this is the highest gain per stage for a GaN PA in D-band.

Chebyshev Polynomial-LSTM Model for 5G Millimeter-Wave Power Amplifier Linearization

In this letter, a behavior model, namely CP- LSTM, composed of Chebyshev polynomials (CP) and a long short-term memory (LSTM) network is built to linearize the wideband millimeter-wave power amplifier (mmW PA) in the fifth-generation (5G) mobile communication system. In order to verify the linearization performance of the CP- LSTM predistorter, a 100-MHz bandwidth 5G new radio (5G NR) signal is employed to test the 28-GHz mmW PA under the text. Experimental results show that the adjacent channel power ratio (ACPR) of the mmW PA with the CP- LSTM can be improved by 20 dB which is 5-dB better than with the LSTM and 3-dB better than with the generalized memory polynomial (GMP). Therefore, the proposed CP- LSTM model is very effective to linearize 5G mmW PAs.

Broadband Millimeter-Wave 5G Power Amplifier Design in 22 nm CMOS FD-SOI and 40 nm GaN HEMT

Three millimeter-wave (mm-Wave) power amplifiers (PAs) that cover the key 5G FR2 band of 24.25 to 43.5 GHz are designed in two different state-of-the-art device technologies and are presented in this work. First, a single-ended broadband PA that employs a third-order input matching network is designed in a 40 nm GaN/SiC HEMT (High Electron Mobility Transistor) technology. Good agreement between the measurement and post-layout parasitic extracted (PEX) electromagnetic (EM) simulation data is observed, and it achieves a measured 3-dB BW (bandwidth) of 18.0–40.3 GHz and &gt;20% maximum PAE (power-added-efficiency) across the entire 20–44 GHz band. Expanding upon this measured design, a differential broadband GaN PA that utilizes neutralization capacitors is designed, laid out, and EM simulated. Simulation results indicate that this PA achieves 3-dB BW 20.1–44.3 GHz and maximum PAE &gt; 23% across this range. Finally, a broadband mm-Wave differential CMOS PA using a cascode topology with RC feedback and neutralization capacitors is designed in a 22 nm FD-SOI (fully depleted silicon-on-insulator) CMOS technology. This PA achieves an outstanding measured 3-dB BW of 19.1–46.5 GHz and &gt;12.5% maximum PAE across the entire frequency band. This CMOS PA as well as the single-ended GaN PA are tested with 256-QAM-modulated 5G NR signals with an instantaneous signal BW of 50/100/400/9 × 100 MHz at a PAPR (peak-to-average-power ratio) of 8 dB. The data exhibit impressive linearity vs. POUT trade-off and useful insights on CMOS vs. GaN PA linearity degradation against an increasing BW for potential mm-Wave 5G applications.

Broadband High-Efficiency Millimeter-Wave Power Amplifiers in 22-nm CMOS FD-SOI with Fixed and Adaptive Biasing

The design of broadband highly-efficient millimeter-wave (mm-Wave) Power Amplifiers (PA) in 22-nm CMOS FD-SOI (fully depleted silicon-on-insulator) is discussed. One design uses fixed biasing while the other utilizes an adaptive biasing network to improve its Power-Added-Efficiency (PAE) in power backoff. These designs aim to cover the key Fifth-Generation (5G) FR2 (Frequency Range 2) band (e.g., from 24.25 GHz to 43.5 GHz). In measurement, the PAs obtain very broadband 3-dB BW, ranging from 19.1 GHz to 46.5 GHz for the fixed-bias design and 18.8 GHz to 41.9 GHz for the adaptively biased design. The adaptively biased design is able to achieve enhanced output 1-dB compression point (OP1dB) and PAE@P1dB because of its adaptive biasing network. Measurements on the fixed-biased PA at 24/28/37/39 GHz yield max. PAE of 22.2/22.4/19.7/19.8%, and POUT,SAT of 14.9/15.3/14.7/14.7 dBm, with OP1dB of 11.8/11.6/12/11.6 dBm, and PAE@P1dB of 14.1/13.4/14.5/13.5%. Measurements on the adaptively biased PA at 24/28/37/39 GHz yield max. PAE of 20.1/15.2/10.3/7.9%, and POUT,SAT of 14.6/14.2/12.5/11.2 dBm, with improved OP1dB of 13.1/12.3/12.1/11.2 dBm, and PAE@P1dB of 19.1/14.4/10.3/7.9%. Data from body bias voltage VB on the PA performance is also presented. These measurement results are compared with post-layout parasitic-extraction (PEX) simulations, and also against other novel silicon broadband mm-Wave PAs in literature.

Millimeter-Wave Power Amplifier ICs for High Dynamic Range Signals

The next-generation 5G and beyond- 5G wireless systems have stimulated a substantial growth in research, development, and deployment of mm-Wave electronic systems and antenna arrays at various scales. It is also envisioned that large dynamic range modulation signals with high spectral efficiency will be ubiquitously employed in future communication and sensing systems. As the interface between the antennas and transceiver electronics, power amplifiers (PAs) typically govern the output power, energy efficiency, and reliability of the entire wireless systems. However, the wide use of high dynamic range signals at mm- Wave carrier frequencies substantially complicates the design of PAs and demands an ultimate balance of energy efficiency and linearity as well as other PA performances. In this review paper, we will first introduce the system-level requirements and design challenges on mm-Waves PAs due to high dynamic range signals. We will review advanced active load modulation architectures for mm-Wave PAs and power devices. We will then introduce recent advances in mm-Wave PA technologies and innovations with several design examples. Special design considerations on mm-Wave PAs for phased array MIMOs and high mm-Wave frequencies will be outlined. We will also share our vision on future technology trends and innovation opportunities.

A New GaN HEMT Small-Signal Model Considering Source via Effects for 5G Millimeter-Wave Power Amplifier Design

A new gallium nitride (GaN) high electron mobile transistor (HEMT) small-signal model is proposed considering source via effects. In general, GaN HEMTs adopt a source via structure to reduce device degradation due to self-heating. In this paper, the modified drain-source capacitance (Cds) circuit considering the source via structure is proposed. GaN HEMTs fabricated using a commercial 0.15 μm GaN HEMT process are measured with a 67 GHz vector network analyzer (VNA). The fabricated device is an individual source via (ISV) type. As a result, it is difficult to predict the measured S12 in the conventional small-signal model equivalent circuit. This causes errors in maximum stable gain/maximum available gain (MSG/MAG) and stability factor (K), which are important for circuit design. This paper proposes a small-signal equivalent circuit that adds the drain-source inductance to the drain-source capacitance considering the source via structure. The proposed equivalent circuit better reproduces the measured S12 without compromising the accuracy of other S-parameters up to 67 GHz and improves the accuracy of MSG/MAG and K. It is expected that the proposed model can be utilized in a large-signal model for 5G millimeter-wave GaN HEMT power amplifier design in the future.

A Yield-Improvement Method for Millimeter-Wave GaN MMIC Power Amplifier Design Based on Load—Pull Analysis

Process fluctuations can significantly affect the yield of millimeter-wave circuits based on submicrometer semiconductor processes. A yield-improvement design that incorporates passive circuits is well established. However, how to consider the process fluctuation in active circuit designs (e.g., power amplifiers) and improve yield is still a challenge. In this article, a yield-improvement load-pull design method, which can be used to find optimum load impedance accounting for high yield while maintaining good output performance, is presented. The yield-improvement load-pull theory is described using an analytical model of transistor large-signal performance considering the process fluctuation. A method of the yield-improvement load-pull for the practical microwave monolithic integrated circuit (MMIC) design is introduced in detail. For demonstration purposes, a high-performance Ka-band power amplifier MMIC is designed. The results show that with the proposed yield-improvement load-pull method, an obvious improvement of yield can be observed with only minimal sacrifice of the output power ( P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> ) and the power added efficiency ( η <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PAE</sub> ), respectively. As a result, the method of this article can be used to improve the yield of millimeter-wave/terahertz integrated circuits (ICs).

The Evolution of Manufacturing Technology for GaN Electronic Devices.

GaN has been widely used to develop devices for high-power and high-frequency applications owing to its higher breakdown voltage and high electron saturation velocity. The GaN HEMT radio frequency (RF) power amplifier is the first commercialized product which is fabricated using the conventional Au-based III–V device manufacturing process. In recent years, owing to the increased applications in power electronics, and expanded applications in RF and millimeter-wave (mmW) power amplifiers for 5G mobile communications, the development of high-volume production techniques derived from CMOS technology for GaN electronic devices has become highly demanded. In this article, we will review the history and principles of each unit process for conventional HEMT technology with Au-based metallization schemes, including epitaxy, ohmic contact, and Schottky metal gate technology. The evolution and status of CMOS-compatible Au-less process technology will then be described and discussed. In particular, novel process techniques such as regrown ohmic layers and metal–insulator–semiconductor (MIS) gates are illustrated. New enhancement-mode device technology based on the p-GaN gate is also reviewed. The vertical GaN device is a new direction of development for devices used in high-power applications, and we will also highlight the key features of such kind of device technology.

A High-Power Broadband Multi-Primary DAT-Based Doherty Power Amplifier for mm-Wave 5G Applications

Silicon-based millimeter-wave (mm-Wave) power amplifiers (PAs) with high power and high peak/back-off efficiency are highly desired to efficiently amplify multi-Gb/s 5G NR signals. This article presents a fully integrated high-power broadband linear Doherty PA with multi-primary distributed-active-transformer (DAT) power combining. We introduce a transformer-based impedance inverter for active load modulation and a multi-primary DAT structure for hybrid series and parallel power combining. Based on this, we propose a transformer-based Doherty combiner with more design freedom and a multi-primary DAT-based Doherty PA for simultaneous active load modulation and low-loss power combining. The EM simulation results demonstrate that the proposed DAT-based Doherty output network achieves very symmetric and balanced load impedances among all the main and auxiliary PA ports. As a proof of concept, a 24-30-GHz prototype PA is implemented in a 0.13- μm SiGe BiCMOS process. The PA achieves 30.4% PAE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> , 28.3-dBm P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> , 30.2% PAE at 26.8-dBm P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1 dB</sub> , and 21.2% PAE at 6-dB back-off from P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> at 28 GHz. Modulation measurement with single-carrier 64-QAM signals and 5G NR FR2 orthogonal frequency-division multiplexing (OFDM) signals has been demonstrated. For a 200-MHz 1-CC 5G NR FR2 64-QAM signal, the PA achieves 18.1-dBm P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> and 13.8% PAE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> with -25.1-dB rms EVM at 28 GHz.

A 24-29.5 GHz Voltage-Combined Doherty Power Amplifier Based on Compact Low-Loss Combiner

In this brief, a 24-29.5 GHz millimeter-wave (mm-wave) voltage-combined Doherty power amplifier (DPA) based on compact low-loss combiner is proposed for the fifth-generation (5G) applications. By maximizing the use of parasitic parameters in the circuit, a compact low-loss combiner is proposed to achieve the required impedance transformation with only one additional series capacitor. A detailed design procedure is also introduced in the brief. Based on the proposed combiner, a fully integrated Doherty PA is implemented in 0.13- μm SiGe BiCMOS process with a core area of only 0.29 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The DPA achieves a 27% -3-dB small-signal gain fractional bandwidth and a 15.9 dB small signal gain at the center frequency of 27 GHz. The -1-dB Psat bandwidth covers 24-29.5 GHz (20% fractional bandwidth), and the maximum output power is 20.8 dBm ± 0.4 dB. From 24 to 29.5 GHz, the designed DPA provides 23.2% to 28.4% power-added efficiency (PAE) at saturated output power, and 18.3% to 21.9% PAE at 6 dB of output power back-off (OPBO).