Load Modulation Research Articles

Hybrid Asymmetrical Load Modulated Balanced Amplifier With Wide Bandwidth and Three-Way-Doherty Efficiency Enhancement

This letter presents a new active-load-modulation power amplifier (PA) architecture, i.e., hybrid asymmetrical load modulated balanced amplifier (H-ALMBA). It is discovered that the control amplifier (CA) of load modulated balanced amplifier (LMBA) can be set as the carrier amplifier and the balanced amplifier (BA) as the peaking amplifier with different threshold settings for two subamplifiers, BA1 and BA2. Through proper amplitude and phase control and cooperative alignment of the turning-on sequence of BA1 and BA2, the entire H-ALMBA can achieve enhanced efficiency overextended power back-off range, similar to a three-way Doherty PA. More importantly, this hybrid load modulation behavior can be replicated over a nearly unlimited frequency span. The theory is well validated by a prototype developed using GaN technology and commercial quadrature couplers, which experimentally demonstrates a 4:1 RF bandwidth from 0.55 to 2.2 GHz and high efficiency, i.e., 55%–82% at peak power, 51%–69% at 5-dB power back-off and 40%–61% at 10-dB power back-off.

A 28-GHz SOI-CMOS Doherty Power Amplifier With a Compact Transformer-Based Output Combiner

This article presents a series voltage-combining Doherty power amplifier (PA) achieving high output power ( P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> ) and high power-back-off (PBO) efficiency for 28-GHz fifth-generation (5G) applications. We introduce a new transformer-based series output combiner design method to achieve a true-Doherty load modulation that uses a compact footprint. The output stages of the main PA and the auxiliary PA (aux. PA) both use a differential three-stacked FET topology for high output power without posing a reliability issue. The intermediate-node matching is achieved by using a shunt inductor for voltage waveform alignment and efficiency improvement. A modified differential quadrature hybrid is proposed to achieve the desired quadrature power splitting function without the need for an input balun. For the proof of concept, the proposed PA is implemented in a 22-nm CMOS fully depleted silicon-on-insulator (FD-SOI) technology with a core area of 0.2 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . At 28 GHz, the measured saturated output power ( P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sat</sub> ), 1-dB output compression point (OP <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1dB</sub> ), and peak power-added efficiency (PAE) are 22.5 dBm, 21.1 dBm, and 28.5%, respectively. State-of-the-art International Technology Roadmap for Semiconductors (ITRS) figure-of-merit (FOM) and power density are achieved. The measured PAE at 6-dB PBO is 22.1%, which results in an efficiency enhancement ratio of 1.56/3.12 with respect to an ideal class-B and class-A PA. The proposed PA can support 2.4-Gb/s 64-quadratic amplitude modulation (64-QAM) and 0.8-Gb/s 256-QAM signal with a competitive average PAE. Excellent device reliability is validated by operating the implemented PA under 3-dB gain compression point for 12 h with less than 0.06-dB P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">out</sub> variation. The proposed Doherty PA with a compact footprint is suitable for the integration purpose of future 5G multiple-input multiple-output (MIMO) and phased-array applications.

Cross diagnostics measurements of heat load profiles on the lower tungsten divertor of WEST in L-mode experiments

WEST is a full metallic tokamak with an extensive set of diagnostics for heat load measurements. In this paper, heat loads on the lower divertor of WEST are investigated using two independent methods. A first method relies on the thermal inversion of temperature measurements from arrays of thermal sensors embedded a few millimeters below the surface, while the second consists in the inversion of black body surface temperatures measured by infra-red (IR) thermography. The challenge of IR based temperature measurements in the full metal environment of WEST is addressed through a simplified model, allowing to correct for global reflections and low surface emissivities of tungsten surfaces. A large database (>100 L-mode discharges) is investigated. It is found that the energy absorbed by an outer divertor tile during a plasma discharge is closely estimated by the two diagnostics, over a large set of experimental conditions. A similar match is also found for the peak heat flux value on the outer target. The toroidal modulation of target heat loads by magnetic ripple is found to be consistent with the geometrical projection of a parallel heat flux component. Additionally, the heat flux channel width at the target is found to scale linearly with the magnetic flux expansion as expected. These observations give confidence in the robustness of the data from both diagnostics, and confirm the simple geometrical rules at use in the description of heat flux deposition on divertor targets. However, it is shown that the heat flux channel width estimated from infra-red thermography is about three times lower than the width estimated from embedded measurements, which is still under investigation.

A 24–28-GHz Doherty Power Amplifier With 4-W Output Power and 32% PAE at 6-dB OPBO in 150-nm GaN Technology

A 24-28-GHz two-stage GaN Doherty power amplifier (PA) is designed and characterized. At millimeter-wave (mm-wave) frequencies, the low output impedance of the auxiliary transistor loads the Doherty combining network, which lowers the power added efficiency (PAE) in back-off. In this design, a small periphery auxiliary transistor is used to increase the output impedance of the auxiliary transistor. The periphery ratio of the auxiliary and the main transistors is 77%. Even though, compared to symmetric Doherty PAs, the load modulation of the main transistor is reduced, this amplifier still achieves 32% and 23% PAE at 6 and 9-dB output power back-off, respectively. Attributing to the small auxiliary transistor, the amplifier obtains a small signal gain of 19 dB. The maximum output power of the amplifier is 4 W with a peak PAE of 42%.

Fully integrated three-way LDMOS Doherty PAs for 1.8–2.2 GHz dual-band and 2.6 GHz m-MIMO 5G applications

AbstractThis paper presents a fully integrated three-way Doherty architecture to address the challenges of 5G applications using laterally-diffused metal-oxide semiconductor (LDMOS) technology. By using the so-called CDS cancelation method for the Doherty combiner design, a wideband impedance transformation is achieved, that combined with the three-way Doherty power amplifier (DPA) architecture allows for high efficiency in deep back-off, with a reduced load modulation for high bandwidth. Throughout this paper, the design approach and realization are described, while multiple critical design challenges will be addressed such as low frequency drain resonance optimization, impact of in-package coupling effects, and linearity versus efficiency tradeoff. Two state-of-the-art three-way fully integrated LDMOS DPA monolithic microwave integrated circuit (MMICs) are presented to demonstrate how these measures have been successfully applied to different power amplifier (PA) line-up components for 5G base station systems. First, a 60 W 1.8–2.2 GHz multi-stage device for driver application in true dual-band operation is presented. The circuit design pays special attention to extended PA video bandwidth thanks to integrated passive device. After digital pre-distortion (DPD) in dual-band operation, this highly linear device achieves an outstanding adjacent channel leakage ratio (ACLR) of −56 dBc for a 2cLTE 20 MHz 8 dB peak-to-average ratio signal spaced by 345 MHz, thus 385 MHz instantaneous bandwidth (IBW), with 29% efficiency at 35 dBm, 12 dB output back-off (OBO). Second, the simulation and measurement results of a 55 W 2.6 GHz multi-stage DPA for massive-MIMO final stage application are presented, which yields an excellent linearized efficiency of 49% using a 200 MHz 10cLTE signal with an ACLR lower than −47.5 dBc. For 8cLTE 20 MHz (160 MHz IBW), the device yields 50% efficiency with −50.7 dBc ACLR linearized after DPD. The achieved efficiency is well comparable to published GaN DPAs. These results were achieved by improved simulation techniques to minimize frequency dispersion and thus allow high efficiency operation over wide bandwidth. Both devices show that LDMOS is not only a mature technology which allows those PAs to be reliable and low-cost for mass production in very compact packages, but also provide best-in-class RF performance according to the needs of 5G base station systems.

Neural and behavioral effects of perceptual load on auditory selective attention

Healthy adults performed an auditory version of the flanker task under low versus high perceptual load while behavioral and electrophysiological measures were recorded. Participants experienced less attentional interference under low load than high load, whether analyses were performed between tasks (Garner interference; found in accuracy and RT), between stimuli (flanker congruity; found in accuracy), or between sequences (Gratton effect; found in accuracy). Analysis of event-related potentials to the distractor (flanker), which was physically identical across load conditions, revealed load modulation of tasks effects in the P1 component (peak amplitude and latency), an early perceptual component peaking approximately 75 ms after distractor onset. As in behavioral performance, ERP analyses showed that auditory attentional disruption in P1 was significantly smaller under low perceptual load. Dipole source analysis suggested activation of prefrontal inhibitory control during low load and default mode network during high load. The results are in keeping with the predictions of tectonic theory (Melara & Algom, 2003), but inconsistent with expectations derived from perceptual load theory (Lavie, 1995).

Enhancing Bandwidth and Back-Off Range of Doherty Power Amplifier With Modified Load Modulation Network

This article presents a novel methodology for designing a broadband Doherty power amplifier (DPA) with extended output power back-off (OBO) range. A modified load modulation network (LMN) is proposed to enhance the OBO range and the bandwidth of the DPA simultaneously. Analysis is conducted to explore the relationship between the proposed LMN parameters and the broadband performance under various OBO levels. Generalized design formulas of the LMN parameters are then introduced to offer the broadband solution for arbitrary current ratios and OBO levels. An asymmetric DPA is demonstrated and implemented with gallium nitride (GaN) transistors using the proposed approach. The fabricated DPA operates from 1.4 to 2.5 GHz with 9-dB OBO range. The measured drain efficiency reaches 61%-75.5% at saturation and 44.6%-54.6% at 9-dB OBO within the operating bandwidth. When driven by a 60-MHz modulated signal with 9-dB peak-to-average power ratio (PAPR), the fabricated DPA attains 47.4%-53.5% average drain efficiency and better than -45.5-dBc adjacent channel leakage ratio (ACLR) after digital predistortion.

The Surviving Sepsis Campaign: Research Priorities for Coronavirus Disease 2019 in Critical Illness.

To identify research priorities in the management, pathophysiology, and host response of coronavirus disease 2019 in critically ill patients. The Surviving Sepsis Research Committee, a multiprofessional group of 17 international experts representing the European Society of Intensive Care Medicine and Society of Critical Care Medicine, was virtually convened during the coronavirus disease 2019 pandemic. The committee iteratively developed the recommendations and subsequent document. Each committee member submitted a list of what they believed were the most important priorities for coronavirus disease 2019 research. The entire committee voted on 58 submitted questions to determine top priorities for coronavirus disease 2019 research. The Surviving Sepsis Research Committee provides 13 priorities for coronavirus disease 2019. Of these, the top six priorities were identified and include the following questions: 1) Should the approach to ventilator management differ from the standard approach in patients with acute hypoxic respiratory failure?, 2) Can the host response be modulated for therapeutic benefit?, 3) What specific cells are directly targeted by severe acute respiratory syndrome coronavirus 2, and how do these cells respond?, 4) Can early data be used to predict outcomes of coronavirus disease 2019 and, by extension, to guide therapies?, 5) What is the role of prone positioning and noninvasive ventilation in nonventilated patients with coronavirus disease?, and 6) Which interventions are best to use for viral load modulation and when should they be given? Although knowledge of both biology and treatment has increased exponentially in the first year of the coronavirus disease 2019 pandemic, significant knowledge gaps remain. The research priorities identified represent a roadmap for investigation in coronavirus disease 2019.

New Transistor Behavioral Model Formulation Suitable for Doherty PA Design

This work presents a new artificial neural network (ANN) model formulation for RF high-power transistors which includes the S-parameters of the active device. This improves the small-signal extrapolation capability, and the OFF-state impedance approximation, making it suitable for Doherty power amplifier (DPA) design. This extrapolation capability plays a key role in the correct Doherty load modulation prediction, since, at low power levels, the peaking PA is subjected to active loads that cannot be synthetized with a passive load-pull system, forcing the model to extrapolate. Thus, the proposed model formulation is able to solve the issues that are normally observed when ANN-based models are used in complex PA architectures as the Doherty PA. To validate the proposed behavioral model, a 700-W asymmetrical LDMOS DPA, centered at 1.84 GHz, was simulated and measured.

Effect of rock mechanical properties on electromagnetic radiation mechanism of rock fracturing

The influence of rock mechanical properties on the electromagnetic radiation (EMR) mechanism of rock fracturing is an important research topic in solid mechanics and earthquake prediction. In this study, an EMR model of rock fracturing considering the fracture factor, elastic modulus, Poisson’s ratio, radiation distance and crack length is derived based on the Hertz oscillator array assumption. An experimental system, including an electromagnetic shielding module, an EMR signal induction and transmission module, a signal recording module and a loading module, is developed to understand the EMR characteristics of four different rocks. The validity of the EMR theoretical model is verified and the relationships between the rock cracking morphology and the EMR waveform, amplitude and frequency are revealed. It is found that rock mechanical properties have obvious influences on the EMR waveform, amplitude and frequency during rock fracturing. This study provides a better understanding on the EMR mechanism of rock fracturing and can help to improve the accuracy of rock disaster prediction based on EMR.

Design and Analysis of Continuous-Mode Doherty Power Amplifier With Second Harmonic Control

While continuous-mode Doherty power amplifier (CM-DPA) can achieve high efficiency at output back-off (OBO) power levels, their achievable bandwidth and load modulation have not yet been fully investigated. This brief reveals that the bandwidth of CM-DPA is limited by the impedance trajectories of the peaking transistors. In particular, the peaking transistor degrades the bandwidth in the high power region and limits the fractional bandwidth (FBW) of the CM-DPA. Moreover, based on post-matching Doherty architecture, an analytical method for harmonic control in CM-DPAs is presented. A broadband CM-DPA with harmonic control is implemented, fabricated and measured. The CM-DPA delivers a saturation output power (Psat) of 42.6–44.4 dBm from 1.50 to 2.55 GHz, i.e., FBW of 51.8%. The drain efficiencies in the interested frequency band are 50.7%–69.7% and 43.3%–57% at the Psat and 6-dB OBO power levels, respectively.

Parametric and sensitivity analysis of a PCM-integrated wall for optimal thermal load modulation in lightweight buildings

Load modulation in buildings is becoming increasingly important due to growing disparity in energy demand during peak and off-peak hours. Integrating phase change material (PCM) in building envelopes and using a controlled precooling strategy can provide substantial thermal load modulation; however, it may greatly increase the total energy use. Previous studies have employed PCM in building envelopes primarily for energy savings and, to some extent, peak load shedding and shifting. However, the load modulation capacity of a PCM-integrated envelope has not been well explored in the literature. In this study, we perform an extensive parametric and sensitivity analysis on PCM-integrated lightweight building walls and examine the combinatory effects of various PCM parameters on thermal load modulation and wall-related heat gains in buildings. Using numerical simulations, we investigate eight PCM parameters: PCM location in the wall, transition temperature, thickness, latent heat, transition range, density, specific heat, and thermal conductivity. We evaluate their impact and relative importance to achieve maximum load modulation in buildings without compromising occupants’ thermal comfort or total energy use. The results show that the optimized PCM proposed in this study can completely invert the transient heat gain profile of the wall, providing up to 70% reduction of wall-related heat gain during peak hours without a major increase in the cumulative heat gain.

Beam-Steerable Transponder Based on Antenna Array and Phased Modulators

This letter presents a novel concept of beam-steerable transponder based on antenna array and phased modulators. The steerability of the beam is achieved by optimally delaying the modulated reflected signal at each antenna element (i.e., changing the phase in frequency domain) with load modulation technique. In this manner, the reflected backscattered signal power can be maximized at one particular direction. The approach makes transponder to collect ambient waves from any direction and further modulate and redirect it to any other direction. The results obtained through experimentation proves the feasibility of omnidirectional transponder and pave way for future lower power smart devices. The transponder functions in the Wi-Fi frequency band of 2.4 GHz.

The clinical and microbiological utility of inhaled aztreonam lysine for the treatment of acute pulmonary exacerbations of cystic fibrosis: An open-label randomised crossover study (AZTEC-CF)

BackgroundThe objective of this study was to explore the clinical and microbiological outcomes associated with substituting inhaled aztreonam lysine for an intravenous antibiotic in the treatment of acute pulmonary exacerbations of CF. MethodsAn open-label randomised crossover pilot trial was conducted at a UK CF centre among 16 adults with CF and P. aeruginosa infection. Median [IQR] age was 29.5 [24.5-32.5], mean ± SD forced expiratory volume in 1 second (FEV1) was 52.4 ± 14.7 % predicted. Over the course of two exacerbations, participants were randomised to sequentially receive 14 days of inhaled aztreonam lysine plus IV colistimethate (AZLI+IV), or dual IV antibiotics (IV+IV). Primary outcome was absolute change in % predicted FEV1. Other outcomes evaluated changes in quality of life, bacterial load and the lung microbiota. ResultsThe difference between mean change in lung function at day 14 between AZLI+IV and IV+IV was +4.6% (95% CI 2.1-7.2, p=0.002). The minimum clinically important difference of the Cystic Fibrosis Revised Questionnaire (CFQ-R) was achieved more frequently with AZLI+IV (10/12, 83.3%) than IV+IV (7/16, 43.8%), p=0.05. No differences were observed for modulation of serum white cell count, C-reactive protein or sputum bacterial load. Microbiome compositional changes were observed with IV+IV (Bray-Curtis r2=0.14, p=0.02), but not AZLI+IV (r2=0.03, p=0.64). ConclusionIn adults with CF and P. aeruginosa infection experiencing an acute pulmonary exacerbation, AZLI+IV improved lung function and quality of life compared to the current standard treatment. These findings support the need for larger definitive trials of inhaled antibiotics in the acute setting. Clinical trial registrationEudraCT 2016-002832-34ClinicalTrials.org NCT02894684

Alternative variable refrigerant flow (VRF) air conditioning systems with rational distribution of thermal load

One of the most attractive reserves of enhancing the energetic efficiency of air conditioning systems (ACS) is to provide operation of compressors in closed to nominal modes by choosing the rational design refrigeration capacities and their distribution according to current thermal loading to provide closed to maximum annual refrigeration energy generation. Generally, the overall thermal load band of any ACS comprises the unstable load range, corresponding to ambient air precooling with significant load fluctuations, and a comparatively stable load part for further air conditioning from a threshold temperature to a target value. The stable thermal load range can be covered by operation of conventional compressor in closed to nominal mode, meantime ambient air precooling needs load modulation by applying a variable speed compressor. A proposed ACS enables a wide range of refrigerant flow variation without heat flux drop in air coolers and can be considered as advanced alternative to variable refrigerant flow systems.

Millimeter-Wave Power Amplifier Integrated Circuits 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.

Real time reorientation and cognitive load adjustment allow for broad application of virtual reality in a pediatric hospital

With a new generation of affordable portable virtual reality (VR), clinicians are discovering more utility for VR, while also identifying opportunities for improvement, such as the inability to reorient the horizon line during repositioning or transport, or modulate cognitive load in real time. At our institution, this lack of functionality prohibited or decreased VR usage in some clinical scenarios such as dressing changes with dynamic positioning. The purpose of this brief report is to describe the development and use of a VR application that is optimized for the healthcare setting and report historical effects of patients who utilized VR as supplement to Child Life procedures. Eligible affects per chart review included Happy, Relaxed, Anxious, Distressed, Unable to Assess. Given the need for real-time reorientation and cognitive load modulation, we created the Space Pups™ VR application. The experience was launched as part of the Stanford Chariot Program in the summer of 2017, and its usage was tracked through the electronic medical record and a VR application dashboard. Chart review was queried from 3 January 2018 to 9 August 2021 for pediatric patients who used VR with real-time reorientation and cognitive load modulation as a supplement to their Child Life interventions. The Space Pups™ experience has been successfully used in a variety of settings, including perioperative care, vascular access, wound care, and ENT clinic, a total of 1696 times. Patients ranged from 6 years to 18-year old, with no reports of side effects. Significant results (P<0.001) were observed pre- and post-VR use for affect improvements in Happy, Relaxed, and Anxious, but not for Distressed. The ability to reorient VR experiences in real time has increased functionality where other applications have failed. While more studies are needed to quantify the anxiolytic and pain-reducing effect of Space Pups™, our report demonstrates the feasibility of this VR experience as a non-pharmacological modality to safely increase patient cooperation in a wide variety of clinical settings.

Measurement and evaluation of the earth's magnetic field parameters using the ECUADOR-UTE small cameras (HC1PX)

The paper deals with the use of the small spacecraft Ecuador-UTE (HC1PX) designed to conduct space experiments in autonomous flight conditions and, in particular, to measure the Earth's electromagnetic field and study the ionosphere. The spacecraft has a built-in target load module, including a precision magnetometer that measures the Earth's magnetic field. The measurement results are used to study the properties and state of the circumterranean environment including magnetic anomalies. The latter may indicate certain tectonic structures in the sedimentary stratum, which are indicators of oil and gas, and magnetic pole displacement processes. Measurement results can also be used for prediction and forecasting efforts in anomalous zones. The compiled analytical dependences for the anomalous zones can serve as a forecasting device when studying the magnetic tension of the Earth's geographic regions by means of a spacecraft. Measuring the magnetic anomalies of the Earth's surface is should prove necessary for factoring them in and developing national industries.

A Broadband Doherty Power Amplifier With a New Load Modulation Network

In this paper, we proposed a new load modulation method to improve bandwidth and efficiency at output power back-off (OBO) of the Doherty Power Amplifier (DPA). The quarter wavelength transmission line behind the combination point of the impedance inverter was replaced with a dual-frequency matching circuit to matche the impedance value of the combination point to the load impedance in this method. The dual-frequency matching was used to compensate for the frequency dispersion effect that occurs in the traditional impedance inverter network and to a certain extent solves the bandwidth limitation of the Doherty power amplifier. To verify the proposed theory, a broadband high-efficiency power amplifier was designed and manufactured for 5G mobile communications. Measurement results show that the designed DPA is in the range of 2.4-3.7GHz, the saturated output power is above 42dBm, the saturated drain efficiency is 61.2%-68.4%, and the 6dB back-off efficiency is 49.7%-61.4%.

A MM-Wave Current-Mode Inverse Outphasing Transmitter Front-End: A Circuit Duality of Conventional Voltage-Mode Outphasing

This article presents a millimeter-wave (mm-wave) transmitter (TX) front-end employing a new inverse outphasing architecture with current-mode power amplifiers (PAs). This study on the conventional outphasing operation reveals its strong dependence on its voltage-mode driving source assumption and thus exhibits major limitations at mm-wave, since efficient and linear mm-wave PAs often behave as current sources. To address this challenge, we propose a current-mode inverse outphasing architecture that employs current-mode driving sources and is inherently compatible with mm-wave linear PAs. Moreover, the conventional series outphasing combiner is replaced by a much simpler and low-loss parallel power combining scheme. Closed-form mathematical expressions are derived for both the outphasing and inverse outphasing operations, including the active load modulation, Chireix compensations, and outphasing efficiency, which fundamentally explains the limitations of the conventional approach and the advantages of the inverse outphasing architecture. Further theoretical analysis discovers a circuit duality relationship between outphasing and inverse outphasing architectures, which offers unique circuit intuitions. As a proof-of-concept, we implement a 28-GHz TX front-end using cascode PAs, based on the inverse outphasing architecture. In the measurement, the TX achieves 22.7-dBm saturated output power with 42.6% PA drain efficiency. The TX exhibits effective PA efficiency enhancement at 6-dB power back-off (PBO), validating the high-efficiency inverse outphasing active load modulation. Modulation tests with high-order quadrature amplitude modulation (QAM) signals demonstrate that the TX supports >10-Gb/s high-fidelity complex signals and achieves the state-of-the-art modulation performance.