Showing papers on "RF power amplifier published in 2021"

Switchmode RF and Microwave Power Amplifiers

Abstract: Combining solid theoretical discussions with practical design examples, this book is an essential reference on developing RF and microwave switchmode power amplifiers. With this book you will be able to: * Design high-efficiency RF and microwave power amplifiers on different types of bipolar and field-effect transistors using well-known and novel theoretical approaches, nonlinear simulation tools, and practical design techniques * Design any type of high-efficiency switchmode power amplifiers operating in Class D or E at lower frequencies and in Class E or F and their subclasses at microwave frequencies, with specified output power * Understand the theory and practical implementation of load-network design techniques based on lumped and transmission-line elements * Combine multi-stage Doherty architecture and switchmode power amplifiers to significantly increase efficiency of the entire radio transmitter * Learn the different types of predistortion linearization techniques required to improve the quality of signal transmission in a nonlinear amplifying system New to this edition: . Comprehensive overview of different Doherty architectures which are, and will be used in modern communication systems to save power consumption and reduce costs . A new chapter on analog and digital predistortion techniques . Coverage of broadband Class-F power amplifiers, high-power inverse Class-F power amplifiers for WCDMA systems, broadband Class-E techniques *Unique focus on switchmode RF and microwave power amplifiers that are widely used in cellular/wireless, satellite and radar communication systems and which offer major power consumption savings *Complete coverage of the new Doherty architecture which offers major efficiencies and savings on power consumption *Balances theory with practical implementatation, avoiding a cookbook approach, enabling engineers to develop better designs *Trusted content from leading figures in the field with a Foreword of endorsement by Zoya Popovic

Biotelemetry and Wireless Powering of Biomedical Implants Using a Rectifier Integrated Self-Diplexing Implantable Antenna

Abstract: This article proposes an efficient and complete wireless power transfer (WPT) system (WPTS) for multipurpose biomedical implants The WPTS is composed of a self-diplexing implantable antenna, efficient rectifier, and WPT transmitter (WPT Tx) The proposed system is capable of simultaneously transmitting recorded data and recharging the batteries of the devices (so as to elongate the implant life) The WPT Tx occupies dimensions of $50 \times 50 \times 16$ mm3 and is optimized to effectively transfer power at 1470 MHz to a 55-mm deep implantable device An efficient and compact ( $34 \times 67$ mm2) rectifier is used at 1470 MHz to convert the harvested RF power into a useful direct current (dc) power The proposed rectifier circuit exhibits a high conversion efficiency of 50% even at an input power of −14 dBm and maximum efficiency of 761% at 2 dBm The proposed self-diplexing implantable antenna occupies small dimensions (94 mm3) and operates at 915 and 1470 MHz by exciting ports 1 and 2, respectively The biotelemetry operation is performed using a 915 MHz band (port 1), and the rectifier circuit is connected to port 2 (1470 MHz) to perform wireless powering The simulated results are validated by examining the individual elements (WPT Tx, rectifier, and self-diplexing antenna) and overall WPTS in a saline solution and minced pork The results prove that the proposed scheme is suitable for biotelemetry and wireless powering of biomedical implants

Joint Waveform and Beamforming Optimization for MIMO Wireless Power Transfer

Abstract: In this paper, we study a multi-sine multiple-input multiple-output (MIMO) wireless power transfer (WPT) system with the objective to increase the output DC power. We jointly optimize the multi-sine waveform and beamforming accounting for the rectenna nonlinearity, and consider two combining schemes for the rectennas at the receiver, namely DC and RF combinings. For DC combining, the waveform and transmit beamforming are optimized, as a function of the channel state information (CSI). For RF combining, the optimal transmit and receive beamformings are provided in closed form and the waveform is optimized. We also consider a practical RF combining circuit using phase shifter and RF power combiner and optimize the waveform, transmit beamforming, and analog receive beamforming adaptive to the CSI. Two types of performance evaluations, based on the nonlinear rectenna model and accurate and realistic circuit simulations, are provided. The evaluations demonstrate that the joint waveform and beamforming design can increase the output DC power by leveraging the beamforming gain, the frequency diversity gain, and the rectenna nonlinearity. It also shows that the joint waveform and beamforming design provides a higher output DC power than the beamforming-only design with a relative gain of 180% in a two-transmit antenna sixteen-sinewave two-receive antenna setup.

Beamforming Optimization for MIMO Wireless Power Transfer With Nonlinear Energy Harvesting: RF Combining Versus DC Combining

Abstract: In this article, we study the multiple-input and multiple-output (MIMO) wireless power transfer (WPT) system so as to enhance the output DC power of the rectennas. To that end, we revisit the rectenna nonlinearity considering multiple receive antennas. Two combining schemes for multiple rectennas at the receiver, DC and RF combinings, are modeled and analyzed. For DC combining, we optimize the transmit beamforming, adaptive to the channel state information (CSI), so as to maximize the total output DC power. For RF combining, we compute a closed-form solution of the optimal transmit and receive beamforming. In addition, we propose a practical RF combining circuit using RF phase shifter and RF power combiner and also optimize the analog receive beamforming adaptive to CSI. We also analytically derive the scaling laws of the output DC power as a function of the number of transmit and receive antennas. Those scaling laws confirm the benefits of using multiple antennas at the transmitter or receiver. They also highlight that RF combining significantly outperforms DC combining since it leverages the rectenna nonlinearity more efficiently. Two types of performance evaluations, based on the nonlinear rectenna model and based on realistic and accurate rectenna circuit simulations, are provided. The evaluations demonstrate that the output DC power can be linearly increased by using multiple rectennas at the receiver and that the relative gain of RF combining versus DC combining in terms of the output DC power level is very significant, of the order of 240% in a one-transmit antenna ten-receive antenna setup.

First RF Power Operation of AlN/GaN/AlN HEMTs With >3 A/mm and 3 W/mm at 10 GHz

Abstract: The AlN/GaN/AlN heterostructure is attractive for microwave and millimeter-wave power devices due to its thin top barrier, tight carrier confinement, and improved breakdown voltage. This work explores the large-signal RF performance of high-electron-mobility transistors on this heterostructure. Results are highlighted by record high on-current of 3.6 A/mm, and record maximum oscillation frequency ( $f_{max}$ ) of 233 GHz. The load-pull power sweep at 10 GHz demonstrate a peak power added efficiency (PAE) of 22.7% with an associated gain ( $G_{T}$ ) of 8.7 dB and output power ( $P_{out}$ ) of 3 W/mm. When optimized for power, the peak $P_{out}$ of 3.3 W/mm has an associated PAE of 14.7% and $G_{T}$ of 3.2 dB. This first demonstration is encouraging for the mm-wave power potential of the AlN/GaN/AlN HEMT.

Electromagnetic-Based Correction of Bio-Integrated RFID Sensors for Reliable Skin Temperature Monitoring

Abstract: Bio-integrated wireless sensors in the form of conformable plaster, based on the Radiofrequency Identification (RFID) communication, have been recently proposed for the battery-less measurement of the human skin temperature. However, the response of the Integrated Circuit (IC) transponder is sensitive to the strength of the interrogating power. Indeed, high power produces artifacts on the sampled temperature up to 2 °C when the mutual position between reader and sensors, as well as the emitted power, can not be carefully controlled. Hence, a reliable adoption of this technology in real cases is challenging and still in question. A combined macro-scale electromagnetic-thermal model is here introduced to predict and correct the above artifact so that the temperature measurement becomes insensitive to the RF power collected by the IC. The method is based on the new generation RFID ICs with on-chip temperature sensor that are also capable to give back the strength of the collected RF power. The model is validated in controlled conditions and then applied for different skin temperature measurements on human body. An average accuracy of ±0.25 °C, compared with a reference calibrated thermocouple, was demonstrated in the considered tests.

Dynamic Focusing of Large Arrays for Wireless Power Transfer and Beyond

Abstract: We present architectures, circuits, and algorithms for dynamic 3-D lensing and focusing of electromagnetic power in radiative near- and far-field regions by arrays that can be arbitrary and nonuniform. They can benefit applications such as wireless power transfer at a distance (WPT-AD), volumetric sensing and imaging, high-throughput communications, and optical phased arrays. Theoretical limits on system performance are calculated. An adaptive algorithm focuses the power at the receiver(s) without prior knowledge of its location(s). It uses orthogonal bases to change the phases of multiple elements simultaneously to enhance the dynamic range. One class of such 2-D orthogonal and pseudo-orthogonal masks is constructed using the Hadamard and pseudo-Hadamard matrices. Generation and recovery units (GU and RU) work collaboratively to focus energy quickly and reliably with no need for factory calibration. Orthogonality enables batch processing in high-latency and low-rate communication settings. Secondary vector-based calculations allow instantaneous refocusing at different locations using element-wise calculations. An emulator enables further evaluation of the system. We demonstrate modular WPT-AD GUs of up to 400 elements utilizing arrays of 65-nm CMOS ICs to focus power on RUs that convert the RF power to dc. Each RFIC synthesizes 16 independently phase-controlled RF outputs around 10 GHz from a common single low-frequency reference. Detailed measurements demonstrate the feasibility and effectiveness of RF lensing techniques presented in this article. More than 2 W of dc power can be recovered through a wireless transfer at distances greater than 1 m. The system can dynamically project power at various angles and at distances greater than 10 m. These developments are another step toward unified wireless power, sensing, and communication solutions in the future.

Frequency-Reconfigurable Input-Reflectionless Bandpass Filter and Filtering Power Divider With Constant Absolute Bandwidth

Abstract: An RF input-quasi-reflectionless bandpass filter (BPF) with reconfigurable center frequency and constant absolute bandwidth (ABW) is presented. The proposed BPF is based on a tunable complementary-diplexer architecture, which is made up of a main bandpass-type channel and an auxiliary channel with nearly-complementary bandstop-type filtering response that are synchronously reconfigured in frequency. The auxiliary channel is terminated by a resistor to absorb the RF power reflected by the main channel within its out-of-band region. In this manner, input-quasi-reflectionless capability is obtained. As an original technique, the constant ABW is attained in this overall BPF across the tuning range by means of the compensation of the bandwidth variations between its two channels. Subsequently, as a further application of this filter design concept, an RF frequency-adaptive Wilkinson-type power divider (PD) with constant-ABW filtering response and input-quasi-reflectionless behavior is reported. A single resistively-terminated bandstop-type branch is connected at the input port of the filtering PD to absorb the non-transmitted RF-input-signal energy. For validation purposes, a varactor-tuned frequency-reconfigurable input-quasi-absorptive BPF and a 3-dB filtering PD with constant-ABW are built and measured.

Dynamic Ambient RF Energy Density Measurements of Montreal for Battery-Free IoT Sensor Network Planning

Abstract: This work summarizes an outdoor dynamic measurement of ambient radiofrequency (RF) power density in the core areas of Montreal city, which can eventually be exploited for possible battery-free Internet of Things (IoT) sensor network planning. The measurement covers a frequency range of 400–2700 MHz. The power density along major streets, roads, and highways is captured and analyzed, which differs from previous stationary measurements. Results indicate that cellular communication bands (GSM/LTE850 and LTE700) are the best choice for RF energy recycling in downtown (populated) areas. The largest average power levels of GSM/LTE850 and LTE700 bands are −35.50 and −36.95 dBm, respectively. In contrast, in suburban areas where cellular communication signals are generally weak, the digital television band with a peak level of −47.68 dBm presents the largest among all frequency bands. Moreover, one separate measurement at a fixed location is conducted on a typical workday to study the effects of foot traffic on ambient RF power density. Results illustrate that no obvious fluctuations are detected during this daytime measurement. For example, both average power levels of GSM/LTE850 and LTE700 remain at a relatively stable level of −25 dBm throughout the measurement. With the advance of far-field wireless power transfer and backscattering techniques, ambient RF power-enabled battery-free IoT sensors are feasible and will contribute to the planning and implementation of a smarter and greener city.

Dual-Band Compact Rectenna for UHF and ISM Wireless Power Transfer Systems

Abstract: A dual-band UHF/industrial, scientific and medical (ISM) compact rectenna with wideband UHF matching (855–935 MHz) covering all, EU, U.S., and Chinese UHF radio frequency identification (RFID), standards is presented. The proposed design consists of a compact single-port, dual-band antenna, a three-port dual-branch matching network, and two voltage doubler rectifiers implemented with Schottky diodes and terminated with a common 10 $\text{k}\Omega $ load. For each band, the measured RF-to-dc efficiency is around 60% for a −5 dBm unmodulated signal. The wideband behavior of the rectenna supports harvesting of multitone signals. The use of a six-tone signal increases the maximum RF-to-dc efficiency of the dual-band rectifier, from approximately 60% for a single-tone UHF signal (890 MHz) to 80% for a six-tone signal for a received RF power of −5 dBm in both cases. A signal generator is used to generate a six-tone signal of equally weighted and equally spaced (10 MHz separation) monochromatic tones, with a total bandwidth of 50 MHz. The measurement results demonstrate that the dc voltages rectified from the two separate RF signals are effectively superimposed on the load, providing a clear advantage compared to single-band rectennas. The single-layer, compact design with a size of $80\times45$ mm2, with a high RF-to-dc efficiency, is an excellent candidate for wirelessly powered RFID tags.

RF power transfer efficiency and plasma parameters of low pressure high power ICPs

Abstract: Inductively coupled radio frequency (RF) ion sources operating at 1 MHz under the condition of a low gas pressure of 0.3 Pa are the basis of negative hydrogen/deuterium ionbased neutral beam injection systems of future fusion devices. The applied high RF powers of up to 75 kW impose considerable strain on the RF system and so the RF power transfer efficiency η becomes a crucial measure of the ion source’s reliability. η depends on external parameters such as geometry, RF frequency, power, gas pressure and hydrogen isotope. Hence, η along with the plasma parameters are investigated experimentally at the ITER prototype RF ion source. At only 45%–65% in hydrogen and an increase of around 5% in deuterium, η is found to be surprisingly low in this ion source. The power that is not coupled to the plasma is lost by Joule heating of the RF coil (∼26%) and due to eddy currents in the internal Faraday screen (∼74%). The matching transformer adds up to 8 kW of losses to the system. The low values of η and the high share of the losses in the Faraday screen and the transformer strongly suggest optimization opportunities. At high power densities well above 5 W cm−3, indications for neutral depletion as well as for the ponderomotive effect are found in the pressure and power trends of η and the plasma parameters. The comprehensive data set may serve for comparison with other RF ion sources and more standard inductively coupled plasma setups as well as for validating models to optimize RF coupling.

Complexity-Reduced Model Adaptation for Digital Predistortion of RF Power Amplifiers With Pretraining-Based Feature Extraction

Abstract: In this article, we present a new method to reduce the model adaptation complexity for digital predistortion (DPD) of radio frequency (RF) power amplifiers (PAs) under varying operating conditions, using pretrained transformation of model coefficients. Experimental studies show that the PA behavior variations can be effectively tracked using a small number of “transformed” coefficients, even with large deviations in its output characteristics. Based on this discovery, to avoid reextracting all the original coefficients every time when the operating condition changes, we propose to conduct a one-time off-line pretraining stage to extract the common features of PA behaviors under different operating conditions first. The online model adaptation process will then only need to identify a small number of transformed coefficients, which can result in a drastic reduction in the computational complexity of the model adaptation process. The proposed solution is validated by experimental results considering varying signal bandwidth and output power levels on a high-efficiency gallium–nitride Doherty PA, where the computational complexity is significantly reduced and the system performance is not compromised.

Towards Energy Efficient Mobile Wireless Receivers Above 100 GHz

Abstract: Wireless communication above 100 GHz offers the potential for massive data rates and has attracted considerable attention for Beyond 5G and 6G systems. A key challenge in the receiver design in these bands is power consumption, particularly for mobile and portable devices. This paper provides a general methodology for understanding the trade-offs of power consumption and end-to-end performance of a large class of potential receivers for these frequencies. The framework is applied to the design of a fully digital 140 GHz receiver with a 2 GHz sample rate, targeted for likely 6G cellular applications. Design options are developed for key RF components including the low noise amplifier (LNA), mixer, local oscillator (LO) and analog-digital converter (ADC) in 90 nm SiGe BiCMOS. The proposed framework, combined with detailed circuit and system simulations, is then used to select among the design options for the overall optimal end-to-end performance and power tradeoff. The analysis reveals critical design choices and bottlenecks. It is shown that optimizing these critical components can enable a dramatic 70 to 80% power reduction relative to a standard baseline design enabling fully-digital 140 GHz receivers with RF power consumption less than 2 W.

Diamond-Incorporated Flip-Chip Integration for Thermal Management of GaN and Ultra-Wide Bandgap RF Power Amplifiers

Abstract: GaN radio frequency (RF) power amplifiers offer many benefits including high power density, reduced device footprint, high operating voltage, and excellent gain and power-added efficiency. Accordingly, these parts are enabling next-generation technologies such as fifth-generation (5G) base transceiver stations and defense/aerospace applications such as high-performance radar and communication systems. However, these benefits can be overshadowed by device overheating that compromises the performance and reliability. In response to this, researchers have focused on GaN-on-diamond integration during the past decade. However, manufacturability, scalability, and long-term reliability remain as critical challenges toward the commercialization of the novel device platform. In this work, a diamond-incorporated flip-chip integration scheme is proposed that takes advantage of existing semiconductor device processing and growth techniques. Using an experimentally validated GaN-on-SiC multifinger device model, the theoretical limit of the cooling effectiveness of the device-level thermal management solution has been evaluated. Simulation results show that by employing a $\sim 2-\mu \text{m}$ diamond passivation overlayer, gold thermal bumps, and a commercial polycrystalline carrier wafer, the power amplifier’s dissipated heat can be effectively routed toward the package, which leads to a junction-to-package thermal resistance lower than GaN-on-diamond high electron mobility transistors (HEMTs). Furthermore, simulation results show that this approach is even more promising for lowering the device thermal resistance of emerging ultra-wide bandgap devices based on $\beta $ -Ga2O3 and AlGaN, below that for today’s state-of-the-art GaN-on-diamond HEMTs.

Second Harmonic Exploitation for High-Efficiency Wireless Power Transfer Using Duplexing Rectenna

Abstract: In this article, a novel duplexing rectenna with harmonic feedback capability is proposed for efficient wireless power transfer (WPT) applications. The proposed duplexing rectenna can harvest the incoming radio frequency (RF) energy efficiently and also make use of an inherent harmonic signal, which is sent back to the RF transmitter (Tx) for positioning in order to guide the radiation patterns from Tx antenna array for optimum WPT. A novel duplexing dipole antenna is designed based on the top loading and capacitive gap effects. It is used to receive RF power at fundamental frequency 0.915 GHz and transmit the second harmonic signals at 1.83 GHz as a feedback. Experimental validation of a complete WPT system with beam-scanning capability has been carried out. It is shown that the fabricated rectifier has realized a maximum RF-dc conversion efficiency of 71% (at 15-dBm input power) and a measured peak second harmonic power of −1 dBm. Thus, the proposed duplexing rectenna can form a closed-loop system by providing its location information for efficient WPT applications.

A 500-nW-to-1-mW Input Power Inductive Boost Converter With MPPT for RF Energy Harvesting System

Abstract: This article discusses a novel RF energy-harvesting system for available power as low as 500 nW. The system includes a main RF rectenna (antenna followed by rectifier) for energy harvesting, an auxiliary RF rectenna for power detection, and a boost converter along with its control circuit. For maximum power point tracking (MPPT), a particular reference voltage ${V_{\text {ref}}}$ for a range of received RF power (from −11 to 3 dBm) is used to harvest maximum available power from the main rectenna by regulating its output voltage with the help of the boost converter. ${V_{\text {ref}}}$ for MPPT is provided by the auxiliary RF rectenna and the power-detector circuit and depends on the RF power. The complete system is designed, simulated, fabricated, and tested in the 180-nm mixed-mode CMOS technology. Measured results show that the boost converter can track the maximum power point for the input available power ranging from 500 nW to 1 mW. The efficiency of the boost converter is a function of the available input power and the equivalent source resistance of the RF energy harvester. For an equivalent source resistance of ${1~\text {k}\Omega }$ , the maximum efficiency of the boost converter is 91.6% at ${165~\mu \text {W}}$ of the available input power. As a potential application, a ${\Delta \Sigma }$ modulator designed in the 180-nm mixed-mode CMOS technology is powered by the proposed energy-harvesting system. The efficiency of the boost converter is approximately 76.6% while powering the ${\Delta \Sigma }$ modulator and 78.5% while powering the dc load at the RF power of ${-7\,\,\text {dBm}}$ .

A Flexible Dual-Band Rectenna With Full Azimuth Coverage

Abstract: This paper presents a novel cylindrical shaped dual-band flexible rectenna capable of harvesting RF energy from number of RF sources available in the entire azimuth plane. The proposed configuration is an array of four identical dual-band rectenna subsystems, printed on the lightweight flexible substrate. Here, each rectenna subsystem comprises of a dual-ring shaped dual-band monopole antenna and a dual-band rectifying circuit. The designed topology is good for popular bands of LTE 1.8 GHz and Wi-Fi 2.45 GHz. The robustness of the designed antenna in the proposed cylindrical shaped rectenna is also verified by testing it for different bending angles in the H-plane by simulation as well as measurement. The bending performance is tested for the antenna using S11 and farfield radiation pattern. Further, for extracting maximum RF signals in the entire azimuth plane, these four identical antennas are backed by a wide-band artificial magnetic conductor (AMC) placed in the inner region of the cylinder. The fabricated single rectenna unit is capable of converting power with 40% efficiency at very low input RF power −12 dBm. Finally, the overall rectenna array is fabricated and validated through measurements using two different test antennas as a RF sources in the real environment of lab. The proposed light weight, rectenna printed on a flexible substrate can extract RF signals from a number of randomly distributed RF sources simultaneously, while maintaining the overall compact configuration.

A Self-Gating RF Energy Harvester for Wireless Power Transfer With High-PAPR Incident Waveform

Abstract: In this article, we propose a self-gating radio frequency (RF) energy harvester (RFEH) for reaching a high-power harvesting efficiency (PHE) at a low incident RF power level with a high peak-to-average power ratio (high-PAPR) waveform. It includes a power switch between a cross-coupled rectifier and its supplied load to cut off the reverse leakage current in between the short power bursts. The power switch is dynamically controlled based on an indication of the ability of the RFEH to effectively charge the load at the instantaneous incident power level. This is achieved by comparing the load voltage with the open-circuit voltage of a replica rectifier. A comparator with optional proteresis (reversed hysteresis) is proposed for compensating its logic delay at the start and at the end of the short RF power bursts. As a result, the power switch is accurately turned on only during the power bursts. The self-gating RFEH was prototyped for 2.45-GHz wireless power transfer (WPT). It includes a cross-coupled rectifier with the proposed self-gating circuit fabricated in a 65-nm process, a discrete balun, a parasitic-aware-sized $\pi $ matching network, and an off-the-shelf power management unit (PMU) with maximum power point tracking (MPPT). Measurement results show sensitivity as low as −26.7 dBm with a peak PHE of 32.3% at −14.1-dBm incident power. Compared with the state-of-the-art works, the proposed design significantly improves the RFEH performance at the target low average incident power.

Boosted Model Tree-Based Behavioral Modeling for Digital Predistortion of RF Power Amplifiers

Abstract: In this article, we propose a new behavioral modeling approach, called boosted model tree, to characterize and compensate for the complex nonlinear distortions induced by wideband high-efficiency radio frequency power amplifiers. With the proposed model, the input data are classified into different zones by decision trees and each zone is assigned separate submodels. We also employ a model boosting technique to build multiple parallel tree structures that jointly model the desired nonlinear behavior. By designing dedicated optimization procedures, both tree structures and submodel coefficients can be efficiently identified. It is demonstrated that the combination of piecewise and parallel structures provides a powerful and hardware-efficient way to model nonlinear memory effect and cross terms. Based on the experimental results, the proposed method can achieve improved linearization performance with low hardware complexity under challenging wideband predistortion scenarios.

A CMOS Envelope Tracking Supply Converter for RF Power Amplifiers of 5G NR Mobile Terminals

Abstract: An envelope tracking supply converter was presented for the RF power amplifiers of sub-6 GHz 5G NR mobile devices. The hybrid supply converter consisted of a linear, fast switching, and slow switching regulators connected in parallel. The two-phase hysteretic control was proposed for use in the fast switching regulator to track the fast-varying envelope of 40-MHz 5G NR signal. The 0.25-μm CMOS supply converter achieved a maximum efficiency of 79.1%. The power-added efficiency improvement of the RF power amplifier with the proposed supply converter was 3.1% when tested with a 40-MHz 256-QAM 5G NR signal.

RF Reliability of SOI-based Power Amplifier FETs for mmWave 5G Applications

Abstract: RF reliability at 28GHz in PAFETs under constant and varying output load (Z0) was evaluated. Time domain analyses show that in addition to non-conducting TDDB (ncTDDB), both conducting (cHCI) and non-conducting Hot Carrier Injection (ncHCI) degradation play key roles as primary mechanisms. RF power as stress variable under linear, P1dB and compression shows higher degradation in compression attributed to higher peak voltage swings. Degradation under varying load is correlated to ruggedness power and VSWR ratio. Excellent DC and RF Model-Hardware correlation was achieved. 5G NR simulations show that PAFETs meet circuit PA lifetime targets making it an ideal technology for mmWave 5G applications.

Single-Chip CMOS Reconfigurable Dual-Band Tri-Mode High-Efficiency RF Amplifier Design

Abstract: This brief presents a new design methodology of single-chip reconfigurable CMOS RF power amplifier (PA) supporting both dual-band and multi-power-mode operation. The proposed architecture utilizes a novel switched-capacitor based output network to facilitate differential signal combining and impedance transformation at two widely separated frequency bands. It can offer three distinct output power levels (saturation) to be selected for multi-power-mode applications. Besides, closed-form explicit equations are readily available for the evaluation of component values. For verification, a PA operating at 1.8/2.6 GHz (non-concurrent), with three distinct saturation power levels (21, 23, 26 dBm) and peak efficiency of about 30%, is designed and fabricated using $0.35~{\mu }\text{m}$ CMOS process.

Development of Reconfigurable Plasma Column Antenna

Abstract: The work presented in this article evaluates the radiation characteristic of the plasma antenna in its classical state called plasma striation. The plasma antenna is basically a plasma column coupled with an RF signal source. The experimental setup of the plasma antenna has been developed, which includes a plasma and vacuum system, the RF signal source along with the matching network, and an automated radiation measurement system to measure the radiation parameters. The radiation characteristics of the plasma antenna depend on the plasma properties, such as plasma length and plasma density, which are the functions of input RF power and gas pressure. In a column, a single length plasma can be transformed into multiple small striations or blobs by having a critical combination of applied power and pressure. In this experiment, radiation patterns of antenna have been measured for the variable plasma parameters and tuned frequencies. The study reveals that the typical arrangement of blobs forms a collinear plasma antenna array, where the radiation parameters can be reconfigured with the size, number, and spacing between blobs and plasma density. The study outcomes the present useful development in the area of reconfigurable RF antenna that is a research interest in the field of radar for beamsteering applications and communication.

Large Signal RF Reliability of 45-nm RFSOI Power Amplifier Cell for Wi-Fi6 Applications

Abstract: A power amplifier cell having a single n-channel transistor fabricated in 45-nm RFSOI technology is stressed using both DC drain voltage as well as RF power at 7GHz applied to the gate reproducing Wi-Fi6 like operating conditions. Impact of the stress is studied using both DC as well as RF metrics. Impact on impedance matching is also studied using small signal characteristics. Through this work, we attempt to explore differences in hot carrier degradation mechanisms between DC and RF stress conditions. Impact of hot carrier degradation on DC and RF parameters is also presented by analyzing the time slope exponent. Degradation in DC and RF performance (small and large signal) is compared under varying stress conditions (DC, RF, and DC+RF).

A Planar Absorptive-Branch-Loaded Quasi-Yagi Antenna With Filtering Capability and Flat Gain

Abstract: A planar quasi-Yagi antenna with cointegrated filtering functionality and flat in-band gain is reported. It exploits complementary-diplexer-based reflectionless-filtering techniques through the inclusion of an absorptive branch to realize the codesigned filtering functionality. This absorptive branch consists of a second-order bandstop-filter (BSF) unit loaded by a grounded resistor that is connected in parallel with the initial planar quasi-Yagi antenna. By designing the reflection coefficients of the basic antenna and the absorptive branch to be nearly complementary in frequency, the out-of-band RF power not radiated by the antenna is transmitted by the BSF to its loading resistor that dissipates it. In this manner, a quasi-absorptive filtering action is added to the antenna. Moreover, whereas the out-of-band radiation efficiency of the antenna is highly suppressed, its in-band behavior is kept as the in-band RF power is not transmitted by the BSF but radiated by the antenna as usual. For the experimental-validation purposes, a microstrip antenna prototype is developed and measured. Flat in-band gain with a ripple lower than 1 dB within the operational range of the antenna (2.6–3.06 GHz) is obtained as an added merit.

Design, Characterisation and Performance of an Improved Portable and Sustainable Low-Field MRI System

Abstract: Low-field permanent magnet-based MRI systems are finding increasing use in portable, sustainable and point-of-care applications. In order to maximize performance while minimizing cost many components of such a system should ideally be designed specifically for low frequency operation. In this paper we describe recent developments in constructing and characterising a low-field portable MRI system for in vivo imaging at 50 mT. These developments include the design of i) high-linearity gradient coils using a modified volume-based target field approach, ii) phased-array receive coils, and iii) a battery-operated three-axis gradient amplifier for improved portability and sustainability. In addition, we report performance characterisation of the RF amplifier, the gradient amplifier, eddy currents from the gradient coils, and describe a quality control protocol for the overall system.

A New RF MEMS Power Sensor Based on Double-Deck Thermocouples With High Sensitivity and Large Dynamic Range

Abstract: This letter reports a new RF MEMS power sensor based on double-deck thermocouples with high sensitivity and a large dynamic range. In order to improve RF sensing capability and sensitivity, the double-deck thermocouples and a MEMS substrate membrane are carefully designed. The proposed RF MEMS power sensor is fabricated by GaAs monolithic microwave integrated circuit (MMIC) process coupled with MEMS technology. Experimental result shows that the output thermovoltage of the device has inherent RF–dc linearity with the power from 1 to 500 mW. And the measured return loss is less than −28.6 dB at 1–20 GHz, which exhibits excellent matching characteristics. Moreover, at 8, 10, and 12 GHz, the measured sensitivities are 133.2, 124.3, and $116.8~\mu \text{V}$ /mW, respectively. Compared with a traditional thermoelectric power sensor, the sensitivity and the dynamic range of the proposed RF MEMS power sensor are increased by approximately 61% and 2.5 times, respectively. The research work can be considered as an incremental improvement of the state of the art (higher power sensing capability and sensitivity) as RF power sensing using double-deck thermocouples.

33.9 A Hybrid Switching Supply Modulator Achieving 130MHz Envelope-Tracking Bandwidth and 10W Output Power for 2G/3G/LTE/NR RF Power Amplifiers

Abstract: Envelope tracking (ET) is a key technology improving efficiency of RF power amplifiers (PAs) and battery lifetime in mobile handsets. It has been commercialized since 4G LTE era, and is also being employed in 5G NR handsets. A supply modulator (SM) is a circuit generating power supplies of RF PAs for ET and average power tracking (APT) operations. Currently, the maximum channel BW and supported ET BW of 5G NR handset is 100MHz [1]–[4]. In a short time, over 100MHz BW will be necessary to support intra-band contiguous carrier aggregation cases of n77C/n78C/n79C in 3GPP standard [5]. The required instantaneous maximum output power of SM is about 10W which is calculated by the following parameters: 26dBm output power by power class 2 (PC2), 2dB loss of RF front-end module (FEM) due to complex operating band combinations (EN-DC for non-standalone mode, NE-DC, 2CA/3CA), 6dB higher instantaneous power due to peak-to-average power ratio (PAPR) at 1 resource block (RB), 1dB margin, and poor PA efficiency of around 33% (worst example) due to high carrier frequency of 5GHz at n79 band. The poor PA efficiency can be relaxed by high voltage PA design beyond 5V. In [1], a supply modulator with boosted output larger than battery voltage $(V_{BAT})$ is proposed, and the designed PA with 30% higher voltage shows 10% higher efficiency and broader BW owing to low impedance transformation ratio from $50 \Omega$ and small parasitic output capacitance of power cell. The challenge is how to design a supply modulator for 5G NR that can achieve both wide ET BW and high output voltage/power capability, while satisfying high efficiency, low receiver-band noise, short transition time, and multi-mode/standard operation.