RF Power Amplifier Research Articles

Comparative efficiency analysis of RF power amplifiers with fixed bias and envelope tracking bias

Comparative efficiency analysis of RF power amplifiers with fixed bias and envelope tracking bias

Foundry fabricated compact slow-light Mach-Zehnder modulator and photodetector for on-chip analog photonic computing

This work presents a scaling pathway of on-chip analog photonic computing using foundry-fabricated silicon electro-optic (EO) slow-light Mach-Zehnder modulators (SL-MZMs) and compact Ge photodetectors (PDs) to construct a computing unit. Two SL-MZMs with phase shifter (PS) lengths of 500 μm and 150 μm are studied in this work. The bit resolution, nonlinearity, clock frequency, and power consumption of the photonic computing link, including an RF amplifier, on-chip SL-MZM, and a PD, are thoroughly investigated. The computing link using the SL-MZM with 500 μm has demonstrated a low normalized mean square error (NMSE) of 0.0305 at 8-bit resolution under 3.2 GHz clock frequency. Under the setting of 6-bit resolution at a clock frequency of 800 MHz, high computing accuracy was achieved with a measured NMSE of 0.0018 using the SL-MZM with 150 μm PS length. Using the Google Speed Commands dataset to run a voice keyword spotting task, we determine that 6-bit resolution operating at 3.2 GHz achieves the optimal power-accuracy trade-off. We show a 20× improvement in energy efficiency and a 3.35× improvement in area efficiency compared to NVIDIA V100 GPU [“Volta: Performance and programmability,” IEEE Micro 38(2), 42 (2018)10.1109/MM.2018.022071134 ]. These results show that our compact SL-MZMs and PDs promise to scale up photonic computing for practical machine-learning applications.

Ultra-wideband GaN RF power amplifier based on low-pass ladder matching network

Ultra-wideband GaN RF power amplifier based on low-pass ladder matching network

Low-Cost Purpose-Built Ultra-Low-Field NMR Spectrometer.

Low-field NMR has emerged as a new analytical technique for the investigation of molecular structure and dynamics. Here, we introduce a highly integrated ultralow-frequency NMR spectrometer designed for the purpose of ultralow-field NMR polarimetry of hyperpolarized contrast media. The device measures 10 cm × 10 cm × 2.0 cm and weighs only 370 g. The spectrometer's aluminum enclosure contains all components, including an RF amplifier. The device has four ports for connecting to a high-impedance RF transmit-receive coil, a trigger input, a USB port for connectivity to a PC computer, and an auxiliary RS-485/24VDC port for system integration with other devices. The NMR spectrometer is configured for a pulse-wait-acquire-recover pulse sequence, and key sequence parameters are readily controlled by a graphical user interface (GUI) of a Windows-based PC computer. The GUI also displays the time-domain and Fourier-transformed NMR signal and allows autosaving of NMR data as a CSV file. Alternatively, the RS485 communication line allows for operating the device with sequence parameter control and data processing directly on the spectrometer board in a fully automated and integrated manner. The NMR spectrometer, equipped with a 250 ksamples/s 17-bit analog-to-digital signal converter, can perform acquisition in the 1-125 kHz frequency range. The utility of the device is demonstrated for NMR polarimetry of hyperpolarized 129Xe gas and [1-13C]pyruvate contrast media (which was compared to the 13C polarimetry using a more established technology of benchtop 13C NMR spectroscopy, and yielded similar results), allowing reproducible quantification of polarization values and relaxation dynamics. The cost of the device components is only ∼$200, offering a low-cost integrated NMR spectrometer that can be deployed as a plug-and-play device for a wide range of applications in hyperpolarized contrast media production─and beyond.

On forced RF generation of CW magnetrons for accelerators

CW magnetrons, initially developed for industrial RF heaters, were suggested to power RF cavities of superconducting accelerators due to their higher efficiency and lower cost than traditionally used klystrons, IOTs or solid-state amplifiers. RF amplifiers driven by a master oscillator serve as coherent RF sources. CW magnetrons are regenerative RF generators with a huge regenerative gain. This causes regenerative instability with a quite large noise when a magnetron operates with the anode voltage above the threshold of self-excitation. Traditionally, an injection locking by a small signal is used for stabilization of magnetrons. In this case CW magnetrons with the injection-locked oscillations generate a high level of noise. This may preclude use of standard CW magnetrons in this operating mode in the Superconducting RF (SRF) accelerators. In this article we described a method developed for forced RF generation of CW magnetrons when the magnetron startup is provided by the injected forcing signal and the regenerative noise is suppressed. The method is most suitable for powering high Q-factor cavities.

Design of PNP SiGe HBTs Towards 200 GHz fmax

Engineering SiGe HBTs with very high fT and fmax poses a significant challenge in the industry. Most technology iterations focus primarily on the improvement of the NPN performance for RF amplifiers, and a fast PNP device is often never offered. It is even more difficult to make high performance SiGe PNP transistors with comparable performance due to fundamental material and electrical limitations. However, the availability of a complementary device can enable several circuit applications including matched driver circuits and push-pull amplifiers. This paper applies lateral and vertical optimizations in a SiGe PNP, explores the performance scaling available and demonstrates a measured peak fT /fmax performance of 130/180 GHz at a BVCBO of 5.1 V.

Enhancing Security of Telemedicine Data: A Multi-Scroll Chaotic System for ECG Signal Encryption and RF Transmission.

Protecting sensitive patient data, such as electrocardiogram (ECG) signals, during RF wireless transmission is essential due to the increasing demand for secure telemedicine communications. This paper presents an innovative chaotic-based encryption system designed to enhance the security and integrity of telemedicine data transmission. The proposed system utilizes a multi-scroll chaotic system for ECG signal encryption based on master-slave synchronization. The ECG signal is encrypted by a master system and securely transmitted to a remote location, where it is decrypted by a slave system using an extended state observer. Synchronization between the master and slave is achieved through the Lyapunov criteria, which ensures system stability. The system also supports Orthogonal Frequency Division Multiplexing (OFDM) and adaptive n-quadrature amplitude modulation (n-QAM) schemes to optimize signal discretization. Experimental validations with a custom transceiver scheme confirmed the system's effectiveness in preventing channel overlap during 2.5 GHz transmissions. Additionally, a commercial RF Power Amplifier (RF-PA) for LTE applications and a development board were integrated to monitor transmission quality. The proposed encryption system ensures robust and efficient RF transmission of ECG data, addressing critical challenges in the wireless communication of sensitive medical information. This approach demonstrates the potential for broader applications in modern telemedicine environments, providing a reliable and efficient solution for the secure transmission of healthcare data.

A Unified Neural Network-Based Approach to Nonlinear Modeling and Digital Predistortion of RF Power Amplifier

A Unified Neural Network-Based Approach to Nonlinear Modeling and Digital Predistortion of RF Power Amplifier

(Electronics and Photonics Division Award) Research Advances Wide- and Ultrawide-Bandgap Power Switching Devices

Wide bandgap semiconductors such as SiC and GaN (WBG) and emerging ultrawide-bandgap materials such as Ga2O3, AlGaN, and Diamond (UWBG) represent the next-generation materials for high performance medium voltage and high voltage power switch technology. Such devices have a wide range of immediate Naval applications, including high-power satellite communications and radar, unmanned underwater and aerial vehicles, ship drive components, and hybrid vehicle inverters. Vertical SiC power device technology has matured rapidly over the past two decades, owing to advances in substrates, a fundamental understanding of epitaxial growth to eliminate performance-limiting defects, as well as device design breakthroughs. This has enabled breakthroughs in highly integrated module design for medium voltage power conversion with switching frequency >100 kHz. In parallel, lateral GaN-based high electron mobility transistor (HEMT) technology has been highly successful for RF power amplifiers and is well positioned to supersede GaAs-based microwave circuits. Recently, GaN-based vertical and lateral power devices have attracted significant interest due to promising device results coupled with progress in native substrate, epitaxial growth, and processing technology developments. This seminar will present an overview of the WBG/UWBG power device efforts at NRL. This research has four primary focus areas – 1) thermal management in III-N power device structures by diamond thin film integration, 2) characterization of substrate materials and homoepitaxial layers used for drift regions of power devices identify appropriate specifications and benchmark performance, 3) process module development, particularly for selective area doping by ion implantation, and 4) pilot production manufacturing of 1.2kV-class PiN diodes including reliability assessments to identify and mitigate performance limiting defects.

Optically powered FiWi system for B5G hybrid VLC/RF access networks

This paper proposes the concept and reports the demonstrator of an optically powered fiber/wireless (FiWi) system based on a hybrid visible light communication (VLC) and RF access network for beyond 5G (B5G) indoor applications. The power-over-fiber (PoF) technology is properly applied to simultaneously energize two components from the remote site, namely: a radio-over-fiber (RoF) module, which contains a photodetector and an RF amplifier; a red laser from the VLC system. The proposed PoF system is composed of a 500 m conventional multimode optical fiber (MMF) with a 62.5 μm core diameter, which enables the transmission of up to 12 W optical power with a power transmission efficiency (PTE) of 14%. In the proof of concept, 8.1 W optical power is generated to feed the 5G system components. Regarding the communication setup, a 5G new radio (5G NR) signal is initially transported through a RoF fronthaul, composed of 10 km of single-mode fiber (SMF), followed by the hybrid VLC/RF access network. The performance investigation of the B5G communication system is based on an analysis of the root mean square error vector magnitude (EVMRMS) parameter. Experimental results indicate 1.2 Gbps throughput in the VLC link using a 200 MHz bandwidth and 64-quadrature amplitude modulation (64-QAM), resulting in approximately 4.02% of EVMRMS. Moreover, the RF link at 3.5 GHz provides 360 Mbps with an EVMRMS of 2.67%. Finally, a comparison between the PoF system and conventional power supply validates the proposed approach's applicability for B5G wireless communications.

Block-Oriented Recurrent Neural Network for Digital Predistortion of RF Power Amplifiers

Block-Oriented Recurrent Neural Network for Digital Predistortion of RF Power Amplifiers

Sparsely Gated Mixture of Experts Neural Network For Linearization of RF Power Amplifiers

Sparsely Gated Mixture of Experts Neural Network For Linearization of RF Power Amplifiers

A low-cost, portable device for the study of the malaria parasite’s growth inhibition via microwave exposure

Recently, a novel method for the growth inhibition of malaria parasites using microwaves was proposed. However, the apparatuses used to demonstrate this method are high-cost and immovable, hindering the progression in this field of research, which is still in its early stages. This paper presents the redesign, construction, and validation of an equivalent system, converting it into a portable and low-cost system, capable of replacing the existing one. The proposed system is mainly composed of an RF generator (MAX2870), an RF amplifier (SKYWORKS 66292-11) and a graphical user interface. Likewise, the RF applicator proposed by the original study was redesigned, resulting in a five-fold improvement in return loss. The obtained results indicate that the proposed system achieves 90% parasite growth inhibition, matching the performance of its counterpart at less than 1% of its cost. These results represent a breakthrough for the creation of smaller, enhanced devices that open new possibilities for an alternative treatment to combat this devastating disease.

Recursive Neural Network With Phase-Normalization for Modeling and Linearization of RF Power Amplifiers

Recursive Neural Network With Phase-Normalization for Modeling and Linearization of RF Power Amplifiers

Complexity-Optimized Adaptive Model for Multiband Digital Predistortion of RF Power Amplifiers

Complexity-Optimized Adaptive Model for Multiband Digital Predistortion of RF Power Amplifiers

Miniaturized design of multi-octave PA using spoof surface plasmon polaritons

Surface Plasmon Polariton (SSPP), which exhibits subwavelength-scaled field confinement, can be realized at microwave frequencies by ultrathin corrugated metallic strips, providing significant potential for circuit and system miniaturization. A number of SSPP units were employed in this study to design input and output matching networks of a multi-octave RF power amplifier (PA) for the purpose of reducing the overall circuit size. The designed SSPP-based PAs were fabricated and demonstrated to have an output power between 39.1 dBm and 41.8 dBm, and a power added efficiency (PAE) ranging between 60.2 % and 69.8 % in the frequency range of 0.8 GHz to 3.1 GHz, with a size of 35.5 mm * 46.7 mm, which achieves a 47 % size reduction compared to the traditional transmission-line based PA. A highly efficient global optimization method, the Bayesian Optimization (BO), was utilized to further enhance performance. SSPP PA's average output power and PAE have been improved by approximately 0.3 dBm and 2.6 %, respectively. Its overall size remains at the same level. With the use of a 20 MHz 5GNR signal, digital pre-distortion (DPD) has been implemented, and the linearity of the PA has been improved.

Design of class f reconfigurable power amplifiers

With the rapid development of mobile communication technology, RF amplifier requirements becoming higher, miniaturization, high efficiency and multi-band have gradually become a research hotspot. Based on these hot research directions, this paper designs a dual-band reconfigurable power amplifier. The input of the amplifier adopts a stepped impedance matching network, which has a good matching effect in the 1.6 - 2.8 GHz band. The output is switched by a single-knife double-throw switch to the corresponding band output matching network to achieve the fast switching of different frequency bands. The RF amplifier tube is designed by using Cree’s GaN chip CGH40010F, which has an additional power efficiency of more than 60% in the frequency range of 1.7 - 1.9 GHz and 2.5 - 2.7 GHz bands, a gain of about 12 - 14 dB and a saturated output power of more than 40 dBm. This design has the features of high efficiency, high gain, miniaturization and multi-band, which is applicable to the mobile communication system.

Design, Implementation and Performance Analysis of RF Power Amplifier for 5G Mobile Communication in the Sub-6 GHz Band Using Advanced Node 18nm FinFET Technology

Design, Implementation and Performance Analysis of RF Power Amplifier for 5G Mobile Communication in the Sub-6 GHz Band Using Advanced Node 18nm FinFET Technology

Comprehensive study of Class‐‐E/F2 and inverse Class‐‐F power amplifiers for mm‐Wave systems utilizing 130 nm CMOS process

AbstractThis paper presents a comprehensive study of Class‐‐E/F2 and inverse Class‐‐F power amplifiers (PAs) designed for 35–42 GHz millimeter‐wave applications, utilizing a 130 nm CMOS process. The proposed RF PAs are well suited for wide frequency‐band millimeter‐wave and 5G radio transmitters. A comprehensive study of limiting factors in amplifier efficiency is presented in this paper. The study encompasses an analysis of all the factors that restrict the efficiency of the switched power amplifier. The first proposed power amplifier is based on the Class E/F2 architecture, comprising a parallel capacitor, second harmonic resonance circuit, and output matching network. Conversely, the second suggested power amplifier is constructed using the inverse Class‐‐F topology, which includes harmonic termination and matching networks. The harmonic termination circuit incorporates a second harmonic resonance network and utilizes a parasitic capacitor to control the harmonic components. Both the proposed Class E/F2 and inverse Class‐‐F architectures are employed to reshape the drain current and voltage waveforms, aiming to reduce the overlap between them and, consequently, improve efficiency. The suggested power amplifiers comprise a driver Class‐‐AB stage and a power stage constructed based on either the Class E/F2 architecture or inverse Class‐‐F topology, utilizing harmonic termination networks at the output load. Two new designs of high‐Q factor on‐chip finger capacitors have been implemented to improve efficiency and radio frequency performance. Achieving input matching and inter‐stage matching is facilitated by employing two novel on‐chip transformers designed for maximum power transfer. Additionally, an inter‐stage matching inductor is utilized in a cascode configuration to enhance the overall RF performance. The on‐chip transformers, inductors, and finger capacitors are designed using the HFSS software program. S‐parameter files (SNP files) of the designed on‐chip components are extracted and inserted into the simulation tool to ensure accurate results. The proposed Class E/F2 power amplifier achieves a constant power of 14.9 dBm, an extreme power added efficiency (PAE) of 11.7%, and a maximum gain of 13.74 dB. In contrast, the suggested inverse Class‐‐F power amplifier attains a constant power of 15.4 dBm, a peak PAE of 12.6%, and a maximum gain of 14.8 dB. The DC power consumption is 73 and 66 mW for the proposed Class E/F2 and inverse Class‐‐F PAs, respectively, while their active sizes are 0.14 and 0.2 mm2.

A Highly Flexible Passive/Active Discrete-Time Delta-Sigma Receiver

This paper presents a fourth-order discrete-time direct RF-to-digital Delta-Sigma receiver architecture for flexible receivers with a wide frequency range. The use of a current-driven passive mixer with RF feedback enables high-Q bandpass filtering and relaxes the linearity requirement of the RF amplifier. In addition, the reconfigurable passive/active loop filter offers a good compromise between power consumption, linearity, and dynamic range. The other important feature of the proposed architecture is the use of a sampling frequency that is a divisor of the LO frequency. This solves several problems such as the upmixing of quantization noise, the need to reconfigure the Delta-Sigma loop when changing the LO frequency, and the use of two independent clocks for the LO and the sampling frequency. The circuit was implemented using 65 nm CMOS technology. The I/Q Direct Delta-Sigma receiver has an RF bandwidth of 20 MHz and a sampling frequency of 400 MHz. Measurement results show a very high dynamic range of up to 80 dB with a peak SNDR of 46 dB for a power consumption of 46 mW at 800 MHz.