Radio Frequency Circuits Research Articles

IP2 optimization in frequency mixers using ferroelectric field-effect transistors

Ferroelectric devices have traditionally been utilized in memory circuits due to their ability to retain a polarization charge and potentially act as a nonvolatile storage device. Their usage in applications unrelated to memory has also previously expanded into other digital and analog circuits, and now, it is being investigated in radio frequency circuits. This work explores the implementation of a frequency mixer using ferroelectric field-effect transistors in order to demonstrate stability against voltage offsets in a single-balanced mixer, making use of the polarization in the switching transistors to improve the performance of the second-order intermodulation product.

Frequency multiplexing enables parallel multi-sample EPR

Electron paramagnetic resonance (EPR) spectroscopy stands out as a powerful analytical technique with extensive applications in the fields of biology, chemistry, physics, and material sciences. It proves invaluable for investigating the molecular structure and reaction mechanisms of substances containing unpaired electrons, such as metal complexes, organic and inorganic radicals, and intermediate states in chemical reactions. However, despite their remarkable capabilities, EPR systems face significant limitations in terms of sample throughput, as current commercial systems only target the analysis of one sample at a time. Here we introduce a novel scheme for conducting ultra-high frequency continuous-wave EPR (CW EPR) targeting the EPR spectroscopy of multiple microliter volume samples in parallel. Our proof-of-principle prototype involves two decoupled detection cells equipped with high qualty factor Q=104\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q=104$$\\end{document} solenoidal coils tuned to 488 and 589 MHz, ensuring a significant frequency gap for effective radio frequency (RF) decoupling between the channels. To further enhance electromagnetic decoupling, an orthogonal alignment of the coils was adopted. The paper further presents an innovative radiofrequency circuit concept that utilizes a single physical RF channel to simultaneously conduct parallel EPR on up to eight cells. Parallel EPR experiments on two BDPA samples, each with a sample volume of 18.3 μL, registered signal-to-noise ratios of 255 and 252 for the two EPR measurement cells, with no observable coupling. The showcased prototype, built using cost-effective commercially available fabrication technology, is readily scalable and represents an initial step with promising potential for advancing sample screening with high-throughput parallel EPR.

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].

Ultra-fast switching memristors based on two-dimensional materials

The ability to scale two-dimensional (2D) material thickness down to a single monolayer presents a promising opportunity to realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among 2D memristors and low switching energy (2pJ). Furthermore, we study the switching dynamics of these memristors using ultra-short (120ps-3ns) voltage pulses, a frequency range that is highly relevant in the context of modern complementary metal oxide semiconductor (CMOS) circuits. We employ statistical analysis of transient characteristics to gain insights into the memristor switching mechanism. Cycling endurance data confirms the ultra-fast switching capability of these memristors, making them attractive for next generation computing, storage, and Radio-Frequency (RF) circuit applications.

Multichannel coupling induced topological insulating phases with full multimerization

We propose and experimentally realize a class of quasi-one-dimensional topological lattices whose unit cells are constructed by coupled multiple identical resonators, with uniform hopping and inversion symmetry. In the presence of coupling-path-induced effective zero hopping within the unit cells, the systems are characterized by complete multimerization with degenerate −1 energy edge states for open boundary condition. Su–Schrieffer–Heeger subspaces with fully dimerized limits corresponding to pairs of nontrivial flat bands are derived from the Hilbert spaces. In particular, topological bound states in the continuum (BICs) are inherently present in even multimer chains, manifested by embedding the topological bound states into a continuous band assured by bulk-boundary correspondence. Moreover, we experimentally demonstrate the degenerate topological edge states and topological BICs in radio-frequency circuits.

Design and Simulation of Tunneling Diodes with 2D Insulators for Rectenna Switches.

Rectenna is the key component in radio-frequency circuits for receiving and converting electromagnetic waves into direct current. However, it is very challenging for the conventional semiconductor diode switches to rectify high-frequency signals for 6G telecommunication (>100 GHz), medical detection (>THz), and rectenna solar cells (optical frequencies). Such a major challenge can be resolved by replacing the conventional semiconductor diodes with tunneling diodes as the rectenna switches. In this work, metal-insulator-metal (MIM) tunneling diodes based on 2D insulating materials were designed, and their performance was evaluated using a comprehensive simulation approach which includes a density-function theory simulation of 2D insulator materials, the modeling of the electrical characteristics of tunneling diodes, and circuit simulation for rectifiers. It is found that novel 2D insulators such as monolayer TiO2 can be obtained by oxidizing sulfur-metal layered materials. The MIM diodes based on such insulators exhibit fast tunneling and excellent current rectifying properties. Such tunneling diodes effectively convert the received high-frequency electromagnetic waves into direct current.

Analysis of a Graphene FET-Based Frequency Doubler for Combined Sensing and Modulation through Compact Model Simulation

The ambipolar conduction property of graphene field-effect transistors (GFETs) and the inherent square-like dependence of the drain current on the gate voltage, enable the development of single-device architectures for analog nonlinear radiofrequency (RF) circuits. The use of GFETs in novel RF component topologies allows leveraging graphene’s attractive thermal and mechanical properties to improve the miniaturization and weight reduction of electronic components. These features are specifically appealing for integrated sensing, modulation, and transmission systems. However, given the innovative nature of emerging graphene-based technology, a complete performance analysis of any novel electronic component is essential for customizing the operating conditions accordingly. This paper presents a comprehensive circuital analysis of a GFET-based frequency doubler, exploiting a compact model for GFET circuit simulation to assess the device’s performance parameters, including power conversion gain bandwidth and saturation. The performed analysis proposes to support the design of GFET-based harmonic transponders, offering integrated sensing and signal manipulation capabilities.

Optimizing ultra-wideband balanced power amplifiers through the selection of different output impedance transformation based on SiP techniques

In this paper, two improved ultra-wideband (UWB) balanced power amplifiers based on the flip-chip system-in-package technique and electronic design automation (EDA) are proposed. The conventional approach to system-on-chip (SoC) involves integrating all sub-circuit designs into a single manufacturing process. However, in radio frequency circuits, adopting the SoC approach necessitates intricate matching designs, leading to an increase in development costs. In this study, two types of SiGe unit power amplifiers attempted to achieve a flat S21 response using simpler matching for input/output. The cascode architecture was adopted as the main structure for the first type of unit power amplifier (type I). Subsequently, the design of the second type unit power amplifier was built upon the foundation of the first type, with the only difference being the implementation of two parallel cascode structures (type II), and the primary goal is to enhance both gain and output power compared to the first type. In addition, for this second type unit power amplifier, in conjunction with a quadrature hybrid coupler, the optimal impedance matching value was selected to maintain the flatness of gain across the entire UWB range. Furthermore, the poor performance of S11,22 of these two types of unit power amplifiers was improved by using quadrature hybrid couplers using the WIPD process combined with EDA simulation. Therefore, using flip-chip packaging technology can effectively reduce the increased wafer fabrication costs caused by complex matching designs in active circuits. This improved system has the potential to offer a new practical application for UWB power amplifier design.

Design of Low Power Analog/RF Signal Processing Circuits Using 22 nm Silicon-on-Insulator Schottky Barrier Nano-Wire MOSFET

The gate-all-around (GAA) silicon-on-insulator (SOI) Schottky barrier (SB) nano-wire (NW) MOSFET was recently proposed for low-power and high-frequency analog and radio frequency (RF) circuits. But their use in low-power and high-frequency analog/RF circuits is still under investigation. In this work, basic analog signal processing circuits using gate-all-around SOI-SB-NW MOSFETs are designed for low-power and high-frequency applications. These basic and necessary analog processing circuits are designed for ± 0.3 V and ± 0.25 V power supplies to work on frequencies up to 10 GHz. The analog/RF characteristics of the GAA SOI-SB MOSFET are compared with those of the GAA SB NW MOSFET. The SOI-SB NW MOSFET shows improvements in early voltage, output resistance, and transconductance generation factor. The Silvaco TCAD simulator is used to obtain the results and perform numerical simulations. Simulation results show good analog/RF performance of the analog processing circuits.

Compact dual‐frequency impedance transformer for frequency‐dependent complex source and load

SummaryThis study presents a compact hybrid dual‐frequency impedance transformer that is suitable for sources and loads having frequency‐dependent complex impedances. The basic transformer comprises two transmission lines and two shunt stubs, and this configuration is adequate for the design of a dual‐frequency impedance transformer for a few sources and loads. Compared with other studies, this work presents a distinct derivation concept to obtain the circuit parameters, thus enabling the achievement of a compact circuit. For some particular sources and loads that the basic structure is difficult to match because of line width limitations, lumped elements are added to overcome the limitation and further reduce the circuit size. The derived design formulas avoid errors caused by frequency‐dependent deviations in the component values due to parasitic effects, which constitute a critical problem in Radio Frequency (RF) circuits that employ lumped elements. The simulated results are in good agreement with the measured results, and the frequency responses obtained herein validate the proposed structure and design procedure.

Wireless Detection of Trace Ammonia: A Chronic Kidney Disease Biomarker.

Elevated levels of ammonia in breath can be linked to medical complications, such as chronic kidney disease (CKD), that disturb the urea balance in the body. However, early stage CKD is usually asymptomatic, and mass screening is hindered by high instrumentation and operation requirements and accessible and reliable detection methods for CKD biomarkers, such as trace ammonia in breath. Enabling methods would have significance in population screening for early stage CKD patients. We herein report a method to effectively immobilize transition metal selectors in close proximity to a single-walled carbon nanotube (SWCNT) surface using pentiptycene polymers containing metal-chelating backbone structures. The robust and modular nature of the pentiptycene metallopolymer/SWCNT complexes creates a platform that accelerates sensor discovery and optimization. Using these methods, we have identified sensitive, selective, and robust copper-based chemiresistive ammonia sensors that display low parts per billion detection limits. We have added these hybrid materials to the resonant radio frequency circuits of commercial near-field communication (NFC) tags to achieve robust wireless detection of ammonia at physiologically relevant levels. The integrated devices offer a noninvasive and cost-effective approach for early detection and monitoring of CKD.

A 3D coaxial transition with continuous ground wall fabricated by a 12-inch wafer-level packaging method for radio frequency applications

Purpose This paper aims to realize the vertical interconnection in 3D radio frequency (RF) circuit by coaxial transitions with broad working bandwidth and small signal loss. Design/methodology/approach An advanced packaging method, 12-inch wafer-level through-mold-via (TMV) additive manufacturing, is used to fabricate a 3D resin-based coaxial transition with a continuous ground wall (named resin-coaxial transition). Designation and simulation are implemented to ensure the application universality and fabrication feasibility. The outer radius R of coaxial transition is optimized by designing and fabricating three samples. Findings The fabricated coaxial transition possesses an inner radius of 40 µm and a length of 200 µm. The optimized sample with an outer radius R of 155 µm exhibits S11 < –10 dB and S21 > –1.3 dB at 10–110 GHz and the smallest insertion loss (S21 = 0.83 dB at 77 GHz) among the samples. Moreover, the S21 of the samples increases at 58.4–90.1 GHz, indicating a broad and suitable working bandwidth. Originality/value The wafer-level TMV additive manufacturing method is applied to fabricate coaxial transitions for the first time. The fabricated resin-coaxial transitions show good performance up to the W-band. It may provide new strategies for novel designing and fabricating methods of RF transitions.

Analog RF Circuit Sizing by a Cascade of Shallow Neural Networks

A deep neural network architecture for the automatic sizing of analog circuit components is proposed, with a focus on radio frequency (RF) applications in the 2 to 5 GHz region. It addresses the challenges of the typically small number of examples for network training and the existence of multiple solutions, of which impractical values for integrated circuit implementation. We address these issues by restricting the learning to one component size at a time, thanks to a cascade of dedicated shallow neural networks (SNN), where each network constrains the prediction of the next ones. Moreover, the SNNs are individually tuned by a genetic algorithm for the prediction order and accuracy. This reduction of the solution space at each step allows the use of small training sets, and the introduced constraints between SNNs handle component interdependencies. The method is successfully validated on three different types of RF microcircuits: a low-noise amplifier (LNA), a voltage-controlled oscillator (VCO), and a mixer, using 180 nm and 130 nm CMOS implementations. All the predictions were within 5 % of the true values, both at the component and performance levels, and all the responses were obtained in less than 5 s, after 4 to 47 min. training on a regular PC station. The obtained results show that the proposed method is fast and applicable to arbitrary analog circuit topologies, with no need to retrain the developed neural network for each new set of desired circuit performances.

Instantaneous Viral Detection of SARS‐CoV‐2 and Beyond using Electromagnetic Sensing

AbstractThis study proposes a highly sensitive portable device that utilizes electromagnetic waves and data analytics for instantaneous Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS‐CoV‐2) detection. The device consists of a Radio Frequency (RF) circuit that interprets reflected and transmitted electromagnetic waves to identify virus signatures in physiologically significant matrices, including human saliva and diluted nasopharyngeal swabs. The sensor's accuracy is validated in both pre‐clinical and clinical settings, where clinical measurements demonstrate an instantaneous detection accuracy of 94%, sensitivity of 95%, and specificity of 97.5% between the sensor's physical parameters and SARS‐CoV‐2 detection. The sensor's accurate real‐time response is due to its unique design and precise modeling techniques. In addition, the same sensing system is tested across different viruses and its ability to differentiate between influenza A, respiratory syncytial, and SARS‐CoV‐2 viruses is proven. Hence this work presents a holistic system that can predict the viral concentration of SARS‐CoV‐2, as well as differentiate between different viruses instantaneously and without adding any amplifying agent.

Bipolar ablation of ventricular arrhythmias: Step-by-step.

Radiofrequency (RF) ablation of intramural ventricular arrhythmias (VAs) may require advanced ablation techniques to achieve effective energy transfer to the targeted tissue. As an alternative to standard RF ablation, catheter ablation can also be conducted in bipolar configuration when two ablation catheters participate in the RF circuit. This strategy has proved to result in deeper lesion formation and may be effective for eliminating arrhythmias that have been refractory to standard ablation. In this article, we provide a step-by-step guide on when and how to perform bipolar ablation of VAs.

Optical N-plasmon: topological hydrodynamic excitations in graphene from repulsive Hall viscosity

Edge states occurring in Chern and quantum spin-Hall phases are signatures of the topological electronic band structure in two-dimensional (2D) materials. Recently, a new topological electromagnetic phase of graphene characterized by the optical N-invariant was proposed. Optical N-invariant arises from repulsive Hall viscosity in hydrodynamic many-body electron systems, distinct from the Chern and Z 2 invariants. In this paper, we introduce the topologically protected edge excitation—optical N-plasmon of interacting many-body electron systems in the topological optical N-phase. These optical N-plasmons are signatures of the topological plasmonic band structure in 2D materials. We demonstrate that optical N-plasmons exhibit unique dispersion relations, stability against various boundary conditions, and edge profiles when compared with the topologically trivial edge magneto plasmons. Based on the optical N-plasmon, we design an ultra sub-wavelength broadband topological hydrodynamic circulator, which is a chiral quantum radio-frequency circuit component crucial for information routing and interfacing quantum–classical computing systems. Furthermore, we reveal that optical N-plasmons can be effectively tuned by the neighboring dielectric environment without breaking the topological properties. Our work provides a smoking gun signature of topological electromagnetic phases occurring in 2D materials arising from repulsive Hall viscosity.

Versatile On-Chip Programming of Circuit Hardware for Wearable and Implantable Biomedical Microdevices.

Wearable and implantable microscale electronic sensors have been developed for a range of biomedical applications. The sensors, typically millimeter size silicon microchips, are sought for multiple sensing functions but are severely constrained by size and power. To address these challenges, a hardware programmable application-specific integrated circuit design is proposed and post-process methodology is exemplified by the design of battery-less wireless microchips. Specifically, both mixed-signal and radio frequency circuits are designed by incorporating metal fuses and anti-fuses on the top metal layer to enable programmability of any number of features in hardware of the system-on-chip (SoC) designs. This is accomplished in post-foundry editing by combining laser ablation and focused ion beam processing. The programmability provided by the technique can significantly accelerate the SoC chip development process by enabling the exploration of multiple internal circuit parameters without the requirement of additional programming pads or extra power consumption. As examples, experimental results are described for sub-millimeter size complementary metal-oxide-semiconductor microchips being developed for wireless electroencephalogram sensors and as implantable microstimulators for neural interfaces. The editing technique can be broadly applicable for miniaturized biomedical wearables and implants, opening up new possibilities for their expedited development and adoption in the field of smart healthcare.

Enhancing the brain MRI at ultra-high field systems using a meta-array structure.

The main advantage of ultra-high field (UHF) magnetic resonance neuroimaging is theincreased signal-to-noise ratio (SNR) compared with lower field strength imaging. However, the wavelength effect associated with UHF MRI results in radiofrequency (RF) inhomogeneity, compromising whole brain coverage for many commercial coils. Approaches to resolving this issue of transmit field inhomogeneity include the design of parallel transmit systems (PTx), RF pulse design, and applying passive RF shimming such as high dielectric materials. However, these methods have some drawbacks such as unstable material parameters of dielectric pads, high-cost, and complexity of PTx systems. Metasurfaces are artificial structures with a unique platform that can control the propagation of the electromagnetic (EM) waves, and they are very promising for engineering EM device. Implementation of meta-arrays enhancing MRI has been explored previously in several studies. The aim of this study was to assess the effect of new meta-array technology on enhancing the brain MRI at 7T. A meta-array based on a hybrid structure consisting of an array of broadside-coupled split-ring resonators and high-permittivity materials was designed to work at the Larmor frequency of a 7 Tesla (7T) MRI scanner. When placed behind the head and neck, this construct improves the SNR in the region of the cerebellum,brainstem and the inferior aspect of the temporal lobes. Numerical electromagnetic simulations were performed to optimize the meta-array design parameters and determine the RF circuit configuration. The resultant transmit-efficiency and signal sensitivity improvements were experimentally analyzed in phantoms followed by healthy volunteers using a 7T whole-body MRI scanner equipped with a standard one-channel transmit, 32-channel receive head coil. Efficacy was evaluated through acquisition with and without the meta-array using two basic sequences: gradient-recalled-echo (GRE) and turbo-spin-echo (TSE). Experimental phantom analysis confirmed two-fold improvement in the transmit efficiency and 1.4-fold improvement in the signal sensitivity in the target region. In vivo GRE and TSE images with the meta-array in place showed enhanced visualization in inferior regions of the brain, especially of the cerebellum, brainstem, and cervical spinal cord. Addition of the meta-array to commonly used MRI coils can enhance SNR to extend the anatomical coverage of the coil and improve overall MRI coil performance. This enhancement in SNR can be leveraged to obtain a higher resolution image over the same time slot or faster acquisition can be achieved with same resolution. Using this technique could improve the performance of existing commercial coils at 7T for whole brain and other applications.

Structural, Physical, Magnetic, and Dielectric Study of Glassy and Crystalline Bismuth Zinc Silicates

AbstractThe current study aims to thoroughly analyze the optical, magnetic, and dielectric properties of the glass and glass-ceramics in the system Bi2O3.ZnO.SiO2 with stoichiometric composition xBi12SiO20.(100-x)Zn2SiO4(x = 0, 10, 30, 50, 70, 90, and 100). The systematic dependence on density, Bi2O3, and the presence of interphases was studied. Fourier transform infrared (FTIR) spectra of the glass-ceramic samples certify the changes occurring in structure from amorphous to crystalline form where more intense, sharp, narrow bands were observed. Both 10B and 30B samples display more ultraviolet (UV) absorbance than the remaining samples. Upon introducing Bi2O3, the glass sample's color gradually changed from brown to pale yellow. In the vibrating sample magnetometer (VSM) study, the highest (9.22 × 10-7 emu/g) and lowest (4.53 × 10-7 emu/g) magnetic susceptibility were noticed for 30B and 70B samples, respectively. Further, all glass ceramics display diamagnetic properties due to the existence of Bi ions. The glass-ceramic samples showed better dielectric properties than glass samples due to changes from the amorphous nature of the glassy phase (high dielectric loss) to the well-ordered structure of the corresponding glass-ceramic (low dielectric loss). The glass ceramic sample of 100B attained much lower dielectric loss values (0.002, f = 106 Hz) than the corresponding glass sample (0.01, f = 106Hz) which could be helpful for electric storage devices, i.e. capacitors, supercapacitors, batteries, etc. Besides, the high-quality factor (Q = 2758) of the same glass-ceramic sample makes it promising in Radio Frequency (RF) circuits or other high- frequency applications.

Film bulk acoustic resonators with 400 MHz ultrawide-range tunability using crystalline PZT thin film

Tunable and switchable film bulk acoustic resonators (FBARs) have great application potential owing to their much-increased flexibility in radiofrequency (RF) circuits. Here, we report on the design and fabrication of a tunable and switchable FBAR based on a thin crystalline lead zirconate titanate (PZT, Pb[Zr0.6Ti0.4]O3) film. The FBAR device has a resonant frequency of 2.42 GHz with a high effective electromechanical coupling coefficient keff2 of 30%. The frequency tunable range of the device is up to 400 MHz (2.11–2.51 GHz, 16.6%) with a DC bias voltage of less than 12 V, and the device can also be switched off when the polarization intensity in the PZT film is zero. Through the investigation, a relationship between the ferroelectric nature of PZT material and the wide tuning range of FBAR is established, providing a theoretical and experimental guideline for further development.