Radio Power Research Articles

Inverse “Foldover” Resonance in an Yttrium Iron Garnet Film

Nonlinear magnetic resonance is studied in an in-plane magnetized yttrium iron garnet (YIG) film. For YIG films magnetized perpendicular to the plane, the effect referred to as the foldover resonance is well known. It arises because the precession frequency increases with the deviation of the magnetization. When the field is reduced, the frequency of the precession remains resonant because the demagnetizing field decreases with the deviation of the magnetization. The signal disappears when the radio frequency pump power is insufficient to maintain a nonequilibrium state of the system. In the in-plane magnetized yttrium iron garnet film, the precession frequency decreases with an increase in the pump amplitude. Accordingly, the foldover effect arises under an increase in the field. The fundamental difference is that the precession in the latter case should be unstable with respect to the decay into spin wave modes. The deviation angles of magnetization of about 10° are reached, and the rate of decay of the uniform precession into spin waves, which depends on the deviation angle of the magnetization, is measured. This study opens up another way of achieving the magnon density corresponding to the formation of its Bose–Einstein condensate.

Pulsed chemical vapor deposition for crystalline aluminum nitride thin films and buffer layers on silicon and silicon carbide

Low temperature aluminum nitride (AlN) deposition has applications ranging from serving as a heat spreading material to serving as a buffer layer for III-V semiconductors on silicon or silicon carbide (SiC) for radio frequency, power, and microLED devices. While crystalline AlN is traditionally deposited at high temperature (>800 °C), in the present study AlN is deposited on Si(100), Si(111), and 4H-SiC substrates by two modest temperature processes using a metal precursor with high thermal stability, tris(dimethylamido) aluminum (III), and a highly reactive nitrogen source, anhydrous hydrazine. A 580 °C pulsed chemical vapor deposition (CVD) process is compared to a more complex 400 °C atomic layer annealing process, in which the same precursors are utilized with periodic ion bombardment to induce film crystallinity. Films deposited by both processes template preferential c-axis orientation in subsequently sputtered AlN on unheated substrates. Both templating techniques demonstrate equivalent enhancements in crystallinity of the sputtered AlN relative to a non-templated sputtered film by x-ray diffraction and transmission electron microscopy studies. On 4H-SiC substrates, a comparison of sputtering directly and templating with the 580 °C pulsed CVD process reveals epitaxial deposition by the 580 °C pulsed CVD process which extends into the low temperature sputtered AlN.

Low-Temperature Direct Synthesis of Multilayered h-BN without Catalysts by Inductively Coupled Plasma-Enhanced Chemical Vapor Deposition.

Low-temperature direct synthesis of thick multilayered hexagonal-boron nitride (h-BN) on semiconducting and insulating substrates is required to produce high-performance electronic devices based on two-dimensional (2D) materials. In this study, multilayered h-BN with a thickness exceeding 5 nm was directly synthesized on quartz and Si at low temperatures, between 400 and 500 °C, by inductively coupled plasma-enhanced chemical vapor deposition using borazine as the precursor material. The quality and thickness of the h-BN crystals were investigated with respect to synthesis parameters, namely, temperature, radio frequency power, N2 flow rate, and H2 flow rate. Introducing N2 and H2 carrier gases critically affected the deposition rate, and increasing the carrier gas flow rate enhanced the h-BN crystal quality. The typical optical band gap of synthesized h-BN was approximately 5.8 eV, consistent with that of previous studies. The full width at half-maximum of the h-BN Raman peak was 32-33 cm-1, comparable to that of commercially available multilayered h-BN on Cu foil. These results are expected to facilitate the development of 2D materials for electronics applications.

Application of a Trellis Coded Modulation to Ameliorate the 5G Communication for Tropical Regions

Objectives: To minimize the bit error rate and enhance the radio signal power by an application of the Trellis Coded Modulation (TCM) for the Fifth Generation (5G) technology in tropical regions. Methods: Various diversity techniques have been adopted to diminish the Bit Error Rate. A Communication link model has been proposed in this work and an STBC MIMO system (Space-Time Block Coding multiple-input multiple-output) has been applied to enhance the diversity gain and coding gain of the proposed model. The said model has been implemented in this work for tropical regions for increasing the radio signal power. Findings: The basic climatic feature of tropical regions is a heavy amount of rainfall throughout the year. Because of such rainfall, the radio signal power in these regions gets diminished, and the Bit Error Rate (BER) increases. By applying the proposed communication link model in the tropical regions the Bit Error Rate has been reduced. The values of the Bit Error Rate of the proposed model have been obtained for Rayleigh distribution, Rician distribution and various MIMO techniques. Novelty: A hardware cosimulation block and a 4x4 STBC MIMO has been developed with its subsequent verification on Xilinx Kintex-7 FPGA board. Keywords: Bit error rate; MIMO Systems; Xilinx system generator; Trellis coded modulation; FPGA; Signal attenuation

Self-excitation of radio waves in the metal–insulator–metal structure doped with metal nanowires

The effect of self-excitation of radio waves in the metal–insulator–metal structure doped with metal nanowires is predicted and its theory is developed. Both the transient stage of self-excitation and the steady-state regime of self-oscillation are analyzed in a fully analytical form. The numerical estimates demonstrate that this effect can be used for diverse practical purposes, in particular, for radio frequency wireless power harvesting. These findings extend the approach developed in nano-optics to the field of electrical engineering.

Bandwidth-Efficient Generalized Differential Spatial Modulation

Differential spatial modulation (DSM) can transmit additional data bits by selecting indexes of antennas without the pilot overhead and increasing radio frequency circuits and power consumption. DSM is extended to generalized DSM (GDSM) where more than one transmit antennas are activated each time. However, the transmission rate of the existing GDSM scheme is low. In this paper, we propose a new GDSM scheme that uses symbol interleaving on differential space-time modulation. The number of interleaving patterns is derived, and interleaving patterns with transmit diversity two are created as well. By selecting the interleaving patterns, the proposed scheme has higher data rates than the existing GDSM scheme. We also propose low-complexity detectors for both schemes. Theoretical analysis and computer simulation both show that the proposed scheme has satisfactory error performance.

THE COMPUTER MODELING OF CLASS -D AND -DE SWITCHING-MODE POWER AMPLIFIERS FOR VHF DIGITAL RADIO BROADCAST EQUIPMENT

Currently the transition to digital VHF radio broadcasting is being discussed more and more in different countries, which requires the design of new radio broadcast equipment devices. In classical method of amplifying the power of complex radio signals with a variable envelope, the new broadcast equipment will lose significantly to the existing broadcast equipment with frequency-modulated signal in many energy parameters. The most the promising ways to build high-efficiency broadcast equipment devices of complex radio signals with amplitude-phase modulation and high peak-factor are synthetic methods of linear amplification of radio frequency power (for example, basing on the scheme of L. Kahn) by using high-efficiency switching-mode circuits of powerful amplification. The present state of development of powerful radio-frequency transistors allows to assume that in the near future in the VHF-band switching-mode power amplifiers of Class -D and -F, which will be suitable for building digital radio broadcast equipment with the polar architecture of L. Kahn, will be everywhere used. These switching-mode amplifiers, in contrast to higher-frequency Class-E circuits, supply more steady characteristics in the frequency band. But when developing such broadcast equipment, it is also reasonable to deal with modified switching-mode power amplifiers of the Class -DE and -FE. The article deals with the questions of the computer modeling of switching- mode power amplifiers of Class -D and -DE in relation to the design of VHF radio broadcast equipment.

CONVECTIVE HEAT TRANSFER OF HEAT SINKS WITH PARTIALLY CUT PLATE FINS AND TURNING OF THEIR CUT SECTIONS

Plate-fin heat sinks are widely used for cooling radio electronic, power electronic, and telecommunication components. The current trends in the development of radio and microelectronic systems dictate the need to dissipate large heat fluxes. The present article uses the methods of numerical simulation, verified by experimental data, to study convective heat transfer of different-type heat sinks with partially cut plate fins. The heat sink with partially cut plate fins served as the basis of study. Three types of heat sinks with extended surfaces were also considered. First, we analyzed the fin cut section turned at an angle of 30° and then - the fin cut section with diverging or converging shape. Comparing the thermal and hydraulic performance of such heat sinks showed that the thermal and hydraulic performance of heat sinks with a fin cut section with diverging shape at a turning angle of 30° is by 10% higher than that of heat sinks with partially cut plate fins. As the velocity distribution in the wake shows, the use of heat sinks with partially cut plate fins and turning of their cut sections for cooling real microelectronic devices needs to correctly design an installation, in which the device is located.

Mathematical model of the UAV landing approach system on the example of the course-glide path system

A mathematical model of the landing approach system for an unmanned aerial vehicle (UAV) on the example of a course-glide path system (СGS) is presented. The proposed mathematical model includes an information model of the ground and airborne segments operation for the approach system. The mathematical model of the ground segment implements the calculation of the CGS radio signals power level at a given point in space — the position of the UAV. The mathematical model of the onboard segment implements the determination of the UAV getting into the radio beacon coverage area and the calculation of the UAV deviation angles from the glide path line. The UAV dynamics model is considered as a set of pre-obtained trajectory points. The carried out computational experiments showed the fundamental adequacy of the mathematical model and its application possibility for checkout automatic control systems for aircraft-type UAVs during landing approach. Keywords UAV, landing approach system, course-glide path system, localizer, glide path radio beacon, marker beacon, mathematical model, UAV landing

The Beaming Effect for Fermi-LAT-detected FR-I Radio Galaxies

Our knowledge of Giga-electron volt (GeV) radio galaxies has been revolutionized by the Fermi-LAT Telescope, which provides an excellent opportunity to study the physical properties of GeV radio galaxies. According to the radio power and morphology, radio galaxies can be separated into Fanaroff–Riley Type I radio galaxies (FR-Is) and Type II radio galaxies (FR-IIs). In this paper, we consider the unification of FR-Is and BL Lacertae objects (BL Lacs), and assume FR-Is to be a standard candle to discuss the beaming effect for Fermi-LAT-detected FR-Is. Our main conclusions are as follows: (1) The estimated Doppler factors for 30 Fermi-LAT-detected FR-Is are in a range of δ I = 0.88 − 7.49. The average Doppler factor (〈δ I〉 = 2.56 ± 0.30) of the 30 FR-Is is smaller than that (〈δ BL〉 = 10.28 ± 2.03) of the 126 Fermi-LAT-detected BL Lacs, supporting the unification model that FR-Is are regarded as the misaligned BL Lacs with smaller Doppler factors; (2) We propose that different regions of FR-Is in the plot of the γ-ray luminosity against the photon spectral index may indicate the different beaming effects; (3) The average Doppler factor of the 6 TeV FR-Is is similar to that of the 24 non-TeV FR-Is, which implies that the difference between the TeV and GeV emissions is not driven by the beaming effect in the Fermi-LAT-detected FR-I samples.

DC-10 GHz broadband linear power amplifier for 5G applications using 180 nm CMOS technology

This article suggests a broadband linear power amplifier (PA) for DC-10 GHz for Fifth-generation (5G) and multi-standard applications using 180 nm CMOS technology. The suggested radio frequency power amplifier is appropriate for wideband LTE, IoT, WSN, multi-standard, and 5G radio frequency transmitters. T-coil peaking and bridged-shunt-series peaking amplifiers are used for bandwidth extension and gain flatness. Also, the interstage matching inductors between common source and common gate transistors are applied to improve radio frequency achievement. The suggested PA consists of four stages as follows; input stage, two stages using the T-coil peaking technique, and the last stage utilizing bridged-shunt-series peaking topology. The input stage is a complementary current reuse (CCR) common gate with active shunt feedback (SFB) architecture. It is utilized to extend the matching of RF input impedance with agreeable linearity and power gain at little power consumption. The second stage works in class-C operation to enhance the efficiency and reduce DC power consumed whereas the class-AB mode is utilized in the third and fourth stages to improve the output power. The suggested PA obtains a peak constant power equal to 14.25 dBm, a maximum Power-Added-Efficiency (PAE) of 16 %, and a peak gain equal to 22 dB. The proposed power amplifier dissipates a DC power of 80 mW. The die size of the proposed power amplifier equals 1mm2, whereas the total chip size includes the pads is 1.62mm2.

Deep low-frequency radio observations of Abell 2256

We present the first detailed analysis of the radio halo in the merging galaxy cluster Abell 2256 using the LOw Frequency ARray, the upgraded Giant Metrewave Radio Telescope, and the Karl G. Jansky Very Large Array. Radio observations (120 MHz–2 GHz) combined with archival Chandra and XMM-Newton X-ray data allowed us to study the central radio halo emission with unprecedented detail. The integrated radio emission from the entire halo is characterized by an ultra-steep spectrum, which can be described by a power law with α144 MHz1.5 GHz = −1.63 ± 0.03 and radial steepening in the outer regions. The halo is significantly underluminous according to the current scaling relations between radio power and mass at 1.4 GHz, not at 150 MHz; ultra-steep spectrum halos are predicted to be statistically underluminous. Despite the complex structure of this system, the halo morphology is remarkably similar to that of the X-ray emission. The radio surface brightness distribution across the halo is strongly correlated with the X-ray brightness of the intracluster medium. The derived correlations show sublinear slopes and distinct structures: the core is IR ∝ IX1.51, the outermost region IR ∝ IX0.41, and we find radio morphological connections with X-ray discontinuities. We also find a strong anticorrelation between the radio spectral index and the X-ray surface brightness, implying radial steepening. We suggest that the halo core is either related to old plasma from previous active galactic nuclei activity, being advected, compressed, and reaccelerated by mechanisms activated by the cold front or less turbulent with strong magnetic field in the core. The change in the radio versus X-ray correlation slopes in the outer regions of the halo could be due to a radial decline of the magnetic field, the increase in the number density of seed particles, or increasing turbulence. Our findings suggest that the emitting volume is not homogenous according to turbulent reacceleration models.

Diffuse radio source candidate in CIZA J1358.9−4750

AbstractWe report on results of our upgraded Giant Metrewave Radio Telescope (uGMRT) observations for an early-stage merging galaxy cluster, CIZA J1358.9−4750 (CIZA1359), in Band-3 (300–500 MHz). We achieved the image dynamic range of ∼38000 using the direction dependent calibration and found a candidate of diffuse radio emission at 4σrms significance. The flux density of the candidate at 400 MHz, 24.04 ± 2.48 mJy, is significantly positive compared to noise, where its radio power, 2.40 × 1024 W Hz−1, is consistent with those of typical diffuse radio sources of galaxy clusters. The candidate is associated with a part of the X-ray shock front at which the Mach number reaches its maximum value of $\mathcal {M}\sim 1.7$. The spectral index (Fν ∝ να) of the candidate, α = −1.22 ± 0.33, is in agreement with an expected value derived from the standard diffusive shock acceleration (DSA) model. However, such a low Mach number with a short acceleration time would require seed cosmic rays supplied from active galactic nucleus (AGN) activities of member galaxies, as suggested in some other clusters. Indeed, we found seven AGN candidates inside the diffuse source candidate. Assuming the energy equipartition between magnetic fields and cosmic rays, the magnetic field strength of the candidate was estimated to be 2.1 μG. We also find head–tail galaxies and radio phoenixes or fossils near CIZA1359.

Extended radio emission in the galaxy cluster MS 0735.6+7421 detected with the Karl G. Jansky Very Large Array

ABSTRACT MS 0735.6+7421 (z = 0.216) is a massive cool core galaxy cluster hosting one of the most powerful active galactic nuclei (AGNs) outbursts known. The radio jets of the AGN have carved out an unusually large pair of X-ray cavities, each reaching a diameter of 200 kpc. This makes MS 0735.6+7421 a unique case to investigate active galactic nuclei feedback processes, as well as other cluster astrophysics at radio wavelengths. We present new low radiofrequency observations of MS 0735.6+7421 taken with the Karl G. Jansky Very Large Array (VLA): 5 h of P-band (224–480 MHz) and 5 h of L-band (1–2 GHz) observations, both in C configuration. Our VLA P-band (224–480 MHz) observations reveal the presence of a diffuse radio component reaching a scale of ≈ 900 kpc in the direction of the jets and of ≈ 500 kpc in the direction perpendicular to the jets. This component is centred on the cluster core and has a radio power scaled at 1.4 GHz of P1.4GHz = (4 ± 2) × 1024 W Hz−1. Its properties are consistent with those expected from a radio minihalo as seen in other massive cool core clusters, although it may also be associated with radio plasma that has diffused out of the X-ray cavities, or to a combination of these two hypotheses. Observations at higher spatial resolution are needed to fully characterize the properties and nature of this component. We also suggest that if radio minihaloes originate from jetted activity, we may be witnessing the early stages of this process.

Joint power and hopping rate adaption against follower jammer based on deep reinforcement learning

AbstractAs an effective anti‐jamming approach, frequency‐hopping (FH) technology has been widely applied to tactical communication system, providing reliable communication guarantee and improving resilience against conventional interference under strong confrontation environment. Key challenges for tactical wireless communication network face are the smart follower jammer with responsive spectrum reconnaissance and intelligent decision‐making capabilities. In response, this article investigates a deep reinforcement learning based anti‐jamming scheme, with the aim of maximizing the system throughput. The interactions between a radio transmitter and a smart follower jammer are formulated as a hierarchical anti‐jamming dynamic game model, in which the radio terminal decides transmission power and hopping rate according to the state feedback information, and the jammer chooses spectrum scanning rate accordingly to minimizing the rewards of the FH communication system. We prove that there is a Nash equilibrium (NE) strategy for static and dynamic environment in the game. A double deep Q‐network with prioritized experience reply (PDDQN) based anti‐jamming scheme is proposed to approximating the optimal power control and hopping strategy without being aware of the environment and jamming parameters. Finally, simulation results demonstrate that the proposed algorithm efficiently provide better throughput and jamming resistance.

An Elusive Population of Massive Disk Galaxies Hosting Double-lobed Radio-loud Active Galactic Nuclei

It is commonly accepted that radio-loud active galactic nuclei are hosted exclusively by giant elliptical galaxies. We analyze high-resolution optical Hubble Space Telescope images of a sample of radio galaxies with extended double-lobed structures associated with disk-like optical counterparts. After systematically evaluating the probability of chance alignment between the radio lobes and the optical counterparts, we obtain a sample of 18 objects likely to have genuine associations. The host galaxies have unambiguous late-type morphologies, including spiral arms, large-scale dust lanes among the edge-on systems, and exceptionally weak bulges, as judged by the low global concentrations, small global Sérsic indices, and low bulge-to-total light ratios (median B/T = 0.13). With a median Sérsic index of 1.4 and low effective surface brightnesses, the bulges are consistent with being pseudobulges. The majority of the hosts have unusually large stellar masses (median M * = 1.3 × 1011 M ⊙) and red optical colors (median g − r = 0.69 mag), consistent with massive, quiescent galaxies on the red sequence. We suggest that the black hole mass (stellar mass) plays a fundamental role in launching large-scale radio jets, and that the rarity of extended radio lobes in late-type galaxies is the consequence of the steep stellar mass function at the high-mass end. The disk radio galaxies have mostly Fanaroff–Riley type II morphologies yet lower radio power than sources of a similar type traditionally hosted by ellipticals. The radio jets show no preferential alignment with the minor axis of the galactic bulge or disk, apart from a possible mild tendency for alignment among the most disk-dominated systems.

Differential Privacy and IRS Empowered Intelligent Energy Harvesting for 6G Internet of Things

In the era of the sixth generation (6G), the deployment of massive Internet of Things (IoT) generates and processes large amounts of data, resulting in high energy demand and huge challenges to the energy-limited IoT devices. To achieve green and sustainable communication, energy harvesting is a feasible technology to prolong the lifetime of IoT. However, the existing energy harvesting architecture cannot guarantee the privacy of energy users while improving the intelligence and effectiveness of energy transmission. To solve these issues, we propose a differential privacy and intelligent reflecting surface empowered privacy-preserving energy harvesting framework for 6G-enabled IoT. First, a secure and intelligent energy harvesting framework is designed, which includes an intelligent reflecting surface-aided radio frequency power transmission mechanism and a differential privacy-based energy harvesting mechanism. Second, an exponential mechanism-based privacy-preserving energy harvesting scheme is established, where we analyze the adversary mode, propose the differential privacy-enabled location-preserving algorithm, and provide security analysis and proof. Third, we quantify the user satisfaction for energy harvesting and propose a deep reinforcement learning empowered resource allocation scheme to maximize the weighted satisfaction of all system users. Finally, simulation results show the effectiveness of the proposed secure and intelligent energy harvesting architecture for 6G IoT.

Thermal property evaluation of a 2.5D integration method with device level microchannel direct cooling for a high-power GaN HEMT device

Gallium nitride high electron mobility transistor (GaN HEMT) devices have become critical components in the manufacturing of high-performance radio frequency (RF) or power electronic modules due to their superior characteristics, such as high electron saturation speeds and high power densities. However, the high heat characteristics of GaN HEMTs make device level cooling a critical problem to solve since performance degradation or even failure may occur under high temperatures. In this paper, we proposed a 2.5D integration method with device-level microchannel direct cooling for a high-power GaN HEMT device. To demonstrate this technological concept, a multigate GaN HEMT device featuring a gate length/width/source drain spacing of 0.5 μm/300 μm/6 μm that underwent in-house backside thinning and metallization was used as the test vehicle. A high-resistivity silicon (HR Si) interposer embedded with four-layer microchannels was designed, having widths/pitches of 30 μm/30 μm at the top microchannel. The high-power GaN HEMT device was soldered on a Si interposer embedded with open microchannels for heat dissipation. A pair of GSG Pad chips was soldered simultaneously to display the capacity for the heterogeneous integration of other chip types. Thermal property evaluation was conducted with experiments and simulations. The test results showed that the maximum surface temperature of the GaN HEMT device decreased to 93.8 °C when it experienced a heat dissipation density of 32 kW/cm2 in the gate finger area and an average heat dissipation density of 5 kW/cm2 was found in the active area with the DI water coolant at a flow rate of 3 mL/min. To our knowledge, among recently reported works, this finding was the best cooling capacity of heterogeneously integrated microchannels for GaN HEMT devices. In addition, this technology was scalable regarding the numbers of gate fingers or GaN HEMT devices.

Three-Level Hybrid Envelope Tracking Supply Modulator with High-Bandwidth Wide-Output-Swing

Envelope tracking is a dynamic supply modulation technique, which is mainly used to improve the efficiency of radio frequency power amplifier. For 5G NR mobile devices, this paper presents an envelope tracking supply modulator which is composed of a three-level switching converter and linear amplifier (LA) in parallel. The hysteresis control method is adopted in the supply modulator to improve the bandwidth of the switching converter and the loop response speed. At the same time, a rail-to-rail input-output class AB linear amplifier is designed to achieve a wide output swing and a super source follower is proposed to reduce the output impedance of LA. Designed with the 180 nm CMOS technology, the supply modulator operated at 5G NR 100 MHz envelope signal. The output power of the modulator reaches 1.5 W for a 6 Ω load resistor and the output swing is 4.3 V at 5.0 V supply, and the maximum efficiency reaches 85%.

Design and Evaluation of Self-Cooling Electrodes for Radiofrequency Intestinal Anastomosis

Abstract Colorectal cancer is a common malignant tumor in the gastrointestinal tract. Resection of the cancerous site and anastomosis of the residual intestine is the preferred radical treatment for colorectal cancer. In particular, radio frequency energy anastomosis of the residual intestine is being increasingly used in clinical practice. To improve the quality of anastomosis, reduce the thermal damage of tissue near the anastomosis area, and avoid foreign body residue in this area, we propose a self-cooling eversion-type radio frequency-energy intestinal anastomosis electrode, which is analyzed through simulations and evaluated experimentally for welding intestinal tissue. For radio frequency energy power of 160 W, anastomosis time of 13.2 s, and pressure of 154 kPa, the disconnected intestinal tissues can be anastomosed using the proposed electrode. The average burst pressure of the anastomotic orifice is 43.86 mmHg. During welding, the temperature of the normal saline at the outlet is 6.8 °C higher than that at the inlet, indicating that the use of circulating normal saline as the conductive and cooling medium can dissipate part of the heat generated by welding and reduce heat accumulation, thereby reducing thermal damage of biological tissue near the welding area. Overall, the proposed electrode may contribute to the recovery of postoperative intestinal function by enabling a novel strategy for clinical intestinal anastomosis induced by radio frequency energy.