High Frequency System Research Articles

Deep Brain Stimulation beyond the Clinic: Navigating the Future of Parkinson's and Alzheimer's Disease Therapy.

Deep brain stimulation (DBS) is a surgical procedure that uses electrical neuromodulation to target specific regions of the brain, showing potential in the treatment of neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD). Despite similarities in disease pathology, DBS is currently only approved for use in PD patients, with limited literature on its effectiveness in AD. While DBS has shown promise in ameliorating brain circuits in PD, further research is needed to determine the optimal parameters for DBS and address any potential side effects. This review emphasizes the need for foundational and clinical research on DBS in different brain regions to treat AD and recommends the development of a classification system for adverse effects. Furthermore, this review suggests the use of either a low-frequency system (LFS) or high-frequency system (HFS) depending on the specific symptoms of the patient for both PD and AD.

Research of the frequency response parameters of antenna module circuit of the high frequency heating system of KTM tokamak plasma

The article presents the results of measuring the parameters of the amplitude-frequency characteristics (AFC) of the antenna module circuit of the system for additional high frequency (HF) heating of the KTM tokamak plasma in laboratory conditions. A description of the antenna-feeder device and the HF system of the KTM tokamak is presented. At this stage of time, commissioning works for launching of the HF system of additional heating are performed at the KTM tokamak. The design and launch of such system requires conducting of separate research. Since the HF system consists of four modules, which includes various subsystems and components, before testing the entire HF system as an assembly, it is necessary to check and determine the parameters of individual components of the HF system. The antenna module is a part of the antenna-feeder device and is a very important component in the HF system, because it transfers energy from the generator to the tokamak plasma, thus heating the plasma. In case if the transmitting system does not match the declared operating frequency, HF system will be mismatched, which will affect the efficiency of plasma heating and operation of the entire HF system. It is impossible to bring the KTM tokamak to the nominal declared power without putting into operation of the system for additional HF heating of the plasma. Additional components are attached to the antenna module, the influence of which must also be studied for the correct operation of the entire HF system in the future. This paper presents a method for measuring the frequency response of the antenna module and the results of determining the operating parameters of the antenna module such as: wave impedance, inductance, capacitance, resonant frequency and quality factor of the antenna module circuit, depending on various additional inductance adjustment elements.

Double-mode and double-beam staggered double-vane traveling-wave tube with high-power and broadband at terahertz band

In this paper, a 220 GHz broadband and high-power staggered double-vane traveling-wave tube has been designed and verified. Firstly, a planar double-beam staggered double-vane slow-wave structure is proposed. By using the double-mode operation scheme, the transmission performance and bandwidth have been almost increased with twice as the single mode. Second, to satisfy the high output power requirement and improve the stability of the traveling-wave tube, a double pencil-beam electron optical system has been designed, the 20–21 kV driven voltage and the 2 × 80 mA current are set as the design target. By using the mask portion and the control electrode in the double beam gun, the two pencil beams can be focused with a compression ratio of 7 along their respective centers with narrow distances of about 0.18 mm with good stability. The uniform magnetic focusing system has also been optimized. The stable transmission distance of planar double electron beams could reach 45 mm with the focusing magnetic field of 0.6 T, which was long enough to cover the whole high-frequency system (HFS). Then, to verify the availability of the electron optical system and the performance of the slow-wave structure, particle-in-cell (PIC) simulation has also been carried out with the whole HFS. Results demonstrate that the beam-wave interaction system can get a nearly 310 W peak output power at 220 GHz with a 20.6 kV optimized beam voltage and beam current of 2 × 80 mA, the gain is of 38 dB with the 3-dB bandwidth over 35 dB about 70 GHz. Finally, the high precision microstructures fabrication has been carried out to verify the performance of the HFS, the results show that the bandwidth and the transmission properties are in good agreement with simulation result. Thus, the proposed scheme in this paper is expected to develop the high-power and ultra-wideband terahertz band radiation source with potential applications in the future.

Comparison of Measured Surface Currents from High Frequency (HF) and X-Band Radar in a Marine Protected Coastal Area of the Ligurian Sea: Toward an Integrated Monitoring System

Two different ground-based remote sensing instruments can be used for the near-real-time monitoring of surface waves and currents, namely the high frequency HF radar and the microwave X-band radar. The HF system reaches larger offshore distances at lower spatial resolutions and provides a poorer measurement of the wave-induced currents in very shallow waters. On the other hand, the X-band system achieves significantly higher spatial resolutions with a smaller offshore coverage. This study provides a preliminary comparison of the measured surface currents, obtained by the two different tools where they overlap. The comparison showed a good agreement between the measures with some discrepancies ascribable to the difference in the characteristics of the two radar technologies.

Passive radio sounding to correct for Europa’s ionospheric distortion of VHF signals

The dispersive effect of Europa’s ionosphere on radio wave propagation is detrimental to the quality of radar observations for altimetry and geodesy of Europa’s surface, as it creates pulse broadening and signal delay. While using the relative delay between two active radar channels of different center frequencies is a common method to correct for this ionospheric distortion, the High Frequency (HF) active band for a dual-frequency radar sounder like the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) is susceptible to being dominated by the bursts of Jupiter’s radio emissions when the radar is on the sub-Jovian side. At these times, the HF radar will be severely degraded or unusable alongside the slightly dispersed Very High Frequency (VHF) channel for performing radar sounding as well as reference-based radar corrections of ionospheric distortion for VHF altimetry. To address this, we assess the potential to use Jupiter’s radio emissions to correct for ionospheric distortion with a passive radio sounding approach that has been developed on Earth to estimate the thickness of ice sheets using the Sun. With REASON as an interesting test case for the technique, we discuss in general the abilities and requirements for a dual-frequency radar system using a passive HF radar alongside an active VHF radar to correct for ionospheric distortion, and we compare the passive mode’s performance to that of an active HF radar system. Finally, we show that even in the presence of the maximum expected total electron content (TEC) in Europa’s ionosphere, the passive radar approach, using the REASON HF as a receive-only instrument, not only corrects for dispersion but also performs at a level similar to that of an active HF system in terms of TEC estimation and VHF range error reduction.

Design, Fabrication, and Cold Test of a High Frequency System for an H-Band Sheet Beam Travelling Wave Tube

The design, fabrication and cold test of a high frequency system (HFS) for an H -band (220–325GHz) sheet beam travelling wave tube is presented in this article. The HFS was composed of a 90-period double-staggered grating waveguide and a pair of identical L-shaped couplers with Bragg reflectors and matching steps. The HFS was manufactured by nano-computer numerical control machining and its electromagnetic properties were measured by using a vector network analyzer. The measured S -parameters were in good agreement with the simulated ones, which predicted a 3 dB bandwidth of ∼47.0 GHz. The maximum value of the measured transmission coefficient S 21 was −4.9 dB and the in-band port reflection S 11 was around −15.0 dB. Based on the cold testing-based HFS, simulations of the beam wave interaction predicted a stable output power of over 55.1 W in the frequency range of 230–280 GHz. In addition, the instabilities of the beam wave interaction were investigated in the simulation.

A Dual-Band HF and UHF Antenna System for Implanted Neural Recording and Stimulation Devices

We present a dual-band high-frequency (HF) and ultrahigh-frequency (UHF) (13.56 and 902-928 MHz) antenna system for implanted neural recording and/or stimulation devices. This system consists of implant-side and external antennas. These antennas are intended for dual-band systems, where power is supplied to the implant via inductive coupling in the HF band, while data are transferred via UHF near-field coupling. The antenna system consists of an implant-side antenna of 25 mm diameter and 3 mm thickness, as well as an external antenna of 85 mm diameter and 3 mm thickness. We present both timeand frequency-domain simulation results for antenna performance and specific absorption rate in a layered tissue model, as well as experimental confirmation of antenna performance in a saline tissue proxy. With an implant depth of 11 mm and an air gap of 5 mm, the power link has a 17% measured power transfer efficiency in the HF band, inclusive of matching component losses, and the UHF communication link has 38-dB insertion loss over the 902-928-MHz band.

Bonding Performance of Adhesives with Lamina in Structural Glulam Manufactured by High Frequency Heating System

The bonding performance of two types of wood adhesives, namely phenol-resorcinol-formaldehyde (PRF) resin and melamine-urea-formaldehyde (MUF) resin for glued laminated timber manufactured by high frequency (HF) heating was evaluated. The HF heating system consists of HF oscillator with dielectric heating system for curing adhesives, and hydraulic press system for clamping glued laminated timber. The designed frequency and output power of the HF system was as 5 MHz and 60 kW, respectively. To verify dielectric heating mechanism under HF oscillation, the heat loss factors of laminae and adhesives were measured. The results show that it is possible to selectively heat adhesives for their curing due to the remarkably higher loss factor of the adhesives than those of wood laminae. The temperature of adhesive in the bonding line reached up to the set temperature within a few seconds by high frequency oscillating, which advanced the curing of adhesive afterwards. The bonding performance, such as shear strength of bonding line, water soaking delamination, and boiling water soaking delamination of PRF resin met the requirement of Korean Standard (KS), however the MUF resin did not meet the KS requirement of boiling water soaking delamination. These results indicate that the HF heating system is successful to manufacture glued laminated timbers with PRF resins to meet the bonding requirements.

The high energy electromagnetic field generator

The original concept described is named the high energy electromagnetic field generator. This concept's governing physics entail the coupling of gyration (high frequency spin), vibration (high frequency abrupt pulsations/harmonic oscillations) and possible curvilinear translation, of electrically charged systems. If we couple the system's high frequency of rotation (30,000 to 100,000 RPM, and higher) with high vibration (abrupt pulsations/harmonic oscillations) frequencies in the range of 109 to 1018 Hertz (and above) we can obtain electromagnetic field intensity values in the range 1024 to 1028 Watts/m2 (and beyond). These extremely high electromagnetic field intensity values emphasise the novelty of this concept, especially suited for the design of energy generation machinery with power output levels much higher than those currently achievable. The utilisation of such high power sources for space power and propulsion generation, as it pertains to reduction in a spacecraft's inertial mass as a direct result of local vacuum polarisation, is an important application of the described theoretical concept. In this manner, extreme spacecraft speeds can be achieved.

Direct detection of SDSS J0926+3624 orbital expansion with ARCONS

AM Canum Venaticorum (AM CVn) stars belong to a class of ultra-compact, short period binaries with spectra dominated largely by helium. SDSS J0926+3624 is of particular interest as it is the first observed eclipsing AM CVn system. We observed SDSS J0926+3624 with the \textbf{Ar}ray \textbf{C}amera for \textbf{O}ptical to \textbf{N}ear-IR \textbf{S}pectrophotometry (ARCONS) at the Palomar 200" telescope. ARCONS uses a relatively new type of energy-resolved photon counters called Microwave Kinetic Inductance Detectors (MKIDs). ARCONS, sensitive to radiation from 350 to 1100 nm, has a time resolution of several microseconds and can measure the energy of a photon to $\sim10%$. We present the light curves for these observations and examine changes in orbital period from prior observations. Using a quadratic ephemeris model, we measure a period rate of change $\dot{P} = (3.07 \pm 0.56)\times 10^{-13}$. In addition, we use the high timing resolution of ARCONS to examine the system's high frequency variations and search for possible quasi-periodic oscillations (QPOs). Finally, we use the instrument's spectral resolution to examine the light curves in various wavelength bands. We do not find any high frequency QPOs or significant spectral variability throughout an eclipse.

A New Simulation Architecture for Communication Network Systems with Application to HF Radio

 Abstract—This paper describes a simulation architecture developed to address the need in the defence and aerospace industry for a rapid prototyping capability to test new and existing network protocols and systems where analytical methods no longer suffice. In particular, the simulator introduced here allows study of High Frequency (HF) radio networks and other unorthodox systems that cannot be easily modelled using existing communications network simulators. This paper describes the architecture and gives an example use case - modelling an HF System using the 2G Automatic Link Establishment (ALE) linking protocol under a variety of conditions; exploring the effects of changing the number of nodes in the network, and of altering the input data rate to the system. The network performance was analysed under a wide range of combinations of conditions, and it was found that increasing the number of nodes in these networks causes specific latency increases and an overall throughput decrease, both in the unidirectional and bidirectional case, although it is better tolerated in the unidirectional case. Increasing the input data rate causes an overall throughput increase up to a threshold point, after which it saturates and then decreases as data remains unsent, due to the physical limits of the system (including networking overhead) being surpassed. This simulator, known as CommNetSim has been developed for use in evaluating the technical capabilities of, and business cases for, real-world applications to be developed by Thales UK. Index Terms—Communication networks, discrete event simulation, high frequency radio, modelling, simulation.

SWITCHABLE DISTANCE-BASED IMPEDANCE MATCHING NETWORKS FOR A TUNABLE HF SYSTEM

Distance-based impedance matching networks for a tunable high frequency (HF) system are presented in this paper for the improved performance. The transmitting antenna for a HF system with an operating frequency of 13.56MHz consists of a two-turn loop and three channel impedance matching networks corresponding to the distance of the receiving antenna. Each impedance matching network maximizes the system performance such as uniform power e-ciency and reading range at speciflc distance between a transmitting and a receiving antenna. By controlling the distance-based matching networks, the power e-ciency of the proposed antenna improves by up to 89% compared to the conventional antenna system with the flxed matching (FM) condition for distances, and the reliable reading range according to the impedance matching conditions is also increased. The proposed technique is applicable for near fleld communication (NFC), radio frequency identiflcation (RFID), or wireless power transfer (WPT) devices.

Design and implementation of a wideband HF channel simulator

The paper presents a wideband high frequency (HF) channel simulator. The simulation consists of a software simulation of a direct-sequence spread-spectrum (DSSS) HF system with RAKE receiver. The validity of the HF channel simulator is demonstrated by the analysis of the scattering function and example results of the simulator. The performance of DS system under HF channel and noise are also presented. The simulation results and theoretical analysis show that a straightforward DS system may properly mitigate the intersymbol interference (ISI) distortion of the HF channel while perform badly under the HF noise and interference.