High Frequency Radio Research Articles

A 100 kpc ram pressure tail trailing the group galaxy NGC 2276

We present the discovery of a $100\ kpc $ low-frequency radio tail behind the nearby group galaxy, NGC 2276. The extent of this tail is a factor of ten larger than previously reported from higher-frequency radio and X-ray imaging. The radio morphology of the galaxy disc and tail suggest that the tail was produced via ram-pressure stripping, cementing NGC 2276 as the clearest known example of ram-pressure stripping in a low-mass group. With multi-frequency imaging, we extract radio continuum spectra between $ sim MHz $ and $1.2\ GHz $ as a function of projected distance along the tail. All of the spectra are well fit by a simple model of spectral ageing due to synchrotron and inverse-Compton losses. From these fits we estimate a velocity of $870\ $ for the stripped plasma across the plane of the sky, and a three-dimensional orbital velocity of $970\ $ for NGC 2276. The orbital speed that we derive is in excellent agreement with the previous estimates from an X-ray shock analysis, despite the completely independent methodology.

High‐Latitude Off‐Great Circle Propagation Associated With the Solar Terminator

AbstractLarge‐scale ionospheric gradients associated with the solar terminator can deflect high frequency (HF) radio waves to off‐great circle paths during the morning and evening, negatively impacting technologies reliant on HF radio wave propagation. For example, geolocation algorithms used by scientific and military over‐the‐horizon radars (OTHRs) generally assume on‐great circle propagation, and thus lateral deviations from the great‐circle path can lead to positioning errors. In this study, radio wave propagation is simulated via 3D numerical ray traces though an empirical, high‐latitude model ionosphere initialized for a variety of times of the day and year to explore and quantify high‐latitude off‐great circle propagation associated with the solar terminator. Analysis of these simulations show large scale east‐west ionospheric gradients due to the solar terminator can cause lateral deviations in north‐directed propagation paths exceeding 20° at sunrise and sunset depending on radio wave frequency, though the largest portion of received signal power tends to experience maximum deflections of 5°. An exploration of the dependence of propagation direction on deflection shows that propagation paths parallel to the solar terminator tend to experience the largest deflections. Since the solar terminator at high latitudes is at an angle with respect to north in the winter and summer, propagation paths oriented west or east of north can experience larger deflections than north oriented paths at sunrise and sunset during these times of year. Impacts of these diurnal deflections on the operation of OTHR and scientific radar are discussed, as well as possible strategies for mitigating them.

Statistical Analysis of Off‐Great Circle Radio Wave Propagation in the Polar Cap

AbstractHigh latitude ionospheric density structures such as polar cap patches and arcs are capable of deflecting high frequency (HF) radio waves to off‐great circle paths, and are likely detrimental to technologies dependent on HF radio propagation. In this study, nearly 2.5 years of 4.6–14.4 MHz data from a multi‐frequency HF radio link between Qaanaaq, Greenland and Alert, Canada are used to investigate high‐latitude off‐great circle propagation in the polar cap. After an example of HF radio propagation affected by polar cap patches is shown in detail, a statistical analysis of the occurrence and impacts of off‐great circle deflections in the polar cap is presented. Off‐great circle propagation is shown to be increasingly common with increasing frequency up to 11.1 MHz, such that averaged over 1 year, received 11.1 MHz signals experienced deflections >30° from the great circle direction 65.6% of the time. The occurrence of these deflections across the year is shown to be at a maximum in the winter, while occurrence across the day varies with season. Trends across both time of day and time of year for 11.1 and 14.4 MHz deflections are consistent with polar cap patch occurrence trends. Off‐great circle deflections are shown to be associated with increased time‐of‐flights, a larger range of positive and negative Doppler shifts, increased Doppler spreads, and lower signal‐to‐noise ratios. These results are discussed in the context of ionospheric phenomena in the polar cap, and implications for over‐the‐horizon radars operating at high latitudes.

The Ellipticity of High Frequency Transionospheric Radio Waves

AbstractThe polarization state of transionospheric high frequency (HF) radio waves can be determined using the crossed‐dipole antennas of the Radio Receiver Instrument (RRI) onboard Enhanced Polar Outflow Probe (e‐POP) on the CAScade, Smallsat, and IOnospheric Polar Explorer/Swarm‐E satellite. Coordinated experiments between ground radars and RRI showed that the radio waves have high ellipticity angles (elliptical or circular polarization) for propagation direction 6°–25° from the perpendicular direction to the local geomagnetic field. However, from magnetoionic theory and a typical assumption of roughly equal power in the O‐ and X‐modes, radio waves can have high ellipticity angles only when the propagation direction is within 10° of perpendicularity. This investigation uses coordinated experiments between the Saskatoon SuperDARN radar and RRI. Magnetoionic modeling reveals that the relative strengths of the O‐ and X‐modes for the HF radio waves transmitted from the Saskatoon SuperDARN change significantly poleward of the radar. Differences in the relative power between the two wave modes were found to significantly modify the polarization state of radio waves, and govern the sense of rotation of the wave. Even a relatively modest 2–5 dB power difference in the X‐mode over the O‐mode was found to result in unexpected observations of circularly polarized radio waves at aspect angles 6°–10° from perpendicular, and unexpected elliptically polarized waves observed at aspect angles more than 10° from perpendicular. Therefore, a combination of RRI observations and modeling, which accounts for relative differences in the O‐ and X‐mode powers, was used here to better understand the unexpected observations of polarization states of transionospheric radio waves.

Survey of IP-based air-to-ground data link communication technologies

The main purpose of an air traffic management system is to provide air traffic services to an aircraft moving within the controlled airspace. Very high frequency (VHF) radio in continental regions, as well as high frequency (HF) radio and satellite communications in remote areas, are used today as the primary way of delivering air traffic services. The technical limitations and constraints associated with the current technology, such as line-of-sight requirement, vulnerability to interference, and limited coverage, cause degraded voice quality and discontinuity in service. At the same time, voice-based communication may affect flight safety due to poor language skills, call sign confusion, and failure to use standard phraseology. For this reason, text-based communication over a VHF data link (VDL) has been proposed as an alternative. However, it is predicted that VDL will be insufficient to support increasing air traffic and intensive data exchanges due to its lack of mobility support and limited resources to ensure service continuity. This paper surveys next-generation data link technologies based on the current state of the "industry standard" for aeronautical communication. These include Aeronautical Mobile Airport Communication System (AeroMACS), L-band Digital Aeronautical Communications System (LDACS), and Airborne New Advanced Satellite Techniques & Technologies in a System Integrated Approach (ANASTASIA). The paper also surveys IP-based text communication solutions over these next-generation data links. We analyze the efficiency of the proposed solutions with regard to service continuity and aeronautical application requirements. We conclude the survey by identifying open problems and future trends.

OVERVIEW FOR THE IMPLEMENTATION OF FLIGHT WATCH IN FLIGHT TRAFFIC SERVICES WITH FLIGHT OPERATORS

On the Job Training activities are one of the activities that must be carried out by cadets. One of those who received this On the Job Training (OJT) activity was the Tarakan Branch of LPPNI, which is one of the airports that serves various types of flights, including pioneer, domestic, international and local flights. The data taken by the author is real data that the author obtained when carrying out OJT activities from September to August 2022. There were several obstacles that the author encountered when carrying out On the Job Training activities. One of them is inadequate communication from several aircraft because they do not carry High Frequency (HF) radio equipment. So that the aircraft that should be able to communicate with Balikpapan Info on the HF radio channel cannot communicate. And there is no sending of departure messages and arrival messages to the Tarakan APP which can cause disruption to the separation that is being implemented, because planes coming from the pilot area will suddenly appear on the controller's radar. By implementing the Flight Watch procedure, it is hoped that this incident can be minimized, as well as reviewing aircraft that do not carry equipment as stated in the Flight Plan as appropriate.

Forward Modeling for the Fine Detection of Geological Abnormal Area in Coal Seams Using High-frequency Radio Imaging Method

Forward Modeling for the Fine Detection of Geological Abnormal Area in Coal Seams Using High-frequency Radio Imaging Method

Unsupervised Machine Learning-Based Clustering of High-Frequency Radio Channel Properties: Analysis of Sector Communication Efficiency

Machine learning has emerged as a powerful tool for both engineering and geo-localization applications. In this study, we investigate the Terabit/sec bandwidth wireless technology application using specialized ns-3 simulation tools. Through extensive simulations, we explore various scenarios with diverse parameters, including population density, topology types, and overlapping ratios among consecutive radio sectors centered around a single access point. To extract meaningful insights from the data, we employ the DBScan unsupervised learning method, enabling us to identify the optimal number of classes for sector efficiency features. Our optimization approach considers both the number of outliers and the minimum number of elements within each radio sector. By analysing a synthetic dataset generated from the simulation cases, we uncover valuable insights and establish the optimal working point for the system.

Design of a Spiral Coil for High-Frequency Wireless Power Transfer Systems Using Machine Learning

Design of a Spiral Coil for High-Frequency Wireless Power Transfer Systems Using Machine Learning

Cryptanalysis of HALFLOOP Block Ciphers

HALFLOOP is a family of tweakable block ciphers that are used for encrypting automatic link establishment (ALE) messages in high frequency radio, a technology commonly used by the military, other government agencies and industries which require high robustness in long-distance communications. Recently, it was shown in [DDLS22] that the smallest version of the cipher, HALFLOOP-24, can be attacked within a practical time and memory complexity. However, in the real-word ALE setting, it turns out that this attack require to wait more than 500 years to collect the necessary amount of plaintext-tweak-ciphertext pairs fulfilling the conditions of the attack.In this paper, we present real-world practical attacks against HALFLOOP-24 which are based on a probability-one differential distinguisher. In our attacks, we significantly reduce the data complexity to three differential pairs in the chosen-plaintext (CPA) setting which is optimal in the sense that even a brute force attack needs at least six plaintext-tweak-ciphertext pairs to uniquely identify the correct key. Considering the same ALE setting as [DDLS22], this translates to a reduction from 541 years to 2 hours worth of intercepted traffic.Besides, we provide the first, non generic, public cryptanalysis of HALFLOOP-48 and HALFLOOP-96. More precisely, we present Demirci-Selçuk meet-in-the-middle attacks against full-round HALFLOOP-48 and round-reduced HALFLOOP-96 to recover the complete master key in a CPA setting. However, unlike the attacks on HALFLOOP-24, our attacks on the larger versions are only theoretical. Moreover for HALFLOOP-96 the known generic time-memory trade-off attack, based on a flawed tweak handling, remains the strongest attack vector.In conclusion, we iterate what was already stated in [DDLS22]: HALFLOOP does not provide adequate protection and should not be used.

A Bidirectional Autonomous High-Frequency Wireless Power Transfer System With Constant Voltage Output Against Load and Coupling Variations

A Bidirectional Autonomous High-Frequency Wireless Power Transfer System With Constant Voltage Output Against Load and Coupling Variations

Analysis and Design of a High Frequency Wireless Battery Charging System With Smooth Mode Transition Characteristics

Analysis and Design of a High Frequency Wireless Battery Charging System With Smooth Mode Transition Characteristics

An Updating of the IONORT Tool to Perform a High-Frequency Ionospheric Ray Tracing

This paper describes the main updates characterizing the new version of IONORT (IONOsperic Ray Tracing), a software tool developed at Istituto Nazionale di Geofisica e Vulcanologia to determine both the path of a high frequency (HF) radio wave propagating in the ionospheric medium, and the group time delay of the wave itself along the path. One of the main changes concerns the replacement of a regional three-dimensional electron density matrix, which was previously taken as input to represent the ionosphere, with a global one. Therefore, it is now possible to carry out different ray tracings from whatever point of the Earth’s surface, simply by selecting suitable loop cycles thanks to the new ray tracing graphical user interface (GUI). At the same time, thanks to a homing GUI, it is also possible to generate synthetic oblique ionograms for whatever radio link chosen by the user. Both ray tracing and homing GUIs will be described in detail providing at the same time some practical examples of their use for different regions. IONORT software finds practical application in the planning of HF radio links, exploiting the sky wave, through an accurate and thorough knowledge of the ionospheric medium. HF radio waves users, including broadcasting and civil aviation, would benefit from the use of the IONORT software (version 2023.10).

The Nature of the IMBH Candidate CXO J133815.6+043255: High-frequency Radio Emission

The ultraluminous X-ray source CXO J133815.6+043255 is a strong candidate for a bona fide intermediate-mass black hole residing in the outskirts of NGC 5252. We present 22 GHz radio observations of this source obtained serendipitously in an ongoing high-frequency imaging survey of radio-quiet Active Galactic Nuclei (AGNs), and use this new data point to construct the broadband radio spectral energy distribution (SED). We find that the SED exhibits a spectral slope of α = −0.66 ± 0.02, consistent with a steep spectrum from optically thin synchrotron emission from an unresolved jet. We also find that the L R/L X ratio is approximately 10−3, inconsistent with radio-quiet AGN and many ULXs but consistent with low-luminosity AGN and radio-loud quasars. Together, these observations support the conclusion that CXO J133815.6+043255 is an intermediate-mass black hole producing a low-mass analog of radio jets seen in classical quasars.

Channel characterization and modeling for wireless communication link planning and design in the tropics

<p>Channel model provides basis in the link budgetary for planning and design of low margin systems of communication links. This paper proposed a simple and efficient channel model for wireless channel path loss characterization and modeling. Free space channel was characterized and modelled to account for both static and dynamic changes of signal that propagates through it. Correction factors in the model account for the losses due to refraction effects, as a result of abnormal refractivity condition frequent in tropical regions. The model was validated via measurement data from experiment conducted in a tropical region and a high level of agreement was observed. The proposed model can be deployed during link planning and budgetary for ultra high frequency (UHF) wireless radio services.</p>

An ultrawideband Koch fractal patch antenna

PurposeCompact and wideband antennas are the need of modern wireless systems that preferably work with compact, low-profile and easy-to-install devices that provide a wider coverage of operating frequencies. The purpose of this paper is to propose a novel compact and ultrawideband (UWB) microstrip patch antenna intended for high frequency wireless applications.Design/methodology/approachA square microstrip patch antenna was initially modeled on finite element method-based electromagnetic simulation tool high frequency structure simulator. It was then loaded with a rectangular slit and Koch snowflake-shaped fractal notches for bandwidth enhancement. The fabricated prototype was tested by using vector network analyzer from Agilent Technologies, N5247A, Santa Clara, California, United States (US).FindingsThe designed Koch fractal patch antenna is highly compact with dimensions of 10 × 10 mm only and possesses UWB characteristics with multiple resonances in the operating band. The −10 dB measured impedance bandwidth was observed to be approximately 13.65 GHz in the frequency range (23.20–36.85 GHz).Originality/valueOwing to its simple and compact structure, positive and substantial gain values, high radiation efficiency and stable radiation patterns throughout the frequency band of interest, the proposed antenna is a suitable candidate for high frequency wireless applications in the K (18–27 GHz) and Ka (26.5–40 GHz) microwave bands.

On the Use of Wireless Technologies for Wildlife Monitoring: Wireless Sensor Network Routing Protocols

Traditional methods for wildlife monitoring are labor-intensive and time-consuming. Therefore, advanced technologies and remote monitoring methods are becoming increasingly popular. This paper presents a study on wireless technologies for wildlife monitoring. In the study, a review of the literature was done to identify the most commonly used wireless technologies. Various technologies were explored including unmanned aerial vehicles (UAVs), Internet of Things (IoT), wireless sensor networks (WSNs), artificial intelligence (AI), global positioning system (GPS), and very high frequency (VHF) radio. Then, a more detailed study was done on WSN technology. Investigations were done to observe the performance of routing protocols in WSNs. The use of source location privacy (SLP) routing protocols was considered for secure wildlife monitoring in areas such as game reserves. In such areas, sensor node energy consumption minimization and battery lifetime maximization are crucial. Hence, energy-efficient SLP protocols are more suitable for deployment. Using MATLAB simulation environment, performance analysis of various phantom- based SLP protocols was done to identify effective and energy-efficient SLP protocols. Simulation results show that two-level phantom with a backbone route protocol (TBP) and phantom with angle protocol (PAP) exhibit advantageous performance features in terms of SLP protection, energy efficiency, effective long-term SLP protection, and scalability. Thus, TBP and PAP are suitable for deployment in wildlife monitoring WSNs.

Diffraction Theory of Propagation of High-Frequency Radio Waves in a Spherically Layered Ionospheric Radio Channel

Diffraction Theory of Propagation of High-Frequency Radio Waves in a Spherically Layered Ionospheric Radio Channel

Shielding Design for High-Frequency Wireless Power Transfer System for EV Charging With Self-Resonant Coils

This paper provides a complete coil and shielding design solution for a 6.6 kW electric vehicle wireless power transfer system based on compact self-resonant (SR) coils. Due to the presence of a conductive vehicle body above the receiver coil, vertical fringing flux must be shielded in any electric vehicle wireless charger. Using high-frequency SR coils, parasitic capacitance introduced by standard shielding design approaches degrades the quality factor of the coils. In this work, the high-frequency parasitic capacitance introduced by the magnetic and conductive shielding materials is analyzed in detail, and a shielding geometry optimization method is proposed. Using ferrite and an additional dielectric spacer, prototype aluminum-backed SR coils are fabricated to validate the modeling. The total thicknesses of the transmitter and receiver coils are only 11.4 mm and 7.4 mm, respectively. The prototype coils achieve 92.3% DC-DC efficiency and 7.1 kW/dm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> volumetric power density. This paper demonstrates the first 6.6 kW WPT system for EV charging using compact megahertz-self-resonant coils including a complete magnetic and conductive shielding implementation.

Handover Experiment of 60-GHz-Band Wireless LAN in over 200-km/h High-Speed Mobility Environment

High-frequency wireless communication is drawing attention because of its potential to actualize huge transmission capacity in the next generation wireless system. The use of high-frequency bands requires dense deployment of access points to compensate for significant distance attenuation and diffraction loss. Dense deployment of access points in a mobility environment triggers an increase in the frequency of handover because the number of candidate access points increases. Therefore, simple handover schemes are needed. High-frequency wireless systems enable station position to be determined using their wideband and highly directional communication signals. Thus, simple handover based on position information estimated using the communication signal is possible. Interruptions caused by handover are also a huge barrier to actualizing stable high-frequency wireless communications. This paper proposes a seamless handover scheme using multiple radio units. This paper evaluates the combination of simple handover and the proposed scheme based on experiments using a formula racing car representing the fastest high-speed mobility environment. Experimental results show that seamless handover and high-speed wireless transmission over 200Mbps are achieved over a 400-m area even at station velocities of greater than 200km/h.