The results of theoretical studies and mathematical modeling indicate the possibility of obtaining the angular superresolution and its limits by using algebraic methods of imaging. The necessary algorithms are created on the basis of solution to inverse problems. The limiting levels of the achieved angular superresolution are found depending on the signal‐to‐noise ratio (SNR) for objects of various

Global Navigation Satellite System (GNSS) signals have become a useful tool to analyse signal‐in‐space performance in the presence of ionospheric perturbations with a view to improving the performance of satellite‐based systems and services. For this purpose, continuous monitoring of the signal tracking capabilities of commercial GNSS receivers is a priority, particularly from regions around the crests

A new discovery was made using the Radio Receiver Instrument (RRI) on the Canadian Enhanced Polar Outflow Probe (e‐POP) showing that Strong Plasma Wave Emissions (SPWE) are seen near 17 kHz and 300 Hz. The frequency of these emissions are affected by small injections of neutral gas from the Cygnus spacecraft. The technique of using a 150 g/s thruster to change frequencies and intensities of plasma

We modified and justified the radar equation for ground penetration by including the backscattering effect. We propose a strawman system on an orbiter 50 km above the surface based on lunar conditions. The Tightly‐coupled dipole arrays antenna substantially reduces the size and mass and consists of an array with 8x8 cells on a light weight plate that is 1.62m2 wide with cells 0.25m high providing increased

High‐speed data transfer and high‐performance imaging can be realized by using radio‐waves in high‐frequency bands, such as millimeter‐waves and THz‐waves, where wide frequency bands are available. However, the cell size would be smaller than a few hundred meters, due to large free space propagation loss and large atmospheric attenuation. Thus, many base stations, which are connected by networks, are

This paper introduces a new approach of estimating the daytime horizontal geomagnetic field (∆H) induced variations of vertical E × B drift velocity and evaluates its performance using Communication/Navigation Outage Forecasting Systems (C/NOFS) over the East African sector. H‐field at AAE (Addis Ababa magnetometer station) and ETHI (Adigrat magnetometer station in Ethiopia) and their immediate difference

No abstract is available for this article.

When electromagnetic waves impinge on objects with complex geometries and/or internal structure, we can observe scattering that is distributed in time rather than instantaneous. To detect and characterize such targets, we build the coordinate‐delay synthetic aperture radar (cdSAR) images by adding a delay term to the standard SAR matched filter. In order to apply this approach to the case of extended

We present passive observations of midlatitude sporadic E (Es) structures in the 30 to 50 MHz range using the Long Wavelength Array (LWA) telescopes in New Mexico. Spectral and temporal analysis of the structures reveals that some of the emissions can be characterized by broadband, spark‐like radiation occurring at a repetition frequency of 60 Hz. The azimuthal distribution indicates that the brightest

This paper presents a new ultra‐wideband (UWB) antenna system with circular polarization (CP). The antenna is a coplanar waveguide (CPW) feed structure with a modified inverted L‐shaped radiating patch. A single‐layer non‐uniform frequency selective surface (FSS) composed of rectangular conductive patches is designed and used with the CP antenna to improve the CP characteristics and the gain of the

No abstract is available for this article.

Extending the frequency range of the Walfisch‐Bertoni (W‐B) model, which is a representative theory‐based model, was investigated. To extend the W‐B model, three changes to the original W‐B model were made: (i) re‐modeling over rooftop path, (ii) introducing a slant path, and (iii) modeling of multiple reflections between buildings. To validate the proposed model, propagation loss predicted by the

The tropospheric propagation effect is one of several sources of error in radio science measurements. Systematically calibrated for the Earth troposphere disturbances, the ranging and Doppler data provided by the Martian landers have not been corrected so far for Mars troposphere effects. These effects were considered negligible because the Mars atmosphere is a hundred times less dense than that of

The ionosphere in low‐latitude regions has strong dynamics reflected by unique phenomena such as the equatorial ionization anomaly and equatorial plasma bubbles. Since the ionosphere can significantly affect space‐to‐Earth technologies, notably communication systems and Global Navigation Satellite Systems (GNSS), the variations in ionospheric total electron content are of great interest to the space

The present contribution applies a modified version of a well‐known weak‐scatter scintillation model to the propagation paths between an Earth station and two geostationary satellites, as they are affected by drifting ionospheric irregularities detected by the planar Langmuir probe onboard the Communications/Navigation Outage Forecasting System (C/NOFS) satellite. This study considers one year of data

We aim to select the range of frequencies where the medium parameters have less effects on the scattered waves, and as a result we achieve high precision of computed radar cross section (RCS). Ideal object detection can be obtained through calculation of RCS assuming a plane wave incidence in the far field. Numerical results are conducted to investigate effects of medium characteristics and target

Ionospheric correlation time is an important parameter that contains information about the temporal variability, structures, and dynamics of the ionosphere. This parameter is also important in forecasting of the ionospheric state. Ionospheric data assimilation algorithms employing empirical background models, such as Ionospheric Data Assimilation Four‐Dimensional (IDA4D), apply Gauss‐Markov approximation

A significant anomaly in the extremely low frequency (ELF) spectra of Schumann resonance (SR) was discovered for the 1999 Chi‐Chi earthquake (EQ) in Taiwan as observed in Japan. Similar phenomena were confirmed for other EQs remote from the observer by a few megameters. An additional effect was detected for nearby EQs. The anomalies were explained by ELF radio wave scattering from a seismogenic disturbance

Using a argument approach and a combination of historical, contemporary datasets, we show that the evidence for deep geotemperature rise and abyssal ocean warming due to “human‐induced” changes to the Earth's insulation system. This warming deepened the soil and sea change and triggered large mass losses from glaciers, resulting in a n times increase in delivery of glacial melt‐waters, sediment, organic

Maxwell's equations are transformed from a Cartesian geometry to a Riemannian geometry. A geodetic path in the Riemannian geometry is defined as the raypath on which the electromagnetic energy efficiently travels through the medium. Consistent with the spatial behavior of the Poynting vector, the metric tensor is required to be functionally dependent on the refractive index of the medium. A symmetric

The background covariance matrix establishes the transition from the data‐ to model‐driven regions in the ionospheric data assimilation algorithms. To construct the background covariance matrix, the information about the spatial ionospheric correlations of model errors is required. This paper focuses on the horizontal component of the covariance matrix. It is the first study that presents global maps

The Embrace Magnetometer Network (Embrace MagNet) uses a series of magnetometers over South America to monitor the Earth's space environment and to study space weather. One of the common techniques used to study the effects of the magnetic disturbances in the globe is through the quiet day curve (QDC) of the geomagnetic field components. These types of QDC are calculated based on geomagnetic field

No abstract is available for this article.

We demonstrate scintillation analysis from a network of geodetic Global Positioning System (GPS) receivers which provide data at 1‐second resolution. We introduce proxy phase (σTEC) and amplitude (SNR4) scintillation indices and validate them against the rate of change of TEC index (ROTI) and S4. Additionally, we validate scintillation observations against a Connected Autonomous Space Environment Sensor

Detection of precursors of strong earthquakes is a challenging research area. Recently, it has been shown that strong earthquakes affect electron distribution in the regional ionosphere with indirectly observable changes in the ionospheric delays of GPS signals. Especially, the total electron content (TEC) estimated from GPS data can be used in the seismic precursor detection for strong earthquakes

The study investigates the relationship between Super Dual Auroral Radar Network (SuperDARN) high‐frequency (HF) radar velocities measured at intermediate ranges of 600–1,000 km from the radar and the E × B plasma drift. Two approaches are implemented. First, a 3‐h interval of SuperDARN Rankin Inlet (RKN) radar measurements and Resolute Bay incoherent scatter radar RISR‐C measurements in nearly coinciding

The analysis of the performance of 5G wireless communication systems employing Massive MIMO at millimeter‐wave frequencies is of great practical relevance. Of special relevance are the signal fluctuations. In the present paper, we introduce a semi‐analytical model for a generic scattering environment by using randomly distributed resonant scatterers to investigate the impact of the size of the scattering

This paper applies the collocation method to the modeling and simulation of scattering from a strip with the Dirichlet boundary condition on the upper interface and the Dirichlet and Neumann boundary conditions on the two subintervals along the lower interface. Green's theorem is used to reduce the mixed boundary value problem to the system of three coupled hypersingular and singular integral equations

Echoes from meteor trails can be analyzed to derive diffusion coefficient and thereafter estimates of neutral temperatures, typically around 90 km altitude. The method entails some assumptions and, usually, use of model pressures. Even so, variations in derived temperatures have been assumed to be representative and indicators of other mesospheric processes. However, we now find that the observed variations

While several mm‐wave and sub‐THz frequency bands are being proposed for next generation wireless systems to meet the increasing traffic demand, the electromagnetic properties of many common use materials at those frequencies still need to be determined. The evaluation of such properties is important for the design and deployment of future wireless networks. Recently, a simple method based on Fabry‐Pérot

Spatiotemporal variability of ionosphere poses a major challenge in characterization of observable parameters, critical frequency of F2 layer (foF2), maximum ionization height (hmF2), total electron content (TEC), and slab thickness. The nature of the multiscale space‐time variability of ionosphere can be modeled as a random field. In this study, as a first step in random field modeling of the trend

Streams of the particle ejected from the Sun and the extreme space weather conditions like storms, high‐speed streamers (HSSs), interplanetary coronal mass ejections (ICMEs), corotating interaction regions (CIRs), and interplanetary shocks (IS) termed as geomagnetic storms have massive influence in the climate and components of the Earth's upper atmosphere such as total electron content (TEC). The

The construction of the background covariance matrix is an important component of ionospheric data assimilation algorithms, such as Ionospheric Data Assimilation Four‐Dimensional (IDA4D). It is a matrix that describes the correlations between all the grid points in the model domain and determines the transition from the data‐driven to model‐driven regions. The vertical component of this matrix also

In recent years, high‐speed railway and subway are being built rapidly in China. Tunnel scenario is a major scenario in some of the high‐speed railways and most of the subways. Channel characteristic is the decisive condition of wireless communication system design in tunnel. The availability of multiple‐input multiple‐output (MIMO) in tunnel is an important issue in the next generation communication

In this paper a novelty Massive Multiple Input Multiple Output (MIMO) channel model based on the birth‐and‐death process of multipath clusters is proposed. First, Massive MIMO measurements are conducted in typical outdoSor scenarios with the bandwidth of 100 MHz at frequencies of 1.4725 and 6 GHz, respectively, following with the investigation of radio propagation characteristics over antenna array

Ultrahigh frequency wireless signals are mainly influenced by the geomorphological environment during the transmission process, resulting in fading channels, especially in mountainous regions. The experiment was conducted in the Karst landform of Guizhou Province, China, in order to explore fading distribution characteristics for mainly analyzing electro magnetic compatibility (EMC) specialties between

The information of atmospheric attenuation at Ka‐band is important during rain and clear air condition. In this paper, Ka‐band attenuation data obtained from radiometric measurements at Kolkata, India (22°034′E, 88°022′N) have been presented. The role of water vapor is examined in determining the behavior of atmospheric attenuation during and without rain condition at 22.24, 26.24, and 31.4 GHz frequencies

We consider propagation of surface Transverse Electric (TE) waves in a rod filled with nonlinear metamaterial medium. The problem is reduced to the analysis of a nonlinear integral equation with a kernel in the form of the Green function of an auxiliary boundary value problem on an interval. The existence of propagating nonlinear surface TE waves for the chosen nonlinearity (Kerr law) is proved using

No abstract is available for this article.

Nearly 200 hours of observing with the Murchison Widefield Array (MWA) radio telescope during the Galactic and Extra‐galactic All‐sky MWA (GLEAM) survey were used to assemble images of ionospheric structure. These images cover a nearly 50°‐wide area on the sky at a cadence of 10 minutes over many 5‐7 hours‐long observing runs. They are generated by tracking the apparent motions of ~200‐‐800 cosmic

Millimeter wave (mmWave) based massive multiple‐input multiple‐output (MIMO) beamforming technology is one of the key technologies in the fifth generation (5G) network. In this paper, we apply mmWave to high‐speed railway (HSR) communication scenario to meet its increasingly growing demands for tremendous data rate and reliable mobile services. The HSR mmWave communication system uses a control/user

This paper presents the equatorial ionospheric response to 11 strong‐to‐severe geomagnetic storms that occurred during the period 2000–2005, the declining phase of the Solar Cycle 23. The analysis has been performed using the global ion density plots of the Defense Meteorological Satellite Program (DMSP). Observations show that for about 91% of the cases, postsunset equatorial irregularities occurred

The zero‐order integral equation method (IEM) and the second‐order IEM were introduced to simulate the high‐altitude electromagnetic pulse (HEMP) in our former reports, where the planar gamma radiation model and the point gamma radiation model were utilized, respectively. Herein, the equation of the IEM is analyzed and simplified, after which the fifth‐order method is introduced. Several asymmetric

Anomalous propagation conditions may cause multipath fading and strong signal enhancement on terrestrial line of sight links or interference on transhorizon paths. In detecting this conditions, spatial distribution of vertical refractivity gradient and ducting index were estimated across Nigeria using atmospheric data obtained from Era5 archive of European Centre for Medium‐Range Weather Forecasts

This paper presents 3–4 and 38–40 GHz wideband channel characteristics for industrial internet‐of‐things (IIoT) scenario based on measurements. The channel measurement equipment applied in the measurements consists of a programmable vector network analyzer and necessary auxiliaries. An extensive amount of data in line‐of‐sight (LoS) and non‐line‐of‐sight (NLoS) scenarios is collected with omnidirectional

No abstract is available for this article.

For various precise navigational applications using Indian NavIC system, it is imperative to have an accurate estimation of the ionospheric line‐of‐sight total electron content (TEC). In dual frequency TEC estimation from code and carrier phase measurements, the error is mainly caused by the satellite and receiver differential instrumental biases, which can be several TEC units. The reason for the

GPS amplitude and phase scintillations in terms of the index S4 and σϕ and the corresponding losses of lock in signal have been studied with consequent errors in receiver positions for the whole month of March 2014 from Calcutta situated near the northern crest of the equatorial ionization anomaly (EIA). The impact of phase and amplitude scintillations is found to be different on GPS satellites in

Horizontal phase speeds for a medium‐scale traveling ionospheric disturbance (TID) are calculated from three different atmospheric gravity wave (AGW) dispersion relations using vertical phase speeds derived from vertical ionograms measured by a single ionosonde. Observed heights from a network of four ionosondes in southern New Mexico provide the measured phase velocities. Horizontal phase speeds calculated

In this paper, first, energy detection (ED) based spectrum sensing inorthogonal frequency division multiplexing (OFDM) system using National Instrument (NI) Universal Software Radio Peripheral (USRP) 2942R software defined radio platform has been implemented. It is observed that in practical scenario ED scheme gives poor performance at low gain (G) values. To overcome the shortcomings of energy detection

This study mainly focuses on the prediction of the variability of the vertical total electron content (VTEC) and validation of the new versions of the International Reference Ionosphere (IRI 2016), IRI extended to the plasmasphere (IRI‐Plas 2017), and NeQuick 2 models over the equatorial anomaly region during 2013–2018. The Global Positioning System (GPS)‐derived VTEC data inferred from the South American

A multiuser full‐duplex (FD) two‐wayrelaying system is considered with decode‐and‐forward relaying protocol. All nodes are assumed to have FD abilities, and residual self‐interference (RSI) at each node is modeled as a Rician‐distributed random variable. Based on the availability of channel state information (CSI) at the relay node, different scheduling schemes are adopted and investigated in terms

One of the newly launched satellite navigation systems is the Indian Regional Navigation Satellite System (IRNSS) operating at L5 and S band and providing position determining with an accuracy of 10 m over the Indian subcontinent and 1,500 km beyond. Collocation of this constellation, containing three geostationary and four geosynchronous satellites, with GPS over a common ionospheric volume at certain

Like any other system relying on transionospheric propagation, Global Navigation Satellite System (GNSS) Radio Occultation (GNSS‐RO) is affected by ionospheric conditions during measurements. Regions of plasma irregularities in F region create abrupt gradients in the distribution of ionized particles. Radio signals propagated through such regions suffer from constructive and destructive contributions

Turbulence in the atmosphere plays a vital role in controlling the surface, lower and upper tropospheric dynamics. Here, we have utilized a newly installed Aryabhatta Research Institute of Observational Sciences (ARIES) Stratosphere Troposphere (ST) radar at the high‐altitude subtropical site in the central Himalayan region (Nainital, 29.4°N, 79.5°E, 1793 m above mean sea level) for the first ever

This paper presents the global three‐dimensional morphology and seasonal variation of the scintillation index at E‐layer altitudes varying from 70 to 140 km. An attempt is conducted to analyze the scintillation distribution in different latitude bins and to explore solar and geomagnetic activity‐dependent characteristic of E‐layer scintillations. The scintillation index is derived from the signal‐to‐noise

Super Dual Auroral Radar Network (SuperDARN) radars operate in a coordinated but monostatic configuration whereby high‐frequency (HF) signals scattered from ionospheric density irregularities or from the surface of the Earth return to the transmitting radar where Doppler parameters are then acquired. A bistatic arrangement has been developed for SuperDARN radars in which HF signals transmitted from

In the fifth generation (5G) wireless communication, high‐speed railway (HSR) communication is one of the most challenging scenarios. By adopting massive multi‐input multioutput (mMIMO) technology in HSR communication, the design of the underlying communication system becomes more challenging. Some new channel characteristics must be studied, such as nonstationarity in space, time, and frequency domains

The MAVEN Radio Occultation Science Experiment (ROSE) generates vertical profiles of electron density in the ionosphere of Mars from two‐way, single‐frequency radio occultation observations. Here we develop methods for generating vertical profiles of ionospheric electron density from frequency residuals obtained from such observations. We show that the relevant set of equations can be closed for ionospheric

In this paper, we present a novel improved wind‐driven optimization (IWDO) for transmit beamforming of phased array radar, which is assumed as a multiple constraints optimization problem. First, the emitted signal model and objective functions of optimization with constraints are presented. Second, all air parcels are divided into feasible and infeasible parcels, and then the target function and constraint