The Global Positioning System (GPS) cycle slip has a marked impact on the application of communication and navigation systems and therefore is one of the main concerns of the user and designer of terminal systems. In this study, we analyzed the temporal and spatial characteristics of cycle slip events using the GPS data detected from 260 observations in the China sector during the period of the year

This paper describes the development of superconductor–insulator–superconductor (SIS) receivers in the 787–950 GHz radio frequency (RF) range, which covers the highest frequency band of the Atacama Large Millimeter/submillimeter Array (ALMA) and is recognized as the most difficult band in terms of superconducting technology, because the conventional superconducting material of Nb cannot be used for

Obtaining high‐precision Doppler frequencies for very weak and high‐dynamic signals in deep space exploration is challenging. Such signals are commonly encountered, including in soft landing of lunar probes and the entry, descent, and landing (EDL) phase of Mars probes. Phase‐locked loop (PLL) is a widely used method for measuring high‐precision Doppler frequencies. In this study, two major improvements

The dual‐frequency global positioning system (GPS) data acquired from the UNAVCO over different places of Nepal were processed to examine the eclipse‐triggered consequences on total electron content (TEC) in response to the annular solar eclipse of 15th January 2010 and 21st June 2020. These occasions were exceptional since they occurred during solar minimum, additionally as in a magnetically quiet

Massive Multiple‐Input Multiple‐Output (MIMO) is emerging as one promising technology for the fifth generation (5G), but the hardware and software complexity arising from the sheer number of transmitting elements is a bottleneck. Antenna selection strategies have been reported as an appealing solution for hybrid beamforming architectures to select a number of radio‐frequency (RF) chains less than the

A new method is developed to retrieve electron density profiles from a raw virtual height ionosonde traces. A Kalman filter is used for the assimilative inversion scheme together with the newly developed data‐driven vertical covariance model. The detailed mathematical formalism for the derivation of the Jacobian that takes into account the effect of the magnetic field is presented. The incoherent scatter

In this study, we use a collection of Gaussian striations to generate random realizations of a disturbed ionosphere. The formalism is developed here to create a two‐dimensional realization of electron density by summing a large number of Gaussian striations, uniformly distributed in space and with a given probability density function of their radii. We analytically calculate the power spectral density

Radar and jammer can be considered as two players in the countermeasure game of electronic warfare (EW). A game framework for joint beamforming and power allocation is investigated for multistatic radars and multiple jammers in this paper. Under a certain target detection criterion, the major aim of every radar is to reduce its power consumption and suppress various jammings. Conversely, the multi‐agent

Incoherent scatter radars (ISR) are among the most powerful ground‐based instruments for solar‐terrestrial physics, measuring multiple plasma parameters over almost the entire vertical extent of the ionosphere. In Sanya, on Hainan Island, China, an advanced high‐power phased array ISR, known as the Sanya incoherent scatter radar (SYISR), is under construction. A tristatic system is planned, with a

The Agile Dual Auroral Radar Network (AgileDARN) radar has been developed as an all‐digital high‐frequency (HF) coherent scatter radar. Based on phased array antenna and digital signal processing techniques, digital beam forming (DBF) is employed for both transmission and reception, which steers toward the desired direction based on the relative phases within the array elements. However, the amplitude

In radio astronomy, holography is a commonly used technique to create an image of the electric field distribution in the aperture of a dish antenna. The image is used to detect imperfections in the reflector surface. Similarly, holography can be applied to phased array telescopes, in order to measure the complex gains of the receive paths of individual antennas. In this paper, a holographic technique

No abstract is available for this article.

In this paper, a comprehensive view of the evening and nighttime ionospheric irregularities using Communication/Navigation Outage Forecasting System (C/NOFS), Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), and Global Navigation Satellite System GPS satellites were carried out over the east African region during June and September 2014. The strength of the pre‐reversal

ULF magnetic anomalies (f < 1 Hz) have been observed prior to multiple large earthquakes (EQs) during the last three decades. A polarization analysis method was produced and applied in many EQ cases in order to discriminate the weak ULF crustal signals from other signals. Although many publications considered the parameter of polarization ratio (amplitude or power ratio of vertical magnetic field component

High frequency (HF) radio waves propagating through regions of ionospheric plasma irregularities exhibit random fluctuations in both amplitude and phase referred to as scintillations, which heavily influences the detection performance of HF sky‐wave radar and hybrid sky‐surface wave radar systems. In this paper, a numerical multiple phase screen model for HF sky‐wave propagation is developed, which

Forty years of studies on bioelectromagnetics, in our laboratory, are presented to view new horizons in electromagnetics in medicine and biology. The several topics are reviewed and discussed. The review includes transcranial magnetic stimulation (TMS) of the human brain, imaging of electrical information in the brain based on magnetic resonance imaging (MRI) such as impedance MRI and current MRI,

This paper presents a comprehensive analysis of results obtained using NWRA’s assimilative ionospheric model GPSII when it is driven by Spire Global, Inc.’s global navigation satellite system ‐ radio occultation (GNSS‐RO) measurements. Results of the assimilative model are validated using the database of Digisonde and Dynasonde ionograms. A week’s worth of dual‐frequency phase data was collected from

This study investigates an innovative theory on design of dielectric resonator (DR) based negative group delay (NGD) microwave circuit. The NGD circuit is mainly constituted by a cylindrical bulk of DR as a coupling element with a microstrip line. The developed theory is analytically established from the S‐parameters modeling of this innovative DR NGD topology. The NGD analysis and synthesis equations

In this paper, a novel and simple dual‐polarized frequency‐selective rasorber (FSR) which has a wide absorption band including a wide transmission band was presented. Detailed equivalent circuit was derived to accurately predict the frequency responses of the structure. Based on reasonable equivalent analysis of a traditional metal grid structure, a modified structure with improved performance was

Phase unwrapping is very important to acquire surface deformation using InSAR, unwrapping the interferometric phase directly is not appropriate because the phase is affected by various noises. Therefore, it is essential to apply a suitable filter to the interferometric phase before phase unwrapping. Although there are many filtering methods for noise, these methods can not be used directly due to the

Among the techniques for atmospheric sounding, radio occultation enables an in‐depth investigation of vertical profiles from the ionosphere to the troposphere by measuring the radio frequency signal associated to the propagation medium. A precise characterization of the atmospheric layers requires a thorough processing of the raw radio tracking data to estimate the thermodynamic properties of the atmosphere

The editors thank the 2020 peer reviewers

The present study explores the center‐of‐mass (Hc) of the ionosphere as the effective ionospheric varying shell height (VSH). We presents global ionospheric maps GIM‐Hc produced with IRI‐Plas model by assimilating the instant GIM‐TEC maps provided by JPL from 1994 to present which allows obtaining global maps of the F2 layer critical frequency, GIM‐foF2 (or NmF2) and peak height, GIM‐hmF2. Ratio TEC/NmF2

No abstract is available for this article.

An inverse problem of reconstructing real permittivity of a plane‐parallel layer in a perfectly conducting rectangular waveguide or in free space from experimental data using an explicit expression for the scattering matrix is considered. In general, this problem is improperly posed and may be unsolvable due to inaccuracy of the experimental data, and for a perfect noiseless experiment the solution

The Ionospheric Continuous‐wave E‐region Bistatic Experimental Auroral Radar (ICEBEAR) is a VHF coherent scatter radar that operates with a field‐of‐view centered on 58°N, 106°W and measures characteristics of ionospheric E‐region plasma density irregularities. The initial operations of ICEBEAR utilized a wavelength‐spaced linear receiving array to determine the angle of arrival of the ionospheric

Refractivity‐from‐clutter (RFC) is a technique for remote sensing of the lowest portion of vertical atmospheric refractivity profile, particularly evaporation and surface‐based ducts. It uses the sea‐surface backscattered radar signal to estimate the ducting conditions. The Lower Atmospheric Propagation (LATPROP) radar is a software‐defined, coherent‐on‐receive remote sensing system built on a low‐cost

This manuscript presents a rectenna with a high impedance asymmetric antenna array for ambient wireless energy harvesting at the 2.45 GHz frequency band. It is fulfilled without using any impedance matching networks, which demonstrations significant benefits over available rectennas as a function of the layout and cost with a wide range of input power level and load impedance. A rectenna prototype

This two‐part article presents a review of different techniques of mutual coupling (MC) reduction. MC reduction is a primary concern while designing a compact multiple‐input‐multiple‐output (MIMO) antenna where the separation between the antennas is less than λ0/2, that is, half of the free‐space wavelength. The negative permittivity and permeability of artificially created materials/structures (Metamaterials)

This two‐part article presents a review of different techniques of mutual coupling (MC) reduction. MC is a major issue when an array of antennas is densely packed. When the separation between the antennas is <λ0/2, i.e., half of the free‐space wavelength, the antenna parameters suffer from the surface wave, and the space wave coupling effect between the antenna elements. To reduce the MC influence

Japanese space weather research and operation began in 1896 with research on radio propagation. LF, MF, and HF radio communication used to be important before the era of communication satellites; however, they are affected by ionospheric conditions and solar activity. A center for the research and development of radio systems was established at Hiraiso, which is now also a space weather observatory

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 for objects of various types

During the guidance of the missile, the target needs to be positioned in real time. The detonating missile will look forward to the target area during the flight, and the imaging distance becomes closer as the missile approaches the target. The image quality of forward‐looking missile‐borne bistatic synthetic aperture radar (FM‐BSAR) deteriorates rapidly when the detonator enters a rapid dive stage

No abstract is available for this article.

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 8 × 8 cells on a light weight plate that is 1.62‐m2 wide with cells 0.25‐m high providing

Modeling long‐range propagation of electromagnetic waves is necessary to study the performance of systems, for applications such as radar or navigation. Such models generally rely on split‐step Fourier (SSF) because large mesh sizes can be used. The split‐step wavelet method (SSW) is a recently developed method allowing to perform the same simulations as with SSF but in a shorter computation time.

A new discovery was made using the radio receiver instrument 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 waves

The first demonstration of rocket exhaust driven amplification (REDA) of whistler mode waves occurred on May 26, 2020 by transferring energy from pickup ions in a rocket exhaust plume to EM waves. The source of coherent VLF waves was the Navy NML Transmitter at 25.2 kHz located in LaMoure, North Dakota. The topside ionosphere at 480 km altitude became an amplifying medium with a 60 s firing of the

This study proposes a metasurface (MS) based high performance antenna in which the radiating patch is embedded with split ring resonators in its square slots. The slotted corner cut rectangular patch antenna with defected ground plane and the MS are placed together in the same plane. The designed prototype operates over dual frequencies with impedance bandwidths (S11 < −10 dB) of 4.02% and 28.24% at

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

Ionosphere is a significant component of the solar‐terrestrial space environment. Geomagnetic storm induces global ionospheric disturbances, severely affect radio communications and human space activities, e.g., earth observation, deep space exploration, and space weather monitoring and prediction. Monitoring ionospheric anomalies are critical to improve the performance of Global Navigation Satellite

We present passive observations of midlatitude sporadic E (Es) structures in the 30–50 MHz range using the long wavelength array 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 emissions

No abstract is available for this article.

This paper introduces a new approach of estimating the daytime horizontal geomagnetic field (ΔH)‐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

Using an argument approach and a combination of historical, contemporary data sets, 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 an n times increase in delivery of glacial melt waters, sediment

This work shows how both frequency and the election of path loss model affect estimated spectral efficiency. Six different frequency bands are considered, ranging from 2.6 GHz in the ultra high frequency (UHF) band to 73 GHz in the millimeter wave bands (mmWaves), using both single‐slope and two‐slope path‐loss models. We start by comparing four urban path loss models for UHF: the urban/vehicular and

The main chemicals of rocket exhaust plume are released into the ionosphere, which cause three‐dimensional (3‐D) disturbances. By simulating the disturbance, we investigate the influence of ionospheric disturbance by the chemical release on the propagation of over‐the‐horizon radar (OTHR) waves. Based on the absorption simulation model, the absorption loss of OTHR waves caused by rocket plume was simulated

Global Navigation Satellite System (GNSS) signals have become a useful tool to analyze signal‐in‐space performance in the presence of ionospheric perturbations with a view to improve 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

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

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.

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

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) remodeling 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 model

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

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