The present study investigates the ionospheric impacts of three intense geomagnetic storms that occurred on 10–11 May 2024 (Sym-H: –518 nT), 23–24 April 2023 (Sym-H: –233 nT), and 23–24 March 2023 (Sym-H: –170 nT) during the ascending phase of solar cycle 25. The storm-induced ionospheric perturbations analysis over dip equatorial station in Thanjavur, India (geomagnetic: 2.49°N, 152.26°E) has been done by using GPS derived TEC data. Results reveal that the intensity and onset timing of storm influences magnitude and spatial extent of ionospheric disturbances. Interestingly, both positive and negative ionospheric impacts have been observed during different phases of storms. The results are also significantly larger ionospheric responses to those storms that initiated during local midnight hours, as observed during the event that occurred in May 2024. However, the modest positive and negative ionospheric responses detected during the different phases of storms could be the result of prompt penetration of electric fields (PPEFs) and disturbance dynamo electric fields (DDEFs). Thermospheric alterations, driven by Joule heating and circulation changes from high-latitudes toward equator, thereby modulating overall ionization rates. To the best of our knowledge, this study provides one of a few comparative ground-based GPS-TEC analyses of these three intense geomagnetic storms of different origin over the Indian near-geomagnetic-equatorial sector, emphasizing how storm onset local time and storm nature influence the sign, magnitude, and timing of ionospheric response. These findings may enhance understanding of how equatorial ionosphere reacts to intense geomagnetic disturbances, thereby supporting efforts to develop robust space-weather forecasting and modelling systems.

A dual frequency band circularly polarized NavIC (Navigation with Indian Constellation) Antenna for radio determination of the L1 band 1575 MHz and S-band 2492MHz which we use for GNSS (Global Navigation Satellite System) application was designed. The simulated results show circular polarization can be attained at L1 and S bands with RHCP (Right Hand Circular Polarization). The motion of current flows in the electric field and magnetic field direction at L1 and S-band frequency are articulated. The Axial Ratio (AR) for the L1 band is 1.09 dB and the S-band is 3.31 dB. The defective ground structure is incorporated to accomplish dual-band polarization. The The NavI Cantenna achieves the Bandwidth for the L1 band and S-band is 30 MHz and 42 MHz, respectively. The gain value for 1.575 GHz is -5.56 dB and the frequency for 2.492 is -5.82 dB. CST studio suite 2024 version was used for the simulation.

This paper presents the design and analysis of a phase gradient metalens for gain enhancement with focused beam in broadside direction and operates at the L5 frequency band (1.176 GHz) for Global Navigation Satellite System (GNSS) applications. The planar lens has 20 x 20 array configuration and transforms the phase profile of the electromagnetic wave propagating through it by providing varying phase response. It is a 1-bit phase quantized lens with bit-0 and bit-1 meta-atoms consisting of three identical layers separated by an air gap of 44 mm. The designed lens is highly polarization-insensitive and has a size of 600 mm x 600 mm. The proposed lens has a focal length of 300 mm and uses a vivaldi antenna as the feed source resulting in a f/D ratio of 0.5. The proposed lens improves the gain of the feed antenna by 9.23 dB and thus the maximum gain of 15 dBi is achieved in the broadside direction at 1.176 GHz. This results in the beamwidth reduction by 52.4 degree resulting in a broadside beamwidth of 23.9 degree and improvement in side lobe level by 6.7 dB from 9.1 dB to -15.8 dB.

Abstract To investigate solar activity dependence of the coupling between medium-scale traveling ionosphere disturbance (MSTID) and sporadic E (Es) layer, we analyzed the total electron content (TEC) obtained from a Japanese global positioning system (GPS) receivers and ionosonde at Kokubunji (35.7° N, 139.5° E) in Japan during the summer period of May–August from 1998 to 2019. To obtain perturbation TEC caused by MSTIDs, the detrended TEC is calculated by subtracting 1-h moving averages from the measured TEC for each pair of GPS satellite and receiver. The detrended TEC data are mapped on to the geographical coordinates to make detrended 2-D maps with spatial resolution of 0.15° × 0.15° in longitude and latitude. The MSTID activity is defined as a ratio of the standard deviation to the background TEC over Kokubunji in Japan. Day-to-day variations of the MSTID activity during summer nights was compared to Es layer parameters [critical frequency ( $${f}_{o}Es$$ f o E s ) and $${\Delta f}_{o-b}\equiv {f}_{o}Es-{f}_{b}E$$ Δ f o - b ≡ f o E s - f b E , where $${f}_{{\text{b}}}Es$$ f b E s is blanketing frequency] derived from ionosonde station at Kokubunji. We have found that the correlation coefficient between the MSTID activity and $${f}_{o}Es$$ f o E s ( $${\Delta f}_{o-b}$$ Δ f o - b ) between 1998 and 2019 is 0.5 3 (0.46) on average, suggesting that there is an electrodynamical coupling between the Es layer and F region could generate nighttime MSTIDs. We also have found that the correlation coefficient positively correlates with solar activity. This finding indicates that in the high solar activity conditions, when the growth rate of Perkins instability is relatively low, generation of the polarization electric fields in the $$Es$$ Es layer could play a more important role to grow MSTIDs than in the low solar activity conditions. Graphical Abstract

A Co-Planar Waveguide (CPW) fed conformal Multiple Input Multiple Output (MIMO) antenna is presented by deploying circular and rectangular patch in a stacked configuration. The analytical equations for the antenna are modeled and compared with the proposed antenna. The antenna is designed on a flexible polyimide substrate featuring a dielectric value of 3.5 with 0.1 mm thickness resonating at two frequencies, LTE-42 Band (5G-V2X) 3.4-3.6 GHz and Dedicated Short Range Communication (DSRC) 5.850-5.925 GHz. The design is further extended as a 4 x 4 MIMO structure by positioning the antenna elements orthogonal, separated by a distance of 10 mm. The antenna exhibits a reflection coefficient < -10 dB with a gain value between 4.5 and 5.25 dB over the desired frequencies. The radiation efficiency of the antenna is around 90% at both bands. MIMO parameters were measured to analyze the MIMO performance of the proposed antenna and the placement analysis of the antenna is studied by mounting the antenna on various vehicle positions and their corresponding pattern were characterized. The designed MIMO antenna is fabricated and tested, having an overall size of 85 x 85 x 0.1 mm(3), offering extremely flexible design functioning to be a promising candidate for next-generation V2X Communication.

The leading cause of cancer-related deaths in women is breast cancer. The likelihood of survival can be significantly increased by early detection of breast cancer. Breast cancer detection using microwave imaging has shown promising results because it is non-invasive and inexpensive. In order to create an image, microwave imaging works by passing microwave signals through the breast tissue and measuring the signal. Since cancerous tissues have different electrical properties than healthy tissues, they interact with microwaves differently. Since microwave imaging uses non-ionizing radiation, numerous studies have demonstrated its potential for breast cancer detection. To increase the technique's precision and dependability, more study is required. Designing an antenna for microwave breast cancer imaging is the goal of this work. . The frequency range of 20-30 GHz offers a good resolution and penetrative power required for imaging. A planar array design has been chosen to provide high directivity for the antenna. The detection is simulated using EMPro© for various positions and sizes of the tumor. The proposed system is able to successfully detect tumors as small as 1.25 mm.

This paper presents the design and analysis of a single-band patch antenna operating at the L5 frequency band (1.176 GHz) for Global Navigation Satellite System (GNSS) applications. The antenna utilizes a single coaxial feed and is implemented on an FR-4 substrate, known for its cost-effectiveness and ease of fabrication. Circular polarization is achieved through strategic truncations and slots on both the patch and ground plane without the use of any external phase shift and power divider network. The simulation results show a -10 dB reflection coefficient bandwidth of 70 MHz (1.140 GHz to 1.210 GHz) with an S11value of-17.29 dB at the L5 frequency band and the 3 dB axial ratio bandwidth of approximately 20 MHz (1.166 GHz to1.186 GHz) with an axial ratio of 1.75 dB at the L5 frequency band. Additionally, a nine-element antenna array, measuring 260 mm x 270 mm, is developed using the same antenna element. The array provides a good impedance matchingwith an S11value of -20.02 dB at the centre frequency and S11of below - 10 dB within the operating bandwidth of GPS L5 frequency band and an axial ratio of 2.24 at the centre frequency and below 3 dB level over a narrow frequency range. The suitability of the antenna and its array for GNSS applications is validated through simulated results, which are thoroughly discussed in this paper. Furthermore, the beam-switching simulation results of the antenna array have also been carried out,allowing for dynamic adjustment of the antenna's radiation pattern to enhance signal reception and mitigate interference.

In this study, we consider Bi-directional Long Short Term Memory (Bi-LSTM) model based Vertical Total Electron Content (VTEC) prediction over Thanjavur (Geographic 10.72˚ N, 79.01˚ E, Geomagnetic 2.34˚ N, 152.19˚ E) Global Positioning System (GPS) station. This station is located at low latitude Equatorial Ionization Anomaly (EIA) region of 2˚ geomagnetic dip latitude and has unique ionospheric dynamics. In this region, the VTEC prediction is crucial and challenging for space weather and the Sixth Generation (6G) Internet of Space (IoS) application to support early warning systems and future spatial data transmissions. A Deep Learning (DL) model based on Bi-LSTM was developed and trained for F10.7 and Dst index for predicting the VTEC. This study highlights the prediction of VTEC for any day that includes solstice and equinox time frames. The Bi-LSTM has an improvement of 28 % in mean absolute error (MAE), 48% in mean square error (MSE) and 24% in root mean square error (RMSE) as compared to the conventional Long Short Term Memory (LSTM) network. Hence, this Bi-LSTM model can be helpful to predict the VTEC in the EIA region and may be helpful to extrapolate over the unmeasured grid region of ocean and land.

The ionosphere’s dynamic fluctuations are a persistent challenge to satellite navigation and communication. The total electron content (TEC) information from global navigation satellite system (GNSS) signals provides the status of the ionosphere for fail-safe transionospheric communication. The equatorial ionization anomaly (EIA) and equatorial plasma bubble (EPB) dominate in low latitude and equatorial ionosphere. The low solar activity's fast varying pre-reversal enhancement is low, and slow varying gravity waves can seed ionospheric disturbances. This study analyses the vertical TEC (VTEC) variations using a ground-based global positioning system (GPS) receiver at Thanjavur (10.72° N, 79.02° E), Tamil Nadu, India, for the years 2019 and 2020, with specific emphasis on the Equinox and Solstice conditions during low solar activity. The suitability of global ionospheric models such as IRI-Plas and NeQuick2 models is investigated with low solar activity GPS VTEC observations. VTEC variations are more during the Vernal Equinox compared to other seasons. The NeQuick2 model underestimates the VTEC content during the night hours and overestimates the day's evening hours regardless of the month, perhaps due to higher ITU-R coefficients. The results help us improve IRI-Plas and NeQuick prediction models' accuracy.

A wideband quad-port Multiple Input Multiple Output (MIMO) antenna with efficient isolation characteristics for 5 G New Radio (5 G-NR) applications is presented. The proposed antenna works in the span of 3-6 GHz frequency covering the n77/n78/n79 bands also covering the 5 G-V2X band (3300-5000 MHz), LTE-46 band (5150-5925 MHz) and Dedicated Short Range Communication (DSRC) at 5.9 GHz band. The single element of the MIMO antenna structure is modelled by an elliptical structure stacked on a rectangular patch along with the feedline on the conducting plane. The ground plane is modelled as a rhombic design providing a Defected Ground Structure (DGS) to provide the resonance at the desired frequency band. Later, the antenna is evolved as a four-element MIMO system by arranging the antenna elements orthogonal to each other with a distance of separation between the adjacent antenna elements considered to be 10 mm. The all-inclusive dimension of the proposed antenna is 65 x 65 mm2. The simulated MIMO structure is fabricated and measured for antenna parameters and MIMO parameters such as isolation characteristics and MIMO diversity performances. The simulated values are obtained at acceptable limits with the measured values for the proposed wideband frequency range of operation. The compact, wideband antenna is found to be suitable for various 5 G-NR applications, especially Wi-Fi-assisted Vehicular Communication in the sub-6 GHz frequency range.

The Strategic missiles attempts to attack the enemy forces at a distance greater than ten thousand kilometers which are either propelled by the jet engines or the rockets. The detection and destruction of the missiles is a significant step for a nation to protect its land. Missile countermeasure methods are used to counter the missiles which includes active and passive methods. In Passive method the naturally emitted energy by the missile is detected whereas in the active detection method a radio signal is transmitted, and the backscattered signal is measured to find the range and the velocity of the target.

The hypersonic missiles are the type of missiles which can travel above Mach 5 that is 5 times the speed of sound. The hypersonic missiles with nuclear or non-nuclear warheads causes threat not only nationally but also globally. Due to their high speed, heat is produced which breaks down the molecules in the atmosphere causing formation of ionized gas layer called as Plasma stealth. So, it is very challenging to detect hypersonic missiles but few vulnerabilities of hypersonic missiles make it possible for its detection. The Plasma Stealth itself can be used to detect the hypersonic missiles. By detecting the Plasma footprint which will last for few milliseconds, the hypersonic missiles can be detected.

In this paper, modified analytical equations for the total electric field intensity in the far field region of a 10 MHz bent wire antenna have been proposed. The antenna system is meant for the airborne ground penetrating RADAR application for bedrock survey. This bent antenna is having vertical, slant and horizontal segments joined together along with the parasitic element. The current in the antenna wire is assumed to be a sinusoidal distribution which drops to zero at the ends. Current in both the energized and parasitic elements contribute to the fields in the far field region of the antenna system. Separate field equations for the various segments of the antenna system have been derived and finally summed to obtain the required equation for the electric field intensity at the far field region of the antenna. The MATLAB R2017b© simulation results of the far field antenna analytical equations show good agreement with the HFSS© simulation results of the 10 MHz antenna system. Direct measurements of these radiation characteristics in a typical GPR environment present a lot of practical difficulties. In this work, the influence of the helicopter on the 10 MHz GPR antenna during the airborne survey, is simulated using EMPro© and analyzed. This placement analysis resuls from the simulation gives us the appropriate range of distance values that can be maintained between the helicopter and antenna during the glaciological survey before performing the real time survey. A tradeoff between scattering parameter (S11) and directivity is considered to propose the optimum distance. The overall antenna structure seems to be a promising candidate for low frequency airborne GPR glacier explorations.

Wireless networks exploiting massive MIMO technologies come in handy to meet the demands of increasing data traffic and enhance network capacity and coverage for imminent communications. A large number of RF chains and energy-efficient antenna arrays are used on a broad scale to intensify the data rate and system throughput. This results in computational complexity and high energy requirements. To overcome this concern, a transceiver with Hybrid Beamforming is designed at 3.5 GHz (IMT range 3.5-3.8 GHz) using SystemVue© software. 3.5 GHz is preferred for its technical characteristics that make it effective in delivering high-speed services. It has the capacity to afford a considerable amount of contiguous spectrum that will support channels with wide bandwidth, ideal for 5G deployment. Transceiver designs with Hybrid Beamforming for sub 6 GHz MIMO systems with OFDM source are viable to reduce the volume of RF chains, disintegrating the signal processing into the analog and digital domains. Simulation results are analyzed based on various beamforming parameters like antenna array spacing, sidelobe suppression, directivity, beamforming gain and the use of a minimum number of RF chains is ensured. The proposed design provides a near-optimal performance close to the digital Beamforming with sharp beams.

In this paper a compact dual band planar hexagonal patch antenna with meander transmission line fed by co-planar wave guide is proposed. The antenna resonates at 2.51-2.69 GHz and 3.52-4.10 GHz, which makes it suitable for 2.57 GHz (LTE) and 3.78 GHz worldwide interoperability for microwave access (WiMAX) frequency bands, respectively. This hexagonal patch is designed on FR-4 substrate with 1.6 mm thickness. The antenna is fed by a meandered transmission line which reduces the overall size of the antenna. The planar hexagonal patch antenna is smaller in size as compared with conventional microstrip patch antenna and has a good agreement with the simulation results. Hence, the antenna is suitable for LTE and WiMAX band applications.

A direction shifting electronically beam steerable Microstrip antenna array is proposed. In order to reduce the overall size, the antenna array is designed on a dielectric substrate. A single antenna element in the array consists of a dipole element and two parasitic elements, designed over a multilayer dielectric structure. The length of the parasitic elements can be reconfigured using RF switches. Switching the length of the parasitic elements in various configurations, the main lobe of the single antenna of the array is shifted in three directions. This leads to three modes of operation. By configuring the switches of every antenna in the array, the main lobe of the array shifts the direction. The main lobe of the antenna array in a particular mode is made steerable by changing the phase shift between the antenna elements. Simultaneously altering the length of parasitic elements by switches and changing the phase shift between the antenna elements in the array, the main lobe is made steerable in any of the three modes. This paper discusses the design of an array with pattern reconfigurability and beam steering on multilayer structure with a minimum number of RF switches. The proposed antenna is designed to operate in C Band.

GNSS/GPS having wide application in Civil and defence sectors like aviation, transport, navigation, survey, vehicular and secured communications. This GNSS/GPS will be vital for future navigation systems, especially in the intelligent transport system (driverless vehicle) and vehicular communications. Nowadays, spoofing is a significant threat that can divert the route or trajectory of mobile units (ground or airborne). To identify and minimise spoofing, many methods have been tried. Methods such as identifying anomalous carrier-to-noise ratios, the interval amongst the phase changes, the delay in between signal broadcast at various frequencies, spatial data processing, and determining the direction of arrival using an antenna array were all successfully applied. Nevertheless, still, there are challenges to be addressed in spoofing detection. In this short communication, we propose using ionospheric signature as an augmentation to the existing methods to detect spoofing more effectively. By the continuous estimation of the ionospheric parameters from the received signal since the beginning of the navigation and comparing it with the model derived values, one can effectively identify the spoofing signal. When added with the existing spoofing detection methods, this method implemented in real-time will become a powerful tool.

A compact printed monopole antenna mounted on a FR-4 substrate having a dielectric constant of 4.6 fed by the transmission line operating between 5.925 GHz and 7.125 GHz frequency range with minimum bandwidth of 1200 MHz is proposed for Wi-Fi 6E applications. The designed antenna is simulated using the Keysight Advanced Design System (ADS) software and various other antenna parameters required for the specific functioning of the antenna under the IEEE 802.11 ax standards are analyzed. The results showed that the antenna has bandwidth approximately more than 2000 MHz which is greater than desired bandwidth making it suitable for Wi-Fi 6E applications. Matching network is also designed to transfer maximum power from source to load.

This article presents a compact Co-Planar Waveguide (CPW) fed antenna for next-generation Vehicular Communications. The antenna is designed by employing two rectangular stacked patch structures and slots, making the antenna resonate at dual frequency bands. The analytical study of antenna design is carried out using the governing microstrip patch equations. On optimizing the patch's dimensions for CPW structures, the desired frequency range of operation is obtained for the single element antenna structure. The designed antenna resonates at 3.5 GHz (LTE-42 Band) and 5.9 GHz (DSRC Band), yielding this antenna to be a prime component for Vehicular to Everything (V2X) Communication. The optimized single-element antenna structure is 35 mm × 20 mm designed on an FR-4 substrate of thickness 1.6 mm. The substrate has a dielectric constant of 4.4 and a loss tangent value of 0.001. Further, the antenna structure is developed as a 4-element MIMO configuration with the distance between adjacent antenna elements to be 10 mm. The adjacent antennas in the MIMO configuration are positioned orthogonal to each other, thereby exhibiting better isolation between the antenna elements. The antenna has a reflection coefficient value of < −10 dB within the bandwidth of interest and VSWR less than 2. The Gain value of the designed antenna ranges between 2.8 and 2.9 dBi at 3.5 GHz and between 3.6 and 3.7 dBi at 5.89 GHz. The overall efficiency of the antenna element is between 60 and 80% at both frequency bands. MIMO parameters are analyzed by calculating the Channel Capacity Loss (CL), Diversity Gain (DG), Envelope Correlation Coefficient (ECC) and Total Active Reflection Co-Efficient (TARC). The designed antenna is fabricated and tested, which shows the measured results coincide with the simulated antenna results. The overall dimension of the MIMO configured antenna design is 60 mm × 60 mm × 1.6 mm, which is highly compact and is a suitable candidate for deployment of Vehicle to Vehicle (V2V), Vehicle to Infrastructure (V2I), and Vehicle to Network (V2N) scenarios.

A half-wave dipole antenna can be bent into different directions based on angles to fix any desired space. It can resonate at various angles providing different antenna parametric values. This paperfocuses on the analysis of adipole antenna when its edges are bent at various angles. Generally, dipoles are not bent unless they find it difficult in placing the antenna in a tight space. At such times these bent antennas are used to study the variations when the dipole is bent physically and can be used for low frequency applications. The antenna is modelled using 4Nec2 software and the simulated parameters of the antenna are analysed.