A dual-band serrated microstrip MIMO antenna is proposed for 5th generation wireless applications in this article. The simulated -10 dB impedance bandwidth of 160 MHz (3.340-3.50 GHz) and 220 MHz (5.50-5.72 GHz) can cover 3.40-3.60 GHz and 5-5.7 GHz fifth generation bands. Here the designed MIMO antenna is a serrated basic microstrip patch antenna. A full ground copper layer has been utilized in the design to attain a better isolation, whereas the fabricated antenna's isolation among the antenna elements is measured to be greater than -20 dB. In addition, the measured ECCs are less than 0.0025 and 0.001 at the two resonant frequency bands and for the two MIMO antennas. The antenna diversity parameters covering ECC and DG were analyzed. The average gain for the single-element, dual-port and quad-port MIMO antennas is 3 dBi. These parameters make the serrated microstrip MIMO antenna also suitable for intelligent IOT devices operating in sub-6 GHz band.

Electromagnetic energy is being utilized over multiple frequency bands to sustain high speed wireless communication systems around the globe. As a consequence, living bodies such as humans, animals, plants, and fruits continuously get exposed to electromagnetic radiation. To safeguard human health, a number of diversified international and national electromagnetic regulatory standards have been prescribed across geographical boundaries for limiting electromagnetic radiation - specific absorption rate and reference power density limits have been prescribed by the international organizations to protect humans from immediate thermal effects. However, reference power density limits differ by ten to hundred times across geographical boundaries depending upon the electromagnetic standards in effect. Moreover, prescribed reference power density limit also varies with frequency of irradiation. On the other hand, plants and fruits possess reasonably high permittivity and electrical conductivity that contribute to considerable electromagnetic energy absorption rates inside typical plant and fruit models. In addition, plants and fruits are primarily asymmetric in nature, and therefore direction of arrival and polarization of incident electromagnetic field are two additional factors that significantly influence the amplitude and spatial distribution of specific absorption rate. Therefore, prescribing only the maximum permissible power density limit in far field seems inadequate. To address these issues, specific absorption rates inside a typical multilayer mango fruits model have been estimated at five different frequencies in accordance with four different international and national electromagnetic regulatory standards (with contrasting reference power density limits) - the magnitudes and spatial distributions of specific absorption rates have been quantified and reported at different frequencies as well as for distinct averaging techniques. Moreover, the impact of direction of arrival and polarization of incident electromagnetic field on the magnitude and spatial distribution of specific absorption rate has also been investigated. A total of one hundred and twenty rigorous simulations has been performed, and as a consequence, four hundred and eighty specific absorption rate data points have been analyzed. Wide disagreement in specific absorption rate data is observed due to variations in four factors mentioned above, i.e. reference power density, frequency, direction of arrival, and polarization of incident electromagnetic field. Moreover keeping all the other factors unaltered, specific absorption rate cannot be directly correlated with the reference power density limit primarily due to non-identical and asymmetric structures of bunch of fruits and plants in most practical scenarios. Thus, observations indicate the necessity of adopting globally harmonized electromagnetic regulatory standards and direct adoption of specific absorption rate limit for plants and fruits instead of only the reference power density limits in far field exposure scenario.

Parity-time (PT) reversal symmetry, as a representative example in the field of non-Hermitian physics, has attracted widespread research interest in the past few years due to its extraordinary wave dynamics. PT-symmetry enables unique spectral singularities, including the exceptional point (EP) degeneracy where two or more eigenvalues and eigenvectors coalesce, as well as the coherent perfect absorber-laser (CPAL) point where laser and its time-reversal counterpart (i.e., coherent perfect absorber) can coexist at the same frequency. These singular points not only give rise to new physical phenomena, but also provide new plausibility for building the next-generation sensors and detectors with unprecedented sensitivity. To date, investigations into EPs and CPAL points have unveiled their great potential in various sensing scenarios across a broad spectral range, spanning optics, photonics, electronics, and acoustics. In this review article, we will discuss on going developments of EP- and CPAL-based sensors composed of PT-synthetic structures and offer a glimpse into the future research directions in this emerging field.

Exact analytic solutions for the electromagnetic field due to a thin, uniform circular loop current are presented. The solutions are provided in the form of a power series with respect to wavenumber. The coefficients of the series are real functions of the spatial coordinates and loop radius and involve recursions of complete elliptic integrals or finite sums of elementary functions. Explicit expressions for the magnetic vector potential and electric and magnetic fields are provided for both cylindrical and spherical coordinate systems. The expressions are adapted for computing the electric field and axial magnetic field on the interface of two half spaces generated by a current loop lying on the half-space interface. Expressions for the self and mutual loop impedances are provided for both the free-space and interface case. Computed examples are given for specific frequency and half-space parameters and are compared to known solutions based on spherical Hankel functions or direct integration. The solutions are shown to be particularly efficient in the near field. Their derivation is motivated by recent developments of large sensors used in magnetic resonance sensing of minerals.

The folding antennas are anticipated to become mandatory because of integration necesity according to communication object shapes. The effect of folded antennas on the electromagnetic (EM) radiation is an open question for RF and microwave wireless engineers. An innovative approach to explore the flexible patch antenna (FPA) parameters through V-folding analysis is addressed for this problem. This paper is focused on the methodological approach of FPA study by considering an innovative V-folding behaviour compared to the classical flat condition. As proof-of-concept, FPA prototypes are designed on Kapton substrate, simulated, fabricated, and tested. A non-shifting operating frequency is achieved at 3.4 GHz for all percentage-wise folding with a flat (unfold) bandwidth of about 360.8 MHz with good acceptable performance. The FPA performance prediction as reflection coefficient, efficiency, gain, and directivity versus forward and back V-folding percentage and angle is examined. The obtained result can be exploited to predict the V-folding effect on the communication performances of transceiver systems like radar, satellite and multimedia applications.

Interrupted Sampling Repeater Jamming (ISRJ) can produce several false targets through intermittent sampling and forwarding of the intercepted signals. The paper proposes an interference identification and suppression method based on Short-Time Fourier Transform-Energy Distribution Correlation Judgment (STFT-EDCJ) to lessen the impact of the false targets mixed in echo pulses. Firstly, the method obtains the energy distribution of echoes in the time-frequency domain employing the short-time Fourier transform, extracts the time slice of higher energy targets through energy peak detection, and then calculates the Pearson correlation coefficient (PCC) of the energy distribution in the frequency domain of each target time slice to construct the Target PCC Datasets (TPCCD). Secondly, it distinguishes between the real target and false targets after echo pulse pressure by the range and specificity of TPCCD. Finally, it uses mapping the time domain position of the false targets to suppress interference. The abundant simulation results verify the proposed method's effectiveness, and the Monte Carlo simulation demonstrates the method's usefulness under ISRJ models.

Wearable textile antennas have obtained remarkable attention in various medical fields due to their ease of integration and flexibility. This paper puts forward an Ultra Wide Band (UWB) Compact Textile Wearable Antenna (CTWA) for Wireless Body Area Network (WBAN) applications. The proposed antenna is a semicircular slotted elliptical antenna with an L shaped stub and a partial defected ground plane. The antenna is fabricated on denim jeans (ε_r = 1.77) and has an overall dimension of 27 × 28 × 0.7 mm with an operating frequency range 3.01-15.98 GHz, radiation efficiency of 83.5-90.11% and maximum gain of 5.81 dBi. Structural deformation studies including human body loading of the antenna are carried out, and the performance of the antenna is found to be stable. The proposed antenna has a low profile and high fractional bandwidth (137%) compared to the UWB wearable antennas reported in the literature. The calculated Specific Absorption Rate (SAR) of the antenna at the frequencies 4,7 and 10 GHz are 1.2, 1.06, and 1.58 W/Kg, respectively, which lies within the FCC (Federal Communications Commission) standard. The proposed CTWA is compact, flexible, wearable, and robust, which makes it suitable for on-body WBAN applications.

The THz spectrum (0.1-10 THz) is a region between optics and electronics, and it is still not fully explored and is unlicensed. Recent studies show that it will bring a revolution in technology, especially in the field of communication. Future communication technologies such as 6G and Terabit DSL will utilize this THz band as it has the capability to support high data rates in Tbps. For designing an efficient system that propagates these THz waves with low loss, it is required to understand the propagation channel properly. THz channel modeling is at its infancy stage, and a detailed investigation of channel behavior is required to study the efficient propagation of THz waves. In this study, the methods applied to the modeling of the THz channel are discussed in detail. Although channel modeling is a broad topic here only the methods and techniques are discussed along with their advantages and limitations. Lastly, the challenges and the future direction in the field of THz channel modeling are also discussed.

This paper addresses the bandwidth limitations inherent in microstrip patch antennas, which are commonly employed in radar applications owing to their compact size and integration convenience. To overcome these limitations, this study explores the application of Prosopis Africana conductive ink-based thick film, an innovative and environmentally friendly material. Originating from the African mesquite tree, this ink exhibits high conductivity owing to its elevated carbon content, presenting a compelling solution for enhancing microstrip patch antenna bandwidth. The research entails thoroughly examining microstrip antenna design principles and associated challenges, followed by exploring the unique properties of Prosopis Africana conductive ink. A detailed methodology outlines the fabrication process of the ink-based thick layer or film on the substrate, with simulation and measurements employed to evaluate its impact on impedance matching and radiation characteristics. Emphasizing the eco-friendliness of Prosopis Africana conductive ink aligning with green electronics trends, the study showcases its potential for advancing wireless communication systems while reducing ecological footprints. Results demonstrate a substantial bandwidth improvement exceeding 1.85 GHz, a simulation |S₁₁| return loss value of -16.19 dB, and achieved 84.5% radiation efficiency of the operating frequency at 9.5 GHz and a peak realized gain of 7.10 dB. Hence, integrating Prosopis Africana conductive ink-based thick film is a viable strategy for augmenting microstrip patch antenna bandwidth, rendering them more adept for radar applications.

This paper presents a circularly polarized double wall substrate integrated waveguide (SIW) fractal slot antenna array designed for X-band satellite applications. The proposed antenna demonstrates a reflection coefficient, covering the frequency range from 7.3 GHz to 8.5 GHz. The antenna is circularly polarized with a 3-dB axial ratio bandwidth ranging from 7.88 GHz to 8.58 GHz. The antenna array exhibits a gain variation between 11 dBi and 12.51 dBi. Moreover, the proposed design achieves an efficiency of 89%. With overall dimensions of 177 mm x 48.8 mm x 3.175 mm (4.8λ₀ x 1.32λ₀ x 0.086λ₀), the antenna array is compact and suitable for satellites with limited surface area. This compact form factor facilitates seamless integration into satellite systems without compromising performance. The proposed antenna is suitable to be employed for the satellite X-band telemetry application extending from 7.9 GHz to 8.4 GHz. A prototype of the proposed antenna has been fabricated and then measured using Vector Network Analyzer (VNA) and Anechoic chamber. The proposed antenna's measurement results match the simulated results.