Volume 79, Issue 7-8

This paper presents a novel technique for detecting tumors in human breasts using a single high-gain antenna and a metasurface (MTS) layer. An artificial neural network (ANN) is employed to classify detected tumors as benign or malignant based on the permittivity of the tissue. The detection and classification process leverages the contrast in dielectric properties between normal and abnormal biological tissue, utilizing the actual permittivity as a distinguishing factor. This study highlights the effectiveness of the proposed technique in accurately detecting and localizing malignant tumors within human breasts. Electromagnetic analysis is conducted using voxel datasets derived from human models to validate the approach. Tumor localization is achieved with high precision based on the Specific Absorption Rate (SAR) magnitude. The study considers various fat layer thicknesses (10–100 mm) and tumor radii (2.5–10 mm), addressing scattering effects comparable to the wavelength of the applied microwave radiation. The proposed Vivaldi antenna operates at 3.5 GHz, achieving a gain of 15.5 dBi with a half-power beamwidth in the E-plane of ±12°. Results demonstrate minimal average errors and high-performance indices (PI) for fat thickness (0.1 %, 90 %), tumor size (0.06 %, 94 %), and tumor classification (0.11 %, 89 %). The experimental and simulation results exhibit strong agreement, confirming the feasibility and potential of the proposed antenna system for medical diagnostics and post-detection rehabilitation planning.

A Multiple Input and Multiple Output (MIMO) antenna operating at 2.4 GHz Industrial Scientific and Medical (ISM) band is specifically built and studied for on-body communication. The MIMO elements are identical and designed to resonate at an operational frequency of 2.4 GHz. They are specifically designed to function within an impedance bandwidth of 78.7 MHz. MIMO antenna is constructed on a substrate made of FR-4 material, which has a thickness of 1.6 mm, with a loss tangent of 0.002 and permittivity of 4.4. The simulated and experimental findings indicate that the antenna exhibits favourable levels of isolation, ranging from −20 dB to −22 dB. The designed antenna maintains an Envelope Correlation Coefficient (ECC) below 0.02 and a Diversity Gain (DG) approaching 10 dB across its entire operational bandwidth. The suggested antenna utilizes a Perfect Electric Conductor (PEC) as a reflector in order to enhance the gain and mitigate the Specific Absorption Rate (SAR) of the MIMO antenna system. The incorporation of a PEC reflector in the MIMO antenna significantly reduces the SAR value for 10 g of tissue from 6.93 W/kg to 0.0255 W/kg.

This article explores 3D-printed horn-integrated MIMO Dielectric Resonator Antennas (DRAs) designed specifically for CubeSats. Traditional manufacturing methods struggle to create complex and customized DRAs. However, 3D printing offers a revolutionary approach, enabling the development of intricate, optimized DRA configurations even in miniaturized sizes. Notably, the 3D printing material utilized in this design is Polylactic Acid (PLA), a biodegradable material that contributes to reducing electronic waste (e-waste) in space. The proposed design boasts an impressive bandwidth exceeding 6 GHz (11.42 GHz–17.52 GHz) with an |S 11 | below −10 dB. It achieves a maximum gain of 12.4 dBi and a maximum directivity of 15.4 dBi. Furthermore, the Envelope Correlation Coefficient (ECC) remains remarkably low, at less than 0.06. These attributes make this MIMO antenna ideal for advanced communication systems and MIMO-enabled applications, particularly within the realm of CubeSat technology.

Enormous growth in wireless communication has led its applicability in various scenarios. One among them is the wireless based on-/off body communication. Achieving this requires compact and efficient antennas for wireless data transfer. To meet this requirement, a low profile Ultra Wideband (UWB) antenna is reported in this work. The antenna’s dimension is 35 × 45 × 0.8 mm 3 which is designed using a semi flexible Rogers 5,880 substrate. Using partial ground and asymmetric feed techniques, an ultra-wide bandwidth of 10 GHz (3–13 GHz) is achieved with a good peak gain of 6.7 dB, while the efficiency ranging from 80 % to 92 % in the UWB spectrum. A novel approach of conjointly connecting the Artificial Magnetic Conductor (AMC) structures is followed to achieve desired reflection response. AMC structures are deployed to achieve directional radiation pattern at 5.8 GHz to support off body communication, while concentric ring slots and partial ground plane enable Omni-directional pattern at 2.45 GHz which supports on body communication. On body measurements on various body parts and real time measurements under wet conditions are carried out. 0.654 and 0.327 W/kg of Specific Absorption Rate (SAR), at 2.45 and 5.8 GHz respectively, confirms minimum radiation hazards. The path loss of the antenna was analyzed for free space, on body and off body scenarios and were found to be considerably minimum. Similar scenarios were used to analyze group delay and minimum variation in group delay (<1.5 ns) is witnessed. The pulse similarity has been analyzed using fidelity factor and the values obtained satisfy the required standard values. The obtained results are predominant compared to the ones in the literature with good compatibility between simulated and measured results.

This paper presents the design of a rectangular patch antenna with compound reconfigurability in terms of operating frequency and radiation pattern using only four PIN diodes. Two PIN diodes namely, PD1 and PD2, are implanted on a rectangular slot of the driven patch for frequency reconfiguration. While other two PIN diodes PD3 and PD4, are uniquely arranged with shorting posts between parasitic elements and ground, perform the pattern reconfiguration operation. Switching of PD1 and PD2 changes the effective electrical length of driven patch for four different measured resonant frequencies at 3.35, 4.02, 4.12 and 5.12 GHz. Moreover, ON/OFF states of PD3 and PD4 alter the function of parasitic elements between director and reflector to achieve H-plane pattern reconfiguration in all reconfigurable operating frequencies. Measured tilt angles at 3.35, 4.02, 4.12 and 5.12 GHz bands are (−40°, 0°) (+30°, −42°, 0°) (+40°, −40°, 0°) and (+36°, −43°) respectively. Measured results of reflection coefficient and radiation pattern are in good agreement with the simulated results, which validates the frequency and pattern reconfigurable performances of the antenna. The proposed antenna can be used for various C band wireless applications such as sub-6-GHz 5G (3.3 GHz, 4 GHz), and WLAN (5.2 GHz).

A novel effective technique for improving the decoupling among antenna elements in four port MIMO is metamaterial based absorber wall is investigated and presented in this paper. The proposed work includes a quad port MIMO (Multiple Input Multiple Output) antenna for vehicle-to-vehicle (V2V) communication under Sub 6 GHz range. The mutual coupling in MIMO is mitigated by three different techniques: Combline filter, integrated horizontal and vertical absorber walls and patch with meander line technology. The designed antenna has two layer substrates which are coupled by a coaxial feed technique, with dimensions of 75*75*1.6 mm 3 . By using a combline filter in between the ground of nearby circular patches, the mutual connection between them is lessened. Furthermore, the use of integrated horizontal and vertical absorber walls greatly reduces the radiation interference between adjacent antennas. To find out how flexible the antenna is, parametric experiments are conducted. The findings indicate that the peak gain exceeds 6 dB and the return S11 is less than −19 dB. Furthermore, the suggested 2 × 2 MIMO antenna has an observed diversity gain of 6.42 dB, an Envelop Correlation Coefficient of below than 0.002 and a good isolation was observed between antenna units is of −45.92 dB. The proposed antenna best suited applicant for sub-6GHz applications.

A circular to linear polarization conversion of microstrip patch antenna using miniature multilayer graphene (MLG) pads is proposed in this article. The antenna consists of a circular radiating patch fed with 90° Branch Line Coupler (BLC) making it circularly polarized. The tiny graphene nano pads are placed on either side of the BLC in a way that one end of graphene pad touches the BLC, and the other is shorted to ground. The resistance of the graphene pads varies from 250 Ω to 54 Ω by applying variable voltage (0 V−6 V). This voltage bias makes the graphene pads conductive and attenuates the power in one of the arms of BLC and thereby converting antenna from circular to linearly polarized mode. The antenna is designed to operate at center frequency 3.3 GHz having operational bandwidth of 420 MHz (3.13 GHz–3.55 GHz), axial ratio (AR) bandwidth of 288 MHz (3.255 GHz−3.543 GHz). By varying the bias, the axial ratio in this band can be tuned from < 3 dB to > 5 dB. The measured results are in good agreement with simulated and the proposed antenna can be used for C band wireless applications.

A method for estimating signal and noise subspaces in the context of direction of arrival (DOA) for coherent wideband orthogonal frequency-division multiplexing (OFDM) signals is proposed. It relies on a newly defined matrix, which leverages the orthogonality property of OFDM subcarriers. We mathematically demonstrate that this matrix satisfies adequate subspace decomposition by considering two approximations. Furthermore, through DOA estimation evaluations, we confirm its effectiveness in discerning DOAs even with reduced snapshots and a low signal-to-noise ratio. To validate its feasibility and effectiveness, practical experiments are conducted using a real-world testbed based on USRP-B210 boards, and the results demonstrate the method’s effectiveness.

This work presents performance analysis of dual-band bandpass filter using substrate integrated waveguide technology. It includes two prototypes; featuring a dual-cavity working as dual-mode resonator and slot perturbation for creation of passbands. Design 1 and design 2 work on center frequencies of 7.35 GHz, 11.4 GHz and 7.3 GHz, 11.36 GHz respectively. The filter exhibits excellent performance in terms of measured in-band return loss of greater than 16 dB for both passbands and insertion loss of 0.96 dB and 1.63 dB for design 1. Design 2 has measured return loss of greater than 17 dB for both passbands and insertion loss of 0.98 dB and 1.92 dB, ensuring minimum losses. Additionally, simulation is performed using HFSS software for analysis of insertion loss, return loss, unloaded quality factor and group delay characteristics. The single layer filter is fabricated over RT Duroid 5,880 with ε r value of 2.2 as substrate. Parametric analysis is performed to explore the optimum values of physical dimensions to ensure impressive Q factor and coupling in the design. The proposed design utilizes a multimode resonator and is miniaturized to provide a robust solution in specific microwave circuit designs and enables independent tuning of passbands to increase design flexibility.

This paper combines cuckoo search (CS) with ExtraTrees for the first time searching for the optimal hyperparameters and proposes the CS-ExtraTrees model. Based on the parasitic feeding behavior of cuckoo birds and the principle of Lévy flight enhancing random flying ability, CS can effectively search for the optimal parameters on a global scale. To verify the effectiveness of the CS-ExtraTrees model proposed in this paper, the CS-ExtraTrees model was used to model the measured data of the 2.5 GHz gallium nitride (GaN) power amplifier (PA). Compared with gradient boosting, random forest, and ExtraTrees, the CS-ExtraTrees proposed in this paper can significantly improve the modeling accuracy and modeling speed.