This paper presents a novel circularly polarized microstrip antenna system for non-invasive detection of moisture in wood, enabling early identification of arthropod infestation areas before structural damage occurs. The proposed system consists of two microstrip antennas with opposite polarization directions (LHCP/RHCP) for transmission and reception. The circular polarization direction difference between the transmitter and the receiver allows long distance measurement and ensures low coupling between the antennas; thus, high isolation is maintained when no moisture is present. Moisture presence alters this condition, increasing the received power by 12.5 dB. The antenna system is fabricated on a low-cost FR4 substrate with compact dimensions of 50mm × 50mm × 1.6mm and operates at 2GHz. Comprehensive simulations and experiments demonstrate reliable operation across multiple conditions, including moisture levels (0-100%), temperature (- 20°C to 90°C), antenna positioning, wood type (Pine, Douglas fir, and Oak), sample thickness (20-30mm), and subsurface moisture depth (up to 20mm). A prototype was then fabricated, and experimental repeated measurements confirmed high repeatability, with a standard deviation [Formula: see text] 0.7 dB. Calibration analysis yields an average sensitivity of 0.109 dB/%MC. These results indicate that the proposed system is suitable for wood-protective moisture-sensing applications.

Designing compact, high-gain antennas at 400 MHz is challenging due to large size, narrow bandwidth, and low efficiency. This work proposes an interaction-driven Artificial Magnetic Conductor-Defected Ground Structure (AMC-DGS) microstrip antenna for subsurface communication. The design exploits electromagnetic interaction between the slot-type DGS, radiating patch, and AMC surface with spacer layer for performance enhancement. The DGS functions not only for impedance tuning or to attain polarization purity but also as an active radiator, enabling current redistribution and higher order mode perturbation. This interaction, combined with composite superposed mode (CSM) excitation and orthogonal slot radiation, achieves a 400 MHz band (379–419 MHz) with 10.2% bandwidth and 6.5 dBi peak gain. Additionally, a higher-order mode generates a second band at 700 MHz (700–714 MHz) with 2% bandwidth and 6.1 dBi gain. The antenna maintains stable broadside radiation with efficiencies of 98% and 70% at 400 MHz and 700 MHz, respectively. The proposed AMC-DGS antenna provides a compact, dual-band solution for subsurface sensing, Wireless Underground Sensor Networks (WUSN), Internet of Underground Things (IoUT), Ground Penetrating Radar (GPR), and other low-frequency communication systems.

Microwave bowtie-metasurfaces and their applications in miniaturized microstrip antennas

Design and performance evaluation of a miniaturized corner-truncated wearable microstrip antenna for non-invasive brain tumour detection

As essential radiating elements in RF and microwave microsystems, microstrip antennas require sufficient bandwidth to ensure stable operation, integration flexibility, and overall microsystem performance. From a microsystem optimization perspective, this paper proposes a bandwidth extension method for microstrip antennas that combines swarm intelligence and reinforcement learning. The proposed ICOA-TD3 framework is designed to enhance antenna bandwidth within target frequency bands and thus improve the performance robustness of compact RF microsystems. In the proposed method, an improved crayfish optimization algorithm (ICOA) is first used to explore the global design space and achieve global bandwidth enhancement, followed by the Twin Delayed Deep Deterministic Policy Gradient (TD3) algorithm for local refinement and further exploitation of the antenna structure’s bandwidth potential. In Experiment 1, the impedance bandwidth (S11≤−10dB) is increased by up to 200%. In Experiment 2, the impedance bandwidth (S11≤−10dB) and axial-ratio (AR) bandwidth (AR≤3dB) are improved by up to 27% and 250%, respectively. The results indicate that the proposed method is a feasible solution for bandwidth-oriented optimization of microstrip antennas and is promising for the intelligent design of high-performance RF microsystems.

HighlightsWhat are the main findings?A flexible microstrip antenna with beveled meandering and a partial ground plane broadens its bandwidth from 0.612–0.625 GHz to 0.346–2.0 GHz while shrinking its footprint to 75.3% of its original size.The improved whale optimization algorithm (I-WOA), which combines Sobol sequence initialization with Q-learning, efficiently optimizes the antenna’s structural parameters for simultaneous bandwidth maximization and size minimization.What are the implications of the main findings?The novel sensor overcomes the installation rigidity of conventional microstrip antennas by enabling non-invasive, broadband RF detection of partial discharges in both power transformers and cable joints.The practical advantage of a flexible substrate for curved equipment surfaces is evidenced by a 14% increase in response amplitude when the antenna is conformally wrapped around a cable joint.Partial discharge (PD) detection effectively identifies insulation defects in power equipment. Radio frequency (RF) methods for PD detection offer promising advantages due to their non-invasive measurement capability and ability to locate discharge sources. However, microstrip antennas used as RF sensors for PD detection suffer from narrow bandwidth and limited installation flexibility. To address these limitations, this paper presents a novel flexible microstrip antenna design. By incorporating a partial ground plane and oblique-cut meandering techniques and optimizing the structural parameters using an improved whale optimization algorithm (I-WOA), the operating bandwidth is expanded from 0.612–0.625 GHz to 0.346–2.0 GHz, while the overall size is reduced to 75.3% of its original dimensions. The antenna’s performance was validated through GTEM cell measurements and PD calibration pulse tests, confirming its suitability for RF detection of PD in power equipment such as transformers and cable joints. Notably, when the antenna was conformally wrapped around a cable joint, the response amplitude increased by 14%. This study contributes to the development of a low-cost, broadband, and flexibly installable RF sensor for partial discharge detection.

Aiming at the problems that existing detection methods struggle to accurately identify early insulation faults of induction motors, are susceptible to interference, and have poor installation adaptability, a non-intrusive detection method for early insulation faults of induction motors based on a microstrip antenna array is proposed. Relying on the low-loss electromagnetic wave transmission characteristic of the heat dissipation hole at the tail of the induction motor, a four-element microstrip antenna array with multiple narrow beams and dual detection frequencies is designed, with the detection frequencies accurately set at 1.14 GHz and 2.23 GHz, which effectively avoids the motor operation noise frequency band (≤300 MHz) and the strong interference frequency band of mobile base stations (900 MHz, 1.8 GHz, 2.4 GHz). Utilizing the high gain and strong directivity of the array antenna, the accurate extraction and amplification of weak electromagnetic wave signals from early insulation fault discharge penetrating through the heat dissipation hole are realized. The full-dimensional simulation design of the antenna array is completed by using HFSS electromagnetic simulation software, and an industrial-grade experimental platform is built to carry out multi-condition verification experiments. The results show that the proposed detection system can realize non-intrusive, non-stop, and non-disassembly identification of early insulation discharge faults in induction motors, with a fault recognition rate of 94% for single faults and 90% for composite faults, and the average signal-to-noise ratio reaches 31.6–35.2 dB. Even under strong industrial electromagnetic interference, the recognition rate remains above 85%. This method overcomes the problems of traditional methods such as severe noise interference, difficult installation, and inability to monitor online, providing a high-efficiency scheme for real-time insulation state monitoring of industrial induction motors with good engineering application value.

This paper presents a high-performance 4 × 1 dual-polarized square-ring patch antenna array operating in the Ku-band for Ground-Based Synthetic Aperture Radar (GB-SAR) applications, with a compact size of 90mm × 30mm. The proposed design achieves compact integration by implementing dual-port polarization on a single substrate, enabling significant size reduction while effectively controlling mutual coupling and suppressing surface-wave propagation. To further enhance isolation and radiation performance, metamaterial unit cells (MTMLs) are introduced between adjacent elements to mitigate surface waves, while strategically positioned metallic vias improve port isolation. The antenna exhibits a wide impedance bandwidth from 16.3 to 18.5GHz; however, the performance is specifically optimized within the 16.8-17GHz band of interest for GB-SAR applications, where it achieves mutual coupling below - 12.5 dB, radiation efficiency exceeding 93%, and ECC values below 0.006. A two-layers dielectric superstrate are incorporated to improve radiation characteristics, resulting in a peak gain of 12 dBi, sidelobe suppression of - 16.8 dB, and a half-power beamwidth of 38.3°. These additional layers enhance gain and beam focusing while also serving as a protective shield against harsh automotive environmental conditions such as temperature variations, vibration, moisture, and mechanical stress. This protective layer ensures mechanical durability and stable RF performance without compromising radiation efficiency. The antenna array is fabricated and experimentally validated, with measured results showing strong agreement with simulations. The proposed configuration provides a compact, low-loss, high-efficiency, and environmentally effective solution suitable for advanced Ku-band radar applications.

Annually 14.7% demand is increasing for IoT devices & Wireless technologies projecting a rise in market to $22.3 billion till 2030, thus efficient and compact antennas operating at Industrial Scientific and medical [ISM] Band are widely needed. Wireless technologies like Wi-Fi, Zigbee, and Bluetooth uses 2.4GHz ISM band. Microstrip patch antennas are most oftenly used in these technologies, Microstrip patch antennas have characteristics like simple structure, low profile and easy to integrate with microwave circuitry. Yet, conventional microstrip antennas have low bandwidth and comparatively less radiation efficiency. This research work present the analysis and design of Circular Slot-Loaded square ring microstrip patch antenna functioning at 2.4GHz. The designing of the antenna is made by FR-4 dielectric substrate and examined using ANSYS HFSS electromagnetic simulation software. The current distribution is modified by introducing a circular slot in square ring patch resulting in improved impedance matching. The simulation result signify a VSWR of 1.3, gain of 3 dB, return loss of -32.8dB and bandwidth ranging from 2.3GHz to 2.6GHz. The proposed antenna have a compact design while delivering improved performance making it right for IoT devices.

A Two-Diode Bandwidth-Reconfigurable Microstrip Antenna with Resonance Merging for 6G Mid-Band Systems

This paper describes the development of an integrated aircraft safety monitoring system that combines a multiband antenna configuration with a real-time sensing and communication framework. The proposed design utilizes four microstrip antennas operating at different frequency bands to support multiple aviation functions within a single platform. The antennas are initially designed at 1.81 GHz, 3.49 GHz, 4.55 GHz, and 7.55 GHz, while experimental measurements indicate resonances at 1.92 GHz, 3.52 GHz, 4.68 GHz, and 7.60 GHz, respectively. Both simulation and practical measurements are conducted to assess important antenna characteristics such as return loss, voltage standing wave ratio (VSWR), bandwidth, radiation efficiency, total efficiency, and gain. The observed results show close agreement between simulated and measured performance. Return loss values are consistently below −27 dB, and VSWR remains near unity, confirming effective impedance matching. The antennas demonstrate a wide bandwidth range from 48 MHz to 1427 MHz, allowing support for both narrowband and broadband applications. Radiation efficiency is maintained above 52% across all designs, reaching a peak value of 66.16%, while total efficiency improves up to 65.5% at higher operating frequencies. The gain results indicate stable radiation behavior suitable for airborne communication systems. To enhance system functionality, an embedded monitoring unit based on the ESP32 is integrated with multiple sensors for tracking parameters such as vibration, temperature, tilt, altitude, smoke levels, and position. The collected data is processed using a real-time decision mechanism to identify abnormal conditions. In such events, alerts are transmitted to a remote station through a GSM communication module, enabling prompt response. The complete system is implemented on a drone platform to validate its operational performance and integration capability. Experimental observations confirm that the proposed system ensures reliable communication, continuous monitoring, and timely alert generation. The overall approach provides a compact and efficient solution for improving aircraft safety and can be extended to next-generation aviation and unmanned aerial systems.

Design and analysis of an elliptical microstrip antenna with ground plane variations for ultrawideband applications

Continuous introduction of advanced optimization algorithms promotes the development of electromagnetic (EM) technology in radar and communication systems. Wideband antenna design within a given space and wideband array pattern synthesis, especially in the scenario of strong mutual coupling, are two typical challenging electromagnetic problems. In this paper, a nature-inspired algorithm, i.e., the water cycle algorithm (WCA), is introduced to resolve the above two EM problems. Two typical wideband antennas, i.e., the dual-band E-shaped microstrip antenna and the typical magnetoelectric (ME) dipole antenna, are designed on the basis of the established WCA-based antenna design scheme. Compared with the well-known algorithms that have been introduced in antenna design, including the differential evolution (DE) algorithm and the gray wolf optimizer (GWO), better results can be achieved with WCA. In the sequel, a WCA-based low peak sidelobe level (PSLL) pattern synthesis is implemented based on a uniformly spaced 27-element folded fractal ME dipole array antenna with mutual coupling as high as −10 dB, the results of which further validate the superiority of WCA in array pattern synthesis and demonstrate the value of this application innovation.

The surface-wave generation in microstrip antennas and reflectarray antennas composed of microstrip patches is an unavoidable phenomenon. The incidence of surface-waves on discontinuities and edges results in side-lobe generation and main beam declination. In this paper, the side-lobe production in reflectarrays is analyzed using the Fourier transform technique and aperture field estimation. In reflectarray antennas composed of graphene unit-cells, the side-lobe production is somewhat different from the metal ones due to the graphene intrinsic characteristics, such as Ohmic losses and kinetic inductance. In this paper, the impact of graphene Ohmic losses on the side-lobe reduction and directivity improvement is analyzed. A reflectarray composed of graphene cell-clusters is designed and simulated for the investigation of the generation of surface-waves and side-lobes in the far-field pattern, at 1 THz. And the impact of losses, on directivity improvement, have been examined for different reflection angles.

This article presents the designs of simple dual-slot L-shaped microstrip antennas with coaxial-feeding that require only two cuts of slot, operating at frequencies of 0.7 GHz, 2.1 GHz, and 3.5 GHz, which align with the fifth-generation (5G) new radio (NR) frequency bands n28, n1, and n78, respectively. These antennas are designed to support low- and mid-band 5G applications while accommodating demand for simple and low-profile designs. All rectangular microstrip antennas have been designed using a fundamental microstrip formula, followed by modifications to ensure optimal performance by integrating rectangular slots on the radiating patch and variably shaped slots on the ground plane to improve the reflection coefficient, S11, gain, and efficiency, with varying effects across frequencies. The proposed microstrip antennas yield S11 less than − 10 dB, approximately 2 dB gain, and efficiency surpassing 50%. Meanwhile, the validation measurements show a minimum S11 of − 18.7 dB at 0.7 GHz and a maximum gain of 2.4 dB at 3.5 GHz. All designs are simulated and analyzed in CST Microwave Studio using the Rogers RT/Duroid 5880 substrate, prior to the validation via a vector network analyzer and an anechoic chamber.

Abstract A microstrip patch antenna is a low-profile, lightweight antenna widely used in wireless communication systems. It consists of a radiating metallic patch on one side of a dielectric substrate and a ground plane on the other. These antennas are easy to fabricate and integrate with printed circuit boards. They are commonly used in mobile devices, satellite communication, and radar systems. This project proposes design and implementation of microstrip patch antenna using conventional methods there are some disadvantages such as narrow bandwidth, low gain, low efficiency etc. the proposed design can be optimized using Particle Swarm Optimization (PSO) To overcome these limitations, for wideband performance at 10.5 GHz. The optimization aims to enhance return loss, bandwidth, and gain, addressing the limitations of conventional microstrip antennas. The proposed antenna will show improved bandwidth, higher gain, and better return loss, making it suitable for X- band wireless Keywords: PSO Algorithm antenna design simulation, HFSS, wireless communication

I. ABSTRACT In this project, a dual-frequency microstrip antenna has been designed and simulated using ANSYS HFSS. The antenna structure is optimized to achieve miniaturization while maintaining efficient radiation performance across the desired frequency bands. Techniques such as geometry modification and loading elements (e.g., slots or PIN diodes) are employed to enable frequency reconfiguration and compact design. The proposed microstrip antenna is modeled and analyzed in HFSS, where important parameters such as return loss (S11), VSWR, bandwidth, radiation pattern, and gain are evaluated. Simulation results confirm that the antenna operates efficiently at the targeted frequencies, validating its suitability for dual band wireless communication applications. Furthermore, dual-frequency microstrip antennas are widely used in mobile communication, Wi-Fi, Bluetooth, WLAN, satellite links, and IoT systems, where compactness and multiband capability are essential. Their ability to combine small size, good efficiency, and dual-frequency operation makes them highly suitable for modern and next-generation wireless communication systems.

This paper presents the design and analysis of a wideband Substrate Integrated Waveguide (SIW) antenna for 5G applications operating in the millimeter-wave (mmWave) frequency range. The proposed antenna utilizes an aperture-coupled SIW feeding mechanism to achieve wide bandwidth, high gain, and low transmission loss. Compared to conventional microstrip antennas, the SIW structure offers improved efficiency, better impedance matching, and reduced radiation loss. The antenna is designed to support multiple 5G bands with stable radiation characteristics. Simulation results demonstrate enhanced bandwidth, high radiation efficiency, and reliable performance, making the proposed design suitable for next-generation wireless communication systems.

In order to solve the shortcomings of wireless passive sensors based on label chips for signal transmission, which cannot withstand high temperatures, and the problem of the short transmission distance of wireless passive sensors without chips, a wireless passive high-temperature frequency-doubling microstrip antenna sensor based on a high-temperature-resistant Schottky diode is proposed. The sensor utilizes the characteristic of the resonant frequency of the microstrip antenna changing with temperature. The high-temperature-resistant platinum sensitive structure integrated on alumina ceramic adapts to temperature measurement in harsh environments such as high temperatures, oxidation, and corrosion. A high-temperature-resistant Schottky diode was designed, and on this basis, a high-temperature-resistant frequency doubling circuit was designed and implemented. Through this circuit, the network analyzer can transmit a fundamental frequency signal and receive a modulated double frequency signal, while limiting ambient noise to the fundamental frequency band, eliminating interference, and significantly improving the signal-to-noise ratio, thereby enabling wireless transmission. In addition, a high-temperature-resistant, miniaturized broadband coplanar waveguide antenna was designed to replace the traditional horn antenna as the interrogation antenna, which realized the wireless transmission of sensor signals. A high-temperature testing system was set up to test the sensor performance in the range of 15–800 °C. The results showed that the maximum transmission distance of the sensor is 20 cm, and the transmission performance is best at 10 cm away from the interrogation antenna. It can accurately characterize the temperature during the heating process, with a sensitivity of up to 181 KHz/°C and a frequency error of no more than 0.2%.

The growing utilization of terahertz (THz) technology, particularly in biomedical fields, has heightened the need for multiband, high-gain THz antennas. To address this, a novel symmetric stub-loaded shaped microstrip antenna has been proposed with the integration of metamaterial, delivering enhanced gain performance, smooth operational characteristics, and support for multiple frequency bands. The silicon layer is used as a substrate layer for the proposed design with a dielectric constant value of 11.7 and the loss tangent value of 0.046 − 0.034 in addition to this the thickness of 100μm and a permittivity value of 2.25.The proposed antenna has a dimension of 38 × 38 × 100μm³ in its maximum configuration, which can be made by using parametric analysis and operating across 3.8 and 6.4 THz, which exhibit the return loss value of below 10 dB, having a bandwidth of 0.4 THz and 1 THz, respectively. The proposed antenna having simulated gain value of 9.2dBi and 8.9dBi across the resonating frequency. The results highlight the suggested antenna’s potential for security screening and adaptable biological THz applications. In addition to this, the design successively achieves isolation of -43 dB and − 37 dB across the operating frequency. On top of it, the proposed MIMO antenna has a mean effective gain value of 9.5 and 9.2 dB, a CCL (channel capacity loss) value of 0.01 and 0.018 (bps/Hz/s), and a DG (diversity gain) value of 9.2 and 9.5 dB across the operating frequency (3.8 and 6.4 THz).