Compact Size Research Articles

A Low-Profile four-port MIMO Antenna for 5G-n79 Band with high diversity performance

This paper presents a simple design of a compact 4-port multiple-input multiple-output (MIMO) microstrip antenna using polarization diversity technique. The proposed structure consists of four monopole elements operating in the fifth generation n79 band (4800–5000 MHz). To achieve good performance with a more compact design, the four identical elements are arranged orthogonally to each other. The proposed antenna is fabricated using a Rogers RT6010 substrate with a compact size of 28 × 28mm2. The measured results of the manufactured antenna in terms of S-parameters and radiation pattern are in good agreement at the operating frequency band. Moreover, the diversity performance of the proposed MIMO antenna is evaluated through the envelope correlation coefficient (ECC), the diversity gain (DG), the total active reflection coefficient (TARC) and the channel capacity loss (CCL).

Lake Environmental Data Harvester (LED) for Alpine Lake Monitoring with Autonomous Surface Vehicles (ASVs)

This article introduces the Lake Environmental Data Harvester (LED) System, a robotic platform designed for the development of an innovative solution for monitoring remote alpine lakes. LED is intended as the first step in creating portable robotic tools that are lightweight, cost-effective, and highly reliable for monitoring remote water bodies. The LED system is based on the Shallow-Water Autonomous Multipurpose Platform (SWAMP), a groundbreaking Autonomous Surface Vehicle (ASV) originally designed for monitoring wetlands. The objective of LED is to achieve the comprehensive monitoring of remote lakes by outfitting the SWAMP with a suite of sensors, integrating an IoT infrastructure, and adhering to FAIR principles for structured data management. SWAMP’s modular design and open architecture facilitate the easy integration of payloads, while its compact size and construction with a reduced weight ensure portability. Equipped with four azimuth thrusters and a flexible hull structure, SWAMP offers a high degree of maneuverability and position-keeping ability for precise surveys in the shallow waters that are typical of remote lakes. In this project, SWAMP was equipped with a suite of sensors, including a single-beam dual-frequency echosounder, water-quality sensors, a winch for sensor deployment, and AirQino, a low-cost air quality analysis system, along with an RTK-GNSS (Global Navigation Satellite System) receiver for precise positioning. Utilizing commercial off-the-shelf (COTS) components, a Multipurpose Data-Acquisition System forms the basis for an Internet of Things (IoT) infrastructure, enabling data acquisition, storage, and long-range communication. This data-centric system design ensures that acquired variables from both sensors and the robotic platform are structured and managed according to the FAIR principles.

A Novel Proposal of an Electro-Optical Sensor to Measure Various Levels of an Electric Field Using Pockels Effect Photonic Crystals

Electro-optic sensors based on the Pockels effect are key components for optical instrumentation due to their speed and accuracy. In this work, we propose a new electro-optic platform using two-dimensional photonic crystals of gallium arsenide and barium titanate (GaAs-BTO). This structure allows for the measurement of various electric field levels, from 0 kV/mm to 50 kV/mm, with a very high sensitivity and a compact size. The opto-geometric parameters of this sensor were chosen, optimized, and analyzed numerically using the Plane Wave Expansion (PWE) and Finite-Difference Time-Domain (FDTD) methods.

35‐2: Multispectral Pancharatnam‐Berry Phase Liquid Crystal Lens and Its Aplication in AR Displays

Pancharatnam‐Berry (PB) phase liquid crystal (LC) lenses show attractive benefits in optical systems because of their high efficiency, compact size and polarization‐dependent behavior. However, as a kind of diffraction‐based devices, PB LC lenses suffer from chromatic dispersion, which limits their applications in multi‐wavelength imaging systems. In this paper, we demonstrate a multispectral PB LC lens design to overcome this issue. An active multispectral PB LC lens has been fabricated and characterized. It can focus different wavelengths at the same distance so they are expected to solve the chromatic dispersion problem in the multi‐wavelength display system and other broadband optical systems.

High-performance MTM inspired two-port MIMO antenna structure for 5G/IoT applications

Abstract This study thoroughly investigates a two-port multiple-input multiple-output (MIMO) antenna system tailored for 5G operation at 28 GHz. The proposed antenna is patched on a Rogers (RT5880) substrate with a relative permittivity of 2.2 and total size of 20×12×0.508 mm3. The mutual relationship between the radiating patches is refined using an H-shaped metamaterial structure to reduce the isolation to –55 dB. A MIMO configuration with attractive features is employed to reduce the envelope correlation coefficient (ECC) to about 0.00062 and the channel capacity loss (CCL) to about 0.006 bits/sec/Hz, while magnify the gain to about 9.39 dBi and the diversity gain (DG) to about 9.995. Additionally, it boasts a compact size with stable radiation pattern. The simulations of the MIMO antenna are executed using CST microwave studio, subsequently validated with Advanced Design System (ADS) for an equivalent circuit model, then measured using Vector Network Analyzer. Discrepancies between measured and simulated results were analyzed, with observed variations attributed to cable losses and manufacturing tolerances. Despite these challenges, a comprehensive comparison with prior research highlights the notable advantages of the proposed design, positioning it as a compelling solution for 5G applications.

A compact broadband RF rectifier using two‐stage microstrip lines

AbstractThis paper simulates and measures a compact broadband rectifier for voltage doubler Schottky diode. Among them, a two‐stage microstrip line impedance matching network for voltage doubling circuits is used. The imaginary part of the diode impedance is limited by the short‐circuit branch. The impedance conversion transmission line matches the impedance to 50 Ω. The impedance matching in the circuit is only realized by two‐stage microstrip lines, which reduces the physical size of the rectifier and makes the rectifier more compact. Judging the measurement results from 0.8 to 2.5 GHz, the conversion efficiency is greater than 30% at 0 dBm, the bandwidth is 103%, and the maximum conversion efficiency reaches 66.3% at 8 dBm. In addition, the compact size of the rectifier is 23 × 20 mm2.

A lightweight CNN model for pepper leaf disease recognition in a human palm background

The identification of pepper leaf diseases is crucial for ensuring the safety and quality of pepper yield. However, existing methods heavily rely on manual diagnosis, resulting in inefficiencies and inaccuracies. In this study, we propose a lightweight convolutional neural network (CNN) model for recognizing pepper leaf diseases and subsequently develop an application based on this model. To begin with, we acquired various images depicting healthy leaves as well as leaves affected by viral diseases, brown spots, and leaf mold. It is noteworthy that these images were captured against a background of human palms, which is commonly encountered in field conditions. The proposed CNN model adopts the GGM-VGG16 architecture, incorporating Ghost modules, global average pooling, and multi-scale convolution. Following training with the collected image dataset, the model was deployed on a mobile terminal, where an application for pepper leaf disease recognition was developed using Android Studio. Experimental results indicate that the proposed model achieved 100 % accuracy on images with a human palm background, while also demonstrating satisfactory performance on images with other backgrounds, achieving an accuracy of 87.38 %. Furthermore, the developed application has a compact size of only 12.84 MB and exhibits robust performance in recognizing pepper leaf diseases.

A novel slotted antenna design for future Terahertz applications

A slotted patch antenna operating at 118 GHz is proposed to address challenges in the terahertz (THz) frequency band for wireless communication systems. The antenna design, utilizing a Rogers RO3003 substrate, which has a dielectric constant of 3 and tan 0.001, strategically incorporates slots to enhance key performance parameters. Copper is employed for the ground and radiating patch, and a microstrip feeding method powers the antenna. High frequency structure simulator (HFSS) software is used for design and simulation, revealing resonance at 0.118 THz with a reflection coefficient of -42.41 dB and an impedance bandwidth of 4.42 GHz (115.84–120.26 GHz). At the operating frequency, the antenna exhibits a gain of 7.36 dB, maximum directivity of 7.38 dB, the voltage standing wave ratio (VSWR) of 1.01, and 99.75% radiation efficiency, all within a compact size of 1.5×1.3×0.1 mm³. The suggested antenna outperforms recent counterparts, making it suitable for applications like security screening and wireless communication systems (5G). Future efforts will target bandwidth expansion, gain enhancement, and further size reduction to enhance overall performance.

Design of Compact Size Tri-Band Stacked Patch Antenna for GPS and IRNSS

Design of Compact Size Tri-Band Stacked Patch Antenna for GPS and IRNSS

Design of Compact Size Tri-Band Stacked Patch Antenna for GPS and IRNSS

Abstract: This paper introduces a low-profile, compact tri-band microstrip patch antenna designed for GPS and IRNSS applications. The proposed antenna operates at frequencies of 1.57 GHz, 1.22 GHz, and 1.77 GHz. The antenna configuration consists of a patch antenna with a slip slot or manderline to generate three frequency bands while maintaining an acceptable radiation pattern. The focus of the study is to enhance the antenna's gain across all three frequency bands. This design aims to offer a versatile solution for navigation systems, leveraging the tri-band capability to accommodate different satellite signals and improve overall performance in GPS and IRNSS applications.

A Single-Clamp Inchworm Actuator with Two Piezoelectric Stacks.

Inchworm piezoelectric actuators have attracted much attention in the field of precision positioning due to the advantages of a large stroke, high output force, and high resolution. However, traditional inchworm piezoelectric actuators use two sets of clamps and a set of drive structures to achieve stepping motion, which generally requires at least three piezoelectric stacks, resulting in a complex structure and the control system. Several methodologies have been advanced to minimize the utilization of piezoelectric stacks. However, there still exists the issue of excessive volume. Therefore, an inchworm piezoelectric actuator with a single-clamp and single drive structure is proposed in the study, which provides a compact size and smaller volume. The clamping mechanism comprises two sets of clamping feet with opposite displacement, which alternate contact with the guide frame and adjustable plate to ensure that the clamping mechanism always has frictional force and accomplishes the stepping motion. The testing of the actuator's step distance, output force, and other parameters was conducted utilizing a displacement sensor. Experimental results indicate that the actuator achieved a maximum speed of 174.3 μm/s and an output force of 8.6 N when the frequency and voltage were 19 Hz and 150 V.

High performance few-mode fiber-based light field direction sensing system using deep convolutional neural network: fiber speckle demodulation network (FSDNET)

Precisely sensing the light field direction information plays the essential role in the fields of three-dimensional (3D) imaging, light field sensing, target positioning and tracking, remote sensing, etc. It is thrilling to find that the optical fiber can be used as a sensing component due to its high sensitivity, compact size, and strong resistance to electromagnetic interference. According to the core principle that the few-mode fiber output speckle pattern is sensitive to the change of incident light field direction, the variation characteristics is further investigated in this research study. Based on the simulation and analysis of the fiber transmission characteristics, the output speckle corresponding to the incident light field with the direction in the range of ±6° horizontally and vertically are calculated. Furthermore, a deep convolutional neural network (CNN): fiber speckle demodulation network (FSDNET) is proposed and constructed to establish what we believe to be a novel way to reveal and identify the mapping relationship between the light field direction and the output speckle. The theoretical simulation shows that the mean absolute error (MAE) between the perceived light field directions and the true directions is 0.01°. Then, a light field direction sensing system based on the few-mode fiber is developed. Regarding to the performance of the sensing system, the MAE of the FSDNET for the light field directions that have appeared in the training set is 0.0389°, and for testing set of the unknown directions that have not appeared in the training set, the MAE is 0.0570°. Therefore, the simulation and experimental results prove that high performance sensing of light field direction can be achieved by the proposed few-mode fiber sensing system and the FSDNET.

Modeling and performance enhancement of compact FSS based low‐profile broadband monopole antenna

SummaryIn this research work, a compact‐sized offset‐fed broadband monopole antenna is designed using a frequency selective surface (FSS) reflector to enhance gain, radiation efficiency, and FBR and validated experimentally. The designed antenna consists of a triple v‐slit on a rectangular‐shaped radiating patch, a modified partial ground, and a frequency‐selective surface (FSS). It exhibits a ‐10 dB impedance bandwidth of 9.37 GHz (6.55–15.92 GHz) and a fractional bandwidth of 83.4%, yielding significant portions of the C‐band (4–8 GHz), the X‐band (8 GHz–12 GHz), and covering a considerable part of the Ku‐band (12–18 GHz). The proposed prototype equivalent circuit model has been developed progressively to validate the electromagnetic simulation results. The measured peak gain is 14.25 dBi (6.8 dBi without FSS) at 14.2 GHz with an average radiation efficiency of ≥ 96% for the FSS integrated antenna. Furthermore, the proposed design improves the front‐to‐back ratio (FBR) by 15 dB throughout the broadband frequency range. The proposed antenna peak gain, reflection coefficient (S11), radiation efficiency, and radiation patterns show adequate similarity between the tested and simulated results and have numerous advantages, including very compact size, simple structure, minimum S11 (dB), high gain, and broadband capability.

Broadband spin and angle co-multiplexed waveguide-based metasurface for six-channel crosstalk-free holographic projection

Metasurface-based holograms, or metaholograms, offer unique advantages including enhanced imaging quality, expanded field of view, compact system size, and broad operational bandwidth. Multi-channel metaholograms, capable of switching between multiple projected images based on the properties of illuminating light such as state of polarization and angle of incidence, have emerged as a promising solution for realizing switchable and dynamic holographic displays. Yet, existing designs typically grapple with challenges such as limited multiplexing channels and unwanted crosstalk, which severely constrain their practical use. Here, we present a new type of waveguide-based multi-channel metaholograms, which support six independent and fully crosstalk-free holographic display channels, simultaneously multiplexed by the spin and angle of guided incident light within the glass waveguide. We employ a k-space translation strategy that allows each of the six distinct target images to be selectively translated from evanescent-wave region to the center of propagation-wave region and projected into free space without crosstalk, when the metahologram is under illumination of a guided light with specific spin and azimuthal angle. In addition, by tailoring the encoded target images, we implement a three-channel polarization-independent metahologram and a two-channel full-color (RGB) metahologram. Moreover, the number of multiplexing channels can be further increased by expanding the k-space’s central-period region or combing the k-space translation strategy with other multiplexing techniques such as orbital angular momentum multiplexing. Our work provides a novel approach towards realization of high-performance and compact holographic optical elements with substantial information capacity, opening avenues for applications in AR/VR displays, image encryption, and information storage.

Radiation Pattern Reconfigurable Arch-Shaped Dual-Band Antenna for Wi-Fi and WLAN Applications

This paper describes the design and analysis of a reconfigurable radiation pattern dual-band antenna for Wi-Fi and WLAN applications. The antenna patch comprises two parts: the upper part, which consists of three symmetrical oval rings, and the lower part, which is shaped like a lotus flower. By controlling the ON and OFF states of lumped p-i-n switches to control the direction of the radiation beams, the proposed pattern reconfigurable antenna achieves three reconfigurable states. The beam's direction change is performed by two switches that are connected in the gap between the feedline and the arch. The proposed antenna operates at 2.4 and 5.5 GHz, covering the bands from 2.1882 to 2.55 GHz and from 5.31 to 5.96 GHz, respectively. Additionally, the directivity over the working bands is about 1.92 to 4 dBi while the gain lies in the range of 1.66 to 3.5 dB. Moreover, the voltage standing wave ratio (VSWR) varies from 1 to 1.20. The size of the antenna is 47×59.5 mm2 which is printed on a 1.6 mm thickness FR-4 substrate of 4.4 relative permittivity. Computer simulation technology Microwave Studio is used to design and study the recommended constructions. The proposed design achieves an acceptable value of VSWR, stable gain, and good directivity, which makes it a suitable choice for future radiation pattern reconfiguration applications. The proposed antenna is distinguished by a simple shape, compact size, respectable return loss, good radiation characteristics, and high efficiency. The obtained results from measurements are quite close to the simulations.

Boosting the sensitivity of single photon ionization time-of-flight mass spectrometry using a segmented focus quadrupole-ion guide

Single photon ionization time-of-flight mass spectrometry (SPI-TOF-MS) is a powerful analytical technique for real-time detection of trace VOCs. However, efficient ion transmission within the ionization chamber has always been a challenging issue in SPI-TOF-MS. In this study, a novel ion guide termed the Segmented Focus Quadrupole Ion Guide (SFQ-IG) was introduced for SPI-TOF-MS. The SFQ-IG device consists of 12 printed circuit boards (PCB), each containing four quarter-ring electrodes with inner diameters progressively decreasing from 26 to 4 mm. The simulation results demonstrated that SFQ-IG exhibited superior ion transmission efficiency than both ion funnel (IF) field and direct current-only (DC-only) field. By integrating into a SPI-TOF-MS, this ion guide was optimized in terms of the ionization source pressure, direct current gradient, and radio frequency amplitude. Further comparative experiments demonstrated that the SPI-TOF-MS with the SFQ-IG exhibited higher sensitivity than both the IF field (1.3–7.4 times) and DC-only field (3.5–8.8 times) for the test VOCs. The improvements in limit of detection (LOD) with the SFQ-IG ranged from 1.6 to 5.3 times compared to the DC-only field for the test VOCs. Fabricated using PCB technology, the SFQ-IG is characterized by its cost-effectiveness, compact size, and high transmission efficiency, facilitating its integration into other mass spectrometers.

High-efficiency single-layer corporate-feed gap waveguide based circularly polarized antenna array with compact size

A high-efficiency, single-layer gap waveguide based circularly polarized (CP) metasurface (MTS) antenna array has been proposed at Ka-band, employing a combination of printed circuit board (PCB) and machining techniques. The coupling slot parallel to the feeding ridge is proposed, which can be beneficial for designing single-layer ridge gap waveguide (RGW) networks, avoiding the traditional cavity layer and reducing the transmission loss. The MTS elements in a 4 × 4 lattice of truncated-corner patches are etched on a single substrate layer for lightweight and low-cost, validating the concept of a compact mixed design that can be easily adapted to other printed CP antennas. A 4 × 4 MTS array prototype was fabricated and tested. The impedance bandwidth and axial ratio bandwidth are 26–31.3 GHz (18.5%) and 28.2–33 GHz (15.7%), respectively. Over the entire operating bandwidth of 28.2–31.3 GHz (10.4%), antenna radiation efficiency exceeds 82%, and the maximum realized gain at 29.2 GHz is 21.2 dBi. The designed broadband MTS antenna array is efficient, compact, and suitable for certain millimeter-wave communication applications.

An efficient self-powered piezoelectric energy extraction scheme with cascaded-gyrators-based transformer

The enhancement of power transfer from the piezoelectric transducer to the load with a compact size is explored in this paper. Large physical inductors are no more required to create resonance in piezoelectric energy harvesting schemes while applying the proposed gyrator-induced double resonance (GI-DR) technique. Hence, the proposed circuit is cost-effective and provide improved performance along with reduced-space benefits in integrated circuits (IC) package for wireless sensor nodes (WSN) and Internet-of-Things (IoT) applications. Two cascaded gyrators are used in place of a transformer in the proposed circuit. The required phasor response for resonance is acquired by the gyrators' voltage-current (V–I) relationship. Regarding the final charging voltage, the proposed circuit with a storage capacitor of 1000 mF can obtain 763.46 % and 14.77 % improved performance than other synchronous circuits like SEH and DSSH respectively. The proposed technique can also be applied to similar piezoelectric energy harvesting strategies with large inductors to create resonance.

High-power electrically pumped terahertz topological laser based on a surface metallic Dirac-vortex cavity

Topological lasers (TLs) have attracted widespread attention due to their mode robustness against perturbations or defects. Among them, electrically pumped TLs have gained extensive research interest due to their advantages of compact size and easy integration. Nevertheless, limited studies on electrically pumped TLs have been reported in the terahertz (THz) and telecom wavelength ranges with relatively low output powers, causing a wide gap between practical applications. Here, we introduce a surface metallic Dirac-vortex cavity (SMDC) design to solve the difficulty of increasing power for electrically pumped TLs in the THz spectral range. Due to the strong coupling between the SMDC and the active region, robust 2D topological defect lasing modes are obtained. More importantly, enough gain and large radiative efficiency provided by the SMDC bring in the increase of the output power to a maximum peak power of 150 mW which demonstrates the practical application potential of electrically pumped TLs.

Citrus Pest Identification Model Based on Improved ShuffleNet

To address the current issues of complex structures and low accuracies in citrus pest identification models, a lightweight pest identification model was proposed. First, a parameterized linear rectification function was introduced to avoid neuronal death. Second, the model’s attention to pest characteristics was improved by incorporating an improved mixed attention mechanism. Subsequently, the network structure of the original model was adjusted to reduce architectural complexity. Finally, by employing transfer learning, an SCHNet model was developed. The experimental results indicated that the proposed model achieved an accuracy rate of 94.48% with a compact size of 3.84 MB. Compared to the original ShuffleNet V2 network, the SCHNet model showed a 3.12% accuracy improvement while reducing the model size by 22.7%. The SCHNet model exhibited an excellent classification performance for citrus pest identification, enabling the accurate identification of citrus pests.