Search Results (361)

Background: Pulsed radiofrequency (PRF) applied to the dorsal root ganglion (DRG) has been proposed as an effective neuromodulator treatment for persistent radicular pain. Autologous conditioned serum (ACS) therapy, derived from the patient’s own blood, offers a conservative approach. This study aims to evaluate the efficacy of ACS applied to the DRG as an adjunct in treating lower limb radicular pain (LLRP). Methods: A prospective, randomized, double-blind, placebo-controlled clinical trial was conducted comparing PRF combined with ACS versus PRF with physiological saline (PhS) on the DRG. Seventy patients (35 per group) with radicular pain lasting ≥ 6 months and refractory to previous treatments were enrolled. The primary outcome measure was the Numeric Pain Rating Scale (NPRS); secondary measures included the Oswestry Disability Index (ODI), Mood Assessment Scale (MOAS), SF-12 quality of life questionnaire, and DN4 neuropathic pain scale. Assessments occurred at baseline, 1 month, 3 months, 6 months, and 12 months post-intervention. Results: A total of 70 patients were included. The ACS group showed a significant reduction in pain compared to controls at 30 days (p < 0.05). Additionally, neuropathic symptoms such as tingling, numbness, stubbing, and burning decreased significantly in the ACS group during this period (p < 0.05). While both groups experienced pain reduction over time, no significant differences persisted at 6 months. No adverse effects were reported. Conclusions: The addition of ACS to PRF provides a short-term, statistically significant reduction in radicular pain at 30 days, suggesting it is a safe and effective adjunct therapy for lower limb radicular pain. Full article

In this paper, a miniaturized balanced bandpass filter with flexible input/output (I/O) functionality is initially designed based on parallel-coupled microstrip lines. Unlike conventional balanced bandpass filters, the proposed filter features two distinct I/O configurations. In these two states, the I/O ports of the developed balanced filter are symmetrically arranged in either horizontal or vertical directions. Moreover, the developed balanced filter demonstrates excellent differential-mode and common-mode suppression in both states. To further enhance the common-mode suppression without compromising the differential-mode performance, an asymmetrical quarter-wavelength open-circuited stub is introduced in the middle of the filter when the I/O ports are vertically symmetric. The inclusion of this stub significantly broadens the common-mode suppression bandwidth. More importantly, the developed balanced filters achieve highly compact sizes, which is essential for integration into modern compact RF front-end modules. To verify the feasibility of the proposed design concept, two prototypes are designed and fabricated, whose simulated and measured results are in good agreement. Full article

In this paper, a novel multi-mode resonator-based ultra-wideband bandpass filter topology is proposed, analyzed, and experimentally validated. The filter comprises a short shunt-stepped impedance resonator and shunt-open stubs. Thus, it can be easily implemented using microstrip technology, offering a simple and cost-effective alternative to multilayer and high-temperature superconductor thin-film-based bandpass filters. S-parameter expressions for the proposed filter are derived using even- and odd-mode methods. To validate theoretical results, a filter prototype operating at the center frequency ($f_o$) of 6.85 GHz is designed, fabricated, and experimentally tested. The measured 3 dB fractional bandwidth (FBW) of the filter exceeds 176%, and the selectivity factor (SF) reaches 0.87. Additionally, the filter outperforms most existing designs in the literature in terms of insertion loss (IL) and return loss (RL). Finally, a figure of merit (FoM) is proposed to measure the trade-off among key performance parameters (i.e., FBW, IL, RL, SF, $f_o$, and group delay flatness), and confirms that the proposed bandpass filter exhibits the best FoM compared to the state of the art. Full article

This paper presents a broadband omnidirectional rectenna combined with a solar cell for hybrid energy harvesting, addressing the daytime-only limitation of solar cells via complementary RF energy harvesting. To avoid mutual interaction in integration, the solar cell is placed above the antenna to receive light/EM waves from different directions. A broadband discone antenna ensures omnidirectional RF reception from 1.56 to 6.63 GHz, while a single-stub matching circuit and voltage doubler enable rectifier operation from 1.4 to 3.6 GHz, with over 50% power conversion efficiency at 5 dBm. The measurement demonstrates that the hybrid system can yield 20.25 mW from combined RF/solar power. This broadband hybrid energy harvesting system shows potential for powering sensors throughout the day by integrating two complementary energy sources with minimal interaction. Full article

Heat stress (HS), a pervasive environmental stressor, significantly disrupts systemic physiological homeostasis, posing substantial threats to human and animal health. Sheng Mai San (SMS), a classic Traditional Chinese Medicine (TCM) formula, exerts its therapeutic effects by replenishing qi (the vital energy governing physiological functions) and nourishing yin (the material basis responsible for moistening and cooling actions). This formula demonstrates significant efficacy in astringing sweating and preventing collapse. However, its precise molecular mechanisms against HS-induced myocardial injury remain incompletely elucidated. This study initially employed physicochemical analytical methods to determine the contents of total polysaccharides, saponins, and flavonoids in SMS and evaluated its antioxidant activity. Subsequently, both in vitro and in vivo rat models of HS were established to systematically assess the alterations in reactive oxygen species (ROS), antioxidant enzymes (GSH, SOD, CAT), and heat shock proteins (HSP70, HSP90) following SMS intervention, thereby investigating HS-induced myocardial injury and the protective effects of SMS. Furthermore, Western blot, immunofluorescence, and qRT-PCR techniques were utilized to quantitatively analyze key molecules in the Keap1-Nrf2-HO-1 and Stub1-HSF1 signaling pathways. The results demonstrated that total polysaccharides were the most concentrated in SMS, followed by total saponins. This formula exhibited potent free radical scavenging capacity against DPPH, ABTS, and OH⁻, along with significant reducing activity. HS-induced myocardial injury reached its peak severity at 6-12 h post-stress exposure. SMS intervention effectively suppressed excessive ROS generation, enhanced the activities of antioxidant enzymes (GSH, SOD, and CAT), and downregulated HSP70 and HSP90 mRNA expression levels, thereby significantly mitigating cardiomyocyte damage. Mechanistic investigations revealed that SMS conferred cardioprotection through dual modulation of the Keap1-Nrf2-HO-1 and Stub1-HSF1 signaling pathways. This study not only provides a novel TCM-based therapeutic strategy for preventing and treating HS-related cardiovascular disorders but also establishes a crucial theoretical foundation for further exploration of SMS’s pharmacological mechanisms and clinical applications. Full article

The rapid growth of low-power Internet of Things (IoT) applications has created an urgent demand for compact, battery-free power solutions. However, most existing RF energy harvesters rely on active rectifiers, multi-phase topologies, or complex tuning networks, which increase circuit complexity and static power overhead while struggling to maintain high efficiency under microwatt-level inputs. To address this challenge, this work proposes a harmonic-recycling, passive, RF-energy-harvesting system with integrated power management (HR-P-RFEH). The system adopts a planar microstrip architecture compatible with MEMS fabrication, integrating a dual-stage voltage multiplier rectifier (VMR) and a stub-based harmonic suppression–recycling network. The design was verified through combined electromagnetic/circuit co-simulations, PCB prototyping, and experimental measurements. Operating at 915 MHz under a 0 dBm input and a 2 k$\Omega$ load, the HR-P-RFEH achieves a stable 1.4 V DC output and a peak rectification efficiency of 70.7%. Compared with a conventional single-stage rectifier, it improves the output voltage by 22.5% and the efficiency by 16.4%. The rectified power is further regulated by a BQ25570-based unit to provide a stable 3.3 V supply buffered by a 47 mF supercapacitor, ensuring continuous operation under intermittent RF input. In comparison with the state of the art, the proposed fully passive, harmonic-recycling design achieves competitive efficiency without active bias or adaptive tuning while remaining MEMS- and LTCC-ready. These results highlight HR-P-RFEH as a scalable and fabrication-friendly building block for next-generation energy-autonomous IoT and MEMS systems. Full article

The rapid expansion of broadband wireless communication systems, including 5G, satellite networks, and next-generation IoT platforms, has created a strong demand for antenna architectures capable of real-time beam control, compact integration, and broad frequency coverage. Traditional reflectarrays, while effective for narrowband applications, often face inherent limitations such as fixed beam direction, high insertion loss, and complex phase-shifting networks, making them less viable for modern adaptive and reconfigurable systems. Addressing these challenges, this work presents a novel wideband planar metasurface that operates as a polarization rotation reflective metasurface (PRRM), combining 90° polarization conversion with 1-bit reconfigurable phase modulation. The metasurface employs a mirror-symmetric unit cell structure, incorporating a cross-shaped patch with fan-shaped stub loading and integrated PIN diodes, connected through vertical interconnect accesses (VIAs). This design enables stable binary phase control with minimal loss across a significantly wide frequency range. Full-wave electromagnetic simulations confirm that the proposed unit cell maintains consistent cross-polarized reflection performance and phase switching from 3.83 GHz to 15.06 GHz, achieving a remarkable fractional bandwidth of 118.89%. To verify its applicability, the full-wave simulation analysis of a 16 × 16 array was conducted, demonstrating dynamic two-dimensional beam steering up to ±60° and maintaining a 3 dB gain bandwidth of 55.3%. These results establish the metasurface’s suitability for advanced beamforming, making it a strong candidate for compact, electronically reconfigurable antennas in high-speed wireless communication, radar imaging, and sensing systems. Full article

A quad-channel diplexer is designed in this paper. The diplexer is composed of four stub-loaded step impedance resonators and a common feeder T-joint, which realizes four passbands with center frequencies of 2.6 GHz, 3.48 GHz, 4.8 GHz, and 6.3 GHz. The dual-band filter can be formed by coupling the stepped impedance resonator with the stub load, so two dual-band filters with good performance can be constructed. At the input and output end, a 0-degree feed is used to generate transmission zeros, which improves the high selectivity. When two dual-band filters are combined, a good impedance matching is obtained, and the |S₂₃| > 20 dB between the two dual-band filters achieves good isolation. The simulation results are consistent with the measured results. Full article

This work presents the use of a novel impedance coupling technique and electrical length increase by using stub loading placed from the radiator to the ground plane. This method is applied to the design of a small four-element ultrawideband (UWB) MIMO antenna arranged in axial symmetry to achieve a compact array size while obtaining a bandwidth starting from a very low cutoff frequency compared to a conventional radiator operating at the same frequency. The four-element MIMO antenna, with an operational bandwidth of 1.9 GHz to 30 GHz, is based on a wideband monopole with a semicircular geometry, fed by a coplanar structure and an L-shaped half-ground plane section. To increase the electrical length of the structure and achieve a compact antenna design, reactive stub loading is introduced, placing it on the backside of the substrate, located orthogonally between the radiator and the L-shaped ground plane, obtaining a small-sized configuration. The axial symmetry is employed to increase the antennas’ isolation by taking advantage of the orthogonal positioning and making the radiated fields have a low correlation. The antenna array footprint measures 48 mm × 48 mm, corresponding to 0.3λ₀ × 0.3λ₀ at the lower cutoff frequency. The array exhibits a low envelope correlation coefficient (ECC) of around 0.033 at 2 GHz, and less than 0.001 at the rest of the bandwidth; a diversity gain (DG) of approximately 10; a stable total active reflection coefficient (TARC) below −10 dB; interport isolation between 20 and 40 dB; and an average gain of 2.8 dBi. Full article

To reduce the carbon footprint of the concrete industry and promote a circular economy, this study explores the reuse of waste materials such as glass powder (GP) and nitrile rubber (NR) fibres in concrete. However, the inclusion of these waste materials results in lower compressive strength compared to conventional concrete, limiting their application to non-structural elements. To overcome this limitation, this study adopts the concept of confined concrete by developing concrete-filled steel tube (CFST) stub columns. In total, twelve concrete mix variations were developed, with and without steel tube confinement. GP was utilised at replacement levels of 10–30% by weight of cement, while NR fibres were introduced at 0.5% and 1% by volume of concrete. The findings demonstrate that the incorporation of GP and NR fibres leads to a reduction in compressive strength, with a compounded effect observed when both materials are combined. Steel confinement within CFST columns effectively mitigated the strength reductions, restoring up to 17% of the lost capacity and significantly improving ductility and energy absorption capacity. All CFST columns exhibited consistent local outward buckling failure mode, irrespective of the concrete mix variations. A comparison with predictions from existing design codes and empirical models revealed discrepancies, underscoring the need for refined design approaches for CFST columns incorporating sustainable concrete infill. This study contributes valuable insights into the development of eco-friendly, high-performance structural systems, highlighting the potential of CFST technology in facilitating the adoption of waste materials in the construction sector. Full article

This paper presents a symmetry-driven broadband circularly polarized magnetoelectric dipole antenna with bandpass filtering response, where the principle of symmetry is strategically employed to enhance both radiation and filtering performance. The antenna’s circular polarization is achieved through a symmetrical arrangement of two orthogonally placed metallic ME dipoles combined with a phase delay line, creating balanced current distributions for optimal CP characteristics. The design further incorporates symmetrical parasitic elements—a pair of identical inverted L-shaped metallic structures placed perpendicular to the ground plane at −45° relative to the ME dipoles—which introduce an additional CP resonance through their mirror-symmetric configuration, thereby significantly broadening the axial ratio bandwidth. The filtering functionality is realized through a combination of symmetrical modifications: grid slots etched in the metallic ground plane and an open-circuited stub loaded on the microstrip feed line work in tandem to create two radiation nulls in the upper stopband, while the inherent symmetrical properties of the ME dipoles naturally produce a radiation null in the lower stopband. This comprehensive symmetry-based approach results in a well-balanced bandpass filtering response across a wide operating bandwidth. Experimental validation through prototype measurement confirms the effectiveness of the symmetric design with compact dimensions of 0.96${\lambda }_0$ × 0.55${\lambda }_0$ × 0.17${\lambda }_0$ (${\lambda }_0$ is the wavelength at the lowest operating frequency), demonstrating an impedance bandwidth of 66.4% (2.87–5.05 GHz), an AR bandwidth of 31.9% (3.32–4.58 GHz), an average passband gain of 5.5 dBi, and out-of-band suppression levels of 11.5 dB and 26.8 dB at the lower and upper stopbands, respectively, along with good filtering performance characterized by a gain-suppression index (GSI) of 0.93 and radiation skirt index (RSI) of 0.58. The proposed antenna is suitable for satellite communication terminals requiring wide AR bandwidth and strong interference rejection in L/S-bands. Full article

This article presents the design and evaluation of a compact-sized antenna targeting heterogenous applications working in the C-band, 5G-sub-6GHz, and the ISM band. The antenna offers frequency reconfigurability along with multi-operational modes ranging from wideband to dual-band and tri-band. A compact-sized antenna is designed initially to cover a broad bandwidth that ranges from 4 GHz to 7 GHz. Afterwards, various multiband antennas are formed by loading various stubs. Finally, the wideband antenna along with multi-stub loaded antennas are combined to form a single antenna. Furthermore, PIN diodes are loaded between the main radiator and stubs to activate the stubs on demand, which consequently generates various operational modes. The last stage of the design is optimization, which helps in achieving the desired bandwidths. The optimized antenna works in the wideband mode covering the C-band, Wi-Fi 6E, and the ISM band. Meanwhile, the multiband modes offer the additional coverage of the LTE, LTE 4G, ISM lower band, and GSM band. The various performance parameters are studied and compared with measured results to show the performance stability of the proposed reconfigurable antenna. In addition, an in-depth literature review along with comparison with proposed antenna is performed to show its potential for targeted applications. The utilization of FR4 as a substrate of the antenna along with its compact size of 15 mm × 20 mm while having multiband and multi-mode frequency reconfigurability makes it a strong candidate for present as well as for future smart devices and electronics. Full article

The rapid development of 5G and next-generation wireless systems has increased the demand for antennas that support circular polarization (CP), wide frequency coverage, and a compact size. Achieving wideband CP performance in a low-profile and simple structure remains a key challenge for modern antenna designs. In response to this, this paper presents a compact wide-slot antenna with a single feed, offering a wide operational bandwidth and circularly polarized radiation. The proposed design is excited by a 50 Ohm microstrip feedline, and it is fabricated on an (54 × 50 × 1.6 mm³) FR4 dielectric substrate. On the bottom side of the dielectric substrate, the ground plane is engraved to form a square-shaped radiating slot. The shape of the tuning stub of the antenna is modified in order to attain a wide impedance bandwidth and an axial ratio bandwidth (ARBW). The modifications include inserting a rectangular strip and thin horizontal strips into the tuning stub after tapering its upper corner. On the other hand, the radiating slot is appended by two rectangular stubs. The radiation of the resulted structure has right-hand circular polarization (RHCP). The measured results of the proposed antenna show a −10 dB impedance bandwidth equal to 78% (2.65 GHz, 2.08–4.73 GHz), whereas its broadside 3 dB ARBW is 71.6% over the frequencies (2.31 GHz, 2.07–4.38 GHz), which is compatible with various wireless communication applications. Furthermore, the peak value of the measured gain is equal to 4.68 dB, and its value is larger than 2 dBi along the operational bandwidth of the antenna. Full article

This paper presents an optimized 868 MHz low-noise amplifier (LNA) based on a bipolar junction transistor (BJT), specifically designed for wake-up receivers operating in the sub-GHz band. The proposed LNA achieves low noise, high gain, and good impedance matching while consuming only $3.2$ mA from a $3.3$ V supply, resulting in a total power consumption of $10.56$ mW. Designing efficient sub-GHz LNAs for low-power applications involves a careful balance between multiple performance metrics. Higher gain typically requires increased biasing current, which can raise power consumption, while achieving a low noise figure often conflicts with input-matching constraints. The presented design addresses these trade-offs by leveraging the BFP740 BJT and employing a stub-based microstrip matching network to simultaneously optimize the gain, noise figure, and input–output matching. Simulation results, using both external lumped elements and microstrip techniques, show a forward gain ($S_{21}$) of $15.2$ dB at 868 MHz, with an input reflection coefficient ($S_{11}$) of $-6.9$ dB and an output reflection coefficient ($S_{22}$) of $-6.3$ dB. The amplifier achieves a minimum noise figure of approximately $1.77$ dB, which is notably low for this frequency band. These results demonstrate that the proposed LNA offers a compact, energy-efficient, and cost-effective solution, ideally suited for always-on, low-power wireless applications such as Internet of Things (IoT) devices and wireless sensor networks. Full article

The exponential growth in the number of devices connected via the internet has led to the need to achieve granular programmability for increased performance, resilience, reduced latency, and jitter. Software Defined Networking (SDN) and Programming Protocol independent Packet Processing (P4) are designed to introduce programmability into the control and data plane of networks, respectively. Despite their individual potential and capabilities, the performance of combining SDN and P4 remains underexplored. This study presents a comprehensive evaluation of SDN with data plane programmability using P4 (SDN+P4) against traditional SDN with Open vSwitch (SDN+OvS), aimed at answering the hypothesis that combining SDN and P4 strengthens the control and data plane programmability and offers improved management and adaptability, which would provide a platform with faster packet processing with reduced jitter, loss, and processing overhead. Mininet was employed to emulate three distinct topologies: multi-path, grid, and transit-stub. Various traffic types were transmitted to assess performance metrics across the three topologies. Our results demonstrate that SDN+P4 outperform SDN+OvS significantly due to parallel processing, flexible parsing, and reduced overhead. The evaluation demonstrates the potential of SDN+P4 to provide a more resilient and stringent service with improved network performance for the future internet and its heterogeneity of applications. Full article