A COMPREHENSIVE OVERVIEW OF RECENT DEVELOPMENTS IN RF-MEMS TECHNOLOGY-BASED HIGH-PERFORMANCE PASSIVE COMPONENTS FOR APPLICATIONS IN THE 5G AND FUTURE TELECOMMUNICATIONS SCENARIOS

The goal of this work is to provide an overview about the current development of radio-frequency microelectromechanical systems technology, with special attention towards those passive components bearing significant application potential in the currently developing 5G paradigm. Due to the required capabilities of such communication standard in terms of high data rates, extended allocated spectrum, use of massive MIMO (Multiple-Input-Multiple-Output) systems, beam steering and beam forming, the focus will be on devices like switches, phase shifters, attenuators, filters, and their packaging/integration. For each of the previous topics, several valuable contributions appeared in the last decade, underlining the improvements produced in the state of the art and the chance for RF-MEMS technology to play a prominent role in the actual implementation of the 5G infrastructure

A Reconfigurable Pseudohairpin Filter Based on MEMS Switches

This work presents a bandpass-reconfigurable planar pseudohairpin filter based on RF-MEMS switches. Hairpin-line structures are preferred to design microstrip filters because this class of filters offers a more compact size, and, in general, hairpin filters do not need ground connections for resonators. In this work, the U-shape resonators are arranged to obtain an interdigit capacitor to improve the coupling between the resonators. RF-MEMS switches modify the lengths of coupled resonators by adding microstrip segments to control the filter bandwidth, moving the center frequency and the return loss. An experimental hairpin tunable filter prototype based on RF-MEMS has been designed, fabricated, numerically and experimentally assessed, and compared concerning its tunability, quality factor, and capability with standard tunable filters based on PIN diodes. In conclusion, the tunable hairpin filter based on RF-MEMS switches offers the best performance in center frequency tuning range, compactness, and power consumption regarding reconfigurable filters based on standard PIN diodes switches. The obtained results are appealing and demonstrate the capabilities and potentialities of RF-MEMS to operate with the new communication standards that work at high microwave frequency bands

Pull-In Voltage and Stress in Fixed-Fixed Beams of RF MEMS Switches

Electrostatically actuated microelectromechanical system (MEMS) switches with fixed- fixed beams were fabricated. FEM modeling was used to calculate the contributions of stress in the fabricated beams from the measured values of pull-in voltage. The reported study provides useful guidelines to optimize the design of fixed-fixed beams, in order to reduce the stress contributions for the successful development of efficient and reliable electrostatically actuated MEMS devices

Symptomatic pseudoarthrosis secondary to a stress fracture of the acromion

Summary. Fractures of the acromion are uncommon clinical entities, and stress fractures are even more rare, with few cases reported. Due to their rarity, stress fractures are often misdiagnosed. Here, we report a case of an elderly patient with an acromion stress fracture, which was overlooked, resulting in nonunion followed by the displacement of the distal portion of the acromion. The purpose of this report was to discuss this rare fracture, highlighting the importance of an accurate evaluation of radiological imaging as well as clinical data

Energy poverty alleviation and its consequences on climate change mitigation and African economic development

Energy access in Africa is a key policy priority, given the strict inter-relation between energy, economic growth and sustainability. The current and projected trends on Africa access to energy and electricity indicate that unless new policies are implemented, energy access in the continent will remain low, hindering Africa’s ability to transition economically. The challenges in overcoming energy poverty and in mobilizing the investment needs for a reliable and sustainable energy infrastructure are significant, but can be attained using the right energy mix. Providing energy access will not significantly exacerbate other global challenges such as climate change mitigation. Innovative financing mechanisms and policy tools can help achieve a sustainable energy transition, and the EU can play a vital role in filling the investment gaps

Prospects of Micro/Nanotechnologies (MEMS/NEMS) in the Emerging Scenario of 6G with Focus on RF-MEMS

The emerging scenarios of 6G and, on a longer term, of Future Networks (FN) will pose challenges that cannot be addressed relying on standard design and development approaches. The network is expected to turn into a system of systems, implementing self-management and self-evolutionary capacities, especially at the edge. This work sketches a prominent role for Micro and Nanotechnologies (MEMS/NEMS) in making visions of 6G and FN possible. A comprehensive description of 6G/FN is developed, along with a reformulation of the concept of Hardware (HW), capitalizing on MEMS/NEMS technologies. Finally, RF-MEMS technology (MEMS for Radio Frequency passives) is reported as an example of 6G/FN enabling solution

Discussion and Demonstration of RF-MEMS Attenuators Design Concepts and Modules for Advanced Beamforming in the Beyond-5G and 6G Scenario—Part 1

This paper describes different variants of broadband and simple attenuator modules for beamforming applications, based on radio frequency micro electro-mechanical systems (RF-MEMS), framed within coplanar waveguide (CPW) structures. The modules proposed in the first part of this work differ in their actuation voltage, topology, and desired attenuation level. Fabricated samples of basic 1-bit attenuation modules, characterized by a moderate footprint of 690 × 1350 μm2 and aiming at attenuation levels of −2, −3, and −5 dB in the 24.25–27.5 GHz range, are presented in their variants featuring both low actuation voltages (5–9 V) as well as higher values (~45 V), the latter ones ensuring larger mechanical restoring force (and robustness against stiction). Beyond the fabrication non-idealities that affected the described samples, the substantial agreement between simulations and measurement outcomes proved that the proposed designs could provide precise attenuation levels up to 40 GHz, ranging up to nearly −3 dB and −5 dB for the series and shunt variants, respectively. Moreover, they could be effective building blocks for future wideband and reconfigurable RF-MEMS attenuators. In fact, in the second part of this work, combinations of the discussed cells and other configurations meant for larger attenuation levels are investigated

A Reconfigurable Pseudohairpin Filter Based on MEMS Switches

This work presents a bandpass-reconfigurable planar pseudohairpin filter based on RF-MEMS switches. Hairpin-line structures are preferred to design microstrip filters because this class of filters offers a more compact size, and, in general, hairpin filters do not need ground connections for resonators. In this work, the U-shape resonators are arranged to obtain an interdigit capacitor to improve the coupling between the resonators. RF-MEMS switches modify the lengths of coupled resonators by adding microstrip segments to control the filter bandwidth, moving the center frequency and the return loss. An experimental hairpin tunable filter prototype based on RF-MEMS has been designed, fabricated, numerically and experimentally assessed, and compared concerning its tunability, quality factor, and capability with standard tunable filters based on PIN diodes. In conclusion, the tunable hairpin filter based on RF-MEMS switches offers the best performance in center frequency tuning range, compactness, and power consumption regarding reconfigurable filters based on standard PIN diodes switches. The obtained results are appealing and demonstrate the capabilities and potentialities of RF-MEMS to operate with the new communication standards that work at high microwave frequency bands

Functional and Radiographic Outcomes of Minimally Invasive Intramedullary Nail Device (MIIND) for Moderate to Severe Hallux Valgus

BACKGROUND: This study was aimed at assessing clinical and radiographic outcomes of the Minimally Invasive Intramedullary Nail Device (MIIND) to correct moderate to severe hallux valgus (HV) and the long-term persistence of its effects.METHODS: This case series study involved 100 patients, 84 women and 16 men (mean age, 59 years), who underwent the MIIND procedure with a mean follow-up of 97 months. Assessment was performed preoperatively, postoperatively, at 6 and 12 months, and at last follow-up. Clinical outcomes were evaluated with American Orthopaedic Foot & Ankle Society (AOFAS) scores, visual analog scale (VAS), and patient satisfaction. Intermetatarsal angle (IMA), metatarsophalangeal hallux valgus angle (HVA), distal metatarsal articular angle (DMAA), and tibial sesamoid position were assessed. Statistical analysis was performed.RESULTS: The mean AOFAS score improved from 57.9 to 90.5 points, VAS scale was 1.5 \ub1 2.0, and patients' satisfaction was 8.7 \ub1 1.4. The mean correction of the HVA and IMA showed a significant correction; however, the effect of time was not statistically significant on DMAA. Sex (P = .047), severity (P = .050), associated procedures (P = .000), and preoperative angle (P = .000) showed significant association with HVA correction and its persistence over time. Age was not statistically significant. Complications were 9 cases of superficial wound infection and 6 recurrences.CONCLUSIONS: The MIIND technique proved a viable procedure to correct moderate to severe HV with a low rate of complications and recurrence, producing significant correction of most radiographic parameters assessed and their persistence, even at long term.LEVEL OF EVIDENCE: Level IV, case series study