Microstrip band-stop filter based on double negative metamaterial

In this work, we present a novel miniature band stop filter based on double negative metamaterial, this circuit is designed on a low-cost substrate FR-4 of relative permittivity 4.4 and low tangential losses 0.002. The proposed filter has a compact and miniature size of 15 mm in length and 12mm in width without the 50 Ω feed lines. The resonator was studied and analyzed with a view to achieving a band-stop behavior around its resonant frequency. The band-stop characteristics are obtained by implementing the metamaterial resonator on the final structure. The obtained results show that this microstrip filter achieves fractional bandwidth of 40% at 2 GHz. Furthermore, excellent transmission quality and good attenuation are achieved. This filter is an adequate solution for global system for mobile communications (GSM).

Acoustic metamtaterial and metasurface composed of meta-atoms and meta-molecules

Acoustic metamaterials (AMMs) and acoustic metasurfaces (AMSs) are artificially structured materials with the unique properties not found in natural materials. We reviewed herein the properties of AMM and AMS that have been designed using the meta-atoms of split hollow spheres (SHSs) and hollow tubes (HTs) or meta-molecules of split hollow tubes (SHTs) with local resonance. AMMs composed of SHSs or HTs display a transmission dip with negative modulus or negative mass density. AMMs composited with SHSs and HTs present a transmission peak and a phase fluctuation in the overlapping resonant frequency region, indicating that they simultaneously have a negative modulus and a negative mass density. Furthermore, the meta-molecule AMMs with SHTs also exhibit double-negative properties. Moreover, the acoustic meta-atoms or meta-molecules can be used to fabricate acoustic topological metamaterials with topologically protected edge states propagation. These meta-atoms and meta-molecules can also attain phase discontinuity near the resonant frequency, and thus they can be used to design AMSs with the anomalous manipulation for acoustic waves. The various tunability of the meta-molecules provides a feasible path to achieve broadband AMS.

Piezoelectric MEMS Acoustic Transducer with Electrically-Tunable Resonant Frequency

The paper presents a technique to obtain an electrically-tunable matching between the series and parallel resonant frequencies of a piezoelectric MEMS acoustic transducer to increase the effectiveness of acoustic emission/detection in voltage-mode driving and sensing. The piezoelectric MEMS transducer has been fabricated using the PiezoMUMPs technology, and it operates in a plate flexural mode exploiting a 6 × 6 mm doped silicon diaphragm with an aluminum nitride (AlN) piezoelectric layer deposited on top. The piezoelectric layer can be actuated by means of electrodes placed at the edges of the diaphragm above the AlN film. By applying an adjustable bias voltage Vb between two properly-connected electrodes and the doped silicon, the d31 mode in the AlN film has been exploited to electrically induce a planar static compressive or tensile stress in the diaphragm, depending on the sign of Vb, thus shifting its resonant frequency. The working principle has been first validated through an eigenfrequency analysis with an electrically induced prestress by means of 3D finite element modelling in COMSOL Multiphysics®. The first flexural mode of the unstressed diaphragm results at around 5.1 kHz. Then, the piezoelectric MEMS transducer has been experimentally tested in both receiver and transmitter modes. Experimental results have shown that the resonance can be electrically tuned in the range Vb = ±8 V with estimated tuning sensitivities of 8.7 ± 0.5 Hz/V and 7.8 ± 0.9 Hz/V in transmitter and receiver modes, respectively. A matching of the series and parallel resonant frequencies has been experimentally demonstrated in voltage-mode driving and sensing by applying Vb = 0 in transmission and Vb = −1.9 V in receiving, respectively, thereby obtaining the optimal acoustic emission and detection effectiveness at the same operating frequency.

A Simple Model to Compute the Characteristic Parameters of a Slotted Rectangular Microstrip Patch Antenna

In this study, we developed an analytical model of slot-loaded rectangular microstrip patch antennas based on the simulation results by varying slot parameters. The dominant resonant frequency predicted by such a model is in strong agreement with the experimental results measured at several locations of slot-loaded rectangular microstrip patch antennas. The model enables a reliable and quick computation of the resonant frequency, which generally follows a harmonic behavior that nearly resembles the resonant frequency of a microstrip antenna without a slot, which can be related to a small change in the impedance caused by the slot position. Results showed a good agreement between simulations and measurements for all the slot positions. Mathematical analytic functions to describe the changes in specific characteristic parameters of the slot-loaded rectangular microstrip patch antennas are also included.

A Rudimentary X band CW-EPR Spectrometer Based on FPGA

A rudimentary Electron Paramagnetic Resonance (EPR) spectrometer is design using a field programmable gate array (FPGA) equipped with two digital-to-analog (DAC) and two analog-to-digital (ADC) channels. The single stage heterodyne setup operates at X band frequencies and is used to detect EPR signals from 2,2-diphenyl-1-picrylhydrazyl (DPPH) in a loop-gap resonator. We design the loop gap resonator with 3 loops 2 gaps for high field homogeneity and moderate Q-factor. The resonator is coupled capacitively to the coaxial cable and is designed to have an unloaded resonant frequency of 8.856 GHz with a Q-factor of 646.0 when critically coupled. The loaded resonant frequency is reported to be 8.668 GHz with a Q-factor of 615.8. Using this setup, EPR signal is successfully detected at 311.4 mT and 8.688 GHz with an experimental g-factor of 1.99450.0012, which is very near to the standard value for DPPH.

Study on the Behavior of Helmholtz Resonance in Different Size Bottles

The resonance is the specific response of system which is capable to vibrate with certain frequency to an external force acting with the same frequency. When air is blown across the open mouth of different bottles then air vibrate in a neck at resonant frequency. In this study we consider 5-5 bottles of different five types bottles having different of length of neck, radius of port, cross-sectional area of port and same volume (250ml). Resonance in different bottles was studied to determine how the volume of air cavity of different bottle affects the resonance. From calculated and experimental data, we found that the Helmholtz resonance frequency decreases with increase in volume and vice versa in each case of different bottles. From graph we also found that the calculated and experimental model are about 100% and 99% variability of the response data around its mean. The practical range for these different bottles is from about 256 to 512 Hz. This is about an octave plus a musical fifth near the middle of the musical instrument, so most simple musical tunes can be produced with such bottles.

Development and characterisation of a self-powered measurement buoy prototype by means of piezoelectric energy harvester for monitoring activities in a marine environment

<p class="Abstract">In the interest of our society, for example in Smart City but also in other specific backgrounds, environmental monitoring is an essential activity to measure the quality of different ecosystems. In fact, the need to obtain accurate and extended measurements in space and time has considerably become relevant. In very large environments, such as marine ones, technological solutions are required for the use of smart, automatic, and self-powered devices in order to reduce human maintenance service. This work presents a simple and innovative layout for a small self-powered floating buoy, with the aim of measuring and transmitting the detected data for visualization, storage and/or elaboration. The power supply was obtained using a cantilever harvester, based on piezoelectric patches, converting the motion of ripple waves. Such type of waves is characterized by frequencies between 1.50 Hz and 2.50 Hz with oscillation between 5.0 ° and 7.0 °. Specifically, a dedicated experimental setup was created to simulate the motion of ripple waves and to evaluate the suitability of the proposed design and the performance of the used harvester. Furthermore, a dynamic analytical model for the harvester has been defined and the uncertainty correlated to the harvested power has been evaluated. Finally, the harvested voltage and power have shown how the presented buoy behaves like a frequency transformer. Hence, although the used cantilever harvester does not work in its resonant frequency, the harvested electricity undergoes a significant increase.</p><p class="Abstract"><span lang="EN-US"><br /></span></p>

Miniaturized Dual-Band Dual-Mode Microstrip Patch Antenna with Defected Ground Structure for Wearable Applications

This work presents the performance of a miniaturized dual-band dual-mode microstrip patch antenna with Defected Ground Structure (DGS) at 2.45 GHz and 5.8 GHz on the stacked substrate configuration in the order of FR-4 – PDMS- FR-4. The antenna offers a promising solution for wearable applications in the ISM bands. The first substrate is a flexible Flame Retardant 4 (FR-4) and the other substrate is a highly flexible Polydimethyl Siloxane (PDMS). The size of the antenna was reduced from 50 × 50 mm2 to 30 × 30 mm2, by introducing DGS on the ground plane. A single U-slot on the rectangular radiating patch was introduced to produce the upper resonant frequency of 5.8 GHz while the existing square patch is to generate the lower resonant frequency of 2.45 GHz. The simulations on the dual-band dual-mode microstrip patch antenna shows the reflection coefficient, S11 at 2.45 GHz is -17.848 dB with a bandwidth of 278.8 MHz and -13.779 dB with a bandwidth of 273 MHz at 5.8 GHz. A unidirectional radiation pattern observed in the E-plane shows that the antenna could be applied for off-body communication while an omnidirectional radiation pattern in the H-plane showed that the antenna can be used for on-body communication. Bending investigation were performed for the antenna over a vacuum cylinder with varying diameters of 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm and 120 mm in the CST MWS® software. From the graph of reflection coefficients, the performance of the antenna were not affected in bending condition. The SAR simulations showed that the SAR limits obey the guidelines as stipulated by the Federal Communication Commission (FCC) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) for 1 mW of input power. The 2.45 GHz SAR limit for 1 g of human tissue is 0.09007 W/kg (FCC standard: < 1.6 W/kg) while for 10 g is 0.01867 W/kg (ICNIRP standard: < 2 W/kg). For 5.8 GHz, the SAR limit for 1 g of human tissue is 0.115 W/kg and for 10 g is 0.03517 W/kg. Based on the performance of the antenna in bending condition and the SAR limits, it is safe to conclude that the antenna can be used for wearable applications at 2.45 GHz and 5.8 GHz of the ISM bands.