Academic literature on the topic 'Resonant inductive-capacitive (L-C) circuit'

The relevance An analysis of scientific and technical literature in the field of development and research of aircraft engine ignition systems shows that the manifestations of resonant processes in nonlinear discharge circuits of capacitive ignition systems in the presence of two energy storage devices - a storage capacitor and an inductor coil have not been studied with the issuance of recommendations for matching the parameters of energy storage devices. This problem is of significant practical interest from the point of view of optimizing the parameters of the discharge circuits, increasing the energy efficiency and igniting ability of ignition systems. Aim of research Revealing the possibilities of increasing the efficiency of capacitive ignition systems based on the use of the manifestation of resonant processes in nonlinear discharge circuits containing two energy storage devices. Research methods Studies have been carried out involving a theoretical description of the processes during the discharge of the former charged capacitor to the R-L circuit, followed by experimental confirmation of the assumptions of the alleged states, described with the alleged resonance of occurrence in the discharge circuit using a similar falling current-voltage characteristic. Results The manifestations of resonant phenomena in a capacitive ignition system during the discharge of a capacitor on a non-linear circuit R-L are investigated. It is theoretically substantiated and experimentally proved that the dependences of the voltage in the spark discharge, the current and the energy of the discharges on the capacitance of the storage capacitor at a fixed inductance of the discharge circuit are uneven with inflection points corresponding to the equality of the inductive and capacitive resistances. It is shown that the energy efficiency of the discharge circuit can remain practically unchanged with a more than 1.5-fold decrease in the capacitance of the storage capacitor in the region of manifestation of resonant processes. The results obtained make it possible to coordinate the parameters of capacitive ignition systems, to determine the optimal values of the inductance of the discharge circuits for a given value of the capacitance of storage capacitors to ensure maximum energy efficiency and igniting capacity.

This paper compares performances of two wireless sensors for measuring water concentration in building materials, one manufactured by the printed circuit board (PCB) technology and another one using the low temperature co-fired ceramics (LTCC) process. The fabricated sensors consist of inductive part (L) and interdigitated capacitive part (C) in one metal layer, connected in parallel. Inductance of inductive part was kept constant, whereas capacitance of capacitive part was changed by exposing the sensor to different moisture concentration, changing its resonant frequency. The variation of resonant frequency as a function of different water concentration was measured, using antenna coil and impedance analyser, in two widely used construction materials: clay brick and autoclaved aerated concrete block. Surface analysis for two sensors was performed by means of 3D profilometer. Mechanical properties of the sensors were measured for both conductive segments (copper and silver) and substrates materials (PCB and ceramics substrates) using nanoindenter. Comparative characteristics of the sensors are presented from their application point of view.

The power factor of the circuit is determined by the amount of pure resistance (R), self-inductance of the coil (L) and the capacitance of the capacitor (C). In this study, the measurement of the power factor value in a parallel RLC circuit was carried out through experimental testing and simulation with the value of C as the independent variable, while the values of R and L were fixed conditioned quantities. The purpose of this study was to determine the effect of capacitance on a parallel RLC circuit. One of the ways to improve the power factor value in a circuit is to install capacitive compensation using a capacitor. The relation between the power factor value and the capacitance and inductive reactance based on the experimental results and the simulation calculation results in the parallel RLC circuit both shows the same pattern with a relative uncertainty below 8%. The experimental results and simulation results both show that the power factor can be improved by using a right capacitance which is around the capacitance value when there is resonance in the circuit.

Ruddlesden-Popper oxide Sr2Mn0.7Sn0.3O4 was synthesized by solid state method by calcining at different temperatures between 1200 and 1500?C. The phase evolution during thermal treatments was investigated and it was shown that the powder calcined at 1500?C and ceramics sintered at 1500?C have single phase structure. Rietveld refinement of the XRD data confirmed tetragonal crystal structure having a = b = 3.9425 ? and c = 12.1230? lattice parameters and I4/mmm space group symmetry. Permittivity (?), impedance (Z*), dissipation factor (tan ?) and AC conductivity (?AC) of the samples were studied in the frequency range 1 kHz-2MHz and temperature range 60-600?C. An equivalent circuit comprising two parallel R-L elements and one constant phase element (CPE) model fitted the impedance data very well. Components of the equivalent circuit were correlated with compositional micro inhomogeneities in the sintered sample. Resonance-like feature observed in the dissipation factor at a particular temperature is attributed to the cancellation of capacitive and inductive reactants. Negative permittivity and loss of the sintered sample were compared with other ceramic oxides showing negative permittivity.

This paper investigated an novel wireless RF pressure sensor fabricated with SU-8 polymer. The sensor consists of an inductor (L) interconnected with pressure-variable capacitor (C) to form a LC resonant circuit. The fabricated devices is 4 × 3 mm2 in size and houses 9 turns of Cu electro-plated coil with inductance of 100 nH. In this system, RF signal was transmitted from external antenna to the fabricated LC resonator. Then RF signal was changed as power of fabricated device via inductive coupling. The external antenna was modulated by resonant frequency of the LC resonator. By detecting this abrupt resonant frequency shift of the device, the pressure change of the device can be measured by wireless method.

The objective of this research was to develop a wireless pressure sensor useful for monitoring bladder pressure. The wireless sensor consists of an active capacitive element and an inductor coil. The changes in pressure are related to the changes in the resonant frequency of the internal sensor. The existing pressure sensors have inductors formed on both sides of the substrate. The changes in internal capacitance of these sensors are related to the changes in pressure by impedance matching of the internal LC circuit. The deviation in bladder pressure is an important variable in evaluating the diseased state of the bladder. The inductor designed for this application is a spirally wound inductor fabricated adjacent to the capacitor. The external sensing uses equivalent changes in internal LC. The resonant frequency of the internal sensor is defined by the deformation of the plate, causing the plate to touch the dielectric on the fixed capacitive plate, which is reflected as changes in capacitance(C). The deformation of the plate has been modeled using Finite Element Analysis. The finite element analysis optimizes the dimensions of the design. Remote sensing is achieved through inductive coupling and the changes in pressure are determined. The device is tested for pressures ranging from 0–150 mmHg, bladder pressure. The RF Telemetry system has been modeled using Sonnet. The frequency range is between 100–670 MHz which is in compliance to that specified by Federal Communications Commission (FCC) regulations.

Introduction Textile wearable systems for human movement monitoring are increasingly popular. However, few examples report on robustness to sweat, which is relevant for use in real life. Some reported the effect of artificial sweat like phosphate buffered saline (PBS; Lin et al., 2022) or simply moisture (Xu et al., 2020) on custom materials. We previously developed an all-textile wireless sensing platform with commercial conductive yarns and fabrics containing silver. There is no study on the effect of sweat on such materials, therefore we performed a preliminary study to account for moisture and potential oxydation of silver. Methods The textile sensing system is resonating RLC circuit, where the sensing part is a capacitive parallel plate strain sensor (C) located on a joint (knee). All components are textile based and contain silver. As the capacitive sensor stretches, capacitance increases and the resonance of the circuit fres decreases. This information is transmitted wirelessly via inductive coupling (Galli et al., 2023). We sprayed 1 ml of 0.1 M PBS solution on the textile capacitive sensor to simulate sweating, and applied mechanical strain before (damp state) and after air drying (dry state). The unmodified sensor (before the addition of any PBS) was also used as a baseline measure. First, we applied fixed strain (10%) with a universal testing machine; then, we tested the response of the sensorized pants when bending the knee. Results The resonance frequency of the textile sensing (RLC) circuit in the damp state was much lower than the baseline (14.85 ± 0.11 MHz vs 22.70 ± 0.12 MHz) as expected from the higher dielectric constant of water that increases the baseline capacitance of the sensor. As for the change in Δfres upon 10% strain (Δfres = fres,baseline - fres,stretch), interestingly a larger change was observed for the damp configuration as compared to the baseline and dried (1.08 ± 0.08 vs 0.79 ± 0.06 vs 0.66 ± 0.03 MHz). A similar behaviour was observed in the test with pants, where the response for flexion was Δfres = 1.58 MHz for the damp sensor and Δfres = 1.28 MHz for the dried sensor. Discussion/Conclusion This preliminary investigation showed promising results in terms of robustness of our system to artificial sweat, as there was a measurable response both in the damp and dried configurations. Further tests with different sweat amounts and rate are needed to determine the full functioning range, e.g., how much sweat is tolerated. References Galli, V., Sailapu, S. K., Cuthbert, T. J., Ahmadizadeh, C., Hannigan, B. C., & Menon, C. (2023). Passive and wireless all-textile wearable sensor system. Advanced Science 10(22), Article 2206665. https://doi.org/10.1002/advs.202206665 Lin, R., Kim, H.-J., Achavananthadith, S., Xiong, Z., Lee, J. K. W., Kong, Y. L., & Ho, J. S. (2022). Digitally-embroidered liquid metal electronic textiles for wearable wireless systems. Nature Communications, 13, Article 2190. https://doi.org/10.1038/s41467-022-29859-4 Xu, L., Liu, Z., Zhai, H., Chen, X., Sun, R., Lyu, S., Fan, Y., Yi, Y., Chen, Z., Jin, L., Zhang, J., Li, Y., & Ye, T. T. (2020). Moisture-resilient graphene-dyed wool fabric for strain sensing. ACS Applied Materials & Interfaces, 12(11), 13265–13274. https://doi.org/10.1021/acsami.9b20964

The paper presents equivalent substitution circuits (ESCs) describing nanogranular composite films (Fe0.45Cо0.45Zr0.10)x(Al2O3)1 – x and (Fe0.45Cо0.45Zr0.10)x(PZT)1 – x with a concentration of metal-containing granules in the range 0.3 < х < 0.8. Films of 2–7 μm thick were obtained by ion-beam sputtering of composite targets in pure argon or in Ar – O2 mixture, followed by stepwise (with a step of 25 K) isochronous (15 min) annealing in air in the temperature range of 398 – 873 K. Deposition of nanocomposites in an oxygen-containing atmosphere or subsequent annealing in air led to the formation of nanoparticles with a core – shell structure consisting of Fe0.45Cо0.45Zr0.10 metallic alloy cores coated with shells of native iron and cobalt oxides (FeO, Fe3O4, Fe2O3, CoO). It has been established that when such shells contain semiconductor-type iron oxides (like FeO and Fe3O4) the frequency dependences of the total impedance Z (f, T) of nanocomposites can be described using ESCs containing two resonant RCL-circuits, that is accompanied by a positive phase shift of the current relative to the applied bias voltage (the so-called negative capacitance effect). The prevailing of dielectric-like oxides (Fe2O3) in shells around metallic cores leads to ESCs either with one resonant RCL-circuit or without it at all. This results in disappearing of the negative capacitance effect when usual capacitive-like behaviour of nanocomposite behaviour is observed. It is shown that if we construct ESCs for nanocomposites with different ratios of the metallic (FeCoZr) and dielectric (Al2O3, PZT) components, it is possible to describe the Z (f, T) dependences for every circuit elements (R, C, L) corresponding both to individual phase components in nanocomposites including intrinsic semiconductor- or dielectric-like iron and cobalt oxides in shells around metallic cores.

Physiological pressure measurement is one of the most common applications of sensors in healthcare. Particularly, continuous pressure monitoring provides key information for early diagnosis, patient-specific treatment, and preventive healthcare. This paper presents a thin-film flexible wireless pressure sensor for continuous pressure measurement in a wide range of medical applications but mainly focused on interface pressure monitoring during compression therapy to treat venous insufficiency. The sensor is based on a pressure-dependent capacitor (C) and printed inductive coil (L) that form an inductor-capacitor (LC) resonant circuit. A matched reader coil provides an excellent coupling at the fundamental resonance frequency of the sensor. Considering varying requirements of venous ulceration, two versions of the sensor, with different sizes, were finalized after design parameter optimization and fabricated using a cost-effective and simple etching method. A test setup consisting of a glass pressure chamber and a vacuum pump was developed to test and characterize the response of the sensors. Both sensors were tested for a narrow range (0–100 mmHg) and a wide range (0–300 mmHg) to cover most of the physiological pressure measurement applications. Both sensors showed good linearity with high sensitivity in the lower pressure range <100 mmHg, providing a wireless monitoring platform for compression therapy in venous ulceration.

Dielectric materials are an important research topic for many applications today. Polymers are among the prominent dielectrics due to their durability, high ionic conductivity and low dielectric losses. This study investigates the dielectric properties of Parylene C (PAC)-based composite films. Capacitance and dissipation factor values are measured. Dielectric permittivity and losses are calculated. Negative capacitance and negative dielectric constant are observed, and resonant frequency values are compared. Activated carbon doping significantly impacts the resonant frequencies of the films. Doped samples exhibit higher positive and negative resonant frequencies (2.2560 MHz and 2.2593 MHz) compared to undoped counterparts (2.1952 MHz and 2.2015 MHz). Polarization further increases resonant frequencies, alongside dielectric permittivity and dissipation factor with permittivity experiencing a more pronounced increase. Post-polarization, doped samples display resonant frequencies of 2.3727 MHz and 2.3761 MHz, while undoped samples reach 2.3658 MHz and 2.3727 MHz. A comprehensive analysis of impedance, resistance, and reactance values reveals insights into the composite film's behavior. Crucially, throughout the measurements, the composite films display a consistent inductive response at frequencies above their resonance frequencies. Understanding the mechanisms behind this inductive response could open up new possibilities for the use of these films in advanced electronic devices and circuits.

Developments in RF MEMS switches have demonstrated great potential at low-loss microwave application. MEMS shunt switches have a few advantages compared to the FET or p-i-n diode counterparts due to their characteristics of low intermodulation distortion or harmonics, low DC power consumption, low insertion losses and high isolation [1][2]. RF MEMS shunt capacitive switches has shown excellent performance from Ka-band to W-band, however, they fail to perform the same in X-band for the low isolation in this frequency range. Various approaches have been introduced to address this shortcoming, such as applying high-impedance transmission line [3], using strontium titanate oxide (SrTiO3) as high relative dielectric constant material [2], etc. Aimed at X-band applications, this paper reports a novel design of a high isolation RF MEMS shunt capacitive switch which is fabricated on a groove etched substrate. Fig. 1(a) and Fig. 2(a) show the schematics of the MEMS capacitive switch. The switch is constructed on a coplanar waveguide (CPW) transmission line. When the switch is up, the switch presents a small shunt capacitance to ground, presenting an RF open. When the switch is pulled down to the center conductor by electrostatic force, the shunt capacitance increases remarkably, presenting an RF short. In this work, a short high-impedance section of transmission line is designed between the MEMS bridge and the ground plane. This increases the series inductance of the switch so as to lower the resonant frequency. The length of this line is designed to put the series resonant frequency into the frequency range of X-band. Two grooves are etched into the substrate along the center conductor between the transmission line and the ground plane. For the desired characteristic impedance, a wider center conductor width can be obtained by increasing the groove depth accordingly. Thus the CPW with grooves potentially has a lower attenuation due to conductor losses [4]. Moreover, as center conductor gets wider, the down-state shorting-circuit capacitance increases which helps to gain a higher isolation. The mechanical and RF performances of this switch have been analyzed by FEA software, IntelliSuite and HFSS. As shown in Fig. 1(b), the actuation voltage of the planar switches is 26V. The RF characteristics of the switch at down state are obtained through HFSS. In Fig. 1(c), the down state isolation reaches −54.6dB at its self-resonate frequency of 13.5GHz. Compared with the non-grooves counterpart, the designed grooves optimize the isolation performance by 7dB. The insertion loss is less than 0.2 dB from 5 to 30 GHz. Fig. 2(a) shows the serpentine folded suspension switch, its actuation voltage is 14V, shown as in Fig. 2(b). The RF response in Fig. 2(c) demonstrates that the series resonant frequency is down to 11GHz due to the inductance introduced by serpentine folded suspensions. The down state isolation is −42.8dB at 11GHz. However, it is demonstrated that the substrate grooves did not help to optimize isolation performance. This is due to the higher resistance and inductance introduced by serpentine folded suspension. This research is supported by “Hundreds Scholar Program”, Chinese Academy of Sciences.