A compact and miniaturized implantable antenna for ISM band in wireless cardiac pacemaker system

A tiny and compact implantable antenna for wireless cardiac pacemaker systems is designed. The antenna works in the Industrial Scientific Medical (ISM) frequency band (2.4–2.48 GHz). The size of the antenna is greatly reduced with the adoption of a high dielectric constant medium and a folded meander structure. The volume of the antenna is 4.5 mm3, and the size is only 3 mm × 3 mm × 0.5 mm. Based on the literature research, it was found that the design was the smallest among the same type of implanted antenna. The antenna is optimized and loaded with a defective slotted structure, which improves the efficiency of the overall performance of the antenna and thus the gain thereof. The antenna maintains good impedance matching in the ISM frequency band, covering the entire ISM frequency band. The actual bandwidth of the antenna is 22%, with the peak gain of − 24.9 dBi. The antenna is processed and manufactured in such a manner that the simulation keeps consistent with the actual measurement. In addition, the specific absorption rate of the antenna is also evaluated and analyzed. The result shows that this kind of antenna is the best choice to realize the wireless biological telemetry communication in the extremely compact space of the wireless cardiac pacemaker system.

Compounding a High Dielectric Constant Thermoplastic Material for Production of Microwave Photonic Crystals through Additive Manufacturing

Additive Manufacturing techniques allow the production of complex geometries unattainable through other traditional technologies. This advantage lends itself well to rapidly iterate and improve upon the design of microwave photonic devices, which are structures with intricate, repeating features. The issue tackled by this work involves compounding a high-dielectric constant material that can be used to produce 3D topological structures using polymer extrusion-based AM techniques. This material was ABS based, and used barium titanate ceramic as the high-dielectric compound of the composite, and involved the use of a surfactant and a plasticizer to facilitate processing. Initial small amounts of material were compounded using an internal batch mixer, and studied using polymer thermal analysis techniques, such as thermogravimetric analysis, rheometry, and differential scanning calorimetry to determine the proper processing conditions. The production of the material was then scaled-up through the use of a twin-screw extruder system, producing homogeneous pellets. Finally, the thermoplastic composite was used with a screw-based, material extrusion additive manufacturing technique to produce a slab for measuring the dielectric constant of the material, as well as a preliminary 3D photonic crystal. The real part of dielectric constant of the composite was measured to be 12.85 in the range of 10GHz to 12GHz, representing the highest dielectric constant ever demonstrated for a thermoplastic AM composite at microwave frequencies. The dielectric loss tangent was equal to 0.046, representing a low-loss dielectric.

Thermochemical Equilibrium Modeling Indicates That Hg Minerals Are Unlikely to Be the Source of the Emissivity Signal on the Highlands of Venus

Several of the highlands of Venus exhibit unexpectedly low radar emissivity compared to that of the lowlands. The source has been hypothesized to be a mineral with a high dielectric constant. Recently HgTe (coloradoite) has been suggested to explain the low emissivity signal; however, little research has been completed to verify its stability on Venus. In this project, we used a Gibbs free energy minimization software to investigate whether HgTe, as well as HgS and HgSe, can form at simulated highland conditions. According to our calculations, approximately 1.3 wt% of mercury in the crust needs to be outgassed in order for HgS to be stable at 4 km in altitude. In addition, approximately 250 ppb of tellurium in the crust needs to be outgassed for HgTe to precipitate at the same altitude. The required mercury abundance for HgSe to be stable at this altitude is less, approximately 0.6 wt%; however, this is significantly larger than the 10–90 ppb generally present in basaltic rocks on Earth. Therefore, Hg-bearing minerals are likely not the source of the low radar emissivity signal.

Can the results of quantum refinement be improved with a continuum-solvation model?

Quantum refinement has repeatedly been shown to be a powerful approach to interpret and improve macromolecular crystal structures, allowing for the discrimination between different interpretations of the structure, regarding the protonation states or the nature of bound ligands, for example. In this method, the empirical restraints, used to supplement the crystallographic raw data in standard crystallographic refinement, are replaced by more accurate quantum mechanical (QM) calculations for a small, but interesting, part of the structure. Previous studies have shown that the results of quantum refinement can be improved if the charge of the QM system is reduced by adding neutralizing groups. However, this significantly increases the computation time for the refinement. In this study, we show that a similar improvement can be obtained if the original highly charged QM system is instead immersed in a continuum solvent in the QM calculations. The best results are typically obtained with a high dielectric constant (ɛ). The continuum solvent improves real-space Z values, electron-density difference maps and strain energies, and it normally does not affect the discriminatory power of the calculations between different chemical interpretations of the structure. However, for structures with a low charge in the QM system or with a low crystallographic resolution (>2 Å), no improvement of the structures is seen.

Traceable Nanoscale Measurements of High Dielectric Constant by Scanning Microwave Microscopy

The importance of high dielectric constant materials in the development of high frequency nano-electronic devices is undeniable. Their polarization properties are directly dependent on the value of their relative permittivity. We report here on the nanoscale metrological quantification of the dielectric constants of two high-κ materials, lead zirconate titanate (PZT) and lead magnesium niobate-lead titanate (PMN-PT), in the GHz range using scanning microwave microscopy (SMM). We demonstrate the importance of the capacitance calibration procedure and dimensional measurements on the weight of the combined relative uncertainties. A novel approach is proposed to correct lateral dimension measurements of micro-capacitive structures using the microwave electrical signatures, especially for rough surfaces of high-κ materials. A new analytical expression is also given for the capacitance calculations, taking into account the contribution of fringing electric fields. We determine the dielectric constant values εPZT = 445 and εPMN-PT = 641 at the frequency around 3.6 GHz, with combined relative uncertainties of 3.5% and 6.9% for PZT and PMN-PT, respectively. This work provides a general description of the metrological path for a quantified measurement of high dielectric constants with well-controlled low uncertainty levels.

Sintering characteristics and microwave dielectric properties of 0.5(Ca0.7Nd0.2)TiO3–0.5(Li0.5Nd0.5)TiO3 ceramics with La2O3–B2O3–CaO–P2O5 additive

In this paper, the effects of glass-ceramics sintering aid, La2O3–B2O3–CaO–P2O5 (LBCP), on the sinterability, microstructure, and microwave dielectric properties of 0.5(Ca[Formula: see text]Nd[Formula: see text]TiO3–0.5(Li[Formula: see text]Nd[Formula: see text]TiO3 (CNT–LNT) ceramic have been investigated. The results indicated that LBCP glass-ceramics has good wettability to CNT–LNT (contact angle at 980[Formula: see text]C is 31.9[Formula: see text]), and it can be used as an effective sintering aid to reduce the sintering temperature of CNT–LNT ceramic from 1300[Formula: see text]C to 980[Formula: see text]C. LBCP glass-ceramics did not change the main crystal phase (perovskite structure) of the sample, but a small amount of LaBO3 and LaPO4 phases was precipitated. Since the LaBO3 and LaPO4 phases are low-loss phases, it is believed that the crystal phases can improve the dielectric properties of the sample, especially the dielectric loss. The samples with 10 wt.% of glass additive sintered for 4 h at 980[Formula: see text]C exhibit the optimized properties: a high dielectric constant of 80.8 and a [Formula: see text] value of 2031 GHz. The high [Formula: see text] and [Formula: see text] value, coupled with a relatively low sintering temperature, suggest that the optimized compositions have the potential to be used in microwave low-temperature co-fired ceramics applications.

A Composite of (95%) La2CoMnO6+ (5%) Ba0.5Na0.5TiO3 : Study of Structural and Dielectric Properties

This project work reports synthesis, structural and dielectric nature of composite of the type (95%) La2CoMnO6+ (5%) Ba0.5Na0.5TiO3. The composite was characterized at room temperature for structural and dielectric properties. The structural characterization X-ray diffraction was carried for structural confirmation. The XRD data study convey the sample is dual phase in nature evident from the corresponding diffraction peaks. Monoclinic phase was acquired by La2CoMnO6 and the space groupof the phase is P 1 21/n whereas Ba0.5Na0.5TiO3 phase has acquired cubic structure with space group Pm-3m. The frequency dependent dielectric constant examined reveals high dielectric constant which decreases with increase in applied ac field values. Dielectric loss calculated shows the behaviour like dielectric constant which initially decreases abruptly with applied field and later attains frequency independent values. However, the ac conductivity was observed higher in the as synthesized.