Ceramic Resonators Research Articles

A microwave sensor for zinc corrosion detection

This article presents a sensor based on zinc wires of different widths deposited on the surface of the ceramic resonator capable of detecting and following the evolution of the corrosion of the zinc material. Electromagnetic studies show that due to the evolution of the corrosion, the progressive degradation of the conductivity of the formed zinc grid (from 6 S/μm to 0.015 S/μm) causes a degradation of the quality factor (from Q0 = 50 to Q0 < 5), a decreased level of the coefficient transmission of the TE101 mode of the resonator (from -8 dB to <-35 dB), and a progressive frequency shift (230 MHz). Experimental measurements of this sensor in a corrosive environment show a gradual shift of the resonance frequency of the TE101 mode, a decreased level of the S21 transmission coefficient, and a degradation of the unloaded quality factor. Confirmed by electronic microscopy and X–Ray analysis, these variations are due to the evolution in the corrosion of zinc wires over time, leading to a creation of corrosion products in these wires.

All-dielectric metamaterial frequency selective surface based on spatial arrangement ceramic resonators

In this paper, we demonstrate a method of designing all-dielectric metamaterial frequency selective surface (FSS) with ceramic resonators in spatial arrangement. Compared with the traditional way, spatial arrangement provides a flexible way to handle the permutation and combination of different ceramic resonators. With this method, the resonance response can be adjusted easily to achieve pass/stop band effects. As an example, a stop band spatial arrangement all-dielectric metamaterial FSS is designed. Its working band is in 11.65–12.23[Formula: see text]GHz. By adjusting permittivity and geometrical parameters of ceramic resonators, we can easily modulate the resonances, band pass or band stop characteristic, as well as the working band.

Thermally tunable slot-coupled dielectric resonator antenna

A thermally tunable slot-coupled dielectric resonator antenna (DRA) has been designed and prepared by placing a thermosensitive ceramic resonator onto the slot. Typical magnetic resonance occurs in the resonator, which is closely related to its dielectric constant. Because the dielectric constant of the ceramic resonator decreases as the temperature increases, the resonance frequency of the proposed DRA increases as the temperature increases. The simulated results are in good agreement with the measured ones, which confirms the thermally tunable behavior. This approach provides a way for designing the frequency tunable antennas.

Development of Novel Piezoelectric Biosensor Using PZT Ceramic Resonator for Detection of Cancer Markers.

A novel biosensor based on piezoelectric ceramic resonator was developed for direct detection of cancer markers in the study. For the first time, a commercially available PZT ceramic resonator with high resonance frequency was utilized as transducer for a piezoelectric biosensor. A dual ceramic resonators scheme was designed wherein two ceramic resonators were connected in parallel: one resonator was used as the sensing unit and the other as the control unit. This arrangement minimizes environmental influences including temperature fluctuation, while achieving the required frequency stability for biosensing applications. The detection of the cancer markers Prostate Specific Antigen (PSA) and α-Fetoprotein (AFP) was carried out through frequency change measurement. The device showed high sensitivity (0.25ng/ml) and fast detection (within 30min) with small samples (1μl), which is compatible with the requirements of clinical measurements. The results also showed that the ceramic resonator-based piezoelectric biosensor platform could be utilized with different chemical interfaces, and had the potential to be further developed into biosensor arrays with different specificities for simultaneous detection of multiple analytes.

In brief

PAGE 1910 A paper presented by researchers from the University of Southern California, USA, and the Birla Institute of Technology and Science, India, shows a new pass-transistor-logic based programmable delay line circuit. Compared to the commonly used design, it consumes 79.2% less dynamic energy, 83.5% less leakage power, has 47.2% better linearity across codewords and 58.6% smaller active area, with similar resiliency to variations across Monte Carlo simulations. PAGE 1906 Researchers at Zurich Research Laboratory in Switzerland present a novel architecture for Taomlinson-Harashima precoders. In this design the modulo operation is taken out of the loop so that the remaining infinite impulse response filtering is performed entirely in carry-save adder arithmetic to reduce the feedback delay, as no conversion to binary format is required within the loop. This programmable delay line circuit has a more compact active area and uses less power than conventional designs. PAGE 1954 A non-stoichiometric GaAs layer is investigated with terahertz emission spectroscopy by a group of researchers at the Center for Physical Sciences and Technology and Teravil Ltd, in Lithuania. The results obtained revealed the existence of parallel to the surface THz radiating electric dipoles. They also showed that non-stoichiometric GaAs enhances THz radiation in comparison with one of the best THz surface emitters: p-InAs and semiconductor nanowires. There are proposals to use this technology in asymmetric and memory links. PAGE 1929 A 3D-printed, ceramic resin spherical resonator X-band dual-mode bandpass filter has been created by researchers in China and the UK. They believe this to be a first of its kind, with the stereolithography-produced ceramic resin structure providing excellent thermal stability, heat handling and mechanical strength with low weight. Non-stoichiometric GaAs has potential for bias-free THz surface emitters. PAGE 1912 Researchers from Konkuk University and Hanbat National University in Korea present a novel image descriptor for fingerprint liveness detection. They propose to accumulate multiple smoothing results by globally fast edge-aware filtering. Experimental results support the efficiency and robustness of the method compared with previous local image descriptors. The 3D-printable ceramic resin can handle heat much better than other resins but is still much lighter than metal alternatives. The proposed method can be directly applied to mobile devices to improve security for users.

Characterization of low loss microwave dielectric materials Zn0.92Co0.08ZrNb2O8 based on the complex chemical bond theory

Low loss microwave dielectric ceramics Zn0.92Co0.08ZrNb2O8 with wolframite structure were prepared by the solid state method. Sintering characteristics, phase composition and microwave dielectric properties were investigated systematically. X-ray diffraction results showed that all samples exhibited a wolframite structure. Rietveld refinement was used to analyze the crystal structure. Based on the lattice parameters, the bond ionicity, the lattice energy, the bond energy and the coefficient of thermal expansion were calculated to evaluate the structural characteristics. The e r values could be strongly dependent on the bond ionicity of the Nb–O bonds. The Q·j values were main affected by the lattice energy and the bond energy of the Nb–O bonds. As for the τ f values, it could be mainly affected by the coefficient of thermal expansion of Zn/Co–O bonds. At the sintering temperature of 1200 °C, Zn0.92Co0.08ZrNb2O8 ceramics exhibited the excellent microwave properties of e r = 27.10, Q·f = 61,036 GHz (at 8.54 GHz) and τ f = −9.81 ppm/°C. These results demonstrated that Zn0.92Co0.08ZrNb2O8 ceramics could be promising candidate materials for the application of highly selective microwave ceramic resonators and filters.

Characterization on low loss dielectric Li2MgTiO4 ceramics based on chemical bond theory at microwave frequency

The low loss microwave dielectric materials Li2MgTiO4 with rock salt structure were prepared by the modified solid state method. Sintering characteristics and microwave dielectric properties were investigated under various sintering temperatures ranging from 1200 °C to 1375 °C. The crystal structure was studied by the X-ray diffraction and the micro-structure was studied by the scanning electron microscopy (SEM) techniques. Rietveld refinement was used to analyze the structure of the crystalline phase. Based on the cell parameters, the bond ionicity, lattice energy, bond energy and coefficient of thermal expansion were calculated to evaluate the structural characteristics. The εr values could be strongly dependent on the bond ionicity of the TiO bond. The Q·ƒ values were affected by the lattice energy of TiO bonds. As for the τf values, it could be mainly affected by the coefficient of thermal expansion of LiO bonds. At the sintering temperature of 1350 °C, Li2MgTiO4 ceramics exhibited the excellent microwave properties of εr = 15.07, Q·ƒ = 97,629 GHz (at 8.2 GHz) and τf = −3.81 ppm/°C. These results demonstrated that Li2MgTiO4 ceramics could be promising candidate materials for the application of highly selective microwave ceramic resonators and filters.

Sintering characteristics and microwave dielectric properties of low loss MgZrNb2O8 ceramics achieved by reaction sintering process

Wolframite structure MgZrNb2O8 ceramics were prepared by a simple and effective reaction sintering method for the first time. The crystal structure, microstructure and phase composition were studied by the X-ray diffraction, scanning electron microscopy (SEM) techniques and energy disperse spectroscopy (EDS), respectively. Sintering characteristics and microwave dielectric properties were investigated under various sintering temperatures ranging from 1150 °C to 1350 °C. In addition, bond energy, bond valence and the distortion of oxygen octahedral were calculated to evaluate the structural characteristics. At the sintering temperature of 1250 °C, the MgZrNb2O8 ceramics exhibited the excellent microwave properties of εr = 26.54, Q·ƒ = 57,477 GHz and τf = −17.69 ppm/°C. These results demonstrated that MgZrNb2O8 ceramics could be promising candidate materials for the application of highly selective microwave ceramic resonators and filters.

Reconfigurable all-dielectric metamaterial frequency selective surface based on high-permittivity ceramics.

Based on effective medium theory and dielectric resonator theory, we propose the design of reconfigurable all-dielectric metamaterial frequency selective surfaces (FSSs) using high-permittivity ceramics. The FSS is composed of ceramic resonators with different band stop responses under front and side incidences. By mechanically tuning the orientation of the ceramic resonators, reconfigurable electromagnetic (EM) responses between two adjacent stopbands can be achieved. The two broad stopbands originate from the first two resonant modes of the ceramic resonators. As an example, a reconfigurable FSS composed of cross-shaped ceramic resonators is demonstrated. Both numerical and experimental results show that the FSS can switch between two consecutive stopbands in 3.55–4.60 GHz and 4.54–4.94 GHz. The design method can be readily extended to the design of FSSs in other frequencies for high-power applications.

Achieving all-dielectric metamaterial band-pass frequency selective surface via high-permittivity ceramics

In this paper, we propose the design of all-dielectric metamaterial band-pass frequency selective surfaces (FSSs) using high-permittivity ceramics based on effective medium theory and dielectric resonator theory. The band-pass response can be determined by the permittivity of the dielectric material, the periodicity, and geometrical shape of the dielectric unit cell. As an example, a band-pass FSS composed of H shaped ceramic resonators is demonstrated. Both the simulation and experiment results show that the FSS can achieve a pass band in X-band. Since such FSSs are made of low-loss high-permittivity ceramics, they are of important application values, especially in high-temperature, high-power environments. The design method can be readily extended to the design of FSSs in other frequencies.

Wireless power transfer based on magnetic quadrupole coupling in dielectric resonators

We numerically investigate a magnetic resonant wireless power transfer system based on high refractive index dielectric resonators. We propose to operate at magnetic quadrupole mode of the resonators to enlarge the efficiency due to minimization of ohmic and radiation losses. Numerical estimation predicts the 80% efficiency of the wireless power transfer (WPT) system operating at quadrupole mode at 300 MHz. Moreover, the system operating at magnetic quadrupole mode is capable of transferring power with 70% efficiency when the receiver rotates 90°. We verify the simulated results by experimental investigation of the WPT system based on microwave ceramic resonators (ε = 80 and tanδ = 10−4).

Dielectric properties and crystal structure of (Mg<sub>0.95</sub>Ni<sub>0.05</sub>)<sub>4</sub>(Nb<sub>1−</sub><i><sub>x</sub></i>Ta<i><sub>x</sub></i>)<sub>2</sub>O<sub>9</sub> ceramics

The rapid growth of recent wireless communication systems led to an increasing demand for small-scale high-frequency resonators, filters and antennas capable of operating in the GHz range [1-3]. The unique electrical properties of ceramic dielectric resonators have revolutionized the microwave-based wireless communications industry by reducing the size and cost of filter and oscillator components in circuit systems [4,5]. At the same time, in order to work with high efficiency and stability, many researches have been focusing on developing new dielectric materials with a high quality factor (Q × f) and a near-zero temperature coefficient of resonant frequency (τf) for use as dielectric resonator and microwave device substrate [6-8].

Harmonics of piezoelectric ceramic resonators based on nonlinear elastic effects

Harmonics of piezoelectric ceramic resonators based on nonlinear elastic effects

Implementation of Filter Bank–Based RF Transceiver for TV White Space

This paper presents a general-purpose design scheme of a filter bank (FB)–based radio frequency (RF) transceiver that operates across the entire ultra-high frequency (UHF) TV band from 470 MHz to 698 MHz and complies with the TV white space (TVWS) regulatory requirements. To this end, an intermediate frequency (IF) band-pass filter (BPF) with a sharp skirt characteristic is considered as a solution for handling the incoming signals from a baseband modem. Specifically, an FB-based BPF structure with four ceramic resonator filters that effectively rejects unwanted signals is proposed to extract a desired signal in the TV band. Achievable data rates of a cognitive radio system (CRS) employing the proposed FB-based RF transceiver at the application layer are investigated in both wired and wireless environments. The service coverage of the CRS network is measured according to several modulation and coding schemes (MCSs) of the CRS. The results show that the coverage of a wireless network in a nearly open area can be extended by more than 9.3 km in the TVWS. Experimental results also confirm that the proposed FB-based RF transceiver is adequate for utilization in TVWS applications.

Electrical and dielectric studies of substituted holmium based pyrochlore zirconates nanomaterials

The effects of Ge4+ cation substitution on the structure, morphology, electrical and dielectric properties of rare earth pyrochlore oxides (Ho2Zr2-xGexO7, 0.00 ≤ x ≤ 1.0) were investigated. The pyrochlore oxides were prepared by the microemulsion method. The XRD data Ge+4 substituted Ho2Zr2-xGexO7 reveal a cubic structure. Room temperature DC electrical resistivity increases on increasing the Ge4+ contents. The value of exponent ‘n’ calculated from the plot of log(σ) versus log(ω) ranges 0.78–0.95 suggested that the conduction phenomena in the studied samples pursue hopping conduction. Nyqiust plot (cole–cole plot) was used to study relaxation phenomenon in the material. The visualization of semicircles in plot represent that grain boundary occupies small volume. The dielectric loss with frequency shows resonance peaks. The dielectric losses were stable below 1.3 GHz. Such frequency independent characteristic of the high dielectric constants Ho2Zr2-xGexO7 ceramics and their low dielectric losses make them more attractive in the applications of multilayer ceramic capacitors and resonators. The increase in resistivity with substitution makes these materials suitable for microwave devices.

Thermomechanical properties and performance of ceramic resonators for wireless pressure reading at high temperatures

This paper reports on the design, fabrication, and thermomechanical study of ceramic LC resonators for wireless pressure reading, verified at room temperature, at 500 °C and at 1000 °C for pressures up to 2.5 bar. Five different devices were fabricated from high-temperature co-fired ceramics (HTCC) and characterized. Alumina green tape sheets were screen printed with platinum paste, micromachined, laminated, and fired. The resulting samples were 21 mm × 19 mm with different thicknesses. An embedded communicator part was integrated with either a passive backing part or with a pressure-sensing element, including an 80 µm thick and 6 mm diameter diaphragm. The study includes measuring thermally and mechanically induced resonance frequency shifts, and thermally induced deformations. For the pressure sensor device, contributions from changes in the relative permittivity and from expanding air trapped in the cavity were extracted. The devices exhibited thermomechanical robustness during heating, regardless of the thickness of the backing. The pressure sensitivity decreased with increasing temperature from 15050 ppm bar−1 at room temperature to 2400 ppm bar−1 at 1000 °C, due to the decreasing pressure difference between the external pressure and the air pressure inside the cavity.

A new microwave dielectric material ZnZrNbTaO8

A new high quality microwave dielectric material ZnZrNbTaO8 was reported for the first time. Single-phase ZnZrNbTaO8 was synthetized at the sintering temperature range of 1050–1150°C. The microstructure and microwave dielectric properties were investigated systematically. The X-ray diffraction results showed that all samples exhibit a single monoclinic structure. The dielectric constant (ε) was affected by the relative density. The quality factor (Qf) increased with the increase of the packing fraction. The temperature coefficient of resonant frequency (τf) moved toward positive due to the increase of Nb/Ta–O bond valence. In summary, the monoclinic structure ZnZrNbTaO8 ceramic samples sintered at 1130°C exhibit uniform and dense microstructural morphology, and own outstanding microwave dielectric properties of ε=29.1, Qf=88,790GHz, τf=−41.55×10−6/°C. It is proposed as a very promising candidate for the application of highly selective microwave ceramic resonators and filters.

ZnO-Nb<sub>2</sub>O<sub>5</sub>-TiO<sub>2</sub> Dielectric Resonators and Porosity Influence on Dielectric Constant Values

The dielectric resonator (DR) is a ceramic component used in electronic circuits that can operate in microwave frequency range, where it plays the role of resonant element and enables the construction of high selective filters and oscillators. The dielectric properties of a ceramic resonator are influenced by their microstructure characteristics as pores amount. This work shows a study of the influence of pores amount (porosity) on the dielectric constant values of ceramics from ZnO-Nb2O5-TiO2 system. Mixtures of Nb2O5, ZnO, and TiO2 powders were compacted by uniaxial (100 MPa) and isostatic (300 MPa) pressing and sintered at 1100, 1200, and 1250°C. The experimental dielectric constant values of the sintered ceramics were corrected to eliminate the porosity influence. The results showed that the porosity, the type and quantities of crystalline chemical compounds in the ceramics influence the dielectric constant values.

All-dielectric metamaterial frequency selective surfaces based on high-permittivity ceramic resonators

In this letter, we propose the design of all-dielectric metamaterial frequency selective surface (FSS) using high-permittivity ceramics. The FSS is composed of 2D arrays of rectangular ceramic resonators. By adjusting the geometrical parameters of the ceramic resonator, the first two resonant modes are merged to achieve broadband band-stop property. As an example, a nearly 1.5 GHz wide stop-band is demonstrated both numerically and experimentally in X band. Since such FSSs are made of low-loss high-permittivity ceramics, they are of important values especially in high-temperature or high-power applications. The method can also be used to design all-dielectric FSS in other frequencies by simply scaling the geometry parameters.

Non-invasive assessment of leaf water status using a dual-mode microwave resonator.

The water status in plant leaves is a good indicator for the water status in the whole plant revealing stress if the water supply is reduced. The analysis of dynamic aspects of water availability in plant tissues provides useful information for the understanding of the mechanistic basis of drought stress tolerance, which may lead to improved plant breeding and management practices. The determination of the water content in plant tissues during plant development has been a challenge and is currently feasible based on destructive analysis only. We present here the application of a non-invasive quantitative method to determine the volumetric water content of leaves and the ionic conductivity of the leaf juice from non-invasive microwave measurements at two different frequencies by one sensor device. A semi-open microwave cavity loaded with a ceramic dielectric resonator and a metallic lumped-element capacitor- and inductor structure was employed for non-invasive microwave measurements at 150 MHz and 2.4 Gigahertz on potato, maize, canola and wheat leaves. Three leaves detached from each plant were chosen, representing three developmental stages being representative for tissue of various age. Clear correlations between the leaf- induced resonance frequency shifts and changes of the inverse resonator quality factor at 2.4 GHz to the gravimetrically determined drying status of the leaves were found. Moreover, the ionic conductivity of Maize leaves, as determined from the ratio of the inverse quality factor and frequency shift at 150 MHz by use of cavity perturbation theory, was found to be in good agreement with direct measurements on plant juice. In conjunction with a compact battery- powered circuit board- microwave electronic module and a user-friendly software interface, this method enables rapid in-vivo water amount assessment of plants by a handheld device for potential use in the field.