Coaxial Microwave Resonator Research Articles

3D printed coaxial microwave resonator sensor for dielectric measurements of liquid

AbstractThis paper presents a coaxial resonator for dielectric measurements of low and medium loss liquids at multiple resonance frequencies up to 8 GHz with the fundamental transverse electromagnetic (TEM) resonant mode at 2 GHz. The measurement is by filling the entire resonator cavity with the material under test and the permittivity of the material is readily extracted using simple equations. This technique provides an easy and accurate extraction method of dielectric properties without any analytical approximation and dedicated software algorithm as used in broadband open coaxial probes or the complex perturbation formula in resonator‐based methods. This significantly reduces the risk of systematic errors from the model approximation. The measured quality factor of the resonator is 2650 to 3500 depending on the resonant mode. This allows for the measurement of samples with loss tangents up to 0.05 (Acetone taken as a reference). The device was made by 3D printing and verified by measurements of several common solvents at all four resonance frequencies. The results obtained agree well with values reported in literature. Further measurements of crude oil samples were carried out and results confirmed with values obtained using other techniques.

Monitoring of primary drying in the freeze-drying process using an open-ended coaxial microwave resonator

An open-ended coaxial microwave resonator was designed and applied for monitoring the primary drying stage in the freeze-drying process by microwave resonance spectroscopy. A stainless steel cylindrical resonator with an inner cavity and cylindrical core was designed to sense the electrical permittivity and permeability (i.e., dielectric property) in the space over the resonator. The obtained spectrum patterns and peak intensities in the frequency range of 2500–3000 MHz responded sensitively to different volumes of ice over the probe. Monitoring of freeze-drying of a dextrin solution and sliced apple was successfully achieved by tracking the peak shift and/or the intensity of selected peak frequencies. The end-point of drying estimated from the microwave resonator perfectly corresponded to the point estimated from the product temperature during drying. This sensing device can potentially be applied for in-line monitoring of the freeze-drying process without contact to product, especially in a freeze-drying process.

High-performance brillouin spectroscopy of phonons induced by a piezoelectric thin film with a coaxial microwave resonator

To overcome the low accuracy of acoustic velocity measurements based on Brillouin scattering from thermal phonons, we attempted to utilize induced coherent phonons, which cause intense Brillouin scattering. A ZnO piezoelectric film was used to induce gigahertz-range coherent phonons in a silica glass block sample. An evanescent electromagnetic wave leaked from a coaxial resonator was applied into the film to excite phonons. The scattered light obtained using this simple system was much more intense than that obtained from thermal phonons. This technique will improve the accuracy and reduce the measurement time.

Atomic resolution imaging at 2.5 GHz using near-field microwave microscopy

Atomic resolution imaging is demonstrated using a hybrid scanning tunneling/near-field microwave microscope. The microwave channels of the microscope correspond to the resonant frequency and quality factor of a coaxial microwave resonator, which is built in to the scan head. The microscope is capable of simultaneously recording the low frequency tunnel current (0–10 kHz) and the information from the microwave channels. When the tip-sample distance is within the tunneling regime, we obtain atomic resolution images using the microwave channels. We attribute this atomic contrast to gigahertz frequency current through the tunnel junction. Images of graphite and Au(111) are presented.

1Pb-7 Observation of induced phonons by ZnO transducer with coaxial microwave resonator using Brillouin scattering(Poster Session)

1Pb-7 Observation of induced phonons by ZnO transducer with coaxial microwave resonator using Brillouin scattering(Poster Session)

Influence of the Dimensional and Form Precision of the Constructional Elements of Biconical Coaxial Microwave Resonator of the Parameter of Sensor of Movement

Influence of the Dimensional and Form Precision of the Constructional Elements of Biconical Coaxial Microwave Resonator of the Parameter of Sensor of Movement

A novel spark-plug for improved ignition in engines with gasoline direct injection (GDI)

Gasoline direct injection (GDI) is one of the future engine concepts offering a significant increase in efficiency of automotive engines. In this technique, the gasoline spray is directly injected into the combustion chamber, which yields a strongly inhomogeneous air-gasoline mixture. Hence, it is difficult to maintain reliable ignition using a conventional spark-plug. In this paper, a novel spark-plug based on a coaxial microwave resonator is presented. First, the design of the resonator is described. Then its capability of generating plasma in the pressure range up to 5 bar (3750 torr) is evaluated. Finally, some results of gasoline ignition experiments in a combustion chamber are presented.

High-frequency magnetooptics of fiber waveguides

An investigation is made of the hf distributed magnetooptic interaction in fiber waveguides associated with the Faraday effect observed under the conditions of both spatial and temporal phase matching between the normal modes of the waveguide and an external magentic field. Analytic expressions are obtained for the main relationships governing modulation of the state of polarization of light in a long fiber waveguide at high and ultrahigh frequencies. An analysis is made of several variants of hf magnetooptic modulators. It is shown that in the specific case when a 10-m long quartz fiber waveguide wound to form a cylindrical coil is placed inside the cavity of a coaxial microwave resonator and the microwave control power is 10 W, the efficiency of modulation of light should be 50%. The main theoretical predictions were supported by the reported experiments. These experiments showed that at a frequency of 80 MHz the modulation efficiency was 1% when the control power was 0.5 W.

Rotationally symmetrical electric fields and electron density distributions in a microwave plasma used in optical fibre production

Using the finite difference method, rotationally symmetrical field strengths are calculated in a coaxial microwave resonator, such as used for the production of optical fibres. A linear relation between electron density and microwave power consumption at each position inside the plasma is assumed. In this way the electron density distribution can be calculated in a self-consistent manner. The energy parameter involved (MW power per electron-ion pair sustained in the plasma) is adjusted so that experimentally obtained emission spectra with local resolution in axial and radial directions are reproduced within reasonable limits. The increase in gas temperature in the discharge has been taken into account. This simple model reproduces the most important relationships found experimentally, the MW-power dependence, the pressure dependence and the axial and radial variation of the emitted light intensity. It can easily be extended to other geometries and plasma gases. Fully three-dimensional calculations are also possible provided enough computer capacity is available.