Papers by Keyword: Resonator

Abstract: This paper introduces a concept of propellant-less microwave thruster for upper stage and space applications. The propellant-less microwave thruster works on classical electromagnetic theory, where the microwave radiations are converted to the electromagnetic pressure that acts as axial thrust. In microwave thrusters, microwaves are radiated to a sealed conical cavity which follows the contour of the thrusters to produce pressure. Normally, there are three types of methods by which thrust can be produced without utilizing any propellant. Cannae Drive, EmDrive, and the Wrap Drive are mostly used. The first two are based on the principle of microwave radiation, whereas the third method is just a concept in various science fiction films. The EmDrive can produce a small amount of thrust, therefore, its application is limited to upper stage thruster, orbit/trajectory correction, and deep-space exploration. This paper provides an insight on the feasibility of EmDrive for space application by comparing its performance with ion propulsion system. The proposed microwave propulsion system has low system mass (typically in Kgs), produces high thrust (in mN) and even has higher specific impulse (in years) which can outweigh the current ion propulsion system.

Abstract: This paper presented a new design of bendable hexagonal resonator for chipless RFID tag. A linearly polarized plane wave and Radar Cross Section (RCS) probes were used in simulation set-up. The optimized resonator was fabricated on a thin fast-film substrate with dielectric constant, ε_r=2.7 and substrate thickness, t = 0.13 mm. The fabricated resonator consisted of 3 hexagonal slots which represented three bit 1s. The measurement was performed to validate the designed resonator. It was measured using two transmitting and receiving horn antennas along with the network analyzer. The measured magnitudes were-24.292 dB, -28.854 dB and-32.234 dB.

Abstract: Dynamic characteristics of a dielectric elastomer based micro beam resonator are investigated by taking into consideration of squeeze-film damping, large deformation and electrical voltage. The analysis shows that the resonant frequency of the resonator can be tuned through changing applied electrical voltage. It is observed that the natural frequency of the resonator increases with the increase of the vibration amplitude. In addition, the ambient pressure can significantly alter the resonant frequency of the resonator. The analysis is envisaged to provide qualitative predictions and guidelines for design and application of DE-based micro resonators.

Abstract: Thermoacoustic refrigerator is an alternative cooling system, which is environmentally safe due to the absence of any refrigerants. The resonator tube of the system is of great importance; its design and dimensions influence the design and performance of the entire refrigerator. This work describes the design of the stack and the resonator along with the influence of its dimensions on the performance of the standing-wave thermoacoustic refrigerator. The resonator consists of two tubes, one larger than the other, characterized by the diameter ratio of the smaller over the larger diameter. A Lagrange multiplier method is used as a technique to optimize the coefficient of performance (COP) of the system. Results show that the resonator small diameter tube dissipates a minimum acoustic power at a diameter ratio of 0.46, which is 17 percent less than the published values. Moreover, the results show that the resonator length increases gradually with the increase of the mean design temperature which leads to the increase of the total acoustic power dissipated by the resonator, reducing the COP of the standing-wave thermoacoustic refrigerator.

Abstract: This paper presents the theoretical and experimental study of the excitation of electromagnetic waves in the TEM-mode in coaxial vircator with radially divergent electron beam. Excitation of electromagnetic oscillations, emission spectrum, instability increment of electromagnetic oscillations, and formation of a virtual cathode are investigated using the kinetic equation and numerical simulation (PIC code KARAT). It was shown that the resonant interaction of the electron beam is most effectively done with the TEM-mode. The possibility of TEM-mode excitation with its subsequent transformation into TE10-mode of a rectangular waveguide has been experimentally demonstrated.

Abstract: Deep reactive ion etching (DRIE) process is specially invented for bulk micromachining fabrication with the objective of realizing high aspect ratio microstructures. However, various tolerances, such as slanted etched profile, uneven deep beams and undercut, cannot be avoided during the fabrication process. In this paper, the slanted etched profile fabrication tolerance with its effect on the performances of lateral comb-driving resonator, in terms of electrostatic force, mechanical stiffness, and resonance frequency, are discussed. It shows that comb finger with positive slope generates larger electrostatic force. The mechanical stiffness along lateral direction increases when the suspended beam slants negatively. The resonance frequency is 1.116 times larger if the comb finger and beam are tapered to -2⁰ and + 2⁰, respectively. These analytical results can be used to compensate the fabrication tolerances at design stage and allow the resonator to provide more predictable performance.

Abstract: In order to increase the potential applications of thermoacoustic engine, coiling the resonator tube is another idea to miniaturise the engine. Resonator is an essential component used to sustain the driving acoustic waves. Coiling of resonator will definitely improve the engine footprint but it may introduce losses that are not encountered by the straight resonator. A straight resonator tube is the easiest design and will have small energy losses, but it requires large space. The proposed work in coiling the resonator will certainly create more energy losses than the previous designs but the magnitude of these losses are unknown. In this paper, an impedance tube system was built to measure the sound energy losses of coiled tubes of different configurations and comparing the results with the losses in a straight tube. The impedance tube system designed for the testing consists of an upstream tube, the test section and a downstream tube. A similar investigation was also conducted for different number of sharp turns of the tubes. The two-load method was used to analyse the results by using the four-microphone impedance tube methodology. The results showed significant differences between the four configurations and the outcomes were found to be very useful in the future when designing miniature thermoacoustic engine. Nomenclature

Abstract: This paper presents an optimization on the resonator, which is one of the main components of electromagnetic energy harvester, using static structural analysis, stress analysis and modal analysis. The electromagnetic energy harvester is a vibration-based energy harvesting technology which has emerged as a solution for powering autonomous sensor nodes to increase their life span. Electromagnetic energy harvester acts as a transducer that converts ambient vibration energy to electrical power. An initial design of the resonator is developed and analyzed using ANSYS software. Static structural analysis and stress analysis have been performed to analyze different resonator designs to produce an optimum resonator model. Maximum static deflection under gravitation force was found to be 104.12 μm. Resonance frequency of the resonator was found to be 261.56Hz by using modal analyses. The selected resonator design was further modified to cater for wide-band frequency application as well as to have better performance. Four resonators with different beam lengths were combined in a model in order to operate at a wider frequency range. Five models were generated and the smallest frequency range is from 272 Hz to 299 Hz by model 5110_5410. The maximum power and minimum power that can be generated for this model is 135 μW and 93.9 μW respectively. The model 3910_4210 which has the highest frequency range generated a maximum power of 437 μW and minimum power of 270 μW at a frequency range of 422 Hz to 466 Hz.

Abstract: The applications of quartz for electric devices had been progressed for a long time. In the early period, the primary application of quartz is focused on the crystal resonator and filter^1-4). The other important application of quartz is on the QCM(quartz crystal microbalance). The basic principle of QCM is based on the mass loading effect, which makes the resonator frequency shift and the mass loading is directly proportion to the shift of frequency. V.M.Mecea has shown the theory of mass loading and its applications⁵⁾. For using quartz as microbalance or sensor, an electronic circuit for change the shift of frequency to electronic signal is necessarily. Unfortunate, another important influence of mass loading is the inharmonic mode appearance with large mass load and inconveniently for designs the electric circuit. So a pure fundamental mode resonator is expected for used the quartz as sensor devices.

Abstract: Based on magnetoelastic biosensor for the heavy ion detection, this paper is committed to study the influence of the excitations and detection positions on the sensitivity of magnetoelastic biosensors. The frequency response of biosensors with different excitations and different detection positions were studied. The numerical simulation software ANSYS [TM] Ansoft Maxwell was applied to calculate the distribution of magnetic field around the coil. The optimal excitation value was determined by this simulation. The frequency test of the magnetoelastic sensor was analyzed by a network analyzer, which showed the frequency in the middle of coil is better than in the two ends.