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Introduction
Published in Nguyen Van Toan, Takahito Ono, Capacitive Silicon Resonators, 2019
A resonator is a structure that exhibits resonant behavior, meaning a resonator oscillates naturally with greater amplitude at its resonant frequencies than at others. The oscillations in a resonator can be either electromagnetic or mechanical. Guitar strings resonating at frequencies in audible range between 20 Hz and 20 kHz is a typical example of mechanical resonator in macro scale. A micromechanical resonator is a micromachined mechanical structure of much smaller size in a comparison with a guitar that can operate at much higher frequencies from kilohertz up to megahertz or even gigahertz. This frequency range is interesting for a variety of applications in electronic circuits and systems, which has attracted more attention and investment in recent years. Many Internet of things (IoT) devices can be connected to the Internet via wireless networks. The increasing amount of transmitted and received information requires accurate data transmissions. Satisfying these issues, micro clock generators for transmitters and receivers with a smaller size and higher performance are required.
Acoustical Materials
Published in Lewis H. Bell, Douglas H. Bell, Industrial Noise Control, 2017
Lewis H. Bell, Douglas H. Bell
Acoustical materials can be divided into three basic categories: (1) absorbing materials, (2) barrier materials, and (3) damping materials. Absorbing materials are generally resistive in nature, either fibrous, porous, or, in rather special cases, reactive resonators. Classic examples of resistive material are fibrous glass, mineral wools, felt, and polyurethane-type foams. Resonators include hollow core masonry blocks, sintered metal (honeycomb backed), etc. Effective barrier materials have one basic common property: dense mass. The most effective barrier materials also have a high degree of internal damping which qualitatively is described as limpness. Sheet lead is the best example of a dense massive limp barrier material. Damping materials are usually relatively thin coatings of plastic polymers, metal, epoxy, or glue which can be adhered to sheet metal panels, gears, machine parts, etc. With these coatings applied, the response of an impact blow to a sheet metal panel is a dull thud rather than a ring. Let us now consider each type in detail.
Q-switched Fiber Laser
Published in Johan Meyer, Justice Sompo, Suné von Solms, Fiber Lasers, 2022
Johan Meyer, Justice Sompo, Sune von Solms
Several applications require a pulsed laser. One of the most effective ways of producing these high-energy pulses is using a Q-switched fiber laser. Q-switching is done by temporarily switching the quality factor of the laser cavity. The quality factor is defined as the ratio between the energy stored in the resonator and the energy lost in a return cycle. In practice, this is done by periodically modulating the losses inside the cavity. High loss corresponds to the low Q-factor of the cavity and low loss corresponds to the high Q-factor of the cavity. When the pump source is switched on, the loss in the cavity is maintained at a high value. Population inversion in the gain medium increases to reach values far beyond threshold values obtainable in the continuous wave regime. After a specific duration, the loss in the cavity is dropped to a minimum value and all the accumulated photons due to population inversion are released in a short time corresponding to several round trips, creating a large pulse at the output of the laser. After releasing the pulse, the loss in the cavity is switched back to a high value and the process is repeated. This is done periodically, releasing a train of pulses. Switching the loss values can be accomplished by using an external switch in the cavity that periodically obstructs the propagation of the photons in the cavity as illustrated in Figure 6.1. This type of Q-switched fiber laser is known as an active Q-switched fiber laser. On the other hand, a saturable absorber can be used to obtain Q-switching. In this case, the transmission property of the saturable absorber is modulated by the propagating field intensity.
Analysis of the quality factor of micro-beam resonators based on heat conduction model with a single delay term
Published in Journal of Thermal Stresses, 2019
Harendra Kumar, Santwana Mukhopadhyay
Based on modern technology, the Micro-Electro-Mechanical Systems (MEMS) and Nano- Electro-Mechanical Systems (NEMS) are being developed due to their various applications in fields of engineering and science such as sensors, micro pumps, accelerometers, charge detectors, radio frequency (RF) filters, and so forth. One of the important application of MEMS is micromechanical resonators for their high sensitivity and fast response. For resonators, it is possible to construct and design systems with very little loss of energy dissipation during vibration. It has been observed that one of the import energy loss factors during vibration is thermoelastic damping in very small structure in size. In order to minimize energy dissipation during the vibration, we need to construct a system with high-quality factor. The quality factor is a dimensionless parameter of a micro resonator and defined as the ratio of the stored energy in the resonator and the dissipated energy by the resonator per cycle of vibration. Quality factor is also commonly termed as the Q-factor. A high value of the quality factor indicates the low rate of energy loss and therefore in such case, oscillations will gradually reduce. This implies that oscillations will ring or vibrate for a long time.
Active Control of Combustion Noise by a Twin Resonator Trim Adjustment System
Published in Combustion Science and Technology, 2022
Varghese M. Thannickal, T. John Tharakan, Satyanarayanan R. Chakravarthy
Variable geometry Helmholtz resonators have been widely used for the active control of acoustic noise (De Bedout et al. 1997; Estève and Johnson 2005; Liu et al. 2007; Nagaya, Hano, Suda 2001). The characteristic frequency of the resonator is tuned to the frequency of the pressure perturbations by varying the dimensions. This makes it possible to precisely achieve optimal damping over a range of operating conditions. The same principle has been used for the trim adjustment active control of thermoacoustic instability. While varying the neck diameter has been investigated (Zhao and Morgans 2009), resonators with variable cavity volume (Thannickal, Tharakan, Chakravarthy 2019; Zhang et al. 2015; Zhao and Li 2012) are easier to realize in practice.
Numerical model & design of wideband band reject filter with closed loop rectangular resonator
Published in International Journal of Electronics Letters, 2023
Neelam Kumari, Meenakshi Sood, Salman Raju Talluri, Sunil Kumar Khah
The present-day communication system requires multifunctional operations with compact size. Multi-functionality extends from performing simultaneous functions to operate in dual band or multi bands. Compact size of the systems is accompanied by complex layouts. The performance of system degrades with the interference due to the presence of multiple signals available from adjacent or nearby systems. In WLAN systems, major interference are in-band signal from 802.11a and 11b working in frequency range of 5–6 GHz and 2.4–2.48 GHz, respectively. For such cases of complex integrated circuits, band stop filters are widely utilised to block interfered signals and suppress spurious harmonics. Filters can be designed and implemented on the circuits of the communication systems inclusively by using transmission lines, microstrip line, stripline, etc. Various methods are utilised for this purpose (Garg et al., 2013; Pozar, 2009). For their inherent advantages, microstrip filters have an edge over other filters (Che et al., 2008). Apart from working as a protection device, microstrip filters are important component of the communication system used in both mobile and satellite applications. To enhance the quality and performance of the advanced communication systems, microstrip resonators are best suited due to their flexible designing. A microstrip design of the filter is widely used in the RF and microwave systems due to low insertion loss and high selectivity. Stepped impedance, coupled lines and ring resonators can be used to design microstrip filters. Microstrip ring resonators are used in applications such as oscillators and antenna. The advantage of ring resonator topology is used in the designing of the bandpass filter.