Tham khảo tài liệu 'an introduction to mems engineering - nadim maluf and kirt williams part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 200 MEM Structures and Systems in RF Applications two free ends meet. An interlocking tongue-in-groove structure aids in alignment and gives a small amount of process tolerance Figure b . The stack coils are electroplated with 5 to 8 um of copper for a low resistance using the gold on both sides as a seed layer. The copper also fills the etch holes and seals the seam where the two halves came together. Finally the photoresist and any remaining release material are removed. Microelectromechanical Resonators A simple mechanical system of a spring with spring constant k and a mass m has a resonant frequency fr - ylk m at which it naturally oscillates if the mass is moved and released see Figure . If an external force drives the mass at this resonant frequency the amplitude of the displacement rapidly grows until limited by losses in the system at steady state the loss is known as damping . When driven at a frequency above or below the resonant frequency the amplitude is smaller. In electronics this is analogous to a series or parallel combination of capacitor and inductor with a small series resistance. As discussed earlier the quality factor Q of a resonant electrical circuit or mechanical device is defined as the ratio of the maximum energy stored during a cycle to the energy lost per cycle. Thus circuits or devices with higher Q values will have larger response . displacement when driven at the resonant frequency see Figure . Such circuits or devices also have a higher response peak and a narrower Massless spring with spring constant k Mass m Damping Displacement Resonant frequency Figure Illustration of a mechanical oscillator consisting of a spring a mass and a damping element that represents mechanical losses. When driven at its natural resonant frequency the amplitude of the oscillation is greatest at lower and higher frequencies the amplitude is smaller. Q maximum energy stored during cycle resonant frequency energy lost per cycle bandwidth
