Vibration modes for a variety of crystal element, wherein the thickness shear use more. For the thickness-shear mode, press the azimuth and angle wafer dicing mainly AT-cut and BT-cut. AT-cut having good temperature characteristics and are widely used.
      Vibration mode crystal elements are pitch-mode (commonly known as the fundamental frequency) and the overtone mode.
      Pitch (fundamental frequency) crystal transducer element is designed to operate in the lowest order of the selected vibration mode. The overtone crystal oscillator components are designed to work at higher than the lowest order of the selected vibration mode Order.
      That is a given vibrational modes of the crystal element there baseband (minimum orders), three times overtone (nearly three times the fundamental frequency), five times overtone (nearly 5 times the fundamental frequency) and higher frequency harmonics times .
      Typically the base frequency to obtain a crystal element in a relatively wide frequency bandwidth and a relatively small resonant resistance. Load capacitance can be achieved by using a wide frequency adjustment range is more suitable for the manufacture VCO and PLL locking circuit. And used to make filters. However, to obtain a relatively low frequency (typically below 30MHz).
      The overtone crystal can work in three times, five times, seven times lower overtone vibration mode, can obtain a higher frequency. When the load capacitance and thus constitute a high degree of stability oscillator greater use by the stray capacitance of the external circuit oscillator frequency pulling range is relatively much smaller, while the aging rate overtone crystal element lower than the fundamental frequency, overtone crystal element.
     Under normal circumstances, quartz crystal components not specifically take measures to control the fundamental frequency resonant vibrational modes of resistance will be less than the resonance resistance overtone modes. Therefore, during the oscillator circuit design, while using crystal element baseband frequency selection mode without additional circuits, and in the use of overtone crystal oscillator elements, shall take appropriate measures (such as increasing the frequency selective circuit) ensure that the oscillator except needed to gain a higher frequency harmonic frequency outside the frequency range of the other lower gain.