Key words: crystal crystal crystal fundamental classification
    (TCXO), voltage-controlled crystal vibrators (VCXO), thermostatically controlled crystal vibrators (OCXO) and digitized / μp compensated crystal vibrators (TCXO), temperature-controlled crystal vibrators (TCXO), voltage-controlled crystal vibrators DCXO / MCXO) and so on several varieties. In the meantime, the temperature-free crystal oscillator is the most simple one, in the Japanese Industrial Standard (JIS), called the standard package

Crystal vibrator (SPXO).
    The quartz crystal vibrator is a resonant device made of a piezoelectric effect of quartz crystal (a crystal of silica), which is constructed substantially from a quartz crystal by a certain azimuth cut sheet (referred to as a wafer, which Can be square, rectangular or circular, etc.), in its two corresponding surface coated with silver layer as the electrode, in each electrode on a welding lead to the pin, coupled with the package shell to form Quartz crystal resonator, referred to as quartz crystal or crystal, crystal. Its products are usually packaged in metal shells, also useful glass shell, ceramic or plastic package. Quartz Crystal Piezoelectric Effect: If an electric field is applied to both electrodes of a quartz crystal, the wafer undergoes mechanical deformation. Conversely, if mechanical pressure is applied on both sides of the wafer, an electric field will occur in the corresponding direction of the wafer, which is called the piezoelectric effect. Note that this effect is reversible. If the alternating voltage on the north and south poles of the chip, the chip will occur mechanical vibration, together with the mechanical vibration of the wafer will occur alternating electric field. Under normal circumstances, the amplitude of the mechanical vibration of the wafer and the amplitude of the alternating electric field are very small, but when the frequency of the applied alternating voltage is a specific value, the amplitude is significantly increased, much larger than the amplitude at other frequencies , Which is called piezoelectric resonance, which is very similar to the resonant scene of the LC loop. Its resonant frequency is related to the cutting of the wafer, the shape of the dice, the scale, and so on.

    The temperature-compensated crystal vibrator (TCXO) is a quartz crystal vibrator that reduces the amount of vibration frequency change caused by changes in ambient temperature via an additional temperature compensation circuit. TCXO, the quartz crystal oscillator frequency temperature drift compensation methods are the main direct compensation and direct compensation of two varieties:
Quartz crystal vibrator
⑴ direct compensation type directly compensated TCXO is composed of thermistor and RC components of the temperature compensation circuit, in the vibrator and quartz crystal oscillator in series made of. In the temperature change, the thermistor resistance and crystal equivalent series capacitance corresponding changes, and then offset or reduce the vibration frequency of the temperature drift.
Not suitable for
   The voltage-controlled crystal vibrator (VCXO) is made by applying an external control voltage to make the vibration frequency variable

Or a quartz crystal vibrator that can be modulated. In a typical VCXO, the tuning voltage is usually changed

The capacity of the varactor diode to "traction" the quartz crystal oscillator frequency. VCXO allows frequency control scale

Relatively wide, the practice of traction scale is about ± 200ppm or even greater. If the VCXO request frequency is requested

Than the quartz crystal oscillator can complete the frequency even higher, the choice of multiplier program. Expand the tuning of the other

One way is to mix the output signal of the crystal vibrator with the output signal of the VCXO. With a single vibrator

In comparison, this heterodyne two vibrator signal tuning scale has significantly expanded.