1 concept
generallyThe stability of the active crystal oscillator is mainly affected by the ambient temperature. The vibration frequency of the vibrating crystal will change accordingly under changing temperature conditions. The constant-temperature crystal vibrator's solution to temperature stability uses constant-temperature bath technology. The crystal is placed in a constant-temperature bath. By setting a constant-temperature working point, the bath is kept at a constant temperature. The output frequency of the vibrator will change due to changes in the surrounding temperature. The amount is reduced to the minimum, and it is not affected by the external temperature within a certain range, achieving the effect of stabilizing the output frequency.
2 principles
The active crystal oscillator is composed of a constant temperature bath control circuit and a vibrator circuit. Usually people use a differential series amplifier composed of a thermistor "bridge" to complete temperature control. The vibration circuit with automatic gain control (AGo) is currently an ideal technical solution to obtain high vibration frequency and stability. Others only place the quartz crystal oscillator in a constant temperature bath, or place the quartz crystal oscillator and related important components in a constant temperature bath. Others place the quartz crystal oscillator in an internal constant temperature bath and place the vibration circuit in the constant temperature bath. Temperature compensation is performed in an external constant temperature bath and a two-layer constant temperature bath control method is implemented.Chip capacitor
3 features
The frequency and temperature characteristics of active crystal oscillators are the best among all types of oscillators. Because the circuit design is precise, its short-term stability and phase noise are better, so constant-temperature crystal oscillators are widely used in various types of communication equipment, including switches, SDH Transmission equipment, mobile communication repeaters, GPS receivers, radio stations, digital electrical transmission equipment, mobile communication repeaters, GPS receivers, radio stations, digital TV and military equipment and other fields. According to user needs, this type of constant temperature crystal oscillator can have voltage control pins. The main disadvantages are high power consumption and large size, and it requires about 5 minutes of heating time to work properly.
