Tham khảo tài liệu 'bishop, robert h. - the mechatronics handbook [crc press 2002] part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | TABLE Summary of Oscillator Types Oscillator Type Quartz TCXO Quartz OCXO Rubidium Commercial Cesium Beam Hydrogen Maser Q 104 to 106 X 106 5 MHz 107 108 109 Resonance Various Various GHz GHz GHz frequency Leading cause of failure None None Rubidium lamp life expectancy 15 years Cesium beam tube life expectancy of 3 to 25 years Hydrogen depletion life expectancy 7 years Stability ơy t T 1 s 1 X 10-8 to 1 X 10-9 1 X 10-12 5 X 10-11 to 5 X 10-12 5 X 10-11 to 5 X 10-12 1 X 10 12 Noise floor 1 X 10-9 1 X 10-12 1 X 10-12 1 X 10 11 1 X 10 15 oy T t 1 to 102 s T 1 to 102 s t 103 to 105 s t 105 to 107 s t 103 to 105 s Aging year 5 X 10-7 5 X 10-9 1 X 10-10 None 1 X 10-13 Frequency 1 X 10 6 1 X 10-8 to 5 X 10-10 to 5 X 10-12 to 1 X 10-12 to offset after 1 X 10-10 5 X 10-12 1 X 10-14 1 X 10-13 warm-up Warm-Up 10 s to 5 min to 5 min to 30 min to 24 h to period 1 X 10 6 1 X 10 8 5 X 10-10 5 X 10-12 1 X 10-12 A quartz crystal inside the oscillator is the resonator. It can be made of either natural or synthetic quartz but all modern devices use synthetic quartz. The crystal strains expands or contracts when a voltage is applied. When the voltage is reversed the strain is reversed. This is known as the piezoelectric effect. Oscillation is sustained by taking a voltage signal from the resonator amplifying it and feeding it back to the resonator. The rate of expansion and contraction is the resonance frequency and is determined by the cut and size of the crystal. The output frequency of a quartz oscillator is either the fundamental resonance or a multiple of the resonance called an overtone frequency. Most high stability units use either the third or fifth overtone to achieve a high Q. Overtones higher than fifth are rarely used because they make it harder to tune the device to the desired frequency. A typical Q for a quartz oscillator ranges from 10 to 10 . The maximum Q for a high stability quartz oscillator can be estimated as Q X
