The Improvement Of Temperature-frequency Characteristics Of Crystal Oscillator

Based on the study of the temperature-frequency and force-frequency characteristic, this article presents such temperature compensation methods: First, combined with the temperature-frequency and the force-frequency characteristics of the crystal, we get the temperature compensated effect of overtone crystal oscillator recur to the thermal stress of metallic electrode making these two characteristics work on each other The theory foundation and realization of the compensation are given in detail, and the basis how to choose the interrelated parameters during the whole realization processing with this new method are offered by experiments, we find our theory have great effect, we can get high frequency stability. To normal crystal resonator, we can make it eliminate 10ppm, to crystal resonator, we can even make it decrease to±4ppm between -40~75 centigrade, it has very small difference with resonator which compensate with circuit has±2ppm. Second, this paper introduces the basic principle of the secondary compensation, the design including analog part and digit part, the whole system and the use of microcomputer and some core technology such as compensation wave and curve fitting replaces some big, expensive and high-power hardware. This oscillator not only retains TCXO merits of small in size and low in power, but also gets high frequency-temperature stability and fine phase noise quality. We get a high frequency stability of±0.28ppm between–40~75 centigrade. Phase noise label: frequency offset 1Hz <= -75 dBc, frequency offset 1KHz <= -145dBc.