Autoregression Frequency Calibrating

The high accuracy quartz crystal oscillator is an accessible frequency standard. Itsshort-term stability of frequency is between 1×10-10 and 1×10-12, but the frequencychanges in various time scales such as day. month, and year, although it changes veryslowly. The drift of frequency is mainly due to the change of temperature. Fortunately thevoltage to control the frequency can be ajusted when the frequency drift is too big. GPScan also be used as a frequency standard, and its long-term frequency stability is ratherhigh .but the short-term stability is drastically reduced because of various interferencesincluding the SA policy. Many engineers are trying to find ways to combine the features ofquartz crystal oscillator with that of GPS. so as to get good results in both short-termand long-term stabilities. This goal can be abtained by the method put forward in thispaper and the tests show that the frequellcy accurary can reaeh the orders of 10-11 for sucha quartz crystal oscillator controlled by GPS.