Oscillators – With frequency calibration or testing
Patent
1993-09-30
1995-02-21
Grimm, Siegfried H.
Oscillators
With frequency calibration or testing
331158, 331176, H03L 100
Patent
active
053920058
ABSTRACT:
Solving the aging problem of crystal oscillators by doing field recalibration. The solution is to utilize an accurate external reference signal to determine when the frequency of the digital temperature compensated crystal oscillator (DTCXO) has drifted from the reference signal in excess of a specification. When this occurs, the DTCXO has used its internal compensation values to correct its output hence the difference between the external reference signal and the frequency of the DTCXO in excess of the specification is due to aging. A new compensation value for the present temperature is calculated using the reference signal. Using the well known fact that the temperature aging uniformly shifts the frequency over the temperature range, a controller utilizes the difference between the new compensation value and the stored compensation value for the present temperature to shift the entire set of compensation values to compensate for the aging effect.
REFERENCES:
patent: 4746879 (1988-05-01), Ma et al.
patent: 4922212 (1990-05-01), Roberts et al.
patent: 4930142 (1990-05-01), Whiting et al.
patent: 5041798 (1991-08-01), Moorman et al.
Bortolini James R.
Grimes Gary J.
AT&T Corp.
Grimm Siegfried H.
Moran John C.
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