Patent ID: 6362699
Filing Date: 2002-03-26
Classification: H03L

Abstract:
An electrical device to compensate for crystal oscillator frequency shifts in a voltage tunable crystal oscillator occurring over a temperature range, comprising:a) first, second and third voltage dividers responsive to temperature change for generating temperature variable, compensation voltages; b) first, second and third voltage sources to be respectively coupled to inputs of the first, second and third voltage dividers for inputting generally fixed voltages during normal crystal oscillator operation, and providing for multiple and repeatable adjustments to the fixed voltages before beginning the normal crystal oscillator operation, the first through third voltage dividers each including a resistor and negative temperature coefficient thermistor connected in series from the associated voltage source to ground potential to compensate for frequency shift over a respective cold, middle and hot temperature region, each of the thermistors of the first and third voltage dividers being interposed between the associated resistor and ground potential and the thermistor of the second voltage divider being interposed between the associated voltage source and the associated resistor; and c) a summing means for combining compensation signals generated by the voltage dividers to generate a summed control signal for tuning the crystal oscillator such that the output frequency of the crystal oscillator is substantially stable over the cold, middle and hot temperature regions.