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US 2008/0174374 A1Published application
Crystal reference clock and radio localization receiver
AssigneeNemerix SA
InventorAndrew Tozer
Life of this patent
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Abstract
Device and method for temperature compensation in a clock oscillator using quartz crystals, which integrates dual crystal oscillators. The minimal power consumption is achieved through an efficient use of a processor in charge of the synchronisation of the two oscillators. The invention is particularly adapted for the provision of a precise reference clock in portable radiolocalization devices
Claims5
A system for generating a very precise, temperature independent reference frequency for GPS devices, comprising:
- (a) A reference oscillator (Xref)
- (b) A temperature sensitive oscillator (XTemp), being thermally coupled to the reference oscillator
- (c) A processing means mixing and measuring the outputs of (a) and (b)
- (d) A memory means storing the characteristics of oscillation frequencies with respect to temperature
- (e) A Digital Processor computing the frequency deviation of the reference oscillator
- (f) A Numerically controlled oscillator (NCO)
- Whereby
- the combination of the outputs the reference oscillator and the temperature sensitive oscillator provided by the processing means produce a temperature dependent beat frequency whose characteristics are stored in the memory means
- the digital processor derives the frequency deviation of the reference oscillator (Xref), depending on the temperature, from the processing means output by applying a calibration function according to the predetermined values stored in the memory means thanks to a piecewise linear interpolation
- The numerically controlled oscillator adjusts the reference oscillator Xref depending on the output of the digital processor, so that its own output will be stable with temperature
7 more elements
A Method for generating a very precise, temperature independent reference frequency for GPS devices, consisting in:
- Mixing the outputs of a reference oscillator Xref (a), with another temperature sensitive oscillator XTemp (b), in order to obtain a temperature dependent beat frequency BT whose characteristics are well known and stored in a memory means (d)
- Deriving the frequency deviation DF(t) of the reference oscillator Xref (a), depending on the temperature, from BT by applying a calibration function according to the predetermined values stored in (d) thanks to a stepwise linear interpolation
- Adjusting the reference oscillator frequency F(t) by adding the frequency deviation DF(t) in order to obtain a final output frequency stable with temperature
Dependencies are inferred from the claim text.