Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
2008-05-20
2008-05-20
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
Reexamination Certificate
active
11217915
ABSTRACT:
A method for correcting frequency errors in the local reference frequency crystal oscillator of a GPS receiver begins with a step in which the ordinary temperature response of a crystal is characterized. A hardware circuit is incorporated with that crystal to mirror that same characteristic. A temperature sensor is used to control a compensation applied. The combination outputs a fairly flat temperature response, e.g., near zero delta-frequency change over the operating temperature range. But this flat response has an unknown offset from the true frequency. A next step finds a precision timing reference, such as when the receiver locks onto and tracks GPS satellites. The receiver then knows time precisely and a navigation software can compute the offset accurately. A value is stored for that offset in memory. Such value is thereafter recalled at each cold start and is used by software to remove the expected frequency offset.
REFERENCES:
patent: 5629708 (1997-05-01), Rodal et al.
patent: 6509870 (2003-01-01), Matsushita et al.
patent: 7010307 (2006-03-01), Abraham
Law Offices of Thomas E. Schatzel
Nguyen Nga X
Tarcza Thomas H.
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