Method of calibrating PLL frequency synthesizers to precise frequencies with low tolerance crystals in their master reference oscillators
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United States of America Patent
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Jun 5, 2007
Grant Date -
Jan 1, 2004
app pub date -
Jun 27, 2002
filing date -
Jun 27, 2002
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A frequency tracking circuit and method comprising a master crystal oscillator circuit is used for frequency tracking between a handset and a base station comprising a calibration subsystem for taking a temperature measurement, a reference control circuit for determining a numerical value needed to align a handset frequency with a base station frequency, an adder for adding the numerical value to a previous numerical value determined by the reference control circuit, a latch for latching the output of the adder, and a low precision master crystal oscillator for clocking the frequency of the latch. The most significant bit from the latch is input into a phase/frequency detector for forcing a voltage controlled oscillator to track a desired frequency.
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