LG -A230 Service Manual page 34

3. TECHNICAL BRIEF
Figure. 3.4.2 Digital PREDISTORTION with LUXO
The DCXO tuning characteristic should be a first order linear function of the programming word AFC. The
variable capacitance array is a first order linear function of the digital word DIG, which leads to a nonlinear
curve ppm vs. DIG (and also a nonlinear ppm vs. AFC for DIG=AFC). In order to linearize the ppm vs. AFC curve
the implementation of a predistortion is necessary.
To get the wanted linear ppm vs. AFC tuning curve some digital predistortion of the AFC word is required. This
predistortion is performed by the linearization unit for crystal oscillator (LUXO). The LUXO calculates the
corresponding DIG value according to the given AFC value.
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