The offset oscillator frequency is controlled by U110(ZIF/SYN) via TXCP_OUT. The operating frequency will depend on the dc biasing of CR300. The offset oscillator fre-

quency is 157.32MHz in analog mode, and 112.32MHz in digital mode. The LP_Switch, which comes from U110 pin 40, changes the offset frequency. The LP_Switch is

on in analog mode and off digital mode. The LP-Switch is currently not supported in the TDMA StarTAC, therefore, the frequency of the offset oscillator will be

157.32MHz regardless of whether it is in analog or digital mode.

In analog mode the FM signal comes from U1800(DCI) pin 39 and is modulated directly in the offset oscillator. The offset oscillator with the FM then enters U300(QMOD).

The Quadmod(U300) will feed back the offset frequency to U110 for proper PLL operation.

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