Reference Oscillator; Pll Ic; Figure 11-4 Diagram Of Pll Ic - Hytera MD78X Service Manual

UHF2 (450-520MHz 45W) Information
11.3.2

Reference Oscillator

X100 is a 19.2MHz TCXO, and its reference frequency is calibrated by the digital-to-analog converter
(U500) for accuracy.
11.3.3

PLL IC

The PLL IC (U100) is a fractional frequency divider. The logic IC U101 and U102 work with the PLL IC
(U100) to achieve locking.
The 19.2MHz frequency generated by the reference oscillator (X100) goes into the PLL IC (U100) for
division, generating the reference frequency. Meanwhile, the frequency generated by VCO goes into
PLL IC (U100) for frequency division. The resulting frequency will be compared with reference
frequency in terms of phase difference in the phase detector. After comparison, the resulting
frequency is converted to CV voltage via the loop filter, to control and lock the frequency.

Figure 11-4 Diagram of PLL IC

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