Model No: 3390 Drawring No:
Customer :
Title
M-490 Plus
Rev,Date:
4. FREQUENCY STABILITY
LET : Fo = Crystal oscillator frequency
Fr = Phase detector reference frequency
Fvco = VCO frequency
Ft = Transmit frequency
Then : Fr = Fo/1800
And under locked conditions : Fr = Fvco / N
WHERE, “N” is the programmable divider divide ratio.
THEN : Fvco = N X Fr
From which it can be seen, the percentage error in Ft is the same as the percentage error in Fo. The
stability of the crystal oscillator is determined primarily by the crystal itself and having lesser deviation
by the active and passive components of the oscillator. The choice of crystal and component is such
that the required frequency stability is maintained over the required voltage
and temperature rang.
Created by: Approved by: Rev.No:
For Stage: Release Date: Page: 24 / 61
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