Synthesizer: Lo2 - Siemens S55 Repair Documentation

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4.2.3

Synthesizer: LO2

The second local oscillator is required for transmitter operations only. It consists of a

PLL and a VCO which are integrated inside the Bright 4, and an external second order

loopfilter

(R831; C830;

arrives at the modulator, it is divided by 8. So the resulting frequency after the IQ

modulator is 80/82MHz (depending on channel and band). Programming of the LO2

PLL is done in the same way as described at the LO1. The tree-wire-bus (EGOLD+

signals RFDATA; RFCLK; RFSTR.

frequency stability, the 640MHz VCO signal is compared by the phase detector of the

PLL with the 26MHz reference signal. The resulting control signal passes the

external loop filter and is used to control the 640/656MHz VCO.

The required voltage

VCC_SYN

Circuit diagram

V1.00

S55/S57

C832). Before the VCO generated 640 or 656MHz signal

(RF Control J15, J16, J17)

is provided by the ASIC

Page 12 of 49

is used. To ensure the

D361

Loop-filter LO2

ICM MP CCQ GRM

12/02

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S57