User Guide

TME-3 Company Confidential

Data Module RL7 PAMS Technical Documentation

Page 24 Nokia Corporation. Issue 4 12/03

Frequency synthesizers

VCO frequency is locked with PLL into stable frequency source, which is a VCTCXO-mod-

ule. VCTCXO is running at 26 MHz. Temperature drifting is con trolled with AFC voltage.

VCTCXO is locked into frequency of the base station. AFC is generated by baseband with

a 11 bit conventional DAC. 13MHz VCTCXO can also be used if multislot operations is not

needed.

Figure 12: Phase Locked Loop, PLL

PLL is located in HAGAR RF-IC and is controlled via serial RFBus. There is 64/65 (P/P+1)

prescaler, N- and A-divider, reference divider, phase detector and charge pump for the

external loop filter. SHF local signal, generated by a VCO-module, is fed through a

180deg balanced phase shifter to prescaler. Output of the prescaler is fed to N- and A-

divider, which produces the input to phase detector.

Phase detector compares this signal to reference signal (400kHz), which is divided with

reference divider from VCTCXO output. Output of the phase detector is connected into

charge pump, which charges or discharges integrator capacitor in the loop filter depend-

ing on the phase of the measured frequency compared to reference frequency.

Loop filter filters out comparison pulses of phase detector and generates DC control volt-

age to VCO.

Dividers are controlled via serial bus. RFBus Data is for data, RFBusClk is serial clock for

the bus and RFBusEna1X is a latch enable, which stores new data into dividers.

LO-signal is generated by SHF VCO module. VCO has double frequency in GSM1800 and x

4 frequency in EGSM compared to actual RF channel frequency. LO signal is divided by

two or four in HAGAR (depending on system mode).

Receiver

Receiver is a direct conversion, dual band linear receiver. Received RF-signal from the

antenna is fed via a RF-antenna switch module to the 1st RX bandpass RF-SAW filters

and MMIC LNAs. RF-antenna switch module contains upperband and lowerband opera-

VCO

CHARGE

PUMP

PHASE

DET.

f_out

Kvco

M = A(P+1) + (N-A)P=

ref

f_out /

26 MHz frequency reference

= NP+A

AFC-controlled VCTCXO