User Guide

CCS Technical Documentation 7 - System Module & UI

Company Confidential NMM-3

Issue 1 (11/2003) Copyright  2003 Nokia Corporation Page 7-37

Company Confidential

Figure 5: GSM power control loop

GSM receiver

The GSM receiver is a direct conversion, dualband linear receiver. From the antenna the

received RF-signal is first fed to the ASM. Inside the module there is a diplexer which

divides the signal into two separate paths. The lower path is for GSM900 and the upper

for GSM1800. In each of the paths a pin-diode switch is used to select either receive or

transmit mode. The selections are controlled by HELGO, which obtains the mode/band

and timing information through RFBus. After the switch the received signal goes

through a bandpass filter also included in the ASM. The signal is then fed to the inte-

grated LNAs within HELGO.

The LNAs have three gain levels. The first level is for maximum gain, the second is about

30dB below the maximum, and the third is the off state about 50dB below maximum.

The gain selection is controlled via RFBus.

EGSM900 PA

GSM1800 PA

TX_IN

GSM_PA

TXP

TXC

TXP

ERROR

AMPLIFIER

R2 Ctemp

K = -R1/R2

DOMINANT

POLE

DCS_PA

DETECTOR

TX_OUT

DIR COUPLER

det

22K

1p8

68N 68N

33R

3k3

4k7

10pF

3k3