Information and Communication Products
Mobile Phones
Service Manual S25 / S2588
V 1.0
ICP CD ST
R. Fleuren
Sm_S25_lvl2_v11
Page
19
of 35
06/99
5.2
Hardware Description
The handset consists of the following major integrated circuits:
1)
HiGOLD (PMB 2800)
This IC is a combination of microprocessor and signalprocessor.
The microprocessor part of this component is responsible for controlling the keyboard, SIM-
Card, Flash and RAM. Furthermore it controls the power up/power down of the RF module
and sets the amplification of the PA.
The signal processor part of PMB 2800 is responsible for processing the Rx I/Q signals
(filtering, equalizing, speech and channel decoding).
Furthermore it does the speech and channel encoding and the GSMK modulation of the Tx
I/Q signals.
2) GOLD-SX (PMB 2709)
The coprocessor PMB 2709 is used to realize advanced features regarding coding of the
speech signal. These are:
•
Halfrate-Encoding
•
Halfrate-Decoding
•
Enhanced Fullrate Encoding
•
Enhanced Fullrate Decoding
•
Voice Activity Detection
•
Comfort Noise
3) GAIM (PMB 2905)
The GAIM (GAIM =
G
SM
A
nalog
I
nterfacing
M
odule) provides the interface between the
analogue signals (I/Q, voiceband, PA-control, charging control signals) and its digital
representation.
4) Receiver Circuit (PMB 2411)
This circuit provides the following main functionalities:
•
Low Noise Amplifier (LNA) with a fixed amplification of +20dB to amplify the input
RF signal.
•
Mixer to mix down the RF signal to the Intermediate Frequency (IF)
•
Programmable IF amplifier with a dynamic range of 60dB ( -10dB ... +50dB in steps of
2dB).