Samsung SGH-600 Service Manual page 8

Circuit Description
2-1-3 Receiver
The incoming RF signal passes through the integrated lowpass filter and TX/RX switch. This is followed by a
947 MHz SAW Band Pass Filter and a bipolar low-noise amplifier (LNA). The HD155101BF includes an active
bias circuit which stabilizes the DC operating point of the LNA. The RF signal passes via a second RF SAW
filter to the first receive mixer. This mixer is implemented as a Gilbert cell within the HD155101BF. The
incoming signal at 947 MHz mixes with the UHF LO at 1172 MHz to generate a 225 MHz IF signal. The IF
signal passes from the mixer output via a 225 MHz IF SAW filter to the first IF amplifier. A further internal
Gilbert cell mixes the 225 MHz IF signal down to the 45 MHz second IF. The 45 MHz output from the second
mixer is filtered and passes to the AGC amplifier. The gain of the AGC amplifier is set by a DC control voltage
supplied by the baseband. The usable control range is in excess of 80dB. Finally, the AGC output signal at 45
MHz passes to the demodulator and is mixed down to DC to generate I and Q baseband signals. The baseband
signals pass via baseband filter to the baseband A/D converters. The remainder of the channel filtering is
performed by the baseband chipset.
2-2 Baseband Part
2-2-1 General Block Diagram
SERIAL
EEPROM
VIBRATOR
VOCODER
2-2
cmd
B.B. FILTER
clk
power
cmd
eepdata
Vcel.
KERNEL
Vther.
Vib
voice data
cmd
add
data
audio
dai
< Fig. 3 Baseband Block Diagram >
I,Q Rx
Vmid
I,Q Tx
RS232
3V/ 5V
TRANSLATOR
SIM
keyboard
synth.cmd
radio.cmd
cmd
MEMORY
(Flash1 + SRAM)
add
Flash2
data
(Voice recognition)
(Voice recognisation)
Earphone (Spk/Mic)
Spk/Mic
SIM
SIM I/F
Samsung Electronics