Samsung SGH-P408 Service Manual page 6

SG H- P408 Circuit Description
5 . Si 4 2 0 0 ( U 9 0 1 )
T h i s c h i p i n t e g r at e s t h r e e d i f f e r e n t i al - i n p u t L N A s .
T h e G SM i n p u t s u p p o r t s t h e E - G SM , D C S i n p u t s u p p o r t s t h e D C S1 8 0 0 , P C S
i n p u t s u p p o r t s t h e P C S1 9 0 0 . T h e L N A
d i f f e r e n t i al o u t p u t SA W f i l t e r s t h r o u g h e t e r n a l L C m at c h i n g n e t w o r k .
I m ag e - r e j e c t m i x e r d o w n c o n v e r t s t h e RF s i g n al t o a 1 0 0 K H z i n t e r m e d i at e
f r e q u e n c y ( I F ) w i t h t h e RF L O f r o m SI 4 1 3 3 T f r e q u e n c y s y n t h e s i z e r .
T h e RF L O f r e q u e n c y i s b e t w e e n 1 7 3 7 .8 ~ 1 9 8 9 .9 M H z .
T h e M i x e r o u t p u t i s am p l i f i e d
am p l i f i e r ( P G A ) , w h i c h i s c o n t r o l l e d b y A G A I N .
T h e q u ad r at u r e I F s i g n al i s d i g i t i z e d w i t h h i g h r e s o l u t i o n A / D c o n v e r t s ( A D C ) .
6 . Si 4 2 0 1 ( U 9 0 0 )
T h e SI 4 2 0 1 d o w n - c o n v e r t s t h e A D C o u t p u t t o b as e b an d w i t h a d i g i t al
1 0 0 K H z q u ad r at u r e L O s i g n al .
D i g i t al d e c i m at i o n an d I I R f i l t e r s p e r f o r m c h a n n e l s e l e c t i o n t o r e m o v e b l o c k i n g
an d r e f e r e n c e i n t e r f ac e s i g n al s . A f t e r c h an n e l s e l e c t i o n , t h e d i g i t al o u t p u t i s
s c al e d w i t h a d i g i t al P G A , w h i c h i s c o n t r o l l e d w i t h t h e D G A I N . D A C s d r i v e a
d i f f e r e n t i al a n al o g s i g n al o n t o t h e RX I P , RX I N , RX Q P , RX QN p i n s t o i n t e r f ac e
t o s t an d ar d an al o g - i n p u t b a s e b an d I C .
2 ) T X P A RT
B as e b an d I Q s i g n a l f e d i n t o o f f s e t P L L , t h i s f u n c t i o n i s i n c l u d e d i n s i d e
o f U 9 0 2 c h i p .
SI 4 2 0 0 c h i p g e n e r a t e s m o d u l at o r s i g n al w h i c h p o w e r l e v e l i s ab o u t 1 .5 d B m
an d f e d i n t o P o w e r A m p l i f i e r ( U 1 0 0 8 ) .
T h e P A o u t p u t p o w e r an d p o w e r r a m p i n g ar e w e l l c o n t r o l l e d b y A u t o
P o w e r C o n t r o l c i r c u i t . W e u s e o f f s e t P L L b e l o w ,
Modulation
Spectr um
w i t h an a n al o g p r o g r a m m ab l e g a i n
200kHz offset
30 kHz bandwidth
400kHz offset
30 kHz bandwidth
600kHz ~ 1.8MHz offset
30 kHz bandwidth
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i n p u t s ar e m at c h e d t o t h e 2 0 0 o h m
GSM
DCS
PCS
GSM
DCS
PCS
GSM
DCS
PCS
2- 2
- 35dBc
- 35dBc
- 35dBc
- 66dBc
- 65dBc
- 66dBc
- 75dBc
- 68dBc
- 75dBc