Specifications

DTT 7685x
SBU Technology – Tuners ATSC half NIM with Ch 3 / 4 modulator
20 Apr 2007
Preliminary Specification Page 4 / 29
1. Brief description
DTT 7685x is a newly developed ATSC half NIM with ch 3 / 4 modulator to be used in ATSC
digital (VSB & QAM), it consists of:
a. A switch 2 bands RF tuner, which receives NTSC / ATSC signal & down-converts it to
an IF frequency of 44MHz for digital and 45.75MHz for analog IF.
b. A digital IF Stage, which consists of one SAW filters & gain controllable IF amplifiers
and outputs a 1.0Vp-p IF signal with a good IF selectivity.
c. An analog modulator which modulates base-band video and sound to RF channel 3
or 4.
d. An active splitter (optional), which is designed with 50 /50 split, with good signal
handling & also provide sufficient gain compensation for the splitting loss & with right
return loss for cable reception
e. RF switch at TV_OUT (optional) provides good isolation from Ant_IN to TV_OUT at
ch 3 / 4.
2. Block diagram
Sound
Input
Ch3/ 4
select
Ant_IN
TV_OUT
UHF
VHF
H/ L
Input filter
MOPLL
Tuner
WB AGC
IF
AGC
DIF
Active
Splitter
( Switch 2 band)
IF
filter
SAW Driver
SAW
VGA
Digital IF
DC
DC
5V Vt
AS
I
2
C
Video
Input
Ch 3 / 4
modulator
Path
Select
AIF
External
AGC
Optional