AD6649 Analog Devices, AD6649 Datasheet - Page 25

• Manufacturer Part Number: AD6649
• Description: IF Diversity Receiver
• Manufacturer: Analog Devices

Data Sheet
Figure 43. High Performance FIR Filter Pass-Band Response at 245.76 MSPS
Figure 44. High Performance FIR Filter Pass-Band Response at 245.76 MSPS
–100
–110
–120
–0.1
–0.2
–0.3
–0.4
–0.5
–0.6
–0.7
–0.8
–0.9
–1.0
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
0
0
0
(Tunable-Frequency NCO, 100 MHz FIR Filter)
(Tunable-Frequency NCO, 100 MHz FIR Filter)
30.72
15.36
FILTER RESPONSE (MHz)
FILTER RESPONSE (MHz)
61.44
30.72
92.16
46.08
122.88
61.44
Rev. A | Page 25 of 40
OUTPUT NCO
The output of the 32-bit fine-tuning NCO is complex and
typically centered in frequency around dc. This complex output
is carried through the stages of either the 95 MHz or 100 MHz FIR
filter to provide proper antialiasing filtering. The final NCO
provides a means to move this complex output signal away from
dc so that a real output can be provided from the AD6649. The
output NCO translates the output from dc to a frequency equal
to the output frequency divided by 4 (f
with an output signal centered at f
The AD6649 output NCOs within a single part or across
multiple parts can be synchronized using the external SYNC
input. Bit 7 and Bit 6 of Register 0x58 allow the output NCO to
be resynchronized on every SYNC signal or only on the first
SYNC signal after the register is written.
S
/4 in frequency.
S
/4). This provides the user
AD6649