AD6620
A DSP is then used to perform the demodulation of the digital
channel. This has the advantage of allowing for in-system con-
figuration options and can even allow for improved modulation
techniques to be applied in the future. This assumes that the
AD6600 and the circuitry on its front end are compatible with
the modulation standard to be used.
AD6620 #1
CLK
AD6640
AD6644
SERIAL I/O
AIN
LATCH
D
IN
AD6620 #2
CLK
SERIAL I/O
For more information on using the AD6600 and AD6620 in a
Single Carrier application, refer to Analog Devices’ Application
note AN-502.
D
IN
ENCODE
CLOCK
DSP
ARRAY
AD6620 #3
CLK
Using the AD6620 in a Wideband System
SERIAL I/O
D
IN
The AD6620 is fully capable of being utilized in a wide-band
architecture system where A/Ds such as the AD6640 or the
AD9042 usually run at higher sample rates than those typically
found in a narrow-band system. A correspondingly wider band
can then be digitized. The digitization of this wide bandwidth
allows many more channels to be digitized using the same A/D
and IF circuitry. The core configuration of such a system is
shown in Figure 61.
AD6620 #4
CLK
SERIAL I/O
D
IN
Figure 61. Implementation of a Multicarrier Receiver
channel. This places a greater requirement on the Spurious Free
Dynamic Range (SFDR) of the A/D than in the narrow-band
case. The SFDR is then usually the limiting factor of the wide-
band system.
The AD6640 and the AD6620 are both designed to run as fast
as 67 MHz. In these applications the AD6620 will be used to
process only one channel and will process the data at the A/D
sample rate. Additional channels can be processed by taking the
AD6640 high speed data stream to additional AD6620s. Each
AD6620 can then be tuned to a different channel.
Provided that the A/D has sufficient SFDR for the air interface
requirements, the AD6620 can use process gain, as in the narrow-
band case, by filtering the out-of-band noise and adjacent channel
power. This increases the SNR of the digital data stream.
The AD6620 provides a great deal of selectivity by mixing down
a channel of interest as in the narrow-band case and filtering the
out-of-band noise and adjacent channels. Unlike the narrow-
band solutions it is much more difficult to place the spurious
content out of the band of interest because more of this band-
width is used due to the larger number of carrier channels. The
aliased spurs of one channel are likely to fold back on another
As in the Narrow-band System a DSP is then used to demodu-
late the digital data. The same advantages of flexibility exist in
the wide-band case as they did in the narrow-band case. Future
improvements in demodulation algorithms can be implemented
in the receiver, provided that the front end hardware is compat-
ible with the desired modulation standard.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
80-Lead Terminal Plastic Quad Flatpack (PQFP)
(S-80A)
0.690 (17.45)
0.667 (16.95)
0.555 (14.10)
0.547 (13.90)
0.134 (3.40)
MAX
0.486 (12.35) BSC
0.041 (1.03)
0.029 (0.73)
80
61
60
1
SEATING
PLANE
TOP VIEW
(PINS DOWN)
0.004 (0.10)
MAX
20
21
41
40
0.010 (0.25)
MIN
0.026 (0.65) 0.015 (0.38)
BSC
0.120 (3.05)
0.100 (2.55)
0.009 (0.22)
–44–
REV. A
ADI [ ADI ]
