AD6657ABBCZ AD [Analog Devices], AD6657ABBCZ Datasheet - Page 26

• Manufacturer Part Number: AD6657ABBCZ
• Description: Quad IF Receiver
• Manufacturer: AD [Analog Devices]

33% BW MODE (>60 MHZ AT 184.32 MSPS)
The second bandwidth mode offers excellent noise performance
over 33% of the ADC sample rate (66% of the Nyquist band)
and can be centered by setting the NSR mode bits in the NSR
control register (Address 0x3C) to 001. In this mode, the useful
frequency range can be set using the 6-bit tuning word in the
NSR tuning word register (Address 0x3E).
There are 34 possible tuning words (TW); each step is 0.5% of
the ADC sample rate. The following three equations describe
the left band edge (f
band edge (f
Figure 54 to Figure 56 show the typical spectrum that can be
expected from the
different tuning words.
AD6657A
f
f
f
0
CENTER
1
–100
–120
–140
–100
–120
–140
–20
–40
–60
–80
–20
–40
–60
–80
= f
= f
Figure 55. 33% BW Mode, Tuning Word = 17 (f
0
0
ADC
0
0
0
+ 0.33 × f
= f
1
× .005 × TW
9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50
9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50
), respectively.
0
Figure 54. 33% BW Mode, Tuning Word = 5
+ 0.165 × f
AD6657A
0
ADC
), the channel center (f
ADC
FREQUENCY (MHz)
FREQUENCY (MHz)
in the 33% BW mode for three
THIRD HARMONIC
THIRD HARMONIC
185MSPS
140.3MHz @ –1dBFS
NSR 33% BW MODE, TW = 17
SNR = 71.1dB (72.7dBFS)
SFDR = 91dBc
185MSPS
140.3MHz @ –1dBFS
NSR 33% BW MODE, TW = 5
SNR = 70.9dB (72.5dBFS)
SFDR = 91dBc
CENTER
S
/4 Tuning)
), and the right
Rev. 0 | Page 26 of 36
–100
–120
–140
–20
–40
–60
–80
0
0
9.25 18.50 27.75 37.00 46.25 55.50 64.75 74.00 83.25 92.50
Figure 56. 33% BW Mode, Tuning Word = 17
FREQUENCY (MHz)
THIRD HARMONIC
185MSPS
140.3MHz @ –1dBFS
NSR 33% BW MODE, TW = 17
SNR = 70.9dB (72.5dBFS)
SFDR = 91dBc
Data Sheet