Max2108 direct-conversion tuner ic – Rainbow Electronics MAX2108 User Manual
Page 9
MAX2108
Direct-Conversion Tuner IC
_______________________________________________________________________________________
9
MHz
DESIRED
CHANNEL
(20Msps)
dBc
AT POINT
0
0
10
PASSBAND FILTER REQUIREMENTS:
(1) <20% OF BAUD PERIOD DELAY RIPPLE
(2) <0.1dB GAIN RIPPLE
TRANSITION BAND FILTER REQUIREMENTS:
< 2dB GAIN RIPPLE
FILTER CUTOFF
12
20
28
40 MHz
17.16
-30
ADC SAMPLING
TRANSPONDER SPACING = 29.16 MHz
LOWPASS FILTER RESPONSE
DESIRED
CHANNEL
(20Msps)
UNDESIRED ADJACENT CHANNEL
TRANSPONDER BW = 24MHz
dBc
AT POINT
0
1
0
10
DATA NYQUIST
NYQUIST FOR ADC
α
= 0.2
12
20
29.16
40 41.16
17.16
-30
ADC SAMPLING
MHz
DESIRED
CHANNEL
(20Msps)
ADJ
CHANNEL
FOLDOVER
dBc
AT POINT
0
0
10
ADC NYQUIST
12
20
40
17.16
-30
ADC SAMPLING
MHz
DESIRED
CHANNEL
(20Msps)
FOR POINTS 1, 2, 3, 4, REFER TO FIGURE 1
DIGITAL MATCHED FILTER
dBc
AT POINT
0
10 12
40
-30
ADC SAMPLING
2
3
4
Figure 2. Lowpass Filtering Example
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