A complete design example is shown in Figure 91. A sixth-order
Butterworth differential filter having a 1.9 MHz corner frequency
interfaces the output of the ADL5380 to that of an ADC input.
The 500 Ω load resistor defines the input impedance of the
ADC. The filter adheres to typical direct conversion W-CDMA
applications where, 1.92 MHz away from the carrier IF frequency,
1 dB of rejection is desired, and, 2.7 MHz away from the carrier IF
frequency, 10 dB of rejection is desired.
Figure 89 and Figure 90 show the measured frequency response
and group delay of the filter.
10
5
0
–5
–10
–15
–20
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
FREQUENCY (MHz)
Figure 89. Sixth-Order Baseband Filter Response
ADL5380
900
800
700
600
500
400
300
200
100
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
FREQUENCY (MHz)
Figure 90. Sixth-Order Baseband Filter Group Delay
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