adl5382 Analog Devices, Inc., adl5382 Datasheet - Page 18

• Manufacturer Part Number: adl5382
• Description: 700 Mhz To 2.7 Ghz Quadrature Demodulator
• Manufacturer: Analog Devices, Inc.

ADL5382
As an example, a second-order Butterworth, low-pass filter
design is shown in Figure 50 where the differential load impedance
is 500 Ω and the source impedance of the ADL5382 is 50 Ω. The
normalized series inductor value for the 10-to-1, load-to-source
impedance ratio is 0.074 H, and the normalized shunt capacitor
is 14.814 F. For a 10.9 MHz cutoff frequency, the single-ended
equivalent circuit consists of a 0.54 µH series inductor followed
by a 433 pF shunt capacitor.
The balanced configuration is realized as the 0.54 µH inductor
is split in half to realize the network shown in Figure 50.
A complete design example is shown in Figure 53. A sixth-order
Butterworth differential filter having a 1.9 MHz corner frequency
interfaces the output of the ADL5382 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 10 dB of rejection
is desired.
V
V
V
S
S
S
Figure 50. Second-Order Butterworth, Low-Pass Filter Design Example
R
R
S
L
= 0.1
R
R
R
R
S
2
2
S
S
S
= 50Ÿ
= 50Ÿ
= 25Ÿ
= 25Ÿ
CONFIGURATION
CONFIGURATION
DENORMALIZED
SINGLE-ENDED
SINGLE-ENDED
NORMALIZED
EQUIVALENT
L
BALANCED
N
0.54µH
0.27µH
0.27µH
= 0.074H
C
N
14.814F
433pF
433pF
f
C
f
R
R
R
C
R
2
2
= 10.9MHz
L
L
L
L
= 1Hz
= 500Ÿ
= 500Ÿ
= 250Ÿ
= 250Ÿ
Rev. 0 | Page 18 of 28
Figure 51 and Figure 52 show the measured frequency response
and group delay of the filter.
–10
–15
–20
900
800
700
600
500
400
300
200
100
10
–5
5
0
0
0
Figure 52. Sixth-Order Baseband Filter Group Delay
Figure 51. Sixth-Order Baseband Filter Response
0.2
0.5
0.4
1.0
0.6
FREQUENCY (MHz)
FREQUENCY (MHz)
1.5
0.8
1.0
2.0
1.2
2.5
1.4
1.6
3.0
1.8
3
.5