AD8341-EVAL Analog Devices Inc, AD8341-EVAL Datasheet - Page 12

• Manufacturer Part Number: AD8341-EVAL
• Manufacturer: Analog Devices Inc

Specifications of AD8341-EVAL

• Lead Free Status / Rohs Status: Not Compliant

AD8341
APPLICATIONS
USING THE AD8341
The AD8341 is designed to operate in a 50 Ω impedance
system. Figure 30 illustrates an example where the RF input is
driven in a single-ended fashion while the differential RF out-
put is converted to a single-ended output with an RF balun. The
baseband controls for the I and Q channels are typically driven
from differential DAC outputs. The power supplies, VPRF and
VPS2, should be bypassed appropriately with 0.1 µF and 100 pF
capacitors. Low inductance grounding of the CMOP and CMRF
common pins is essential to prevent unintentional peaking of
the gain.
RF INPUT AND MATCHING
The input impedance of the AD8341 is defined by the charac-
teristics of the polyphase network. The capacitive component of
the network causes its impedance to roll-off with frequency
albeit at a rate slower than 6 dB/octave. By using matching
inductors on the order of 1.2 nH in series with each of the RF
inputs, RFIP and RFIM, a 50 Ω match is achieved with a return
QBBM
INPUT
QBBP
IBBM
IBBP
VP
RF
VP
0.1µF
C3
100pF
100pF
C6
C5
C8
0.1µF
100pF
C4
1.2nH
1.2nH
L3
L4
C7
100pF
VPRF
CMRF
RFIM
RFIP
CMRF
VPRF
(SEE TEXT)
(SEE TEXT)
IFLP
C12
C11
AD8341
Figure 30. Basic Connections
100pF
Rev. 0 | Page 12 of 20
C2
VP
C9
100pF
DSOP
VPS2
CMOP
CMOP
CMOP
CMOP
RFOM
RFOP
C1
0.1µF
C10
0.1µF
loss of >10 dB over the operating frequency range. Different
matching inductors can improve matching over a narrower
frequency range. The single-ended and differential input
impedances are exactly the same.
The RFIP and RFIM should be ac-coupled through low loss
series capacitors as shown in Figure 29. The internal dc levels
are at approximately 1 V. For single-ended operation, one input
is driven by the RF signal while the other input is ac grounded.
120nH
L1
RF
VP
Figure 29. RF Input Interface to the AD8341 Showing
A
B
Coupling Capacitors and Matching Inductors
OUTPUT
DISABLE
50Ω
C14
0.1µF
L2
120nH
100pF
100pF 1.2nH
100pF
100pF ETC1-1-13
VP
C18
C17
1.2nH
RFIM
RFIP
~1VDC
RF
OUTPUT
PHASE
RC