CN-0283 Datasheet, PDF (1/6 Pages) Analog Devices – Providing Fixed Power Gain at the Output of an IQ Modulator

Circuit Note
CN-0283
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0283.
Devices Connected/Referenced
ADL5375
400 MHz to 6 GHz Broadband Quadrature
Modulator
ADL5320
400 MHz to 2700 MHz ¼ Watt RF Driver
Amplifier
Providing Fixed Power Gain at the Output of an IQ Modulator
EVALUATION AND DESIGN SUPPORT
Circuit Evaluation Boards
ADL5375 Evaluation Board (ADL5375-05-EVALZ)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
Whether an IQ modulator is used in a direct conversion
application or as an upconverter to a first intermediate frequency
(IF), some gain is generally applied directly after the IQ modulator.
How to choose an appropriate driver amplifier to provide the
first stage of gain at the output of an IQ modulator will be
described. The devices shown in Figure 1 are the ADL5375
IQ modulator and the ADL5320 driver amplifier. They are well
matched from a system performance level; that is, they have
equivalent performance so neither device contributes to
degradation in the overall performance. Because these devices are
well matched in terms of their dynamic ranges, a simple direct
connection between the IQ modulator and the RF driver
amplifier is recommended without any need for attenuation
between the devices.
+5V
+5V
C5
0.1µF
C3
100pF
C2
100pF
C4
0.1µF
IP
VPS2
24
VPS1
18
R7
100Ω
IBBP
21
IBBN
22
U1
AD L537 5
+5V
C9 10µF
(2)
U2 ADL5320
C10 10nF
C11 22pF
IN
LO
QN
C6
100pF _LOIP
3
LOIN
4
C7
100pF
R12
100Ω
QBBN
9
QBBP
10
QUADRATURE
PHASE
SPLITTER
RFOUT
16
L1
1
2
3
15nH
C12
λ1
λ2
λ3
λ4 ^{22pF AMP_OUT}
C1
100pF
C100 (C3)
0.5pF
C101 (C7)
1.5pF
DSOP
1
NOTE: SEE ADL5320 DATA SHEET FOR COMPONENT SPACING (λ) VALUES
2 5 8 11 12 17 19 20 14 23 6 7 13 15
COMM
QP
NC
Figure 1. Circuit Schematic for IQ Modulator with Output Power Gain
Rev. 0
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