EVAL-ADF4151EB1Z 查看數據表（PDF） - Analog Devices
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EVAL-ADF4151EB1Z Datasheet PDF : 28 Pages
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ADF4151
APPLICATIONS INFORMATION
DIRECT CONVERSION MODULATOR
Direct conversion architectures are increasingly being used to
implement base station transmitters. Figure 29 shows how Analog
Devices, Inc., parts can be used to implement such a system.
The circuit block diagram shows the AD9788 TxDAC® being
used with the ADL5375. The use of dual integrated DACs, such
as the AD9788 with its specified ±0.02 dB and ±0.004 dB gain
and offset matching characteristics, ensures minimum error
contribution (over temperature) from this portion of the
signal chain. The signal for the I channel of the quadrature
modulator is taken from the OUT1 differential outputs of the
AD9788, and the OUT2 differential outputs provide the signal
for the Q channel of the quadrature modulator ADL5375.
The local oscillator (LO) is implemented using the ADF4151.
The low-pass filter was designed using ADIsimPLL™ for a channel
spacing of 200 kHz and a closed-loop bandwidth of 35 kHz.
Data Sheet
The LO ports of the ADL5375 can be driven from the VCO
output. To ensure that all three RF ports (VCO output, RFIN and
LOIP) are connected to 50 Ω impedance, the matching network
of three 18 Ω resistors must be placed as in Figure 29. AC
coupling of the RF signal is implemented by the capacitors
connected in serial with the 18 Ω resistors . It is possible, as
well, to use a balun to convert from a single-ended LO input to
the differential LO inputs for the ADL5375.
If the I and Q inputs are driven in quadrature by 2 V p-p
signals, the resulting output power from the modulator is
approximately 2 dBm.
REFIO
MODULATED
DIGITAL
DATA
FSADJ
2kΩ
51Ω
OUT1_P
AD9788
TxDAC
OUT1_N
OUT2_P
OUT2_N
51Ω
51Ω
LOW-PASS
FILTER
LOW-PASS
FILTER
51Ω
VDD
VP
LOCK
DETECT
FREFIN
10
16
17 4 28 32 6
30
25
AVDD1 AVDD2
1nF 1nF
29 REFIN
51Ω
1 CLK
AVDD2
CE DVDD SDVDD VP
MUXOUT LD
RFIN+ 14
RFIN– 15
2 DATA
3 LE
4.7kΩ
22 RSET
ADF4151
CPOUT 7
100pF 18Ω
18Ω 1nF
100pF
18Ω
100pF
VVCO
VCOOUT
VCC
VTUNE
1nF
VCO
680Ω
CPGND AGND
8
9
AGND
11
AGND
18
AGND
21
DGND
26
SW 5
DGND SDGND
27
31
2700pF
39nF
360Ω
1200pF
Figure 29. Direct Conversion Modulator
IBBP
IBBN
ADL5375
LOIP
LOIN
QUADRATURE
PHASE
SPLITTER
QBBP
QBBN
RFOUT
DSOP
Rev. B | Page 24 of 28
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