ADF4360-5BCPZRL7 View Datasheet(PDF) - Analog Devices
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ADF4360-5BCPZRL7 Datasheet PDF : 24 Pages
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ADF4360-5
APPLICATIONS
DIRECT CONVERSION MODULATOR
Direct conversion architectures are increasingly being used to
implement base station transmitters. Figure 17 shows how ADI
parts can be used to implement such a system.
The circuit block diagram shows the AD9761 TxDAC® being
used with the AD8349. The use of dual integrated DACs, such
as the AD9761 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 local oscillator is implemented using the ADF4360-5. The
low-pass filter was designed using ADIsimPLL for a channel
spacing of 200 kHz and an open-loop bandwidth of 10 kHz.
The LO ports of the AD8349 can be driven differentially from
the complementary RFOUTA and RFOUTB outputs of the
ADF4360-5. This gives better performance than a single-ended
LO driver and eliminates the often necessary use of a balun to
convert from a single-ended LO input to the more desirable
differential LO inputs for the AD8349. The typical rms phase
noise (100 Hz to 100 kHz) of the LO in this configuration is 1.09°.
The AD8349 accepts LO drive levels from −10 dBm to 0 dBm.
The optimum LO power can be software programmed on the
ADF4360-5, which allows levels from −13.5 dBm to −4.5 dBm
from each output.
The RF output is designed to drive a 50 Ω load but must be
ac-coupled, as shown in Figure 17. 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
AD9761
TxDAC
IOUTA
IOUTB
QOUTA
QOUTB
2kΩ
VVCO
LOCK
VDD
DETECT
LOW-PASS
FILTER
LOW-PASS
FILTER
10µF
6
21
2 23
20
VVCO DVDD AVDD CE MUXOUT VTUNE 7
14
1nF 1nF
CN
CP 24
8.2kΩ
FREFIN
16 REFIN
51Ω
10nF
8200pF
17 CLK
18 DATA
19 LE
ADF4360-5
VVCO
4.3kΩ
1nF
4.7kΩ
12 CC
13 RSET
CPGND
13
RFOUTA 4
AGND
DGND RFOUTB 5
8 9 10 11 22 15
47nH
47nH
270pF
3.9pF 5.1nH
3.9pF 5.1nH
IBBP
VPS1
IBBN
VPS2
QBBP
AD8349
QBBN
LOIP
PHASE
LOIN SPLITTER
100pF
TO
RF PA
Figure 17. Direct Conversion Modulator
Rev. A | Page 20 of 24
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