ADF4360-4BCPRL Просмотр технического описания (PDF) - Analog Devices
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ADF4360-4BCPRL Datasheet PDF : 24 Pages
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ADF4360-4
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 ADF4360-4. 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
ADF4360-4. 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
ADF4360-4, which allows levels from −13 dBm to −4 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
FREFIN
16 REFIN
51Ω
1nF
1nF
4.7kΩ
17 CLK
18 DATA
19 LE
12 CC
13 RSET
CPGND
13
ADF4360-4
VVCO
47nH
RFOUTA 4
AGND
DGND RFOUTB 5
8 9 10 11 22 15
6.8kΩ
12nF
3.9kΩ
330pF
47nH
1.8pF 5.1nH
1.8pF 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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