ADF4110 Analog Devices, ADF4110 Datasheet - Page 22

• Manufacturer Part Number: ADF4110
• Description: Single, Integer-N, 550 MHZ PLL With Programmable Prescaler And Charge Pump
• Manufacturer: Analog Devices

ADF4110/ADF4111/ADF4112/ADF4113
DIRECT CONVERSION MODULATOR
In some applications a direct conversion architecture can be used
in base station transmitters. Figure 11 shows the combination
available from ADI to implement this solution.
The circuit diagram shows the AD9761 being used with the
AD8346. The use of dual integrated DACs such as the AD9761
with specified ± 0.02 dB and ± 0.004 dB gain and offset match-
ing characteristics ensures minimum error contribution (over
temperature) from this portion of the signal chain.
The Local Oscillator (LO) is implemented using the ADF4113.
In this case, the OSC 3B1-13M0 provides the stable 13 MHz
reference frequency. The system is designed for a 200 kHz
channel spacing and an output center frequency of 1960 MHz.
OSC 3B1-13M0
MODULATED
TCXO
NTERFACE
DIGITAL
DIGITAL
DATA
SERIAL
100pF
2k
REF
REFIO
FS ADJ
RF
AD9761
TxDAC
ADF4113
IN
IN
B
R
SET
QOUTB
QOUTA
RF
IOUTA
IOUTB
4.7k
IN
A
CP
51
100pF
910pF
POWER SUPPLY CONNECTIONS AND DECOUPLING
CAPACITORS ARE OMITTED FROM DIAGRAM FOR CLARITY.
3.9k
9.1nF
3.3k
620pF
LOW-PASS
LOW-PASS
FILTER
FILTER
The target application is a WCDMA base station transmitter.
Typical phase noise performance from this LO is –85 dBc/Hz at
a 1 kHz offset.
The LO port of the AD8346 is driven in single-ended fashion.
LOIN is ac-coupled to ground with the 100 pF capacitor and
LOIP is driven through the ac coupling capacitor from a 50 Ω
source. An LO drive level of between –6 dBm and –12 dBm is
required. The circuit of Figure 11 gives a typical level of –8 dBm.
The RF output is designed to drive a 50 Ω load but must be
ac-coupled as shown in Figure 11. If the I and Q inputs are
driven in quadrature by 2 V p-p signals, the resulting output
power will be around –10 dBm.
VCO190-1960T
IBBP
IBBN
QBBP
QBBN
100pF
100pF
LOIN
AD8346
18
LOIP
18
18
100pF
VOUT
100pF
RF
OUT