0.8 GHz to 2.5 GHz
Quadrature Modulator
AD8346
Rev. A
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FEATURES
High accuracy
1 degree rms quadrature error @ 1.9 GHz
0.2 dB I/Q amplitude balance @ 1.9 GHz
Broad frequency range: 0.8 GHz to 2.5 GHz
Sideband suppression: −46 dBc @ 0.8 GHz
Sideband suppression: −36 dBc @ 1.9 GHz
Modulation bandwidth: dc to 70 MHz
0 dBm output compression level @ 0.8 GHz
Noise floor: −147 dBm/Hz
Single 2.7 V to 5.5 V supply
Quiescent operating current: 45 mA
Standby current: 1 μA
16-lead TSSOP
APPLICATIONS
Digital and spread spectrum communication systems
Cellular/PCS/ISM transceivers
Wireless LAN/wireless local loop
QPSK/GMSK/QAM modulators
Single-sideband (SSB) modulators
Frequency synthesizers
Image reject mixer
FUNCTIONAL BLOCK DIAGRAM
1
2
3
4
5
6
7
8
BIAS
PHASE
SPLITTER
16
15
14
13
12
11
10
9
AD8346
IBBP
IBBN
COM1
COM1
LOIN
LOIP
VPS1
ENBL
QBBP
QBBN
COM4
COM4
VPS2
VOUT
COM3
COM2
05335-001
Figure 1.
GENERAL DESCRIPTION
The AD8346 is a silicon RFIC I/Q modulator for use from
0.8 GHz to 2.5 GHz. Its excellent phase accuracy and amplitude
balance allow high performance direct modulation to RF.
The differential LO input is applied to a polyphase network
phase splitter that provides accurate phase quadrature from
0.8 GHz to 2.5 GHz. Buffer amplifiers are inserted between
two sections of the phase splitter to improve the signal-to-
noise ratio. The I and Q outputs of the phase splitter drive the
LO inputs of two Gilbert-cell mixers. Two differential V-to-I
converters connected to the baseband inputs provide the
baseband modulation signals for the mixers. The outputs of
the two mixers are summed together at an amplifier which is
designed to drive a 50 Ω load.
This quadrature modulator can be used as the transmit mod-
ulator in digital systems such as PCS, DCS, GSM, CDMA, and
ISM transceivers. The baseband quadrature inputs are directly
modulated by the LO signal to produce various QPSK and
QAM formats at the RF output.
Additionally, this quadrature modulator can be used with direct
digital synthesizers in hybrid phase-locked loops to generate
signals over a wide frequency range with millihertz resolution.
The AD8346 comes in a 16-lead TSSOP package, measuring
6.5 mm × 5.1 mm × 1.1 mm. It is specified to operate over a
−40°C to +85°C temperature range and a 2.7 V to 5.5 V supply
voltage range. The device is fabricated on Analog Devices’ high
performance 25 GHz bipolar silicon process.
