1.5 GHz to 2.4 GHz

RF Vector Modulator

AD8341

Rev. 0

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FEATURES

Cartesian amplitude and phase modulation

1.5 GHz to 2.4 GHz frequency range

Continuous magnitude control of −4.5 dB to −34.5 dB

Continuous phase control of 0° to 360°

Output third-order intercept 17.5 dBm

Output 1 dB compression point 8.5 dBm

Output noise floor −150.5 dBm/Hz @ full gain

Adjustable modulation bandwidth up to 230 MHz

Fast output power disable

4.75 V to 5.25 V single-supply voltage

APPLICATIONS

RF PA linearization/RF predistortion

Amplitude and phase modulation

Variable attenuators and phase shifters

CDMA2000, WCDMA, GSM/EDGE linear power amplifiers

Smart antennas

FUNCTIONAL BLOCK DIAGRAM

90

°

0

°

VPS2

QBBM

QBBP

RFIP

RFIM

DSOP

IBBM

IBBP

RFOP

RFOM

VPRF

CMOP

Figure 1.

GENERAL DESCRIPTION

The AD8341 vector modulator performs arbitrary amplitude

and phase modulation of an RF signal. Since the RF signal path

is linear, the original modulation is preserved. This part can be

used as a general-purpose RF modulator, a variable attenu-

ator/phase shifter, or a remodulator. The amplitude can be

controlled from a maximum of −4.5 dB to less than −34.5 dB,

and the phase can be shifted continuously over the entire 360°

range. For maximum gain, the AD8341 delivers an OP1dB of

8.5 dBm, an OIP3 of 17.5 dBm, and an output noise floor of

−150.5 dBm/Hz, independent of phase. It operates over a

frequency range of 1.5 GHz to 2.4 GHz.

The baseband inputs in Cartesian I and Q format control the

amplitude and phase modulation imposed on the RF input

signal. Both I and Q inputs are dc-coupled with a ±500 mV

differential full-scale range. The maximum modulation band-

width is 230 MHz, which can be reduced by adding external

capacitors to limit the noise bandwidth on the control lines.

Both the RF inputs and outputs can be used differentially or

single-ended and must be ac-coupled. The RF input and output

impedances are nominally 50 Ω over the operating frequency

range. The DSOP pin allows the output stage to be disabled

quickly in order to protect subsequent stages from overdrive.

The AD8341 operates off supply voltages from 4.75 V to 5.25 V

while consuming approximately 125 mA.

The AD8341 is fabricated on Analog Devices’ proprietary, high

performance 25 GHz SOI complementary bipolar IC process. It

is available in a 24-lead, Pb-free LFCSP package and operates

over a −40°C to +85°C temperature range. Evaluation boards

are available.