LT5571 Datasheet, PDF (1/16 Pages) Linear Technology – 620MHz - 1100MHz High Linearity Direct Quadrature Modulator

FEATURES
■ _{Direct Conversion from Baseband to RF}
■ _{High Output: –4.2dB Conversion Gain}
■ _{High OIP3: 21.7dBm at 900MHz}
■ _{Low Output Noise Floor at 20MHz Offset:}
No RF: –159dBm/Hz
P_OUT = 4dBm: –153.3dBm/Hz
■ _{Low Carrier Leakage: –42dBm at 900MHz}
■ _{High Image Rejection: –53dBc at 900MHz}
■ _{3-Ch CDMA2000 ACPR: –70.4dBc at 900MHz}
■ _{Integrated LO Buffer and LO Quadrature Phase}
Generator
■ _{50Ω AC-Coupled Single-Ended LO and RF Ports}
■ _{High Impedance DC Interface to Baseband Inputs}
with 0.5V Common Mode Voltage
■ _{16-Lead QFN 4mm × 4mm Package}
APPLICATIONS
■ _{RFID Interrogators}
■ _{GSM, CDMA, CDMA2000 Transmitters}
■ _{Point-to-Point Wireless Infrastructure Tx}
■ _{Image Reject Up-Converters for Cellular Bands}
■ _{Low-Noise Variable Phase-Shifter for 620MHz to}
1100MHz Local Oscillator Signals
LT5571
620MHz – 1100MHz High
Linearity Direct Quadrature
Modulator
DESCRIPTION
The LT^®5571 is a direct I/Q modulator designed for high
performance wireless applications, including wireless
infrastructure. It allows direct modulation of an RF signal
using differential baseband I and Q signals. It supports
RFID, GSM, EDGE, CDMA, CDMA2000, and other systems.
It may also be configured as an image reject upconvert-
ing mixer by applying 90° phase-shifted signals to the I
and Q inputs. The high impedance I/Q baseband inputs
consist of voltage-to-current converters that in turn drive
double-balanced mixers. The outputs of these mixers are
summed and applied to an on-chip RF transformer, which
converts the differential mixer signals to a 50Ω single-
ended output. The four balanced I and Q baseband input
ports are intended for DC-coupling from a source with a
common-mode voltage at about 0.5V. The LO path consists
of an LO buffer with single-ended input, and precision
quadrature generators that produce the LO drive for the
mixers. The supply voltage range is 4.5V to 5.25V.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Direct Conversion Transmitter Application
I-DAC
EN
Q-DAC
V-I
I-CH
Q-CH
V-I
V_CC
LT5571
0°
90°
BALUN
5V
100nF
×2 RF = 620MHz
TO 1100MHz
PA
BASEBAND
GENERATOR
VCO/SYNTHESIZER
5571 TA01a
CDMA2000 ACPR, AltCPR and Noise vs RF
Output Power at 900MHz for 1 and 3 Carriers
–40
DOWNLINK TEST
MODEL 64 DPCH
–110
–50
3-CH ACPR
–120
–60
3-CH AltCPR
1-CH
ACPR –130
–70
–140
–80
1-CH AltCPR
1-CH NOISE
–150
3-CH NOISE
–90
–30 –25 –20 –15 –10 –5
–160
0
RF OUTPUT POWER PER CARRIER (dBm)
5571 TA01b
5571f
1