LT5558_15 Datasheet, PDF (1/16 Pages) Linear Technology – 600MHz to 1100MHz High Linearity Direct Quadrature Modulator

FEATURES
■ _{Direct Conversion from Baseband to RF}
■ _{High OIP3: + 22.4dBm at 900MHz}
■ _{Low Output Noise Floor at 20MHz Offset:}
No RF: –158dBm/Hz
P_OUT = 4dBm: –152.7dBm/Hz
■ _{Low Carrier Leakage: –43.7dBm at 900MHz}
■ _{High Image Rejection: –49dBc at 900MHz}
■ _{3 Channel 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 Interface to Baseband Inputs}
with 2.1V Common Mode Voltage
■ _{16-Lead QFN 4mm × 4mm Package}
APPLICATIONS
■ _{RFID Single-Sideband Transmitters}
■ _{Infrastructure TX for Cellular and ISM Bands}
■ _{Image Reject Up-Converters for Cellular Bands}
■ _{Low-Noise Variable Phase-Shifter for 600MHz to}
1100MHz Local Oscillator Signals
■ _{Microwave Links}
LT5558
600MHz to 1100MHz
High Linearity Direct
Quadrature Modulator
DESCRIPTION
The LT^®5558 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
GSM, EDGE, CDMA, CDMA2000, and other systems. It
may also be configured as an image reject upconverting
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 balanced I and Q baseband input ports are intended
for DC coupling from a source with a common-mode
voltage level of about 2.1V. The LO path consists of an LO
buffer with single-ended input, and precision quadrature
generators which 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
600MHz to 1100MHz Direct Conversion Transmitter Application
∫ ^IDAC
EN
∫ ^QDAC
V_CC
8, 13
5V
2 x 100nF
14
16
V-1
I-CH
1
O°
LT5558
RF = 600MHz TO
1100MHz
11 ^PA
90°
7
Q-CH
5
V-1
BALUN
BASEBAND
GENERATOR
2, 4, 6, 9, 10,
12, 15, 17
3
VCO/SYNTHESIZER
5558 TA01
CDMA2000 ACPR, AltCPR and Noise vs
RF Output Power at 900MHz for 1 and 3 Carriers
–40
DOWNLINK TEST
MODEL 64 DPCH
–50
3-CH ACPR
3-CH ALTCPR
–60
–70
–110
–120
–130
1-CH ACPR
–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)
5558 TA01b
5558fa
1