LT5575
800MHz to 2.7GHz
High Linearity Direct Conversion
Quadrature Demodulator
DESCRIPTION
FEATURES
The LT®5575 is an 800MHz to 2.7GHz direct conversion
quadrature demodulator optimized for high linearity
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Input Frequency Range: 0.8GHz to 2.7GHz*
50Ω Single-Ended RF and LO Ports
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High IIP3: 28dBm at 900MHz, 22.6dBm at 1.9GHz
High IIP2: 54.1dBm at 900MHz, 60dBm at 1.9GHz
Input P1dB: 13.2dBm at 900MHz
I/Q Gain Mismatch: 0.04dB Typical
I/Q Phase Mismatch: 0.4° Typical
Low Output DC Offsets
Noise Figure: 12.8dB at 900MHz, 12.7dB at 1.9GHz
Conversion Gain: 3dB at 900MHz, 4.2dB at 1.9GHz
Very Few External Components
receiver applications. It is suitable for communications
receivers where an RF signal is directly converted into I
and Q baseband signals with bandwidth up to 490MHz.
The LT5575 incorporates balanced I and Q mixers, LO
bufferamplifiersandaprecision,highfrequencyquadrature
phaseshifter.Theintegratedon-chipbroadbandtransform-
ers provide 50Ω single-ended interfaces at the RF and LO
inputs. Only a few external capacitors are needed for its
application in an RF receiver system.
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Shutdown Mode
16-Lead QFN 4mm × 4mm Package with
Exposed Pad
The high linearity of the LT5575 provides excellent spur-
free dynamic range for the receiver. This direct conversion
demodulator can eliminate the need for intermediate fre-
quency(IF)signalprocessing,aswellasthecorresponding
requirements for image filtering and IF filtering. Channel
filtering can be performed directly at the outputs of the I
and Q channels. These outputs can interface directly to
channel-select filters (LPFs) or to baseband amplifiers.
APPLICATIONS
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Cellular/PCS/UMTS Infrastructure
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RFID Reader
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High Linearity Direct Conversion I/Q Receiver
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Operation over a wider frequency range is possible with reduced performance. Consult
the factory.
TYPICAL APPLICATION
Conversion Gain, NF, IIP3 and IIP2
vs LO Input Power at 1900MHz
High Signal-Level I/Q Demodulator for Wireless Infrastructure
+5V
35
30
25
20
15
10
5
70
60
50
40
30
20
10
0
IIP2
V
CC
LT5575
+
RF
INPUT
BPF
BPF
LPF
I
OUT
RF
LNA
VGA
A/D
–
I
IIP3
OUT
0°
DSB NF
LO
LO INPUT
ENABLE
–40°C
25°C
85°C
0°/90°
CONV
GAIN
90°
+
LPF
Q
Q
OUT
VGA
A/D
–
OUT
EN
0
–5
–15
–10
0
5
5575 TA01
LO INPUT POWER (dBm)
5575 TA01b
5575f
1