LT5517
40MHz to 900MHz
Quadrature Demodulator
U
FEATURES
DESCRIPTIO
The LT®5517 is a 40MHz to 900MHz quadrature demodu-
lator optimized for high linearity receiver applications
where high dynamic range is important. It is suitable for
communications receivers where an RF or IF signal is
directly converted into I and Q baseband signals with a
bandwidth up to 130MHz. The LT5517 incorporates bal-
ancedIandQmixers, LObufferamplifiersandaprecision,
broadband quadrature generator derived from an on-chip
divide-by-two circuit.
■
RF Input Frequency Range: 40MHz to 900MHz
■
High IIP3: 21dBm at 800MHz
■
High IIP2: 58dBm at 800MHz
■
I/Q Gain Mismatch: 0.3dB Max
■
I/Q Phase Mismatch: 0.7°
■
Noise Figure: 12.4dB at 800MHz
■
Conversion Gain: 3.3dB at 800MHz
■
Baseband Bandwidth: 130MHz
■
Single Ended, 50Ω Matched 2XLO Input
■
Shutdown Mode
The superior linearity and low noise performance of the
LT5517 is achieved across its full frequency range. A well-
balanceddivide-by-twocircuitgeneratesprecisionquadra-
ture LO carriers to drive the I mixer and the Q mixer.
Consequently, the outputs of the I-channel and the
Q-channelarewellmatchedinamplitude,andtheirphases
are 90° apart. The LT5517 also provides excellent 50Ω
impedance matching at the 2XLO port across its entire
frequency range.
■
16-Lead QFN (4mm × 4mm) Package
with Exposed Pad
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APPLICATIO S
■
Wireless Infrastructure
■
High Linearity Direct Conversion I/Q Receiver
■
High Linearity I/Q Demodulator
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
I/Q Output Power, IM3, IM2
vs RF Input Power
5V
BPF
BPF
20
V
CC
LT5517
+
RF
RF
LNA
+
LPF
I
I
OUT
OUT
0
VGA
VGA
P
OUT
–
–20
–40
0°
T
= 25°C
2XLO
= 1602MHz
= 799.9MHz
= 800.1MHz
A
–
P
f
= –10dBm
2XLO
RF1
RF2
DSP
IM3
f
f
–60
–80
+
–
LPF
Q
Q
OUT
IM2
2xLO
EN
2xLO
INPUT
÷2
OUT
90°
ENABLE
5517 F01
–100
–18
–14
–10
–6
–2
2
RF INPUT POWER (dBm)
Figure 1. High Signal-Level I/Q Demodulator for 450MHz Infrastructure Receiver
5517 F01b
5517f
1