LT5575_15 Datasheet, PDF (1/16 Pages) Linear Technology – 800MHz to 2.7GHz High Linearity Direct Conversion Quadrature Demodulator

LT5575
FEATURES
800MHz to 2.7GHz
High Linearity Direct Conversion
Quadrature Demodulator
DESCRIPTION
■ _{Input Frequency Range: 0.8GHz to 2.7GHz*}
■ _{50Ω Single-Ended RF and LO Ports}
■ _{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}
■ _{Shutdown Mode}
■ _{16-Lead QFN 4mm × 4mm Package with}
Exposed Pad
APPLICATIONS
■ _{Cellular/PCS/UMTS Infrastructure}
■ _{RFID Reader}
■ _{High Linearity Direct Conversion I/Q Receiver}
The LT^®5575 is an 800MHz to 2.7GHz direct conversion
quadrature demodulator optimized for high linearity
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
buffer amplifiers and a precision, high frequency quadrature
phase shifter. The integrated on-chip broadband transform-
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.
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) signal processing, as well as the corresponding
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.
, 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
High Signal-Level I/Q Demodulator for Wireless Infrastructure
+5V
BPF
BPF ^RF
LNA
INPUT _RF
V_CC
0°
LT5575
I_OUT+
LPF
VGA
A/D
I_OUT–
LO
LO INPUT
0°/90°
ENABLE EN
90°
Q_OUT+ ^LPF
VGA
A/D
Q_OUT–
5575 TA01
Conversion Gain, NF, IIP3 and IIP2
vs LO Input Power at 1900MHz
35
70
IIP2
30
60
25
IIP3
50
20
40
15
DSB NF
30
10
–40°C
25°C
CONV
20
85°C
GAIN
5
10
0
0
–15
–10
–5
0
5
LO INPUT POWER (dBm)
5575 TA01b
5575f
1