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FEATURES
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LT5575 800MHz to 2.7GHz High Linearity Direct Conversion Quadrature Demodulator DESCRIPTION
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 transformers 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 spurfree dynamic range for the receiver. This direct conversion demodulator can eliminate the need for intermediate frequency (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.
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
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Cellular/PCS/UMTS Infrastructure RFID Reader High Linearity Direct Conversion I/Q Receiver
TYPICAL APPLICATION
High Signal-Level I/Q Demodulator for Wireless Infrastructure
+5V BPF LNA BPF RF INPUT VCC RF LT5575 VGA 0° IOUT– A/D
Conversion Gain, NF, IIP3 and IIP2 vs LO Input Power at 1900MHz
35 IIP2 GAIN (dB), NF (dB), IIP3 (dBm) 70 60 IIP3 50 IIP2 (dBm) 40 DSB NF –40°C 25°C 85°C 30 20 10 0
IOUT+
LPF
30 25 20 15 10 5 0 –15
LO INPUT
LO 0°/90° 90°
QOUT+ QOUT–
LPF VGA A/D
CONV GAIN
ENABLE
EN
5575 TA01
–5 –10 0 LO INPUT POWER (dBm)
5
5575 TA01b
5575f
1
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LT5575
(Note 1)
ABSOLUTE MAXIMUM RATINGS
Power Supply Voltage ..............................................5.5V Enable Voltage ................................ –0.3V to VCC + 0.3V LO Input Power ....................................................10dBm RF Input Power ....................................................20dBm RF Input DC Voltage ...............................................±0.1V LO Input DC Voltage ..............................................±0.