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LT5575

800MHz to 2.7GHz High Linearity Direct Conversion Quadrature Demodulator

Linear Technology 

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

VCC

0°

LT5575

IOUT+

LPF

VGA

A/D

IOUT–

LO

LO INPUT

0°/90°

ENABLE EN

90°

QOUT+ LPF

VGA

A/D

QOUT–

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

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