LT5503

1

5503f

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

MODOUT

0

°

90

°

÷2

÷1

CONTROL

LOGIC

GC1

GC2

GND

LO2

2.45GHz

BPF

2V

2V

2.45GHz

MODULATED

RFOUT

MODIN

LT5503

LO1

LO1IN (2075MHz)

LO2IN

(750MHz)

DMODE

MIXEN

MODEN

MIXER

ENABLE

MODULATOR

ENABLE

5503 TA01

VGA

■

Direct IQ Modulator with Integrated 90

° Phase

Shifter*

■

120MHz Modulation Bandwidth

Power

1.2GHz to 2.7GHz Direct

IQ Modulator and Mixer

The LT

voltage operation. The IC contains a high frequency quadra-

ture modulator with a variable gain amplifier (VGA) and a

balanced mixer. The modulator includes a precision 90

°

phase shifter which allows direct modulation of an RF

signal by the baseband I and Q signals.

In a superheterodyne system, the mixer can be used to

generate the high-frequency RF input for the modulator by

mixing the system’s 1st and 2nd local oscillators.

The LT5503 modulator output P 1dB is –3dBm at 2.5GHz.

The VGA allows output power reduction in three steps up

to 13dB with digital control. The baseband inputs are

internally biased for maximum input voltage swing at low

supply voltage. If needed, they can be driven with external

bias voltages.

2.45GHz Transmitter Application, Carrier for Modulator Generated by Upmixer

SSB Output Power vs

I, Q Amplitude

0.01

1

0

–5

–10

–15

–20

–25

–30

–35

–40

–45

5503 G04

0.1

10

5.25 VDC

3 VDC

1.8 VDC

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners. *Patent Pending