LT5503

1

MODOUT

0

°

90

°

÷2

÷1

CONTROL

LOGIC

GC1

GC2

GND

LO2

2.45GHz

BPF

2V

2V

2.45GHz

MODULATED

RFOUT

MODIN

LO1

LO1IN (2075MHz)

LO2IN

(750MHz)

DMODE

MIXEN

MODEN

MIXER

ENABLE

MODULATOR

ENABLE

5503 F01

VGA

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Final Electrical Specifications

s

IEEE 802.11 DSSS and FHSS

s

High Speed Wireless LAN (WLAN)

s

Wireless Local Loop (WLL)

s

PCS Wireless Data

s

MMDS

s

Single 1.8V to 5.25V Supply

s

Direct IQ Modulator with Integrated 90

° Phase

Shifter*

s

Four Step RF Power Control

s

120MHz Modulation Bandwidth

s

Independent Double-Balanced Mixer

s

Modulation Accuracy Insensitive to Carrier Input

Power

s

Modulator I/Q Inputs Internally Biased

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

1.2GHz to 2.7GHz Direct

IQ Modulator and Mixer

October 2001

The LT

voltage operation, and is compatible with the LTC family of

WLAN products. 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 delivers –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.

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

DESCRIPTIO

Figure 1. 2.45GHz Transmitter Application, Carrier for Modulator Generated by Upmixer

SUPPLY VOLTAGE (V)

1.8

–2

–3

–4

–5

–6

2.4

3.0

3.6

4.2

5503 TA01b

4.8

5.4

2.45GHz Modulated Output

Power vs Supply Voltage

*Patent Pending