LT5503

U U FEATURES ■ Single 1.8V to 5.25V Supply ■ Direct IQ Modulator with Integrated 90° Phase Shifter* ■ Four Step RF Power Control ■ 120MHz Modulation Bandwidth ■ Independent Double-Balanced Mixer ■ Modulation Accuracy Insensitive to Carrier Input Power ■ Modulator I/Q Inputs Internally Biased ■ Available in 20-Lead FE Package U APPLICATIO S ■ IEEE 802.11 DSSS and FHSS ■ High Speed Wireless LAN (WLAN) ■ Wireless Local Loop (WLL) ■ PCS Wireless Data ■ MMDS , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. *Patent Pending LT5503 1.2GHz to 2.7GHz Direct IQ Modulator and Mixer DESCRIPTIO The LT®5503 is a front-end transmitter IC designed for low voltage operation. The IC contains a high frequency quadrature 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. TYPICAL APPLICATIO 2.45GHz Tra...