GENERAL DESCRIPTION

The AD8347 is a broadband direct quadrature demodulator with RF and baseband automatic gain control (AGC) amplifiers. It is suitable for use in many communications receivers, performing

quadrature demodulation directly to baseband frequencies. The input frequency range is 800 MHz to 2.7 GHz. The outputs can be connected directly to popular A-to-D converters such as the

AD9201and AD9283. The RF input signal goes through two stages of variable gain amplifiers prior to two Gilbert-cell mixers. The LO quadrature phase splitter employs polyphase filters to achieve high quadrature accuracy and amplitude balance over the entire operating frequency range. Separate I and Q channel variable gain amplifiers follow the baseband outputs of the mixers. The

RF and baseband amplifiers together provide 69.5 dB of gain control. A precision control circuit sets the linear-in-dB RF gain response to the gain control voltage.

FEATURES

Integrated RF and baseband AGC amplifiers

Quadrature phase accuracy 1° typ

I/Q amplitude balance 0.3 dB typ

Third-order intercept (IIP3) +11.5 dBm @ min gain

Noise figure 11 dB @ max gain

AGC range 69.5 dB

Baseband level control circuit

Low LO drive −8 dBm

ADC-compatible I/Q outputs

Single supply 2.7 V to 5.5 V

Power-down mode

28-lead TSSOP package

APPLICATIONS

Cellular base stations

Radio links

Wireless local loop

IF broadband demodulators

RF instrumentation

Satellite modems