The HFA3761 is a highly integrated baseband converter for quadrature demodulation applications. The HFA3761 400MHz AGC and quadrature IF demodulator is one of the seven chips in the PRISM® full duplex chip set (see Typical Application Diagram). It features all the necessary blocks for baseband demodulation of I and Q signals. It has a two stage integrated AGC IF amplifier with 82dB of voltage gain and 76dB of gain control range. Baseband antialiasing and shaping filters are integrated in the design. Four filter bandwidths are programmable via a two bit digital control interface. In addition, these filters are continuously tunable over a ±20% frequency range via one external resistor. To achieve broadband operation, the Local Oscillator frequency input is required to be twice the desired frequency of demodulation. A selectable buffered divide by 2 LO output and a stable reference voltage are provided for convenience of the user. The device is housed in a thin 80 lead TQFP package well suited for PCMCIA board applications.

Features
• Integrates all IF and AGC Receive Functions
• Broad Frequency Range . . . . . . . . . . 10MHz to 400MHz
• I/Q Amplitude and Phase Balance . . . . 0.2dB, 2 Degrees
• 5th Order Programmable
   Low Pass Filter . . . . . . . . . . . . . . . . . 2.2MHz to 17.6MHz
• 400MHz AGC Gain Strip . . . . . . . . . . . . . . . . . . . . . 82dB
• AGC Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75dB
• Low LO Drive Level . . . . . . . . . . . . . . . . . . . . . . . -15dBm
• Fast AGC Switching . . . . . . . . . . . . . . . . . . . . . . . . . . 1µs
• Power Management/Standby Mode
• Single Supply 2.7V to 5.5V Operation

Applications
• Wireless Local Loop
• Wireless Local Area Networks
• PCMCIA Wireless Transceivers
• ISM Systems
• CDMA Radios
• PCS/Wireless PBX