ADRF6806:  50 MHz TO 525 MHz Quadrature Demodulator with Fractional-N PLL and VCO

The ADRF6806 is a high dynamic range IQ demodulator with integrated PLL and VCO. The fractional-N PLL/synthesizer generates a frequency in the range of 2.8 GHz to 4.2 GHz. A programmable quadrature divider (divide ratio = 4 to 80) divides the output frequency of the VCO down to the required local oscillator (LO) frequency to drive the mixers in quadrature. Additionally, an output divider (divide ratio = 4 to 8) generates a divided-down VCO signal for external use.

The PLL reference input is supported from 10 MHz to 160 MHz. The phase detector output controls a charge pump whose output is integrated in an off-chip loop filter. The loop filter output is then applied to an integrated VCO.

The IQ demodulator mixes the differential RF input with the complex LO derived from the quadrature divider. The differential I and Q output paths have excellent quadrature accuracy and can handle baseband signaling or complex IF up to 120 MHz.

A reduced power mode of operation is also provided by programming the serial interface registers to reduce current consumption, with slightly degraded input linearity and output current drive.

The ADRF6806 is fabricated using an advanced silicon-germanium BiCMOS process. It is available in a 40-lead, exposed-paddle, RoHS-compliant, 6 mm × 6 mm LFCSP package. Performance is specified over the −40°C to +85°C temperature range.

Applications

• QAM/QPSK RF/IF demodulators
• Cellular W-CDMA/CDMA/CDMA2000
• Microwave point-to-(multi)point radios
• Broadband wireless and WiMAX