RF ICs seem to be getting smaller and more fully integrated all the time. For example, the Analog Devices ADRF6806 and ADRF6807 quadrature demodulators are designed for a wide range of broadband communication applications such as cellular infrastructure and microwave point-to-point radios.

The ADRF6806 operates in the 50-MHz to 525-MHz range, and the ADRF6807 operates in the 700-MHz to 1050-MHz range. Both integrate an IQ demodulator with a high-performance phase-locked loop (PLL), a low-noise voltage-controlled oscillator (VCO), and two low-dropout regulators (LDOs).

The devices appear to be the industry’s only quadrature demodulators to combine three RF functions into a single device, simplifying design and reducing board space and bill of materials cost. They use a high-performance mixer core that results in an exceptional input third-order intercept point (IP3) and input 1-dB compression point (P1dB), with a very low output noise floor for excellent dynamic range.

The serial peripheral interface (SPI) port enables users to control the fractional-N PLL functions, the demodulator local oscillator (LO) divider functions, multiple optimization functions, and low-power mode, as well as allow for an externally applied LO.

The ADRF6806 features:

• RF performance: input P1dB of 12.2 dBm; input IP3 of 28.5 dBm; noise figure (DSB) of 12.2; voltage conversion gain of 1 dB
• Quadrature demodulation accuracy: phase accuracy of < 0.5° and amplitude accuracy of < 0.1 dB
• Error vector magnitude (EVM) < –45 dB over RF input range of +35 dB
• Baseband demodulation of 135 MHz, 3-dB bandwidth
• SPI for PLL programming

The ADRF6807 features:

• RF performance: input P1dB of 12.8 dBm; input IP3 of 26.7 dBm; noise figure (DSB) of 13.1; voltage conversion gain of 1 dB
• Quadrature demodulation accuracy: phase accuracy of < 0.5° and amplitude accuracy of < 0.1 dB
• Baseband demodulation of 170 MHz, 3-dB bandwidth
• EVM < –28 dB over RF input range of +33 dB
• SPI for PLL programming

Both demodulators are designed with an advanced silicon-germanium biCMOS process and are available in a compact 6- by 6-mm lead-frame chip-scale package (LFCSP). They cost $9.98 in 1000-unit quantities. Evaluation boards are also available for $150. Samples and full production quantities are available now.

Analog Devices also offers a PLL frequency synthesizer that can be used to implement LOs as high as 18 GHz in the up-conversion and down-conversion sections of wireless receivers and transmitters. The exceptionally high-bandwidth ADF41020 permits designers to potentially eliminate a frequency-doubler stage, simplifying system architecture and reducing cost.

Target applications include microwave point-to-point and multi-point radios, wireless infrastructure equipment, very small aperture terminal (VSAT) radios, semiconductor test equipment, radar applications, and private mobile radios. With an operating bandwidth up to 18 GHz, this represents the highest-frequency PLL available on the market today.

The ADF41020 PLL frequency synthesizer consists of a low-noise, digital phase-frequency detector, a precision charge pump, a programmable reference divider, and high-frequency programmable feedback dividers. A complete synthesizer can be implemented if the PLL is used with an external loop filter and VCO.

The PLL can be used to drive external microwave VCOs via an active loop filter. The pinout matches very closely the pinout of the ADF4106/7/8 family of integer-N PLLs, meaning only a minor layout change is required when updating a design to take advantage of the much wider bandwidth.

The ADF41020 also features:

• 18-GHz maximum RF input frequency
• Integrated prescaler
• Programmable dual-modulus prescaler
• 2.7-V to 3.3-V PLL power supply
• Programmable charge-pump currents
• Three-wire serial interface
• Analog and digital lock detect
• Hardware and software power-down mode

The ADF41020 PLL frequency synthesizer is packaged in a 20-lead LFCSP housing and costs $12.77 in 1000-unit quantities. Samples are available now.

Analog Devices                      
www.analog.com