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Analog Devices RF Mixers Provide High Performance from 700MHz to 2.8GHz
On May 10, 2011 ADI announced the availability of the semiconductor industry’s only double balanced wideband passive mixers. P/N ADL5811 is a single-channel mixer and P/N ADL 5812 is a dual-channel mixer. Due to differences in frequency allocations around the world, wireless receiver manufacturers often need to provide a receiver that will operate on several different frequencies, scattered across a wide frequency band. But, this presents a quandary. Active mixers have the requisite bandwidth but also have higher noise figures and lower linearity than passive mixers. Passive mixers have better noise figures and linearity but only across a narrow bandwidth. The new Analog Devices’ mixers employ a clever technical ploy to achieve the best of both worlds. The Analog Devices’ mixers use a programmable RF balun transformer and a programmable low pass filter to allow a receiver manufacturer to tune the mixer to a frequency of their choice. This allows a passive mixer to retain its low noise and greater linearity characteristics while achieving the bandwidth of an active mixer. This allows a receiver manufacturer to shorten design time, eliminate off-chip matching components, achieve a shorter time to market, reduce the number of component qualifications and greatly improve inventory management. The new ADI mixers offer outstanding performance. Detailed specifications are available on the ADI Web site, but two specs are important. The noise figure is below 12dB over a frequency range from 700MHz to 2800MHz at 25○C. The input 3rd order intercept (IIP3) is above 24dBm over the same frequency range, also at 40○C. In addition, the mixers’ programmability allows a designer to adjust the mixer bias to trade off between IIP3 and noise figure to meet the requirements of the application. These mixers are suitable for a wide variety of applications, including cellular base stations, down-link converters, cellular repeaters, software defined radios, broadband high dynamic range radios and many more. It’s always exciting to see a company use ingenuity to overcome a seemingly intractable design problem, and that’s exactly what Analog Devices has done here. Morry Marshall VP Strategic Technologies