Linear Technology releases downconverting mixers for 3G, WiMAX basestations

(Product News, 8 Feb 2007)

Linear Technology's LT5557 downconverting active RF mixer enhances receiver dynamic range performance while extending bandwidth capability to cover 3G and WiMAX basestation frequencies to 3.8GHz. The 3.3V, high-linearity device offers 24.7dBm IIP3, noise figure of 11.7dB, and 2.9dB of gain at 1.95GHz. At WiMAX frequencies, its ratings are: 23.5dBm IIP3, and 1.7dB gain at 3.6GHz.

Power consumption—about 270mW from a 3.3V supply—is claimed to be low for this class of high linearity mixers. Incorporating on-chip RF transformers, the device features single-ended, 50Ω matching at the RF and LO inputs. The combination yields an overall cost- effective, compact, easy-to-use and high performance receiver solution for wireless basestations of all types.

The LT5557 incorporates a double-balanced active mixer core topology with on-chip LO buffer. Differential drive is employed internally throughout the mixer to maximize linearity and RF isolation. Conversion from single ended to differential is accomplished through on-chip RF balun transformers at the RF and LO inputs. The device's wide operating bandwidth covers the 850MHz to 965MHz GSM and US cellular bands, as well as 1.7GHz to 2.1GHz 3G wireless services. The LT5557 also supports WiMAX operating in the US at 2.6GHz and worldwide at up to 3.8GHz.

The LT5557 also features a shutdown feature. When it is disabled, it draws a maximum sleep current of 0.1mA. Avaialble in a 16-lead 4x4mm QFN surface mount package, the chip is pin compatible with other high performance Linear Technology downconverting mixers. Pricing starts at $5.95 each in 1,000-piece quantities.

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