原标题：Linear LTC5569双路有源下变换混频解决方案

　　Linear公司的LTC5569是双路有源下变换混频器,每个混频器包括单独的LO缓冲放大器,有源混频器核,以及带使能引脚的偏压电路.1950MHz时的IIP3高达26.8dBm,变换增益2dB,1950MHz的噪音为11.7dB,通路间的隔离度为44dB,总功耗为 3.3V/600W,主要用在无线接收器,MIMO接收器和遥控无线电单元.本文介绍了LTC5569主要特性, 方框图, 多用途接收器电路图以及低通和高通IF输出匹配电路图,测试电路和评估板布局图.

　　The LTC®5569 dual active downconverting mixer is optimized for diversity and MIMO receiver applications that require low power and small size. Each mixer includes an independent LO buffer amplifier, active mixer core, and bias circuit with enable pin. The symmetry of the IC assures that a phase and amplitude coherent LO is applied to each mixer.

　　The RF inputs are 50Ω matched from 1.4GHz to 3.3GHz, and easily matched for higher or lower RF frequencies with simple external matching. The LO input is 50Ω matched from 1GHz to 3.5GHz, even when one or both mixers are disabled. The LO input is easily matched for higher or lower frequencies, as low as 350MHz, with simple external matching. The low capacitance differential IF outputs are usable up to 1.6GHz.

　　LTC5569主要特性：

　　High IIP3: 26.8dBm at 1950MHz

　　2dB Conversion Gain

　　Low Noise Figure: 11.7dB at 1950MHz

　　17dB NF Under 5dBm Blocking

　　44dB Channel Isolation

　　Low Power: 3.3V/600mW Total

　　Very Small Solution Size

　　Enable Pins for Each Mixer

　　Wide IF Frequency Range

　　LO Input 50Ω Matched in All Modes

　　–40℃ to 105℃ Operation

　　16-Lead (4mm × 4mm) QFN package

　　LTC5569应用：

　　Wireless Infrastructure Diversity Receivers

　　MIMO Infrastructure Receivers

　　Remote Radio Units

　　图1.LTC5569方框图

　　图2.LTC5569 190MHz通带IF匹配的多用途接收器电路图

　　图3.LTC5569 200欧姆低通IF输出匹配电路图(所示元件为190MHz IF)

　　图4.LTC5569 200欧姆高通IF输出匹配电路图(所示元件为190MHz IF)

　　图5.LTC5569 测试电路图