原标题：Linear LTC5594300MHz-9GHz I-Q解调器解决方案

　　Linear公司的LTC5594是用于300MHz-9GHz频段的直接转换正交解调器,镜像抑制优于60dB,5.8GHz时总OIP3为37dBm,OIP2为58dBm,可调整到65dBm,最达功率转换增益为9.2dB,工作温度–40℃到105℃,主要用在5G基站前传(Fronthaul)和回传(Backhaul)接收器,军用和卫星接收器,点对点宽带无线点,高线性直接转换I/Q SDR,测试仪表和DPD接收器.本文介绍了LTC5594主要特性,框图和测试电路图,以及演示板DC2645A主要特性,硬件建立图和电路图.

　　DC2645A - LTC5594 l 300MHz to 9GHz I/Q Demodulator with Wideband IF Amplifier The LTC®5594 is a direct conversion quadrature demodulatoroptimized for high linearity zero-IF and low-IF receiverapplications in the 300MHz to 9GHz frequency range.

　　The very wide IF bandwidth of more than 1GHz makesthe LTC5594 particularly suited for demodulation of verywideband signals, especially in 5G fronthaul/backhaulreceiver applications. The outstanding dynamic range ofthe LTC5594 makes the device suitable for demandinginfrastructure direct conversion applications. Proprietarytechnology inside the LTC5594 provides the capabilityto optimize OIP2 to 65dBm, and achieve image rejectionbetter than 60dB. The DC offset control function allowsnulling of the DC offset at the A/D converter input, therebyoptimizing the dynamic range of true zero-IF receivers thatuse DC-coupled IF signal paths. The wideband RF and LOinput ports make it possible to cover all the major wirelessinfrastructure frequency bands using a single device. TheIF outputs of the LTC5594 are designed to interface directlywith most common A/D converter input interfaces. Thehigh OIP3 and high conversion gain of the device eliminatethe need for additional amplifiers in the IF signal path.

　　LTC5594主要特性:

　　True Zero IF Demodulation

　　Wideband Input Matched from 500MHz to 9GHz

　　Wide IF Bandwidth: DC to 1GHz (1dB Flatness)

　　37dB Image Rejection, Adjustable to 60dB

　　High Total OIP3: 37dBm at 5.8GHz

　　58dBm OIP2 at 5.8GHz, Adjustable to 65dBm

　　Max Power Conversion Gain: 9.2dB at 5.8GHz

　　Single-Ended RF Input with On-Chip Transformer

　　User Adjustable DC Offset Null

　　Serial Interface

　　IF Amplifier Gain Adjustable in Eight Steps

　　IF Amplifier Shutdown/Enable

　　Low Power Shutdown Mode

　　Operating Temperature Range (TC): –40℃ to 105℃

　　32-Lead 5mm × 5mm QFN Package

　　LTC5594应用:

　　5G Base Station Fronthaul/Backhaul Receivers

　　Military and Satellite Receivers

　　Point-to-Point Broadband Radios

　　High Linearity Direct Conversion I/Q SDR

　　Test Instrumentation

　　DPD Receivers

　　图1.LTC5594框图

　　图2.LTC5594测试电路图

　　图3.LTC5594 IF放大器输入,混合输出测试电路图

　　图4.LTC5594反混淆滤波器IF放大器输出电路图

　　演示板DC2645A

　　Demonstration circuit 2645A showcases the LTC®5594300MHz to 9GHz high linearity I/Q demodulator with widebandIF amplifiers. The USB serial controller, DC590B, isrequired to control and configure LTC5594 for its evaluation.

　　The DC2645A’s single-ended RF input is optimized for500MHz to 9GHz and can be easily modified for lowerfrequency evaluations down to 300MHz. Its single-endedLO input is programmable for 300MHz to 9GHz operationvia SPI bus. The demo circuit includes discrete L-C interstagelowpass filters between the demodulator outputsand the IF amplifier inputs, which limits the DC-coupleddifferential I and Q outputs to about 1GHz. (The LTC5594data sheet lists filter component values for other cutofffrequencies.)By writing to specific registers through SPI bus,LTC5594’s IF amplifier gain, LO input frequency, outputDC offset, image rejection, and linearity can be adjustedor optimized.

　　详情请见:

DC2645A-1-SCH.pdf

DC2645AF.pdf

5594f.pdf