高灵敏度W波段平衡辐射计硅基集成芯片研究

W-band radiometer based imagers demonstrates wide applications. Silicon-based radiometer can dramatically reduce imager’s size, weight, un-uniformity between receiving channels and cost. However, silicon-based W-band radiometer chip suffers from a low sensitivity, which becomes the bottle neck of this type of radiometer’s development. As a matter of fact, the radiometer’s sensitivity is decided by the root-mean-square value of the uniform noise figure of receiver, gain variation and the introduced external noise. According to this fundamental principle, based on the developed silicon-based Dicke radiometer, the team plan to conduct the following investigations to improve the sensitivity: Firstly, a method of seamlessly integrating the distributed switch and the active noise load is proposed, which leads to a broadened bandwidth of the silicon-based noise source and reduced gain fluctuation. Meanwhile, a differential receiver architecture together with a novel noise-suppression sub-block are deployed to cancel the supply noise. The receiving architecture is built upon a single-ended receiver, a dummy front-end block and a differential square-law detector. With this architecture, the external noise will be reduced. Moreover, substrate-isolating technique are proposed to prevent the disturbing from the control signal, which reduces the external noise further. Finally, fully-integrated W-band radiometer with balanced calibration is achieved and verified in the imaging system. The above research is expected to make the silicon-based W-band radiometer satisfy the threshold NETD requirement of industry applications. And a design method of achieving high-sensitivity silicon-based radiometer will also be concluded based on the above experiments.

基于W波段辐射计的成像系统应用广泛，辐射计硅基集成芯片可大幅改进成像系统的体积、重量、通道间一致性、成本等指标, 但灵敏度低是制约硅基W波段辐射计发展的瓶颈。辐射计的灵敏度由前端的归一化噪声温度、接收机增益波动和外部噪声的统计平均值决定，本项目根据这一根本原因，在团队已实现的狄克辐射计前端集成芯片的基础上，拟通过以下途径来提高灵敏度：①无缝集成分布式开关和有源噪声负载，拓展硅基噪声源的带宽，在宽带范围实现平衡校准，减小增益波动；②采用基于虚设前端模块和差分检波器的电源噪声抵消架构，结合新型电源噪声抑制模块，使接收机具备电源噪声抑制功能，减小外部噪声；③提出硅衬底隔离技术，以隔绝控制信号干扰，进一步减小外部噪声；最终实现W波段平衡辐射计集成芯片，并验证成像效果。通过以上研究，使硅基W波段辐射计的实测NETD满足工业用辐射计使用标准，并总结出高灵敏度硅基辐射计的设计方法。

辐射计作为一种高灵敏度接收机，常用于测量目标物体自身的热辐射，在遥感探测、人体安检成像、军事导弹、低能见度环境导航及气象观测等诸多领域中发挥着重要作用。而基于噪声源校准的平衡辐射计可通过单刀双掷开关在天线和噪声源间周期切换，有效解决传统辐射计在应用中存在的噪声干扰、增益起伏问题，明显提升灵敏度。其中用于校准的冷、热噪声源的带宽直接影响平衡辐射计的灵敏度，且现有的噪声源模块存在体积大、使用复杂等问题，因此研制高灵敏度和集成化的平衡辐射计具有重要研究意义。.本项目研究实现了用于高灵敏度平衡辐射计系统的超宽带冷热集成噪声源、宽带低噪声放大器、检波器、零反射低噪声放大器、混频器、滤波器等电路，在此基础上实现了一款高集成度的双通带平衡辐射计模块，并完成了应用验证。具体的研究工作如下：(1) 首次实现了一种分布式开关切换冷热噪声源，通过无缝集成分布式低噪声放大单元和宽带功率合成单元，可在156%带宽内实现狄克式辐射计的平衡校准，并具有对225 K至650 K的输入信号范围实现自动进行平衡校正的能力。(2) 研究设计了用于平衡辐射计接收通道的一系列子电路，包括单刀双掷开关电路、分布式低噪声放大器、检波器、级间反射吸收的零反射低噪声放大器、混频器、滤波器等电路。(3) 进一步研究实现了集成上述子电路的一种双通带平衡辐射计验证系统，分别在两个通带内实现了低至 0.36 K和1.39 K的等效噪声温度。.本项目研究实现的用于平衡辐射计的冷热集成噪声源，具有156%的工作带宽，达到了同类设计中最高带宽。设计并验证实现的双通带平衡辐射计模块集成了超宽带冷热集成噪声源及单刀双掷开关、低噪声放大器、检波器及滤波器等子电路，在1.2 GHz和4.5 GHz的峰值响应可分别达到58 MV/W和310 MV/W，具有体积小、灵敏度高的特点。上述研究成果可直接应用于遥感探测、高分辨率成像等应用场景中，具有明确的预期贡献。