【作者】 张巍；

【导师】 王宗新；

【作者基本信息】 东南大学 ， 电磁场与微波技术， 2015， 硕士

【摘要】 随着科技的高速发展,毫米波辐射计广泛应用于遥感、探测、安检等重要领域,具有广阔的市场和巨大的商业价值。检波电路作为辐射计的核心部分,尤其是直接检波式电路,因其结构简单,系统噪声温度低,是近些年来辐射计接收前端研究的热点课题。因此,本文将对W波段检波电路进行研究。在W波段,测试仪器接口均为波导口,本文首先研制了波导微带鳍线过渡结构,利用Spline曲线取点优化,缩短了鳍线过渡段的尺寸；通过在介质基片末端加凸型槽,改善了接口处阻抗的不连续性,最终进行了背腔结构的实物加工验证。实验结果表明,S参数实测曲线和仿真曲线一致性高,背腔过渡结构在84～110GHz内,反射系数小于-12dB,插损小于2dB,在整个80～110GHz频带内,反射系数小于-9dB。单侧过渡插损小于0.9dB。随后,利用该过渡转换结构,我们分别对W波段检波器和低噪声放大器进行了研制。W波段检波器采用了国内目前较少研究的VDI公司零偏置肖特基二极管,并编程提取了该二极管的Spice模型参数,最终利用该参数设计了检波器,实验结果表明在工作频带84～94GHz内,电压灵敏度大于800mV/mW,在92GHz处电压灵敏度高达1900mV/mW,接近国外先进水平。W波段低噪声放大器,我们采用了Gotmic公司LNA单片,通过两级MMIC芯片级联,实现预期36dB左右增益。为了防止芯片级间反馈,在两级芯片间加入了隔墙,并对隔墙进行了仿真；设计了时序电源模块,完成单电源供电；设计了低噪放的腔体结构,分别将低噪放高频部分和低频部分放在腔体的正反面,实现了物理隔离。最终完成装配和测试,实验测得在工作频带84GHz-94GHz内,低噪放增益为18±2dB,在中心频点89GHz处,1dB压缩输出功率为0dBm。增益没有达到预期指标,通过反复实验,推测原因主要在于芯片自身增益不足。最终,利用两级低噪放级联实现36dB左右的增益,计算得到系统的温度灵敏度为0.6K,达到预期目标。更多还原

【Abstract】 With the rapid development of technology, millimeter wave radiometer, which has vast market and great commercial value, is widely used in many important areas, such as remote sensing, detection, and security. Detector circuit as the core part radiometer, especially the direct detection structure circuit, has become the hot rearch topic because of its simple structure, low system noise temperature in recent years. Therefore, this thesis is forcus on the W-band detector circuit.In the W-band, feeds of test equipments are waveguide ports. This paper firstly developed a waveguide-microstrip transition by finline, using Spline curve to shorten the size of finline transition structure and adding convex grooves by the end of the dielectric substrate to improve the impedance discontinuity at the interface. Eventually the back to back structure of the transition had been carried out and tested. The experimental results showed that the insertion loss of the back to back structure was less than 2dB in the working band 84～110GHz, and the reflection coefficient S11 was less than-12dB.The reflection coeffient S11 was also less than-9dB in the whole 80～110GHz. The insertion loss of the single transition is less than 0.9dB.Subsequently, A W-band detector and a low-noise amplifier had been developed using the finline-structure waveguide-microstrip transition. The W-band detector used a new type zero bias Schottky diode, which had few studies in the domestic, made by VDI company. Firstly, we extraced the Spice model parameters of the diode, and then made the simulation of the detector by the Spice model. In the end, the detector was manufactured and tested. The results showed that the voltage sensitivity is greater than 800mV/mW in the operating frequency band 84-94GHz, especially at 92GHz the voltage sensitivity is up to 1900mV/mW, which is close to the international advanced level.In the end, we developed the W-band low-noise amplifier. Through cascading two MMICs, made by Gotmic company, to achieve the expected gain of 30dB or more. In order to prevent inter-chip-level feedback, we joined the wall between the two MMICs, and the wall was optimated by HFSS software. A sequency power module was also manufactured to complete the single power supply; For the purpose of achieving physical isolation between high frequency part and low frequency part of LNA, we designed cavity structure and put the two parts on the positive and negative of the cavity respectively. Finally assembly and testing of the LNA were completed, the experimental data showed the gain of LNA is 18±2dB, in the operating band of 84～94GHz and 1dB compression output power is OdBm at 89GHz. The results suggested that the LNA chips was not as good as it described. In order to achieve the desiered targets, we cascad two LNAs and calculated the minimum noise temperature of the whole system. The minimum noise temperature was 0.6K, which reached the expected targets.更多还原