Application of GaAs Discrete p‐HEMTs in Low Cost Phase Shifters and QPSK Modulators

The application of a discrete pseudomorphic high electron mobility transistor (p‐HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p‐i‐n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p‐HEMT characterization and modeling in switching mode as well as the development of a low‐cost four‐bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.     

卫星数字电视的探讨

本文详细介绍了采用多路单载波和单路单载波方式，通过亚洲卫星２号一个Ｋｕ频段转发器传送多路数字电视信号的设计方案。     

Ku波段固态倍频源

采用晶振 倍频链的方式研制生产了１３ Ｇ Ｈｚ 的微波固态频率源。在－ ５５～＋ ８５℃温度范围内, 输出功率优于２５０ｍ Ｗ, 相位噪声为－ １０２ｄ Ｂ／１ｋ、－ １１０ｄ Ｂ／１０ｋ。     

提高Ku频段地球站抗雨衰能力的措施

通过一个工程实例介绍了提高Ku频段小站抗雨衰能力的方法。对如何充分发挥Ku频段转发器资源和大站高接收性能提出了建议。实践证明，这些方法和建议对实际工作是有益的。     

Application of microscopic techniques in authentication of herbal tea--Ku-Ding-Cha

Ku-Ding-Cha, a kind of herbal tea, has been widely used in China for a long time to support cardiovascular health. Confusion arises because in different parts of China different plants are used to produce the commercial teas. It is important to determine the identity of the used species in order to authenticate genuine Ku-Ding-Cha. However, once the plants have been processed, it is difficult to identify them through macroscopic identification; other means are necessary. A comparative study was made on 24 samples of Ku-Ding-Cha, including five standard identified and authenticated plants and 19 commercial samples, by microscopic techniques. The results showed that the shapes of leaf blades, xylem cells, stone cells, and calcium oxalate crystals could be used for the identification of the plants from which the commercial products were made. The method was proven to be quick, handy, simple, and convenient.     

Ku波段电磁涡旋相控阵列天线设计

为了能产生性能更好携有轨道角动量的涡旋电磁波,采用微带天线技术,设计了一种新型的相控微带阵列天线.以同轴馈电的圆微带天线为单元,将8个、16个相同的单元天线等间隔的分布在一个同心圆上分别组成两个单圆环和一个双圆环结构的相控阵列天线,并采用等幅且同一环的相邻单元间相位差为常数的方式进行激励.通过电磁场全波仿真软件Ansoft HFSS建模并优化,单圆环和双圆环阵列结构均在中心频率为15 GHz处获得了携有轨道角动量的涡旋辐射方向图.结果表明:虽然单圆环结构的相控阵列天线可通过增加阵元数来改善电磁涡旋性能,但不可避免的造成更大的天线体积;而利用双圆环结构,由于增加一个内环设计自由度,结合内外环的协同优化仿真,通过设置适当的天线阵列结构和相位延迟,双圆环结构较单圆环结构产生的涡旋电磁波有更小的中心轴线开口张角,具有更强的涡旋方向性和更高的辐射增益.     

基于口面场分布函数的赋形天线设计

标准卡塞格伦天线的口径效率和截获效率之间存在矛盾,限制了天线效率的提高。采用特定的口面场分布函数对天线主副反射面进行赋形。设计了一副Ku频段的高效率、低剖面、短焦距的卡塞格伦天线,同时给出了一种口面场曲线随半径增大而快速下降,接近口面边缘时有所上升的口面场分布函数。仿真结果表明,文章所设计的赋形天线在Ku接收频段内效率大于66.2%,在Ku发射频段内效率大于67.53%,证实了这种赋形方法对天线效率有明显的改善。     

基于准MMIC技术的12～18GHz宽带VCO

提出了一种基于准MMIC技术的Ku波段宽带压控振荡器.该电路采用MMIC芯片和外加高Q值的超突变结变容管的方式,实现了覆盖整个Ku波段的超宽带的振荡信号输出.通过将MMIC技术与混合集成技术相结合的方法,大大降低了调试难度,更重要的是,克服了通用pHEMT MMIC工艺难于兼容高Q值的变容管对超宽带设计VCO的限制,在相位噪声和调谐频率线性度方面都有较大改善.该方法为微波、毫米波压控振荡器的设计提供了一个新的途径.     

造化神奇 丹甘香醇

该文主要介绍了酿造红曲古工艺历史资料的查询结果。红曲亦名丹曲，属生物科技含量较高的酿造制品。