140 GHz高速无线通信技术研究

太赫兹频段的宽带特性使得其在高速无线通信领域存在巨大的应用潜力,当前太赫兹通信存在的主要问题是辐射功率低、大气衰减严重及调制解调困难。该文在提出了基于肖特基二极管次谐波混频技术+16 QAM高速数字调制解调技术的太赫兹波超高速信息传输系统实现方案,该方案提高了太赫兹通信的频谱效率。并在国内首次实现了140 GHz无线通信实验系统,以实验方法验证了太赫兹信道的幅相失真特性完全满足高阶数字信号的传输要求。该系统在0.5 m距离上实现了10 Gbps无线传输实验和高清视频传输,辐射功率-3 dBm,系统误码率小于1e-6。     

对称型席夫碱类二茂铁衍生物的合成与性能研究

以二茂铁甲醇为原料,经Wittig反应后与2,6-(双胺基)-苯并[1,2-d-4,5-d′]双三唑-4,8(2H,6H)-二酮缩合,合成了一个D-π-A-π-D结构的二茂铁席夫碱类金属有机三阶非线性光学材料。化合物结构经1H NMR,MS表征确认。测定了该化合物的紫外-可见吸收光谱,用简并四波混频(DFWM)检测了其三阶非线性参数,检测波长为800 nm;脉冲宽度为80 fs。该化合物的三阶非线性极化率χ(3)值为3.67×10-13esu(静电单位),分子二阶超极化率γ值为3.49×10-31esu,表明该化合物具有良好的三阶非线性光学性能,优于现有的二茂铁类金属有机材料。探讨了分子结构对三阶非线性光学性能的影响,长共轭链、强电子离域能可提高分子三阶非线性光学性能。     

1.2V低功耗时钟发生器设计

基于整数分频锁相环结构实现的时钟发生器,该时钟发生器采用低功耗、低抖动技术,在SMIC 65 nm CMOS工艺上实现。电路使用1.2 V单一电源电压,并在片上集成了环路滤波器。其中,振荡器为电流控制、全差分结构的五级环形振荡器。该信号发生器可以产生的时钟频率范围为12.5～800MHz,工作在800 MHz时所需的功耗为1.54 mW,输出时钟的周期抖动为:pk-pk=75 ps,rms=8.6 ps;Cycle-to-Cycle抖动为:pk-pk=132 ps,rms=14.1 ps。电路的面积为84μm2。     

含氟三环NCS液晶材料的介电性能研究

为了探究液晶材料的介电性能,本文研究了4PPTGS和4PUTGS两种含氟三环NCS类液晶材料的介电各向异性和介电损耗。首先用精密LCR表(Agilent E4980A)测量液晶盒的电容并用双盒模型和液晶盒电容模型得到4PPTGS和4PUTGS两种液晶材料的平行和垂直介电常数,再由电压-电容特性曲线得到它们的阈值电压,并进一步探讨了介电各向异性和阈值电压对温度的依耐性;然后,在20 Hz~10kHz范围内研究了外加电压频率对液晶材料介电损耗的影响,两种液晶材料在1kHz左右都存在介电损耗峰值,为了减小器件的功耗和提升器件的质量,液晶材料应选择在介电损耗小的频率下工作;最后,通过对平行和垂直排列向列相盒中液晶材料在不同电压下介电损耗的测试与分析,介电损耗的变化是由于在外加电场下液晶分子固有偶极矩的取向极化引起的,介电损耗值的大小与液晶分子的排列状态密切相关。此项研究对提升液晶材料在应用中的介电性能具有一定的指导意义。     

用高压拉曼光谱方法研究β-胡萝卜素相变

为了探究β-胡萝卜素在高压下是否会发生相变,进行了0～30 Gpa压强范围内β-胡萝卜素的高压拉曼光谱实验。通过评估不同压强范围内拉曼光谱频移-压强的线性函数变化来判断β-胡萝卜素是否发生相变。研究表明,当压强升至约为7 Gpa以及14 Gpa时,β-胡萝卜素分子的频移-压强线性函数方程发生了变化,即发生了相变。通过分析频移-压强函数线性关系是否发生变化来判断相变,是简捷、方便的技术方法。关于纯β-胡萝卜素压力相变的研究,暂未检索到相关报道。     

InGaAs／GaAs自组织量子点光致发光特性研究

用PL谱测试研究了GaAs和不同In组份InxGa1-xAs(x=0.1,0.2,0.3)覆盖层对分子外延生长的InAs/GaAs自组织量子点发光特性的影响,用InxGa1-xAs外延层覆盖InAs/GaAs量子点,比用GaAs做 其发光峰能量向低有端移动,发光峰半高度变窄,量子点发光峰能量随温度的红移幅度较小,理论计算证实这是由于覆盖层InxGa1-xAs减小了InAs表面应力导致发光峰红移,而In元素有效抑制了InAs/GaAs界面组份的混杂,量子点的均匀性得到改善,PL谱半高宽变窄,用InGaAs覆盖的In0.5Ga0.5As/GaAs自组织量子点实现了1．3μm发光,室温下PL谱半高宽为19．2meV,是目前最好的实验结果。     

基于2051单片机的激光对抗模拟器设计

介绍了以2051单片机为控制核心的激光对抗模拟器的结构及设计原理,具体阐述了其发射、接收处理、声光报警装置、供电电路的原理及电路实现,并说明了2051的协调处理过程。     

宽带高光束质量KrF激光器的实验研究

利用SBS作为相位共轭镜,对宽带KrF自由振荡激光器的光束质量进行了改善。在KrF激光能量为36mJ,脉宽为13.7ns,束散角为9.5倍衍射限的条件下,获得输出能量为20.8mJ,脉宽为4.3ns,束散角为6.4倍衍射限的高光束质量宽带KrF激光。     

Miniature heart cell force transducer system implemented in MEMS technology

A fully submersible force transducer system for use with isolated heart cells has been implemented using microelectromechanical systems (MEMS) technology. By using integrated circuit fabrication techniques to make mechanical as well as electrical components, the entire low-mass transducer is only a few cubic millimeters in size and is of higher fidelity (approximately 100 nN and 13.3 kHz in solution) than previously available. When chemically activated, demembranated single cells attached to the device contract and slightly deform a strain gauge whose signal is converted to an amplified electrical output. When integrated with a video microscope, the system is capable of optical determination of contractile protein striation periodicity and simultaneous measurement of heart cell forces in the 100-nN to 50-microN range. The average measured maximal force was Fmax = 5.77 +/- 2.38 microN. Normalizing for the cell's cross-sectional area, Fmax/area was 14.7 +/- 7.7 mN/mm2. Oscillatory stiffness data at frequencies up to 1 kHz has also been recorded from relaxed and contracted cells. This novel MEMS force transducer system permits higher fidelity measurements from cardiac myocytes than available from standard macro-sized transducers.     

Smooth side-match classified vector quantizer with variable blocksize

Although the side-match vector quantizer (SMVQ) reduces the bit rate, the image coding quality by SMVQ generally degenerates as the gray level transition across the boundaries of the neighboring blocks is increasing or decreasing. This study presents a smooth side-match method to select a state codebook according to the smoothness of the gray levels between neighboring blocks. This method achieves a higher PSNR and better visual perception than SMVQ does for the same bit rate. Moreover, to design codebooks, a genetic clustering algorithm that automatically finds the appropriate number of clusters is proposed. The proposed smooth side-match classified vector quantizer (SSM-CVQ) is thus a combination of three techniques: the classified vector quantization, the variable block size segmentation and the smooth side-match method. Experimental results indicate that SSM-CVQ has a higher PSNR and a lower bit rate than other methods. Furthermore, the Lena image can be coded by SSM-CVQ with 0.172 bpp and 32.49 dB in PSNR.