Low-Voltage Differentiator for VHF Filtering

In this paper a G _m -C resonator circuit is proposed which is based on a new current-mode differentiating concept, compatible with low voltage and very high frequency operation.A prototype 4th-order 200 MHz band pass filter has been fabricated using a 0.8 m CMOS process and shows a side-band rejection lower than –80 dB. This response confirms the feasibility of the proposed resonator in very-high frequency applications such as IF band pass sections of RF front-end circuits. The filter consumes less than 5.5 mW from a 2.7 V supply and the measured dynamic range is 57 dB at IM3 of 0.5%, where the active area is 0.12 mm².     

VHF宽带E类高效率功率放大器设计

使用ADS(Advanced Design System)软件仿真设计了基于28-V MOSFET器件的VHF频段30 MHz～80 MHz E类开关模式高效率功率放大器。输入端使用了宽带匹配,输出端通过开关改变后端的匹配电路和滤波器。电路实测:30 MHz～80 MHz输出功率3.2 W～7.1 W,效率从30 MHz的71.4%到80MHz的52.5%,并且具有优良的调幅线性度,可以将其应用到EER发射机。     

基于甚高频的语音增强算法研究

甚高频通信在民航中有广泛应用,但是它极易受到各种噪声的干扰,传统方法去噪效果差且没有消除固有干扰,提出了一种基于小波分析的自适应卡尔曼滤波算法。该算法在小波分析中提出了新阈值函数,在自适应卡尔曼滤波算法中增加了调节窗口长度的自适应因子,以此来调节滤波增益,可以有效地避免滤波发散。随机选择了某一时段4种不同频率的甚高频语音信号,并用提出的算法进行滤波处理,从信噪比、均方根误差、信号波形图和语谱图等方面进行分析。结果表明,该算法能够有效去除甚高频语音信号中的噪声,可以获得更高的信噪比和更小的均方根误差,进一步提升语音质量。     

流星余迹极低信噪比信号同步和补偿技术

在对超短波流星余迹极低信噪比模式的信道特性分析的基础上,针对采用M进制正交扩频序列的流星余迹通信系统的极低速通信模式,利用迭代信号处理原理,提出了频域迭代载波同步估计和信号补偿技术.接收机通过对存在频率偏移的长扩频序列进行相关的频率补偿,可以提高频域相关峰值,从而可以显著提高接收性能.理论研究和计算机仿真结果证明了该方法的有效性.     

MC-CDMA在VHF航空信道中的性能研究

文章分析多载波码分多址系统的信号传输模型和甚高频（VHF）航空信道模型，对多载波码分多址（MC-CDMA）系统在航空信道下的误码性能进行了研究和仿真。VHF航空通信信道拥挤，多径现象严重，时延和多普勒频移很大，MC-CDMA结合利用正交频分复用和码分多址技术的优点，能够有效的对抗多径干扰，并提供更大的通信容量，具有良好的应用前景。     

基于波瓣分裂的米波雷达低仰角测高方法及其应用

针对米波雷达的波束较宽、由于地面反射引起波瓣分裂,通常只能估高而不能测高这一难题,提出一种基于分裂波瓣的米波雷达低仰角测高方法——比相比幅法.该方法采用多个不同高度的测高天线,由于不同高度天线的分裂波瓣有一定的相位关系,利用该相位关系确定目标所在仰角区间;利用不同天线接收信号幅度进行比幅处理提取归一化误差信号;再查表得到目标的高度.分析地面起伏对测高精度的影响;推导不同阵地情况下的比幅误差曲线.将该方法应用于某型雷达,在我国首次成功地进行了米波雷达测高.试验结果表明该方法是行之有效的.     

小型无人机空地数据链系统的应用研究

设计了一种适用于小型无人机的空地数据链系统；文中提出了详细的系统设计方案，对数据链的传输方式、传输内容、传输流程等进行了研究；并给出了系统的软件设计和实现方法。     

More stable low gap a-Si:H layers deposited by PE-CVD at moderately high temperature with hydrogen dilution

In the present work, several series with variation of deposition parameters such as hydrogen dilution ratio, VHF-power and plasma excitation frequency f_exc have been extensively analyzed. Compared with “conventional” more-stable layers obtained at 200–250°C and high H₂ dilution ratios of about 10, it was observed that electrical transport properties after light-induced degradation of layers deposited at “moderately high” temperatures (300–350°C) are equivalent but required lower H₂ dilution ratios (between 2 and 4). As a consequence, the deposition rate of more stable layers obtained at moderately high temperatures is increased by a factor of 2. Moreover, optical gaps of a-Si:H deposited at 300–350°C are significantly lower (by approx. 10 meV); furthermore, they decrease with f_exc.     

Electrical and structural properties of nano-crystalline silicon intrinsic layers for nano-crystalline silicon solar cells prepared by very high frequency plasma chemical vapor deposition

Thin silicon intrinsic layers were deposited in the amorphous to nano-crystalline transition regime to investigate their structural and optoelectrical properties using the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique. Optical emission spectroscopy (OES) was primarily used to monitor the plasma properties during the deposition. The ratio Hα/Si^*$\mathrm{H}\alpha /{\mathrm{Si}}^{*}$, estimated from OES spectra, is closely related to the microstructure of the films. With the increasing plasma power from 10 to 50 W, the ratio Hα/Si^*$\mathrm{H}\alpha /{\mathrm{Si}}^{*}$ increases leading to nano-crystalline films. The ratio Hα/Si^*$\mathrm{H}\alpha /{\mathrm{Si}}^{*}$ decreases with the increase of process gas pressure at constant power of 15 and 30 W. The films were nano-crystalline at low pressure and became amorphous at high pressure.     

低压应用的高性能甚高频功率VDMOSFETs

采用梯形栅结构和难熔金属钼栅工艺 ,研制出了高性能 ,低电压工作 ,适用于移动通信的甚高频功率VDMOS场效应晶体管 .该器件在 175 MHz、 12 V低电压工作条件下 ,输出功率为 12 W,漏极效率为 70 % ,功率增益为 12 d B