基于多级维纳滤波的机载共形阵雷达杂波抑制方法研究

目前,多级维纳滤波器是一种收敛速度最快的降秩空时自适应处理算法,但它只适合于处理平稳随机信号,不能直接用于抑制非均匀的机载共形阵雷达杂波。该文在分析共形阵雷达杂波特性的基础上,提出采用俯仰向空域滤波改善杂波的非均匀性,改进了传统的协方差矩阵加权算法,最后形成了一种基于俯仰向空域滤波的协方差矩阵加权多级维纳滤波算法,用于抑制共形阵雷达杂波。仿真结果表明,该文方法抑制共形阵雷达杂波的综合性能优于现有其他方法,且计算复杂度低,收敛速度快,便于工程实现,在共形阵雷达杂波抑制中具有实际应用前景。     

应用于3.3kV IGBT的线性渐变掺杂结终端扩展的设计与优化

本文将线性渐变掺杂结终端扩展（LG-JTE）技术用于3.3kV IGBT并进行了试验验证。和采用多次光刻和离子注入传统结终端扩展技术不同,LG-JTE只用一张注入窗口宽度随与主结的距离线性变化的掩膜版。结合仿真设计了采用LG-JTE的IGBT,并在国内工艺平台上成功流片,其测试耐压达到3.7kV,接近理想的平行平面情形的耐压。     

Field Measurements with a 5.25 GHz Broadband MIMO-OFDM Communication System

Theoretical capacity calculations and corresponding simulations show significant capacity/throughput gains from MIMO systems. Whether these gains are achievable in a real system, deployed in a practical environment, depends on a variety of factors, such as the choice of the communication algorithms, analog impairments and the "quality" of the wireless channel to sustain MEMO communications. In this paper, a 5.25 GHz broadband MIMO-OFDM testbed is described along with field measurements conducted with it. The MIMO-OFDM communication algorithms and also the impact of analog impairments on the performance of the system are described. Detailed system calibration results are described which serve as a baseline for results of field measurements. The results of wireless measurements are compared with the theoretical capacity, computed with the channel estimates obtained during the demodulation process. The average achievable capacity in the indoor wireless environment is shown to be 9.97 bps/Hz (bits per sec per Hz) while the capacity loss due to analog impairments and the choice of algorithms is about 2.33 bps/Hz. Also, field measurements conducted with the system in various environments are presented comparing the average throughput/capacity achieved in each of these environments.     

几种数据压缩算法的比较

对几种数据压缩算法进行了总结,并针对实验数据表对其压缩率进行了比较。     

Analytical expressions for intermodulation distortion of a MESFET small-signal amplifier using the nonlinear Volterra series

Using the nonlinear Volterra series representation, analytical expressions for the third-order intermodulation distortion power and intercept point for a MESFET small-signal amplifier are derived when its equivalent circuit is bilateral and includes the gate-to-drain capacitance (C_gd) explicitly as a nonlinear element. Previously developed analytical expressions treated C_gd as a linear element or incorporated it as a part of gate-to-source and drain-to-source capacitances (C_gs and C_ds). These new analytical expressions are then compared with experimental data and good agreement is obtained. The analytical expressions are also used to study the variation of intermodulation distortion with input power and frequency, and the effect of the individual nonlinear elements in the MESFET’s equivalent circuit.     

单频网分布式外辐射源雷达技术

外辐射源雷达的研究和应用正朝着由单收发对向多收发对体制发展。作为该型雷达的一种重要机会照射源,新一代数字广播电视广泛采用单频(或同频)网覆盖方式,其内在决定了基于此的外辐射源雷达是分布式和网络化的。鉴于照射源单频网配置下外辐射源雷达不同寻常的工作和处理方式,该文归纳提出了单频网分布式外辐射源雷达的概念,阐述了该型雷达的主要特性以及所面临的核心问题,并就部分关键技术讨论了若干可供尝试的解决方案,结合原理实验结果展示了该型雷达的可行性,最后提出了集外辐射源雷达探测网的四网融合的概念并展望了其应用前景。      

Half-Rate Duobinary Transmitter Architecture for Chip-to-Chip Interconnect Applications

For a high speed duobinary transmitter clock frequency defines the transmission limit. A conventional duobinary transmitter needs a clock frequency equal to the data rate. In this work we propose a duobinary transmitter that uses a clock frequency half of the output data rate and hence achieves double the transmission rate for a given clock frequency as compared to a conventional duobinary transmitter. In the proposed transmitter the duobinary precoder is integrated into the last stage of a tree structured serializer to combine two NRZ data streams at half the transmission data rate. Two modes for the precoder have been incorporated into the design. The first mode is applicable for data transmission over copper whereas the second mode is suitable for wavelength division multiplexed optical transmission. A DLL based clock multiplier unit is employed to produce the high frequency clock with 50% duty cycle needed for the precoding operation. It incorporates a clock generation logic with integrated duty cycle control. A charge pump with dynamic current matching and a high resolution PFD are employed to reduce static phase error in locking and hence achieves improved jitter performance. A new delay cell along with automatic mode selection is proposed. To cover a wide range of data rate, the DLL is designed for a wide locking range and maintains almost 50% duty cycle. The design is implemented in 1.8-V, 0.18 μm Digital CMOS technology with an f _T of 27 GHz. Simulations shows that, the duobinary transmitter circuit works up-to 10 Gb/s and consumes 60 mW of power.     

Characteristics of planar n-p junction diodes made bydouble-implantations into 4H-SiC

Double implantation technology consisting of deep-range acceptor followed by shallow-range donor implantation was used to fabricate planar n⁺-p junction diodes in 4H-SiC. Either Al or B was used as the acceptor species and N as the donor species with all implants performed at 700°C and annealed at 1650°C with an AlN encapsulant. The diodes were characterized for their current-voltage (I-V) and capacitance-voltage (C-V) behavior over the temperature range 25°C-400°C, and reverse recovery transient behavior over the temperature range 25°C-200°C. At room temperature, the B-implanted diodes exhibited a reverse leakage current of 5×10^-8 A/cm² at a reverse bias of -20 V and a carrier lifetime of 7.4 ns     

BN–Graphene Composites Generated by Covalent Cross‐Linking with Organic Linkers

Composites of boron nitride (BN) and carboxylated graphene are prepared for the first time using covalent cross‐linking employing the carbodiimide reaction. The BN_1–xG_x (x ≈ 0.25, 0.5, and 0.75) obtained are characterized using a variety of spectroscopic techniques and thermogravimetric analysis. The composites show composition‐dependent electrical resistivity, the resistivity decreasing with increase in graphene content. The composites exhibit microporosity and the x ≈ 0.75 composite especially exhibits satisfactory performance with high stability as an electrode in supercapacitors. The x ≈ 0.75 composite is also found to be a good electrocatalyst for the oxygen reduction reaction in fuel cells.