调幅一调频收音机的新型调试方法

在调幅-调频收音机安装完成后,会遇到各种问题,严重的影响到收听的效果和质量。因此需要对其进行精确地调试及检测,进而保证收音机的接收效果。文中分析了S205-2T型收音机在AM波段和FM波段的调试方法,并详细介绍了相应的调试步骤及技巧。经实践验证,这些新型调试方法可以快速准确的调试收音机,极大改善接收效果,并且为同类收音机的调试检测工作提供借鉴。     

相位调制平行光延迟器的微波高精度测量

提出了一种新的相位调制平行光延迟器,使用双电极马赫-曾德尔调制器进行高精度测量微波信号到达角及等效到达时间差,建立了一个理论模型来分析系统的测量精度监控。空间时延测量转换成两个微波信号之间的相移,精度监测的结果显示,对从5°~165°相移的测量误差小于3.1°,具有重要的应用价值。     

1.5kW户用光伏高频逆变器研制

分析了一种具有中间储能环节的高频隔离逆变拓扑结构,该电路能实现前后级解耦,适用于光伏发电系统。前级DC/DC高频升压电路基于有限双极性调制,实现升压功能;后级采用双极性SPWM逆变技术,结合电压平均值反馈使输出电压稳定。详细介绍了高频变压器和LC滤波电路的设计方法,最后搭建了1.5k W高频逆变实验平台,实验结果显示,逆变器具有输出电压稳定,波形畸变小等优点。     

离散Hopfield神经网络的PWM型脉冲流技术实现

研究了离散Hopfield神经网络的PWM(脉冲宽度调制)型脉冲流技术实现。利用MOS开关管和电压比较器实现了离散Hopfield神经网络，并提出了利用离散Hopfiled神经网络实现自联想记忆时相应的PWM型脉冲流电路。所提出的电路结构简单，易于芯片间通讯及系统扩展。     

四进制VMCK调制信号的传输仿真

甚小线性调频键控(VMCK)是一种高效的超窄带调制技术,具有窄带占用,强边带抑制,数据传输效率高等优点。频分复用技术是一种常用的提高频带利用率手段,在超窄带的通信结构基础上,根据VMCK调制原理,利用Simulink搭建超窄带系统的四路信号复用系统,并进行分析。     

CPM信号的微积分解调算法分析

连续相位调制（Continuous Phase Modulation）是一类包络恒定且相位连续的调制方式,具有很高的带宽和功率利用率,优良的包络和相位特性使其适用于空间通信。在分析CPM信号的模型基础上,研究了基于微积分的代数运算方法来完成对CPM信号的解调,该方法几乎不需要任何的先验信息和参数信息就能实现信号的盲解调,目的能够降低接收机的复杂度,是一种优秀的CPM信号解调方式。     

A novel high-voltage device structure with an N~+ ring in substrate and the breakdown voltage model

A novel high-voltage device structure with a floating heavily doped N~+ ring embedded in the substrate is reported,which is called FR LDMOS.When the N~+ ring is introduced in the device substrate,the electric field peak of the main junction is reduced due to the transfer of the voltage from the main junction to the N~+ ring junction, and the vertical breakdown characteristic is improved significantly.Based on the Poisson equation of cylindrical coordinates,a breakdown voltage model is developed.The numerical results indicate that the breakdown voltage of the proposed device is increased by 56%in comparison to conventional LDMOS.     

基于FPGA的GMSK调制设计研究

高斯滤波最小频移键控（GMSK）调制方式具有很好的频谱性能和恒包络特性,这两种特性使得GMSK在存在邻道干扰、非线性功率放大器的系统中具有很好的性能,并在Altera公司的CycloneII系列的FPGA上实现了设计,在此着重介绍了FPGA上滤波器的设计。     

Symmetry Modulation and Enhanced Multiferroic Characteristics in Bi1‐xNdxFeO3 Ceramics

BiFeO₃ is recognized as the most important room temperature single phase multiferroic material. However, the weak magnetoelectric (ME) coupling remains as a key issue, which obstructs its applications. Since the magnetoelectric coupling in BiFeO₃ is essentially hindered by the cycloidal spin structure, here efforts to improve the magnetoelectric coupling by destroying the cycloidal state and switching to the weak ferromagnetic state through symmetry modulation are reported. The structure is tuned from polar R3c to polar Pna2₁, and finally to nonpolar Pbnm by forming Bi_1‐xNd_xFeO₃ solid solutions, where two morphotropic phase boundaries (MPBs) are detected. Greatly enhanced ferroelectric polarization is obtained together with the desired weak ferromagnetic characteristics in Bi_1‐xNd_xFeO₃ ceramics at the compositions near MPBs. The change of magnetic state from antiferromagnetic (cycloidal state) to ferromagnetic (canted antiferromagnetic) is confirmed by the observation of magnetic domains using magnetic force microscopy. More interestingly, combining experiments and first‐principles‐based simulations, an electric field‐induced structural and magnetic transition from Pna2₁ back to R3c is demonstrated, providing a great opportunity for electric field‐controlled magnetism, and this transition is shown to be reversible with additional thermal treatment.     

Research of the equivalent relationship between the space vector and the triangular carrier-based PWM modulation strategies in the flying capacitor multilevel inverters

ABSTRACT

The equivalent relationship between the carrier-based modulation (CBPWM) and the space vector modulation (SVPWM) based on the flying capacitor multilevel inverters has not been analysed systematically. Due to the redundancies of the flying capacitor multilevel inverters, this paper firstly focuses on the switching sequence and the working ratio of each switching state and then proposes a novel method of decomposing modulation wave. This method can distribute the ratio of redundancies arbitrarily to satisfy the requirements of the output. Taking three- and five-level inverters as examples, by injecting a zero-sequence voltage into the CBPWM modulation wave and then decomposing the new modulation wave, we can get the same sequence of SVPWM modulation. This method takes the advantages of using simple CBPWM to realise the complex output of SVPWM, such as double- and quadruple-frequency output. At last, we deduce the equivalent relationship between the SVPWM and CBPWM in n-level with an arbitrary number of segments. Experimental results verify the correctness of the equivalent relationship.