星载数字化TDRSS/USB双模应答机设计与试验

介绍了跟踪与数据中继星系统(TFDRSS)中用户星TDRSS/USB双模应答机的功能和组成,在传统USB应答机和扩频应答机的基础上设计了一种数字化的星载TDRSS/USB双模应答机,具有TT&C和TDR两种工作模式.接收机采用了中频数字化的载波跟踪和解扩解调、伪码快速捕获和精确跟踪方法;发射机的相干载波产生和PM调制采用直接数字频率合成(DDS)方法;两种模式下共用了收发通道和部分FPGA.资源.新的设计方法使应答机的调试难度、稳定性、载波和伪码捕获速度、跟踪精度、测距时延误差、功耗、重量等指标均有改善.     

An active‐diode‐based CMOS rectifier for biomedical power harvesting applications

A fully integrated and near lossless CMOS rectifier, intended for inductively powered electronic medical devices, is presented. By making use of high‐performance active diodes fulfilling almost ideal switching (zero forward voltage drop) and circuit to be provided with negative resistance, the proposed design is able to achieve a maximum conversion efficiency of more than 90% when designed in a 0.18‐ µm standard CMOS process, without any special device requiring additional manufacturing procedures. As a result, the proposed design dramatically reduces the production cost. Estimations in all aspects regarding the performance of the rectifier are given in this paper. Experimental results from the fabricated chip are also included in this paper. Copyright © 2010 John Wiley & Sons, Ltd.     

基于多通道阵列处理的二次雷达混扰信号分选

针对应答脉冲信号的同步干扰(即混扰)造成二次雷达询问机解码错误的问题,提出了基于多通道阵列处理的混扰信号分选算法。首先建立了询问机天线使用多通道阵列的混扰信号模型,在此基础之上给出了应答机个数及其到达角估计算法,并提出了基于最大似然估计的应答信号分选算法。仿真结果表明,该算法能够从混扰信号中同时准确分离多个应答信号,性能明显优于FastICA算法。当信噪比高于10 dB时,所提算法的分离指数比FastICA算法至少低10 dB。     

遗传算法在载波排列优化中的应用研究

卫星转发器的固态放大器(Solid State Power Amplifier,SSPA)或行波管放大器(Traveling Wave Tube Amplifier,TWTA)产生的非线性互调噪声会对有用载波进行干扰。为了使非线性互调噪声对有用载波的干扰最小,提高卫星通信质量,提出了基于遗传算法的载波排列优化方法。简述了遗传算法原理,分析了载波排列优化的基本原则,阐述了该方法的实施步骤,进行了仿真实验,同时分析了载波排列规律。     

应答着陆系统测角误差分析

应答着陆系统(Transponder Landing System,TLS)是一种基于应答机的精密进近着陆引导系统,采用相位干涉仪测角原理获得飞机的方位和仰角信息。从应答着陆系统的基本测角原理入手,分析了该系统的测角精度和误差来源。重点分析了因接收通道不平衡和多基线干涉仪测角的相位模糊引起的相位误差,并针对各自的特点提出了消除接收通道失衡和噪扰条件下解相位模糊的办法。通过计算机仿真验证了理论分析的正确性。     

大气机高度输出接口电路的设计

为完成俄制大气机与国产航管应答机的交连,设计了由单片机、A/D转换器、电平转换电路、驱动电路、隔离电路和电源等电路组成的俄制大气机高度输出接口板电路。采取数据校准和抗干扰技术,简化硬件电路,提高高度数据转换精度和系统的抗干扰能力。实验表明,该接口电路实现了高度数据的数字化,能够将俄制大气机输出的模拟高度电平信号转换成满足国产航空应答机要求的数字编码信号。     

应答器设备的原理及应用

首先介绍了应答器的应用背景和组成,然后分析了应答器的原理以及技术指标,最后总结了应答器的设置原则,旨在确保应答器在列车运行控制系统中应用的完整性,进而保证列车的运行安全。     

Deep‐space communications with a 2‐hop downlink with high link‐availability

We recall and discuss the theory of a 2‐hop downlink in deep‐space communications. The first hop (length d₁) links the deep‐space spacecraft to either a geostationary satellite or to a low Earth orbiting satellite. The second hop (length d₂, with d₂ ? d₁) links the satellite to the Earth receiver through a transparent or regenerative transponder, in slant paths affected by troposphere attenuation. If we adopt a BPSK or QPSK modulation scheme and the same carrier frequencies in the two hops with a transparent transponder, a particular value of the carrier frequency makes the noise‐to‐signal ratio minimum. A better choice is to assign a low carrier frequency (X‐band) to the second hop and a high one (W‐band) to the first hop. A 2‐hop downlink is superior to a 1‐hop downlink with a large power gain proportional to (d₁/d₂)² ? 1 at high microwave frequencies and large troposphere attenuation (high link‐availability). Shannon's capacity theorem provides the same large gain independently of the choice of the carrier frequencies in the two hops, if we use a regenerative transponder. The carrier frequencies of a 2‐hop downlink need not be those reserved to deep‐space communication, because the spacecraft could communicate as if it were transmitting ‘from the Earth’ through a conventional satellite connection. We have applied the theory to a first‐order design in the frequency range 10–100 GHz, slant path elevation angles 30°, 45° and 90° at Gera Lario or Fucino (Italy), and downlinks form Mars and Saturn, although the general findings and methodology are of global applicability. Copyright © 2005 John Wiley & Sons, Ltd.     

水下应答器定位的正则化数值算法研究

为解决线性化平差估计和高斯牛顿法求解水下应答器绝对坐标不稳定的问题,根据水下网型布设,提出将正则化数值算法应用于水下应答器定位。相比于传统非线性正则化算法,该算法将正则化约束只作用于病态方向即Z方向,在保证解决水下非线性病态的同时提高了传统非线性正则化算法的收敛效率。算法的正则化参数通过调整信赖域半径来确定。最后采用南海水下实测数据进行验证,结果表明,非线性正则化算法能够提高线性化平差估计的求解精度,收敛效率优于传统非线性正则化算法。     

二次定位技术在OBC勘探施工中的应用

在物探0BC勘探施工中,测量工作一般只能提供接收线上检波点瞬间离开定位船的坐标,为了准确得到沉到海底的接收线检波点的坐标,需要对检波点进行重新测量,通过二次定位得到的检波点坐标为地震资料的解析提供了可靠的保证.本文介绍了二次定位系统的硬件组成、工作原理和在OBc勘探中的使用方法及注意事项.