A compact transmit/receive switch for 2.4 GHz reader-less active RFID tag transceiver

Radio frequency identification(RFID) is a ubiquitous identification technology nowadays. An on-chip high-performance transmit/receive(T/R) switch is designed and simulated in 0.13-μm CMOS technology for reader-less RFID tag. The switch utilizes only the transistor width and length(W/L) optimization, proper gate bias resistor and resistive body floating technique and therefore,exhibits 1 d B insertion loss, 31.5 d B isolation and 29.2 d Bm 1-d B compression point(P1d B). Moreover, the switch dissipates only786.7 n W power for 1.8/0 V control voltages and is capable of switching in 794 fs. Above all, as there is no inductor or capacitor used in the circuit, the size of the switch is 0.00208 mm2 only. This switch will be appropriate for reader-less RFID tag transceiver front-end as well as other wireless transceivers operated at 2.4 GHz band.

Downlink MBER Transmit Beamforming Design Based on Uplink MBER Receive Beamforming for TDD-SDMA Induced MIMO Systems

The downlink minimum bit error rate (MBER) transmit beamforming is directly designed based on the uplink MBER receive beamforming solution for time division duplex (TDD) space-division multiple-access (SDMA) induced multiple-input multiple-output (MIMO) systems, where the base station (BS) is equipped with multiple antennas to support multiple single-antenna mobile terminals (MTs). It is shown that the dual relationship between multiuser detection and multiuser transmission can be extended to the rank-deficient system where the number of users supported is more than the number of transmit antennas available at the BS, if the MBER design is adopted. The proposed MBER transmit beamforming scheme is capable of achieving better performance over the standard minimum mean square error transmit beamforming solution with the support of low-complexity and high power-efficient MTs, particularly for rank-deficient TDD-SDMA MIMO systems. The robustness of the proposed MBER transmit beamforming design to the downlink and uplink noise or channel mismatch is investigated using simulation.

Time Domain Analysis of Transmit/Receive Dipole Pair Array

We introduce a new transmit/receive dipole pair array to obtain a compact quasi\|monostatic antenna structure for ground penetrating radar systems. And we analyze this transmit/receive dipole pair array in time domain. The numerical results show that if the distance between the transmit antenna and receive antenna is appropriate the array configuration is adoptable.

ROBUST OPTIMIZATION OF TRANSMIT/RECEIVE BEAMFORMER FOR MIMO DOWNLINK WITH IMPERFECT CSI AT BASE STATION

A robust scheme is proposed to jointly optimize transmit/receive beamformers for Mul-tiple Input Multiple Output(MIMO) downlinks where the available Channel State Information(CSI) at Base Station(BS)(CSIBS) is imperfect.The criterion is to minimize the sum Mean Square Error(sum-MSE) over all users under a constraint on the total transmit power,which is a non-convex and non-linear problem.Observing from the first order optimization condition that the optimal trans-mit/receive beamformers are mutually dependent,the transmit/receive beamformers for each user are updated iteratively until the sum-MSE is minimized.Simulation results indicate that the proposed scheme can effectively mitigate the system performance loss induced by imperfect CSIBS.

Cognitive anti-jamming receiver under phase noise in high frequency bands

This paper investigates the jamming sensing performance of the simultaneous transmit and receive based cognitive anti-jamming(SCAJ) receiver impaired by phase noise in local oscillators(LO) over fading channels. Firstly, energy detection(ED)based on the jamming to noise ratio(JNR) of the high frequency bands SCAJ receiver with phase noise under different channels is analyzed. Then, the probabilities of jamming detection and false alarm in closed-form for the SCAJ receiver are derived. Finally,the modified Bayesian Cramer-Rao bound(BCRB) of jamming sensing for the SCAJ receiver is presented. Simulation results show that the performance degradation of the SCAJ system due to phase noise is more severe than that due to the channel fading in the circumstances where the signal bandwidth(BW) is kept a constant. Moreover, the signal BW has an effect on the phase noise in LO, and the jamming detection probability of the wideband SCAJ receiver with lower phase noise outperforms that of the narrowband receiver using the same center frequency. Furthermore,an accurate phase noise estimation and compensation scheme can improve the jamming detection capability of the SCAJ receiver in high frequency bands and approach to the upper bound.

Throughput-based mode switching for MIMO ARQ systems in presence of transmit correlation

The mode switching between spatial multiplexing （SM） and space-time block code （STBC） diversity is investigated for the multiple-input multiple-output （MIMO） automatic repeat request （ARQ） system. Five important practical factors are considered in the proposed switching scheme： transmit correlation, ARQ technique, packet loss probability （PLP） constraint, discrete rate transmission （DRT） and channel coding. Under the spatially correlated channel, the distributions of the post signal-to-interference-plus- noise ratio （SiNR） for the SM mode and the STBC mode are obtained by using Gamma approximations. Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed, based on which the mode switching algorithm is proposed to improve the spectral efficency. In the simulation, the correction of the expressions is first verified. Then, the significant gain observed by the proposed algorithm is presented. Since the switching point is the key parameter to implement the mode switching, this paper also shows how the switching point is affected by the practical factors considered.

Analysis of Packet Sending and Receiving by Layer 3 Ethernet Switch CPU

Designing an Ethernet switch that can assure normal interaction of protocol packets between switches in a network environment of massive traffic is an important matter. Taking the L3 Ethernet switch based on Application Specific Integrated Circuit (ASIC) as an example,this article analyzes several typical issues about packet receiving and sending by the CPU in a multi-progress environment,including CPU load,software and hardware queue settings,and communication mechanism between CPU and the switch chip. This article gives solutions to these issues mentioned above. The solutions are applicable to Network Processor (NP) issues as well.

Performance evaluation of MIMO-OFDM system based on time-switched transmit diversity

In this paper, a time-switched space-time （TSST） coded orthogonal frequency division nmltiplexing （OFDM） scheme against the time-varying channels is proposed. In the TSST-OFDM scheme, it is equipped with four transmit antennas, but only double of them are used for coding in every time slot. It is shown that the signal to inter-antenna interference ratio is a function of Doppler frequency in time-varying channels for a given space-time code. The analyses and simulations results validate that the proposed scheme not only gets time- switched diversity and lower decoding complexity, but also suffers less time-varying impairments. Hence, it ex- hibits better performance than quasi-orthogonal space-time coded scheme.

Performance Analysis of Uplink Massive Spatial Modulation MIMO Systems in Transmit-Correlated Rayleigh Channels

In this paper,the performance of uplink multiuser massive multiple-input multipleoutput(MIMO)system with spatial modulation over transmit-correlated Rayleigh fading channel is investigated,where a large number of antennas are deployed at the base station and linear zero-forcing(ZF)receiver is employed for detection.By taking the transmit correlation and the randomness of shadow fading in to account,the bit error rate(BER)performance of the system is analyzed.According to the performance analysis,an approximated expression of overall average BER of the system is attained.Besides,asymptotic performance is studied and the corresponding BER expression at high signal-to-noise ratio is derived.On this basis,the diversity gain of the system can be obtained for performance evaluation.Simulation results show that the derived theoretical expressions match the simulated values well,which verifies the correctness of our analysis.

A High-Elasticity Router Architecture with Software Data Plane and Flow Switching Plane Separation

Routers have traditionally been architected as two elements: forwarding plane and control plane through For CES or other protocols. Each forwarding plane aggregates a fixed amount of computing, memory, and network interface resources to forward packets. Unfortunately, the tight coupling of packet-processing tasks with network interfaces has severely restricted service innovation and hardware upgrade. In this context, we explore the insightful prospect of functional separation in forwarding plane to propose a next-generation router architecture, which, if realized, can provide promises both for various packet-processing tasks and for flexible deployment while solving concerns related to the above problems. Thus, we put forward an alternative construction in which functional resources within a forwarding plane are disaggregated. A forwarding plane is instead separated into two planes: software data plane(SDP) and flow switching plane(FSP), and each plane can be viewed as a collection of "building blocks". SDP is responsible for packet-processing tasks without its expansibility restricted with the amount and kinds of network interfaces. FSP is in charge of packet receiving/transmitting tasks and can incrementally add switching elements, such as general switches, or even specialized switches, to provide network interfaces for SDP. Besides, our proposed router architecture uses network fabrics to achievethe best connectivity among building blocks,which can support for network topology reconfiguration within one device.At last,we make an experiment on our platform in terms of bandwidth utilization rate,configuration delay,system throughput and execution time.

T/R组件故障对DBF影响分析及维护策略研究

针对相控阵雷达T/R组件故障数低于总数10%时的可维护性和维护时机问题,分析通道故障对数字波束形成的影响规律,提出保持雷达性能不降级的维护策略。首先,基于面阵结构分别建立发射数字波束形成(DBF)数学模型和基于最小均方(LMS)算法的接收数字波束形成数学模型。其次,仿真验证T/R组件处于正常和部分失效2种状态时的波束形成性能,采用5个指标对比分析故障数量和故障区域对接收DBF性能和雷达探测性能的影响。最后,分析其内在规律,提出维护策略,为科学精细维修与作战效能发挥提供理论依据和决策支持。

面向阵列级同时同频收发的宽带自干扰空域抑制

具备阵列级同时同频收发能力的多功能一体化平台,面临发射阵列对接收阵列的强自干扰问题。针对这一问题,该文设计了一种宽带自干扰空域抑制方法,构造了限制主波束增益损失条件下,最小化残余自干扰和噪声功率的非凸优化问题,提出了交替迭代的优化算法联合求解发射和接收数字波束成形系数,从理论上分析了所提算法的自干扰抑制极限性能,并给出了所提算法的计算复杂度。分析和仿真结果表明,给定2.4 GHz工作频率,100 MHz带宽,主波束增益损失限制在3 dB时,收发各30阵元的相控阵列宽带自干扰空域抑制能力,即有效各向同性隔离度达到168 dB,距离自干扰抑制性能极限差距7 dB。

PCM信号间歇收发互补设计与回波重构方法

间歇收发用于辐射式仿真中可以有效解决收发信号互耦的问题,但间歇收发会带来信号损失,导致相位编码信号距离像出现高旁瓣。为了解决这一问题,提出间歇收发互补序列设计方法,给出了收发序列参数设计方法,并对相位编码间歇收发回波进行重组拼接,消除间歇收发导致的回波缺失,获得了精确的目标距离像。仿真结果表明,收发互补设计及回波重组拼接能够准确重构回波,并且重构后互相关系数接近1,验证了所提方法的可行性与正确性。

基于小波变换的雷达脉冲间歇收发回波联合重构方法

进行内场测量时,间歇收发处理能有效解决因暗室尺寸导致的收发信号耦合,但该方法会造成目标回波被部分截断。在回波重构过程中,受暗室本身结构设计及吸波材料性能等因素的影响,回波中不可避免出现噪声干扰,使得重构性能降低。为提高回波重构的精确度,本文提出基于小波变换的雷达脉冲间歇收发回波联合重构方法,该方法结合间歇收发原理和Mallat算法,实现了低信噪比条件下LFM脉冲雷达信号的精确重构。仿真和实验结果表明,联合重构方法所得目标回波和一维距离像与完整脉冲保持一致,验证了本文方法的有效性。

高分辨二维成像声呐电子系统的设计与实现

针对海洋工程和开发中用于水下作业的机器人、自动潜水器等水下载体需要对海底地形地貌、障碍物、沉底目标或水中目标等进行成像,以获得目标轮廓等信息,或对水下运动目标进行跟踪和识别。然而,在光照条件低或水体混浊环境中,光学成像难以获得较好的效果,而成像声呐几乎不受其影响就能获得较好的高分辨声呐图像。依据此需求,论证了成像声呐的主要技术指标,设计并实现了成像声呐的发射单元和接收单元的电子系统,对其电路性能测试和成像声呐的水池实验验证了方案设计的合理性、可行性,表明成像性能满足系统要求。

250 kHz收发一体化水声换能器

针对水声领域对兼有高效发射和高灵敏度接收、收发工作频带重合、结构一体化高频水声换能器的应用需求,该文研制了一种高灵敏度收发一体水声换能器。该换能器由发射单元和接收单元两部分嵌套组成,发射单元采用1-3复合材料,接收单元采用单金属板压电陶瓷阵列结构。首先,通过有限元模拟确定发射和接收单元频率使其满足收发一体条件;其次接收单元采取改变压电陶瓷结构提升了机电耦合系数,从而提升接收灵敏度;最后制备了换能器样机并进行测试。结果表明,发射单元共振频率和接收单元反共振频均在250 kHz附近,接收灵敏度最高可达-173:5 dB,满足收发一体条件和高灵敏性能。

阵列自由度欠定条件下雷达干扰对消方法及性能分析

针对雷达、数据链等分时信息系统发射时隙产生的自干扰影响非合作干扰对消权值问题,分析辅助天线阵列自由度影响对消暂态权值收敛特性,提出非合作干扰对消权值保持方法。考虑辅助天线通道与主天线通道异构场景,定量推导非合作干扰对消输出功率稳态性能边界与影响因素。结果表明,权值保持技术避免发射自干扰影响,增加辅助天线数量提升对消比和对消收敛特性。所提方法提升了阵列自由度欠定条件下非合作对消稳态和暂态性能,对于雷达非合作干扰对消设计具有现实指导意义。

MCSEM勘探发射电流扰动实验仿真研究与设计

海洋可控源电磁法(MCSEM)勘探中发射电流质量是影响接收信号质量和勘探效率的重要因素。基于COMSOL Multiphysics虚拟仿真平台,研究了MCSEM勘探发射电流强度和形态参数对电场响应强度的影响。结果表明,发射电流强度的不稳定波动会降低接收信号的基波和谐波分量电场响应强度,主要影响中远偏移距电场值;发射电流波形的上升和下降沿的增加对接收信号基波和低次谐波分量影响较小,但会显著降低高次谐波分量的电场响应强度,主要影响中近偏移距电场值。通过仿真分析,MCSEM勘探中发射电流变化对接收信号的影响,可为实际勘探中发射波形异常时振幅随偏移距变化曲线的解释提供帮助。

水下双层加肋圆柱壳全空间收发分置散射声场快速预报方法

针对水下双层加肋圆柱壳的全空间收发分置散射声场求解,提出了一种快速预报方法。该方法将散射声场表示为声散射传递函数与声源密度函数的乘积,以目标表面网格信息、少量的仿真或测试多基地散射声压数据作为已知信息,借助数值积分、矩阵理论、最小二乘法对其他收发分置散射声场进行预报。分别以有限元仿真和试验测试的散射声压数据作为输入,对水下双层加肋圆柱壳的多基地散射声场进行了计算,并与完全采用有限元方法的计算结果进行了对比。结果表明:该方法在目标表面结构和部分散射声场数据已知条件下能对目标的全空间收发分置散射声场进行预报;已知散射声压数据量越多,计算频率越低,预报精度越高。

新型三维组合式发射线圈的设计与实验

多维无线电力传输是胃肠道胶囊机器人发展的关键。为了解决新型胶囊机器人功能不断增加,而传统三维接收线圈占用内部空间过大的问题,本文提出了一种三维组合式发射线圈,能够通过调制通过各维线圈的电流来产生动态的三维磁场。本文首先介绍了无线供能系统的工作原理,然后对发射系统产生的空间磁场进行了有限元分析。最后利用搭建的实验平台进行实验,验证了仿真结果的准确性并确定了接收线圈感应最大接受电压的姿态。试验结果表明,当发射系统在中心点处产生相等的三维磁场分量时,负载接收能量超过630 mW。此外,发射系统附近边缘区域的位置稳定性超过80%,确保胶囊机器人能够平稳的运行。