多时滞离散切换系统反馈镇定

研究一类具有多时滞子系统的离散切换系统的稳定性分析和反馈镇定问题。通过状态变量的转换，将时滞切换系统变为不含时滞项的切换系统。以LMI形式给出了在任意切换信号作用下多时滞离散切换系统渐近稳定的充分性条件，以及系统状态反馈镇定、输出反馈镇定的控制器设计。并通过两个仿真实例验证所设计控制方案的有效性。     

Comprehensive study of multiband unconditional stabilization of common-source and common-gate MESFET transistors using feedback

The use of a new feedback scheme to achieve unconditionally stable MESFET transistors from 0 GHz until cutoff is presented. The methodology is applied for both common-source and common-gate MESFET transistor configurations. Analytical formulation of the stabilization methodology is presented. In addition, two coplanar-waveguide-based amplifiers were designed to operate at Ka-band, monolithically fabricated, and tested, thus, verifying the methodology. The study includes the effects of the bias change on the feedback amplifier stability performance.     

基于自适应反步跟踪的反馈调整稳定性控制算法

当飞机在大回环飞行中,由于受到空气动力学的扰动较大,需要进行飞行姿态稳定性控制,传统方法采用分段线性化控制方法,在大扰动条件下,飞行过程中各段的控制误差不断方法,导致飞行稳定性不好。提出一种基于自适应反步跟踪的飞行器反馈调整稳定性控制算法。构建大回环飞行中的飞行稳定性控制的参量模型系统,考虑外界干扰的情况下,进行飞行器反馈调整稳定性控制目标函数构建,采用自适应反步跟踪方法拟合控制过程的状态误差响应,实现控制器优化设计。仿真结果表明,采用该算法进行飞行器的稳定性控制,系统误差受到外界扰动的影响较小,控制器的自适应收敛性较高,展示了较好的应用性能。     

Figure of merit for multiband antennas

This communication defines a figure of merit for multiband antennas that gives an objective quantification of the similarities between radiation patterns at the different antenna operating bands.     

Integrated circuits for multiband multimode receivers

The need for different types of wireless connections to mobile terminals has increased rapidly during the last few years. The mobile terminal must be able to connect to globally existing cellular networks, as well as to different ad-hoc networks. The receivers designed for these terminals must achieve a high integration level and a high level of component sharing to meet the strict size and cost requirements. In addition, the performance of a multimode receiver must be compatible with existing single-system receivers. New process technologies, which use low supply voltages and are optimised for digital circuitry, set additional challenges for future receiver design. Several integrated receiver ICs for the multimode and multiband transceivers have been published to meet these demands. This paper gives a review of these circuit solutions and a brief introduction to the demands set by different systems and receiver architectures for the design of the multimode and multiband receiver.     

多频共面波导馈电平面开式套简天线研究

提出了一种同时支持诸多频带工作的共面波导馈电平面开式套筒天线.共面波导中心金属导带以及接地板均采用渐变的形状,天线采用开式套筒结构,并加入了一个倒L型寄生贴片,以最大程度地展宽天线带宽.与以往所提出的共面波导馈电天线相比,此天线具有尺寸小,覆盖更宽的频带,可同时支持个人通信系统(PCS),宽带码分多址系统(WCDMA)...     

多频带数字滤波器的设计和FPGA实现

本文介绍了一种应用于FPGA芯片的多频带数字滤波器的快速高效的设计、验证和实现的方法,该方法不同于传统的FPGA滤波器设计而且十分实用能大大缩短开发周期。首先根据多频带数字滤波器的性能要求,介绍了在具体性能指标下的多频带数字滤波在FPGA中实现的思想和原理,接下来描述了FPGA数字滤波器的传统设计方法和MATLAB设计方法,解释了采用极小化极大准则对滤波器的频率响应进行逼近的原理,然后结合一个具体的多频带数字滤波器的设计,给出了利用MATLAB进行多频带滤波器设计的过程以及HDL代码的生成步骤,最后介绍了该多频带滤波器在Modelsim中的RTL级仿真和在FPGA芯片中的门级实现。     

Microstrip fractal patch antenna for multiband communication

A novel square microstrip fractal patch antenna in a Sierpinski carpet is proposed for three-band operation. Measured results indicate that the return loss is better than 10 dB and that the gain is greater than 7 dB in each band. This antenna is an attractive candidate for wireless, satellite and mobile communication applications     

Triple-stacked microstrip patch antenna for multiband system

A triple-stacked microstrip patch antenna is presented for a multiband system comprising cellular phone, global positioning system and personal communication services. It consists of three microstrip patches, and there is a slot on the middle patch to couple the first patch to the third patch. The measured results are in agreement with the simulated results at the frequencies of interest.     

Miniature built-in multiband antennas for mobile handsets

In this paper, we propose a new design for built-in handset antennas in that metal strips as additional resonators are directly connected with a feed strip. With the new design scheme, a quad-band antenna for covering GSM900, DCS1800, PCS1900, and UMTS2000 bands and a five-band antenna for covering GSM900, DCS1800, PCS1900, UMTS2000, and ISM2450 bands for use in mobile built-in handsets are experimentally carried out. Compared with the parasitic form with a shorted strip placed away from the main radiator in the open literature, the size of the proposed antennas can be reduced by an order of 10/spl sim/20%, which is desirable since the size of mobile phones is becoming smaller according to consumer preferences. Moreover, the impedance matching for each band of the new antennas becomes easy. The new quad-band and five-band built-in handset antennas are developed within the limits of a 36/spl times/16/spl times/8 mm/sup 3/ volume. The antennas are also analyzed using the finite-difference time-domain technique. A good agreement is achieved between measurement and simulation.     

高集成度多波段外辐射源雷达接收机的设计与实验

针对现阶段外辐射源雷达多波段软件无线电(SDR)系统集成度低,体积大和硬件结构复杂的不足,设计了一种高集成度、多波段、小型化、低成本的外辐射源雷达SDR接收机系统。系统由高集成度的AD9361射频芯片、现场可编程门阵列(FPGA)和USB 3.0传输模块组成,目的是利用调频(FM)广播、中国移动多媒体广播(CMMB)和数字电视地面多媒体广播(DTMB)第三方机会照射源实现对目标的探测。实测数据结果表明,该系统能够对多波段信号进行正确的采集,并将数据传输到上位机。外场实验验证了该系统的可靠性以及良好的目标探测性能。     

Figure of merit for narrowband,wideband and multiband LNAs

In software defined radio, the same radio front end is used to accommodate different wireless standards operating in different frequency bands. The use of wideband or multiband low noise amplifiers (LNAs) is mandatory in such situations. There are several figures of merit (FoMs) proposed for narrowband LNAs. These FoMs are modified for wideband/multiband LNAs just by the inclusion of 3?dB bandwidth, and designers tend to use the one that favours their own design. In this article, a review of the existing FoMs for narrowband LNAs is presented. Based on this analysis, we propose two different FoMs for fair comparison of improvement in LNA parameters due to complementary metal oxide semiconductor (CMOS) technology advancement and circuit optimisation (irrespective of transistor technology), separately. The empirical technology scaling factor for gain, noise figure (NF), f _T and linearity is used to differentiate between these FoMs for different types of LNAs.     

Frequency planning and synthesizer architectures for multiband OFDM UWB radios

This work presents an analysis on frequency planning and synthesis for multiband (MB) orthogonal frequency-division multiplexing (OFDM) ultra-wideband (UWB) radios operating in the range of 3.1-10.6 GHz. The most important specifications for the frequency synthesizer in an MB-OFDM UWB transceiver are provided. A synthesizer architecture for an existing frequency plan is introduced along with a discussion on its performance and implementation. An alternative frequency plan and its corresponding synthesizer architecture are also proposed. It is shown how this modified frequency plan leads to a significant simplification in the synthesizer realization. The feasible performance of both synthesizer architectures is evaluated through macromodel simulations using realistic models for the building blocks. Finally, system-level simulation results showing the impact of synthesizer spurs on the bit error rate performance of an MB-OFDM UWB receiver in the presence of interferers are provided. The presented results and discussion provide valuable insight for the implementation of a 3.1-10.6-GHz UWB synthesizer.     

Modified T-shaped planar monopole antennas for multiband operation

In this paper, we propose a novel modified T-shaped planar monopole antenna in that two asymmetric horizontal strips are used as additional resonators to produce the lower and upper resonant modes. As a result, a dual-band antenna for covering 2.4- and 5-GHz wireless local area network (WLAN) bands is implemented. In order to expand the lower band, a multiband antenna for covering the digital communications systems, personal communications systems, Universal Mobile Telecommunications Systems, and 2.4/5-GHz WLAN bands is also developed. Prototypes of the multiband antenna have been successfully implemented. Good omnidirectional radiation in the desired frequency bands has been achieved. The proposed multiband antenna with relatively low profile is very suitable for multiband mobile communication systems.     

Self-similar prefractal frequency selective surfaces for multiband and dual-polarized applications

Frequency-selective surfaces (FSS), that have been designed using fractal iterative techniques, have been fabricated and measured. Fractals contain many scaled copies of the starting geometry, each of which acts as a scaled version of the original. A multiband FSS can be designed that uses several iterations of the geometry to form a prefractal that resonates corresponding to each of the scales present in the geometry. Minkowski and Sierpinski carpet fractals have been utilized in the design of three surfaces which exhibit two or three stopbands depending on how many iterations are used to generate the geometry of the cell. These surfaces are dual polarized due to the symmetry of the geometry. Simulation capabilities have been developed to analyze these periodic structures, including periodic method of moments (MOM) and finite-difference time-domain (FDTD) techniques which show good correlation to the measured results.     

Compact internal multiband antenna for mobile phone and WLAN standards

A novel internal planar inverted-F antenna (PIFA) suitable for handset terminals is presented. The structure combines shorted parasitic patches, capacitive loads and slots to achieve multiband operation. This compact antenna operates in the GSM, DCS, PCS, UMTS, HIPERLAN/2 and IEEE 802.11a bands within 2.5:1 voltage standing wave ratio (VSWR) and with good efficiency.     

谈字幕机数据安全及有效运行的保障措施

字幕机是电视节目制作中的重要环节,本文结合实际,从软件和硬件两方面,讨论了保障字幕机有效运行及数据安全的多种措施。     

Improving pitch estimation for efficient multiband excitationcoding of speech

The authors describe an improved pitch detection algorithm for efficient multiband excitation (MBE) coding of speech. The improved algorithm adds a corrective measure to the error measure for spectrum matching employed in conventional MBE pitch analysis. This corrective measure effectively applies equal weighting to all harmonic bands by normalising the error energy in each band. The result is the reduction of gross pitch errors owing to pitch doublings. An additional advantage of using this corrective measure is that, because this measure is based on a sum-of-product formula, comparisons of matching scores may be performed with partial-sums computed during the evaluation of the measure, therefore, facilitating fast searching of the optimum pitch period. Simulation results show that, with the deployment of the improved algorithm, pitch tracking procedure is no longer needed, and the coding delay of the MBE coder is significantly reduced     

Single and double layer planar multiband PIFAs

A compact multiband planar inverted-F antenna (PIFA) suitable for distributed radio-over-fiber repeater networks is modified into a planar structure. It is shown that the planar antenna performance is not degraded with respect to the original PIFA and further, a two layer design is demonstrated to offer improved feed matching. The European bands for GSM, DCS-1800, DECT, UMTS, Bluetooth and HiperLAN2 are all covered. A model of the antenna is introduced as a first stage to developing an equivalent circuit.