A simple dual-band microstrip-fed printed antenna for WLAN applications

A novel microstrip-fed dual-band printed antenna for wireless local area network (WLAN) is presented. The antenna comprises a rectangular and a circular radiating element, which generate two resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. The design was experimentally verified by constructing the antenna on a FR4 (ϵr = 4.4) dielectric substrate (47 mm x 26 mm x 0.76 mm) and measuring its impedance and radiation characteristics at both the bands. The measured 10 dB return loss (VSWR 2:1) bandwidth in the 2.4G Hz band is 550 MHz (2.1?2.65 GHz) and it covers the bandwidth required for 2.4 GHz WLAN. The 5.2/5.8 GHz resonant mode has a bandwidth of 950 MHz (5.15?6.1 GHz) covering 5.2/5.8 GHz WLAN bands. A rigorous experimental evaluation confirmed that the dual-band printed antenna maintained good radiation characteristics with minimum cross-polarisation levels.     

Calibration of smart antenna systems: measurements and results

Smart antennas (SAs) are viewed as a candidate enabling technology for modern wireless communication systems to increase network capacity and facilitate location-based services. By conducting measurements on an SA test-bed, the signal distortion introduced by the implementation of a practical system can be analysed. This distortion can have significant impact on the estimation of signal wavefronts. Measurements have been conducted at the system, sub-system and component levels, using an SA developed for this purpose and employing a uniform circular array. This has enabled the error introduced by an implemented system to be examined. Calibration procedures are developed to overcome these implementation limitations. The cause and effects of these errors are examined, and system manufacturing tolerances and temporal thermal effects on the analogue sub-systems are shown to be the major contributor to this error; these results are presented and analysed     

Dual-band frequency selective surface for improving the transmission of Bluetooth and WLAN signals through an energy-saving glass

A dual-band frequency selective surface (FSS) consisting of one larger and four smaller regular Jerusalem-cross slots was designed to improve the transmission effect of signals through an energy-saving glass at 2.45 and 5.8 GHz for Bluetooth and wireless local area network applications, respectively. Reflections from the energy-saving glass sculptured with the dual-band FSS are improved by a factor of 10 and 3 dB at 2.45 and 5.8 GHz, respectively, while the transmissions of the energy-saving glass sculptured with the dual-band FSS are improved by a factor of 50 and 40 dB at 2.45 and 5.8 GHz, respectively. The ratio of area occupied by the dual-band FSS to area of the energy-saving glass is 35.6%, which may degrade thermal isolation capability but can greatly improve communication quality for wireless communications.     

基于ZigBee网络的TD-SCDMA智能天线信号强度测量系统

由于智能天线的波束成形技术,传统测量电磁辐射的方法已不适用于TD-SCDMA智能天线。该文设计一种TD-SCDMA智能天线的信号强度测量系统,根据智能天线的特点,应用ZigBee网络同时获取多个测量点的信号强度值。另外,还提供一种测量点的布设方案,并使用该方案进行实际测量。实际测量结果显示:设计的测量系统的测量精度高于传统的测量方法,进而可以更准确地进行电磁环境的测评,具有较强的实用价值。     

一种新型的OFDM智能天线

根据自适应天线阵列理论，结合给定的参考波束的误差，引入虚拟干扰的概念，对目标波束图形状进行调整，提出一种新的可以应用于任意类型天线阵列的波束综舍算法．应用提出的新算法，在主辩和旁瓣位置都可以对波束进行有效的调节．最终获得阵列的最优权矢量，能够最小化目标波束图与参考波束图间的差异．理论分析与仿真结果表明，与现有的同类算法相比，该算法能更有效地获得与参考波束基本相符的波束．应用于OFDM智能天线系统时，对不同子载波频率上信号进行单独处理，利用该算法进行波束综合，能够在整个有效频段，使所有子载波上获得基本一致的阵列输出．     

用于直升机舱内降噪的智能周期撑杆研究

直升机主减速器内的齿轮啮合引起的中高频振动是直升机舱内噪声的主要来源之一,通过设计具有隔振性能的减速器撑杆可以有效抑制传递到机体的振动,进而减小齿轮啮合诱发的舱内噪声。基于压电叠堆/橡胶周期结构,提出了一种适用于直升机舱内降噪的主动/被动混合振动控制的智能周期撑杆,在满足强度与刚度要求的同时,具有优良的多频与宽频减振能力。压电叠堆与橡胶材料周期排列组成周期结构,其在特定频率范围内具有“机械滤波”特性;同时,通过调节驱动压电叠堆的电压与电流,改变压电叠堆的动刚度,可实现主动减振的功能。为了对智能周期撑杆的主动/被动混合振动控制性能进行分析,建立了基于传递矩阵形式的智能周期撑杆的机电耦合动力学模型,并使用多物理场仿真软件验证了模型的正确性。进一步基于该模型分析了在驱动电压与电流有限的条件下的智能周期撑杆的最优隔振性能：在智能周期撑杆一端固支、一端受到 10 N 的激振力时,最大驱动电压为 20 V、最大驱动电流为 1 A 的电学边界限制下,该智能周期撑杆具有将 692 Hz以上的振动完全衰减的能力,对 692 Hz以下的振动有一定程度的控制效果。此外,还研究了材料参数与力学边界条件对主动控制的影响,即橡胶材料的阻尼、激振力对进行主动控制时需要的驱动电压与电流的影响。使用有限元模型校核了智能周期撑杆的强度与刚度,验证了所提出的智能周期撑杆方案的工程可行性。使用压电叠堆作动器与聚酯乙烯杆件组成一个三周期的压电叠堆周期撑杆作为智能周期撑杆的简化模型,验证了主动/被动混合振动控制性能,分析了力学边界条件对隔振性能的影响,以及进行主动控制时的驱动电压和电流与最优驱动电压和电流的关系。     

Coverage probability analysis of IEEE 802.16 system with smart antenna system over stanford university interim fading channels

The IEEE 802.16 system, a promising wireless communication system, has a maximum transmission range of 50 km according to the IEEE 802.16 standard. In reality, the transmission range and coverage probability of an IEEE 802.16 system vary for different wireless scenarios. Evaluating the transmission range and coverage probability of an IEEE 802.16 system prior to implementation is important. Hence, the Stanford University Interim (SUI) channel model in IEEE 802.16 specifications is suitable for evaluating the performance of IEEE 802.16 systems. To generate an effective method for predicting coverage, this study uses the SUI channel model to analyse the coverage probability of an IEEE 802.16 system. Furthermore, this study utilises a smart antenna system (SAS) to enhance IEEE 802.16 system performance. In terms of different antenna heights of the Base Transceiver Station and Customer Premises Equipment, the performance evaluation results show that the cell radius with the SAS is at least 30% more than that without the SAS.     

Eigenspace-based blind pattern optimisations of steerable antenna array for interference cancellation

A novel adaptive algorithm for an array using directional elements called a hybrid smart antenna system is proposed. The algorithm controls the element patterns on the basis of an objective function composed of eigenvalues of a covariance matrix. A high and stable array output signal-to-interference-plus-noise ratio is achieved by improving both the received powers and the spatial correlation coefficient between incident waves, without prior knowledge such as directions-of-arrival, channel state information or training signals. The characteristics of the proposed algorithm are theoretically and numerically clarified for a simple case involving two incident waves. Convergence with least mean squares algorithm is found to be as fast as that with recursive least squares algorithm in this system. Also, simulation for statistical performance evaluation is carried out in comparison with a conventional system. Furthermore, a method to implement the proposed eigenspace control algorithm without having to solve the eigenvalue problem is shown.     

Size reduction and bandwidth enhancement of snowflake fractal antenna

A new small-size and wideband fractal antenna in the shape of a snowflake is proposed. Various iterations of this fractal antenna with probe feed and capacitively coupled feed are compared and an optimised design is presented. It is shown that, with an air-filled substrate and capacitive feed, an impedance bandwidth >49% and, with a slot-loading technique, a reduction of about 70% in patch surface size compared with an ordinary wideband Koch fractal antenna are achievable. The simulation via a finite-element programme, and measured results on the return loss and the E and H-plane radiation patterns of the proposed antennas are presented and shown to be in good agreement.     

Studying electromagnetic interference spectrum in antenna under aircraft radome using models with artificial charged aerosol clouds

The spectrum of electromagnetic interference that is induced by discharges in an antenna arranged under an aircraft radome in an artificial charged aqueous aerosol cloud has been experimentally studied. It is established that, among different possible variants of lightning-arrest radomes, the minimum level of the spectral density of interference signals in the antenna is provided by vertical stripe electrodes on the radome surface. The maximum characteristic frequencies of signals in a model spherical antenna are several times lower than those in model lightning diverters, while the flat model antennas of disk or rectangular shapes exhibit the opposite trend. It has been suggested that a significant role in determining the characteristics of the electromagnetic interference spectrum in weather radar antennas is played by currents of discharges generated by charges accumulated on the dielectric radome surface.     

非接触式 IC卡天线的 CMOS集成化设计

用CMOS工艺实现了非接触式IC卡天线的集成化所需要考虑的多个方面,建立了集成天线的模型,导出了合理的设计方案,并通过实验验证了模型和设计方案。实验结果表明,采用片上天线完全可以提供非接触式IC卡工作所需要的能量。在频率为22.5MHz、感应强度为6Gs的磁场中,面积为2mm×2mm的集成天线可以为10kΩ的负载提供1.225mW的能量。     

A two-channel circuit for protecting a resonant gravitational antenna from correlated non-Gaussian interference

A modernized circuit with a noninertial nonlinear element, a whitening filter and a matched filter, connected in series-parallel, for suppressing correlated non-Gaussian interference at the output of a cryogenic resonant gravitational antenna is considered. The algorithm is based on the use of optimum processing of vector signals. __________ Translated from Metrologiya, No. 5, pp. 3–9, May, 2008.     

Peculiarities of the response of a laser interference gravitational antenna to low-frequency disturbances

Translated from Izmeritel'naya Tekhnika, No. 10, pp. 26–28, October, 1990.     

Single antenna interference cancellation for synchronised GSM networks using a widely linear receiver

A novel cochannel single antenna interference cancellation (SAIC) receiver is proposed for synchronised Group Special Mobile (GSM) systems. The receiver uses a two-stage strategy, where in the first stage cochannel interference is cancelled by a widely linear filter, while inter-symbol interference due to the GSM frequency-selective Rayleigh-fading environment is removed by a second-stage equaliser. Analytical results for the optimal widely linear filter coefficients are derived. Simulation results show excellent performance with large gains over the conventional receiver under interference limited channel conditions. It is shown that the conventional maximum likelihood sequence estimator or maximum a posteriori probability receiver is optimal when cochannel interference it not the dominant impairment, and it is proposed that the SAIC algorithm is disabled when the estimated carrier-to-interference (C/I) ratio is above a certain threshold     

Design of fractal patch antenna for size and radar cross-section reduction

This research study presents a novel design of star-shaped fractal patch antenna for miniaturisation and backscattering radar cross-section (RCS) reduction. The proposed fractal antenna gives 50% size reduction compared with a conventional circular microstrip patch (CCMP) antenna. The antenna is studied experimentally for return loss behaviour using vector network analyser R&S ZVA40. It can be useful for wireless application in 0.85-4 GHz frequency band. Further, the study focuses on backscattering RCS (both monostatic and bistatic) reduction by the proposed antenna compared with the CCMP antenna. It is found that increase in number of fractal iterations included in the conventional patch to design fractal antenna geometry reduces backscattering RCS at multiband compared to the conventional patch antenna. This reduction in backscattering RCS by the antenna is observed at multiband. The antenna can be tuned for low backscattering by variation in the substrate dielectric constant and thickness and the superstrate dielectric constant and thickness. For maximum RCS reduction by the antenna, optimisation of substrate thickness becomes necessary. The study also deals with effect of frequency and aspect angle variation on backscattering RCS reduction.     

基于符号调整的OFDM系统载波间干扰抑制方法

基于组合优化理论,提出了一种通过调整子载波调制符号的正负来抑制正交频分复用(OFDM)系统载波间干扰(ICI)的方法.首先推导出了加性高斯白噪声(AWGN)信道下的最优符号选择算法,并给出了降低其复杂度的简化算法;然后给出了二进制相移键控(BPSK)调制下减少算法码率损失的改进算法,而且在频率选择性衰落信道下对以上算法进行了推广.仿真结果证实,提出方法的误码率低于基于选择映射的载波间干扰抑制方法.     

Normalized differential detection by use of smart pixels with smart illumination

Smart pixels permit rapid signal processing through the use of integrated photodetectors and processing electronics on a single semiconductor chip. Smart pixels with smart illumination can increase the dynamic range and functionality of smart pixels by employing optoelectronic feedback to control the illumination of a scene. This combination of smart pixels and optoelectronic feedback leads to many potential sensor applications, including normalized differential detection, which is modeled and demonstrated here.     

Frequency-selective surfaces for GPS and DCS1800 mobile communication. 2. Integration with antenna for scattering reduction

The paper describes a novel attempt to integrate a quad-layer frequency selective surface (FSS) with a circularly polarised Maltese-cross antenna for the global positioning system and DCS 1800 mobile communications. The effect of integrating the FSS with the antenna is presented for both in-band (1.5-1.9 GHz) and out-of-band (8.5-9.7 GHz) operation. For out-of-band operation, a reduction of antenna scattering is observed with the integration of the FSS. A comparison of the total scattering of the antenna with that calculated for the finite ground plate is included. The seemingly contradictory two-fold impact of the FSS performance on the link budget equation is illustrated     

双基地声纳矢量传感器直达波抑制技术

针对双基地声纳系统应用中存在直达声波干扰的问题,提出了矢量双基地声纳的概念。将矢量传感器的自然指向性以及指向性锐化思想引入双基地声纳系统。以单矢量传感器作为双基地声纳接收基地,利用电子波束旋转扫描技术,将指向性零点对准发射基地,完成了声源强干扰屏蔽下的目标探测。水池试验与湖上试验结果表明,单矢量传感器配合自体姿态信息,可完成对强声源干扰的抑制。此研究工作为矢量双基地声纳系统设计奠定了理论与试验基础。     

Chemical segregation and reduction of Raman background interference using drop coating deposition

A new application of the recently described drop coating deposition Raman (DCDR) method facilitates the segregation and independent spectral characterization of mixture components. The quality of the normal (un-enhanced) Raman spectra are significantly improved as a result of reduced spectral interference from fluorescent impurities and buffer compounds. Fluorescence of commercial amino acid (O-phospho-L-serine) and protein (myoglobin) samples is reduced by over an order of magnitude using DCDR, more effectively than prolonged photo-bleaching. Furthermore, DCDR is used to obtain high-quality Raman spectra of proteins, lysozyme, and insulin, derived from solutions with up to 1000-fold excess buffer concentration. Possible thermodynamic and kinetic contributions to the observed segregation phenomena are discussed.