Switching rates of dual selection diversity and dual switch-and-stay diversity

The switching rates of dual selection combining diversity and dual switch-and-stay combining diversity in Rayleigh, Rician and Nakagami-m (m half-integer or integer) fading are derived. Closed-form or single integral expressions are obtained for both the cases of balanced channels and unbalanced channels.     

Low-profile dual band, dual polarised array antenna module

The design of a microstrip patch antenna module intended for use in the SHF military satcom band as a building-block for a variety of two dimensional array antennas is described. The module can operate in duplex mode in dual orthogonal circularly polarised transmit/receive bands.<>     

一种双频双模射频电路的设计

给出了一种基于802．11b／g下的双模电路设计，该电路能很好地应用于2．4GHz和5.8GHz两个工作频段，并能实现全向和定向两种工作模式的转换。仿真结果表明，该电路有良好的回波损耗和传输特性，可以较好地满足无线局域网中的应用。     

新型光湿敏元件及应用

介绍了利用硅作衬底的陶瓷钛酸镧锶（SrLaTiO3)材料的半导体元件，独特的MIS结构元件，既具有光的特性，又可以测量湿度信号。利用光、湿敏特性元件设计成光、湿敏传感器。     

红外双波段/双视场导引头的光学设计

现有对地捷联导引头多数采用红外单波段和单视场相结合的方式对目标进行匹配和截获,然而该种方式在日益复杂的战场环境下易受目标/背景特性复杂程度、探测器性能、视场大小限制等因素的影响。在保留了某型捷联导引头原有单一的中波红外大视场的基础上,加入了长波红外大小两个视场,提出了一种新型的红外双波段/双视场导引头。通过利用中长波双波段的图像融合和长波红外下的双视场切换,突出目标与背景特征信息差异,可以有效提高导弹对目标的截获概率。采用CODE V软件设计了光学系统。整个系统采用共孔径式光学设计,具有较好的成像质量,满足系统要求。     

OTA-based dual input integrator

A new type of dual input integrator (ODI) realized with two operational transconductance amplifiers (OTAs) is proposed. A compensation of non-ideally matched characteristics of OTAs, based on dividing the integration period into two subintervals, is achieved. Very high linearity and increased frequency and dynamic range are obtained. The ODI is suitable for measurement of very small time differences between two square-wave input signals.     

Property of dual points

Starting from a basic theorem in threshold logic, a condition which must be satisfied by the on set and the off set of a threshold function is found. A property follows which neural networks must possess to be able to realise a reverberation of maximum length.     

Symmetric wavelets dyadic sibling and dual frames

We introduce a family of symmetric dyadic wavelets arising from dual and sibling frames. Each of the frames consists of three generators obtained using spectral factorization. We describe two cases of dual frames: symmetric frames with redundant highpass filters and symmetric frames with redundant bandpass filters. We present design methods and examples for both types of dual frames. We additionally consider the design of symmetric frames where the analysis and synthesis filterbanks have the same lowpass filter, leading to sibling frames. In the proposed sibling frames the non-redundant filters are identical in the synthesis and analysis filterbanks. Only the redundant filters are different, thus obtaining a dual frame approximating tight frames. The filters are simple to construct, and offer smooth scaling functions and wavelets, as well as dense time-scale grid. Examples of sibling frames are discussed. The filters are all FIR of even and odd lengths, linear phase, and possess at least one vanishing moment each. A denoising application compares the proposed wavelets with published frames.     

A dual watermark-fingerprint system

This article proposes a multimedia content protection system in which all copies of a protected object are identically watermarked, but each user has a distinct secret detection key that differs from the secret embedding key. An attacker with access to one detection key can fool the corresponding watermark detector but not other watermark detectors. Surprisingly, analogous to a criminal action, during this attack the attacker necessarily inserts his or her fingerprint into the modified content. Even a collusion clique of relatively large size cannot entirely remove the secret marks from the protected content by colluding their detection keys. More importantly, if the clique is not large enough, traces of the detection keys of all colluders can be detected with relatively high accuracy in the attacked clip. Our proposed watermark-fingerprint system achieves a minimum collusion size K that grows linearly with the size N of the marked object. In addition, we can augment our watermark-fingerprint system with a segmentation layer. The media content is partitioned into 5 segments, in which media players as well as forensic analyzers can reliably detect a watermark or fingerprint. Only detection keys that belong to the same segment can participate in the collusion clique. With segmentation, the minimum collusion size K grows as 0(N log N). Therefore, with or without segmentation, our watermark-fingerprint system significantly improves on the best-known asymptotic resistance to (fingerprint) collusion attacks of about O(N/sup 1/4/). Because we use a new protection protocol, comparing our system to classic fingerprint systems might seem unfair. However, such a comparison is important because the two technologies share a common goal: multimedia copyright enforcement. Our aim in this article is to characterize the collusion attacks against this system under the assumption that watermark detection is robust against signal-processing attacks on the protected object.     

Small dual patch antenna

A novel two-layer rectangular patch antenna has been designed and tested. Compared with a basic single layer patch antenna with the same projection area, the resonant frequency is reduced by 39%. The bandwidth is 5%; the cross-polarization level is less than -15 dB     

GaInAsP dual wavelength laser

The fabrication and performance characteristics of a dual wavelength laser emitting near 1.3 μm and 1.55 μm are described. The lasers are of the etched mesa buried heterostructure type, and utilise semi-insulating InP layers both the lateral optical confinement and current confinement. The 1.55 μm emission is at a single wavelength by virtue of the frequency selective feedback provided by a grating etched on the substrate. The lasers have threshold currents in the 20 to 40 mA range, and have quantum efficiencies comparable to single emitter lasers     

Bifocal dual reflector antenna

A bifocal dual reflector antenna is similar to and has better scan capability than a classical Cassegrain reflector antenna. The method used in determining the reflector surfaces is a modification of a design method for the dielectric bifocal lens. Computed radiation characteristics of the bifocal reflector system are compared with those of a classical Cassegrain reflector system. The results confirm that the bifocal reflector has superior scanning performance.     

宽带、双极化四脊喇叭馈源研究

研制了一种用于抛物面天线馈源的高性能宽带、双极化四脊喇叭天线.利用三维全波电磁场仿真(Computer Simulation Technology,CST)软件分析了喇叭天线中后腔的形状和结构参数以及馈电探针位置对天线驻波比的影响,同时对天线的整体结构参数进行了优化,并对其进行加工测试.模拟和实验测试结果表明：采用渐变后腔,并取合适的结构参数和馈电探针位置,馈源天线能得到最佳驻波比,在4～12 GHz的工作频带范围内小于2、-12 dB的边缘照射角大于90°,馈源的其它电性能参数符合设计要求.     

Buried active and passive components

The coming generations of portable products require significant improvement of packaging technologies, mainly due to increasing signal frequencies and the demand for higher density of functions. State of the art are organic substrates with high-density build-up layers and micro-vias, equipped on both sides with discrete passive and active components. The space requirement of active chips can be already reduced to a minimum by implementing CSPs (chip size packages) or flip chips. A further miniaturization however requires a 3-dimensional integration of components. Besides miniaturization the new applications require signal frequencies of several GHz. In order to maintain signal integrity, much shorter and impedance-matched interconnects between chips and other components are required. Here a new approach will be described which allows extreme dense 3-dimensional integration and very short interconnects combined with the generation of integrated resistors. This approach, called ?Chip in Polymer“ is based on the integration of extremely thin components into build-up layers of printed circuit boards.     

Millimetric V-groove guide and components

A characteristic equation of single V-groove guide has been derived using the transverse resonance technique. This equation is much less complex and tedious to solve when compared with that obtained by the conformal mapping technique. The computed results are within 1% of the published experimental values for the cut-off wavelengths at X-band and 100 GHz. The present analytical approach is to approximate the central groove region by a large number of rectangular steps and the previously derived analytical solution for the rectangular-groove guide are applied to predict the propagation characteristics of single V-groove guide. A number of components in V-groove guide which have very similar characteristics to those of the rectangular-groove counter-part have been reviewed. It is noted that both the E-plane and H-plane cylindrical bends in both rectangular-groove and V-groove guides had unacceptably high-loss and a satisfactory solution have yet to be reached.     

纳米电子器件与纳米电子技术

介绍了纳米电子器件与纳米电子技术的概念以及纳米电子器件的分类;综述了现有的光刻、外延、SPM、特种精细加工等相关的纳米电子器件制备与加工技术;阐述了纳米电子技术中急需解决的若干关键问题。     

The effects of channel-estimation errors on a space-time spreading CDMA system with dual transmit and dual receive diversity

The uplink of a space-time spreading code-division multiple-access system with dual transmit and dual receive antennas is analyzed with the effect of imperfect channel estimation. With the help of pilot signals, the Rayleigh multipath fading channel experienced by the transmitted signal is estimated by simple correlators, and subsequently used to coherently combine the multipath signals in a RAKE-like space-time combiner. As a system becomes more wideband, more multipaths are resolved, and the energy in each path is reduced. This reduction in signal strength causes increased estimation error and impacts the system performance. Through the derivation of the probability of error in a space-time spreading system with channel-estimation errors, this paper studies the tradeoff between diversity and estimation errors. It is shown that an optimal bandwidth exists and the optimal power allocation for the pilot signals is a function of the quality of the channel estimates.     

On relations between covering radius and dual distance

The covering radius of a code tells us how far in the sense of Hamming distance an arbitrary word of the ambient space can be from the code. For a few decades this parameter has been widely studied. We estimate the covering ratios of a code when the dual distance is known. We derive a new bound on covering radii of linear codes. It improves essentially on the previously known estimates in a certain wide range. We also study asymptotic bounds on the cardinality of constant weight codes