Sigma-delta modulation with i.i.d. Gaussian inputs

The response of a single-loop sigma-delta modulator to an independent identically distributed (i.i.d.) Gaussian input signal is analyzed. A continuous-time stochastic model is developed and the connection of the model to the system is described. A condition is given so that the difference between the behavior of the model and that of the true system can be made arbitrarily small. Theories from renewal and Wiener processes are applied to show the convergence and mixing properties of the output sequence. Also derived is the power spectrum of the quantization noise. Compared to the spectrum when the input is DC, the i.i.d. Gaussian random process smears the discrete spectrum into band structures     

千兆以太网中8B/10B线路码的功率谱分析

该文根据有限状态机模型,采用Cariolaro算法(1983)即状态转移矩阵求解法分析了千兆以太网中8B/10B线路码的功率谱,给出了P=0.5时的闭合解析式及功率谱曲线。     

HP8566B频谱分析仪显示故障维修

详细描述了HP8566B显示故障的维修过程，通过维修实践熟悉了一般电子分析仪器显示器的工作机理。对出现的故障现象分析其产生原因，总结了维修方法，用国产元器件进行了更换，最终解决了问题。     

B3G系统的频谱需求分析

B3G网络具有更高的复杂性和业务多样性,对频谱需求分析方法提出了更高的要求,ITU-RWP8F工作组正在开展对B3G的频谱需求分析.本文介绍了B3G频谱需求分析的通用流程,详细说明了其中的系统容量算法;并对频谱需求分析所需的电路交换业务资源占用度量方法进行了研究.     

Performance of personal access communications system-unlicensed B

The FCC has allocated the band between 1920 MHz and 1930 MHz for unlicensed personal communications services (UPCS) using isochronous or circuit operation. The UPCS spectrum is between the licensed PCS spectrum bands of 1850-1910 MHz and 1930-1990 MHz. Terminal interoperability in both the UPCS spectrum on private indoor wireless systems and the licensed spectrum on public PCS systems is desirable and encouraged by the FCC. This paper presents a port channel assignment process for the personal access communications system-unlicensed B (PACS-UB) which abides by the FCC etiquette for UPCS and discusses the corresponding uplink and downlink performance. Uplink power control is employed to improve the uplink performance. PACS-UB has a high degree of commonality with licensed PACS to permit economical licensed/unlicensed terminals and common network services. The results of our simulation show that, at 1% to 2% blocking probability, 99% of downlink local-mean signal-to-noise plus interference ratio (SINR) values are above 17 dB for a 10 to 20 m port separation. For a three-dimensional office environment, the uplink limits the SINR performance, however, with uplink power control, a 5.5 to 7 dB improvement in the uplink SINR can be achieved even for high traffic load     

Comments, with reply, on `Modeling of the 1/f noiseovershoot in short-channel MOSFETs locally degraded by hot-carrierinjection' by B. Boukriss et al

It is pointed out that a letter by Boukriss et al. (see ibid., vol.10, p.433-6, 1989) contains no reference to the actual value of the characteristic exponent of the noise spectrum (γ). This omission may result from the assumption that γ is equal to one. Similar measurements by the present author indicate that γ varies strongly following hot-carrier injection near the drain. The change in the characteristic component is caused by the injected carriers present in the oxide near the interface, rather than the increased number of traps. This injected charge has an effect on noise provided the channel is not pinched off. It is argued that to study only the amplitude of the noise and not γ misses critical information, the scaling properties, and that if one is to measure noise amplitude, one should measure the characteristic exponent as well. In a reply, the original authors state that the 1/f noise was studied for a nonhomogeneous MOSFET. The 1/f noise level was investigated from weak to strong inversion     

固态面粉中维生素B6的荧光法直接测定

利用荧光光谱法对固体粉末面粉中痕量维生素B<,6>(VB<,6>)含量进行了研究.通过测量添加有VB<,6>的硫酸钡固体粉末样品,得到峰值波长为405 nm的荧光光谱图,其荧光强度与VB<,6>含量呈线性关系,相关系数R=0.9976.采用上述方法对面粉样品进行测量,得到峰值波长为390 nm的荧光光谱图,其荧光强度与...     

Spectrum analysis with a c.c.d. delay line

A novel form of c.c.d. spectrum analyser is described which functions by performing the discrete Fourier transform. The approach is based on the coherent-memory-filter principle and is well suited to Doppler processing. Results are given for a 10 kHz analyser with 200 Hz resolution.     

Cognitive Wireless Communication Networks (Hossian, E. and Bhargava, V.; 2007) [Book Review]

?Cognitive radio? is emerging as a promising technology to cope with the spectrum scarcity as well as the spectrum underutilization problem in the next generation wireless communications systems. This book, Cognitive Wireless Communication Networks, edited by Ekram Hossain and Vijay Bhargava, puts together a rich set of research articles featuring recent advances in theory, design, and analysis of cognitive wireless communication networks. The book consists of 15 invited articles from distinguished researchers in this area, which cover a wide range of topics related to the cognitive radio technology. In particular, the topics covered in this book include fundamental challenges and issues in designing cognitive radio systems, information-theoretic analysis of cognitive radio systems, spectrum sensing and co-existence issues, adaptive physical layer protocols and link adaptation techniques for cognitive radio, orthogonal frequency division multiple access (OFDM) and ultra wide band (UWB)- based cognitive radio, different techniques for spectrum access by distributed cognitive radio, cognitive medium access control (MAC) protocols, decentralized learning-based dynamic spectrum access methods, and microeconomic models for spectrum management in cognitive radio.     

联合循环平稳特征PCA与RVM的频谱感知

针对无线信道环境中低信噪比情况下主用户信号检测率较低的问题,提出了一种基于循环平稳特征主成分分析(PCA)与相关向量机(RVM)的认知网络频谱感知算法。该算法结合了主成分分析算法与相关向量机分类方法,应用于解决认知网络频谱感知问题。首先对信号循环平稳特征参数进行特征提取,通过主成分分析进行降维提取信号主成分,生成训练样本和待测样本,并完成对相关向量机的训练,再采用训练完成的相关向量机算法分别对有无主用户情况下的信号进行分类检测,最后获得主用户信号存在性的感知判断。仿真实验表明,与人工神经网络、支持向量机和最大最小特征值算法相比较,所提算法在低信噪比情况下具有较高的分类检测性能,检测率最大可提高61.6%,有效地实现了对主用户信号的感知。     

Effects of 2.6-4.0 GHz microwave radiation on E-coli B.

The effects of 2.6-4.0 GHz microwave radiation on living E. coli B bacteria were studied using measurement of the colony forming ability (CFA) of the cells and alterations in the molecular structure determined by comparing the infrared spectrum of irradiated and unirradiated cell cultures. At absorbed power levels of 20 mW in 1 ml of cellular suspensions (i.e., a specific absorption rate of 20 W/kg) for 10-12 hour exposures, no effects were observed on either the molecular structure or the CFA for this particular strain of E. coli.     

Large-time-bandwidth-product correlation and holographic storage with an s.a.w. storage correlator

High-resolution (375 Hz) spectrum analysis has been performed by correlating long signals during the read-in process. In a ZnO-on-Si storage correlator a new holographic storage technique is demonstrated to achieve chirp compression with large compression ratio (?8000) and improved dynamic range.     

Studies of backscattered sea return with a CW, dual-frequency, X-band radar

A coherent, CW, dual-frequency,X-band radar was used to study microwave sea return from the Chesapeake Bay. It is shown that the product of the backscattered fields depends strongly on long surface wave properties. In particular, a sharp line is found in the product power spectrum whose frequency is that of the water wave whose wavelength is in resonance with the spatial period of the beat frequency between the two transmitted signals and whose wave vector is parallel to the horizontal line of sight. Thus, gravity wave dispersion relations can be obtained with the system. Furthermore, the degree of modulation of short waves by long ones is given by the intensity of the line. A broad background corresponding to the convolution of the single-frequency Doppler spectra is also seen in the product power spectrum. These results are shown to be interpretable by composite surface scattering theory.     

Market Driven Dynamic Spectrum Allocation over Space and Time among Radio-Access Networks: DVB-T and B3G CDMA with Heterogeneous Terminals

The radio frequency spectrum is a naturally limited resource of extraordinary value, as the key to the provision of important communication and information services. Traditionally, spectrum has been allocated first to specific access technologies, and then sub-allocated to specific access networks, on very long term basis (up to decades). The traditional scheme can be very inefficient when demand patterns (“loads”) exhibit high temporal and spatial variations. Dynamic spectrum allocation (DSA) improves radio spectrum efficiency by adjusting the allocation as demand changes in time and/or space. In previous work, we introduced a DSA scheme in which a spectrum manager periodically auctions short-term spectrum licenses. The scheme can be supported by a realistic “pooling” business model, and can work with many radio-access technologies. But our previous analysis only considers a code-division multiple access (CDMA) technology; and DSA provides the greatest benefits with the participation of networks having complementary “busy hours,” such as video entertainment services and cellular telephony. Here, a digital video broadcast (DVB) terrestrial network joins the scheme. A typical DVB terrestrial cell is (much) larger than a UMTS cell. This brings to the forefront inter-cell interference, and inter-related auctions in different cells. To capture the essence of these issues we focus first on a situation where one DVB terrestrial cell overlays two adjacent CDMA cells. Subsequently we discuss extensions to richer scenarios. The contributions of the present work over our previous publications include to : (i) address the impact of inter-cell interference among several CDMA cells, (ii) introduce the DVB access technology into the DSA scheme, (iii) modify the auction scheme to consider that a DVB cell overlays several CDMA cells, (iv) characterise analytically the marketing and bidding behaviour of the DVB network.

B.J.T. frequency doubling with sinusoidal output

A frequency-doubling technique is described that can provide a low-distortion sinusoidal output. The circuit consists only of bipolar-junction-transistor (b.j.t.) arrays, and is hence readily fabricated by s.i.c. technology. Results are given, and the criteria for a low-distortion output discussed.     

Routing,modulation level and spectrum allocation with dynamic modulation level conversion in elastic optical networks

Elastic optical network is introduced as a promising technology to provide multi-bitrate-friendly data transmission in the optical layer. Elastic optical networks are based on flexible modulation format conversion, which can make more efficient use of spectrum resources than current fix-grid WDM networks. In this paper, we define the routing, modulation level and spectrum resource allocation (RMLSA) problem and then propose two novel dynamic modulation level conversion (MLC) enabled RMLSA algorithms. Numerical simulations are conducted to compare the performance of the path modulation level conversion (Path-MLC) and link modulation level conversion (Link-MLC) with different MLC thresholds with K-shortest paths RSA in terms of blocking rate, occupied spectrum and the number of MLCs across two topologies. The results verify that the Link-MLC with unlimited MLC achieves the lowest blocking rate and moderate spectrum utilization at the expense of intermediate node modulation conversions in two topologies. Smaller MLC threshold has higher blocking rate and occupied less spectrum resource. The results also suggest that the Path-MLC approach is more resource efficient than the Link-MLC with relatively higher blocking rate, and this method maybe more preferable in the networks with tight budget and/or energy constraints.     

美军战场频谱管理现状与发展

在现代战争中,电磁频谱管理是实现电磁协同的保证,是取得战争胜利的保证。阐述了战场频谱管理的基本概念,重点介绍了战场频谱管理的典型流程以及美军典型的战场频谱管理系统,然后分析了战场频谱管理未来的技术发展趋势,期望为后续研究提供一定的参考。     

Statistically instable processes: Connection with flicker,nonequilibrium, fractal and colored noise

Analytical expressions that link statistical instability parameters with process’s spectrum are obtained. It is shown that statistical stability is determined solely by the character of spectral power density dependence on frequency. It is revealed that statistically stable noises are those with rising intensity when frequency is increased, white noise, and equilibrium flicker noise described by the dependence 1/f ^β where the spectrum shape parameter is 0 < β < 1 as well as fractal Gaussian noise. Statistically instable noises are nonequilibrium flicker noises with spectral power density 1/f ^β when β≥1. It is determined that not only random nonstationary and deterministic processes are statistically instable as it was considered earlier, but stationary processes as well.     

Comments, with reply, on 'Cumulants: a powerful tool in signal processing' by G.B. Giannakis

A counterexample is presented to show that the solution to the stochastic realization problem given in the above-titled letter (ibid., vol.75, no.9, p.1333-4, Sept. 1987) does not apply, in general, to the infinite impulse response systems. The author expands on the comments.<>