Low Insertion-Loss, Sharp-Rejection and Compact Microstrip Low-Pass Filters

Complementary split ring resonators are used to design compact, low insertion loss (IL), low pass filter with sharp cut-off. A prototype filter implementing area is 0.23 lambda_gtimes0.09lambda _g, lambda_g being the guided wavelength at 3-dB cut-off frequency (f_c) 1.887GHz. Maximum IL is within 0.5dB up to 1.717GHz and 20-dB stopband extends up to 3.4f_c     

Upscale integration of normalized difference vegetation index: theproblem of spatial heterogeneity

The correspondence between the normalized difference vegetation index (NDVI) calculated from average reflectances, M_NDVI , and NDVI integrated from individual NDVIs, I_NDVI , by simulating AVHRR data from high spatial resolution SPOT 1 Haute Resolution Visible radiometer and Landsat Thematic Mapper data is analyzed. For the considered sites, located in tropical West Africa and temperate France, and the scales analyzed, 300-1000 m, a strong correlation exists between the two types of index. The relationship is almost perfectly linear, with a slope depending slightly on the variability of the vegetation cover. Effecting the scale change using M_NDVI instead of I_NDVI does not introduce significant errors     

Optical multiplication using a bisected intersecting waveguide

We present an analysis of a bisected intersecting waveguide in periodically poled lithium niobate that can produce and isolate the second-order optical product E(ω₁+ω₂)~E₁(ω₁ )E₂(ω₂) free from the near degenerate second harmonics. Model calculations of such a device fabricated in quasi-phase matched (QPM) LiNbO₃ predict a conversion efficiency of ≈1.5%/W, about 15% that of a straight waveguide of the same length, and a crosstalk of ≲-30 dB     

Erasure, list, and detection zero-error capacities for low noiseand a relation to identification

For the discrete memoryless channel (χ, y, W) we give characterizations of the zero-error erasure capacity C_er and the zero-error average list size capacity C_al in terms of limits of suitable information (respectively, divergence) quantities (Theorem 1). However, they do not “single-letterize.” Next we assume that χ⊂y and W(x|x)>0 for all x∈χ, and we associate with W the low-noise channel W_ϵ, where for y ⁺(x)={y:W(y|x)>0} W_ϵ(y|x)={1, if y=x and |y⁺(x)|=1 1-ϵ, if y=x and |y⁺(x)|>1 e/|y ⁺(x)|-1, if y≠x. Our Theorem-2 says that as ε tends to zero the capacities C_er(W_ε) and C_al (W_ε) relate to the zero-error detection capacity C _de(W). Our third result is a seemingly basic contribution to the theory of identification via channels. We introduce the (second-order) identification capacity C_oid for identification codes with zero misrejection probability and misacceptance probability tending to zero. Our Theorem 3 says that C_oid equals the zero-error erasure capacity for transmission C_er     

The common randomness capacity of a pair of independent discretememoryless channels

We study the following problem: two agents Alice and Bob are connected to each other by independent discrete memoryless channels. They wish to generate common randomness, i.e. agree on a common random variable, by communicating interactively over the two channels. Assuming that Alice and Bob are allowed access to independent external random sources at rates (in bits per step of communication) of H_A and H_B, respectively, we show that they can generate common randomness at a rate of max{min[H_A+H(W|Q),I(P;V)]+min[H_B +H(V|P), I(Q;W)]} bits per step, by exploiting the noise on the two channels. Here, V is the channel from Alice to Bob, and W is the channel from Bob to Alice. The maximum is over all probability distributions P and Q on the input alphabets of V and W, respectively. We also prove a strong converse which establishes the above rate as the highest attainable in this situation     

A CMOS continuous-time Gm-C filter for PRML read channelapplications at 150 Mb/s and beyond

Design techniques for equiripple phase CMOS continuous-time filters are presented, and their integration within a partial-response maximum likelihood (PRML) disk drive read channel is discussed. A programmable seven-pole two asymmetric zero filter implementation is described based on a new transconductance (G_m) cell. The impact of integrator finite output impedance, excess phase, and other implementation related nonidealities is discussed. A filter tuning circuit that requires an accurate time base but no external components is presented. The filter has a cutoff frequency (f_c) range of 6-43 MHz, where f_c is the -3 dB point of the magnitude transfer function with the two zeros set to infinity. Also, with finite zeros it is able to provide up to 12 dB of boost which is defined as the maximum value of the magnitude transfer function referred to dc. The group delay ripple stays within ±2% for frequencies below 1.75 f _c. The cutoff frequency exhibits a 650 ppm/°C temperature dependency and a variation of ±1%/V with the power supply. Total harmonic distortion (THD) values are below -40 dB at twice the nominal operating input voltage (V_nominal=320 mV peak-to-peak differential), and the dynamic range exceeds 60 dB (for a maximum input signal of 640 mV peak-to-peak differential, maximum bandwidth setting, and no boost). Both the filter and a tuning circuit were implemented in a 0.6-μm single-poly triple-metal n-well CMOS process. They consume 90 mW from a single 5 V power supply and occupy an area of 0.8 mm²      

An Analysis of Angle-Based With Ratio-Based Vegetation Indices

Remotely sensed, angle-based vegetation indices that measure vegetation amounts by the angle between an approximated soil line and a simulated vegetation isoline in the red–near-infrared reflectance space were developed and evaluated in this paper. Ünsalan and Boyer previously proposed an angle-based vegetation index,$theta$(denoted as$theta_ NDVI$in this paper), based on the normalized difference vegetation index (NDVI) with the objective of overcoming the saturation problem in the NDVI. However,$theta_ NDVI$did not consider strong soil background influences present in the NDVI. To reduce soil background noise, an angle-based vegetation index,$theta_ SAVI$, based on the soil-adjusted vegetation index (SAVI), was derived using trigonometric analysis. The performance of$theta_ NDVI$and$theta_ SAVI$was evaluated and compared with their corresponding vegetation indices, NDVI and SAVI. The soil background influence on$theta_ NDVI$was found to be as significant as that on the NDVI.$theta_ NDVI$was found to be more sensitive to vegetation amount than the NDVI at low vegetation density levels, but less sensitive to vegetation fraction at high vegetation density levels. Thus, the saturation effect at high vegetation density levels encountered in the NDVI was not mitigated by$theta_ NDVI$. By contrast,$theta_ SAVI$exhibited insignificant soil background effects and weaker saturation, as in SAVI, but also improved upon the dynamic range of SAVI. Analyses and evaluation suggest that$theta_ SAVI$is an optimal vegetation index to assess and monitor vegetation cover across the entire range of vegetation fraction density levels and over a wide variety of soil backgrounds.     

CMOS high-frequency switched-capacitor filters fortelecommunication applications

A digitally programmable high-frequency switched-capacitor filter for use in a switched digital video (SDV/VDSL) link is described. The highest available clock frequency in the system is 51.84 MHz (f_s =2f_clock=103.68 MHz for double sampling) while the three desired low-pass corner frequencies (f_c) are 8,12, and 20 MHz. The double-sampling, bilinear, elliptic, fifth-order switched-capacitor filter meets the desired -40-dB attenuation at 1.3 f _c, and -30 dB at 1.25 f_c. For the 12-MHz corner frequency setting, given the 2V_pp differential input, the measured worst case total harmonic distortion is -60 dB, with signal-to-noise ratio of 54 dB. The analog power dissipation is 125 mW from a 5-V power supply. The test results indicate that the clock frequency can be increased to 73 MHz without any ill effects. More measurements verify that an all-digital CMOS implementation, utilizing metal-sandwich capacitors, performs as well as the special-layer analog capacitors implementation, with a small reduction in the absolute corner frequencies. The prototype IC's are fabricated in a 0.35-μm 5-V (0.48 μm drawn) CMOS process     

Emissivity maps to retrieve land-surface temperature from MSG/SEVIRI

Retrieval of land-surface temperature (LST) using data from the METEOSAT Second Generation-1 (MSG) Spinning Enhanced Visible and Infrared Imager (SEVIRI) requires adequate estimates of land-surface emissivity (LSE). In this context, LSE maps for SEVIRI channels IR3.9, IR8.7, IR10.8, and IR12.0 were developed based on the vegetation cover method. A broadband LSE map (3-14 /spl mu/m) was also developed for estimating longwave surface fluxes that may prove to be useful in both energy balance and climate modeling studies. LSE is estimated from conventional static land-cover classifications, LSE spectral data for each land cover, and fractional vegetation cover (FVC) information. Both International Geosphere-Biosphere Program (IGBP) Data and Information System (DIS) and Moderate Resolution Imaging Spectrometer (MODIS) MOD12Q1 land-cover products were used to build the LSE maps. Data on LSE were obtained from the Johns Hopkins University and Jet Propulsion Laboratory spectral libraries included in the Advanced Spaceborne Thermal Emission and Reflection Radiometer spectral library, as well as from the MODIS University of California-Santa Barbara spectral library. FVC data for each pixel were derived based on the normalized differential vegetation index. Depending on land cover, the LSE errors for channels IR3.9 and IR8.7 spatially vary from /spl plusmn/0.6% to /spl plusmn/24% and /spl plusmn/0.1% to /spl plusmn/33%, respectively, whereas the broadband spectrum errors lie between /spl plusmn/0.3% and /spl plusmn/7%. In the case of channels IR10.8 and IR12.0, 73% of the land surfaces within the MSG disk present relative errors less than /spl plusmn/1.5%, and almost all (26%) of the remaining areas have relative errors of /spl plusmn/2.0%. Developed LSE maps provide a first estimate of the ranges of LSE in SEVIRI channels for each surface type, and obtained results may be used to assess the sensitivity of algorithms where an a priori knowledge of LSE is required.     

Sensitivity to soil moisture by active and passive microwavesensors

The backscatter measured by radar and the emission measured by a radiometer are both very sensitive to the moisture content m_υ of bare-soil surfaces. Vegetation cover complicates the scattering and emission processes, and it has been presumed that the addition of vegetation masks the soil surface, thereby reducing the radiometric and radar soil-moisture sensitivities. Even though researchers working in the field of microwave remote sensing of soil moisture are all likely to agree with the preceding two statements, numerous claims and counterclaims have been voiced, primarily at symposia and workshops, espousing the superiority of the radiometric technique over the radar, or vice versa. The discussion is often reduced to disagreements over the answer to the following question “Which of the two sensing techniques is less impacted by vegetation cover?” This paper is an attempt to answer that question. Using realistic radiative-transfer models for the emission and backscatter, calculations were performed for three types of canopies, all at 1.5 GHz. The results lead to two major conclusions. First, the accepted presumption that vegetation cover reduces the soil-moisture sensitivity is not always true. Over certain ranges of the optical depth τ of the vegetation canopy and the roughness of the soil surface, vegetation cover can enhance, not reduce, the radar sensitivity to soil moisture. The second conclusion is that under most vegetation and soil-surface conditions, the radiometric and radar soil-moisture sensitivities decrease with increasing τ, and the rates are approximately the same for both sensors, suggesting that at least as far as vegetation effects are concerned, neither sensor can claim superiority over the other     

Coding theorems for Shannon's cipher system with correlated sourceoutputs, and common information

Source coding problems are treated for Shannon's (1949) cipher system with correlated source outputs (X,Y). Several cases are considered based on whether both X and Y, only X, or only Y must be transmitted to the receiver, whether both X and Y, only X, or only Y must be kept secret, or whether the security level is measured by (¹/_KH(X^K|W), (¹/_KH(Y^K|W)) or ¹/_K H(X^KY^K|W) where W is a cryptogram. The admissible region of cryptogram rate and key rate for a given security level is derived for each case. Furthermore, two new kinds of common information of X and Y, say C₁(X;Y) and C₂(X;Y), are considered. C₁(X;Y) is defined as the rate of the attainable minimum core of (X^K,Y^K) by removing each private information from (X^K,Y^K) as much as possible, while C₂(X;Y) is defined as the rate of the attainable maximum core V_C such that if one loses V_C , then each uncertainty of X^K and Y^K becomes H(V_C). It is proved that C₁(X;Y)=I(X;Y) and C₂(X;Y)=min {H(X), H(Y)}. C₁(X;Y) justifies the author's intuitive feeling that the mutual information represents a common information of X and Y     

地磁坐标系下变姿态空间相机的外热流计算

为了提供准确的空间相机外热流数据,提出一种在地磁坐标系下进行频繁姿态变换的空间相机瞬态外热流计算方法。首先,确定了在J2000坐标系下太阳地球的相对位置及太阳辐照强度;其次,计算相机不同位置的地磁纬度,并采用二分法得到相机在轨运行时进出高磁纬地区(|L|60)的轨道时间;然后,依据其地磁纬度,确定相机不同时刻下的在轨姿态。最后,采用蒙特卡洛法(MCM)计算相机的各环境映射面的轨道视角系数,进而得出整轨周期内各环境映射面接受的瞬时外热流。此方法与IDEAS/TMG软件的外热流结果能够较好的吻合。与姿态稳定的相机相比,空间相机姿态频繁变化会导致外热流数值的明显波动。尤其是入光口所在的+Z面,其波动范围为0~1 245.4 W/m2。     

Two-dimensional weight-constrained codes through enumeration bounds

For a rational α∈(0,1), let 𝒜_n×m,α be the set of binary n×m arrays in which each row has Hamming weight αm and each column has Hamming weight αn, where αm and αn are integers. (The special case of two-dimensional balanced arrays corresponds to α=1/2 and even values for n and m.) The redundancy of 𝒜_n×m,α is defined by ρ_n×m,α=nmH(α)-log₂|𝒜 _n×m,α| where H(x)=-xlog₂x-(1-x)log₂(1-x). Bounds on ρ_n×m,α are obtained in terms of the redundancies of the sets 𝒜_ℒ,α of all binary ℒ-vectors with Hamming weight αℒ, ℒ∈{n,m}. Specifically, it is shown that ρ_n×m,α⩽nρ_m,α+mρ _n,α where ρ_ℒ,α=ℒH(α)-log₂|𝒜 _ℒ,α| and that this bound is tight up to an additive term O(n+log m). A polynomial-time coding algorithm is presented that maps unconstrained input sequences into 𝒜_n×m,α at a rate H(α)-(ρ_m,α/m)     

Soil moisture retrieval using the C-band polarimetric scanning radiometer during the Southern Great Plains 1999 Experiment

The Advanced Microwave Scanning Radiometer (AMSR) holds promise for retrieving soil moisture in regions with low levels of vegetation. Algorithms for this purpose have been proposed, but none have been rigorously evaluated due to a lack of datasets. Accordingly, the Southern Great Plains 1999 Experiment (SGP99) was designed to provide C-band datasets for AMSR algorithm development and validation. Ground observations of soil moisture and related variables were collected in conjunction with aircraft measurements using a C-band radiometer similar to the AMSR sensor (6.92 GHz), the Polarimetric Scanning Radiometer with its C-band scanhead (PSR/C). The study region has been the focus of several previous remote sensing field experiments and contains vegetation conditions compatible with the expected capabilities of C-band for soil moisture retrieval. Flights were conducted under a wide range of soil moisture conditions, thus providing a robust dataset for validation. A significant issue found in data processing was the removal of anthropogenic radio-frequency interference. Several approaches to estimating the parameters of a single-channel soil moisture retrieval algorithm were used. PSR/C soil moisture images show spatial and temporal patterns consistent with meteorological and soil conditions, and the dynamic range of the PSR/C observations indicates that the AMSR instrument can provide useful soil moisture information.     

Remote Vector Gaussian Source Coding With Decoder Side Information Under Mutual Information and Distortion Constraints

Let X , Y , Z be zero-mean, jointly Gaussian random vectors of dimensions n_x, n_y, and n_z, respectively. Let P be the set of random variables W such that W harr Y harr (X, Z) is a Markov string. We consider the following optimization problem: _WisinP ^min I(Y; Z) subject to one of the following two possible constraints: 1) I(X; W|Z) ges R_I, and 2) the mean squared error between X and Xcirc = E(X|W, Z) is less than d . The problem under the first kind of constraint is motivated by multiple-input multiple-output (MIMO) relay channels with an oblivious transmitter and a relay connected to the receiver through a dedicated link, while for the second case, it is motivated by source coding with decoder side information where the sensor observation is noisy. In both cases, we show that jointly Gaussian solutions are optimal. Moreover, explicit water filling interpretations are given for both cases, which suggest transform coding approaches performed in different transform domains, and that the optimal solution for one problem is, in general, suboptimal for the other.     

Formation of silicon reentrant cavity heat sinks using anisotropicetching and direct wafer bonding

A novel silicon reentrant cavity heat sink for enhanced liquid cooling of silicon multichip substances has been fabricated using a two-step anisotropic etching process followed by silicon direct wafer bonding. Cavity mouth openings ranging from 8 to 500 μm have been batch fabricated with the two-step process. The reentrant cavities suppress the temperature overshoot normally associated with the transition between the free convection and nucleate boiling regimes of liquid immersion cooling. Nucleate boiling has been observed to occur at heater fluxes below 2 W/cm² for both increasing and decreasing heat flux conditions. Specific thermal contact resistances (heater fluid) of less than 0.6 K-cm²/W have been measured in Freon-22, R-113, and FC-72     

Relief-F筛选波段的小麦白粉病早期诊断研究

为了准确监测小麦白粉病染病早期病情,给喷药防治提供技术指导,论文将染病初期的小麦叶片作为研究对象。首先,利用高光谱图像数据,通过图像特征分割出叶片区域和病斑区域,定量计算病情严重度;其次引入Relief-F算法提取染病早期最敏感波段和波段差,计算出白粉病病害指数PMDI （Powdery mildew disease index）;并通过分析病情指数DI （Disease index）与11种植被指数（含PMDI指数）的相关性及线性模型,得出PMDI模型有最高的决定系数（R2=0.839 9）和最低的均方根误差（RMSE=4.522 0）,效果优于其他病害植被指数的结果（其中,Normalized Difference Vegetation Index,NDVI的模型决定系数最高,R2=0.777 1,RMSE=5.336 4）;最后,选择PMDI和NDVI植被指数分别构建小麦白粉病染病早期病情严重度的支持向量回归模型。结果表明:经敏感波段筛选构建的PMDI指数的预测结果更好,预测模型的R2=0.886 3,RMSE=3.553 2,可以实现小麦白粉病早期无损诊断,这为指导作物病害喷药防治提供重要的技术支撑。     

Land cover dependence in the detection of contaminated pixels insatellite optical data

The detection of partially contaminated pixels over land is necessary for quantitative applications of satellite optical measurements to estimate surface biophysical parameters such as leaf area index or vegetation composition. Threshold-based algorithms suffer from the heterogeneity of land cover and the seasonal variability of the radiation reflected and emitted by the land surface. As an alternative, a method based on a Fourier series approximation to the seasonal trajectory of the normalized difference vegetation index (NDVI) had been previously developed (Cihlar 1996). In this paper, we introduce modifications to the basic algorithm to more closely represent NDVI seasonal trends for different land cover types, as well as a simplified way to determine the time- and pixel-specific contamination thresholds. Based on the tests with 1993-1996 Advanced Very High Resolution Radiometer (AVHRR) data over Canada, the modified procedure effectively detects contaminated pixels for boreal ecosystems after the growing season of interest. The modifications also improved its performance while the growing season is in progress; in this case, at least one complete previous growing season coverage is required to provide the temporal series needed to establish the thresholds. The modified procedure also yields a contamination parameter that may be used to estimate the most likely value for NDVI or other variables for each pixel. It is concluded that the procedure would perform effectively in other areas, provided that the NDVI temporal trajectories of the cover types of interest can he represented by a mathematical model     

An on-line universal lossy data compression algorithm viacontinuous codebook refinement .III. Redundancy analysis

For pt.II see ibid., vol.42, p.822-36 (1996). The Gold-washing data compression algorithm is an adaptive vector quantization algorithm with vector dimension n. In this paper, a redundancy problem of the Gold-washing data compression algorithm is considered. It is demonstrated that for any memoryless source with finite alphabet A and generic distribution p and for any R>0, the redundancy of the Gold-washing data compression algorithm with dimension n (defined as the difference between the average performance of the algorithm and the distortion-rate function D(p,R) of p) is upper-bounded by |_δR /^δD(p,R)|((|A|+2ξ+4 log n)/2n)+σ(logn/n) where _δR/^δD(p,R) is the partial derivative of D(p,R) with respect to R, |A| is the cardinality of A, and ξ>0 is a parameter used to control the threshold in the Gold-washing algorithm. In connection with the results of Zhang, Yang, and Wei (see ibid., vol.43, no.1, p.71-91, 1997) on the redundancy of lossy source coding, this shows that the Gold-washing algorithm has the optimal convergence rate among all adaptive finite-state vector quantizers     

A 0.5-V 1-Msps Track-and-Hold Circuit With 60-dB SNDR

We discuss a design technique that makes possible the operation of track-and-hold (T/H) circuits with very low supply voltages, down to 0.5 V. A 0.5-V 1-Msps T/H circuit with a 60-dB SNDR is presented. The fully differential circuit is fabricated in the CMOS part of a 0.25-mum BiCMOS process, with standard 0.6-V V_T devices, and uses true low-voltage design techniques with no clock boosting and no voltage boosting. The T/H circuit has a measured current consumption of 600 muA