Broadband Model Research Articles

Performance of the meteorological radiation model during the solar eclipse of 29 March 2006

Abstract. Various solar broadband models have been developed in the last half of the 20th century. The driving demand has been the estimation of available solar energy at different locations on earth for various applications. The motivation for such developments, though, has been the ample lack of solar radiation measurements at global scale. Therefore, the main goal of such codes is to generate artificial solar radiation series or calculate the availability of solar energy at a place. One of the broadband models to be developed in the late 80's was the Meteorological Radiation Model (MRM). The main advantage of MRM over other similar models was its simplicity in acquiring and using the necessary input data, i.e. air temperature, relative humidity, barometric pressure and sunshine duration from any of the many meteorological stations. The present study describes briefly the various steps (versions) of MRM and in greater detail the latest version 5. To show the flexibility and great performance of the MRM, a harsh test of the code under the (almost total) solar eclipse conditions of 29 March 2006 over Athens was performed and comparison of its results with real measurements was made. From this hard comparison it is shown that the MRM can simulate solar radiation during a solar eclipse event as effectively as on a typical day. Because of the main interest in solar energy applications about the total radiation component, MRM focuses on that. For this component, the RMSE and MBE statistical estimators during this study were found to be 7.64% and −1.67% on 29 March as compared to the respective 5.30% and +2.04% for 28 March. This efficiency of MRM even during an eclipse makes the model promising for easy handling of typical situations with even better results.

A strict test in climate modeling with spectrally resolved radiances: GCM simulation versus AIRS observations

The spectrally resolved infrared radiances observed by AIRS provide a strict and insightful test for general circulation models (GCMs). We compare the clear‐ and total‐ sky spectra simulated from the Geophysical Fluid Dynamics Laboratory GCM using a high resolution radiation code with the AIRS observations. After ensuring consistency in the sampling of the observed and simulated spectra and a proper representation of clouds in the radiance simulation, the observed and simulated global‐mean radiances are shown to agree to within 2 K in the window region. Radiance discrepancies in the water vapor v2 (1300–1650 cm−1) and carbon dioxide v2 (650–720 cm−1) bands are consistent with the model biases in atmospheric temperature and water vapor. The existence of radiance biases of opposite signs in different spectral regions suggests that a seemingly good agreement of the model's broadband longwave flux with observations may be due to a fortuitous cancellation of spectral errors. Moreover, an examination of the diurnal difference spectrum indicates pronounced biases in the model‐simulated diurnal hydrologic cycle over the tropical oceans, a feature seen to occur in other GCMs as well.

GRB 051022: Physical Parameters and Extinction of a Prototype Dark Burst

GRB051022 was undetected to deep limits in early optical observations, but precise astrometry from radio and X-ray showed that it most likely originated in a galaxy at z~0.8. We report radio, optical, near infra-red and X-ray observations of GRB051022. Using the available X-ray and radio data, we model the afterglow and calculate the energetics of the afterglow, finding it to be an order of magnitude lower than that of the prompt emission. The broad-band modeling also allows us to precisely define various other physical parameters and the minimum required amount of extinction, to explain the absence of an optical afterglow. Our observations suggest a high extinction, at least 2.3 magnitudes in the infrared (J) and at least 5.4 magnitudes in the optical (U) in the host-galaxy restframe. Such high extinctions are unusual for GRBs, and likely indicate a geometry where our line of sight to the burst passes through a dusty region in the host that is not directly co-located with the burst itself.

A Broadband and Scalable On-Chip Inductor Model Appropriate for Operation Modes of Varying Substrate Resistivities

A broadband and scalable model is developed to accurately simulate on-chip inductors with various dimensions and substrate resistivities. The broadband accuracy is proven over frequencies of up to 20 GHz, even beyond resonance. A new scheme of resistance-inductance-capacitance networks is deployed for the spiral coils and substrate to account for 3-D eddy current, substrate return path, and spiral coil to substrate coupling effects. The 3-D eddy current is identified as the key element essential to accurately simulate the broadband characteristics. Electromagnetic simulation using the Advanced Design System momentum is conducted to predict the on-chip inductor performance corresponding to a wide range of substrate resistivities(PSi = 0.05-1 KOmega ldr cm) ldr Three operation modes such as transverse electromagnetic mode, slow-wave mode, and eddy current mode are reproduced. The model parameters manifest themselves as physics-based through relevant correlation with PSi over three operation modes. The onset of slow-wave mode can be consistently explained by a key element Rp introduced in our model, which accounts for the conductor loss due to an eddy current arising from magnetic field coupling through a substrate return path. This broadband and scalable model is useful for radio frequency circuit simulation. In addition, it can facilitate an optimum design of on-chip inductors through the physics-based model parameters relevant to varying substrate resistivities.

A time‐domain extraction for the spice‐compatible models of power delivery networks in PCB

AbstractSimultaneous switch noise, or power/ground bounce noise, on the power and ground planes of high‐speed circuit packages is one of the main concerns of signal integrity or power integrity issues. A novel time‐domain approach is proposed to synthesize the broadband models of the resonance effect of power/ground planes. Either from measurements by time‐domain reflectrometry or simulations by the finite‐difference time‐domain method, the time‐domain step response of the planes is characterized with a pole‐residue representation obtained through the matrix pencil method. A new equivalent circuit models are then synthesized through the pole‐residue representations. The synthesized model can accurately predict the resonance behavior of power/ground planes over a wide frequency range. These models can be efficiently incorporated into the currently available circuit simulator such as HSPICE or Agilent ADS for the consideration of power/ground bouncing noise in high‐speed circuits. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3001–3004, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22967

Validating tomographic model with broad-band waveform modelling: an example from the LA RISTRA transect in the southwestern United States

SUMMARY Traveltime tomographic models of the LA RISTRA transect produce excellent waveform fits if we amplify the damped images. We observe systematic waveform distortions across the western edge of the Great Plains from South American events, starting about 300 km east of the centre of the Rio Grande Rift. The amplitude decreases by more than 50 per cent within array stations spanning less than 200 km while the pulse width increases by more than a factor of 2. This feature is not observed for the data arriving from the northwest. While the S-wave tomographic image shows a fast slab-like feature dipping to the southeast beneath the western edge of the Great Plains, synthetics generated from this model do not reproduce the waveform characteristics. However, once we modify the tomographic image by amplifying the velocity contrast between the slab and adjoining mantle by a factor of 2‐3, the synthetics produce observed amplitude decay and pulse broadening. In addition to the traveltime delay, amplitude variation due to wave phenomena such as slab diffraction, focusing and defocusing provide much tighter constraints on the geometry of the fast anomaly and its amplitude and sharpness as demonstrated by a forward sensitivity test and snapshots of the seismic wavefield. Our preferred model locates the slab 200 km east of the Rio Grande Rift dipping 70 ◦ ‐75 ◦ to the southeast, extending to a depth near 600 km with a thickness of 120 km and a velocity of about 4 per cent fast. In short, adding waveform and amplitude components to regional tomographic studies can help validate and establish structural geometry, sharpness and velocity contrast.

Broadband Spectral Reflectance Models of Turfgrass Species and Cultivars to Drought Stress

The objective of this study was to assess canopy broadband spectral reflectance for turfgrasses under drought stress. Optimum turf quality (TQ) and leaf firing (LF) models were developed and compared based on two, three, and five wavelength bands. Sods of bermudagrass (Cynodon dactylon L. × C. transvaalensis Burtt‐Davy), seashore paspalum (Paspalum vaginatum Swartz), zoysiagrass (Zoysia japonica Steud.), and St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and seeded tall fescue (Festuca arundinacea Schreb.) were used in this study with three cultivars each of bermudagrass, seashore paspalum, and tall fescue. Traditional vegetation indices (VIs) based on two bands within 660 to 950 nm were not as sensitive as three to five broadband models using a wider band range of 660 to 1480 nm. Optimum models were cultivar specific models, even within a species. The broadband wavelength at R900 and R1200 should be considered in drought sensitive spectral models since they were most often observed and exhibited high partial R2 values. These results suggest that mobile broadband spectral devices to map turfgrass responses to drought stress would benefit by the availability of three to five broadbands that could be user selected for optimum, cultivar specific models.

Prediction of Losses Caused by Roughness of Metallization in Printed-Circuit Boards

In this paper, the effect of metal roughness on the total loss, the extracted tandelta, and signal integrity of typical interconnections found in printed-circuit boards is extracted from measurements on three different materials. The differing characteristics of the roughened metal cross sections are highlighted, and a simplified, practical, 2-D, causal, broadband modeling methodology is shown

Modeling and Characterization of On-Chip Transformers for Silicon RFIC

A broadband and scalable lumped-element model for silicon on-chip transformers is presented. Model elements are driven from layout and process technology specifications. We provide simple and accurate expressions for evaluating the self inductance and the mutual coupling coefficient. The effects of various layout parameters, including transformer area, number of turns, and turns ratio, on transformer electrical response have been investigated. Model accuracy is demonstrated by comparing simulated and measured S-parameters, minimum insertion loss, quality factor, coils inductance, and magnetic coupling of several transformers with a wide range of configurations

Krylov model order reduction of finite element approximations of electromagnetic devices with frequency‐dependent material properties

AbstractA methodology is presented for the Krylov subspace‐based model order reduction of finite element models of electromagnetic structures with material properties and impedance boundary conditions exhibiting arbitrary frequency dependence. The proposed methodology is a generalization of an equation‐preserving Krylov model order reduction scheme for methodology for second‐order, linear dynamical systems. The emphasis of this paper is on the application of this method to the broadband model order reduction of planar circuits including lossy strips of arbitrary thickness and lossy reference planes. In particular, it is shown that the proposed model order reduction methodology provides for the accurately modelling of the impact of the frequency dependence of the internal impedance per unit length of the thick lossy strip on the electromagnetic response of the stripline structure over a very broad, multi‐GHz frequency band, extending all the way down to frequencies in the DC neighbourhood. In addition, the application of the proposed methodology to the broadband modelling of electromagnetic coupling between strips on either side of a lossy ground plane is demonstrated. Copyright © 2007 John Wiley & Sons, Ltd.

Novel all-optical AND and NOR gates based on semiconductor fiber ring laser

A new scheme for all-optical AND gate and NOR gate based on simultaneous four-wave mixing (FWM) and cross-gain modulation (XGM) in a semiconductor fiber ring laser (SFRL) is proposed, and a comprehensive broad-band dynamic model of this kind of all-optical logic gates is presented. By numerical simulation, the effects of the input signal peak power and the coupling of the couplers in SFRL on the output performances of the logic gates are analyzed.

A Broadband Single-Stage Equivalent Circuit for Modeling LTCC Bandpass Filters

A single-stage equivalent circuit is proposed to model microwave bandpass filters (BPFs) fabricated in low-temperature co-fired ceramic (LTCC) technology up to several times its passband frequency. The equivalent circuit adopts a modified T topology with the expandable multilayer resonators to achieve an extremely large bandwidth. It can be efficiently established from the measured S-parameters using direct extraction or rational approximation. As a result, the modeled S-parameters for a 2.45-GHz wideband local area network (WLAN) LTCC BPF show good agreement with the measured results over a wide frequency range up to 8.5 GHz. Such a broadband model can be used to accurately predict the suppression of harmonics and interferences in system simulation of the WLAN front-end modules

A comparison of broadband models for sand sediments

Chotiros and Isakson [J. Acoust. Soc. Am. 116(4), 2011-2022 (2004)] recently proposed an extension of the Biot-Stoll model for poroelastic sediments that makes predictions for compressional wave speed and attenuation, which are in much better accord with the experimental measurements of these quantities extant in the literature than either those of the conventional Biot-Stoll model or the rival model of Buckingham [J. Acoust. Soc. Am. 108(6), 2796-2815 (2000)]. Using a local minimizer, the Nelder-Mead simplex method, it is shown that there are generally at least two choices of the Chotiros-Isakson parameters which produce good agreement with experimental measurements. Since one postulate of the Chotiros-Isakson model is that, due to the presence of air bubbles in the pore space, the pore fluid compressibility is greater than that of water, an alternative model based on a conjecture by Biot [J. Acoust. Soc. Am. 34(5), 1254-1264 (1962)], air bubble resonance, is considered. While this model does as well or better than the Chotiros-Isakson model in predicting measured values of wave speed and attenuation, the Rayleigh-Plesset theory of bubble oscillation casts doubt on its plausibility as a general explanation of large dispersion of velocity with respect to frequency.

Shortwave radiative closure studies for clear skies during the Atmospheric Radiation Measurement 2003 Aerosol Intensive Observation Period

The Department of Energy's Atmospheric Radiation Measurement (ARM) program sponsored a large aerosol intensive observation period (AIOP) to study aerosol during the month of May 2003 around the Southern Great Plains (SGP) Climate Research Facility (CRF) in north central Oklahoma. Redundant measurements of aerosol optical properties were made using different techniques at the surface as well as in vertical profile with sensors aboard two aircraft. One of the principal motivations for this experiment was to resolve the disagreement between models and measurements of diffuse horizontal broadband shortwave irradiance at the surface, especially for modest aerosol loading. This paper focuses on using the redundant aerosol and radiation measurements during this AIOP to compare direct beam and diffuse horizontal broadband shortwave irradiance measurements and models at the surface for a wide range of aerosol cases that occurred during 30 clear‐sky periods on 13 days of May 2003. Models and measurements are compared over a large range of solar‐zenith angles. Six different models are used to assess the relative agreement among them and the measurements. Better agreement than previously achieved appears to be the result of better specification of input parameters and better measurements of irradiances than in prior studies. Biases between modeled and measured direct irradiances are in the worst case 1%, and biases between modeled and measured diffuse irradiances are less than 1.9%.

Towards Viable Personal Networks and FedNets -- a Value-Web Perspective

The concepts of Personal Networks (PNs) and Federated Networks (FedNets) have been introduced before, but there are no studies published yet about migration strategies towards viable solutions in the market. One of the main reasons is the lack of a clear vision about the different values that various parties involved in achieving PNs and FedNets have to offer to each other and the end user. In fixed broadband communication such value chains and business models are already commonly used for rolling out complex service offering based on fiber-to-the-home and broadband home networks. In this paper we use the knowledge from these business domains to approach the problem of PNs and FedNets.

Measurements and modeling of low‐frequency air‐sea‐interface scattering

The acoustic scattering response of the undersea air‐sea interface can be quite sensitive to ocean surface conditions, scattering geometry, and acoustic frequency. This paper presents both measurements and modeling of low‐frequency (<1500 Hz) scattering strength. The modeling is based on a small slope approximation (SSA) that accounts for directional surface‐wave roughness spectra with low‐wave‐number cutoffs. To provide an operationally useful predictive tool, a set of surface‐wave spectral parameters (strength, exponent, and peak) are determined by nonlinear, multi‐parameter fits to broadband, vertically bistatic surface backscattering strength data, leading to a semi‐empirical bistatic model environmentally parameterized solely by the wind speed. The same SSA theory is also used to estimate the coherent‐reflection loss given the frequency, angle, and wind speed. These broadband models are then used to explore the dependence of both incoherent and coherent sea‐surface scattering on frequency, angle, and wind speed. [Work supported by ONR and PEO C4I & Space (PMW‐180).]

A broadband and scalable model for on-chip inductors incorporating substrate and conductor loss effects

A new T-model has been developed to accurately simulate the broadband characteristics of on-Si-chip spiral inductors, up to 20 GHz. The spiral coil and substrate RLC networks built in the model play a key role responsible for conductor loss and substrate loss in the wideband regime, which cannot be accurately described by the conventional /spl pi/-model. Good match with the measured S-parameters, L(/spl omega/), Re(Z/sub in/(/spl omega/)), and Q(/spl omega/) proves the proposed T-model. Besides the broadband feature, scalability has been justified by good match with a linear function of coil numbers for all model parameters employed in the RLC networks. The satisfactory scalability manifest themselves physical parameters rather than curve fitting. A parameter extraction flow is established through equivalent circuit analysis to enable automatic parameter extraction and optimization. This scalable inductor model will facilitate optimization design of on-chip inductor and the accuracy proven up to 20 GHz can improve RF circuit simulation accuracy demanded by broadband design.

A New Circuit Augmentation Method for Modeling of Interconnects and Passive Components

This paper presents a new methodology for automated broadband model generation from S-parameter data for interconnects and passive components. The new methodology is based on augmenting an existing equivalent circuit model with a macromodel (black-box) network described by rational functions while simultaneously perturbing the equivalent circuit component values. The macromodel network is determined using standard least-squares or vector-fitting approaches. The perturbation of the equivalent circuit parameter values is achieved during the macromodel generation by means of global optimization based on intelligent search algorithms. The new approach is demonstrated on several two-port test example structures including a broadband probe tip structure and a CMOS spiral inductor.

Combined Circuit-Electromagnetic Simulation Using Multiregion Time Domain Integral Equation Scheme

A full-wave time domain integral equation based formulation for broadband modeling of finite conductors and dielectrics in high-speed microelectronics is presented. An efficient and accurate coupling scheme is developed to enable surface integral equations to couple to modified nodal analysis for combined circuit-electromagnetic systems such as those arising in microwave and RF circuits

Surface-based broadband electromagnetic-circuit simulation of lossy conductors

Surface-only boundary-element formulations are particularly efficient for electromagnetic modelling of microelectronic structures that consist of homogeneous sections, such as interconnects, packaged and on-chip microwave and analogue circuit components. However, broadband modelling, as necessitated in digital and ultrawideband systems, is not possible with standard surface-only formulations that rely on the surface impedance technique to model conductor loss. In existing methods, recourse is taken to volumetric solvers in such cases. A surface-only formulation is presented that is truly broadband, and solves the internal field problem exactly, utilising a newly developed lossy medium quadrature. The value of the proposed technique lies in its seamless behaviour over wide frequency ranges and its direct interconnectivity to circuit-level analyses. In particular, frequency-dependent parameters can be extracted via a surface-only approach, valid at all frequencies. The electromagnetic analysis is coupled to a lumped circuit formulation, via a recently developed contact model.