Adrian K Fung

The University of Texas at Arlington | UTA · Department of Electrical Engineering

Description A successor to the classic Artech House Microwave Remote Sensing series, this comprehensive and up-to-date resource previously published by University of Michigan Press provides you with theoretical models, system design and operation, and geoscientific applications of active and passive microwave remote sensing systems. To facilitate u...

Scattering of a plane, horizontally polarized electromagnetic wave in any direction from a slightly rough, lossless layer is considered. The layer is rough on both sides and the medium below the layer is assumed perfectly conducting. Small-perturbation theory is used and first- and second-order results are obtained. It is found that waves scattered...

In this paper, we study the bistatic scattering using an advanced integral equation model (AIEM). By keeping all the surface current terms in the Kirchhoff surface fields, the bistatic scattering coefficients are obtained. For simplification, the complete Kirchhoff field did not cast into the derivation of the complementary field. We compare varied...

The standard integral equation for the surface current is solved iterativcly to obtain an estimate of the surface current on a perfectly conducting randomly rough surface. The far-zone scattered fields and the backscattering coefficients for vertical, horizontal and cross-polarizations are then computed using this current estimate. The polarized ba...

Most natural surfaces have been reported to have an exponential-like correlation function and generally contain more than one scale of roughness. In this paper we want to show that a multiscale Gaussian-distributed surface with a differentiable correlation function also possesses an exponential-like correlation function except near the origin. As a...

The method of moment (MoM) is a numerical procedure for solving the equation Lf = g, where L is a continuous linear operator, f is the unknown function to be determined and g is a known excitation. In essence, the procedure converts the linear equation into a matrix equation and determines the unknown function in the form of a set of samples of the...

In this study we analyzed backscattering mechanism using a non-Gaussian correlation function, called exponential-like, for rough surface. The corresponding surface spectrum properties were investigated. It contains an excessive amount of high frequency spectral components. But unlike exponential one, it has rms slopes and allows to obtain the desir...

This article treats microwave scattering models for soil surface, leafy vegetation, and snow-covered terrain. These models are generally useful for understanding the physics of the scattering problem, the design of scatterometers for specific applications, and the inversion of physical or geometric terrain parameters in remote sensing. It begins wi...

Most existing EM scattering models for a vegetation medium assume that the leaves have an orientation distribution and each leaf scatters independently. For vegetations that possess compound leaves (for example leaves of a walnut tree) such an assumption is generally not valid. For this type of vegetation the leaves scatter in groups and it is each...

In this study we show that backscattering models are available for a variety of surface conditions including surfaces with a narrow or a broad surface spectrum. In particular, we shall consider the application of three backscattering models in algebraic form to field measurements and numerical simulation results. All three models have a wider range...

Abstract—From a very roughly random,surface the backscattering enhancement,is predicted due to the constructive interference of multiple surfaces scattering. For specialized surfaces involving roughness large compared with the incident wavelength, the backscattering enhancement,takes place.,The phenomenon,of backscatter enhancement becomes evident...

The integral equation approach to modeling scattering from rough surfaces was introduced in 1992. At that time, it was noted that there was a need to find a transition reflection coefficient that could change its argument from the incident angle to the specular angle as frequency or roughness scale got large. One such reflection coefficient was pub...

A Global Positioning System (GPS) transmitter-receiver pair form a bistatic radar for ocean remote sensing when the receiving platform carries a downlooking antenna capable of collecting the GPS signal scattered off the ocean surface. The aggregate GPS signal scattered by the ocean and received in a general bistatic configuration has been calculate...

The contribution of bistatic multiple scattering from randomly rough surfaces is studied. A model with consideration of multiple surface scattering for bistatic surface scattering from a randomly very rough surface is developed on an approximation of a pair of integral equations. Without the consideration of multiple surface scattering, a considera...

Summary form only given. In the study of scattering from randomly rough surfaces, numerical simulation methods have been used to generate a surface with known properties and then to compute scattering from it without using simplifying assumptions that are in common use in theoretical modeling methods. In practice, no technique is completely free fr...

This paper presents a model of microwave emissions from rough surfaces. We derive a more complete expression of the single-scattering terms in the integral equation method (IEM) surface scattering model. The complementary components for the scattered fields are rederived, based on the removal of a simplifying assumption in the spectral representati...

In surface scattering model applications a large variety of roughness conditions are encountered: some surfaces may be described with one roughness scale and others with more than one roughness scales; some surfaces are correlated exponentially, Gaussian-like or anywhere between the two. In this study we want to show two backscattering models in al...

The original IEM surface scattering model used a simplified surface current estimate leading to relatively simple but accurate results for forward and backscattering configurations. Since then other estimates of the surface current based upon the same set of integral equations have appeared in the literature. A major reason for considering a more c...

In the development of the IEM model for surface single scattering a simplifying assumption was applied to the phase of the Green's function in the average power calculation leading to a surface scattering model in algebraic form. In this paper we remove this simplifying assumption yielding a more complex model but still in algebraic form. We shall...

Major developments on active and passive microwave remote sensing of soil moisture over the last twenty five years are reported. This chapter begins with the basic principles and controlled, experimental studies with ground truth on active and passive sensing of soil moisture. Then, the indications of field experiments on the applicability and prac...

In the development of wave scattering models for randomly dielectric rough surfaces, it is usually assumed that the Fresnel reflection coefficients could be approximately evaluated at either the incident angle or the specular angle. However, these two considerations are only applicable to their respective regions of validity. A common question to a...

A bistatic electromagnetic wave scattering model for the sea surface is developed to examine its wind dependence property over a wide range of incident angles along the specular direction. This is done by combining an existing scattering model with a sea spectrum recently reported in the literature. In general, electromagnetic wave scattering from...

In the development of the IEM model for surface single scattering a simplifying assumption was applied to the phase of the Green's function in the average power calculation leading to a surface scattering model in algebraic form. We remove this assumption yielding a more complex model but still in algebraic form. We show that the simplifying assump...

A GPS transmitter-receiver pair form a bistatic radar for ocean remote sensing when the receiving platform carries a downlooking antenna capable of collecting the GPS signal scattered off the ocean surface. The aggregate GPS signal scattered by the ocean and received in a general bistatic configuration has been calculated for representative geometr...

A FM-CW ground base C-band scatterometer is used to measure the bare soil surface. The measurement was conducted at different incident angles and for two soil moisture conditions. In-situ measurement is also arranged simultaneously in order to verify the retrieved moisture. During the moisture retrieval, the integration equation method (IEM) is use...

A technique for improving the topology of a trained neural network, used for an inversion or classification problem, is presented. The technique models the multilayer perceptron as a power series, which allows us to (1) remove units from the network which are well-approximated by zero-degree or first-degree polynomials, (2) measure the effect of re...

Previously, it has been shown that neural networks approximate minimum mean square estimators. In minimum mean square estimation, an estimate ## of the M-dimensional random parameter vector # is obtained from a noisy N-dimensional input vector y where y has an additive noise component e. For the Cramer-Rao maximum a-posteriori bounds on the varianc...

Our investigation of the use of radar imaging method for the detection and identification of buried anti-personnel mines by numerical simulation based on the FD-TD method and by laboratory experiments has led to the following findings: (a) a mine should be larger than or equal to two wavelengths for it to be imaged under the multi-static configurat...

The authors derive the multiple scattering expression within the framework of an IEM model for rough surface scattering. The complementary field coefficients are rederived based on a new surface slope expressions which are dependent on spatial variables. This leads to a more complete expression of the multiple scattering terms, thus allowing the au...

A bistatic electromagnetic wave scattering model for the sea surface is developed to examine its wind dependence property over a wide range of incident angles along the specular direction. This is done by combining an existing scattering model with a sea spectrum calibrated by altimeter measurements at 14 GHz. Generally, surface scattering is sensi...

In ocean surface scattering many investigators believe that only a certain portion of the sea spectrum is responsible for scattering along a given direction of interest. This is based on the fact that different roughness scales dominate scattering in different directions. As a result when the direction of observation is known, only a certain portio...

In this study we investigate the detection of plastic anti- personnel mine simulants of several sizes using radar and IR imaging. The problem is first studied numerically with the finite-difference, time-domain method and an inverse synthetic aperture radar imaging algorithm to estimate the optimum conditions in dielectric contrast between the mine...

Investigates the geophysical and thermodynamic effects of snow on sea ice in defining the electromagnetic (EM) interaction within the microwave portion of the spectrum. The authors combine observational evidence of both the physical and thermodynamic characteristics of snow with direct measurements of scattering and emission at a variety of frequen...

The spatial and temporal distribution of new and young sea ice types are of particular interest because of the influence this can exert on the heat and mass balance of the polar sea ice. The objective of the present work is to characterize the temporal evolution of the electromagnetic (EM) signatures of sea ice from initial formation through the de...

Recent advances in forward modeling of the electromagnetic scattering properties of sea ice are presented. In particular, the principal results include the following: (1) approximate calculations of electromagnetic scattering from multilayer random media with rough interfaces, based on the distorted Born approximation and radiative transfer (RT) th...

Inverse scattering algorithms for reconstructing the physical properties of sea ice from scattered electromagnetic field data are presented. The development of these algorithms has advanced the theory of remote sensing, particularly in the microwave region, and has the potential to form the basis for a new generation of techniques for recovering se...

Efficient algorithms that incorporate different types of spectral data and ancillary data are being developed to extract continuous vegetation variables. Inferring continuous variables implies that functional relationships must be found among the predicted variable(s), the remotely sensed data and the ancillary data. Neural networks have attributes...

The effects of soil and mine parameters on microwave imaging are investigated based on Finite-Difference Time-Domain (FD- TD) simulation and laboratory studies. Range of soil permittivity considered is from 2.6 to 7.6 corresponding to dry soil and a volumetric soil moisture of 16%. Both plastic and metallic mines are imaged. The diameter of the min...

Radar detection and identification of buried objects such as landmines relies on the wave scattering characteristics of the object and signal processing techniques. The effects of soil and object parameters on microwave imaging are investigated based on Finite-Difference Time-Domain (FD-TD) simulation and laboratory studies. Range of soil permittiv...

A combined surface-volume emission model based on the radiative transfer formulation for an inhomogeneous layer above an inhomogeneous half space is developed using a dense medium phase function. This phase function gives the scattering properties of coherent scattering from a group of randomly positioned scatterers within a unit volume. Laboratory...

A transition function for estimating the Fresnel reflection coefficient over the active frequency range is proposed based on two-dimensional moment method simulation. It naturally connects two approximations of the Fresnel coefficients R(θ) and R(θsp). In the authors' comparisons, the model predictions by the integral equation model (IEM) with the...

In this article, a backscatter theory for an electrically dense medium is presented. The random medium is modeled by a layer of randomly distributed dielectric spherical scatterers, bounded on top and bottom by a rough surface. The phase matrix for the discrete spherical scatterers is evaluated using the dense medium phase and amplitude correction...

Most of the rough surfaces are generally multiscale in nature as observed by radar even at narrow-band. In this paper, we apply the modulation concept to study the characteristics of backscattering from such a multiscale surface, using the IEM scattering model. The modulated surface is special kind of multiscale surface in that a random surface is...

A combined surface-volume scattering model based on the radiative transfer formulation for an inhomogeneous layer above an inhomogeneous half space is developed using a dense medium phase function. This phase function gives the scattering properties of coherent scattering from a group of randomly positioned scatterers within a unit volume. For a ba...

A surface scattering model based on the integral equation method is examined in terms of its applicability to laboratory measurements. The Fresnel reflection coefficients used in the model have been approximated as a function of the incidence angle at low frequency and as a function of the specular angle at high frequency. Based on a limited set of...

The IEM surface scattering model was applied to interpret sets of multifrequency, multipolarization radar measurements acquired from rough soil surfaces with measured permittivity profiles. The wetness was induced by irrigation and the profile was generated by evaporation. It is known that surface roughness parameters are difficult to estimate and...

The albedo and nadir incident polarized BRDF were measured at λ=633 nm for five different Schott glasses. Measurements were acquired using a polarized goniometer and a Minolta spectrophotometer. The Schott glass samples were in the form of particles which were obtained by crushing Schott glass plates with known absorption coefficient and index of r...

In the late 1980s backscattering enhancement and strong depolarization of waves scattered from randomly rough Gaussian surfaces with large rms slopes were observed in optical and millimeter measurements. It was noted that backscattering enhancement was most prominent, when the surface rms slope was of the order of unity, a condition under which mul...

A dense medium phase matrix developed based on the concept of random lattice perturbation is employed in the radiative transfer theory to calculate the coand cross-polarized backscatter from a layer of randomly distributed spherical scatterers. The position randomness properties are characterized by the variance and correlation function of scattere...

The objective of this study is to develop a surface scattering model including multiple scattering based on extending an existing integral-equation-based surface scattering model (IEM). This is done by removing a simplifying assumption in the spectral representation of the Green's function used in the scattered field expression of the IEM surface s...

The authors examine the use of a robust statistical inversion approach to the estimation of soil moisture and roughness statistics from backscatter measurements. Two sets of basis functions are examined; the first is a set of basis functions from multinomial combinations of the inputs (termed the MBF) while the second is a set of basis functions ge...

In the derivation of the conventional scattering phase matrix of a discrete random medium, the far-field approximation is usually assumed. In this paper, the phase matrix of a dense discrete random medium is developed by relaxing the far-field approximation and accounting for the effect of volume fraction and randomness properties characterized by...

The IEM surface scattering model is generalized to include the possible existence of a dielectric profile such as observed in drying conditions after rain. It is shown that for such a case, the generalized signal model including this improvement in reflectivity may give better agreement with backscatter measurements for some data sets. Hence, such...

For purposes of verifying inverse and forward scattering models for sea ice, and to develop a better understanding of scattering and emission behaviours from sea ice, a target is built whose dielectric properties are similar to those of sea ice. This paper briefly describes the investigation of materials leading to the construction of a 12 layer ep...

A dense medium scattering model based on the standard radiative transfer formulation but with a scattering phase function for a group of scatterers as opposed to the conventional single scatterer phase function is developed to account for volume scattering from saline ice. Surface scattering due to air-ice and ice-water boundary is accounted for us...

Scattering and emission models for an irregular layer of dense inhomogeneous medium is developed and applied in the analysis of dry snow scattering and emission in the range 35-140 GHz. The models are developed based on the matrix doubling formulation, and accounts for full incoherent multiple scattering inside the snow layer. The effects of close...

The IEM surface scattering model was developed based on an approximate solution of a pair of integral equations governing the surface current. Among the assumptions leading to the approximation is the use of a simplified expression for the Green's function in spectral form. In particular, it was argued that the absolute value of the difference in t...

Most of the studies in the past used empirical phase functions that were not directly related to the physical and electromagnetic properties of the medium. These phase functions do not conserve energy. Although one can normalize these functions to realize conservation, no meaningful albedo or extinction properties can be derived from them, and ener...

The polarized bidirectional reflectance distribution function is measured for a Spectralon calibration target using an automated, broadband, polarized, optical goniometer. Measurements are acquired for illumination angles of 0, -20, -30, -40 -50, and -60 degrees as a function of receiver view angle. Both like- and cross-polarized components are mea...

An examination of soil particles from very fine to medium sand surfaces has indicated that they are generally on the order of 50 to 500 μm. Thus, at an incident wavelength around 0.6 μm, the incident light should “see” microscopic roughness features on the particle rather than its microscopic features. It is anticipated that the macroscopic feature...

An FD-TD algorithm is used to compute the scattering from objects embedded in a homogeneous medium with a rough top boundary. The rough top boundary is modeled as a randomly rough surface with Gaussian correlation function and height distribution. A three dimensional randomly rough surface with specified correlation length and height standard devia...

The frequency dependence of statistics of radar signals scattered from forest are investigated through a simulation study based on a radiative-transfer theory. A forest canopy is modelled as a volume of needle-shaped or disc-shaped leaves and finite-length, cylindrical branches. It is expected that at radar frequencies above the X-band, scattering...

Experiments were performed at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, NH, to precisely determine the relative contributions of surface and volume scattering from saline ice that has well-known surface roughness characteristics. The ice growth phase of the experiment made use of two 6-ft diameter tanks and...

Through a combined study using scattering models and measurements from saline ice with and without snow cover, the authors found that the presence of snow cover can generate either a larger dielectric discontinuity at the snow-ice interface or a rougher interface condition than the case without snow cover. This happens because of the possibility of...

A surface scattering model based on the integral equation method is examined in terms of its applicability to laboratory and field measurements. The examination covers angular, polarization and frequency properties and includes backscattering and bistatic cases. The laboratory measurements include both backscattering and bistatic scattering from a...

The conventional scattering phase matrix is developed based on the assumption that the scatterers are in the far field of one another. In an electrically dense medium where there is more than one scatterer within the distance of a wavelength, this approximation no longer holds. Generally two types of corrections are necessary: the amplitude and the...

A microwave polarimetric scattering model for a forest canopy is developed based on the iterative solution of the vector radiative transfer equations up to the second order. The forest canopy constituents (branches, leaves, stems, and trunks) are embedded in a multi-layered medium over a rough interface. The branches, stems, and trunks are modeled...

In minimum mean square estimation, an estimate /spl theta/' of the random parameter vector /spl theta/ is obtained from an input vector y. We develop bounds on the variances of elements of /spl theta/'-/spl theta/ for the case where input signal vector y and the parameter vector /spl theta/ are non-Gaussian. First, we use linear transformations to...

In modeling of electromagnetic (EM) interaction with terrain one must first examine the geometry of the scatterers relative to the incident wavelength and the electromagnetic properties of the terrain in the frequency region of interest. The purpose of this study is to examine the similarities and differences in developing scattering models for soi...

We performed experiments to collect radar backscatter data at Ku (13.4GHz) and C bands (5.3GHz) over simulated sea ice at the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) during the 1990 and 1992 winter seasons. These experiments were conducted over bare saline ice grown in an indoor tank and an outdoor pond facility. The rada...

The objective of the study is to examine the ease of applicability of three scattering models. This is done by considering the time taken to numerically evaluate these models and comparing their predictions as a function of surface roughness, frequency, incident angle and polarization with the moment method solution in two dimensions. In addition,...

Presents some results of a study carried out in the MTV (Monitoring of the Tropical Vegetation) unit of the Institute for Remote Sensing Applications at the JRC Ispra in the context of the TREES project (Tropical Ecosystem Environment observations by Satellites). The goal of the study is to reach a physical interpretation of the observed time and s...

Several recent developments in nonlinear estimators (e.g. more efficient training algorithms for neural networks) have made it possible to apply them to remote sensing and its associated highly nonlinear mappings between the observation space (Rⁿ) and the parameter space (R^m). One common problem estimators encountering nonline...

Neural networks (NN) are rapidly gaining acceptance within many disciplines including remote sensing. This is due primarily to the use of more efficient training algorithms and better understanding of their capabilities and limitations. NNs have been found to be robust and well suited for the wide variety of data found in remote sensing. They are u...

The neural network learning process is to adjust the network weights to adapt the selected training data. Based on the polynomial basis function (PBF) modeled neural network that is a modified multilayer perceptrons (MLP) network, a dynamic learning algorithm (DL) is proposed. The presented learning algorithm makes use of the Kalman filtering techn...

Randomly rough surface patches in three dimensions are generated on the computer. The FD-TD method is used to compute scattering from surface patches by converting the Maxwell's equations into difference equations using a central difference approximation for the space and time derivatives. The volume of grids above the rough surface is divided into...

Many environmental features such as sea ice, snow, and soils can be considered to be dense media. In order to better understand the microwave scattering mechanisms involved in such media, synthetic targets simulating certain electrical behaviors are created. These targets are composed of lead-glass spheres imbedded in polystyrene sheets. The locati...

Radar scattering measurements of saline ice at 5.3 and 13.4 GHz were collected during the 1990 and 1992 winter seasons at the US Army Cold Regions Research and Engineering Laboratory (CRREL). Both like and cross polarizations were obtained from saline ice with and with out snow cover. The results of these measurements were examined with a radiative...

An examination of soil particles from very fine to medium sand surfaces has indicated that they are generally on the order of 50 to 500 microns. Thus, at an incident wavelength around 0.6 micron, the incident light should “see” microscopic roughness features on the particle rather than its macroscopic features. It is anticipated that the macroscopi...

Three-dimensional randomly rough surface patches with a Gaussian correlation function and height distribution are generated on the computer. An FDTD algorithm with scattered field formulation is used to compute scattering from surface patches by numerically solving Maxwell's equations for the scattered field using a central difference approximation...

A multisensor approach is being developed at the University of Texas at Arlington (UTA) to improve upon current capabilities in environmental monitoring. The sensors consist of an FIR for operation in the near to thermal infrared regions of the spectrum, a long-path UV (LPUV) spectrometer, and an active/passive millimeter-wave (MMW) spectrometer th...

The classification of remote sensing data has been a topic of interest since the early 70s. Recent studies have demonstrated that neural networks can be effective when used as a classifier of remote sensing data. One problem encountered using neural networks, though, is the time required to train the networks. This amount of time is directly relate...

Based on the matrix doubling method, a sea ice scattering model which accounts for the effects of vertical structural variation is developed. The sea ice layer is modeled as many sublayers with different physical characteristic determined by the vertical structural variation profile. Each sublayer is assumed to be statistically homogeneous. In addi...

In this final report, we summarize the approach used and relevant information for simulation of radar signal statistics from randomly rough surfaces. The total number of cases to be performed in this contract is 60 and is depicted in Table 1. Two sets of cases reported in the past are: (1) 30 cases for receiver orientation angles of 135 degrees, fi...

The fractional volume dependence of the extinction rate in dense media is studied. Results from optical scattering experiments are compared with the theoretical extinction rate calculated by independent-scattering theory and the quasi-crystalline approximation (QCA). QCA takes into account the coherent interaction among scatterers in the vicinity o...

A new objective function for functional link net classifier design is presented, which has more free parameters than the classical objective function. An iterative minimization technique for the objective function is described which requires the solution of multiple sets of numerically ill conditioned linear equations. A numerically stable solution...

Fast training algorithms are presented for the training of neural networks used for inversion and classification problems. The algorithms build upon a previously described technique in which linear equations are solved for the network's output weights. First, the method is motivated by an analysis of the multilayer perceptron, based on polynomial b...

In the past, the phase function used in the radiative transfer model has been derived for a single scatterer. Then, scattering computation is done based on intensity scattering, thus ignoring phase interference effects between adjacent scatterers. To overcome this difficulty we derive a phase function using the T‐matrix approach. First, the scatter...

The T-matrix approach is applied to formulate electromagnetic scattering from an arbitrary number of spheres due to an incident plane wave. The representation of an incident plane wave in spherical vector wave functions from an arbitrary incident direction is given to facilitate subsequent derivation. The T-matrix formulation for an arbitrary numbe...

A randomly rough surface with Gaussian height distribution and a Gaussian correlation function was manufactured as a good conducting mold to generate a thin ice layer with the same surface geometry. This ice layer was superimposed on a thick smooth saline ice with known salinity property to form a saline ice medium with a known air-ice roughness ch...

A technique for improving the topology of a trained neural network, used for an inversion or classification problem, is presented. The technique models the multilayer perceptron as a power series, which allows us to (1) remove units from the network which are well-approximated by zero-degree or first-degree polynomials, (2) measure the effect of re...

A new objective function for neural net classifier design is presented, which has more free parameters than the classical objective function. An iterative minimization technique for the objective function is derived which requires the solution of multiple sets of numerically ill-conditioned linear equations. A numerically stable solution to the neu...

Uses a neural network method for obtaining a stochastic Cramer-Rao bound on estimates, given only the training data. The Cramer-Rao bounds can be used (1) to help determine when neural net training should be stopped, (2) to re-order the network inputs according to their contributions to the bounds, and (3) to eliminate less useful inputs. The conve...

Surface bispectrum are obtained from a computer generated skewed surface profile based on a narrow band representation of a nonlinear surface model. Then basic properties are analyzed and summarized. Consistent with the definition and properties of the bispectrum, a Gaussian and two exponential decay functions are tested as possible representations...

The statistics of radar signals returned from forest components are investigated through a simulation study based on a first-order scattering theory. A forest canopy is modeled as a volume of needle-shaped or disc-shaped leaves and finite-length, cylindrical branches. It is expected that at radar frequencies above X band, scattering away from norma...

A model based on the radiative transfer formulation has been modified to account for the effects of the terrain slope on the total backscattering return from a forest canopy. To the first-order, the forested area may be modeled as a plane parallel forest but over a slanted ground plane. Thus the phase matrix for the volume scattering from any fores...

Numerical results are presented to improve understanding of the observed correlation of radar backscatter with canopy biomass in forests. The calculations employ a model developed by Karam el which is based on the solution of the vector radiative transfer equations and operates over a wide range of frequencies. The simulations use data collected ov...