Uniform Theory Of Diffraction-physical Optics Research Articles

Plane-wave UTD-PO formulation for multiple-plateau diffraction analysis assuming negative incidence angles

We present a detailed methodology for investigating radiowave multiple diffraction events over rectangular barriers (here termed plateaus) when exposed to a plane wave originating from a low-lying source. Based on Babinet’s principle, our approach uses the combined uniform theory of diffraction-physical optics (UTD-PO), and is validated via 60 GHz measurements performed on a scaled replica of the setting under investigation. As an additional validation, theoretical results at 2 GHz of the corresponding spherical-wave solution converge with those of the presented plane-wave formulation with expanding distance between the source and the first obstacle. The proposed method has a crucial advantage in that it solely considers single diffractions via recursion, thus precluding the need for the diffraction coefficients to include higher order diffraction terms. The work’s findings and insights are salient for mobile communication system design in settings where the adjacent rectangular structures are higher than the transmitting antenna.

UTD-PO Solution for E-Plane Radiation Pattern Calculation of Rectangular Horn Antennas With Rectangular-Shaped Corrugations

Proposing a novel hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation, we develop a method to calculate the E-plane radiation pattern of corrugated E-plane rectangular horn antennas with rectangular corrugations. We derive the technique from the estimation of the total field that reaches the emitting source (a magnetic current line), thereby assuming the impingement of a plane wave above the horn (reciprocity is applied). To validate our method, we compare the performance of the UTD-PO analysis with that of the electric field integral equation (EFIE) solved using the method of moments (MoM). Our method shows improved computational efficiency over EFIE and other numerical techniques that fully discretize the geometry.

A New Solution Based on UTD-PO Method for Multiple-Diffraction by a Series of Buildings with Irregular Height and Spacing

A new solution based on the uniform theory of diffraction-physical optics (UTD-PO) method is presented for the prediction of multiple diffractions caused by a series of buildings with irregular height and interspacing. The prediction results, obtained using the proposed solution, are compared with the available measurement data and results based on UTD slope-diffraction method to validate the accuracy. Further, the computational complexity of the proposed algorithm is compared with that of the available UTD slope-diffraction method to demonstrate its computational efficiency.

UTD-PO Formulation for the Analysis of Multiple-Plateau Diffraction When Considering Illumination From a Low Source

A hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of the multiple-diffraction (MD) that takes place over rectangular-shaped obstacles (plateaus) when the latter are illuminated from a low source is presented. The solution, which is based on Babinet's principle, has been validated with measurements taken at 60 GHz on a scaled model of the environment under study and with additional measurements performed by other authors. Moreover, the proposed approach has been compared with the wide-angle Fourier split-step parabolic equation method, with the UTD-PO formulation showing better accuracy against the experimental data, especially when the distance between the transmitter and the receiver is increased. Furthermore, the main advantage of the proposed solution is that due to recursion, the calculations imply only single diffractions, thereby avoiding the need of higher order diffraction terms in the diffraction coefficients. The results and findings of this communication are particularly applicable to the planning of microcellular mobile communication systems when the transmitting antenna is located below the height of the surrounding buildings.

On the Influence of Diffuse Scattering on Multiple-Plateau Diffraction Analysis at mm-Wave Frequencies

A study of the impact of the diffuse scattering phenomenon when calculating radio wave multiple-plateau diffraction losses at millimeter-wave (mm-wave) frequencies is hereby presented. In this sense, measurements of the total attenuation caused by a series of either rough or polished brick blocks are properly compared with the theoretical multiple-diffraction losses of an array of ideally smooth brick blocks predicted by a hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation. The results show the influence of diffuse scattering phenomena when it comes to calculating radio wave multiple-plateau diffraction attenuation and can be applied to the obtaining of more realistic mm-wave propagation models when multiple diffraction over rectangular obstacles with irregular (rough) surfaces has to be considered.

Validation with measurements of plane and spherical-wave UTD-PO propagation models which assume flat-topped obstacles

Two radiowave propagation models which calculate the multiple-building diffraction losses through the corresponding Uniform Theory of Diffraction-Physical Optics (UTD-PO) formulations are validated with measurements performed in different locations of an urban environment. The main advantage of such solutions is that, since they are recursive, the calculations are expressed in terms of single diffractions (high-order diffraction terms are not considered in the diffraction coefficients), thus showing better computational efficiency than other existing methods. Buildings are modeled as flat-topped obstacles and one formulation assumes plane-wave incidence over the obstacles while the other considers a spherical wave impinging over the array of rooftops. The locations in which the spherical-wave model should be used instead of the plane-wave method in order to obtain more realistic results are discussed.

On the impact of the type of wave incidence in multiple-cylinder diffraction analysis at millimeter-wave frequencies

A comparison of plane against spherical-wave incidence consideration in multiple-cylinder diffraction analysis is performed, at several millimeter-wave frequencies, in order to clarify the margin in which both incidence results converge or differ. The mentioned comparison is carried out through a pair of two-dimensional (2D) hybrid uniform theory of diffraction-physical optics (UTD-PO) solutions (the plane-wave formulation for cylinders is firstly proposed in this work), and is intended to show the validity of each wave-incidence assumption in environments where millimeter or sub-millimeter-wave bands are being employed. In this sense, results can be used to achieve a more accurate and realistic planning of such radio communication systems when multiple-diffraction over rounded obstacles has to be considered (e.g. communication systems operating in stadiums).

UTD-PO Radiation Pattern Analysis of Rectangular Horn Antennas With Cylindrical Corrugations

The calculation of the E-plane radiation pattern of corrugated E-plane rectangular horn antennas in which the corrugations have a cylindrical shape is hereby performed through a method based on a hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation. The proposed method is successfully validated through comparison with the application of an electric field integral equation (EFIE) solved by the method of moments (MoM), with the UTD-PO analysis showing more computational efficiency than the EFIE and other numerical techniques based on the full discretization of the geometry. On the other hand, the use of cylindrical corrugations instead of the traditional rectangular-shaped corrugations is analyzed and, in view of the results, the former may offer a series of advantages in comparison to the latter, such as narrower main lobes as well as better fabrication-related aspects.

UTD-PO Solution for Estimating the Propagation Loss due to the Diffraction at the Top of a Rectangular Obstacle When Illuminated From a Low Source

A new method based on a hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of the propagation loss due to the diffraction that takes place at the top of a rectangular obstacle that is illuminated from a low source (i.e., the transmitter height is smaller than the obstacle height) is presented. The receiver is considered to be located at the shadow boundary of the second wedge of the plateau so that the solution is valid to estimate the mentioned diffraction loss in order to be incorporated into more general propagation models. In such models, for example, both the free space losses and the typical urban final diffraction loss down to street level (occurring at the receiving point due to an eventual final diffracting obstacle) will be considered. In this sense, it should be noted that the proposed formulation is not a general formalism to estimate radiowave propagation over plateaux (as the receiver is not arbitrarily located). The method, which is mathematically less complex than existing techniques, applies Babinet's principle, and is validated through the solid agreement obtained with measurements at 60 GHz and the comparison with a method which is based on the evaluation of a Fresnel surface integral.

Comparison of a UTD-PO Formulation for Multiple-Plateau Diffraction With Measurements at 62 GHz

A hybrid uniform theory of diffraction-physical optics (UTD-PO) formulation for the analysis of multiple-diffraction of spherical waves by a series of rectangular plateaux is compared with measurements performed at 62 GHz. The comparison shows a solid agreement between predicted and measured results. Therefore, since the array of plateaux under investigation can be considered as a scaled-model of an urban environment, the results support the validity of the proposed UTD-PO formulation in the analysis of urban radiowave propagation.

E‐plane radiation pattern analysis of rectangular horn antennas with V‐shaped corrugations by UTD‐PO formulation

A new method for the calculation of the radiation pattern of corrugated E‐plane rectangular horn antennas based on a hybrid uniform theory of diffraction‐physical optics (UTD‐PO) formulation is presented. The method, which allows for the analysis of horns in which V‐shaped corrugations have been considered, has been validated with numerical data obtained through the application of both an electric field integral equation (EFIE) solved by the method of moments (MoM) and the finite element method (FEM)‐based full‐wave electromagnetic analysis software, HFSS. In this sense, the proposed solution is mathematically less complex and computationally more efficient than existing techniques.

TD solution based on UTD-PO for multiple-building diffraction with shadowing caused by a wedge-shaped hill for UWB signals

A time domain (TD) solution based on uniform theory of diffraction-physical optics (UTD-PO) is presented to analyze the multiple-building diffraction in urban areas where a wedge-shaped hill causes shadowing of the transmitter from the receiver.We derive the channel impulse response of the renowned Bertoni's model, which utilizes a recursion relation and does not need to incorporate the slope diffraction in the transition zone. The received signals can be predicted through a simple operation of convolution, which provides a faster and easier final solution for UWB radio propagation and significantly reduces the computational time. The TD result can be applied to analyze the UWB pulse distortion by multiple-building diffraction in urban areas where the city is surrounded by hilly areas. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:426–429, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25730

Time-Domain UTD-PO Analysis of a UWB Pulse Distortion by Multiple-Building Diffraction

A time domain (TD) solution based on uniform theory of diffraction-physical optics (UTD-PO) is presented to analyze the multiple-building diffraction in urban areas. Buildings are supposed to have rectangular cross sections, and the spherical-wave incidence is considered due to the fact that it is more appropriate than the plane-wave incidence approximation to analyze the waveform distortion in terms of pulse shape in this case. Since the solution utilizes a recursion relation, the slope diffraction in transition zone is avoided, which provides a faster and easier final solution and significantly reduces the computational time. The TD result can be applied to analyze multiple-building diffraction in urban areas.

UTD-PO Formulation for the Multiple-Diffraction of Spherical Waves by an Array of Multimodeled Obstacles

A hybrid uniform theory of diffraction-physical optics (UTD-PO) solution for the analysis of the multiple-diffraction of spherical waves caused by an array of obstacles, which have been modeled by different shapes, is hereby presented. The formulation, validated with measurements from technical literature, does not need to incorporate high-order diffraction terms (slope diffraction) thanks to a recursive relation, therefore producing an easier, faster solution-when compared with other methods-that, at the same time, achieves accurate results. Such results can be applied in radiowave propagation analysis when multiple-diffraction over obstacles with quite different shapes has to be considered.

Comparison of spherical against plane-wave incidence assumption in prediction of over-rooftop multiple-building diffraction

This work presents a comparison between multiple-building forward diffraction loss predicted in urban areas when considering a plane-wave incidence over the rooftops, and when assuming the wavefront impinging on the array of buildings to be spherical. The mentioned comparison is carried out through two hybrid uniform theory of diffraction-physical optics (UTD-PO) solutions, and is intended to clarify the validity of each assumption in a typical urban environment. Results can be used to achieve a more accurate and realistic planning of radio communication systems.