Ben A. Munk

Bio: Ben A. Munk is an academic researcher from Ohio State University. The author has contributed to research in topics: Dipole antenna & Radome. The author has an hindex of 22, co-authored 44 publications receiving 5646 citations.

Frequency Selective Surfaces: Theory and Design

Abstract: General Overview. Element Types: A Comparison. Evaluating Periodic Structures: An Overview. Spectral Expansion of One- and Two-Dimensional Periodic Structures. Dipole Arrays in a Stratified Medium. Slot Arrays in a Stratified Medium. Band-Pass Filter Designs: The Hybrid Radome. Band-Stop and Dichroic Filter Designs. Jaumann and Circuit Analog Absorbers. Power Handling of Periodic Surfaces. Concluding Remarks and Future Trends. Appendices. References. Index.

Finite antenna arrays and FSS

Abstract: Foreword. Preface. Acknowledgments. Symbols and Definitions. 1. Introduction. 1.1 Why Consider Finite Arrays? 1.2 Surface Waves Unique to Finite Periodic Structures. 1.3 Effects of Surface Waves. 1.4 How Do We Control the Surface Waves? 1.5 Common Misconceptions. 1.6 Conclusion. 1.7 Problems. 2. On the RCS of Arrays. 2.1 Introduction. 2.2 Fundamentals of Antenna RCS. 2.3 How to Obtain a Low sigmatot by Cancellation (Not Recommended). 2.4 How Do We Obtain Low sigmatot Over a Broad Band? 2.5 A Little History. 2.6 On the RCS of Arrays. 2.7 An Alternative Approach: The Equivalent Circuit. 2.8 On the Radiation from Infinite vs. Finite Arrays. 2.9 On Transmitting, Receiving and Scattering Radiation Pattern of Finite Arrays. 2.10 Minimum versus Non-Minimum Scattering Antennas. 2.11 Other Non-Minimum Scattering Antennas. 2.12. How to Prevent Coupling Between the Elements Through the Feed Network. 2.12 How to Eliminate Backscatter Due to Tapered Aperture Illumination. 2.13 Common Misconceptions. 2.15 Summary. 2.16 Problems. 3. Theory. 3.1 Introduction. 3.2 The Vector Potential and the H-Field for Column Arrays of Hertzian Elements. 3.3 Case I: Longitudinal Elements. 3.4 Case II: Transverse Elements. 3.5 Discussion. 3.6 Determination of the Element Currents. 3.7 The Double Infinite Arrays with Arbitrary Element Orientation. 3.8 Conclusions. 3.9 Problems. 4. Surface on Passive Surfaces of Finite Extent. 4.1 Introduction. 4.2 Model. 4.3 The Infinite Array Case. 4.4 The Finite Array Case Excited by Generators. 4.5 The Element Currents on a Finite Array Excited by an Incident Wave. 4.6 How the Surface Waves are Excited on a Finite Array. 4.7 How to Obtain the Actual Current Components. 4.8 The Bistatic Scattered Field from a Finite Array. 4.9 Parametric Study. 4.10 How to Control Surface Waves. 4.11 Finite Tuning the Load Resistors at a Single Frequency. 4.12 Variation with Angle of Incidence. 4.13 The Bistatic Scattered Field. 4.14 Previous Work. 4.15 On Scattering from Faceted Radomes. 4.16 Effects of Discontinuities in the Panels. 4.17 Scanning in the E-plane. 4.18 Effect of a Groundplane. 4.19 Common Misconceptions Concerning Element Currents on Finite Arrays. 4.20 Conclusion. 4.21 Problems. 5. Finite Active Arrays. 5.1 Introduction. 5.2 Modeling of a Finite x Infinite Groundplane. 5.3 Finite x Infinite Array with an FSS Groundplane. 5.4 Micro Management of the Backscattered Field. 5.5 The Model for Studying Surface Waves. 5.6 Controlling Surface Waves on Finite FSS Groundplanes. 5.7 Controlling Surface Waves on Finite Arrays of Active Elements with FSS Groundplane. 5.8 The Backscatterd Fields from the Triads in a Large Array. 5.9 On the Bistatic Scattered Field from a Large Array. 5.10 Further Reduction: Broadband Matching. 5.11 Common Misconceptions. 5.12 Conclusion. 5.13 Problems. 6. Broadband Wire Arrays. 6.1 Introduction. 6.2 The Equivalent Circuit. 6.3 An Array with Groundplane and No Dielectric. 6.4 Practical Layouts of Closely Spaced Dipole Arrays. 6.5 Combination of the Impedance Components. 6.6 How to Obtain Grater Braodwidth. 6.7 Array with a Groundplane and a Single Dielectric Slab. 6.8 Actual Calculated Case: Array with Groundplane and Single Dielectric Slab. 6.9 Array with Groundplane and Two Dielectric Slab. 6.10 Comparison Between the Single and Double Slab Array. 6.11 Calculated Scan Impedance for Array with Groundplane and Two Dielectric Slabs. 6.12 Common Misconceptions. 6.13 Conclusions. 7. An Omnidirectional Antenna with Low RCS. 7.1 Introduction. 7.2 The Concept. 7.3 How Do We Feed the Elements? 7.4 Calculated Scattering Pattern for Omnidirectional Antenna with Low RCS. 7.5 Measured Backscatter from a Low RCS Omnidirectional Antenna. 7.6 Common Misconceptions. 7.7 Conclusions and Recommendations. 8. The RCS of Two-Dimensional Parabolic Antennas. 8.1 The Major Scattering Components. 8.2 Total Scattering from a Parabolic Reflector with a Typical Feed. 8.3 Practical Execution of the Low RCS Feed. 8.4 Out of Band Reduction. 8.5 Common Misconceptions on Edge Currents. 8.6 Conclusion. 9. Aperiodicity: Is it a Good Idea? 9.1 Introduction. 9.2 General Analysis of Periodic Structures with Perturbation of Element Loads and/or Inter-element Spacings. 9.3 Perturbation of Arrays of Tripoles. 9.4 Making Use of Our Observations. 9.5 Anomalies due to Insufficient Number of Models. 9.6 Aperiodicity on Finite Arrays. 9.7 Conclusions. 10. Summary and Final Remarks. 10.1 Summary. 10.2 Are We Going in the Right Direction? 10.3 Let Use Make Up! Appendix A. Determination of Transformation and Position Circles. Appendix B. Broadband Matching. Appendix C. Meander-Line Polarizers for Oblique Incidence. Appendix D. On the Scan versus the Embedded Impedance. References. Index.

On Designing Jaumann and Circuit Analog Absorbers (CA Absorbers) for Oblique Angle of Incidence

Abstract: Most investigations of Jaumann and circuit analog absorbers (CA absorbers) consider normal angle of incidence only. This paper expands our investigation to also include oblique angle of incidence as well as arbitrary polarization. Essentially two problems are encountered for oblique angle of incidence: An upward shift of the center frequency; and a mismatch that, in general, will vary with angle of incidence of the incident field. The new contribution given in this paper is that it considers ways to combat both of these dilemmas. Finally, comparison will be made with similar designs obtained by the genetic algorithm (GA) approach. It will be observed that the analytic approach, as used in this paper, in general leads to designs that are not only superior to the GA designs but also simpler, at least in the present case

A low-profile broadband phased array antenna

Abstract: A fundamentally different approach to broadband array design is introduced and validated with measured data. This design approach relies on mutual coupling to increase array bandwidth as opposed to the conventional approach of attempting to minimize coupling between array elements designed in isolation. The design leverages from multi-layer FSS design, resulting in a broadband, low profile, highly efficient, conformal array.

Reflection properties of periodic surfaces of loaded dipoles

Abstract: Two-dimensional periodic arrays of dipoles or slots act as reflecting or transmitting surfaces, respectively, which have bandpass filter characteristics. The resonant frequency and the bandwidth may be controlled by varying the length, spacing, and load impedance of the dipoles (slots). A theoretical and experimental investigation of the scattering by a two-dimensional array of loaded dipoles is described. The scattering through the resonance region shows that a unit reflection coefficient is achieved. The effect of grating-lobe radiation is included. The scattering properties as a function of the angle of incidence are given for both loaded and unloaded dipoles. The loaded dipole array described in this paper produces a narrower bandwidth than the array of unloaded dipoles, and the resonant frequency is much less dependent on the angle of incidence. The resonant frequency of the array as well as the bandwidth depends strongly on the resonant frequency of the dipole element as would be expected; however, it is also substantially influenced by the interelement spacing and the angle of incidence.

Perfect metamaterial absorber.

Abstract: We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz.

Flat Optics With Designer Metasurfaces

Abstract: Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

Terahertz Metamaterials for Linear Polarization Conversion and Anomalous Refraction

Abstract: Polarization is one of the basic properties of electromagnetic waves conveying valuable information in signal transmission and sensitive measurements. Conventional methods for advanced polarization control impose demanding requirements on material properties and attain only limited performance. We demonstrated ultrathin, broadband, and highly efficient metamaterial-based terahertz polarization converters that are capable of rotating a linear polarization state into its orthogonal one. On the basis of these results, we created metamaterial structures capable of realizing near-perfect anomalous refraction. Our work opens new opportunities for creating high-performance photonic devices and enables emergent metamaterial functionalities for applications in the technologically difficult terahertz-frequency regime.

A review of metasurfaces: physics and applications.

Abstract: Metamaterials are composed of periodic subwavelength metal/dielectric structures that resonantly couple to the electric and/or magnetic components of the incident electromagnetic fields, exhibiting properties that are not found in nature. This class of micro- and nano-structured artificial media have attracted great interest during the past 15 years and yielded ground-breaking electromagnetic and photonic phenomena. However, the high losses and strong dispersion associated with the resonant responses and the use of metallic structures, as well as the difficulty in fabricating the micro- and nanoscale 3D structures, have hindered practical applications of metamaterials. Planar metamaterials with subwavelength thickness, or metasurfaces, consisting of single-layer or few-layer stacks of planar structures, can be readily fabricated using lithography and nanoprinting methods, and the ultrathin thickness in the wave propagation direction can greatly suppress the undesirable losses. Metasurfaces enable a spatially varying optical response (e.g. scattering amplitude, phase, and polarization), mold optical wavefronts into shapes that can be designed at will, and facilitate the integration of functional materials to accomplish active control and greatly enhanced nonlinear response. This paper reviews recent progress in the physics of metasurfaces operating at wavelengths ranging from microwave to visible. We provide an overview of key metasurface concepts such as anomalous reflection and refraction, and introduce metasurfaces based on the Pancharatnam-Berry phase and Huygens' metasurfaces, as well as their use in wavefront shaping and beam forming applications, followed by a discussion of polarization conversion in few-layer metasurfaces and their related properties. An overview of dielectric metasurfaces reveals their ability to realize unique functionalities coupled with Mie resonances and their low ohmic losses. We also describe metasurfaces for wave guidance and radiation control, as well as active and nonlinear metasurfaces. Finally, we conclude by providing our opinions of opportunities and challenges in this rapidly developing research field.

Metamaterial Electromagnetic Wave Absorbers

Abstract: The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch–the metamaterial perfect absorber (MPA)–has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed.