A antenna array ( 20 ) includes a plurality of periodic or aperiodic arranged sub-arrays ( 22 ). Each sub-array ( 22 ) includes a plurality of antenna elements ( 32 ) arranged in the form of a spiral ( 30 ). The sub-arrays ( 22 ) can comprise various spiral shapes to provide the required physical configuration and operational parameters to the antenna array ( 20 ). The elements ( 32 ) of each sub-array ( 22 ) are arranged to minimize the number of such elements ( 32 ) that intersect imaginary planes perpendicular to the spiral and passing through the spiral center. Such an orientation of the elements ( 32 ) minimizes grating lobes in the antenna pattern.

Antenna arrays formed of spiral sub-array lattices

Preface. Acknowledgments. Chapter 1: Introduction. 1.1 Numerical Simulation of Antennas. 1.2 Finite Element Analysis vs. Other Numerical Methods. 1.3 Frequency- vs. Time-Domain Simulations. 1.4 Brief Review of Past Work. 1.5 Overview of This Book. References. Chapter 2: Finite Element Formulation. 2.1 Finite Element Formulation in the Frequency Domain. 2.2 Finite Element Formulation in the Time Domain. 2.3 Modeling of Complex Materials. 2.3.1 Modeling of Electrically and Magnetically Lossy Materials. 2.3.2 Modeling of Electrically Dispersive Materials. 2.3.3 Modeling of Magnetically Dispersive Materials. 2.3.4 Modeling of Doubly Dispersive Lossy Materials. 2.4 Solution of the Finite Element Equations. 2.5 Higher-Order and Curvilinear Finite Elements. 2.6 Summary. References. Chapter 3: Finite Element Mesh Truncation. 3.1 Absorbing Boundary Conditions. 3.1.1 First-Order Absorbing Boundary Condition. 3.1.2 Second-Order Absorbing Boundary Condition. 3.2 Perfectly Matched Layers. 3.2.1 PML in Terms of Stretched Coordinates. 3.2.2 PML as an Anisotropic Material Absorber. 3.2.3 PML for Truncating Computational Domain. 3.2.4 Finite Element Implementation of PML. 3.2.5 ABC-Backed, Complementary, CFS, and Second-Order PMLs. 3.3 Boundary Integral Equations. 3.3.1 Frequency-Domain Formulations. 3.3.2 Time-Domain Formulations. 3.3.3 Treatment of Infinite Ground Plane. 3.4 Summary. References. Chapter 4: Hybrid FETD-FDTD Technique. 4.1 The FDTD Method. 4.2 PML Implementation in FDTD. 4.2.1 FDTD Stretched-Coordinate PML. 4.2.2 FDTD Anisotropic PML. 4.3 Near-to-Far-Field Transformation in FDTD. 4.4 Alternative FETD Formulation. 4.5 Equivalence between FETD and FDTD. 4.6 Stable FETD-FDTD Interface. 4.6.1 Initial Approaches. 4.6.2 Stable Formulation. 4.7 Building Hybrid Meshes. 4.8 Wave-Equation Stablization. 4.9 Validation Examples. 4.10 Summary. References. Chapter 5: Antenna Source Modeling and Parameter Calculation. 5.1 Antenna Feed Modeling. 5.1.1 Current Probe. 5.1.2 Voltage Gap Generator. 5.1.3 Waveguide Feed Model. 5.2 Plane-Wave Excitation. 5.2.1 Total-Field Formulation. 5.2.2 Scattered-Field Formulation. 5.2.3 Total- and Scattered-Field Decomposition Approach . 5.3 Far-Field Pattern Computation. 5.4 Near-Field Visualization. 5.5 Summary. References. Chapter 6: Modeling of Complex Structures. 6.1 Thin Material Layers and Sheets. 6.1.1 Impedance Boundary Conditions. 6.1.2 Shell Element Formulation. 6.2 Thin Wires and Slots. 6.2.1 Thin Wires. 6.2.2 Thin Slots. 6.3 Lumped Circuit Elements. 6.3.1 Coupled First-Order Equations. 6.3.2 Wave Equation. 6.3.3 Example. 6.4 Distributed Feed Network. 6.5 System-Level Coupling Example. 6.5.1 Internal Dispersive Material Calibration. 6.5.2 External Illumination and Aperture Coupling. 6.6 Summary. References. Chapter 7: Antenna Simulation Examples. 7.1 Narrowband Antennas. 7.1.1 Coaxial-fed Monopole Antenna. 7.1.2 Monopole Antennas on a Plate. 7.1.3 Patch Antennas on a Plate. 7.1.4 Conformal Patch Antenna Array. 7.2 Broadband Antennas. 7.2.1 Ridged Horn Antenna. 7.2.2 Sinuous Antenna. 7.2.3 Logarithmic Spiral Antenna. 7.2.4 Inverted Conical Spiral Antenna. 7.2.5 Antipodal Vivaldi Antenna. 7.2.6 Vlasov Antenna. 7.3 Antenna RCS Simulations. 7.3.1 Microstrip Patch Antenna. 7.3.2 Standard Gain Horn Antenna. 7.4 Summary. References. Chapter 8: Axisymmetric Antenna Modeling. 8.1 Method of Analysis. 8.1.1 Finite Element Formulation. 8.1.2 Mesh Truncation Using Perfectly Matched Layers. 8.1.3 Mesh Truncation Using Boundary Integral Equations. 8.2 Application Examples. 8.2.1 Luneburg Lens. 8.2.2 Corrugated Horn. 8.2.3 Current Loop Inside a Radome. 8.3 Summary. References. Chapter 9: Infinite Phased Array Modeling. 9.1 Frequency-Domain Modeling. 9.1.1 Periodic Boundary Conditions. 9.1.2 Mesh Truncation Techniques. 9.1.3 Extension to Skew Arrays. 9.1.4 Extension to Scattering Analysis. 9.1.5 Application Examples. 9.2 Time-Domain Modeling. 9.2.1 Transformed Field Variable. 9.2.2 Mesh Truncation Techniques. 9.2.3 General Material Modeling. 9.2.4 Application Examples. 9.3 Approximation to Finite Arrays. 9.4 Summary. References. Chapter 10: Finite Phased Array Modeling. 10.1 Frequency-Domain Modeling. 10.1.1 The FETI-DPEM1 Formulation. 10.1.2 The FETI-DPEM2 Formulation. 10.1.3 Nonconforming Domain Decomposition. 10.1.4 Application Examples. 10.2 Time-Domain Modeling. 10.2.1 The Dual-Field Domain Decomposition Method. 10.2.2 Domain Decomposition for Iterative Solutions. 10.2.3 Application Examples. 10.3 Summary. References. Chapter 11: Antenna-Platform Interaction Modeling. 11.1 Coupled Analysis. 11.1.1 FETI-DPEM with Domain Decomposition. 11.1.2 Hybrid FETD-FDTD with Domain Decomposition. 11.1.3 Hybrid FE-BI Method with FMM Acceleration. 11.2 Decoupled Analysis. 11.2.1 Near-Field Calculation. 11.2.2 Far-Field Evaluation by Numerical Methods. 11.2.3 Far-Field Evaluation by Asymptotic Techniques. 11.2.4 Direct and Iterative Improvements. 11.3 Summary. References. Chapter 12: Numerical and Practical Considerations. 12.1 Choice of Simulation Technologies. 12.2 Frequency- vs. Time-Domain Simulation Tools. 12.3 Fast Frequency Sweep. 12.4 Numerical Convergence. 12.5 Domain Decomposition and Parallel Computing. 12.6 Verification and Validation of Predictions. 12.7 Summary. References. Index.

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Finite Element Analysis of Antennas and Arrays

Power is fed from a feeding coil L2 to a receiving coil L3 by magnetic resonance. A VCO 202 alternately turns ON/OFF switching transistors Q1 and Q2 at a drive frequency fo, whereby AC power is fed to the feeding coil L2, and then the AC power is fed from the feeding coil L2 to the receiving coil L3. A phase detection circuit 114 detects a phase difference between the current phase and voltage phase, and the VCO 202 adjusts the drive frequency fo such that the phase difference becomes zero. When load voltage is changed, the detected current phase value is adjusted with the result that the drive frequency fo is adjusted.

Wireless power feeder, wireless power receiver, and wireless power transmission system

An antenna device includes a substrate, and a radiating element disposed on the substrate. The radiating element has two spiral arms unfurling in an Archimedean progression and terminating in a logarithmic progression. The substrate is formed from a dielectric material and includes multiple perforations for providing passage of coolant through the substrate. The radiating element is disposed on a front surface of the substrate, and an enclosure is formed on a rear surface of the substrate to provide a reflective cavity for reflecting radiation to the front surface of the substrate. The enclosure includes a hexagonal perimeter formed by a wall. The antenna device may be used as an element in a planar phased array.

Compact high-power reflective-cavity backed spiral antenna

This communication presents a single-feed ultra-wideband circularly polarized (CP) antenna with high front-to-back ratio (FBR). The antenna is composed of two orthogonally placed elliptical dipoles printed on both sides of a substrate. To realize high FBR, a novel composite cavity is also proposed and integrated with the presented crossed dipoles, which effectively reduces the backlobe of the crossed dipoles. Simulation results are in good agreement with the measured results that demonstrate an impedance bandwidth from 0.9 to 2.95 GHz (106.5%) and a 3-dB axial ratio (AR) bandwidth from 1 to 2.87 GHz (96.6%). The measured FBR is about 30 dB across the whole global navigation satellite system (GNSS) band. Compared with other reported single-feed wideband CP antennas, the antenna has advantages such as a wider CP bandwidth and lower backlobe radiation.

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Single-Feed Ultra-Wideband Circularly Polarized Antenna With Enhanced Front-to-Back Ratio

When compared to printed cavity-backed spirals, slot spiral antennas offer the possibility of designs that are conformal and very thin. We discuss the physical characteristics of a cavity-backed slot spiral, as well as the associated infinite balun and termination designs. Simulations of the proposed cavity-backed spiral are presented and used to optimize the antenna's various parameters. Comparisons of measurements and calculations are also given, to validate the gain and axial-ratio computations. Several options for miniaturizing this design, using capacitive and inductive loadings, are also presented.

Slot spiral antenna

A new planar, wideband feed for a slot spiral antenna is presented and tested at VHF frequencies. Radiation pattern measurements are presented to demonstrate the performance and usefulness of this feed. In contrast to most traditional printed spiral antenna designs, the one presented here incorporates a completely planar balun and feed, making it more attractive for conformal applications.

/pdf/a-new-planar-feed-for-slot-spiral-antennas-2kyddrxxgf.pdf

A new planar feed for slot spiral antennas

A slot spiral (18) antenna with a planar integrated balun and feed. The slot spiral is produced using standard printed circuit techniques and comprises a dielectric substrate having a conductive layer which is etched to form the radiating slot spiral. An integrated microstrip feed (16) is included to provide a balanced feed to the slot spiral. Impedance matching is preformed between the microstrip feed and the slotline of the slot spiral to maximize energy transfer. A shallow reflecting cavity is included to limit the spiral radiation to one direction. The described antenna apparatus provides a simple, broadband spiral antenna suitable for incorporating into the skin of a moving vehicle. A covering layer may act as a dielecric lens. Outer parts of the slot spiral may be covered with a lossy absorber for termination. The feed point may be off-center with respect to the spiral.

Slot spiral antenna with integrated balun and feed

Thin cavity-backed Archimedean slot spirals are analysed through an efficient implementation of the finite element method. Through numerical analysis, fundamental differences between the free-space and cavity-backed configurations are identified. The bandwidth limitation imposed by the presence of the cavity is remedied by terminating the spiral slot with tapered resistive loading and employing larger apertures. Design improvements are presented based on the interpretation of the numerical simulations. It is shown that a 0.8 cm (0.33 in) thick and 24 cm (9 in) wide antenna can provide circular polarisation over a nearly 4:1 bandwidth.

Analysis of thin multioctave cavity-backed slot spiral antennas

This paper considers the hybridization of the finite-element and high-frequency methods for predicting the radiation pattern of printed antennas mounted on aircraft platforms. The finite-element method is used to model the cavity-backed antennas, whereas the interactions between the radiators and the substructures are treated via a high-frequency technique, such as the GTD, PO/PTD, or SBR. We present comparisons between measurements and calculations, along with a qualitative description of the finite-element and high-frequency codes employed.

Michael W. Nurnberger

Papers

Slot spiral antenna

A new planar feed for slot spiral antennas

Slot spiral antenna with integrated balun and feed

Analysis of thin multioctave cavity-backed slot spiral antennas

A hybridization of finite-element and high-frequency methods for pattern prediction for antennas on aircraft structures