Cavity-backed Spiral Antenna Research Articles

Design of a Low Profile Archimedean Spiral Antenna using Compact Defected Ground Structure as a Reflector

In this paper, design and realisation of a low profile Archimedean spiral antenna is presented. The low profile Archimedean spiral antenna is printed on a substrate and backed by a reflector consisting of DGS. The DGS unit cell consists of a parallel combination of meander line inductors and inter-digital capacitors. This, DGS is one of the forms of electromagnetic band gap (EBG) structures providing electromagnetic band gap characteristics. It is used as a reflector with spiral antenna to achieve unidirectional radiation properties and a low profile of antenna. A modified version of uniplanar EBG cell is used as a DGS cell. This cell is used for configuration of the DGS ground plane. This ground plane is evaluated for its electrical characteristics and used as a reflector for the spiral antenna. Archimedean Spiral antenna is designed and simulated in the frequency band of 1-6GHz with DGS as a reflector. The antenna characteristics are studied for physical parameters of the antenna. These parameters are optimized for better electrical characteristics. The performance of the proposed antenna is also compared with conventional metallic (PEC) reflectors. Simulated results of an antenna are validated by measurement. Antenna height reduction of 60% is achieved compared to conventional cavity-backed spiral antennas.

Low-profile closed cavity backed spiral antennas with circular AMC reflector for V/UHF bands

In this study, two low-profile wideband spiral antennas that are backed by Circular Artificial Magnetic Conductors (C-AMC) are proposed for V/UHF bands. Rather than using a C-AMC design that has single resonance frequency, different C-AMC structures that have different resonance frequencies are used beneath corresponding active regions of spiral antenna, such that frequency independent radiation characteristics are achieved. The C-AMC surface is designed to aim of covering the entire frequency band of antenna so that frequency regions where reflection phase of C-AMC rings are between +90° and −90° will follow each other. It is observed that using frequency-independent C-AMC and a thin absorber between C-AMC and outer region of spiral antenna element provides wideband antenna characteristics and improves axial ratio of antennas. Proposed Antenna 1 in this paper has low-profile (0.47λ0×0.47λ0×0.055λ0) at 300 MHz and high gain at frequencies between 300 MHz and 950 MHz. An absorbing material is used at the inner wall of the closed cavity to improve performance of Proposed Antenna 2 at lower frequencies. In this manner, 0 dBi realized gain transition point is achieved at 235 MHz. Proposed Antenna 2 has also low-profile (0.37λ0×0.37λ0×0.043λ0) at 235 MHz.

Design and fabrication of multi-material broadband electromagnetic absorbers for use in cavity-backed antennas

We investigated the feasibility of designing and fabricating novel broadband radiofrequency (RF) absorbers for use in cavity-backed antennas. Fabricating the absorber involved a multi-material additive manufacturing (AM) approach that combined two polymer filaments: a low-loss dielectric filament and a lossy carbon-loaded filament. An iterative optimization algorithm was developed to deploy these filaments and create gradient distributions of material properties that minimize reflectance over a desired frequency band and a range of incident angles to achieve wideband electromagnetic absorption. The chosen material profiles were effectively realized using a spatially varying subwavelength lattice structure printed via fused filament fabrication. Experimentally, validation results demonstrated low reflectance over a wide frequency band, 10 to 40 GHz, and a range of incident angles, 0°–50°. Finally, this printed multi-material absorber was integrated within a cavity-backed spiral antenna and used to suppress backlobe radiation while maintaining an acceptable radiation pattern in the forward direction. While this study investigated cavity-backed antennas, these computational and experimental methods are potentially useful for a wide range of other applications.

Ultra-Wideband Low-Cost High-Efficiency Cavity-Backed Compound Spiral Antenna

A low-cost high-efficiency ultra-wideband (UWB) cavity-backed spiral antenna is proposed. It employs an equiangular spiral enclosed by an Archimedean spiral and it is fed through a tapered microstrip balun. A center-raised cylindrical absorber-free cavity backs the spiral to minimize the backward radiation without decreasing the efficiency. The cavity is designed to ensure an impedance bandwidth exceeding 16:1 ratio (from 350 MHz to 5.5 GHz). Simulated and measured results are presented and compared, demonstrating competitive performance in terms of impedance bandwidth and efficiency. Time–domain measurements indicate fidelity of 0.62 at boresight.

Design of a cavity-backed spiral antenna using frequency-dependent impedance of a stepped-width arm for low frequency gain enhancement

ABSTRACTThis paper proposes a stepped-width spiral antenna for gain enhancement at a low operating frequency. The frequency-dependent characteristic of the stepped-width transmission line is applied to the spiral arm to enhance the gain at the low end of the operating frequency, and a cavity-backed ground is added to the bottom side of the antenna to further improve the gain at the bore-sight direction. To verify the gain enhancement at the low operating frequency and impedance matching characteristic, we observe the antenna performances such as bore-sight gains and reflection coefficients according to the shape of the spiral arm. The results confirm that the proposed stepped-width structure can enhance the gain at the low operating frequency by improving the impedance matching characteristic.

Miniaturization Techniques Using Magnetic Materials for Broadband Antenna Applications

This paper investigates the instrumentation necessary to analyze frequency-dependent complex parameters of solid magnetic materials based on T/R-based waveguide measurement technique proposed by W. B. Weir. Based on the magnitude and phase values of transmission and reflection coefficients measured using vector network analyzer, complex permittivity and permeability are calculated using the expressions defined. Equations necessary for calculating the complex parameters as a function of frequency with required step size are derived from the experimental results. To validate mathematical expressions developed for composite magnetic materials, the design of a compact 2-18 GHz cavity-backed spiral antenna using off-the-shelf magnetic materials is presented. The electrical performance of the cavity along with stack of high contrast magnetic materials of varying dimensions is modeled and simulated in ANSYS HFSS software.

Development of a logarithmic spiral antenna in UWB GPR for humanitarian demining

ABSTRACTA low cost cavity-backed logarithmic spiral antenna with a very wideband balun is presented for detection of Anti-Personnel land mines in ground penetrating radars. It covers a wide frequency range of 0.5 to 1.6 GHz with 10 dB return loss. The measured maximum gain of the antenna at the center frequency of 1.0 GHz, is 9.2 dBi and the axial ratio is less than 1.3 dB in the angular range of ±48°, which validates circular polarization performance. The fabricated antenna is useful in impulse GPRs for humanitarian demining due to its high penetration depth, wide bandwidth, relatively small dimensions, and low axial ratio.

Design and optimization of a cavity-backed spiral antenna for use in 6–12 GHz band

The design and optimization of a self-complementary two-arm Archimedean spiral antenna backed by an absorptive cavity were presented. Parametric studies on the proposed antenna structure were carried out by using CST MWS. Simulation results show that the proper choice of spiral turns and cavity depth can miniaturize the dimensions of the cavity-backed spiral antenna presented here. According to simulation results, prototype antennas operating in the 6–12 GHz band are fabricated and the dimension of the proposed cavity-backed spiral antenna is 22 mm (diameter)×15 mm (height). The performance of the proposed antenna was measured and compared with the simulation results. It is shown that the experimental results are consistent with the theoretical predictions and the suggested antenna is good enough to adapt for various wideband applications.

부분방전 진단용 UHF cavity-backed 스파이럴 안테나

In this paper, a UHF cavity-backed spiral antenna for partial discharge diagnosis is proposed. The proposed antenna consists of two-arm Archimedean spiral, a cavity, and a balun for feeding. The spiral antenna is designed for 0.3-1.5 GHz operating frequency. Two spiral arms of the proposed antenna are fed by a microstrip tapered-balun. In order to enhance the gain, the cavity is located in the back side of the spiral pattern. The proposed antenna is designed and simulated using CST Microwave Studio. The designed antenna is also fabricated and tested to validate performance. The measured radiation patterns are directional to the +z-axis and measured peak gain is 9.92 dBi.

Characterization, Design and Optimization of Low-Profile Cavities for UWB Spiral Antennas

In this paper, we present a methodology for developing very low profile, hybrid, cavity-backed UWB spiral antennas from a precision electromagnetic material characterization standpoint. Using our method, we have accurately characterized, designed and optimized the dimensions of a 2-18GHz, cavity-backed Archimedean spiral antenna. The si- mulation and measurement results show that the antenna demonstrates excellent axial ratio and gain-bandwidth perfor- mance while maintaining an absorptive cavity depth of only 0.625 inches. The procedure can be extended to the design and optimization of any low-profile spiral radiator required to operate over extremely broad frequencies.

0.5~2 GHz 캐비티 백 스파이럴 안테나 설계

본 논문에서는 0.5~2 GHz 캐비티 백 스파이럴 안테나 설계에 대하여 기술하였다. 안쪽 부분은 Archimedean 스파이럴로, 바깥 부분은 log 스파이럴로 구현된 암(arm) 패턴, 백 캐비티(backing cavity), 그리고 급전용으로 Marchand 동축형 밸런을 설계하였다. 동작 대역의 저주파 대역에서 안테나 특성을 향상시키기 위하여 종단 저항을 사용하였다. CST사의 MWS툴을 이용하여 시뮬레이션 하였고, VSWR, 축비(axial ratio), 이득 그리고 반전력 빔폭을 고찰하였다. 최종적으로 제작 및 측정을 통해 설계 방법의 타당성을 검증하였고, 상용 스파이럴 안테나와의 성능을 비교하였다. In this paper, the design of a 0.5~2 GHz cavity-backed spiral antenna is described. Combined arm pattern with a log spiral in the inner region and an Archimedean spiral in the outer region, a backing cavity, and a Marchand coaxial balun for feeding are designed. Termination resistors are used to improve antenna characteristics at the lower frequency of the operation frequency. VSWR, axial ratio, gain and HPBW(Half Power Beam Width) characteristics are simulated using CST's MWS. Finally, the validity of these approaches is verified by comparing the simulated results with the measured ones. Also, the measurement results are compared with the performance of a commercial spiral antenna.

2~18 GHz 광대역 캐비티 백 스파이럴 안테나 설계

In this paper, design of a GHz wideband cavity-backed spiral antenna is investigated. Firstly, an arm pattern and a backing cavity of a cavity-backed spiral antenna are designed based on the design theory of an Archimedean spiral antenna as well as by using CST`s MWS. VSWR, axial ratio, and HPBW(Half Power Beam Width) characteristics are considered in the simulation. Secondly, a Marchand coaxial balun is designed to meet the required VSWR within the frequency band of operation. Finally, the validity of these approaches is verified by comparing the simulated results with measured ones.

A cavity‐backed spiral antenna with an unbalanced feed system—analyses using FD‐TD and moment methods

AbstractThe FD‐TD method and the moment method are used to analyze a two‐wire square spiral antenna backed by a conducting square cavity (SAC). The SAC is fed from a coaxial line without a balun circuit. First, the SAC is analyzed using the FD‐TD method. The SAC design is based on radiation characteristics of a two‐wire square spiral antenna backed by a conducting plane reflector (SAR). It is found that the frequency bandwidth for a 3‐dB axial‐ratio criterion is 12% (18% for SAR), with a gain of 7 dBi (8 dBi for SAR). Second, the moment method is used to analyze a wire‐grid model of the SAC. Grid sizes appropriate for the analysis are determined on the basis of the FD‐TD solutions. It is revealed that the grid size for the cavity side plates is 1.3 times larger than that for the cavity bottom plate. Third, a two‐SAC array is analyzed to reveal the mutual coupling. Calculation shows that the decoupling factor is larger than that for a two‐SAR array by approximately 3 dB. The computation time and memory size required for the analyses are compared between the two cases for the FD‐TD and the moment methods. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(1): 53–63, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10211

Electromagnetic Scattering from Microstrip Patch Antennas and Spirals Residing in a Cavity

ABSTRACT A new hybrid method is reviewed for the analysis of the scattering by conformal antennas and arrays comprised of circular or rectangular elements. In addition, calculations for cavity-backed spiral antennas are given. The method employs a finite element formulation within the cavity and the boundary integral (exact boundary condition) for terminating the mesh. By virtue of the finite element discretization, the method has no restrictions on the geometry and composition of the cavity or its termination. Furthermore, because of the convolutional nature of the boundary integral and the inherent sparseness of the finite element matrix, the storage requirement is kept very low at 0(n). These unique features of the method have already been exploited in other scattering applications and have permitted the analysis of largo–size structures with remarkable efficiency. In this paper, we describe the method’s formulation and implementation for circular and rectangular patch antennas in the presence of lumpe...