High impact antenna study - Cavity-backed spiral antenna
Indirect high impact test of cavity-backed spiral antenna
SPIRAL ANTENNA↗
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A new planar feed for slot spiral antennas
This report presents a new planar, wideband feed network for a slot spiral antenna, and the subsequent design and performance of a VHF antenna utilizing this feed design. Both input impedance and radiation pattern measurements are presented to demonstrate the performance and usefulness of this feed. Almost all previous designs have utilized wire spirals, requiring bulky, non-planar feeds with separate baluns, and large absorbing cavities. The presented slot spiral antenna feed integrates the balun into the structure of the slot spiral antenna, making the antenna and feed planar. This greatly simplifies the design and construction of the antenna, in addition to providing repeatable accuracy. It also allows the use of a very shallow reflecting cavity for conformal applications. Finally, this feeding approach now makes many of the known miniaturization techniques viable options.
Nurnberger, M. W.↗
Four arm conical spiral antenna Final report
Four arm conical spiral antenna for IRLS system operation with balloon packages interrogated from satellite
Source record↗
Design considerations for an archimedean slot spiral antenna
The design goal is to develop a 118-157 MHz, vertically polarized, low-profile (or conformal) antenna as a replacement for VHF AM blade antennas on aircraft. This design is to be arrived at by scaling the dimensions of an antenna designed for a center frequency of 1.1 GHz. The design prior to scaling may have the following maximum dimensions: diameter less than 3.70 in. and thickness less than 0.50 in. Although a four-arm spiral design was originally suggested, a two-arm spiral may also be used, as both mode-1 and mode-2 (sum and difference) radiation patterns aren't required. While a four-arm spiral can easily be designed should both sum and difference patterns be required, the two-arm design will provide the required sum pattern and simplify the design problem somewhat: only one feed is required, and the feed area geometry is more straightforward. Polarization requirements dictate that a slot spiral be used, as opposed to a wire spiral. Two similar radiating structures were considered. The first is the standard archimedean spiral antenna. The second is a hollow archimedean spiral antenna, essentially a standard archimedean spiral with the inner portion removed.
Nurnberger, Michael W.↗
Radiation field of spiral antennas employing multimode slow wave techniques
Multimode slow wave planar spiral antenna design and radiation field characteristics
Cubley, H. D.↗
Matched pair conical spiral antennas
A matched pair of VHF (220-260 MHz) conical spiral antennas for use in a rocket-tracking interferometer array was designed and tested. While gain, bandwidth, impedance, and pattern measurements met specifications, the phase match between antennas at low elevations was not equal to the design goal.
Metzler, R. E.↗
Slot spiral antenna modeling using hybrid/mixed FE-BI technique
This report is concerned with the numerical simulation of the printed slot spiral antenna (SSA) using the finite element - boundary integral (FE-BI) analysis. It has been reported that the FE-BI technique is suited for modeling microstrip patch antennas of any shape, printed on layered planar structure or cylindrical platform and fed with a coaxial cable or a microstripline network underneath the radiating elements. However, direct application of the hybrid FE-BI technique to thin slot spirals requires excessive sampling rates to accurately simulate the geometry. To alleviate the meshing/modeling difficulties encountered with cavity-backed slot antennas, we describe a mixed finite element-boundary integral formulation. As in the past, the boundary integral is used to describe the radiation of the slot above the cavity. However the cavity is now modeled using a suitable mix of edge and node elements. The latter are used only at the aperture of the thin slot so that the nodes follow the center line of the slot. In this manner, regular size elements can be used regardless of the slot's width and any meshing restrictions are substantially relaxed. The proposed mixed element FE-BI formulation introduces three different computational regions and as expected this complicates the generation of the discrete system.
Gong, Jian↗
Lithographic spiral antennas at short wavelengths
We have extended the high efficiency of lithographic antennas to mid-infrared wavelengths. Pattern measurements made at 9.5/zm wavelength on a 65 deg, self-complementary, spiral antenna exhibit a ratio of response to orthogonal linear polarizations of 1.35 dB, a beamwidth of 85 deg (3 dB full width), a directivity of 8.2 dB, and surprisingly, a close resemblance to the theoretical pattern for a 65 deg spiral in free space. Direct detection measurements made with an ambient temperature blackbody source yield an antenna efficiency of 52 +/- 7 percent, when corrected for incomplete filling of the antenna beam by the source, at a mean effective wavelength of 19 micron.
Grossman, E. N.↗
Finite difference time domain modeling of spiral antennas
The objectives outlined in the original proposal for this project were to create a well-documented computer analysis model based on the finite-difference, time-domain (FDTD) method that would be capable of computing antenna impedance, far-zone radiation patterns, and radar cross-section (RCS). The ability to model a variety of penetrable materials in addition to conductors is also desired. The spiral antennas under study by this project meet these requirements since they are constructed of slots cut into conducting surfaces which are backed by dielectric materials.
Penney, Christopher W.↗
Square-Spiral Microstrip Antennas
Square-spiral microstrip antennas for wideband reception at frequencies of several gigahertz proposed. These could be made to conform to surfaces of aircraft and other vehicles. Offers advantage of thinness. Square shapes of spirals in these spiral microstrip antennas offers advantage over curved shapes of spirals of other spiral microstrip antennas in that square shapes simplifies fabrication.
Shively, David G.↗
Spiral Microstrip Antenna with Resistance
A spiral microstrip antenna having resistor elements embedded in each of the spiral arms is provided. The antenna is constructed using a conductive back plane as a base. The back plane supports a dielectric slab having a thickness between one-sixteenth and one-quarter of an inch. A square spiral, having either two or four arms, is attached to the dielectric slab. Each arm of the spiral has resistor elements thereby dissipating an excess energy not already emitted through radiation. The entire configuration provides a thin, flat, high gain, wide bandwidth antenna which requires no underlying cavity. The configuration allows the antenna to be mounted conformably on an aircraft surface.
Shively, David G.↗
Spiral microstrip antenna with resistance
The present invention relates to microstrip antennas, and more particularly to wide bandwidth spiral antennas with resistive loading. A spiral microstrip antenna having resistor element embedded in each of the spiral arms is provided. The antenna is constructed using a conductive back plane as a base. The back plane supports a dielectric slab having a thickness between one-sixteenth and one-quarter of an inch. A square spiral, having either two or four arms, is attached to the dielectric slab. Each arm of the spiral has resistor elements thereby dissipating an excess energy not already emitted through radiation. The entire configuration provides a thin, flat, high gain, wide bandwidth antenna which requires no underlying cavity. The configuration allows the antenna to be mounted conformably on an aircraft surface.
Shively, David G.↗
Simulation of Spiral Slot Antennas on Composite Platforms
The project goals, plan and accomplishments up to this point are summarized in the viewgraphs. Among the various accomplishments, the most important have been: the development of the prismatic finite element code for doubly curved platforms and its validation with many different antenna configurations; the design and fabrication of a new slot spiral antennas suitable for automobile cellular, GPS and PCs communications; the investigation and development of various mesh truncation schemes, including the perfectly matched absorber and various fast integral equation methods; and the introduction of a frequency domain extrapolation technique (AWE) for predicting broadband responses using only a few samples of the response. This report contains several individual reports most of which have been submitted for publication to referred journals. For a report on the frequency extrapolation technique, the reader is referred to the UM Radiation Laboratory report A total of 14 papers have been published or accepted for publication with the full or partial support of this grant. Several more papers are in preparation.
Volakis, John L.↗
Electromagnetic scattering and radiation from microstrip patch antennas and spirals residing in a cavity
A new hybrid method is presented for the analysis of the scattering and radiation 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 O(n). These unique features of the method have already been exploited in other scattering applications and have permitted the analysis of large-size structures with remarkable efficiency. In this report, we describe the method's formulation and implementation for circular and rectangular patch antennas in different superstrate and substrate configurations which may also include the presence of lumped loads and resistive sheets/cards. Also, various modelling approaches are investigated and implemented for characterizing a variety of feed structures to permit the computation of the input impedance and radiation pattern. Many computational examples for rectangular and circular patch configurations are presented which demonstrate the method's versatility, modeling capability and accuracy.
Volakis, J. L.↗
Simulation of Conformal Spiral Slot Antennas on Composite Platforms
During the course of the grant, we wrote and distributed about 12 reports and an equal number of journal papers supported fully or in part by this grant. The list of reports (title & abstract) and papers are given in Appendices A and B. This grant has indeed been instrumental in developing a robust hybrid finite element method for the analysis of complex broadband antennas on doubly curved platforms. Previous to the grant, our capability was limited to simple printed patch antennas on mostly planar platforms. More specifically: (1) mixed element formulations were developed and new edge-based prisms were introduced; (2) these elements were important in permitting flexibility in geometry gridding for most antennas of interest; (3) new perfectly matched absorbers were introduced for mesh truncations associated with highly curved surfaces; (4) fast integral algorithms were introduced for boundary integral truncations reducing CPU time from O(N-2) down to O(N-1.5) or less; (5) frequency extrapolation schemes were developed for efficient broadband performance evaluations. This activity has been successfully continued by NASA researchers; (6) computer codes were developed and extensively tested for several broadband configurations. These include FEMA-CYL, FEMA-PRISM and FEMA-TETRA written by L. Kempel, T. Ozdemir and J. Gong, respectively; (7) a new infinite balun feed was designed nearly constant impedance over the 800-3000 MHz operational band; (8) a complete slot spiral antenna was developed, fabricated and tested at NASA Langley. This new design is a culmination of the projects goals and integrates the computational and experimental efforts. this antenna design resulted in a U.S. patent and was revised three times to achieve the desired bandwidth and gain requirements from 800-3000 MHz.
Volakis, J. L.↗
Modeling of the Near Field Coupling Between an External Loop and an Implantable Spiral Chip Antennas in Biosensor Systems
In this paper, the near field coupling between an external hand-held loop antenna and an implantable miniature (1x1 mm) printed square spiral chip antenna used in bio-MEMS sensors for contact-less powering and RF telemetry is investigated. The loop and the spiral are inductively coupled and effectively form a transformer. The numerical results include the quasi-stationary magnetic field pattern of the implanted antenna, near zone wave impedance as a function of the radial distance and the values of the lumped elements in the equivalent circuit model for the transformer.
Simons, Rainee N.↗
A fixed tuned broadband matching structure for submillimeter SIS receivers
We have designed, fabricated, and tested a quasi-optical spiral antenna mixer with a Nb/AlO(x)/Nb tunnel junction. This design incorporates a hybrid antenna fed by a planar logarithmic spiral antenna to couple to the radiation field, as previously done with Pb based devices, as well as a newly designed matching circuit. This matching circuit is a relatively complex structure requiring several layers of photolithographic processing on top of the actual tunneling device. Computer modeling of the device predicted the measured bandwidth to within 8 percent, making scale model measurements unnecessary. We have obtained a good match from 210 GHz to 460 GHz between the antenna and a relatively large area (1.25 by 1.25 sq microns) tunnel junction with omega R(sub N) C approx. = 2 - 4.4. This compares to simple inductive stubs that attain only a few percent of total bandwidth in the submillimeter band or inductively tuned SIS arrays with an upper limit of operating frequencies well below the submillimeter band. Noise temperatures were measured at 345 GHz, 426 GHz, and 492 GHz yielding double sideband noise temperatures at 200 K, 220 K, and 500 K, respectively.
Buettgenbach, Thomas H.↗
Broadband Microstrip-to-Coplanar Strip Double-Y Balun
A new version of the double-Y balun, transitioning from an unbalanced microstrip to a balanced coplanar strip (CPS) line, has been designed to feed a complementary spiral antenna with an input impedance of 100 Omega. The new double-Y balun transitions from a microstrip line with truncated ground plane to a CPS line. The balun does not employ CPW lines; hence, CPW bridges are not required at the junction. In addition, the balun does not exhibit CPW parasitic resonances, thereby improving passband performance. The new version of the double-Y balun is designed to feed a complementary spiral antenna. Panels on the right illustrate an expanded view of the balun junction. Preliminary voltage standing-wave ratio (VSWR) and insertion loss data are illustrated. Measured data were compared with numerical results computed using Momentum. It is seen that the balun exhibits a VSWR of less than 1.5 from 400 MHz to 8 GHz and a VSWR of less than 1.8 up to 13 GHz. The VSWR can be reduced further by reducing reflections from the balun junction and load resistor. Also, the balun is seen to exhibit an insertion loss of less than 1.5 dB up to 12 GHz. Further work involves characterizing the balun's performance when feeding a complementary spiral antenna.
Venkatesan, Jaikrishna↗