Flush-mounted Antenna Research Articles

Wideband Antennas of Passive Seekers for Anti Radiation Missiles

Suppression of Enemy Air Defence (SEAD) is a fundamental element of Air Power application by means of in protecting friendly air attackers and destroying the enemy’s ability to defend against air attack. Most of the SEAD operation even today relies on Anti-radiation missile (ARM) which is an air-to-surface tactical missile designed to detect, seek, attack and destroy opponent’s radar. Passive seeker of ARM is a miniaturized ESM receiver which is capable of extracting the necessary angular data from the enemy radar emissions. Single head passive seeker covering wide frequency range from L to Ku band is the preferred choice. Wideband antennas have been designed and utilized for Direction Finding applications of ESM/ELINT receivers for ground, air and ship borne platforms. Unlike these platforms, there are several restrictions for passive seeker based compact ESM receiver for missile borne platform specially air to surface missile where lesser diameter is one of the preferred design parameter. This review paper mainly discusses the existing wideband antennas such as spiral, log-periodic, printed circuit vivaldi and all-metal vivaldi antennas and the comparison of their various parameters for passive seeker. The paper also suggests their suitability with respect to their placement on the missile for three configurations: concealed inside the radome, flush-mounted and conformal antenna based. The paper also brought about the specific test facility required for testing and evaluation of passive seeker to characterize it with missile radome which is the most challenging and time consuming task. Among the three passive seeker configuration discussed, conformal antenna based passive seeker using all-metal Vivaldi is the best option avoiding radome aberration correction which is being utilized in the present third generations of ARM. The second commonly and established passive seeker configuration is concealed inside the radome using spiral antennas where handling radome aberration correction is a limitation.

A New High-Isolation Broadband Flush-Mountable Dual-Polarized Antenna

A new broadband flush-mountable dual-polarized antenna with very high isolation is proposed. The antenna is made up of a pair of crossed slots that are fed by two orthogonal microstrip feedlines. A metallic cavity is introduced to back the slot antenna for unidirectional radiation pattern. By setting the microstrip feedlines on two substrate layers separated by a metal ground on which the crossed slots are etched, the antenna achieves a high isolation of 40 dB. The antenna has a broad bandwidth (BW) of about 47%, which is due to the wide crossed slots and the impedance matching of the feedlines. It is shown that the antenna can be easily flush mounted on a metal surface without affecting the high isolation and the broad BW performance. The proposed antenna may be used as flush-mountable antennas in wireless sensor/communication systems for high-speed vehicles/aircrafts.

A Broadband Flush-Mountable Dual-Polarized Dual-Slot Antenna

A novel broadband dual-polarized flush-mountable dual-slot antenna is proposed in this letter. The antenna consists of two identical crossed dual-slot elements, each of which is made up of two slots that connected through a pair of coplanar waveguides. Two orthogonal microstrip feedlines are used to feed the crossed dual-slot elements for vertical and horizontal polarizations. A metallic cavity is introduced to back the slot antenna for unidirectional radiation patterns. The proposed antenna achieves a broad bandwidth of 40.7% for return loss (RL) >15 dB with isolation better than 32 dB. The proposed flush-mountable antenna is suitable for sensor/communication systems of high-speed vehicles and aircrafts.

Analysis and Design of Cavity-Backed Probe-Fed Hybrid Microstrip Antennas on FR4 Substrate

A novel cavity-backed probe-fed linearly polarized microstrip antenna based on the concept of hybrid radiators is proposed and implemented. The resulting flush-mounted antenna exhibits symmetrical bandwidth, low cross-polarization radiation in theH-plane, due to its hybrid patch, and low cost, since it can be built on a FR4 laminate. Substrate integrated waveguide technology is used in the fabrication of the metallic cavity. The effect of mutual coupling is analyzed for two classical arrangements: the side-by-side and the collinear configurations.

Propagation Between On-Body Antennas

The theory of propagating waves near a surface is reviewed with an eye to gain insight into the mechanisms involved, and to provide analytical-based models, for power-efficient on-body propagation. The Zenneck wave, and in particular the Norton wave, are appraised as candidate mechanisms for the propagation. For flush-mounted (ldquoband aidrdquo) antennas, desired for on-body sensors, the Norton wave is the only direct propagation mechanism between the sensors. The Norton wave fits very well to simulation results presented here, and comparisons are also made with available published physical experiments, although these measurements typically feature the optical paths of elevated, or non-flush, antennas.

Paraxial and source region behavior of a class of asymptotic and rigorous (MoM) solutions in the high-frequency planar limit

Mutual impedance between flush-mounted antennas on convex surfaces has been traditionally computed at high frequencies using the uniform theory of diffraction (UTD) and other high-frequency asymptotic solutions. Motivated by a recent study, the limits of applicability of the existing asymptotic techniques to the calculation of input (or self-) impedance are investigated here. It is shown analytically that UTD and one other asymptotic formulation, in the close vicinity of a source on a perfectly electrically conducting (PEC) circular cylinder, for negligible local surface curvatures, are algebraically identical. For the canonical geometry of an axial magnetic current element on a PEC circular cylinder, it is shown that the additional paraxial correction term in the UTD formulation vanishes in the high-frequency planar limit. Numerical comparisons against rigorous method of moments (MoM) solutions show that the reduced-planar forms are remarkably accurate for source-to-observer separations, t, where 0.02/spl lambda//sub o//spl les/t/spl les/0.08/spl lambda//sub o/, and slightly off the axial direction.

Hybrid finite element-boundary integral method for cavities recessed in an elliptic cylinder

The highly versatile finite element-boundary integral method is presented for accurate modeling of fields within cavities recessed in a perfectly conducting, infinite, elliptic cylinder. Properties of flush-mounted cavities and antennas are explored and compared with prior developments. This formulation represents a significant advancement over prior techniques since surface curvature variation, either across a single element or across an array of elements, is now accurately included into the antenna model. An advantage of this approach is the ability to model cavities with curvature varying from planar to the constant curvature of a circular cylinder. Computed eigenvalues for planar-rectangular and cylindrical-rectangular closed cavities are compared with theoretical values. Eigenvalues are presented for elliptic-rectangular cavities. Furthermore, the input impedance of a conformal cavity-backed patch antenna mounted on an elliptic cylinder is presented and compared with a similar antenna on a circular cylinder.

Mutual coupling reduction of low-profile monopole antennas on high-impedance ground plane

Mutual coupling effects of flush-mounted (horizontal) monopole antennas on high-impedance ground planes (HIP) have been measured. Experiments of horizontal monopoles on HIP with a bandgap centred at 4.7 GHz show that the interference between two adjacent elements is stronger compared to those on a regular metal ground plane due to special properties of HIP. A technique using a combination of HIP and thin metal strip is proven to reduce the mutual coupling by ∼6 dB. Similar results have been obtained for the horizontal monopoles on HIP with a bandgap centre at 17 GHz.

Frequency-independent antennas and broad-band derivatives thereof

The principles used in the development of frequency-independent antennas are reviewed. Examples of log-periodic (LP) geometry and the additional requirements that must be met for practical success are given. The evolution of unidirectional, wire-outline, and dipole arrays is presented. Analytical results for LP dipole arrays led to the concept of an active region that remains almost fixed in size relative to the wavelength. Periodic structure theory serves as an aid to understanding LP structures. The analysis of periodically loaded lines shows the problems that may arise from the existence of stop regions on LP antennas and provides procedures for eliminating them. This has led to successful LP monopole and cavity-backed slot arrays. Planar and conical log-spiral antennas are discussed. Frequency-independent, circularly polarized patterns-bidirectional, unidirectional, omnidirectional, and conical-can be provided from log-spiral antennas with two or more arms. Recently, the LP design principles have been applied to low-profile antennas: patches, thin cavities, and spirals over ground. They have also produced flush-mounted aircraft antennas that can respond simultaneously to two different linear of circular polarizations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis of a dielectric resonator antenna in a cylindrical conducting cavity: te and tm modes

A new configuration for a flushmounted resonator antenna is presented in which the antenna is formed by a conducting cavity with a dielectric post, and radiates through an annular slot in the upper ground plane. An aperture magnetic current integral equation is used to model the slot, and the effect of the post resonator and cavity are included via Green&apos;s function techniques. The formulation is presented for the azimuthally-independent TE and TM cases. The moment method is applied to the integral equation, and the complex resonant frequencies for the antenna structure are found by searching for the zeroes of the determinant of the impedance matrix in the complex-frequency plane. The radiation Q factor, slot-field distribution, and radiation field are subsequently computed at the resonant frequency. Various TE and TM modes have been investigated for different geometrical configurations.

A crossed‐slot antenna backed by a rectangular cavity

AbstractA shallow cavity‐backed slot antenna has been used as a flushmounted antenna in a high‐speed moving object since it is resistant to vibration and shock. This paper presents a theoretical analysis for a circularly polarized antenna consisting of a crossed‐slot along the diagonal line on the surface of a rectangular shallow cavity. As a method of analysis, the reaction matching method has been used which was developed by Richmond as a form of the moment method by Harrington. By means of this method, the input impedance can be obtained over a broad frequency range in the case where an offset feed and a multiple feed are used. In this paper, an offset symmetric two‐point feed is used so that the impedance matching can be realized easily. The input characteristics and the radiation characteristics of the antenna element are obtained numerically and the obtained results are discussed.

Antenna admittance determination of electron density.

A circular-aperture flush-mounted antenna for which a theoretical description of the antenna-plasma interaction has been developed was used to obtain a comparison between theoretical and experimental antenna admittance in the presence of ionized boundary layers of low-collision frequency. The antenna was located in a flat-plate model which was in turn located in the expanding-flow environment of a reflected-shock tunnel. The electron-temperature and electron-density distributions in the plate boundary layer at the antenna location were independently measured using voltage-swept thin-wire Langmuir probes for one of the test conditions. The antenna admittance was measured using a four-probe microwave reflectometer and these measured values were found to be in good agreement with those predicted from the theory. Measurements were also performed with another type of circular-aperture antenna which did not satisfy all of the constraints of the theoretical model, although good agreement was obtained between the calculations and the experimental results.

Radiation field of spiral antennas employing multimode slow wave techniques

The results of both analytical and experimental research in the area of multimode slow wave planar spiral design are reported. This research is directed toward the development of a compact flush-mounted multimode antenna for future space applications. The technique followed in this investigation was to first modify existing analytical models of planar spiral antennas to take into account the effects of the slow wave geometry on the radiated pattern. These models are then used to optimize the design of certain multimode slow wave planar spiral antennas. Experimental antennas corresponding to these optimized designs were constructed and their field patterns are compared to those predicted by the analytical models. The comparison of the results indicates very favorable agreement between the analytical predictions and experimental data.

Beam tilt-angle compensation for a rotatable flush-mounted surface-wave antenna on an asymmetrical ground plane

The beam tilt angle of a rotatable flush-mounted surface-wave antenna mounted on the underside skin of an aircraft varies as the antenna is mechanically scanned in azimuth. This beam tilt-angle variation results because the antenna is presented with a finite asymmetrical ground plane, which introduces a wide range of ground-plane conditions to the antenna as a function of azimuth angle. A method that can compensate partially for these beam tilt variations for low beam tilt angles is described.

A Flush-Mounted Glide-Path System

An instrument-landing system glide-path has been developed which produces a straight-line path originating directly from the touchdown region on the runway. This system makes use of five flush-mounted runway antennas which are mounted directly in the runway, thus eliminating the ground-reflected signals which are presently used to form the path. As a result, the effects of terrain irregularities in the approach region are minimized. Additional benefits realized in flush-mounting the glide-path system are the elimination of parallax problems encountered by flight close in, and the elimination of hazards of antenna supporting masts and buildings near the runway. Potential use of the glide-path at low elevations is enhanced by the paralleling of the path limits during the last 600 feet of the flight path. The path limits cease to converge and maintain a constant value which provides tolerance especially necessary for pilot-controlled flights, while still maintaining sufficient margin of safety. This new glide-path system is completely compatible with the present airborne equipment, and only a minor addition to the transmatter need be made. Automatic servo monitoring is provided for maximum stability in addition to conventional fail-safe monitoring.

Pattern synthesis with a flush-mounted leaky-wave antenna on a conducting circular cylinder

Pattern synthesis with a flush-mounted leaky-wave antenna on a conducting circular cylinder

The flared slot: A moderately directive flush-mounted broad-band antenna

The flared slot is a simply constructed antenna designed to be flush-mounted in a horizontal surface. Its pattern is a moderately directive pencil beam over a 4:1 frequency band, and its impedance bandwidth is essentially that of a coaxial line-to-ridged waveguide transition. Both vertically and horizontally polarized models are discussed.

A Flush-Mounted Runway Antenna for Use with the FAA Directional Glide-Path System

A flush-mounted airport runway antenna has been designed, built, and tested which will allow glide-path signals for instrument landings to be radiated directly from the touchdown point on the runway. Empirical and simplified analytical design procedures are discussed together with a comparison of desirable and measured antenna characteristics. Sufficient low-elevation angle directivity has been obtained from a prototype antenna to provide a path which extends well beyond 5 miles, the approximate distance at which the glide is intercepted in practice.

A flush-mounted leaky-wave antenna with predictable patterns

This paper describes the design and the measured performance of a large, flat antenna consisting of an inductive grid spaced over a conducting surface. The analysis employs the transverse-resonance method to determine the radiating properties of the structure. This analytical technique is shown to predict very accurately the amplitude and phase of the illumination along the aperture of the antenna. An antenna was built with an 18- by 24-inch aperture and tested over the frequency band from 7-to-13 kmc. The results of these tests confirm the theoretical predictions in every detail. A pencil beam from the antenna scans in the H-plane (perpendicular to the antenna) from 20\deg to 60\deg from the normal to the aperture as the frequency changes from 7-to-13 kmc. The H-plane beamwidth remains virtually constant over most of this band. The first H-plane sidelobe or shoulder is at least 29 db below the main lobe from 7-to-10 kmc, and at least 23 db below from 10-to-13 kmc. All H-plane sidelobes beyond three or four beamwidths on either side of the main lobe are at least 40 db below the main lobe everywhere in the 7-to-13 kmc band. At the design frequency the measured pattern agrees with the theoretical pattern within a fraction of a db down to 40 db below the peak of the main lobe, even though the gain of the antenna at this frequency is only 33 db.

U.S.A. national commitee report URSI subcommission 6.3 antennas and waveguides, and annotated bibliography

Recent developments in some of the more active areas of antenna and diffraction theory are summarize& Although concerned primarily with U.S.A. activity, some reference is made to the literature of other countries where closely allied work is in progress. Fields included in this survey are broad-band antennas, wide-angle microwave optics, antennas for ionospheric scatter propagation, traveling-wave antennas, slot radiators, diffraction, and scattering theory. Recent work in broad-band antennas has been concerned mainly with trying to hold both radiation pattern and impedance independent of frequency. The problem has been approached successfully through development of that class of antenna shapes which depends on angles only. The equiangular spiral is a simple example. In microwave optics the requirements for wide-angle scanning of antenna beams have been met largely by using new light-weight, low-loss dielectrics to construct suitable lenses such as a spherical Luneberg lens. Using the geodesic analog of the Luneberg lens in one plane a scan of 40 beamwidths without aberrations has been obtained. The very high gain required for antennas suitable for VHF ionospheric scatter propagation has been obtained through use of long horizontal rhombics and, more recently, by corner reflector antennas driven by collinear arrays of dipoles. The latter antennas have the important advantage for this application of much lower sidelobe level Traveling-wave antennas have received much attention in recent years because of their inherent adaptability to flush-mounted applications. Among the forms considered are corrugated surfaces and single or double dielectric-clad surfaces. The launching problem has been studied rather intensively and recent interest has been shown in the synthesis and scanning aspects for slow-wave structures. Progress has continued in the exploitation of fast-wave systems, with major advances centering on the launching problem and the polarization problem. Strip lines are taking an important place as feeding systems for traveling-wave antennas. Recent years have been marked by considerable research activity on flush-mounted microwave antennas. Such antennas often take the form of slots or apertures in the metallic surfaces of aircraft. The radiation pattern of the slot radiator depends upon the shape of the metallic surface in which it is cut, and for complicated shapes resort is made to experiment. However, certain simple geometric shapes have been treated mathematically. These shapes include the circular cylinder, half plane, wedge, sphere, elliptic cylinder, oblate and prolate spheroid, and cones. Various combinations of these shapes on which work also has been done are the semicircular boss on a flat ground plane, the cylindrically tipped wedge, and the spherically tipped cone. The problem of radiation from apertures in a metallic surface is closely related to the reciprocal problem of calculating the currents excited on the surface by an incoming wave. As a direct consequence of the reciprocity theorem there is an intimate connection between slot radiators, diffraction, and scattering. The result is that the extensive body of knowledge classed as diffraction and scattering must be considered as an integral part of antenna theory. During the past three years there has been a very considerable effort in obtaining new exact solutions, several new approximate solutions, and a better physical understanding of the mechanisms involved in scattering. All of the geometric shapes mentioned above have received attention, and much experimental work has also been done. For the future it can be expected that this intensive effort will continue with emphasis on the asymptotic approaches of Kline and Keller, the method proposed by Logan, and Fock's method of obtaining asymptotic results based on local analysis.