Showing papers on "Coaxial antenna published in 1998"

On the behavior of the Sierpinski multiband fractal antenna

Abstract: The multiband behavior of the fractal Sierpinski (1915) antenna is described. Due to its mainly triangular shape, the antenna is compared to the well-known single-band bow-tie antenna. Both experimental and numerical results show that the self-similarity properties of the fractal shape are translated into its electromagnetic behavior. A deeper physical insight on such a behavior is achieved by means of the computed current densities over the antenna surface, which also display some similarity properties through the bands.

Design of wide-band aperture-stacked patch microstrip antennas

Abstract: A variation of the aperture-coupled stacked patch microstrip antenna is presented, which greatly enhances its bandwidth. Bandwidths of up to one octave have been achieved. The impedance behavior of this antenna is compared with that of other wide-band microstrip radiators. Matching techniques for the antenna are presented and their relative merits discussed. The effects of varying several key physical parameters of the antenna are investigated, lending some insight into its wide-band operation. Variations on the design such as incorporation of additional patches are also discussed.

Microstrip-fed quasi-Yagi antenna with broadband characteristics

Abstract: A compact and uniplanar antenna with broadband characteristics is presented. The novel Yagi-like printed dipole array antenna is fed by a microstrip-to-coplanar strip transition, and uses the truncated microstrip ground plane as its reflecting element. An X-band prototype measures a bandwidth of 17%. With 6.5 dB gain, 18 dB front-to-back ratio, and lower than -15 dB cross-polarisation level at 10 GHz.

Double resonance antenna structure for several frequency ranges

Abstract: The invention relates to small-sized antenna systems, especially planar antenna structures operating on several frequency bands. The antenna structure of the invention comprises a radiating antenna element with at least two lips. Thus, the antenna structure has two basic resonance frequencies, which are defined by the dimensions of the lips of the antenna element, gaps between them, and the other dimensions of the antenna structure. The radiating antenna structure is connected to the ground plane at least at one place. The radiating antenna element comprises at least two connection points, which are used for connecting the feed lines of the transmitter and receiver, and for connecting special tuning elements. The resonance frequencies of the antenna structure may be adjusted by connecting the said tuning elements to the connection points and antenna feed lines so that the antenna structure is operable on more than two frequency bands. The switches may be conventional semiconductor switches, such as FET switches or PIN diodes. Various optionally connectable tuning element or antenna feed arrangements may be used for carrying out an antenna arrangement which may be tuned in on all reception and transmission bands of an arrangement with several frequency ranges and mobile phone systems.

Ultra-wideband magnetic antenna

Abstract: An ultra-wideband magnetic antenna includes a planar conductor having a first and a second slot about an axis. The slots are substantially leaf-shaped having a varying width along the axis. The slots are interconnected along the axis. A cross polarized antenna system is comprised of an ultra-wideband magnetic antenna and an ultra-wideband dipole antenna. The magnetic antenna and the dipole antenna are positioned substantially close to each other and they create a cross polarized field pattern. The present invention provides isolation between a transmitter and a receiver in an ultra-wideband system. Additionally, the present invention allows isolation among radiating elements in an array antenna system.

Folded reflectarray antenna

Abstract: A novel folded reflectarray antenna is presented. This antenna combines a twist and focusing reflector concept in a single printed structure. Together with a printed grid, a low profile and high gain antenna results. A test antenna in the 20 GHz range was designed, fabricated and tested.

Polarization diverse antenna for portable communication devices

Abstract: A communications card having an antenna assembly providing polarization diversity for use with a portable computer is provided. The antenna assembly comprises two folded antennas, which may be dipoles or slot radiators, that are disposed orthogonally to one another to provide polarization diversity. Signals are carried to and from the antenna by microstrip feed lines. The microstrip lines are placed off center along each antenna slot to establish an acceptable impedance match for the antenna. The feed lines are coupled to the communications card by way of coaxial cables. The antenna assembly is coupled with the communications card in a hinged arrangement thus allowing for spatial redirection of the antenna, if desired.

Single-feed square-ring microstrip antenna with truncated corners for compact circular polarisation operation

Abstract: A novel circular polarisation (CP) design of a single-feed square ring microstrip antenna with truncated corners is described. Experimental results show that the proposed design has a reduced antenna size as compared to the conventional circularly-polarised square microstrip antenna with truncated corners at a given operating frequency. Also, the required size of the truncated corners for CP operation is larger for the present design than for the conventional design using a square microstrip patch, which suggests that the fabrication tolerance is relaxed for the present design. Typical results are presented and analysed.

A new design tapered slot antenna for ultra-wideband applications

Abstract: This paper describes the design and the high performance of a new balanced antipodal Vivaldi antenna for ultra-wideband applications. The return loss, radiation pattern, antenna gain, and level of cross polarization of this antenna are presented for both simulated and experimental results. The antenna is demonstrated to have greater than decade bandwidth (impedance within 10 dB over 1.3–20 GHz) and low cross polarization (<−17 dB in the broadside direction) over the band. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 286–289, 1998.

Miniature printed spiral antenna for mobile terminals

Abstract: The present invention seeks to overcome the above-identified deficiencies in the art by providing a built-in printed spiral antenna which is small enough to satisfy the needs of future compact mobile terminals. According to exemplary embodiments, a built-in antenna is provided which includes a printed spiral metal strip that is connected to the mobile terminal's printed circuit board via a substrate. Matching of the antenna is performed by a matching bridge which is positioned between a feeding pin and a grounded post. By adjusting the length of the matching bridge, the matching of the antenna can be changed. In an alternative embodiment, a loading resistor is attached to the matching bridge in order to enhance the bandwidth of the antenna. The size of the antenna of the present invention can be reduced to 20-30% of the conventional PIFA antenna (i.e., less than {fraction (1/10)} of the wavelength of the operating frequency). As a result, the antenna can be used in a very compact chassis.

Performance of a meandered line as an electrically small transmitting antenna

Abstract: For antennas to radiate at maximum efficiency, their dimensions must be on the same order as the radiated wavelength At frequencies below 30 MHz, antennas with efficient radiation are often too large for mobile and portable applications Smaller antennas can be made to radiate efficiently by use of matching networks For installation convenience and ease of adjustment, these networks are usually placed between the transmitter and the antenna input; but it has been found that for best radiation efficiency, matching network elements should be placed at points on the antenna structure Unfortunately, such matching networks must be tuned for each transmitting frequency and, when mounted on the antenna, they cannot easily be tuned A meander element antenna was found to present some electrical and mechanical properties allowing convenient placement of tuning elements when configured as an electrically small transmitting antenna Some simplified design guidelines were derived from experimental data

Microstrip antennas for SAR applications

Abstract: This paper discusses various methods of implementing a shared-aperture dual-frequency dual-polarized array antenna for spaced-based synthetic aperture radar (SAR) applications. After evaluating the use of several potential array architecture concepts and radiating elements, a design using interlaced C-band microstrip patches and X-band printed slot elements was chosen as the best choice for the present system requirements. Layout considerations for the two arrays and their associated feed networks are addressed in terms of a practical design. A dual-frequency (C- and X-band), dual-linear polarized SAR array antenna prototype was designed, fabricated, and tested. The principal goal of this effort was to demonstrate the viability of the dual-band dual-polarized array concept, and this has been accomplished. Test results are shown with good correlation between measured and predicted results, validating the design approach used. This work demonstrates that a dual-frequency dual-polarization SAR antenna within a single aperture is a feasible approach to meeting user requirements in future SAR spacecraft.

Single-feed dual-band circularly polarised microstrip antenna

Abstract: A novel technique for obtaining dual-band circular polarisation (CP) radiation of a single-feed circular microstrip antenna is proposed and demonstrated. By embedding two pairs of arc-shaped slots of proper lengths close to the boundary of a circular patch, and protruding one of the arc-shaped slots with a narrow slot, the circular microstrip antenna can perform dual-band CP radiation using a single probe feed. Details of the antenna design and experimental results are presented.

Broadband antenna realized with shorted microstrips

Abstract: The invention relates to antenna structures, particularly to substantially planar broadband antennas realized by microstrips. The antenna structure according to the invention has at least two superimposed strips (10, 20), which have a length of about a quarter-wave and which at one end are short circuited to the ground plane (30). The strips (10, 20) have certain resonance frequencies, which are tuned close to each other so that the operating band of the antenna structure is substantially continuous.

Wide-band multiport antenna characterization by polarimetric RCS measurements

Abstract: A theoretical description of the scattering of multiport antennas is derived in accordance with the polarimetric radar target characterization. For two-port antennas with dual linear orthogonal polarization, a procedure for the determination of the antenna mode scattering parameters and the structural scattering parameters of the complete polarimetric antenna scattering matrix [S] is given. A measurement setup and experimental results of wide-band polarimetric radar cross section (RCS) antenna measurements are presented. For two-port antennas, in total, 24 unknowns have to be determined. The load variation method is used. The polarimetric RCS antenna measurement is especially advantageous over a wide bandwidth; for example 2-40 GHz with only one single calibration. From the antenna scattering matrix [S], the antenna parameters like polarimetric gain, optimum gain, gain bandwidth, wave admittance, structural scattering, etc., are derived. Results are shown for an X-band horn antenna and a 2-18-GHz dual linearly polarized horn. The measurement technique and evaluation gives the most complete and very accurate information about antenna radiation, antenna characteristics, and scattering obtainable with one single measurement setup. Some quantities determined here, like the maximum available gain and the polarization characteristics, are difficult to access with standard transmission measurements. No cable from the antenna to the receiver is necessary. This helps avoid some difficulties usually experienced at low signal levels.

Optically transparent microstrip patch and slot antennas

Abstract: An antenna (10, 110, 210) comprising a ground layer (30, 130, 230), a feed layer (50, 150, 250), an antenna layer (40, 140, 240) and a transparent dielectric substrate (20, 120, 220) interposed between two of the layers (30 and 40, 140 and 150, 230 and 250). An electromagnetic field is produced between the ground layer (30, 130, 230) and the antenna layer (40, 140, 240) when the feed and ground layers (50 and 30, 150 and 130, 250 and 230) are exposed to a microwave frequency above 3,000 megahertz for transmission and when the antenna and ground layers (40 and 30, 140 and 130, 240 and 230) are exposed to a microwave frequency above 3,000 megahertz, for reception. The ground layer (30, 130, 230), feed layer (50, 150, 250) and antenna layer (40, 140, 240) are made of an optically transparent and electrically conductive material. About 30% of the visible light impinging on the antenna (10, 110, 210) passes through the antenna.

A biconical multibeam antenna for space-division multiple access

Abstract: The biconical antenna is well known as an easy to build broad-band antenna with omnidirectional radiation. In this paper, the biconical antenna is modified for selective radiation in the azimuth direction. By enlarging the diameter of the coaxial feed to the biconical antenna, a set of higher order modes can be excited. In addition to the angle independent TEM mode, higher order TE-modes are also allowed for propagation, which result in an angle-dependent far-field pattern. Several features of this multimode excitation are of interest. Applying multiple input feed connectors allows simple rotation of the antenna beam by switching or, when independently operated, transmission and reception for communication in different angular directions for real-time space division multiple access (SDMA). As with conventional antenna arrays, adaptive pattern synthesis can also be realized by using multiple input feed connectors in combination with an appropriate amplitude and phase shifting network. The antenna allows an extremely flexible design of its characteristics at low cost, both requisites for SDMA communication.

Dielectric lens assembly for a feed antenna

Abstract: A novel and improved dielectric lens assembly ( 100 ) includes a dielectric extension ( 108 ) on a hemispherical dielectric lens ( 104 ), to provide a dielectric lens which exhibits properties of an elliptical lens. The extended dielectric lens can be implemented with a feed antenna ( 112 ) to improve the directivity of the antenna. The extension portion ( 108 ) of the lens assembly ( 100 ) is fabricated using a plurality of dielectric wafers disposed on the bottom surface of the hemisphere, an angled extension ( 516 ), or a cylindrical extension. The entire hemispherical lens and extension assembly ( 508 ) can be a single piece of dielectric material formed into the desired shape, or the assembly can be fabricated using a plurality of dielectric components ( 512, 516 ) coupled together to form the lens assembly.

Single-feed dual-frequency rectangular microstrip antenna with square slot

Abstract: By cutting a square slot at the centre of a rectangular microstrip patch, both compactness and dual-frequency operation can be achieved. Several designs have been implemented. From the experimental results obtained, the required antenna size using the proposed design method can be reduced by /spl sim/17% compared to that of the conventional design method using a simple patch without the slot. Typical experimental results are presented and discussed.

Method and arrangement for adjusting antenna pattern

Abstract: A method and an arrangement for adjusting an antenna pattern particularly in an SDMA system where a transmitter and a receiver include at least two antennas. Baseband antenna signals are multiplied by coefficients shaping the antenna pattern, in order to produce a desired antenna pattern. The phase and strength of a baseband antenna signal are measured. On the basis of the measurement, the differences in phase and strength between the antenna signals are compensated by adjusting the coefficients shaping the antenna pattern.

Modified planar inverted F antenna

Abstract: The design of a modified planar inverted F antenna (PIFA) which is more compact (antenna length

Terminal antenna for communications systems

Abstract: An inexpensive high gain antenna (11) for use on terminals communicating with low earth orbit (LEO) satellites (31, 33, 34 and 35) which include an elevation table (19) mounted for arcuate movement about a transverse axis (Xt) on an azimuth turntable (12) mounted for rotational movement about a central axis (Zg). A plurality of antenna elements (21) forming a phased array antenna are mounted on the top of the elevation table (19) and have a scan plane (30) which is parallel to and extends through the transverse axis (Xt) of the elevation table (19). The antenna (11) may be both mechanically and electrically scanned and is used to perform handoffs from one (LEO) satellite (31, 33, 34 and 35) to another by positioning the elevation table (19) of the antenna (11) with its boresight in a direction intermediate the two satellites (34, 35) and with the scan plane (30) of the antenna (11) passing through both satellites (34, 35). At the moment of handoff, the antenna beam (32) is electronically scanned from one satellite (31) to another (33) without any loss in data communication during the process.

A 94 GHz aperture-coupled micromachined microstrip antenna

Abstract: In this paper, we present an aperture-coupled micromachined microstrip antenna operating at 94 GHz. The design consists of two stacked silicon substrates: (1) the top substrate, which carries the microstrip antenna, is micromachined to improve the radiation performance of the antenna, and (2) the bottom substrate, which carries the microstrip feed line and the coupling slot. The measured return loss is -17 dB at 91 GHz for a 10-dB bandwidth of 11%. The radiation patterns show a measured front-to-back ratio of -10 dB at 91 GHz. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies.

Small rectangular patch antenna

Abstract: A novel folded rectangular patch antenna is designed and measured. Compared with a conventional patch antenna with the same surface area, the resonant frequency is reduced by 37%. The cross-polarisation level is /spl sim/-20 dB.

Broadband direct fed phased array antenna comprising stacked patches

Abstract: A broadband phased antenna is comprised of multiple patches which are dirly feed. The multiple patches provide the broadband patch antenna having overlapping narrow frequency bands and comprise a ground-plane element, multiple antenna elements, multiple dielectric layers, an RF feed line, and a feed arrangement. The ground-plane element has predetermined length and width dimensions and an aperture therein at a predetermined location near its center. The multiple antenna elements have an uppermost antenna element. The multiple dielectric layers are respectively interposed between and separate the multiple antenna elements into a stacked arrangement having odd and even numbered antenna elements.

Compact circularly polarised microstrip antenna with bent slots

Abstract: By embedding a group of four bent slots in a corner-truncated square microstrip patch, a single-feed compact circularly polarised microstrip antenna can easily be obtained. Results show that for a given circular polarisation (CP) operation, the proposed antenna can have an antenna size reduction of more than 50% as compared to the conventional CP design using a corner-truncated square patch without the slots. Moreover, the 50/spl Omega/ feed position and truncated-corner size for achieving CP operation are found to be nearly independent of the bent slots introduced in the patch, which makes the proposed antenna easy to implement.

Simple dual-frequency antenna

Abstract: An antenna construction comprises a feed conductor (11, 21) and an antenna element (12, 22, 24, 25, 26, 27) which has a first end and a second end. The feed conductor is substantially electrically unshielded and coupled to the antenna element at a tapping point (13, 23) located between the first end and second end of the antenna element, said tapping point dividing the antenna element into two portions having unequal electrical lengths. The antenna element may be a helix (12), a whip (22) or another known two-ended antenna element or a combination of those.

Integrated modified rectangular loop slot antenna on substrate lenses for millimeter- and submillimeter-wave frequencies mixer applications

Abstract: A coplanar waveguide (CPW)-fed rectangular-loop slot antenna with built-in tuning and DC-return capabilities on extended hemispherical lenses is examined. The proposed configuration is scalable up to the submillimeter-wave frequencies. For designing and analyzing the impedance characteristics of the proposed antenna, a multilayer method of moments (MoM) solver has been developed based on the mixed potential integral equation (MPIE) formulation. The corresponding patterns through the lens are obtained using geometrical optics and the surface equivalence principle. Three models have been simulated and one of them has been built and tested at 65 GHz. The integrated antenna exhibits tuning capability, rotationally symmetric patterns, high directivity, good Gaussian coupling efficiency, and a reasonable bandwidth. In addition, computed results agree well with measurements and are used to characterize the input impedance and pattern behavior of the antenna.

Microstrip antenna having a metal frame for control of an antenna lobe

Abstract: A device for and/or comprised in antennas, in particular microwave antennas such as microstrip antennas, for controlling the antenna lobe and completely or partially suppressing cross-coupling between the polarizations in dual-polarized antenna elements. A metal frame, the sides of which can be angled for a desired lobe width, is positioned around each antenna element on top of the ground plane of the antenna. The shape and positioning of the metal frame around the antenna element also control the antenna lobe. In this way, the antenna lobe can be controlled in the desired manner irrespective of the size of the ground plane of the antenna, which depends, for example, on a desired microstrip distribution network for the antenna.