Showing papers on "Coaxial antenna published in 2005"

Design of reconfigurable slot antennas

Abstract: In this paper the design of a compact, efficient and electronically tunable antenna is presented. A single-fed resonant slot loaded with a series of PIN diode switches constitute the fundamental structure of the antenna. The antenna tuning is realized by changing its effective electrical length, which is controlled by the bias voltages of the solid state shunt switches along the slot antenna. Although the design is based on a resonant configuration, an effective bandwidth of 1.7:1 is obtained through this tuning without requiring a reconfigurable matching network. Four resonant frequencies from 540-890 MHz are selected in this bandwidth and very good matching is achieved for all resonant frequencies. Theoretical and experimental behavior of the antenna parameters is presented and it is demonstrated that the radiation pattern, efficiency and polarization state of the antenna remain essentially unaffected by the frequency tuning

Band-notched UWB planar monopole antenna with two parasitic patches

Abstract: A novel ultra-wideband antenna with band elimination characteristic is presented, which has omnidirectional patterns in the E-plane and impedance bandwidth of about 3-18 GHz with VSWR below 2. The proposed antenna is fed by microstrip line, and consists of the monopole type with two parasitism-patches rejecting 5.15-5.825 GHz bandlimited by IEEE 802.11a and HIPERLAN/2.

Planar miniature tapered-slot-fed annular slot antennas for ultrawide-band radios

Abstract: A novel planar tapered-slot-fed annular slot antenna is proposed in this paper. The antenna utilizes a unique tapered-slot feeding structure and simultaneously possesses ultrawide bandwidth, almost uniform radiation patterns, and low profile. It is, hence, adequate for ultrawide-band (UWB) applications. By means of a normalized antenna transfer function, both frequency domain and time domain characteristics of the antenna are carefully investigated. Two measures, the uniformity related to the radiation patterns and the fidelity associated with the transient behaviors, are used to quantitatively describe the performance of an antenna over such an ultrawide bandwidth. Effects of varying the antenna's geometric parameters on the performance are then investigated. Finally, the influence of minimizing the antenna dimension is discussed at the end of the paper.

Circuit board having a peripheral antenna apparatus with selectable antenna elements

Abstract: A circuit board for wireless communications includes communication circuitry for modulating and/or demodulating a radio frequency (RF) signal and an antenna apparatus for transmitting and receiving the RF signal, the antenna apparatus having selectable antenna elements located near one or more peripheries of the circuit board. A first antenna element produces a first directional radiation pattern; a second antenna element produces a second directional radiation pattern offset from the first radiation pattern. The antenna elements may include one or more reflectors configured to provide gain and broaden the frequency response of the antenna element. A switching network couples one or more of the selectable elements to the communication circuitry and provides impedance matching regardless of which or how many of the antenna elements are selected. Selecting different combinations of antenna elements results in a configurable radiation pattern; alternatively, selecting several elements may result in an omnidirectional radiation pattern.

A compact and low-profile metamaterial ring antenna with vertical polarization

Abstract: A compact (/spl lambda//sub 0//11 footprint) and low-profile (/spl lambda//sub 0//28 height) metamaterial ring antenna is proposed using two metamaterial unit cells. Each constituent unit cell consists of negative-refractive-index (NRI) microstrip transmission lines (TL) designed to incur a zero insertion phase at the antenna design frequency. This allows the inductive posts to ground, which act as the main radiating elements, to be fed in phase. Hence, the antenna operates as two closely spaced monopoles that are fed in phase through a compact feed network. An embedded matching network ensures good VSWR performance. The theoretical performance of the antenna is verified by full-wave simulations and experimental data obtained from a fabricated prototype at 1.77 GHz. The antenna offers a 120 MHz -10 dB bandwidth and a measured efficiency exceeding 50%.

Dual polarization antenna and associated methods

Abstract: A dual polarization antenna includes a substantially pyramidal configured substrate having opposing walls An antenna element is carried at each wall such that opposing pairs of antenna elements define respective antenna dipoles and provide dual polarization

Low Q electrically small linear and elliptical polarized spherical dipole antennas

Abstract: Electrically small antennas are generally presumed to exhibit high impedance mismatch (high VSWR), low efficiency, high quality factor (Q); and, therefore, narrow operating bandwidth. For an electric or magnetic dipole antenna, there is a fundamental lower bound for the quality factor that is determined as a function of the antenna's occupied physical volume. In this paper, the quality factor of a resonant, electrically small electric dipole is minimized by allowing the antenna geometry to utilize the occupied spherical volume to the greatest extent possible. A self-resonant, electrically small electric dipole antenna is presented that exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and a quality factor that is within 1.5 times the fundamental lower bound at a value of ka less than 0.27. Through an arrangement of the antenna's wire geometry, the electrically small dipole's polarization is converted from linear to elliptical (with an axial ratio of 3 dB), resulting in a further reduction in the quality factor. The elliptically polarized, electrically small antenna exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and it has an omnidirectional, figure-eight radiation pattern.

Novel small-size directional antenna for UWB WBAN/WPAN applications

Abstract: This paper presents a novel small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications. The design is based on a typical slot antenna structure with an added reflector in order to achieve directionality. The effects of different antenna parameters and human body proximity on the radiation characteristics are analyzed. Antenna measurements with an optic RF setup were performed in order to characterize the small-size antenna far field radiation pattern. The different structural antenna parameters were optimized via extensive numerical simulations. Results show that for frequencies above 3.5 GHz, where the power front-to-back ratio of the directional antenna is greater than 10 dB, its impedance is nearly the same as in the free space. It is not the case neither for the omnidirectional slot antenna nor the monopole antenna next to the body. Between 3 and 6 GHz performance of the novel directional antenna, in terms of radiation efficiency and SAR values, is significantly improved compared to omnidirectional antenna designs.

Dual-band circularly polarized microstrip antenna for satellite applications

Abstract: This letter presents a dual-band circularly polarized patch antenna dedicated to satellite communications. The dual-band behavior is obtained by inserting a small X-band microstrip patch antenna into a large L-band one. Both patches are printed on the same substrate and fed by electromagnetic coupling through two perpendicular slots etched in their ground planes. These slots are fed by two different 90/spl deg/ microstrip branch-line couplers printed on a stacked lower substrate. A prototype of the antenna was realized with a 1.5-mm-thick upper layer substrate and a 0.758-mm-thick feed layer substrate, both of the same dielectric material with a relative permittivity of /spl epsiv//sub r/=2.22. Simulation and measurement results are presented, showing this compact dual-band antenna achieves the required Meteosat specifications in terms of frequency bandwidth, circular polarization bandwidth, and isolation between the two communication bands.

Ultra wideband monopole/dielectric resonator antenna

Abstract: A hybrid antenna is presented, consisting of an annular dielectric resonator antenna combined with a quarter-wave monopole to simultaneously act as a radiator and a loading element, producing an ultra wideband response. A prototype antenna is designed and a 3:1 bandwidth is demonstrated.

The design of a squarer-ring slot antenna for circular polarization

Abstract: A new design of a circularly polarized square-ring slot antenna is proposed. The circular polarization is achieved by a series microstrip-line-feed configuration coupling to two orthogonal sides of the square-ring slot. A parametric study is conducted using a commercial simulation software based on the method of moments, and the design procedure is established. The required ground-plane size of the proposed design for a given frequency is also indicated. Three antenna prototypes respectively operated at distinct frequency bands are constructed and measured for providing the simulation validation. Experimental results show that the proposed antenna has good circularly polarized radiations and the 3 dB axial-ratio bandwidth is more than 6%.

Method for steering a smart antenna for a wlan using a periodic re-scan

Abstract: A smart antenna steering algorithm performs a periodic re-scan at an end of a sustained use period and before a next sustained use period. During a sustained use period, a re-scan of the other antenna beams is not performed. The periodic re-scan is performed on alternate antenna beams that were selected when the preferred antenna beam was selected. The steering algorithm monitors a quality metric of the alternate antenna beams as well as a quality metric for the preferred antenna beam. If the quality metric of the preferred antenna beam is less than the quality metrics of anyone of the alternate antenna beams, then the alternate antenna beam corresponding to the quality metric having a higher value is selected for the next sustained use period.

A low profile single dipole antenna radiating circularly polarized waves

Abstract: A low profile single dipole antenna that can generate circularly polarized (CP) radiation patterns is proposed in this paper. The CP patterns and low profile configuration are achieved using a specially designed artificial ground plane: a thin grounded slab loaded with periodic rectangular patches. The artificial ground plane exhibits in-phase reflection coefficients with polarization-dependent feature. The radiation mechanism of the antenna is described, and experimental results verify the antenna concept.

Circular-polarization dipole helical antenna

Abstract: A circular-polarization dipole helical antenna is used for electronic device and satellite terminal and includes a base, and an antenna conductor arranged on surface of the base. The antenna conductor includes a plurality of metal conductors with high Q value and anti-oxidation property and continuously and helically coated on surface of the base. The base is made of low loss and high dielectric constant material. An unbalance-to-balance circuit module connects two signal-feeding ends to the base with phase difference of 180 degree. The problems of narrow bandwidth, low efficiency, complicated structure and precise manufacture can be solved.

Antenna in Package with Reduced Electromagnetic Interaction with on Chip Elements

Abstract: A IC package for a wireless device includes an antenna that is attached to the chip. The electrically conductive elements of the antenna are spaced away from the antenna and particularly the endpoint of the antenna to prevent interference with the antenna. An element on the IC package may be shielded antenna. The antenna may have the shape of a space-filling curve, including a Hilbert, box-counting or grid dimension curve.

Broadband RFID tag antenna with quasi-isotropic radiation pattern

Abstract: A passive RFID tag antenna in the UHF band using two bent dipoles and a modified double T-matching network is proposed. The antenna was fabricated with a thin copper layer printed on a 50 µm-thick PET substrate for low-cost production. The proposed antenna provided a quasi-isotropic radiation pattern and a fairly broad bandwidth S11<−10 dB, 8.5%) for conjugate-matching with a commercial tag chip. The efficiency of the antenna was about 90% in the operating frequency band. The measured readable range was between 170 –240 cm for an arbitrary rotation angle of the tag.

Micro-helix antenna and methods for making same

Abstract: A micro-helix antenna. The antenna comprises a helically-shaped conductive element disposed on a dielectric core. The diameter of the helix formed by the conductive element is very small relative to the wavelength of the antenna, preferably no more than about 1/100th of the wavelength. Having such a small diameter, this micro-helix antenna can be further compressed into two- and three-dimensional shapes, such as spirals, helices and meandering or stochastic patterns. The micro-helix antenna can be created by pressing a fine wire into a helical shape. Alternately, the helical conductor can be formed by a laser ablation process or laying down the helical shape using a direct-write process.

High-gain 1D EBG resonator antenna

Abstract: Theoretical and experimental results are presented for a high-gain electromagnetic bandgap (EBG) resonator antenna. This antenna uses a 1D EBG material made from low-dielectric-constant substrates, which results in a low-profile geometry. The operating frequency of the antenna is accurately predicted using dielectric multilayer theory. Theoretical results calculated using the FDTD method for the gain, directivity, return loss, efficiency, and radiation patterns are shown to be in good agreement with the measured performance of a test antenna. We also describe the behavior of the antenna as a function of frequency over the operating bandwidth, and examine the dependence of directivity on aperture size. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 107–114, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21095

System and apparatus for a wideband omni-directional antenna

Abstract: Embodiments generally relate to an antenna. The antenna includes at least two slot radiators, where each slot radiator has an input port and a profile that has been defined to optimize the return loss bandwidth of the antenna. The antenna also includes a transmission line and a circuit configured to connect the transmission line and the at least two slot radiators at the respective input ports. The circuit is also configured to match the impedance of the at least two slot radiators and the co-planar waveguide.

A compact antenna for ultrawide-band applications

Abstract: A novel compact and ultrawide-band (UWB) antenna is presented in this paper. The basis for achieving such an UWB operation is through proper magnetic coupling of two adjacent sectorial loop antennas in a symmetrical arrangement. A large number of coupled sectorial loop antennas (CSLA) with different geometrical parameters are fabricated and their measured responses are used to experimentally optimize the geometrical parameters of the antenna for achieving the maximum bandwidth. Through this optimization process an antenna with a VSWR of lower than 2.2 (S/sub 11/<-8.5 dB) across an 8.5:1 frequency range is designed. The maximum dimension of this antenna is smaller than 0.37/spl lambda//sub 0/ at the lowest frequency of operation and provides an excellent polarization purity. Furthermore, the antenna exhibits a relatively consistent radiation pattern. Modified versions of the CSLA are also designed to reduce the overall metallic surface and weight of the antenna while maintaining its wide-band characteristics. This allows modifying its dimensions to design low frequency light-weight UWB antennas.

Antenna array for an RFID reader compatible with transponders operating at different carrier frequencies

Abstract: An antenna array is provided for an RFID reader, which includes a first reader antenna tuned to operate at a first frequency and a second reader antenna tuned to operate at a second frequency different from the first frequency. The first and second antennas are preferably arranged in an overlapping arrangement or an opposing magnetic flux arrangement to reduce the effect of antenna self resonance.

Compact dual-band antenna with double L-slits for WLAN operations

Abstract: This letter presents a compact dual-band antenna with double L-slits for wireless local area network (WLAN) applications in IEEE 802.11a/b/g. The proposed antenna effectively covers both 2.4/5-GHz bands with three resonances that are caused by the double L-slits. The proposed antenna has compact size of 15 mm/spl times/9 mm/spl times/7 mm, which is only half size of the antenna using double U-slots. The parametric study is performed to understand the characteristics of the proposed antenna. The measured return loss and radiation patterns indicate the suitability of this antenna for the WLAN applications. The peak antenna gains of 1.3 dBi at 2.4-GHz band and 5.1 dBi at 5-GHz band are measured.

A hybrid-resonator antenna: experimental results

Abstract: Experimental results are presented for a hybrid-resonator antenna, consisting of a microstrip patch resonator coupled to a dielectric resonator. They demonstrate a 10 dB return-loss bandwidth of 5.14-6.51 GHz (23.5%) and a radiation pattern similar to that of a conventional microstrip patch or dielectric-resonator antenna. The peak cross-polarization level in the upper hemisphere is at least 18 dB below the peak co-polarization level.

Electrically small antenna elements using negative permittivity resonators

Abstract: We consider the use of materials with negative electric permittivity as a building block for constructing effective small antenna elements. In this paper, we show that negative permittivity alone is sufficient for constructing an effective small antenna element. Further, we clarify, here the issue of the radiation Q: a quasi-static analysis is used to show that a sub-wavelength spherical negative permittivity resonator will have a Q that is a factor of 3/2 above the Chu limit. We demonstrate through finite element simulation a practical antenna geometry composed of a coaxial transmission line coupled to a half-sphere of negative permittivity adjacent to a ground plane. The resonator is impedance-matched to the transmission line, resulting in an antenna Q matching that predicted by the quasi-static analysis.

Theoretical investigation of a circular patch antenna in the presence of a left-handed medium

Abstract: The influence of a left-handed medium (LHM) on the performances of a circular patch antenna is quantified numerically. For this, a homogenization procedure of the LHM is carried out in order to design the patch antenna at a suitable frequency where the losses of the LHM are low. From the first results obtained, it is noted that in the presence of the LHM, the antenna is more directive and has a higher gain.

Wide-band modified printed bow-tie antenna with single and dual polarization for C - and X-band applications

Abstract: A modified printed bow-tie antenna is designed to simultaneously cover the operations in the C and X-bands from 5.5 to 12.5 GHz. The presented antenna has an end fire radiation pattern that makes it suitable for integration in single and dual polarized phased array systems. The antenna exhibits small size and wide bandwidth of 91%. The radiation characteristics are presented for a single element and a linear array of this antenna.

60-GHz CPW-fed post-supported patch antenna using micromachining technology

Abstract: A 60-GHz coplanar waveguide (CPW)-fed post-supported patch antenna is presented using micromachining technology. In the proposed structure, the radiating patch and the feed line network can be optimized separately with a substrate. The antenna performance is improved by elevating the patch in the air. A patch array antenna is also designed with a simple feed network. The fabricated antenna shows broad band characteristics such as -10 dB bandwidth of 4.3GHz from 58.7GHz to 64.5GHz in the single patch antenna and 8.7GHz from 56.3GHz to 65GHz in 2/spl times/1 patch array antenna.

Antenna Modeling by Infinitesimal Dipoles Using Genetic Algorithms

Abstract: The binary Genetic Algorithm (GA) optimization method is used to simulate antennas from their near-field distribution by a set of infinitesimal dipoles. The infinitesimal dipoles could be of electric and/or magnetic types that produce the near field of the actual antenna and thus the same far field. The method is verified using near fields from known infinitesimal electric and/or magnetic dipoles. Some simple antennas have been simulated by infinitesimal dipoles such as dipole, loop, waveguide, and dielectric resonator antenna. The obtained equivalent dipoles from single frequency measurements are found to be valid for certain frequency band.

Dual-band CPW-fed Y-shaped monopole antenna for PCS/WLAN application

Abstract: A rectangular notch is introduced to expand the impedance bandwidth of a dual-band planar monopole antenna for application in PCS/WLAN systems. The antenna is fed by a CPW line and resembles the shape of the letter ‘Y’. Prototypes of the proposed antenna have been constructed and tested. Good measured radiation characteristics of monopole-like patterns, 14.4 and 34.1% bandwidths, and 3 and 4.3 dBi peak antenna gains for the lower (1.95 GHz) and upper (5.45 GHz) bands have been obtained.