Showing papers on "Patch antenna published in 1999"

Aperture-coupled patch antenna on UC-PBG substrate

Abstract: The recently developed uniplanar compact photonic bandgap (UC-PBG) substrate is successfully used to reduce surface-wave losses for an aperture-coupled fed patch antenna on a thick high dielectric-constant substrate. The surface-wave dispersion diagram of the UC-PBG substrate has been numerically computed for two different substrate thickness (25 and 50 mil) and found to have a complete stopband in the frequency range of 10.9-13.5 and 11.4-12.8 GHz, respectively. The thicker substrate is then used to enhance broadside gain of a patch antenna working in the stopband at 12 GHz. Computed results and measured data show that, due to effective surface-wave suppression, the antenna mounted on the UC-PBG substrate has over 3-dB higher gain in the broadside direction than the same antenna etched on a grounded dielectric slab with same thickness and dielectric constant. Cross-polarization level remains 13 dB down the co-polar component level for both E- and H-planes.

Enhanced Patch-Antenna Performance by Suppressing Surface Waves Using

Abstract: The microstrip patch antenna is a low-profile robust planar structure. A wide range of radiation patterns can be achieved with this type of antenna and, due to the ease of man- ufacture, is inexpensive compared with other types of antennas. However, patch-antenna designs have some limitations such as restricted bandwidth of operation, low gain, and a potential decrease in radiation efficiency due to surface-wave losses. In this paper, a photonic-bandgap (PBG) substrate for patch antennas is proposed, which minimizes the surface-wave effects. In order to verify the performance of this kind of substrate, a configuration with a thick substrate is analyzed. The PBG patch antenna shows significantly reduced levels of surface modes compared to conventional patch antennas, thus improving the gain and far-field radiation pattern.

Enhanced patch-antenna performance by suppressing surface waves using photonic-bandgap substrates

Abstract: The microstrip patch antenna is a low-profile robust planar structure. A wide range of radiation patterns can be achieved with this type of antenna and, due to the ease of manufacture, is inexpensive compared with other types of antennas. However, patch-antenna designs have some limitations such as restricted bandwidth of operation, low gain, and a potential decrease in radiation efficiency due to surface-wave losses. In this paper, a photonic-bandgap (PBG) substrate for patch antennas is proposed, which minimizes the surface-wave effects. In order to verify the performance of this kind of substrate, a configuration with a thick substrate is analyzed. The PBG patch antenna shows significantly reduced levels of surface modes compared to conventional patch antennas, thus improving the gain and far-field radiation pattern.

Directive photonic-bandgap antennas

Abstract: This paper introduces two new photonic bandgap (PBG) material applications for antennas, in which a photonic parabolic reflector is studied. It is composed of dielectric parabolic layers associated to obtain a PBG material. The frequency gap is used to reflect and focus the electromagnetic waves. This device has been designed using a finite-difference time-domain (FDTD) code. FDTD computations have provided the theoretical reflector's directivity. These results are in good agreement with measurements, and it appears that the PBG reflector presents the same directivity as a metallic parabola. A second application uses a defect PBG material mode associated with a metallic plate to increase the directivity of a patch antenna. We explain the design of such a device and propose experimental results to validate the theoretical analysis.

Patch antennas on externally perforated high dielectric constant substrates

Abstract: Smaller physical size and wider bandwidth are two antenna engineering goals of great interest in the wireless world. To this end, the concept of external substrate perforation is applied to patch antennas in this paper. The goal was to overcome the undesirable features of thick and high dielectric constant substrates for patch antennas without sacrificing any of the desired features, namely, small element size and bandwidth. The idea is to use substrate perforation exterior to the patch to lower the effective dielectric constant of the substrate surrounding the patch. This change in the effective dielectric constant has been observed to help mitigate the unwanted interference pattern of edge diffraction/scattering and leaky waves. The numerical data presented in this paper were generated using the finite-difference time-domain (FDTD) technique. Using this numerical method, a patch antenna was simulated on finite-sized ground planes of two different substrate thicknesses, with and without external substrate perforation. The computations showed the directivity drop in the radiation pattern caused by substrate propagation was noticeably improved by introducing the substrate perforation external to the patch for the case of a patch antenna on a relatively thick substrate without any loss of bandwidth. Measurements of a few patch antennas fabricated on high dielectric constant substrates with and without substrate perforation are included for completeness. Good correlation between the computed results and measurements is observed.

Printed twin spiral dual band antenna

Abstract: The present invention overcomes the above-identified deficiencies in the art by providing a miniature, built-in dual band antenna which is suitable for use in future compact mobile terminals. According to exemplary embodiments, a built-in antenna is provided which includes two spiral conductor arms which are of different lengths and capable of being tuned to different frequency bands. The spiral arms are mounted on 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 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.

Cross-slot-coupled microstrip antenna and dielectric resonator antenna for circular polarization

Abstract: Circular polarization (CP) design of microstrip antennas and dielectric resonator (DR) antennas through a cross slot of unequal slot lengths in the ground plane of a microstrip line is demonstrated. The proposed CP design is achieved by choosing a suitable size of the coupling cross slot, which results in the excitation of two near-degenerate orthogonal modes of near-equal amplitudes and 90/spl deg/ phase difference. This CP design can be applied to both configurations of microstrip antennas and DR antennas and has the advantages of easy fine-tuning and less sensitivity to the manufacturing tolerances, as compared to their respective conventional single-feed CP designs. For the proposed design applied to a low-profile circular disk DR antenna of very high permittivity studied here, a large CP bandwidth, determined from 3-dB axial ratio, as high as 3.91% is also obtained. Details of the proposed antenna designs are described, and experimental results of the CP performance are presented and discussed.

Genetic algorithms and method of moments (GA/MOM) for the design of integrated antennas

Abstract: This paper introduces a novel technique for efficiently combining genetic algorithms (GAs) with method of moments (MoM) for integrated antenna design and explores a two example applications of the GA/MoM approach. Integral to efficient GA/MoM integration is the use of direct Z-matrix manipulation (DMM). In DMM a "mother" structure is selected and its corresponding impedance or Z-matrix is filled only once prior to beginning the GA optimization process. The GA optimizer then optimizes the design by creating substructures of the mother structure as represented by the corresponding subsets of the original mother Z-matrix. Application of DMM with GA/MoM significantly reduces the total optimization time by eliminating multiple Z-matrix fill operations. DMM also facilitates the use of matrix partitioning and presolving to further reduce the optimization time in many practical cases. The design of a broad-band patch antenna with greater than 20% bandwidth and a dual-band patch antenna are presented as examples of the utility of GA/MoM with DMM. Measured results for the dual-band antenna are compared to numerical results. Excellent agreement between numerical and measured results is observed.

A shaped-beam microstrip patch reflectarray

Abstract: This paper describes a microstrip reflectarray antenna designed to produce a shaped-beam coverage pattern using phase synthesis. The concept is demonstrated with a Ku-band linearly polarized reflectarray designed to provide coverage of the European continent and measured results are compared to those obtained for a previously designed shaped-reflector antenna designed for the same coverage specifications. Results validate the shaped-beam reflectarray concept, although there are disadvantages to the reflectarray such as narrow bandwidth and reduced aperture efficiency that may offset the mechanical and cost advantages of the flat surface of the reflectarray.

Harmonic control by photonic bandgap on microstrip patch antenna

Abstract: In this work, the single microstrip patch antenna having two-dimensional photonic bandgap (PBG) in the ground has been demonstrated experimentally, and the effectiveness of the PBG structure is discussed for the suppression of the resonance at the harmonic frequencies of the antenna. Experimental results indicate that the radiation patterns at the harmonic frequencies can be drastically diminished comparing with the normal microstrip patch antenna without the PBG structure. For instance, the radiation to the forward of the PBG antenna is suppressed at more than 15 dB at the third harmonic frequency.

Design of probe-fed stacked patches

Abstract: In this paper, a design strategy to achieve bandwidths in excess of 25% for probe-fed stacked patches is presented. The choice of appropriate dielectric materials for such bandwidths is given and the role of each antenna parameter in controlling the impedance behavior is provided. It has been found that the selection of the substrate below the lower patch plays a major role in producing broad-band responses. A simple design procedure is outlined and this technique is verified experimentally. The findings presented here can be applied to all types of probe-fed stacked patches as well as edge-fed and cavity-backed configurations.

Design of nonplanar microstrip antennas and transmission lines

Abstract: Introduction and Overview. Resonance Problem of Cylindrical Microstrip Patches. Resonance Problem of Spherical Microstrip Patches. Characteristics of Cylindrical Microstrip Antennas. Characteristics of Spherical and Conical Microstrip Antennas. Coupling between Conformal Mircostrip Antennas. Conformal Microstrip Arrays. Cylindrical Microstrip Lines and Coplanar Waveguides. Appendices. Index.

Directional coupler, antenna device, and transmitting - receiving device

Abstract: A first transmission line and a second transmission line are caused to be partially opposite to each other, and by use of the opposite portions of the first transmission line and the second transmission line, the first transmission line and the second transmission line are relatively shifted in parallel from their opposite state to their non-opposite state.

Stacked patches using high and low dielectric constant material combinations

Abstract: In this paper, the performance of stacked patches incorporating a high and low dielectric constant material combination is presented. Such a printed antenna is applicable for cases where photonic and microwave devices need to be directly integrated with the antenna. It is shown that 10-dB return-loss bandwidths in excess of 25% can be achieved with such a configuration. Importantly, the surface wave efficiency across this band of frequencies is high-greater than 85%. It is also shown that these stacked patches have lower cross-polarization levels compared to a conventional stacked patch and, thus, are very suited to circular polarization applications. Two circular polarization (CP) configurations are presented and experimentally verified. The single- and dual-feed configurations have 3-dB axial ratio bandwidths of 18% and 32%, respectively.

A microstrip patch antenna using novel photonic band-gap structures

Abstract: Printed antennas exemplified by the microstrip patch antenna offer an attractive solution to compact, conformal and low cost design of modem wireless communications equipment, RF sensors and radar systems. Recent applications have pushed the frequency well into the ram-wave region even in the commercial arena as evidenced by the worldwide race to develop advanced collision warning radar systems for automobiles at the 76 GHz band.[1] Microstrip-based planar antennas fabricated on a substrate with a high dielectric constant (Si, GaAs and InP) are strongly preferred for easy integration with the MMIC RF front-end circuitry. However, it is well known that patch antennas on high dielectric constant substrates are highly inefficient radiators due to surface wave losses and have very narrow frequency bandwidth (approximately one to two percent). This situation becomes extremely severe as applications move to higher frequencies, resulting in patch antennas with reduced gain and efficiency as well as an unacceptably high level of cross polarization and mutual coupling within an array environment. Therefore, much effort has been made recently to realize high efficiency patch antennas on high permittivity substrates, including using the latest micromachining technology.[2,3]

Radio frequency tag with miniaturized resonant antenna

Abstract: An RF transponder is provided with a miniature resonant antenna that can fit on a small form factor the size of a button or coin. More particularly, the RF transponder comprises a substrate and an RF integrated circuit disposed thereon. An antenna is provided on the substrate and is electrically connected to the RF integrated circuit. The antenna has a contorted shape that permits it to fit into the limited available space on the substrate, while having an electrical length that is greater than a maximum length dimension of the substrate. Possible shapes for the antenna may include a meander antenna, a non-uniform meander antenna, a bent dipole antenna, a spiral antenna, a z-shaped dipole, a squeezed dipole antenna, or a combination of any of the antenna types. The RF transponder may further include at least one loading bar spaced from the antenna and/or at least one tuning stub coupled to the antenna.

On the circular polarization operation of annular-ring microstrip antennas

Abstract: Circular polarization (CP) operation of an annular-ring microstrip antenna with a pair of inserted slits at its fundamental TM/sub 11/ mode is proposed and experimentally investigated. Two examples of the proposed antenna fed using a microstrip line at the inner and outer patch boundaries are studied. Results show that the proposed antenna can have good CP performance and, moreover, the required antenna size at a fixed CP operation can be much less than that of a conventional circularly polarized circular microstrip antenna operated at the TM/sub 11/ mode. Details of the proposed antenna for CP operation are described and experimental results of the CP performance are presented and discussed.

Single-feed slotted equilateral-triangular microstrip antenna for circular polarization

Abstract: Novel designs of single-feed equilateral-triangular microstrip antennas for circular polarization (CP) are proposed and studied experimentally. It is demonstrated that by embedding a narrow slot or a cross slot of unequal slot lengths in the triangular patch, circularly polarized radiation of microstrip antennas can easily be achieved using a single probe feed. Furthermore, results show that for the design with a cross slot, the proposed antenna can perform CP radiation with a reduced antenna size at a given frequency (denoted as compact CP operation here); that is, the required antenna size is smaller for the proposed antenna for performing CP radiation as compared to a conventional circularly polarized triangular microstrip antenna at a fixed operating frequency. Details of the proposed CP designs are described, and typical experimental results are presented and discussed.

Integrated-antenna push-pull power amplifiers

Abstract: In this paper, the integrated-antenna concept is applied to push-pull power amplifiers (PAs). In this approach, the antenna serves as an out-of-phase power combiner and tuned load for higher harmonics. This new architecture effectively has a near-zero loss output hybrid, and results in a high-efficiency PA. The first example is a narrow-band push-pull amplifier integrated with a dual-feed patch antenna. At an operating frequency of 2.5 GHz, a maximum measured power-added efficiency (PAE) of 55% is achieved. The second example is a broadband push-pull amplifier integrated with a dual-feed slot antenna amplifier operating at 2.46 GHz which has a peak PAE of 63%, and PAE better than 55% in an 8% bandwidth. Additionally, 48% PAE is achieved with code-division multiple-access modulation and adjacent-channel power ratio better than -42 dBe at a 1.25-MHz offset.

Magnetic resonance antenna

Abstract: A magnetic resonance antenna has at least five antenna elements, each of, which extends essentially radially from an inner element beginning to at least one outer element end with respect to a center axis. The antenna elements are at least magnetically coupled with one another.

Characteristics of single- and double-layer microstrip square-ring antennas

Abstract: A method for miniaturization of microstrip patch antennas without degrading radiation characteristics is investigated. It involves perforating the patch to form a microstrip square-ring antenna, which is investigated numerically and experimentally. The ring geometry introduces additional parameters to the antenna that can be used to control its impedance, resonance frequency, and bandwidth. For a single square ring increasing the size of perforation increases its input impedance, but decreases the resonance frequency and bandwidth. It has a small effect on directivity of the antenna. To match the antenna to a transmission line and also enhance its bandwidth, the ring is stacked by a square patch or another square ring. The computed results are compared with experimental data and again good agreement is obtained.

Microstrip patch antenna

Abstract: An integrated directional patch antenna uses multiple patch radiating elements to control the direction of a beam of radio frequency energy (RF) over a large scan volume. The antenna includes a ground plane element and a first dielectric planar member placed on a major surface of the ground plane element. A plurality of first patch radiator elements is arranged on a surface of the first dielectric member remote from the ground plane element. A second dielectric planar member is placed on first patch radiator elements, and a plurality of second patch radiator elements arranged on a surface of the second dielectric member remote from the first patch radiator elements. First regions are formed in the dielectric planar member that have a first dielectric constant and are separated from each other by second regions that have a dielectric constant different from the first dielectric constant to effectively prevent surface wave energy from propagating in the first dielectric planar member, thereby increasing the scan volume of the antenna.

Dual band antenna for radio terminal

Abstract: A dual band antenna for a radio terminal consists of a retractable whip antenna (10) and a helical antenna (30) with irregular pitches, wherein the whip antenna (10) is independent of the helical antenna (30). The helical antenna (30) includes first and second helical portions (35) having first and second pitches, respectively and the first and second helical portions (35) are operable at different frequency bands independently. The whip antenna (10) includes a conductive core line (12), a conductive substance (13) covering a first portion of the conductive core line (12) to serve as a choke and an isolation element extending from an upper end of the conductive core line (12), for filling a gap between the conductive core line (12) and the conductive substance (13). Here, only the first portion of the conductive core line is operable at a first frequency band and the entire conductive core line (12) is operable at a second frequency. A fixing element (40) fixes the helical antenna (30) and the whip antenna (10) to the radio terminal (60). The fixing element (40) has an upper end connected to a lower end of the helical antenna (30) and a through hold via which the whip antenna (10) is inserted into an interior of the radio terminal (60).

Thin dual-resonant stacked shorted patch antenna for mobile communications

Abstract: A novel thin stacked shorted patch antenna for the 1800 MHz frequency band is presented. The antenna is dual-resonant and small in size. It has a very low profile and a bandwidth of almost 10%, which is sufficient, for example, for GSM1800 or GSM1900 systems. The radiation pattern of the antenna is suitable for directive cellular handset antenna applications.

A 94-GHz aperture-coupled micromachined microstrip antenna

Abstract: This paper presents 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 -18 dB at 94 GHz for a 10-dB bandwidth of 10%. A maximum efficiency of 58/spl plusmn/5% has been measured and the radiation patterns show a measured front-to-back ratio of -10 dB at 94 GHz. The measured mutual coupling is below -20 dB in both E- and H-plane directions due to the integration of small 50-/spl mu/m silicon beams between the antennas. The micromachined microstrip antenna is an efficient solution to the vertical integration of antenna arrays at millimeter-wave frequencies.

Neural computation of resonant frequency of electrically thin and thick rectangular microstrip antennas

Abstract: A method for calculating the resonant frequency of electrically thin and thick rectangular microstrip antennas, based on the backpropagation multilayered-perceptron network, is presented. The method can be used for a wide range of substrate thicknesses and permittivities, and is useful for the computer-aided design (CAD) of microstrip antennas. The calculated resonant-frequency results are in very good agreement with the experimental results reported elsewhere.

A method for designing broad-band microstrip antennas in multilayered planar structures

Abstract: The narrow bandwidth of a microstrip antenna is one of the important features that restrict its wide usage. A simple and practical method for the design of broad-band microstrip antennas is presented in this paper. Utilizing this design technique, several two-layer microstrip antennas have been proposed. To confirm the applicability of the method for the designs of antennas at L-band, experiments have been carried out. The measured results show that the proposed antennas have a bandwidth of up to 25.7%. Also, the method proposed in this paper is applicable to the design of other types of multilayered planar antennas.

Directional reflector shield assembly for a microwave ablation instrument

Abstract: A directional reflective shield assembly (25) is provided for a microwave ablation instrument (20) having an antenna (23) coupled to a transmission line (21). The antenna (23) is formed to generate an electric field sufficiently strong to cause tissue ablation. The shield assembly (25) includes a cradle device (26) disposed about the antenna (23) in a manner substantially shielding a surrounding area of the antenna (23) from the electric field radially generated therefrom. The cradle device (26) further provides a window portion (27) communicating with the antenna (23) which is strategically located relative the antenna to direct a majority of the field generally in a predetermined direction.

Antenna device and radio device comprising the same

Abstract: The invention provides An antenna device, comprising: a substrate made of an insulation material and including a first major surface and a second major surface face; a ground electrode provided substantially on the whole of the first major surface of said substrate; and an inverted F-shape antenna and a microstrip antenna respectively provided on the surface of the substrate. An open end of a radiation electrode of the microstrip antenna and a feeding electrode of the inverted F-shape antenna are capacitively coupled to each other. A first direction through the open end and ground end of the radiation electrode of the inverted F-shape antenna is substantially perpendicular to a second direction through the open end and ground end of the radiation electrode of the microstrip antenna. By the above arrangement, a mutual interference hardly occurs between the two antennas.

Design and characterization of single and multiple beam MM-wave circularly polarized substrate lens antennas for wireless communications

Abstract: We present the design of single and multiple beam circularly polarized (CP) substrate lens antennas for wireless applications at 30 GHz. Circular polarization and high directivity are desirable features as they can effectively reduce multipath effects and maintain a proper link margin. In addition, multiple beam antennas can be utilized either for space division multiple access (SDMA) or for incorporating "smart" antenna features. The approach taken is to use an aperture coupled patch antenna as the lens feed in combination with low-cost plastic materials for making the lens. For the single-beam design, an ellipsoidal lens is utilized which leads to diffraction limited patterns on-axis. For the multiple-beam design, we choose a hexagonal arrangement of printed patch elements at the back of the lens to maximize scan coverage. Also, the extension length of the ellipsoidal lens is optimized to launch beams with roughly equal power densities.