Showing papers on "Dipole antenna published in 2007"

Methods and Apparatuses for Adaptively Controlling Antenna Parameters to Enhance Efficiency and Maintain Antenna Size Compactness

Abstract: An antenna for a communications device having configurable elements controlled to modify an antenna impedance and/or an antenna resonant frequency to improve performance of the communications device The antenna impedance is controlled to substantially match to an output impedance of a power amplifier that supplies the antenna with a signal for transmission The antenna resonant frequency is controlled to overcome the effects of various operating conditions that can detune the antenna or in response to an operable frequency band

Small Printed Ultrawideband Antenna With Reduced Ground Plane Effect

Abstract: A small printed antenna is described with a reduced ground-plane effect for ultrawideband (UWB) applications. The radiator and ground plane of the antenna are etched onto a piece of printed circuit board (PCB) with an overall size of 25mmtimes25 mmtimes1.5 mm. A notch is cut from the radiator while a strip is asymmetrically attached to the radiator. The simulation and measurement show that the miniaturized antenna achieves a broad operating bandwidth of 2.9-11.6 GHz for a 10-dB return loss. In particular, the ground-plane effect on impedance performance is greatly reduced by cutting the notch from the radiator because the electric currents on the ground plane are significantly suppressed at the lower edge operating frequencies. The antenna features three-dimensional omni-directional radiation with high radiation efficiency of 79%-95% across the UWB bandwidth. In addition, a parametric study of the geometric and electric parameters of the proposed antenna will be able to provide antenna engineers with more design information

Frequency Diverse Array Antenna with Periodic Time Modulated Pattern in Range and Angle

Abstract: A general analysis of a frequency diverse transmit array antenna with a periodic modulated pattern in range, angle and time is presented. This antenna array system makes a continuous scanning in range and angle without using any phase shifters. The scanning is achieved using the frequency diversity by inserting a small amount of progressive frequency shift to each antenna element. The theory shows that there is the same modulation pattern in time, range and angle by taking the remaining two parameters fixed. The simulation results for radiation patterns of a binomial distribution array are presented. The expressions for determining the position and the angular bearing of a target for this type of antenna array system are given.

A Novel Dual-Band Printed Diversity Antenna for Mobile Terminals

Abstract: A novel dual-band printed diversity antenna is proposed and studied. The antenna, which consists of two back-to- back monopoles with symmetric configuration, is printed on a printed circuit board. The effects of some important parameters of the proposed antenna are deeply studied and the design methodology is given. A prototype of the proposed antenna operating at UMTS (1920-2170 MHz) and 2.4-GHz WLAN (2400-2484 MHz) bands is provided to demonstrate the usability of the methodology in dual-band diversity antenna for mobile terminals. In the above two bands, the isolations of the prototype are larger than 13 dB and 16 dB, respectively. The measured radiation patterns of the two monopoles in general cover complementary space regions. The diversity performance is also evaluated by calculating the envelope correlation coefficient, the mean effective gains of the antenna elements and the diversity gain. It is proved that the proposed antenna can provide spatial and pattern diversity to combat multipath fading.

Printed Monopole Slot Antenna for Internal Multiband Mobile Phone Antenna

Abstract: A new internal multiband mobile phone antenna formed by two printed monopole slots of different lengths cut at the edge of the system ground plane of the mobile phone is presented. The antenna can generate two wide bands centered at about 900 and 2100 MHz to cover the GSM850/GSM900/DCS/PCS/UMTS bands and the 2.4-GHz WLAN band. Further, the antenna has a simple planar structure and occupies a small area of only. It is also promising to bend the antenna into an L shape to reduce its volume occupied inside the mobile phone. Good radiation characteristics are obtained over the two wide operating bands.

Babinet’s principle for optical frequency metamaterials and nanoantennas

Abstract: We consider Babinet's principle for metamaterials at optical frequencies and include realistic conditions which deviate from the theoretical assumptions of the classic principle such as an infinitely thin and perfectly conducting metal layer. It is shown that Babinet's principle associates not only transmission and reflection between a structure and its complement but also the field modal profiles of the electromagnetic resonances as well as effective material parameters\char22{}a critical concept for metamaterials. Also playing an important role in antenna design, Babinet's principle is particularly interesting to consider in this case where the metasurfaces and their complements can be regarded as variations on a folded dipole antenna array and patch antenna array, respectively.

Carbon Nanotubes as Optical Antennae

Abstract: Light scattering from an array of aligned multiwall carbon nanotubes (MWCNTs) has previously been investigated, and shown to be consistent with that from an array of antennae. Two basic antenna effects have been demonstrated: 1) the polarization effect, which suppresses the response of an antenna when the electric field of the incoming radiation is polarized perpendicular to the dipole antenna axis, and 2) the antenna-length effect, which maximizes the antenna response when the antenna length is a multiple of the radiation half wavelength in the medium surrounding the antenna. In these previous experiments a random nanotube array was chosen to eliminate the intertube diffraction effects. In this communication, we provide compelling evidence of the antenna action of an MWCNT, by demonstrating that its directional radiation characteristics are in an excellent and quantitative agreement with conventional radio antenna theory and simulations. According to conventional radio antenna theory, a simple “thin” wire antenna (a metallic rod of diameter d and length l >> d) maximizes its response to a wavelength k when l = mk/2, where m is a positive integer. Thus, an antenna acts as a resonator of the external electromagnetic radiation. An antenna is a complex boundary value problem; it is a resonator for both the external fields, and the currents at the antenna surface. In a long radiating antenna, a periodic pattern of current distribution is excited along the antenna, synchronized with the pattern of fields outside. The current pattern consists of segments, with the current direction alternating from segment to segment. Thus, a long antenna can be viewed as an antenna array consisting of smaller, coherently driven antennae (segments) in series. Therefore, the resulting radiation pattern, as a function of the angle with respect to the antenna axis, consists of lobes of constructive interference, separated by radiation minima due to destructive interference. Consider a simple antenna as shown in Figure 1a. The radiation pattern produced by this antenna is rotationally symmetric about the z axis. For a center-fed antenna, or one excited by an external wave propagating perpendicular to the antenna axis (i.e., with the glancing angle hi = 90°), the pattern is also symmetric with respect to the x–y plane. For an antenna excited by an incoming wave propagating at an angle (hi < 90°), the relative strengths of the radiation lobes are expected to shift towards the specular direction. This follows from a qualitative argument based on the single-photon scattering picture, and conservation laws for scattered photons from an antenna. Since such scattering is elastic, the energy of each scattering photon x (where is the reduced Planck constant and x is the angular frequency) and its total momentum k = ki= ks (where k is the wave number, ki is the incident wave vector, and ks is the scattered wave vector) must be conserved. Due to the cylindrical symmetry, K, the length of the momentum vector component perpendicular to the antenna, must also be conserved. Thus, the momentum components parallel to the antenna for the incoming, and scattered photons, k (s) and k (i) respectively, satisfy the following condition k (i) = k 2 – K = k (s), or finally k (s) = ±k (i). This immediately leads to a formula for the angle of scattering hs = 180° – hi, since for a “thin” antenna with diameter d << l, the back scattering is suppressed, and therefore the negative sign is unlikely. Thus, scattering is dominated by the specular reflection. We have confirmed this effect, by measuring the scattered microwave radiation from a simple wire antenna; the forward radiation was about one order of magnitude more intense than for the backward scattered wave. To complete the preliminary antenna studies, we performed computer simulations of the detailed antenna response to an external plane wave. Figure 1b shows a polar coordinate plot of the radiation pattern (field intensity versus h), in the y–z plane, from a thin antenna (d = 0.001l) with l = 7k. The incoming wave of fixed wavelength k, struck the antenna at different incidence angles hi = 30°, 45°, and 60°. This produced radiation patterns dominated by lobes at hs = 180 – hi = 150°, 135°, and 120°, respectively: the scattering was dominated by the specular reflection with respect to the 90° line, in agreement with the simple analysis above. Due to cylindrical symmetry in the x–y plane, the response was mirror-image symmetric about the z axis in the x–z plane. The dependence of C O M M U N IC A IO N

Design of a Planar Ultrawideband Antenna With a New Band-Notch Structure

Abstract: A novel planar ultrawideband (UWB) antenna with band-notched function. The antenna consists of a radiation patch that has an arc-shaped edge and a partially modified ground plane. The antenna that makes it different from the traditional monopole antenna is the modification in the shape of ground plane, including two bevel slots on the upper edge and two semicircle slots on the bottom edge of the ground plane. These slots improve the input impedance bandwidth and the high frequency radiation performance. With this design, the return loss is lower than 10 dB in 3.1-10.6 GHz frequency range and the radiation pattern is highly similar to the monopole antenna. By embedding a pair of T-shaped stubs inside an elliptical slot cut in the radiation patch, a notch around 5.5 GHz WLAN band is obtained. The average gain is lower than -18 dBi in the stopband, while the patterns and the gains at frequencies other than in the stopband are similar to that of the antenna without the band-notched function.

Forward throw antenna utility meter

Abstract: Systems and methods are provided for a utility meter assembly comprising: a plurality of meter components configured for measuring and collecting data, wherein the meter components include a transceiver operative for signal communications over a network; a faceplate, configured such that meter reading information is displayed on the front of the faceplate; an exterior cover configured to enclose the meter components and the faceplate, wherein the faceplate is forward of the plurality of meter components; and an internal dipole antenna situated within the exterior cover, wherein the internal dipole antenna is beyond the front of the faceplate and toward the front of the utility meter assembly. The internal dipole antenna is typically situated away from the meter components, so as to minimize interference by the meter components. The internal dipole antenna is typically tuned for optimal matching impedance in an 850 MHz or 1900 MHz receiving band, so that the desired receiving band Standing Wave Ration (SWR) is achieved, and also a specified minimum radiated power threshold is maintained.

Electrically small split ring resonator antennas

Abstract: We studied electrically small resonant antennas composed of split ring resonators (SRR) and monopoles The antennas considered have the same ring radius, but slightly different geometry The resonance frequency depends on the geometry of the SRRs Two SRR antennas are designed The first one, which operates at 362 GHz, is demonstrated theoretically and experimentally The size of this antenna is 0095λ0×0100λ0 and is low profile at the other dimension The gain and directivity of the antenna was 238 and 546, respectively The corresponding efficiency was 436% The estimated radiation Q (rad Q=2303) was much larger than the minimum radiation Q (min Q=178) The second one is a rather small SRR antenna in which the capacitance between the rings is increased The size is reduced to 0074λ0×0079λ0 This structure is called serrated SRR (SSRR) Both antennas have similar far-field patterns but the efficiency of the SSRR antenna is less

Communication Using Antennas Fabricated in Silicon Integrated Circuits

Abstract: The feasibility of integrating compact antennas and required circuits for implementing wireless interconnections in foundry digital CMOS technologies has been demonstrated. A 3-mm long zigzag dipole antenna on a 20-Omega-cm substrate should have efficiency up to approximately 25% at 24 GHz and cost 1-2 cents. These antennas can be used to implement a radio for 100-kb/s communication up to about 10 m. By lowering the operation frequency to 5.8 GHz and using a monopole structure, which occupies approximately 30% more area, the communication range can be increased by three times or more. This technology, as well as in a true single-chip radio, can be used for intra- and inter-chip data communication, intra- and inter-chip clock distribution, beacons, radars, RFID tags, and contactless high-frequency testing.

Reconfigurable Square-Ring Patch Antenna With Pattern Diversity

Abstract: A single-feed reconfigurable square-ring patch antenna with pattern diversity is presented. The antenna structure has four shorting walls placed respectively at each edge of the square-ring patch, in which two shorting walls are directly connected to the patch and the others are connected to the patch via pin diodes. By controlling the states of the pin diodes, the antenna can be operated at two different modes: monopolar plat-patch and normal patch modes; moreover, the 10 dB impedance bandwidths of the two modes are overlapped. Consequently, the proposed antenna allows its radiation pattern to be switched electrically between conical and broadside radiations at a fixed frequency. Detailed design considerations of the proposed antenna are described. Experimental and simulated results are also shown and discussed

Simple Broadband Planar CPW-Fed Quasi-Yagi Antenna

Abstract: In this letter, we present a novel coplanar waveguide fed quasi-Yagi antenna with broad bandwidth. The uniqueness of this design is due to its simple feed selection and despite this, its achievable bandwidth. The 10 dB return loss bandwidth of the antenna is 44% covering X-band. The antenna is realized on a high dielectric constant substrate and is compatible with microstrip circuitry and active devices. The gain of the antenna is 7.4 dBi, the front-to-back ratio is 15 dB and the nominal efficiency of the radiator is 95%.

Yagi Patch Antenna With Dual-Band and Pattern Reconfigurable Characteristics

Abstract: This letter presents a slot-loaded Yagi patch antenna with dual-band and pattern reconfigurable characteristics. The beam can scan in the E-plane by switching the modes of the antenna, which is implemented by changing the states of the switches installed in the slots etched on the parasitic patches. Different modes of the antenna have different radiation patterns and operating frequency bands. There are three modes having a common band of 9.15-9.45 GHz and their beams direct to -7deg, +33.5deg, and -40deg in the E-plane. Two among three modes also have another common frequency band around 10.3 GHz and the main beams direct to +58.5deg and -62.5deg, respectively. The third mode also has another frequency band around 10.85 GHz and has a dual-beam pattern. Simulated and measured results are given and they agree well with each other. The antenna can be used in radar, satellite communications, etc

Array antenna and a method of determining an antenna beam attribute

Abstract: A method of determining one or more attributes of an antenna beam based on measuring phase and/or amplitude differences at different points in a feed network. Amplitude and/or phase are measured by a probe ( 13 ) at an input to a differential variable element ( 7, 8, 9 ) and by a probe ( 14 ) at fewer than all of the outputs of the differential variable element. By using lookup tables based on actual measurements of antenna beam attributes for phase and/or amplitude differences at different points in a feed network computation may be simplified. The method enables a relatively inexpensive control circuit to be employed while providing accurate measurement of antenna beam attributes.

Ultrawideband Band-Notched Folded Strip Monopole Antenna

Abstract: We propose a new band-notched folded strip monopole antenna for ultrawideband applications. This antenna is composed of a forked-shape radiator and a 50 Omega microstrip line. To achieve band-rejected filtering property at the WLAN bands, the forked-shape strips are folded back and result in a pair of coupled lines on the radiator. The length and gap width of the coupled lines primarily determine the notched frequency of the antenna. Based on the band-notched resonance, an equivalent circuit model is proposed for the antenna and the calculated antenna input admittance agrees with the full-wave simulation data. With the help of the dimensionless normalized antenna transfer function, the radiation characteristics are investigated thoroughly. The transmission responses of a transceiving antenna system and their corresponding transient analysis are discussed at the end of this paper.

A New High-Gain Microstrip Yagi Array Antenna With a High Front-to-Back (F/B) Ratio for WLAN and Millimeter-Wave Applications

Abstract: A new printed microstrip Yagi array antenna is proposed that can achieve a high gain and low backside radiation for various applications up to the millimeter-wave frequency range. The high front-to-back (F/B) ratio (up to 15 dB) is attributed to the constructive interference that takes place between the individual printed Yagi arrays in the design. Through the spacing of the elements, the directivity (between 9-11.5 dBi) and the F/B ratio can be altered to suit the application of interest. The operational principles of this design are discussed to give insight on the radiation mechanism of the antenna. An initial design at around 32.5 GHz is presented to show the performance capabilities of this configuration. An impedance bandwidth of 8.3% can be achieved around this frequency. Then, a parametric analysis is conducted to estimate the significance of the design parameters that affect the antenna's performance. Finally, measured return loss and radiation pattern performance at 5.2 GHz is displayed to validate the principles and simulated results of the design. The measured impedance bandwidth of 10% is achieved. The F/B ratio is 15 dB which is larger than values previously published by 5-10 dB. Additionally, a gain of 10.7 dBi is observed. To the author's knowledge, this is the first microstrip Yagi array antenna presented that has a high gain and a high F/B ratio designed using simple fabrication techniques

Prediction of the Notch Frequency of Slot Loaded Printed UWB Antennas

Abstract: To prevent interference between ultrawideband (UWB) systems and existing wireless systems, creating notches in the UWB radiated field spectrum has been proposed. This filtering effect can be achieved by integrating a slot resonator to a UWB antenna. However, in printed monopole or dipole type UWB antennas, the notch frequency of the embedded slot depends on substrate and slot parameters. In this paper, we present a method to calculate, very accurately and efficiently, the notch frequency of such antennas. This method is validated by comparing theoretical and experimental results for 19 different slot width, slot length and dielectric constant combinations. The average difference is about 2%. We also assess the filtering action of slots from two aspects: the mismatch loss at the input and the radiation level in the far field. The sensitivity of the notch frequency to antenna parameters is also investigated.

Antenna e.g. transverse electromagnetic horn antenna, device for motor vehicle, has emblem mark, and radar antenna for transmitting signals to device for monitoring surrounding area at rear end of vehicle

Abstract: The device has a radar antenna e.g. transverse electromagnetic horn antenna, arranged behind a vertically aligned upper surface of an emblem mark (2) that is partially made of plastic and provided at a rear end of a motor vehicle. Beam direction of the antenna is perpendicular to a rear chamber provided at the rear end of the vehicle, via the upper surface of the emblem mark. The antenna transmits signals to a device for monitoring surrounding area at the rear end of the vehicle. The antenna has a filler material made of dielectric material.

Wideband Dipoles on Electromagnetic Bandgap Ground Planes

Abstract: The performance of broadband dipole antennas above electromagnetic bandgap (EBG) structures is investigated. Two different structures are examined. One is a diamond dipole over an EBG with square patch elements optimized by hand and the other an open sleeve dipole over an EBG optimized by a genetic algorithm (GA). Both configurations demonstrate that a low profile dipole antenna over an EBG can have a broad bandwidth. Careful design of both is required and in particular for best results, the antenna-EBG system should be optimized together, rather than as separate components. The performance is compared to an absorber backed wideband dipole antenna and it is found that the gain is significantly increased, whilst the bandwidth is reduced. In general, for the diamond dipole antenna return loss bandwidths of over 2:1 (67%) have been achieved, although radiation pattern control is difficult and reduces the bandwidth to the order of 1.4:1 (33%). The sleeve dipole over an EBG achieved a bandwidth of 1.28:1 (26%). The realized gain, which is power gain reduced by input match loss, of both structures are approximately the same. GA optimization and parametric studies seem to suggest that bandwidths significantly greater than these are difficult to achieve.

Proximity Effects of Metallic Environments on High Frequency RFID Reader Antenna: Study and Applications

Abstract: We study the proximity effects of metallic environments on the performance of high frequency (HF) radio frequency identification (RFID) reader antenna operating at 13.56 MHz. The performance of a typical HF RFID reader loop antenna in the proximity of various metal plate configurations is experimentally investigated in terms of resonant frequency, field intensity, and field distribution. The study shows that the presence of the metal plates shifts up the resonant frequency of the antenna and weakens its field intensity. The proximity effects are strongly dependent on the size of the metal plate, distance between the plate and the antenna as well as the orientation of the plate. Such effects greatly degrade the reading range and restrict the co-existence of HF RFID systems. A solution to alleviate the effects is to re-tune or co-design the reader antenna in proximity with the metallic objects based on the information from the study. As an example, a loop antenna is co-designed with a metal plate to configure a metal-backed loop antenna, and optimized for an RFID smart shelf system to restrain the interference and enhance the detection accuracy.

Stacked multiband antenna

Abstract: An antenna (1) comprises a number of antenna units (10, 20, 30), each comprising a lens (11, 12, 13) and any array (21, 22, 23) of beam ports (32). The antenna units (10, 20, 30) are arranged in a stack, and are configured to transmit or receive signals from the same field-of-view. Each unit (10, 20, 30) is configured to operate in a different frequency band, with the lenses (11, 12, 13) being configured such that an approximately constant beam shape is maintained across the entire operating bandwidth of the antenna (1).

Compact Three-Port Orthogonally Polarized MIMO Antennas

Abstract: Two designs for three-port orthogonally polarized antennas using dipole antennas and half-slot antennas are proposed in this letter. Each of the antennas constitutes three mutually perpendicular radiating elements to achieve good isolation and low antenna signal correlation between ports. The antennas are fabricated on FR4 epoxy boards and experimental results are provided. Experimental results show that the antennas resonate at 2.55 GHz and have a mutual coupling of less than -18 dB between elements. In addition, experimental results for the diversity performance and the multiple-input-multiple-output (MIMO) channel capacity are also provided for these antennas and these show that the proposed antennas offer good diversity gain and the channel capacity can be increased by as much as three times by using these antennas.

Gain Enhancement of a Microstrip Patch Antenna Using a Cylindrical Electromagnetic Crystal Substrate

Abstract: The performance of a circular microstrip patch antenna is improved using a new cylindrical electromagnetic bandgap (EBG) substrate. The microstrip patch antenna is fed by a coaxial probe and is integrated within a cylindrical electromagnetic bandgap substrate, based on the mushroom-like substrate, to increase the antenna gain. The cylindrical electromagnetic bandgap structure is a combination of two periodic structures with different periods. One is made of metallic rings and the other of grounding vias, which are disposed such as to form a radially and circularly periodic structure. A parametric analysis using a full-wave method was carried out in order to design the EBG structure. With the proposed concept, an antenna prototype was fabricated and tested. The radiation patterns and return loss obtained from measurements show a good impedance matching and a gain enhancement of the proposed antenna.

Compact Asymmetric Coplanar Strip Fed Monopole Antenna for Multiband Applications

Abstract: A compact asymmetric coplanar strip fed monopole antenna for multiband applications is presented. The antenna exhibits three resonances around 1.8, 2.4, and 5.6 GHz covering the DCS/PCS/UMTS/IEEE 802.11b/g/IEEE802.11a/HIPERLAN2 bands. The multiband characteristic of the antenna is due to the various meandered current paths excited in the radiating structure. The antenna has an overall dimension of only 2830 when printed on a substrate of dielectric constant 4.4. The uniplanar design, simple feeding technique and compactness make it easy for the integration of the antenna into circuit boards. Details of the antenna design, experimental and simulated results are presented and discussed.

Adaptively tunable antennas and method of operation therefore

Abstract: An embodiment of the present invention is an apparatus, comprising a tunable antenna including a variable reactance network connected to the antenna a closed loop control system adapted to sense the RF voltage across the variable reactance network and adjust the reactance of the network to maximize the RF voltage. The variable reactance network may comprise a parallel capacitance or a series capacitance. Further, the variable reactance networks may be connected to the antenna, which may be a patch antenna, a monopole antenna, or a slot antenna.

Heptagonal antenna array system

Abstract: An antenna system includes a heptagonal antenna array having one center antenna element and seven circumferentially surrounding antenna elements offering improved near and far sidelobe rejection, which is well suited for mechanically-gimbaled and time delayed electrical steering antenna applications.

Left-Handed Dipole Antennas and Their Implementations

Abstract: A new type of dipole antenna using a left-handed transmission line is proposed. The antenna is composed of a transmission line loaded periodically with shunt inductors and series capacitors. The placement of capacitors into one side only of the line leads to currents of different amplitude on the two sides. Because out-of-phase currents have different amplitudes, they do not completely cancel in the far field, and as a result radiate. Numerical investigation of a wire model shows a unique feature of left-handed transmission lines, which is a reduced wavelength with decreasing frequency. Measured results of two antennas are presented. One is a short dipole antenna working at n=-1, based on conventional resonance numbering. The antenna of 0.18 wavelengths in free space has a gain of -3.9 dBi and bandwidth of 1.7% for |S11 |<-10 dB. The other is a meandered dipole antenna working at n=-9. Polarization orthogonal to a right-handed one is achieved by the induced current of |-9| half wavelengths on the meander having 0.77 wavelengths in free space

Wideband microstrip patch antenna design for breast cancer tumour detection

Abstract: A patch antenna is presented which has been designed to radiate frequencies in the range 4-9.5 GHz into human breast tissue. The antenna is shown by means of previously unpublished simulation and practical measurements to possess a wide input bandwidth, radiation patterns that remain largely consistent over the band of interest and a good front-to-back ratio. Consideration is also given to the antenna's ability to radiate a pulse, and in this respect it is also found to be suitable for the proposed application

Dual-band wearable antennas over EBG substrate

Abstract: A dual-band coplanar patch antenna integrated with an electromagnetic bandgap substrate is reported. The antenna structure is made from common clothing fabrics and operates at the 2.45 and 5.1–5.8 GHz wireless bands. The bandgap array consists of just 3×3 elements but reduces radiation into the body by over 10 dB and improves the antenna gain by 3 dB.