Showing papers on "Dipole antenna published in 2002"

Fractal antennas: a novel antenna miniaturization technique, and applications

Abstract: Fractal geometry involves a recursive generating methodology that results in contours with infinitely intricate fine structures. This geometry, which has been used to model complex objects found in nature such as clouds and coastlines, has space-filling properties that can be utilized to miniaturize antennas. These contours are able to add more electrical length in less volume. In this article, we look at miniaturizing wire and patch antennas using fractals. Fractals are profoundly intricate shapes that are easy to define. It is seen that even though the mathematical foundations call for an infinitely complex structure, the complexity that is not discernible for the particular application can be truncated. For antennas, this means that we can reap the rewards of miniaturizing an antenna using fractals without paying the price of having to manufacture an infinitely complex radiator. In fact, it is shown that the required number of generating iterations, each of which adds a layer of intricacy, is only a few. A primer on the mathematical bases of fractal geometry is also given, focusing especially on the mathematical properties that apply to the analysis of antennas. Also presented is an application of these miniaturized antennas to phased arrays. It is shown how these fractal antennas can be used in tightly packed linear arrays, resulting in phased arrays that can scan to wider angles while avoiding grating lobes.

Dominant mode leaky-wave antenna with backfire-to-endfire scanning capability

Abstract: A novel dominant mode leaky-wave antenna is proposed. This antenna is a transmission line structure with radiating wavenumber increasing from negative to positive values, providing backward to forward scanning capability as the frequency is increased. The characteristics and performances of the antenna are demonstrated by full-wave simulation and measurement results.

A high-efficiency dual-frequency rectenna for 2.45- and 5.8-GHz wireless power transmission

Abstract: A dual-frequency printed dipole rectenna has been developed for the wireless power transmission at 2.45- and 5.8-GHz (industrial-scientific-medical bands). For operating at dual band, a new uniplanar printed dipole antenna is developed using a coupling method. A GaAs Schottky barrier diode analysis is performed, and a proper device requirement is discussed to have high RF-to-dc conversion efficiencies at both frequencies. A novel coplanar stripline (CPS) low-pass filter integrated with two additional open-ended T-strip CPS bandstop filters effectively block higher order harmonics generated from the diode. The measured conversion efficiencies achieved at free space are 84.4 and 82.7% at 2.45 and 5.8 GHz, respectively.

A broadband planar quasi-Yagi antenna

Abstract: A novel broadband planar antenna based on the classic Yagi-Uda dipole array is presented. This "quasi-Yagi" antenna achieves a measured 48% bandwidth for VSWR <2, better than 12 dB front-to-back ratio, smaller than -15 dB cross polarization, 3-5 dB absolute gain and a nominal efficiency of 93% across the operating bandwidth. Finite-difference time-domain simulation is used for optimization of the antenna and the results agree very well with measurements. Additionally, a gain-enhanced design is presented, where higher gain has been achieved at the cost of reduced bandwidth. These quasi-Yagi antennas are realized on a high dielectric constant substrate and are completely compatible with microstrip circuitry and solid-state devices. The excellent radiation properties of this antenna make it ideal as either a stand-alone antenna with a broad pattern or as an array element. The antenna should find wide applications in wireless communication systems, power combining, phased arrays and active arrays, as well as millimeter-wave imaging arrays.

Intra-chip wireless interconnect for clock distribution implemented with integrated antennas, receivers, and transmitters

Abstract: A wireless interconnect system which transmits and receives RF signals across a chip using integrated antennas, receivers, and transmitters is proposed and demonstrated. The transmitter consists of a voltage-controlled oscillator, an output amplifier, and an antenna, while the receiver consists of an antenna, a low-noise amplifier, a frequency divider, and buffers. Using a 0.18-/spl mu/m CMOS technology, each of these individual circuits is demonstrated at 15 GHz. Wireless interconnection for clock distribution is then demonstrated in two stages. First, a wireless transmitter with integrated antenna generates and broadcasts a 15-GHz global clock signal across a 5.6-mm test chip, and this signal is detected using receiving antennas. Second, a wireless clock receiver with an integrated antenna detects a 15-GHz global clock signal supplied to an on-chip transmitting antenna located 5.6 mm away from the receiver, and generates a 1.875-GHz local clock signal. This is the first known demonstration of an on-chip clock transmitter with an integrated antenna and the second demonstration of a clock receiver with an integrated antenna, where the receiver's frequency and interconnection distance have approximately been doubled over previous results.

Antenna arrays formed of spiral sub-array lattices

Abstract: A antenna array ( 20 ) includes a plurality of periodic or aperiodic arranged sub-arrays ( 22 ). Each sub-array ( 22 ) includes a plurality of antenna elements ( 32 ) arranged in the form of a spiral ( 30 ). The sub-arrays ( 22 ) can comprise various spiral shapes to provide the required physical configuration and operational parameters to the antenna array ( 20 ). The elements ( 32 ) of each sub-array ( 22 ) are arranged to minimize the number of such elements ( 32 ) that intersect imaginary planes perpendicular to the spiral and passing through the spiral center. Such an orientation of the elements ( 32 ) minimizes grating lobes in the antenna pattern.

Antenna and EM Modeling with MATLAB

Abstract: Preface.Introduction.Receiving Antenna: The Scattering Algorithm.Algorithm for Far and Near Fields.Dipole and Monopole Antennas: The Radiation Algorithm. Loop Antennas.Antenna Arrays: Parameter Sweep.Broadband Antennas: The Frequency Sweep.Ultra wideband Communication Antenna: Time Domain Analysis.Antenna Loading: Lumped Elements.Patch Antennas.Appendix A: Other Triangular Meshes. Appendix B: Impedance Matrix Calculation.Index.

Effect of element mutual coupling on the capacity of fixed length linear arrays

Abstract: The effect of element mutual coupling on the capacity of multiple-input-multiple-output (MIMO) antenna systems is demonstrated by considering a fixed-length linear array of half-wave dipoles. Mutual coupling between elements, which influences both the spatial correlation and the received signal-to-noise ratio (SNR), is taken into account by means of the impedance matrix. Monte Carlo simulations are performed for both single-sided (i.e., transmitting end or receiving end) and double-sided fading correlations. It is shown that mutual coupling results in substantially lower capacity and, hence, in reduced degrees of freedom.

Thin absorbing screens using metamaterial surfaces

Abstract: Metamaterial surfaces can be conceptualized by a 2-dimensional periodic arrangement of many small flat inclusions on an otherwise homogeneous host surface. The electromagnetic properties of such metamaterial plates, which can indeed be regarded as frequency-selective surfaces, are influenced by the shape and geometry of these inclusions. When a metamaterial surface is closely placed above a perfectly conducting plate, at a certain frequency band, this structure may possess a high surface impedance at its top surface, thus providing a high-impedance ground plane (HIGP). The center frequency and bandwidth over which such a high-impedance electromagnetic surface is achieved depend on inclusion shapes and compositions, among other parameters. By placing a resistive sheet on top of this surface, we can achieve a thin structure that can be an efficient absorber for incident electromagnetic energy.

Angular power distribution and mean effective gain of mobile antenna in different propagation environments

Abstract: We measured the elevation angle distribution and cross-polarization power ratio of the incident power at a mobile station in different radio propagation environments at 2.15 GHz frequency. A novel measurement technique was utilized, based on a wideband channel sounder and a spherical dual-polarized antenna array at the receiver. Data were collected over 9 km of continuous measurement routes, both indoor and outdoor. Our results show that in non-line-of-sight situations, the power distribution in elevation has a shape of a double-sided exponential function, with different slopes on the negative and positive sides of the peak. The slopes and the peak elevation angle depend on the environment and base-station antenna height. The cross-polarization power ratio varied within 6.6 and 11.4 dB, being lowest for indoor and highest for urban microcell environments. We applied the experimental data for analysis of the mean effective gain (MEG) of several mobile handset antenna configurations, with and without the user's head. The obtained MEG values varied from approximately -5 dBi in free space to less than -11 dBi beside the head model. These values are considerably lower than what is typically used in system specifications. The result shows that considering only the maximum gain or total efficiency of the antenna is not enough to describe its performance in practical operating conditions. For most antennas, the environment type has little effect on the MEG, but clear differences exist between antennas. The effect of the user's head on the MEG depends on the antenna type and on which side of the head the user holds the handset.

High-strength microwave antenna assemblies

Abstract: Various high-strength microwave antenna assemblies are described herein. The microwave antenna has a radiating portion connected by a feedline to a power generating source, e.g., a generator. The antenna is a dipole antenna with the distal end of the radiating portion being tapered and terminating at a tip to allow for direct insertion into tissue. Antenna rigidity comes from placing distal and proximal radiating portions in a pre-stressed state, assembling them via threaded or overlapping joints, or fixedly attaching an inner conductor to the distal portion. The inner conductor is affixed to the distal portion by, e.g., welding, brazing, soldering, or by adhesives. A junction member made from a hard dielectric material, e.g., ceramic, can be placed between the two portions and can have uniform or non-uniform shapes to accommodate varying antenna designs. Electrical chokes may also be used to contain returning currents to the distal end of the antenna.

Adaptive antenna optimization network

Abstract: An adjustable matching network is provided for a wireless communications device transmitting and receiving signals in multiple frequency bands via an antenna. The adjustable matching network selectively connecting the antenna to a select power amplifier corresponding to a selected transmit frequency band and automatically matching the impedance of the antenna to the select power amplifier. The adjustable matching network also selectively connecting the antenna to a select bandpass filter corresponding to a selected receive frequency band and automatically matching the impedance of the antenna to the select bandpass filter.

Distributed active transmit and/or receive antenna

Abstract: A distributed antenna system comprising a plurality of antenna elements, duplexers and amplifiers, each amplifier and duplexer operatively coupled with one of said antenna elements and mounted closely adjacent to the associated antenna element in such a manner as incidences of insertion loss, noise and system failure are reduced.

Comformal phased array antenna and method for repair

Abstract: A conformal phased array antenna and associated method of repairing the antenna are provided. The antenna has individual subassemblies or line replaceable units such that the antenna can be repaired without completely removing the entire antenna. The antenna generally includes a planar antenna subassembly including an array of RF modules disposed in a reference plane. The antenna also typically has a contoured waveguide subassembly including a contoured aperture honeycomb structure. The contoured aperture honeycomb structure defines a number of passages that are in communication with respective RF modules. The exterior surface of the contoured aperture honeycomb structure that faces away from the planar antenna subassembly is contoured such that at least portions of this surface are at an oblique angle with respect to the reference plane. This contoured surface may advantageously be shaped to match the contour of the surface of the structure to which the antenna is mounted.

Tunable horn antenna

Abstract: A family of FE dielectric-tuned antennas and a method for frequency tuning a wireless communications antenna are provided. The method comprises: forming a radiator; forming a dielectric with ferroelectric material proximate to the radiator; applying a voltage to the ferroelectric material; in response to applying the voltage, generating a dielectric constant; and, in response to the dielectric constant, communicating electromagnetic fields at a resonant frequency. Some aspects of the method further comprise: varying the applied voltage; and, modifying the resonant frequency in response to changes in the applied voltage. Modifying the resonant frequency includes forming an antenna with a variable operating frequency responsive to the applied voltage. Alternately stated, forming an antenna with a variable operating frequency includes forming an antenna with a predetermined fixed characteristic impedance, independent of the resonant frequency.

Protable radio terminal testing apparatus using single self-complementary antenna

Abstract: A portable radio terminal testing apparatus has an antenna coupler 20, a connecting member 16, and a measuring device 15. The antenna coupler 20 has a placement member 35, a coupling antenna 25, a pair of through-connection portions, and an impedance transformer 31. The placement member 35 accepts a portable radio terminal 1, which is a testing object, in an unrestricted state. The coupling antenna 25 is disposed so as to be electromagnetically coupled with an antenna 19 of the portable radio terminal 1, and has a pair of antenna elements which are formed at one face side of a dielectric substrate 26 and which have a planar antenna structure of a predetermined shape, and a pair of feeding points, and is formed from a self-complementary antenna having a predetermined impedance within an operating frequency range including at least 800 MHz to 2.5 GHz order.

Leaky CPW-based slot antenna arrays for millimeter-wave applications

Abstract: A uniplanar leaky-wave antenna (LWA) suitable for operation at millimeter-wave frequencies is introduced. Both unidirectional and bidirectional versions of the antenna are presented. The proposed structure consists of a coplanar waveguide fed linear array of closely spaced capacitive transverse slots. This configuration results in a fast-wave structure in which the n=0 spatial harmonic radiates in the forward direction. Since the distance, d, between adjacent elements of the array is small d/spl Lt//spl lambda//sub o/, the slot array essentially becomes a uniform LWA. A comprehensive transmission line model is developed based upon the theory of truncated periodic transmission lines to explain the operation of the antenna and provide a tool for its design. Measured and simulated radiation patterns, directivity, gain, and an associated loss budget are presented for a 32-element antenna operating at 30 GHz. The uniplanar nature of the structure makes the antenna appropriate for integration of shunt variable capacitors such as diode or micro-electromechanical system varactors for fixed frequency beam steering at low-bias voltages.

Planar elliptical element ultra-wideband dipole antennas

Abstract: This note introduces a new class of planar ultra-wideband (UWB) dipoles that use elliptical elements. These antennas offer good dipole performance over nearly two octaves in frequency. Unlike more traditional broadband dipole elements that must be around a quarter-wavelength to radiate efficiently, planar elliptical UWB dipoles still exhibit a –10 dB return loss for a 0.20λ element size, and remain 50% efficient (–3 dB return loss) for a 0.14λ element size. A wide variety of techniques including exponential and Klopfenstein tapers, and an energy flow analysis all converge to an element axial ratio of about 1.5:1 being optimal. Introduction: A variety of planar dipoles antennas exhibit ultra-wideband performance. These include bow tie antennas 1 and diamond dipoles. 2 Recently, work has been done on elliptical and disk monopoles that are well matched to 50 Ω and exhibit superior broadband performance. 3 One might expect that if a monopole element were well matched to 50 Ω, the corresponding element in a dipole configuration would have a characteristic impedance of around 100 Ω. This note introduces a new class of planar ultra-wideband (UWB) dipoles that use elliptical elements. Counter to expectation, these antennas are well-matched to 50 Ω, and offer good dipole performance over nearly two octaves in frequency. This note discusses the performance of a variety of elliptical planar dipoles with differing eccentricity.

Antenna module and light pole with such an antenna module

Abstract: The antenna module has a central pillar (7) enclosed by attachment arrangements (10) for attaching transmission and/or reception antennas(11), especially for telecommunications, a screen (14) of material that passes radio waves and a coupling arrangement (8,9) at the base and/or top of the pillar for attaching the module to a structure or connecting it to another antenna module. AN Independent claim is also included for the following: a light mast with several lighting bodies and an inventive device.

Electromagnetic wave interaction with stratified negative isotropic media

Abstract: In this paper we provide a general formulation for the electromagnetic wave interaction with stratified media and then specialize to slabs of negative isotropic media. The field solutions are obtained in all regions of the stratified medium. The characteristic waves in negative isotropic media are backward waves. We derive the field solutions and show that a Gaussian beam is laterally shifted by a negative isotropic slab. The amount of beam center shift is calculated for both cases of transmission and reflection. Guided waves in stratified media are studied. Placing a linear antenna and all types of Hertzian dipole antennas in a stratified medium, we obtained solutions in all regions. We demonstrate and locate the positions of the perfect images of the antenna sources in the presence of negative isotropic slabs.

Dipole arrangements using dielectric substrates of meta-materials

Abstract: The invention concerns a dipole antenna of reduced size and with improved impedance bandwidth. The antenna is preferably formed on a dielectric substrate having a plurality of regions, each having a characteristic relative permeability and permittivity. First and second dipole radiating element defining conductive paths can be selectively formed on first characteristic regions of the substrate having a first characteristic permeability and first permittivity. A reactive coupling element can be interposed between the dipole radiating elements for reactively coupling the first dipole radiating element to the second dipole radiating element.

Antenna system having high impedance surface

Abstract: An antenna system for receiving both circularly polarized electromagnetic signals and linearly polarized electromagnetic signals, the circularly polarize signals arriving at the antenna system from a direction normal or oblique to a major surface of the antenna system and the linearly polarized signals arriving at the planar antenna system from a direction acute to said major surface The antenna system includes a high impedance surface and a plurality of antenna elements disposed on said high impedance surface, the plurality antenna elements arranged in a pattern on said surface such first selected ones of said antenna elements are responsive to circular polarization and second selected ones of said antenna elements are responsive to linear polarization

The MIMO cube - a compact MIMO antenna

Abstract: A compact MIMO antenna is suggested by combining polarization diversity and space diversity into one arrangement consisting of a cube where all 12 edges consist of an electrical dipole. The antenna should be useful in an indoor environment with waves arriving from many directions with arbitrary polarizations. The highest gain values are around 8.5 dB per cube and the theoretical capacity is 47 b/s/Hz for a basic SNR of 20 dB. The number of active channels is 12 for a side length of half-a-wavelength, but reduces to 6 for a very compact antenna. Even for less ideal conditions like only horizontal propagation, or lack of cross polarization, the capacity attains considerable values.

Investigations into a cavity-backed circular-patch antenna

Abstract: An empirical formula for resonant frequency of a circular cavity-enclosed circular-patch antenna is tested with measured results. The patch miniaturization in the presence of the cavity is proved. Different design curves in terms of resonant frequencies and bandwidth are derived to facilitate antenna design without a priori knowledge of complex numerical techniques. A simple gain formula for a circular-patch antenna is derived and tested against the measured gain data. The results agree very well. The beamwidth, axial ratio, and mutual coupling in the presence of the cavity are investigated.

Wideband smart antenna theory using rectangular array structures

Abstract: Smart antenna techniques at the base station can dramatically improve the performance of the mobile radio system by employing spatial filtering. The design of a fully spatial signal processor using rectangular array configuration is proposed. Two-dimensional (2-D) spatial filters that can be implemented by microstrip technology are capable of filtering the received signal in the angular domain as well as the frequency domain. Furthermore, it has wideband properties and, hence, eliminates the requirement of different antenna spacing for applications including various carrier frequencies. The desired frequency selectivity of the smart antenna can be combined with compensation of the undesired frequency performance of a single antenna element, and the result is quite satisfactory for practical implementation. In addition, if the elements of the array are not perfectly omnidirectional or frequency independent, we can compensate for these deficiencies in the design algorithm. Two different algorithms for calculating the real-valued weights of the antenna elements are proposed. The first algorithm is more complex but leads to sharper beams and controlled performance. The second method is simpler but has wider beam and lower fractional bandwidth. Some computer simulation results demonstrating the directional beam patterns of the designed beamformers are also presented.

Novel design of broad-band stacked patch antenna

Abstract: A novel broadband stacked E-shaped patch antenna is proposed in this paper. The proposed antenna has an input impedance bandwidth of about 38.41%, better than the conventional E-shaped microstrip patch antenna, which has an input impedance bandwidth of 33.8%. Through the use of the washer on the probe of the stacked patch antenna, the input impedance bandwidth is improved further to 44.9%. The radiation patterns are found to be relatively constant throughout the whole band. Comparisons of these antennas are presented in this paper.

Printed dual-band dipole antenna with U-slotted arms for 2.4/5.2 GHz WLAN operation

Abstract: Dual-band operation of a printed dipole antenna with U-slotted arms is presented. Due to the embedded U-shaped slots, two additional dipole arms are obtained in the proposed design, which form a second dipole antenna with a smaller length and which can generate a higher resonant mode for the 5.2 GHz band operation. By incorporating the original dipole arms designed for the 2.4 GHz band operation, the proposed antenna can perform WLAN operations in the 2.4 and 5.2 GHz bands.

A quarter-wave U-shaped patch antenna with two unequal arms for wideband and dual-frequency operation

Abstract: A wideband and dual-frequency quarter-wave U-shaped patch antenna with two unequal arms on FR4 substrate is presented. The U-shaped patch antenna is fed electromagnetically by another coaxially-fed patch on the same layer, which operates at a higher frequency band. In this paper, we first proposed a new technique to obtain two closely staggered resonant modes to achieve a wide impedance bandwidth using two unequal arms of the U-shaped patch for the lower band. For the substrate thickness = 5, 7.5 and 11 mm, the measured bandwidths of the antennas operating around at 900 MHz are 7%, 10%, and 18%, respectively. Then, we modify the coaxially-fed patch so that both bands are wide in bandwidth. The resulting antenna operating at 900 and 1800-MHz bands with the substrate thickness 11 mm has a measured impedance bandwidth of 13.3% and 20 respectively. This thickness corresponds to 0.033 free-space wavelength at 900 MHz. The far-field radiation patterns are stable in the two operating bands. The proposed antenna is simple in structure compared with the regular stacked or coplanar parasitic patch antennas. It is highly suitable for indoor mobile communications.

High transmission gain integrated antenna on extremely high resistivity Si for ULSI wireless interconnect

Abstract: We have demonstrated the highest transmission gain integrated dipole antenna on Si reported so far, to use as an integrated antenna for the purpose of ULSI on-chip wireless interconnection. A 2-mm long and 10-/spl mu/m wide dipole antenna pair at a distance of 1 cm shows a transmission gain of -36.5 dB at 18 GHz, which is 20 dB higher than the previously reported gain. This large increase in gain is achieved by proton implantation on the Si substrate, which increased the resistivity from 10 /spl Omega/-cm to 0.1 M/spl Omega/-cm. It is also found that transmission gain can be maximized for a given resistivity by optimizing the Si substrate thickness or by inserting a low-k dielectric layer below the substrate.

Fractal antennas and fractal resonators

Abstract: An antenna includes at least one element whose physical shape is at least partially defined as a second or higher iteration deterministic fractal. The resultant fractal antenna does not rely upon an opening angle for performance, and may be fabricated as a dipole, a vertical, or a quad, among other configurations. The number of resonant frequencies for the fractal antenna increases with iteration number N and more such frequencies are present than in a prior art Euclidean antenna. Further, the resonant frequencies can include non-harmonically related frequencies. At the high frequencies associated with wireless and cellular telephone communications, a second or third iteration, preferably Minkowski fractal antenna is implemented on a printed circuit board that is small enough to fit within the telephone housing. A fractal antenna according to the present invention is substantially smaller than its Euclidean counterpart, yet exhibits at least similar gain, efficiency, SWR, and provides a 50Ω termination impedance without requiring impedance matching.