Showing papers on "Slot antenna published in 2005"

The art and science of ultrawideband antennas

Abstract: Introduction and History of UWB Antennas. Antennas as Transducers. Antennas as Transformers. Antennas as Radiators. Antennas as Energy Converters. Taxonomy of UWB Antennas. Antennas in Systems.

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

Bandwidth enhancement and size reduction of microstrip slot antennas

Abstract: Reduced size microstrip monopole slot antennas with different slot shapes-straight, L and inverted T, and placed on a small ground plane, are investigated. The ground plane size is 50 mm/spl times/80 mm, which is about the size of a typical PC Wireless card. Detailed simulation and experimental investigations are conducted to understand their behavior and optimize for broadband operation. It is shown that, the variation in the slot shape, from straight to L and T shapes, helps in generating additional resonances, which when coupled to the original resonances of the slot, further increases impedance bandwidths. The bent shapes of the L and T slots reduce their height and provide more space on the ground plane for electronics. A mirror image dual L-slot antenna, placed at two adjacent corners of the ground plane, is also investigated and optimized for the polarization diversity. They provide an impedance bandwidth of 87%, with near orthogonal radiation characteristics. The measured impedance bandwidths (S/sub 11/=-10 dB) of up to 60%, 84%, and 80% are achieved for these straight, L and inverted T slots respectively, by suitably selecting their design parameters. The simulation results are in good agreement with the experimental data considering several practical issues.

Implantable medical device package antenna

Abstract: A wireless communication system is provided that includes an antenna structure adapted for coupling to a medical device antenna when the medical device is not implanted in a patient's body. The antenna structure effectively extends the medical device antenna length, thereby improving the efficiency and reliability of a communication link between the medical device and a programmer or monitor outside the implanted environment. The antenna structure is fabricated from any conductive material, which may be in the form of conductive wire, tape, ink, foil, film, adhesive or the like, and is attached to a portion of a medical device packaging assembly or another accessory device or substrate such as a pouch or overlay. The antenna structure may be a monopole, dipole, slot antenna, microstrip patch, or loop antenna, and may be fixed or movable relative to the substrate on which it is implemented.

Bandwidth enhancement of a printed wide-slot antenna with a rotated slot

Abstract: In this paper, a printed wide-slot antenna fed by a microstrip line with a rotated slot for bandwidth enhancement is proposed and experimentally studied. Impedance, radiation, and gain characteristics of this antenna are presented and discussed. From experimental results, the measured impedance bandwidth, defined by 10 dB return loss, can reach an operating bandwidth of 2.2 GHz at operating frequencies around 4.5 GHz, which is about four times that of a conventional microstrip-line-fed printed wide-slot antenna. Also, the antenna gain within the operating band is measured and studied, and a 2-dB gain bandwidth of at least 1 GHz is achieved.

Compact slot and dielectric resonator antenna with dual-resonance, broadband characteristics

Abstract: The goal of this study is to improve the bandwidth of a miniaturized antenna. The proposed technique combines a slot antenna and a dielectric resonator antenna (DRA) to effectively double the available bandwidth without compromising miniaturization or efficiency. With proper design it is observed that the resonance of the slot and that of the dielectric structure itself may be merged to achieve extremely wide bandwidth over which the antenna polarization and radiation pattern are preserved. In addition, using the DRA, a volumetric source, improves the radiation power factor of the radiating slot. A miniaturized antenna figure of merit (MAFM) is defined to simultaneously quantify aspects of miniaturized antenna performance including the degree of miniaturization, efficiency, and bandwidth. Figures for various common types of antennas are given and compared with that of the proposed structures. In order to determine the effects of varying design parameters on bandwidth and matching, sensitivity analysis is carried out using the finite-difference time-domain method. Numerous designs for miniaturized slot-fed dielectric resonator antennas are simulated and bandwidths exceeding 25% are achieved. Two 2.4 GHz antennas are built, characterized, and the results compared with theory.

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.

The significance of radiation efficiencies when using S-parameters to calculate the received signal correlation from two antennas

Abstract: The correlation coefficient between signals received by two antennas can be calculated from port S-parameters Antenna radiation efficiencies must, however, also be considered They result in an uncertainty in the calculated received signal correlation, if the correlation between the losses is unknown, which is often the case Relations are presented for the effect antenna efficiencies have on the calculated correlation

Frequency notched ultra-wideband microstrip slot antenna with fractal tuning stub

Abstract: A frequency notched ultra-wideband (UWB) microstrip slot antenna with a fractal tuning stub is proposed. The antenna is similar to a conventional microstrip slot antenna, and by introducing a fractal tuning stub, frequency notched function is achieved. The antenna was studied experimentally regarding impedance bandwidth, radiation patterns and gain. The operation bandwidth of the antenna is from 2.66 to 10.76 GHz, in which a frequency notched band from 4.95 to 5.85 GHz was achieved, along with good radiation performance over the entire frequency range.

One THz harmonic oscillation of resonant tunneling diodes

Abstract: One THz harmonic oscillation was observed in a sub-THz oscillating GaInAs∕AlAs resonant tunneling diode integrated with a slot antenna. The fundamental and third-harmonic frequencies were 342GHz and 1.02THz, respectively, for a 50μm long antenna. The maximum output power of the fundamental mode was around 23μW, and that of the third-harmonic component was 2.6% of the fundamental. Theoretical analysis with the van der Pole equation qualitatively explained the measured results.

Dual-band flat-plate antenna with a shorted parasitic element for laptop applications

Abstract: A novel dual-band flat-plate antenna with a shorted parasitic element for an internal laptop antenna for WLAN operation is presented. The proposed antenna is suitable to be integrated with the supporting metal frame for the display of the laptop and shows a low profile of 5 mm above the metal frame, thus making it easily embedded within the casing of the laptop as an internal antenna. Moreover, the proposed antenna can provide two separate impedance bandwidths of 190 MHz (about 8% centered at 2.4 GHz) and 2140 MHz (about 39% centered at 5.5 GHz), making it easily cover the required bandwidths for WLAN operation in the 2.4 GHz band (about 3.4% bandwidth required) and 5.2/5.8 GHz bands (about 13% bandwidth required). The proposed antenna is studied in detail in this study, and experimental and simulation results are presented.

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%.

Frequency Independent Antennas

Abstract: Frequency-independent (FI) antennas are radiating structures capable of maintaining consistent impedance and pattern characteristics over multiple-decade bandwidths. Their finite size limits the lowest frequency of operation, and the finite precision of the center region bounds the highest frequency of operation. The geometry of a frequency-independent antenna must be specified by angles alone, and principles such as truncation and self-complementarity are necessary and desired, respectively. In this article, Rumsey's theory of FI antennas, developed in the mid-1950s, is thoroughly discussed, and historical highlights listing the most important contributions in this area are given. A mathematical derivation for a general FI structure is provided, and some special cases are considered both theoretically and practically. A description and an explanation of the underlying theory of operation for several FI antenna types, including equiangular spirals, conventional and unconventional sinuous antennas, and log-periodic folded slot arrays, are also provided. A view of frequency independence through the modal content and contamination of the radiated far field is emphasized. Considerations for flush/conformal mounting are briefly discussed, including the use of log-periodic lossless cavities and broadband conical cavities. Keywords: frequency-independent antenna; equiangular spiral antenna; logperiodic antenna; dipole slot array; sinuous antenna; folded slot array

A wide-band slot antenna design employing a fictitious short circuit concept

Abstract: A wide-band slot antenna element is proposed as a building block for designing single- or multi-element wide-band or dual-band slot antennas. It is shown that a properly designed, off-centered, microstrip-fed, moderately wide slot antenna shows dual resonant behavior with similar radiation characteristics at both resonant frequencies and therefore can be used as a wide-band or dual-band element. This element shows bandwidth values up to 37%, if used in the wide-band mode. When used in the dual-band mode, frequency ratios up to 1.6 with bandwidths larger than 10% at both frequency bands can be achieved without putting any constraints on the impedance matching, cross polarization levels, or radiation patterns of the antenna. The proposed wide-band slot element can also be incorporated in a multi-element antenna topology resulting in a very wide-band antenna with a minimum number of elements. It is also shown that, by using only two of these elements in a parallel feed topology, an antenna with good radiation parameters over a 2.5:1 bandwidth ratio can be obtained.

Array antenna capable of controlling antenna characteristic

Abstract: An array antenna includes a feeder element, a parasitic element implemented by a slot line, a variable capacitance element, and a directivity switching unit The variable capacitance element is loaded in the slot line The directivity switching unit supplies a control voltage to the variable capacitance element in order to vary the capacitance, and switches directivity of the array antenna

Dual-frequency annular-ring slot antennas fed by CPW feed and microstrip line feed

Abstract: The dual-frequency properties of a dual annular-ring slot antenna fed by coplanar waveguide (CPW) and microstrip feedline are presented and experimentally studied. The proposed antenna is constructed by dual concentric annular-ring slots fabricated on FR4 substrate with single feed. The proposed slot antennas have good impedance matching for the two operating frequencies with a frequency ratio ranging about 1.34/spl sim/3.11 and 1.4/spl sim/1.74 can be achieved for CPW-fed and microstrip-fed.

2-D periodic leaky-wave Antennas-part II: slot design

Abstract: The far-field radiation patterns of a two-dimensional (2-D) periodic slot leaky-wave antenna (LWA) are studied. The antenna consists of a two-dimensional periodic array of slots in a conducting plane that is printed on top of a grounded dielectric slab. The antenna is excited by a simple source such as a dipole inside the slab. Reciprocity along with the spectral-domain method is used to calculate the far-field pattern, and the radiation characteristics of the structure are investigated. A comparison between the present periodic slot LWA and a 2-D periodic patch LWA discussed in Part I is given to show the advantages of the slot antenna for certain applications. The slot LWA can achieve high directivity patterns, and a circularly-polarized version of the antenna can achieve good circular-polarization at broadside.

Pattern descriptors for UWB antennas

Abstract: Three descriptors of antenna performance appropriate for ultrawide-band (UWB) applications are proposed and described: energy pattern, correlated energy pattern, and correlation coefficient pattern. The parameters are indicative of how a particular antenna will behave with a receiver employing correlation detection of broadband pulses. Numerical simulations of canonical dipole antennas demonstrate the significance of these parameters. In particular, there are substantial differences between total energy quantities and correlated energy quantities, showing that consistency of radiated pulse shape is a critical issue in UWB antenna performance. A further numerical example using crossed linear dipoles shows that even an antenna system exhibiting an isotropic radiation pattern at all frequencies does not provide an isotropic correlated energy pattern and hence cannot provide truly omnidirectional performance when pulse fidelity is considered.

Compact slotted planar inverted-F RFID tag mountable on metallic objects

Abstract: A compact slotted PIFA-type RFID tag (900 MHz) mountable on metallic objects is presented. The proposed structure can be easily matched to most microchips and facilitates their attachment on its slot. The performance of the tag is evaluated by monitoring its radar cross-sections (RCSs) for various incident angles and chip impedances. The measured detection distance is 4 m.

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 slotted post-wall waveguide array with interdigital structure for 45/spl deg/ linear and dual polarization

Abstract: This work proposes a dual-polarized planar antenna; two post-wall slotted waveguide arrays with orthogonal 45/spl deg/ linearly-polarized waves interdigitally share the aperture on a single layer substrate. Uniform excitation of the two-dimensional slot array is confirmed by experiment in the 25 GHz band. The isolation between two slot arrays is also investigated in terms of the relative displacement along the radiation waveguide axis in the interdigital structure. The isolation is 33.0 dB when the relative shift of slot position between the two arrays is -0.5/spl lambda//sub g/, while it is only 12.8 dB when there is no shift. The cross-polarization level in the far field is -25.2 dB for a -0.5/spl lambda//sub g/ shift, which is almost equal to that of the isolated single polarization array. It is degraded down to -9.6 dB when there is no shift.

Ultra-wideband low-cost phased-array radars

Abstract: Emerging radar applications require phased arrays that can operate over wide bandwidths to support multiband/multifunction operation. In response to that need, this paper presents a cost-effective implementation for extremely wide-band phased-array radars. Two designs are demonstrated, one operating from 3 to 12 GHz and the other operating from 8 to 20 GHz. These designs incorporate ultra-wideband antipodal tapered slot antennas, a novel cross-polarization suppressed array architecture, piezoelectric true-time-delay phase shifters, and broad-band high-power monolithic amplifiers. The resulting systems provide target detection and beam steering over the complete operating bandwidths. These results exceed the state-of-the-art for phased-array radars in terms of bandwidth and cost and should have direct applications in the development of ultra-wideband and multifunction radar systems.

Band‐notched ultra‐wideband circular‐disk monopole antenna with an arc‐shaped slot

Abstract: By embedding a simple arc-shaped slot in a circular-disk monopole antenna, an ultra-wideband (UWB, 3.1–10.6 GHz) operation with a controlled notched frequency band can be obtained. The arc-shaped slot is placed close to the boundary of the circular-disk monopole and has a length of about one-half wavelength of the desired notched frequency. The proposed slotted circular-disk monopole antenna showing UWB operation with a notched frequency band for rejecting the 5.8-GHz WLAN band is demonstrated. The effects of the dimensions of the arc-shaped slot on the notched frequency band are also analyzed. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 188–191, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20766

Band‐notched ultra‐wideband planar‐monopole antenna

Abstract: An ultra-wideband (UWB) planar metal-plate monopole antenna with a band-notch characteristic is presented. The proposed planar metal-plate monopole antenna is embedded with an inverted U-shape slot, whose length is selected to be a half-wavelength at the desired notched frequency. By adjusting the slot length, the notched frequency band within the antenna's operating bandwidth can be easily controlled. A design example for an UWB (3.1–10.6 GHz) planar metal-plate monopole antenna with a notched frequency band at 5 GHz is demonstrated. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 217–219, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20592

A novel feeding technique for antipodal linearly tapered slot antenna array

Abstract: A novel feeding system using substrate integrated waveguide (SIW) technique for antipodal linearly tapered slot array antenna (ALTSA) is presented in this paper. After making studies by simulations for a SIW fed ALTSA cell, a 1/spl times/8 ALTSA array fed by SIW feeding system at X-band is fabricated and measured, and the measured results show that this array antenna has a wide bandwidth and good performances.

Experimental and Theoretical Characteristics of Sub-Terahertz and Terahertz Oscillations of Resonant Tunneling Diodes Integrated with Slot Antennas

Abstract: Experimental and theoretical characteristics of sub-terahertz and terahertz oscillations in resonant tunneling diodes (RTDs) integrated with slot antennas are reported. In the experiments, oscillations up to 0.6 THz were obtained in GaInAs/AlAs double-barrier RTDs. The oscillation characteristics were theoretically analyzed for the total device structure including RTD and slot antenna. The equivalent circuit with all parasitic elements was taken into account for the RTD, and the actual structure of the antenna was analyzed using a three-dimensional electromagnetic simulator. The theoretical analysis was in good agreement with the measurements of oscillation frequency and output power. It was shown from the theoretical results that the RTD itself has the potential to oscillate up to 3.0 THz, and that the RTD oscillator with slot antenna is able to oscillate up to 2.8 THz if the device structure is optimized. The output power analysis showed that 90 µW at 1 THz is possible by optimizing the device structure.

Rectangular slot antenna with patch stub for ultra wideband applications and phased array systems

Abstract: This paper presents a coplanar waveguide fed rectangular slot antenna tuned by a patch stub. The presented antenna has 98% impedance bandwidth, and 6 dB average gain. The antenna can be used in phased array applications with more than 61% usable bandwidth.

A printed dipole antenna with tapered slot feed for ultrawide-band applications

Abstract: In this paper a planar antenna is studied for ultrawide-band (UWB) applications. This antenna consists of a wide-band tapered-slot feeding structure, curved radiators and a parasitic element. It is a modification of the conventional dual exponential tapered slot antenna and can be viewed as a printed dipole antenna with tapered slot feed. The design guideline is introduced, and the antenna parameters including return loss, radiation patterns and gain are investigated. To demonstrate the applicability of the proposed antenna to UWB applications, the transfer functions of a transmitting-receiving system with a pair of identical antennas are measured. Transient waveforms as the transmitting-receiving system being excited by a simulated pulse are discussed at the end of this paper.

Ultra-wideband tapered slot antenna with band cutoff characteristic

Abstract: A novel ultra-wideband (UWB) tapered slot antenna (TSA) is proposed that has both enhanced impedance bandwidth enough to cover UWB systems and band cutoff characteristic of 5 GHz WLAN band limited by IEEE802.11a and HIPERLAN/2. To achieve these two characteristics of wide bandwidth and partial band cutoff at the TSA, a broadband microstrip-slotline transition with multi-arm stubs and /spl lambda//4 short stubs, respectively, is used. From measured results, it is observed that wide bandwidth of about 2 octaves from 2.8 to 11.09 GHz for the VSWR<2 is achieved, while 5.05-5.93 GHz is cutoff with the radiated power of this cutoff band effectively suppressed as about -9 dB for the peak power level of other bands.

Quarter-wavelength wideband slot antenna for 3-5 GHz mobile applications

Abstract: In this letter, a quarter-wavelength ultra-wideband (UWB) slot antenna for 3-5 GHz mobile applications is proposed. Numerical results indicate that the performance of the antenna is insensitive to the size of the ground plane and an optimal performance of the antenna can be easily obtained by varying the dimensions of the slot and tuning stubs. Furthermore, a prototype of the antenna is made and a good agreement between simulation and measurement is achieved.