Showing papers in "IEEE Transactions on Antennas and Propagation in 2010"
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TL;DR: In this paper, the authors used vector field-sensing electric and magnetic triaxial antennas to estimate the orbital angular momentum (OAM) of radio beams, assuming ideal (noiseless) conditions and that the beam axis is known.
Abstract: Recent discoveries concerning rotating (helical) phase fronts and orbital angular momentum (OAM) of laser beams are applied to radio frequencies and comprehensive simulations of a radio OAM system are performed. We find that with the use of vector field-sensing electric and magnetic triaxial antennas, it is possible to unambiguously estimate the OAM in radio beams by local measurements at a single point, assuming ideal (noiseless) conditions and that the beam axis is known. Furthermore, we show that conventional antenna pattern optimization methods can be applied to OAM-generating circular arrays to enhance their directivity.
700 citations
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TL;DR: In this paper, an artificial impedance surface that is implemented as an array of sub-wavelength metallic patches on a grounded dielectric substrate is designed to scatter a known input wave into a desired output wave.
Abstract: We have developed a method for controlling electromagnetic surface wave propagation and radiation from complex metallic shapes. The object is covered with an artificial impedance surface that is implemented as an array of sub-wavelength metallic patches on a grounded dielectric substrate. We pattern the effective impedance over the surface by varying the size of the metallic patches. Using a holographic technique, we design the surface to scatter a known input wave into a desired output wave. Furthermore, by varying the shape of the patches we can create anisotropic surfaces with tensor impedance properties that provide control over polarization. As an example, we demonstrate a tensor impedance surface that produces circularly polarized radiation from a linearly polarized source.
682 citations
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TL;DR: In this paper, the effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model.
Abstract: High-impedance surfaces (HIS) comprising lossy frequency selective surfaces (FSS) are employed to design thin electromagnetic absorbers. The structure, despite its typical resonant behavior, is able to perform a very wideband absorption in a reduced thickness. Losses in the frequency selective surface are introduced by printing the periodic pattern through resistive inks and hence avoiding the typical soldering of a large number of lumped resistors. The effect of the surface resistance of the FSS and dielectric substrate characteristics on the input impedance of the absorber is discussed by means of a circuital model. It is shown that the optimum value of surface resistance is affected both by substrate parameters (thickness and permittivity) and by FSS element shape. The equivalent circuit model is then used to introduce the working principles of the narrowband and the wideband absorbing structure and to derive the best-suited element for wideband absorption.
612 citations
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TL;DR: Based on the channel analysis, the MI waveguide technique for communication is developed in order to reduce the high path loss of the traditional EM wave system and the ordinary MI system and reveals that the transmission range of the MIWaveguide system is dramatically increased.
Abstract: The main difference between the wireless underground sensor networks (WUSNs) and the terrestrial wireless sensor networks is the signal propagation medium. The underground is a challenging environment for wireless communications since the propagation medium is no longer air but soil, rock and water. The well established wireless signal propagation techniques using electromagnetic (EM) waves do not work well in this environment due to three problems: high path loss, dynamic channel condition and large antenna size. New techniques using magnetic induction (MI) create constant channel condition and can accomplish the communication with small size coils. In this paper, detailed analysis on the path loss and the bandwidth of the MI system in underground soil medium is provided. Based on the channel analysis, the MI waveguide technique for communication is developed in order to reduce the high path loss of the traditional EM wave system and the ordinary MI system. The performance of the EM wave system, the ordinary MI system and our improved MI waveguide system are quantitatively compared. The results reveal that the transmission range of the MI waveguide system is dramatically increased.
516 citations
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TL;DR: In this paper, the authors examined the range of frequencies that will optimize the tradeoff between received power and tissue absorption and showed that the optimal frequency is above 1 GHz for small receive coil and typical transmit-receive separations.
Abstract: RF wireless interface enables remotely-powered implantable devices. Current studies in wireless power transmission into biological tissue tend to operate below 10 MHz due to tissue absorption loss, which results in large receive antennas. This paper examines the range of frequencies that will optimize the tradeoff between received power and tissue absorption. It first models biological tissue as a dispersive dielectric in a homogeneous medium and performs full-wave analysis to show that the optimal frequency is above 1 GHz for small receive coil and typical transmit-receive separations. Then, it includes the air-tissue interface and models human body as a planarly layered medium. The optimal frequency is shown to remain in the GHz-range. Finally, electromagnetic simulations are performed to include the effect of load impedance and look at the matched power gain. The optimal frequency is in the GHz-range for mm-sized transmit antenna and shifts to the sub-GHz range for cm-sized transmit antenna. The multiple orders of magnitude increase in the operating frequency enables dramatic miniaturization of implantable devices.
419 citations
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TL;DR: In this paper, a balanced antipodal Vivaldi antenna is designed to be used as a sensor for a microwave breast cancer detection system, which has the ability to send short electromagnetic pulses into the near-field, with low distortion, low loss and in a directional manner.
Abstract: A balanced antipodal Vivaldi antenna is designed to be used as a sensor for a microwave breast cancer detection system. The antenna has the ability to send short electromagnetic pulses into the near-field, with low distortion, low loss and in a directional manner. The antenna directivity is further improved by the inclusion of a novel feature in the antenna aperture called a “director” which consists of a profiled piece of higher dielectric constant material. Several simulated results are successfully confirmed with measurements. Reflections of a tumor placed in a breast model are simulated for two cases, namely a balanced antipodal Vivaldi antenna with and without a director. Greater tumor responses are recorded with the director present, demonstrating the potential of this feature for microwave breast imaging.
365 citations
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TL;DR: A new numerical stochastic optimization algorithm, inspired from colonizing weeds, is proposed for Electromagnetic applications, and invasive weed optimization (IWO) is described and applied to different electromagnetic problems.
Abstract: A new numerical stochastic optimization algorithm, inspired from colonizing weeds, is proposed for Electromagnetic applications. This algorithm, invasive weed optimization (IWO), is described and applied to different electromagnetic problems. The linear array antenna synthesis, the standard problem used by antenna engineers, is presented as an example for the application of the IWO. Compared to the PSO, The features of the IWO are shown. As another application, the design of aperiodic thinned array antennas by optimizing the number of elements and at the same time their positions is presented. By implementing this new scenario, thinned arrays with less number of elements and lower sidelobes, compared to the results achieved by genetic algorithm (GA) for the same aperture dimensions, are obtained. Finally, the IWO is applied to a U-slot patch antenna to have the desired dual-band characteristics.
335 citations
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TL;DR: In this article, a dielectric loaded substrate integrated waveguide (SIW) H-plane sectoral horn antenna has been proposed and two antennas with rectangular and elliptical shaped loaded dielectrics were designed and fabricated.
Abstract: A dielectric loaded substrate integrated waveguide (SIW) H-plane sectoral horn antenna has been proposed in this paper. The horn and the loaded dielectric are integrated by using the same single substrate resulting in easy fabrication and low cost. Two antennas with rectangular and elliptical shaped loaded dielectrics were designed and fabricated. These antennas have high gain and narrow beamwidths both in the E-plane and in the H-plane. The results from the simulation and those from the measurement are in good agreement. To demonstrate applications of the array, the small aperture elliptical dielectric loaded antenna has been used to form an array to obtain higher gain and to form a one-dimensional monopulse antenna array.
331 citations
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TL;DR: In this paper, a four-layer transmit array operating at 30 GHz is designed using a dual-resonant double square ring as the unit cell element. And the design procedure for both the single-layer unit cell and the cascaded connection of four layers is described and it leads to a 50% increase in the -1 dB gain bandwidth over that of previous transmitarrays.
Abstract: A four-layer transmitarray operating at 30 GHz is designed using a dual-resonant double square ring as the unit cell element. The two resonances of the double ring are used to increase the per-layer phase variation while maintaining a wide transmission magnitude bandwidth of the unit cell. The design procedure for both the single-layer unit cell and the cascaded connection of four layers is described and it leads to a 50% increase in the -1 dB gain bandwidth over that of previous transmitarrays. Results of a 7.5% -1 dB gain bandwidth and 47% radiation efficiency are reported.
329 citations
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TL;DR: In this article, a single-feed configuration based asymmetric-circular shaped slotted square microstrip patches are adopted to realize the compact circularly polarized microstrip antennas with slits.
Abstract: Novel asymmetric-circular shaped slotted microstrip patch antennas with slits are proposed for circularly polarized (CP) radiation and radio frequency identification (RFID) reader applications. A single-feed configuration based asymmetric-circular shaped slotted square microstrip patches are adopted to realize the compact circularly polarized microstrip antennas. The asymmetric-circular shaped slot(s) along the diagonal directions are embedded symmetrically onto a square microstrip patch for CP radiation and small antenna size. The CP radiation can be achieved by slightly asymmetric (unbalanced) patch along the diagonal directions by slot areas. Four symmetric-slits are also embedded symmetrically along the orthogonal directions of the asymmetric-circular shaped slotted patch to further reduce antenna size. The operating frequency of the antenna can be tuned by varying the slit length while keeping the CP radiation unchanged. The measured 3-dB axial-ratio (AR) bandwidth of around 6.0 MHz with 17.0 MHz impedance bandwidth is achieved for the antenna on a RO4003C substrate. The overall antenna size is 0.27λo × 0.27λo × 0.0137λo at 900 MHz.
268 citations
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TL;DR: The minimization of the power losses in time-modulated arrays is addressed by means of a suitable strategy based on particle swarm optimization, aimed at reducing the amount of wasted power, analytically computed through a very effective closed-form relationship.
Abstract: The minimization of the power losses in time-modulated arrays is addressed by means of a suitable strategy based on particle swarm optimization. By properly modifying the modulation sequence, the method is aimed at reducing the amount of wasted power, analytically computed through a very effective closed-form relationship, while constraining the radiation pattern at the carrier frequency below a fixed sidelobe level. Representative results are reported and compared with previously published solutions to assess the effectiveness of the proposed approach.
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TL;DR: In this article, the reactive energy stored in the electromagnetic field surrounding an electromagnetic device is calculated using new expressions, completely general, explicit and without approximations in terms of the currents flowing on the device.
Abstract: New expressions are derived to calculate the reactive energy stored in the electromagnetic field surrounding an electromagnetic device. The resulting expressions are very simple to interpret, completely general, explicit and without approximations in terms of the currents flowing on the device. They are also fast since they involve integrals solely over the device generating the field. The new technique is very feasible to be used in cases where the electric and magnetic reactive energies are important in practice, especially in the case of radiating structures. Used there, they allow to study the effect of the shape of the device on the amount of reactive energy, and thus on the Q of the device. The implementation of the new expressions in numerical CAD tools is extremely simple and straightforward.
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TL;DR: In this paper, the authors present a comprehensive synthesis procedure for designing low profile, band-pass frequency selective surfaces composed of non-resonant constituting elements, which can provide sharp frequency selectivity and stable frequency responses as functions of angle and polarization of incidence of the EM wave.
Abstract: We present a comprehensive synthesis procedure for designing low-profile, band-pass frequency selective surfaces composed of non-resonant constituting elements. The proposed FSSs use arrays of sub-wavelength periodic structures with non-resonant constituting unit cells with unit cell dimensions and periodicities in the range of , where is the free space wavelength. The main advantages of this type of FSS, compared to traditional ones, are that they allow for the design of low-profile and ultra-thin FSSs that can provide sharp frequency selectivity and stable frequency responses as functions of angle and polarization of incidence of the EM wave. An order FSS designed using this technique typically has an electrical thickness in the order of which is significantly smaller than the overall thickness of a traditionally designed order FSS . The proposed synthesis procedure is validated for two FSS prototypes having third- and fourth-order band-pass responses. Principles of operation, detailed synthesis procedure, measurement results of a fabricated prototype, and implementation guidelines for this type of FSS are presented and discussed in this paper.
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TL;DR: In this paper, the design of a 2D broadband Luneburg lens antenna implemented using printed circuit board techniques is detailed, and the measured half power beamwidth of the experimental antenna is 4.34°.
Abstract: The design of a 2D broadband, Luneburg lens antenna implemented using printed circuit board techniques is detailed. The refractive index of the lens is controlled through a combination of meandering crossed microstrip lines and varying their widths. The 12.4λ° diameter lens is designed to operate in the transverse electromagnetic (TEM) mode at 13 GHz. The lens antenna was designed, fabricated, and measured. The measured half power beamwidth of the experimental antenna is 4.34°.
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TL;DR: In this article, a planar monopole antenna is proposed that employs reactive loading and a?defected? ground-plane structure, which enables the loaded antenna to operate in two modes: dipolar mode over the lower WiFi band of 2.40 GHz -2.48 GHz and a monopolar mode on the 5.15-5.80 GHz upper WiFi band.
Abstract: A compact tri-band planar monopole antenna is proposed that employs reactive loading and a ?defected? ground-plane structure. The reactive loading of the monopole is inspired by transmission-line based metamaterials (TL-MTM), which enables the loaded antenna to operate in two modes. The first resonance exhibits a dipolar mode over the lower WiFi band of 2.40 GHz - 2.48 GHz, and the second resonance has a monopolar mode over the 5.15-5.80 GHz upper WiFi band. Full-wave analysis shows that the currents of the two modes are orthogonal to each other, resulting in orthogonal radiation patterns in the far field. The feature of a ?defected? ground-plane, formed by appropriately cutting an L-shaped slot out of one of the CPW ground-planes, leads to the third resonance that covers the WiMAX band at 3.30-3.80 GHz. Air bridges at the intersection between the antenna and the CPW feedline ensure a balanced current. A fabricated prototype has compact dimensions of 20.0 mm × 23.5 mm × 1.59 mm, and exhibits good agreement between the measured and simulated S parameters and radiation patterns. The measured radiation efficiencies are 67.4% at 2.45 GHz, 86.3% at 3.50 GHz and 85.3% at 5.50 GHz.
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TL;DR: In this paper, a convex optimization based beampattern synthesis method with antenna selection is proposed for linear and planar arrays, which can achieve completely arbitrary sidelobe levels.
Abstract: A convex optimization based beampattern synthesis method with antenna selection is proposed for linear and planar arrays. Conjugate symmetric beamforming weights are used so that the upper and non-convex lower bound constraints on the beampattern can be convex. Thus, a mainlobe of an arbitrary beamwidth and response ripple can be obtained. This method can achieve completely arbitrary sidelobe levels. By minimizing a re-weighted objective function based on the magnitudes of the elements in the beamforming weight vector iteratively, the proposed method selects certain antennas in an array to satisfy the prescribed beampattern specifications precisely. Interestingly, a sparse array with fewer antennas (compared to other methods) is produced. This method can design non-uniformly spaced arrays with inter-element spacings larger than one half-wavelength, without the appearance of grating lobes in the resulting beampattern. Simulations are shown using arrays of up to a few hundred antennas to illustrate the practicality of the proposed method.
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TL;DR: In this article, a compact U-slot microstrip patch antenna with reconfigurable polarization is proposed for wireless local area network (WLAN) applications, which enables switching between linear and circular polarization by using a PIN diode and a capacitor located on the U- slot.
Abstract: A compact U-slot microstrip patch antenna with reconfigurable polarization is proposed for wireless local area network (WLAN) applications. PIN diodes are appropriately positioned to change the length of the U-slot arms, which alters the antenna's polarization state. Two antenna prototypes with identical dimensions are designed, fabricated and measured. The first antenna prototype enables switching between linear and circular polarization by using a PIN diode and a capacitor located on the U-slot. The second antenna prototype uses two PIN diodes to switch between the two circular polarization senses. A good impedance match (S11 ≤-10 dB) for both linear and circular polarization is achieved from 5.725 to 5.85 GHz, a band typically used for WLAN applications, and the 3 dB axial ratio bandwidth is greater than 2.8%. Details of the simulated and measured reflection coefficient, axial ratio, gain and radiation patterns are presented.
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TL;DR: In this paper, a planar ultrawideband (UWB) antenna with band notched characteristics is presented, which is suitable for UWB applications due to its compact size and high performance.
Abstract: A compact planar ultrawideband (UWB) antenna with band notched characteristics is presented. Modification in the shape of radiation element and ground plane with two symmetrical bevel slots on the lower edge of the radiation element and on the upper edge of the ground plane makes the antenna different from the rectangular printed monopole. These slots improve the input impedance bandwidth and the high frequency radiation characteristics. With this design, the reflection coefficient is lower than 10 dB in the 3.1-10.6 GHz frequency range and radiation pattern is similar to dipole antenna. With the inclusion of an additional small radiation patch, a frequency-notched antenna is also designed and good out of band performance from 5.0-6.0 GHz can be achieved. Measured results confirm that the antenna is suitable for UWB applications due to its compact size and high performance. Also an approximate empirical expression to calculate the lowest resonant frequency is proposed.
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TL;DR: In this article, a planar antenna array based on the substrate integrated waveguide (SIW) scheme is presented for 60-GHz band system applications, which consists of one compact SIW 12-way power divider and 12 radiating SIWs each supporting 12 slots, and a 50-? conductor-backed coplanar waveguide integrated with CBCPW-to-SIW transition is directly used as the input of the antenna array.
Abstract: An effective development of a class of low-cost planar antenna arrays having a high reproducibility is presented for 60-GHz band system applications. The proposed antenna arrays, based on the substrate integrated waveguide (SIW) scheme, consists of one compact SIW 12-way power divider and 12 radiating SIWs each supporting 12 radiating slots. A 50-? conductor-backed coplanar waveguide (CBCPW) integrated with CBCPW-to-SIW transition is directly used as the input of the antenna array, thus allowing to accommodate other circuits or MMICs at a minimum cost. An antenna array prototype was implemented on Rogers RT/Duroid 6002 substrate with thickness of 20 mils by our standard PCB process. Measured gain is about 22 dBi with a side lobe suppression of 25 dB in the H-plane and 15 dB in the E-Plane while the bandwidth for the 10-dB return loss is 2.5 GHz.
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TL;DR: In this paper, a dual-band single-feed circularly polarized, S-shaped slotted patch antenna with a small frequency-ratio is proposed for GPS applications, where a single microstrip feed-line is underneath the center of the coupling aperture groundplane.
Abstract: A dual-band single-feed circularly polarized, S-shaped slotted patch antenna with a small frequency-ratio is proposed for GPS applications. An S-shaped slot is cut at the centre of a square patch radiator for dual-band operation. A single microstrip feed-line is underneath the center of the coupling aperture ground-plane. The frequency-ratio of the antenna can be controlled by adjusting the S-shaped slot arm lengths. The measured 10-dB return loss bandwidths for the lower and upper-bands are 16% (1.103-1.297 GHz) and 12.5% (1.444-1.636 GHz), respectively. The measured 3-dB axial-ratio (AR) bandwidth is 6.9% (1.195-1.128 GHz) for the lower-band and 0.6% (1.568-1.577 GHz) for the upper-band. The measured gain is more than 5.0 dBic over both the bands. The measured frequency-ratio is 1.28. The overall antenna size is 0.46 ?o × 0.46?o × 0.086?o at 1.2 GHz.
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TL;DR: In this paper, a new tag geometry combining folded conductors and tuning slots is discussed through numerical analysis and extensive experimentation also including the integration of a passive motion detector, which can be applied to any part of the body.
Abstract: Design of effective wearable tags for UHF RFID applications involving persons is still an open challenge due to the strong interaction of the antenna with the human body which is responsible of impedance detuning and efficiency degradation. A new tag geometry combining folded conductors and tuning slots is here discussed through numerical analysis and extensive experimentation also including the integration of a passive motion detector. The achieved designs, having size comparable with a credit card, may be applied to any part of the body. The measured performance indicates a possible application of these body-worn tags for the continuous tracking of human movements in a conventional room.
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TL;DR: In this paper, an improved antenna array for radar-based breast cancer imaging was presented, which was achieved by increasing the number of antennas in the array to 31 elements, as well as by improving the antenna design itself.
Abstract: This paper presents an improved antenna array for radar-based breast cancer imaging. The improvement was achieved by increasing the number of antennas in the array to 31 elements, as well as by improving the antenna design itself. Using an experimental setup, with homogeneous curved breast phantoms, we have demonstrated substantial imaging improvement with the new antenna array. The new system is also able to detect 7 mm-diameter tumor phantoms in any location within the breast, even as close as 4 mm from the skin layer. Additionally, we have shown good imaging results in low-contrast scenarios, where the dielectric contrast between tumor and normal tissue was reduced to 2:1. Presented results clearly demonstrate the large impact of antenna's characteristics on imaging performance.
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TL;DR: In this paper, a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW) was used for circularly polarized square slot antenna.
Abstract: A novel design is described for a circularly polarized square slot antenna (CPSSA). Circular polarization (CP) operations can be attained using a lightening-shaped feedline protruded from the signal line of the feeding coplanar waveguide (CPW). The CP bandwidth can be significantly enhanced by implanting a pair of inverted-L grounded strips into the slot and adjusting the dimensions of the lightening-shaped feedline, whereas the impedance bandwidth can be greatly enlarged through tuning embedded vertical and horizontal stubs. The designed antenna was measured to exhibit a CP bandwidth of as high as 48.8%.
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TL;DR: In this paper, an all-metal flared-notch array element in both single and dual-polarization configurations is presented for an ultrawideband radiator with an operational bandwidth of 12:1 for broadside scan and 8:1 at a 45-degree scan in all planes.
Abstract: Simulations and measurements are presented for an all-metal flared-notch array element in both single and dual-polarization configurations. The ultrawideband radiator exhibits an operational bandwidth of 12:1 for broadside scan and 8:1 bandwidth at a 45-degree scan in all planes, maintaining active VSWR<;2. The feed consists of a direct coax-to-slot-line transition that mounts directly into the base of the radiator. The all-metal flared-notches are machined from common metal stock and fed via SMA coaxial connectors. No soldering is required for any part of the design-including the feed-and assembly is simple and modular. The array parts are machined using a high-precision wire-EDM cutting technology, ensuring that measurements (in the 700 MHz-9 GHz range) are repeatable and give close agreement with theory, even through multiple assembly cycles of the modular construction system. This paper presents results for a 32-element linear array of horizontal elements and also an 8 × 8 planar array of dual-polarized elements, comparing measurements with full-wave simulations of the complete finite array structures.
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TL;DR: In this paper, the leakage loss of SIW structures increases with the distance between the via-holes or via-slots, and this leakage loss is studied in detail and used to design a periodic leaky-wave antenna.
Abstract: Substrate integrated waveguides (SIW) are built up of periodically arranged metallic via-holes or via-slots The leakage loss of SIW structures increases with the distance between the via-holes or via-slots An open periodic waveguide with a large via distance supports the propagation of leaky-wave modes and can thus be used for the design of a leaky-wave antenna In this paper, this leakage loss is studied in detail and used to design a periodic leaky-wave antenna The proposed concept represents an excellent choice for applications in the millimeter-wave band Due to its versatility, the finite difference frequency domain method for periodic guided-wave or leaky-wave structures is used to analyze the characteristics of the proposed periodic leaky-wave antenna Two modes (TE10 and TE20) are investigated and their different leaky-wave properties are analyzed Based on the proposed leaky-mode analysis method, a novel periodic leaky-wave antenna at 28-34 GHz is designed and fabricated
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TL;DR: In this paper, a high-gain cavity resonance antenna (CRA), employing highly-reflective patch-type superstrates, is modeled and analyzed using the transverse equivalent network (TEN) model and the well known simple ray-tracing method.
Abstract: Results of modeling, design, simulation and fabrication are presented for a high-gain cavity resonance antenna (CRA), employing highly-reflective patch-type superstrates. In order to determine the resonant conditions, the antenna is first analyzed using the transverse equivalent network (TEN) model, as well as the well known simple ray-tracing method. Prior to that, a highly-reflective patch-type frequency selective surface (FSS) is designed in order to be employed as the superstrate layer of the CRA. Next, a 2.5-D full-wave analysis software package, based on the method of moments (ANSOFT Designer v4.0), is utilized to analyze the antenna structure. Using this full-wave analyzer, the input impedance properties of an actual antenna are investigated as well. Then, a 3-D full-wave analyzer, based on the finite element method (ANSOFT HFSS), is used to extract the directivity and radiation patterns of the CRA, taking into account the finiteness of the substrate, superstrate and ground plane. Some previously unaddressed issues, such as the effects of the FSS superstrate on the input impedance characteristics of the probe-fed microstrip patch antenna, acting as the excitation source of the CRA are also studied. The effects of the highly-reflective FSS superstrate size on the CRA directivity, and explicitly its aperture efficiency, are investigated as well. A comparative study is also performed between CRAs with patch-type FSS and high permittivity dielectric superstrates. Measurement results are provided to support the modelings and simulations.
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TL;DR: In this paper, a four-symbol modulation is created by repeated switching of phase shifters in a phased array, in a technique known as directional modulation (DM), where phase shifts are chosen to minimize the bit error rate (BER) in a line-of-sight channel in a desired direction while maximizing the BER elsewhere.
Abstract: A four-symbol modulation is created by repeated switching of phase shifters in a phased array, in a technique known as directional modulation (DM). The phase shifts are chosen to minimize the bit error rate (BER) in a line-of-sight channel in a desired direction while maximizing the BER elsewhere. A DM transmitter is demonstrated in an anechoic chamber, and results are compared with a traditional baseband QPSK modulation using the same phased array. Experiments indicate that the DM transmitter creates a narrower region of low BERs around the desired direction than the traditional phased array while maintaining high BERs in the sidelobe regions.
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TL;DR: The specific problems encountered in the design of near- field focused planar microstrip arrays for RFID (Radio Frequency IDentification) readers are described and improvements with respect to conventional far-field focused arrays (equal phase arrays) are discussed and quantified.
Abstract: The specific problems encountered in the design of near-field focused planar microstrip arrays for RFID (Radio Frequency IDentification) readers are described. In particular, the paper analyzes the case of a prototype operating at 2.4 GHz, which has been designed and characterized. Improvements with respect to conventional far-field focused arrays (equal phase arrays) are discussed and quantified.
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TL;DR: In this paper, single-negative magnetic metamaterials are used in order to reduce mutual coupling between high-profile antennas used in multiple-input multiple-output (MIMO) systems.
Abstract: Single-negative magnetic metamaterials are used in order to reduce mutual coupling between high-profile antennas used in multiple-input multiple-output systems. The magnetic permeability of the developed single-negative inclusions have negative effective response over a specific frequency band. The inclusions considered here are composed of broadside coupled split-ring resonators. The single-negative magnetic inclusions are inserted between closely-spaced high-profile monopole antenna elements. It is shown that mutual coupling between the antenna elements can be reduced significantly by incorporating such magnetic inclusions. Effective response of the constitutive parameters of the developed magnetic inclusions are incorporated within the numerical models. Good agreement is obtained between the experimental and numerical results.
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TL;DR: An electronically reconfigurable transmitarray device at 12 GHz is presented in this work and the proposed reconfigurability to the transmitarray structure is examined.
Abstract: An electronically reconfigurable transmitarray device at 12 GHz is presented in this work. This paper highlights the functioning of this kind of device and thoroughly examines the proposed reconfigurable transmitarray. The architecture is discussed along with the design and selection of all the constituting elements and the prototypes for all of them. In order to add reconfigurability to the transmitarray structure, 360° reflective phase shifters were designed, prototyped and validated for direct application. Eventually, a demonstrative prototype for an active transmitarray with phase shifters was assembled, and radiation pattern measurements were taken in an anechoic chamber to demonstrate the capabilities of this structure.