Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2008"
TL;DR: In this paper, a low profile cavity backed planar slot antenna has been described, which is completely constructed at a single substrate by using substrate integrated waveguide technique and grounded coplanar waveguide.
Abstract: A novel design method of low profile cavity backed planar slot antenna has been described in this paper. The whole antenna including backed cavity and feeding element is completely constructed at a single substrate by using substrate integrated waveguide technique and grounded coplanar waveguide. An example with 1.7% bandwidth has been presented, which has 5.4 dBi gain, 16.1 dB front-to-back ratio and -19 dB maximum cross polarized radiation level with its total thickness less than lambda0/50. The proposed antenna keeps good radiation performance of conventional cavity backed antenna and has advantages of conventional planar antenna including low profile, light weight, easy fabrication with low cost and convenient integration with planar circuit.
402 citations
TL;DR: In this article, a frequency reconfigurable microstrip patch antenna is presented, which is suitable for use in reducing the crosstalk from adjacent channels in multichannel system.
Abstract: A frequency reconfigurable microstrip patch antenna is presented. It is found that the incorporation of a U-slot in the patch can provide a flat input resistance and a linear input reactance across a wider bandwidth than the conventional patch antenna. By placing a variable capacitor and an inductor at the antenna input, the impedance matching frequency of the antenna can be varied. The fabricated prototype antenna attains a tunable frequency range from 2.6 to 3.35 GHz. The proposed antenna is simple in structure, and the control circuitry is placed underneath the ground plane. It is suitable for use in reducing the crosstalk from adjacent channels in multichannel system.
228 citations
TL;DR: In this paper, a low-cost 60 GHz switched-beam patch antenna array with Butler matrix network is developed and experimentally demonstrated, where four rectangular patches fed by inset microstrip lines are connected to the outputs of the Butler matrix for the 60 GHz operation.
Abstract: In this letter, a low-cost 60-GHz switched-beam patch antenna array with Butler matrix network is developed and experimentally demonstrated. In order to improve integration with the patch elements, a 4 times 4 planar Butler matrix is implemented in a low-dielectric substrate. The four rectangular patches fed by inset microstrip lines are connected to the outputs of the Butler matrix for the 60-GHz operation. Because of the fabrication tolerances, the operating frequency of the fabricated antenna shifts to 62 GHz. The radiation patterns measured at 62 GHz are in good agreement with the theoretical array factors. The antenna developed in this letter provides a cost-effective approach to implement an adaptive antenna for 60-GHz wireless communications.
201 citations
TL;DR: In this paper, a wide band patch antenna fed by an L-probe can be designed for dual-and multi-band application by cutting U-slots on the patch.
Abstract: A wide band patch antenna fed by an L-probe can be designed for dual- and multi-band application by cutting U-slots on the patch. Simulation and measurement results are presented to illustrate this design.
198 citations
TL;DR: In this article, a leaky-wave antenna is demonstrated and developed at Ka-band in this work based on the newly proposed half-mode substrate integrated waveguide (HWSIW).
Abstract: A novel leaky-wave antenna is demonstrated and developed at Ka-band in this work based on the newly proposed half-mode substrate integrated waveguide (HWSIW). This antenna is accurately simulated by using a full-wave electromagnetic simulator and then fabricated through a single-layer printed circuit board (PCB) process. Wide bandwidth and a quasi-omnidirectional radiation pattern are obtained. The proposed antenna is therefore a good candidate for millimeter-wave applications. Measured results are in good agreement with simulated results.
197 citations
TL;DR: In this article, a compact antipodal Vivaldi antenna for ultrawide-band (UWB) applications is proposed, which operates across the entire UWB spectrum from 3.1 to 10.6 GHz, and also has low cross-polarization levels and reasonable gain values over the same frequency band.
Abstract: A compact antipodal Vivaldi antenna for ultrawide-band (UWB) applications is proposed. The antenna operates across the entire UWB spectrum from 3.1 to 10.6 GHz, and also has low cross-polarization levels and reasonable gain values over the same frequency band. Two different substrates, Rogers RO3006 and FR4, are considered, and results regarding return loss, far field pattern, phase response, group delay, and gain are presented.
192 citations
TL;DR: In this article, a new wideband circularly polarized square slot antenna (CPSSA) with a coplanar waveguide (CPW) feed was proposed, which features two inverted-L grounded strips around two opposite corners of the slot and a widened tuning stub protruded into the slot from the signal strip of the CPW.
Abstract: This paper presents a new wideband circularly polarized square slot antenna (CPSSA) with a coplanar waveguide (CPW) feed. The proposed antenna features two inverted-L grounded strips around two opposite corners of the slot and a widened tuning stub protruded into the slot from the signal strip of the CPW. Broadside circular-polarization (CP) radiation can be easily obtained using a simple design procedure. For the optimized antenna prototype, the measured bandwidth with an axial ratio (AR) of less than 3 dB is larger than 25% and the measured VSWR les 2 impedance bandwidth is as large as 52%.
185 citations
TL;DR: In this paper, a tunable patch antenna made of a slotted rectangular patch loaded by a number of posts close to the patch edge is proposed, which is short circuited to the ground plane via a set of PIN diode switches.
Abstract: In this letter, we propose a tunable patch antenna made of a slotted rectangular patch loaded by a number of posts close to the patch edge. The posts are short circuited to the ground plane via a set of PIN diode switches. Simulations and measurements verify the possibility of tuning the antenna in subbands from 620 to 1150 MHz. Good matching has been achieved over most of the bands. Other performed designs show that more than one octave can be achieved using the proposed structure.
167 citations
TL;DR: In this paper, a dual wideband CPW-fed modified Koch fractal printed slot antenna is proposed for WLAN and WiMAX operations, which exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi.
Abstract: A dual wide-band CPW-fed modified Koch fractal printed slot antenna, suitable for WLAN and WiMAX operations, is proposed in this paper. Here, the operating frequency of a triangular slot antenna is lowered by the Koch iteration technique resulting in a compact antenna. Studies on the impedance and radiation characteristics of the proposed antenna indicate that a modified Koch fractal slot antenna has an impedance bandwidth from 2.38 to 3.95 GHz and 4.95-6.05 GHz covering 2.4/5.2/5.8 GHz WLAN bands and the 2.5/3.5/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Empirical relations are deduced and compared with the results.
152 citations
TL;DR: In this paper, a reconfigurable reflectarray cell operating at 12 GHz and fabricated in a monolithic MEMS process is presented, which allows reconfiguration of the reflection phase over the full 360deg range, while alleviating the impact of MEMS and bias voltage tolerances on device performances.
Abstract: In this letter, we present a reconfigurable reflectarray cell operating at 12 GHz and fabricated in a monolithic MEMS process. A 5-bit digital control allows reconfiguration of the reflection phase over the full 360deg range, while alleviating the impact of MEMS and bias voltage tolerances on the device performances. The designed reflectarray cell exhibits low frequency phase error (large bandwidth) and excellent measured reflection loss (-0.3 dB) with regard to state-of-the-art. Close agreement between measurements and full-wave simulations is observed.
151 citations
TL;DR: In this paper, a printed circular disc monopole antenna with an L-shaped slot cut out of the ground, forming a defected ground plane, is proposed, which exhibits a measured -10 dB S 11 bandwidth of 600 MHz from 2.68 to 3.28 GHz, and a bandwidth of 4.84 GHz from 4.74 to 9.58 GHz.
Abstract: A compact multiband antenna is proposed that consists of a printed circular disc monopole antenna with an L-shaped slot cut out of the ground, forming a defected ground plane. Analysis of the current distribution on the antenna reveals that at low frequencies the addition of the slot creates two orthogonal current paths, which are responsible for two additional resonances in the response of the antenna. By virtue of the orthogonality of these modes the antenna exhibits orthogonal pattern diversity, while enabling the adjacent resonances to be merged, forming a wideband low-frequency response and maintaining the inherent wideband high-frequency response of the monopole. The antenna exhibits a measured -10 dB S 11 bandwidth of 600 MHz from 2.68 to 3.28 GHz, and a bandwidth of 4.84 GHz from 4.74 to 9.58 GHz, while the total size of the antenna is only 24 times 28.3 mm. The efficiency is measured using a modified Wheeler cap method and is verified using the gain comparison method to be approximately 90% at both 2.7 and 5.5 GHz.
TL;DR: In this paper, the design and measured results of a 2 times 2 microstrip line-fed U-slot rectangular antenna array are presented, where the U slot patches and the feeding network are placed on the same layer, resulting in a very simple structure.
Abstract: The design and measured results of a 2 times 2 microstrip line fed U-slot rectangular antenna array are presented. The U-slot patches and the feeding network are placed on the same layer, resulting in a very simple structure. The advantage of the microstrip line fed U-slot patch is that it is easy to form the array. An impedance bandwidth (VSWR < 2) of 18% ranging from 5.65 GHz to 6.78 GHz is achieved. The radiation performance including radiation pattern, cross polarization, and gain is also satisfactory within this bandwidth. The measured peak gain of the array is 11.5 dBi. The agreement between simulated results and the measurement ones is good. The 2 times 2 array may be used as a module to form larger array.
TL;DR: In this article, a printed monopole antenna with two steps and a circular slot for ultrawide band (UWB) applications is presented, which has a wide frequency bandwidth of 8.4 GHz.
Abstract: This letter presents a printed monopole antenna with two steps and a circular slot for ultrawide band (UWB) applications. The proposed antenna is fabricated and tested. The proposed antenna has a wide frequency bandwidth of 8.4 GHz starting from 3 GHz up to 11.4 GHz for a return loss (S_11) of less than - 10dB and gain flatness over the frequency range. Measured results show also that the proposed antenna features satisfactory radiation characteristics within the achieved impedance bandwidth. By introducing a simple and proper narrow slot in the radiating element, frequency-notched characteristics can be obtained and a good band-notched performance in the 56 GHz band can be achieved.
TL;DR: In this article, the first application of Koch prefractal elements in a miniaturized wideband antenna design is presented, and the proposed LPKDA is validated through a fabricated proof-of-concept prototype that exhibited approximately 12% size reduction with minimal degradation in the impedance and pattern bandwidths.
Abstract: Koch-shaped dipoles are introduced for the first time in a wideband antenna design and evolve the traditional Euclidean log-periodic dipole array into the log-periodic Koch-dipole array (LPKDA). Antenna size can be reduced while maintaining its overall performance characteristics. Observations and characteristics of both antennas are discussed. Advantages and disadvantages of the proposed LPKDA are validated through a fabricated proof-of-concept prototype that exhibited approximately 12% size reduction with minimal degradation in the impedance and pattern bandwidths. This is the first application of Koch prefractal elements in a miniaturized wideband antenna design.
TL;DR: In this article, the authors investigated the application of EBG radar absorbing material (RAM) to asymmetric ridged waveguide slot antenna array to reduce its backward RCS and measured results show that performance of the antenna array is preserved when EBG RAM is used.
Abstract: This letter investigates the application of EBG radar absorbing material (RAM) to asymmetric ridged waveguide slot antenna array to reduce its backward RCS. The EBG RAM is based on the mushroom-like EBG structure loaded with lumped resistances. A ridged waveguide slot antenna array with 4 times 10 slot elements was designed and built, part of the metal ground plane of the array is replaced with this EBG RAM. The measured results show that performance of the antenna array is preserved when EBG RAM is used. At working frequency the backward RCS of antenna array with EBG RAM has dramatically reduced than that of the common antenna array.
TL;DR: In this article, an improved model for analyzing electrically small NRI-TL antennas is proposed, that highlights the methods that enable these antennas to offer a good impedance match and a high radiation efficiency compared to previously reported designs.
Abstract: An improved model for analyzing electrically small NRI-TL antennas is proposed, that highlights the methods that enable these antennas to offer a good impedance match and a high radiation efficiency compared to previously reported designs. An even-odd mode analysis reveals that the antenna supports a predominately even-mode current on the vertical vias, allowing the antenna to be modeled using a multiple folded monopole topology, which provides a substantial increase in the radiation resistance of the antenna. This, together with the top-loading effect of the microstrip line on the vias, enables the antenna to be matched to 50 Omega without the use of an external matching network, while maintaining a high radiation efficiency. The validity of the proposed model is confirmed with a fabricated prototype, that consists of four microstrip zero-degree NRI-TL unit cells with dimensions of lambda0/10 times lambda0/10 times lambda/20 over a 0.45lambda0 times 0.45lambda0 ground plane. The antenna's performance is verified by full-wave simulations and experimental data obtained at 3.1 GHz, which yield a vertical linear electric field polarization, a measured -10dB return-loss bandwidth of 53 MHz and a measured efficiency of 70%.
TL;DR: In this paper, a modified microstrip-fed ultrawideband (UWB) planar monopole antenna with variable frequency band-notch characteristic is presented, by inserting two slots in the both sides of microstrip feedline on the ground plane.
Abstract: A novel modified microstrip-fed ultrawideband (UWB) planar monopole antenna with variable frequency band-notch characteristic is presented. By inserting two slots in the both sides of microstrip feedline on the ground plane, much wider impedance bandwidth can be produced. A modified H-shaped conductor-backed plane with variable dimensions is used in order to generate the frequency band-stop performance and control its characteristics such as band-notch frequency and its bandwidth. The designed antenna has a small size of 22 x 22 mm2 and operates over the frequency band between 3.1 and 14 GHz for VSWR < 2 while showing the band rejection performance in the frequency band of 5.1 to 5.9 GHz.
TL;DR: To improve the performance of microstrip antenna array, a new configuration of micro Strip series-fed tape array is designed that has a better VSWR characteristic and the precorrected fast Fourier transform (P-FFT) method is employed to accelerate the entire computational process.
Abstract: To improve the performance of microstrip antenna array, a matching-in-step (MIS) configuration of microstrip series-fed taper array is designed. Compared to the traditional one, the novel antenna array has a better VSWR characteristic. The design procedure of the MIS antenna array is discussed in detail, and some valuable results are acquired. Numerical results are obtained and a very good agreement is observed between experimental and simulated results of such arrays.
TL;DR: The backscattered, radiated field by a UHF Transponder is described by means of a simple and complete analytical expression, and the tag radar cross section (RCS) and the bit error rate (BER) at the Reader are evaluated by Means of the achieved formula.
Abstract: The investigation of the modulated, backscattered contribution from UHF RFID Transponders is a crucial issue for the reliable evaluation of the behavior and the performance of RFID systems. The backscattered, radiated field by a UHF Transponder is described by means of a simple and complete analytical expression. The tag radar cross section (RCS) and the bit error rate (BER) at the Reader are evaluated by means of the achieved formula, and the results are in perfect agreement with previous available publications.
TL;DR: In this article, a harmonic radar system is proposed to track the migration of the Emerald Ash Borer (EAB) in the 11.812 GHz band, which is composed of a compact radar unit and a passive RF tag for mounting on the insect.
Abstract: Harmonic radar systems provide an effective modality for tracking insect behavior. This letter presents a harmonic radar system proposed to track the migration of the Emerald Ash Borer (EAB). The system offers a unique combination of portability, low power and small tag design. It is comprised of a compact radar unit and a passive RF tag for mounting on the insect. The radar unit transmits a 5.96 GHz signal and detects at the 11.812 GHz band. A prototype of the radar unit was built and tested, and a new small tag was designed for the application. The new tag offers improved harmonic conversion efficiency and much smaller size as compared to previous harmonic radar systems for tracking insects. Unlike RFID detectors whose sensitivity allows detection up to a few meters, the developed radar can detect a tagged insect up to 58 m (190 ft).
TL;DR: In this article, a planar inverted cone antenna (PICA) based wide-slot antenna is proposed for ultrawideband (UWB) with a double-layer substrate.
Abstract: A novel ultrawideband (UWB) printed wide-slot antenna is presented. The design is based on the planar inverted cone antenna (PICA), introduced by Suh. The presented design comprises PICA-like structures, etched from a double-layer substrate. Compared to the original PICA, it is lower in profile, more compact and maintains comparable performance. A prototype integrated in a printed circuit board and fed by a microstrip line is fabricated and measured. The results show that the proposed antenna provides at least 13:1 impedance bandwidth at 10-dB return loss.
TL;DR: In this paper, simple and efficient numerical procedures using singularity cancellation methods are presented for evaluating singular and near-singular potential integrals, four different transformations are compared and the advantages of the radial-angular transform are demonstrated.
Abstract: Simple and efficient numerical procedures using singularity cancellation methods are presented for evaluating singular and near-singular potential integrals Four different transformations are compared and the advantages of the radial-angular transform are demonstrated A method is then described for optimizing this integration scheme
TL;DR: In this paper, the authors presented an optically transparent antenna made of conductive AgHT coated film, with an improved efficiency by applying a highly conductive coating or metallization in the form of a very narrow strip to selective antenna areas of high current density.
Abstract: This letter presents an optically transparent antenna, which is made of conductive AgHT coated film, with an improved efficiency by applying a highly conductive coating or metallization in the form of a very narrow strip to selective antenna areas of high current density. A measurement showed that the proposed method improved the maximum gain of a fabricated transparent antenna using the AgHT film from -5 dBi to 0 dBi at 2.2 GHz while preserving much of the optical transparency. A 3D electromagnetic model using a full-wave method of moments was developed to investigate the effect of width of the highly conductive narrow strip on the efficiency of the transparent antenna.
TL;DR: In this paper, an approach for designing a tunable and steerable antenna model is presented based on a wideband bow-tie radiating element mounted above an active artificial magnetic conductor (AMC).
Abstract: In this letter, an approach for designing a tunable and steerable antenna is presented. The antenna model is based on a wideband bow-tie radiating element mounted above an active artificial magnetic conductor (AMC). The AMC geometry consists of a frequency selective surface (FSS) printed on a thin grounded dielectric slab in which some chip-set varactor diodes are placed between the metallic elements and the backing plane through vias. The resulting antenna can be tuned over the S-Band by simply changing all varactor capacitances through an appropriate biasing voltage. Moreover, this structure can operate a beam scanning over each working frequency by applying an appropriate biasing voltage to the active elements of the AMC surface in accordance to leaky radiation principles. The low-profile active antenna is characterized by an overall thickness of 5.32 mm, which corresponds to approximately lambda/24 at the center of the operating band.
TL;DR: In this article, a port-to-port isolation technique suitable for a two-antenna system positioned at the top corner of a mobile phone is presented, where the chosen planar inverted-F antennas (PIFAs) are intended to operate in the UMTS band [1.92-2.17] GHz and more precisely in the UHF band for diversity purpose.
Abstract: In this letter, a novel port-to-port isolation technique suitable for a two-antenna system positioned at the top corner of a mobile phone is presented. The chosen planar inverted-F antennas (PIFAs) are intended to operate in the UMTS band [1.92-2.17] GHz and more precisely in the UMTS Rx band for diversity purpose. First, the distance between the PIFAs is severely reduced to 4 mm (0.027 lambda0) in order to obtain a very compact system. This proximal placement causes an increase of the insertion loss between the feeding ports of the PIFAs and therefore degrades the overall diversity performance of the two-antenna system. To compensate for this effect, the neutralization technique previously proposed by the same authors is implemented. Then, a novel way to implement this technique is studied to further improve the PIFAs' port-to-port isolation. It consists in achieving the neutralization of the antennas trough folded lines connected to the printed circuit board (PCB). A new prototype is fabricated and measured. The S-parameters and the total efficiency are presented. Additionally, the most important diversity metrics are computed to evaluate the potential of this novel two-antenna system for diversity applications in the UMTS Rx mode.
TL;DR: In this paper, a novel dielectric resonator antenna design is presented for wideband applications by using an optimized H-shaped across section and an optimized trapezoidal patch adhered on the concave surface of the resonator as a feeding mechanism, achieving an impedance bandwidth of about 62% (for VSWR les 2), covering the frequency range of 3.6-6.85 GHz.
Abstract: A novel dielectric resonator antenna design is presented for wideband applications in this letter. By using a dielectric resonator with an optimized H-shaped across section and an optimized trapezoidal patch adhered on the concave surface of the resonator as a feeding mechanism, an impedance bandwidth of about 62% (for VSWR les 2) , covering the frequency range of 3.6-6.85 GHz, is achieved. The measured results in terms of bandwidth and radiation pattern agree well with the simulated ones, confirming the theoretical design.
TL;DR: In this paper, a low-cost patch antenna phased array is demonstrated with analog beam steering without using phase shifters, which can greatly reduce the cost of a phased array system and will enable the wide-scale deployment of phased arrays in low-end commercial products.
Abstract: In this letter, a low-cost patch antenna phased array is demonstrated with analog beam steering without using phase shifters. This novel technique can greatly reduce the cost of a phased-array system and will enable the wide-scale deployment of phased arrays in low-end commercial products. In the presented three-element phased array, the center (driven) antenna is fed by an RF source and the two neighboring (passive) antennas are excited through the mutual coupling from the center antenna. The phase shifts between the antenna elements are achieved by changing the reactance of the capacitors loading the two passive antennas. A phased array using this novel technique is designed, fabricated, and measured at 3 GHz with a bandwidth of 1.8%. This phased array is shown to be able to steer the antenna beam from 20 to 20 degrees in an analog fashion. The measured radiation patterns of this phased array closely match the theoretical calculation and full-wave simulation results.
TL;DR: In this paper, a circuit model capable of predicting the bandwidth and resonance frequency of a well-known artificial magnetic conductor (AMC) is proposed, which is composed of an array of Jerusalem cross-shaped frequency selective surfaces (FSSs) (JC-FSS) deployed on a thin PEC-backed dielectric slab.
Abstract: This letter proposes a circuit model capable of predicting the bandwidth and resonance frequency of a well-known artificial magnetic conductor (AMC). The AMC is composed of an array of Jerusalem cross-shaped frequency selective surfaces (FSSs) (JC-FSS) deployed on a thin PEC-backed dielectric slab. The model benefits from the static (Quasi-TEM) closed-form equations, available in literature for the characteristic impedance of microstrip transmission lines. These equations enable the model to incorporate the influences of the slab thickness on the FSS impedance, a feature that the available models have not been able to offer exactly. In order to check the competence of the model, some sample AMCs are designed by the model, and their properties are verified by numerical analysis.
TL;DR: In this article, the authors proposed a novel technique to reduce the size of microstrip patch antennas by etching the patch edges according to Koch curves as inductive loading and inserting the Sierpinski carpets into the patch as slot loading.
Abstract: A novel technique to reduce the size of microstrip patch antennas is proposed. By etching the patch edges according to Koch curves as inductive loading, and inserting the Sierpinski carpets into the patch as slot loading, it is experimentally found that the resonant frequency of the patch can be greatly lowered, and the higher the iteration order of the fractal shapes, the lower the resonant frequency becomes. And this property can be utilized to reduce the size of the microstrip patch antennas. It is also found that, the radiation patterns of the proposed fractal-shaped antennas maintained because of the self-similarity and centro- symmetry of the fractal shapes. The patches derived from this technique can find applications in integrated low-profile wireless communication systems.
TL;DR: In this article, a planar inverted F antenna (PIFA)-based tunable internal antenna is proposed for personal communication handset applications, which can cover following frequency bands: DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), WLAN (5.2 and 5.8 GHz), Bluetooth (2400-2480 MHz) and ISM band (2500-2700 MHz).
Abstract: A simple planar inverted F antenna (PIFA)-based tunable internal antenna is proposed for personal communication handset applications. The antenna can covers following frequency bands: DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), WLAN (5.2 and 5.8 GHz), Bluetooth (2400-2480 MHz), and ISM band (2500-2700 MHz). Varactor diode is used to get tuning over the wide frequency range. Overall size of the antenna is 19.5 mm times 9.5 mm times 4 mm (0.741 cm3) makes it suitable for 4 G handsets and can be easily integrated inside commercial mobile handsets. The antenna was designed and optimized by using CST microwave studio program. Measured return losses (S11) and radiation patterns of the antenna were carried on Anritsu 37377C vector network analyzer and in standard anechoic chamber room. Return loss of the antenna is within acceptable limit with reasonable radiation performance.