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Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2010"


Journal ArticleDOI
TL;DR: In this paper, a configuration of uniplanar compact electromagnetic band-gap (UC-EBG) structures is proposed to reduce mutual coupling between the radiating elements of an antenna array.
Abstract: Reducing mutual coupling between elements of an antenna array is one of the main topics in array designs. The use of electromagnetic band-gap (EBG) structures built by microstrip technology is an attractive way to mitigate the mutual coupling problem. This letter describes a novel configuration of uniplanar compact electromagnetic band-gap (UC-EBG) structures to reduce mutual coupling between the radiating elements. The idea is to use the UC-EBG structures placed on top of the antenna layer. The main objective is to reduce both the element separation and the mutual coupling between the patch antennas, which in turn increases antenna directivity. The proposed configuration eliminates drawbacks of similar structures presented in previous works.

312 citations


Journal ArticleDOI
TL;DR: In this paper, a novel structure based on complementary split-ring resonators (SRRs) is introduced to reduce the mutual coupling between two coplanar microstrip antennas that radiate in the same frequency band.
Abstract: A novel structure based on complementary split-ring resonators (SRRs) is introduced to reduce the mutual coupling between two coplanar microstrip antennas that radiate in the same frequency band. The new unit cell consists of two complementary SRR inclusions connected by an additional slot. This modification improves the rejection response in terms of bandwidth and suppression. The filtering characteristics of the band-gap structure are investigated using dispersion analysis. Using the new structure, it was possible to achieve a 10-dB reduction in the mutual coupling between two patch antennas with a separation of only 1/4 free-space wavelength between them. Since the proposed structures are broadband, they can be used to minimize coupling and co-channel interference in multiband antennas.

312 citations


Journal ArticleDOI
TL;DR: A coplanar waveguide (CPW)-fed planar monopole antenna with triple-band operation for WiMAX and WLAN applications is presented in this article, which occupies a small size of 25(L) × 25(W) × 0.8(H) mm3.
Abstract: A coplanar waveguide (CPW)-fed planar monopole antenna with triple-band operation for WiMAX and WLAN applications is presented. The antenna, which occupies a small size of 25(L) × 25(W) × 0.8(H) mm3, is simply composed of a pentagonal radiating patch with two bent slots. By carefully selecting the positions and lengths of these slots, good dual stopband rejection characteristic of the antenna can be obtained so that three operating bands covering 2.14-2.85, 3.29-4.08, and 5.02-6.09 GHz can be achieved. The measured results also demonstrate that the proposed antenna has good omnidirectional radiation patterns with appreciable gain across the operating bands and is thus suitable to be integrated within the portable devices for WiMAX/WLAN applications.

214 citations


Journal ArticleDOI
TL;DR: In this article, a rectenna design methodology combining electromagnetic simulation and harmonic balance analysis is presented, which consists of applying reciprocity theory to calculate the Thevenin equivalent circuit of the receiving antenna and optimizing the rectifying circuit parameters using HB analysis.
Abstract: A rectenna design methodology combining electromagnetic (EM) simulation and harmonic balance (HB) analysis is presented. It consists of applying reciprocity theory to calculate the Thevenin equivalent circuit of the receiving antenna and optimizing the rectifying circuit parameters using HB analysis. The method is demonstrated by designing a 2.45-GHz rectenna based on a square aperture-coupled patch antenna with dual linear polarization. A compact implementation is achieved by etching a cross-shaped slot on the patch surface leading to a 32.5% patch side reduction. Voltage-doubling circuits convert the received RF power from each port to dc permitting the rectenna to receive arbitrarily polarized signals. The circuit is optimized for low input power densities and a simulated maximum efficiency of 38.2% was obtained for 1.5 nWcm-2 input RF power density at 2.43 GHz.

196 citations


Journal ArticleDOI
Lin Dang1, Zhen Ya Lei1, Yong Jun Xie1, Gao Li Ning1, Jun Fan1 
TL;DR: In this article, a triple-band microstrip slot antenna is proposed for WLAN/WiMAX applications, which is composed of a microstrip feed line, a substrate, and a ground plane on which some simple slots are etched.
Abstract: A compact triple-band microstrip slot antenna applied to WLAN/WiMAX applications is proposed in this letter. This antenna has a simpler structure than other antennas designed for realizing triple-band characteristics. It is just composed of a microstrip feed line, a substrate, and a ground plane on which some simple slots are etched. Then, to prove the validation of the design, a prototype is fabricated and measured. The experimental data show that the antenna can provide three impedance bandwidths of 600 MHz centered at 2.7 GHz, 430 MHz centered at 3.5 GHz, and 1300 MHz centered at 5.6 GHz.

185 citations


Journal ArticleDOI
TL;DR: In this paper, electric and magnetic dipole antennas are introduced that are based on near-field resonant parasitic (NFRP) elements that are electrically coupled to the driven element and the proposed Huygens sources have one feed point, are well matched to 50 Ω, and have high radiation efficiencies.
Abstract: Electrically small electric and magnetic dipole antennas are introduced that are based on electric and magnetic near-field resonant parasitic (NFRP) elements that are electrically coupled to the driven element. By properly combining these two NFRP antenna types, electrically small Huygens sources are realized. The proposed Huygens sources have one feed point, are well matched to 50 Ω, and have high radiation efficiencies. Their predicted directivity patterns approach the known Huygens source theoretical limit.

166 citations


Journal ArticleDOI
TL;DR: In this article, a compact printed ultrawideband (UWB) monopole antenna with dual band-notched characteristics is presented, which has a small size of 20 × 18 mm2 and operates over the frequency band between 2.8 and 11.8 GHz for VSWR <; 2, with one notch frequency band at 3.3-3.6 GHz and another at 5.1-6 GHz for WLAN band.
Abstract: A compact printed ultrawideband (UWB) monopole antenna with dual band-notched characteristics is presented. By inserting two I-shaped notches in both sides of the microstrip feed line on the ground plane, additional resonances are excited, and hence the bandwidth is increased up to 123%. Two notched frequency bands are achieved by embedding a pair of Γ-shaped stubs in the radiation patch and a modified G-slot defected ground structure in the feeding line. The designed antenna has a small size of 20 × 18 mm2 and operates over the frequency band between 2.8 and 11.8 GHz for VSWR <; 2, with one notch frequency band at 3.3-3.8 GHz (WiMAX band) and the other at 5.1-6 GHz (WLAN band). The VSWR and radiation patterns of the fabricated antenna are presented, which prove that the designed antenna is a good candidate for various UWB applications.

165 citations


Journal ArticleDOI
TL;DR: In this paper, a dual-polarization coplanar waveguide (CPW)-fed slot antenna is proposed, where two orthogonal polarizations can be excited in a slot aperture by the same feeding CPW, and the -10-dB reflection coefficient bandwidths of two polarizations are 670 MHz (27.9%) for one polarization and 850 MHz (35.4%) for the other.
Abstract: A dual-polarization coplanar waveguide (CPW)-fed slot antenna is proposed in this letter. By exploiting the even and odd modes of a CPW structure, two orthogonal polarizations can be excited in a slot aperture by the same feeding CPW, which results in a compact dual-polarization antenna design with very good isolation between the ports. The -10-dB reflection coefficient bandwidths of two polarizations are 670 MHz (27.9%) for one polarization and 850 MHz (35.4%) for the other, and the isolation between the two ports in the WLAN band is better than -32.6 dB. The radiation pattern and efficiency of the proposed antenna are also measured, and radiation pattern data are compared with simulation results.

162 citations


Journal ArticleDOI
TL;DR: In this paper, a wideband circularly polarized (CP) trapezoidal dielectric resonator antenna (DRA) is investigated, which is simply excited by a single 45° inclined slot fed by a microstrip feed line.
Abstract: A wideband circularly polarized (CP) trapezoidal dielectric resonator antenna (DRA) is investigated in this letter. The DRA is simply excited by a single 45° inclined slot fed by a microstrip feed line. It is found that the 3-dB axial ratio (AR) bandwidth of the proposed antenna can be as wide as 21.5%. The antenna gain varies between 5.28 and 8.40 dBi across the antenna passband (3.11-3.86 GHz). This letter also presents a modified trapezoidal DRA that has a notch at its top. The modified version improves the impedance match, as the AR and gain remain almost unchanged. The reflection coefficient, AR, radiation pattern, and antenna gain of each proposed configuration are studied, and reasonable agreement between the measured and simulated results is observed.

152 citations


Journal ArticleDOI
TL;DR: In this paper, a planar monopole antenna with standard band-notched characteristic suitable for ultrawideband (UWB) applications is presented, consisting of a square slot patch with a vertical coupling strip, only occupying a small size of 15 (L) × 15 (W) × 1.6 (H) mm3.
Abstract: A compact planar monopole antenna with standard band-notched characteristic suitable for ultrawideband (UWB) applications is presented. This microstrip-fed antenna, consisting of a square slot patch with a vertical coupling strip, only occupies a small size of 15 (L) × 15 (W) × 1.6 (H) mm3. By properly designing the strip placed at the center of the patch, good frequency rejection performance of the antenna with a wide operating band from 3.05 to 11.15 GHz can be obtained. Compared to other designs, the antenna has a quite simple structure to make the band-notched property to reduce the effect caused by the frequency interference. Furthermore, fairly good omnidirectional radiation patterns and transmission responses both indicate that the proposed antenna is well suited to be integrated within various portable devices for UWB operation.

141 citations


Journal ArticleDOI
TL;DR: The synthesis examples that are presented show that the CLPSO algorithm outperforms the common PSO algorithms and a real-coded genetic algorithm (GA).
Abstract: We present unequally spaced linear array synthesis with sidelobe suppression under constraints to beamwidth and null control using a design technique based on a Comprehensive Learning Particle Swarm Optimizer (CLPSO). CLPSO utilizes a new learning strategy that achieves the goal to accelerate the convergence of the classical PSO. Numerical examples are compared to the existing array designs in the literature and to those found by the other evolutionary algorithms. The synthesis examples that are presented show that the CLPSO algorithm outperforms the common PSO algorithms and a real-coded genetic algorithm (GA).

Journal ArticleDOI
TL;DR: In this paper, a compact coplanar waveguide-fed patch antenna designed by simply embedding two types of shaped slots into a rectangular patch for achieving dual-band operation is presented.
Abstract: A compact coplanar waveguide (CPW)-fed patch antenna designed by simply embedding two types of shaped slots into a rectangular patch for achieving dual-band operation is presented. The use of embedded slots can effectively excite multiresonant modes together with good dual-impedance bandwidths, especially ultrawide for the upper bandwidth. By fabricating and measuring the prototype of the proposed optimal antenna, dual operating bands with 10-dB return-loss bandwidths of about 230 MHz centered at 2.42 GHz and of about 73% ranging from 4.8 to 9.62 GHz covering the required bandwidths of 2.4/5.2/5.8 GHz WLAN standards and the C-band satellite communication were obtained. Also, a stable monopole-like radiation pattern and an average antenna gain of 1.4 and 5.1 dBi, respectively, across the dual operating bands have been measured.

Journal ArticleDOI
TL;DR: In this article, a novel frequency reconfigurable antenna design using photoconductive silicon elements as optical switches is presented, and a new geometry for coupling the light energy onto the silicon switches is demonstrated.
Abstract: This letter presents a novel frequency reconfigurable antenna design using photoconductive silicon elements as optical switches. By illuminating these silicon elements with light of suitable wavelength, their physical properties can be altered from that of a semiconductor to almost metal-like, which in turn alters the radiation properties of the antenna structure. Our work builds on similar work conducted in the past, but goes further by demonstrating a new geometry for coupling the light energy onto the silicon switches, thereby facilitating conformal integration of such reconfigurable antennas into next-generation wireless devices. In this letter, we first present a theoretical model characterizing the behavior of silicon substrate under light illumination. We then present experimental results on a stripline circuit employing a single silicon switch under light illumination and compare the theoretical model to experimental measurements. Finally, a novel frequency reconfigurable antenna design utilizing our new coupling geometry is designed, and its experimentally measured RF performance is compared to numerical simulations.

Journal ArticleDOI
TL;DR: In this article, a multiband E-shaped printed monopole antenna for multiple-input-multiple-output (MIMO) system is presented, which can create a single resonance within the WLAN range.
Abstract: A novel multiband E-shaped printed monopole antenna for multiple-input-multiple-output (MIMO) system is presented. The proposed E-shaped monopole antenna can create a single resonance within the WLAN range. Placement of two slots within the E-shaped monopole antenna creates two extra resonances whose center frequencies can be adjusted by the E-shaped monopole and the slots parameters. The antenna parameters for WLAN application, covering 2.4, 5.4, and 5.8 GHz, are given. Various configurations of array of this E-shaped monopole antenna for MIMO application are also studied. It is shown that good MIMO performance can be achieved even for small element spacing. Simulation and measurement results are compared and discussed.

Journal ArticleDOI
TL;DR: In this article, a reconfigurable microstrip antenna is proposed for low-cost adaptive beam-switching applications, where a small patch-slot ring structure is used as the radiating element where an asymmetrical arrangement of p-i-n diodes is employed to switch the pattern in four directions.
Abstract: A reconfigurable microstrip antenna is proposed for low-cost adaptive beam-switching applications. A small patch-slot ring structure is used as the radiating element where an asymmetrical arrangement of p-i-n diodes is employed to switch the pattern in four directions. The antenna provides pattern switching of 65° and 45° in its fundamental mode for the elevation and azimuth planes, respectively. By maintaining the resonant frequency and beamwidth as relatively constant, beam switching is realized using a single feed point.

Journal ArticleDOI
TL;DR: In this paper, a planar switched beam network (SBN) is proposed for 60 GHz high data rate wireless communication, where the beamforming capability is achieved using two-dimensional (2D) scanning arrays.
Abstract: A two-dimensionally (2-D) scanning array employing a planar switched beam network (SBN) is proposed for 60-GHz high data rate wireless communication. SBNs offer a number of advantages including low cost, multibeam operation, simple direction finding, and minimal power consumption. Unlike existing switched beam arrays operating at 60 GHz, the proposed array scans in both planes. Also, in contrast to 2-D scanning stacks of Butler matrices and Rotman lenses, the proposed SBN is uniplanar and, hence, leads to low-cost manufacturing and integration with 60-GHz radios. The network produces eight 2-D beam states and demonstrates beamforming capability across the entire band of interest (57-64 GHz) with the aid of dummy crossover structures. It is printed on a Rogers Duroid 5880 substrate along with a 2 × 4 patch array. This letter describes the design, operation, and realization of the beamforming array. Simulated and measured performance results are presented to verify the design.

Journal ArticleDOI
TL;DR: In this article, the authors investigated a novel bandwidth improvement method, which combines the multilayer approach with the subwavelength element technique, and a new definition of phase error has been introduced to quantitatively analyze the performance of the reflectarray elements.
Abstract: This letter investigates a novel bandwidth improvement method, which combines the multilayer approach with the subwavelength element technique. A new definition of phase error has been introduced to quantitatively analyze the performance of the reflectarray elements. It is shown that double-layer subwavelength elements exhibit a superior phase performance across the band, namely an increased phase range and a reduced phase error over frequency. Numerical analysis is then performed to calculate the bandwidth of reflectarray antennas using these elements, where the practical fabrication tolerances at high frequencies are considered. Finally, a 1-dB gain bandwidth of 19.1% has been demonstrated for a double-layer -band reflectarray using elements with a periodicity of λ/4.

Journal ArticleDOI
TL;DR: In this paper, a polarization reconfigurable slot antenna with a novel coplanar waveguide (CPW)-to-slotline transition for wireless local area networks (WLANs) is proposed and tested.
Abstract: A polarization reconfigurable slot antenna with a novel coplanar waveguide (CPW)-to-slotline transition for wireless local area networks (WLANs) is proposed and tested. The antenna consists of a square slot, a reconfigurable CPW-to-slotline transition, and two p-i-n diodes. No extra matching structure is needed for modes transiting, which makes it much more compact than all reference designs. The -10 dB bandwidths of an antenna with an implemented bias circuit are 610 (25.4%) and 680 MHz (28.3%) for vertical and horizontal polarizations, respectively. The radiation pattern and gain of the proposed antenna are also tested, and the radiation pattern data were compared to simulation results.

Journal ArticleDOI
TL;DR: In this paper, a microstrip-fed monopole antenna with truncated ground plane is presented, where three notches with proper sizes and positions in two corners of the quasi-square radiating patch are inserted.
Abstract: -A new form of the microstrip-fed monopole antenna with truncated ground plane is presented. In comparison to the previous monopole structures, the miniaturized antenna dimension is only about 11 (0.11λr) × 16 mm2 (0.17λr), where λr, is the wavelength of the lowest frequency of the band (i.e., 3.2 GHz). By only sequentially inserting the three notches with proper sizes and positions in two corners of the quasi-square radiating patch, very good radiation and impedance characteristics are obtained. The measured impedance bandwidth of the realized antenna with optimal parameters is from 3.9 to 21.4 GHz (5.5:1, 138%) for VSWR <;1.5. Moreover, unlike the conventional omnidirectional monopole antennas, the stability of the H-plane radiation patterns of the proposed antenna is maintained in omnidirectional form within the frequency bandwidth up to 16 GHz. The improvement process of the impedance and radiation properties is completely presented and discussed.

Journal ArticleDOI
TL;DR: In this article, the effect of circular polarization diversity on the capacity of a multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system is investigated based on channel measurements.
Abstract: The effect of circular polarization diversity on the capacity of a multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system is investigated based on channel measurements. In this letter, polarization reconfigurable U-slot antennas are incorporated in a 22 MIMO-OFDM demonstrator, and the channel measurements are conducted in both line-of-sight (LOS) and non-LoS (NLOS) indoor environments. Measured results show that transmit/receive antennas radiating different polarizations are able to improve the system capacity significantly compared to antennas with the same polarization in a LOS scenario, while the extent of the improvement is reduced in a NLOS scenario. Furthermore, the factors that can affect the system capacity in both scenarios are analyzed.

Journal ArticleDOI
TL;DR: In this paper, a subwavelength element is presented for designing a circularly polarized (CP) reflectarray that converts the linearly polarized incident field of the feed into an outgoing circularly polarized field.
Abstract: A subwavelength element is presented for designing a circularly polarized (CP) reflectarray that converts the linearly polarized incident field of the feed into an outgoing circularly polarized field. To evaluate the performance of the designed element, a parametric study is carried out using Ansoft HFSS. Compared to the conventional near-resonant patch, the subwavelength one can realize a more similar behavior for the phase curves at different frequencies, leading to broader bandwidth. The phase shifts for both linear polarizations can be controlled by varying the x- and y-dimension of the element. A prime-focus reflectarray with this type of element has been designed and implemented, and a superior bandwidth performance has been verified, compared to a reflectarray with conventional ?/2 elements. The measured results show that the obtained 1-dB gain and 3-dB axial ratio bandwidths of the reflectarray with subwavelength elements can reach as large as 17% and 11%, respectively.

Journal ArticleDOI
TL;DR: In this article, a new circularly polarized patch antenna with loaded shorting elements was proposed to achieve symmetric broadside radiation and size reduction, where the loaded elements are parasitic to the driven patch, but are shorted to the ground plane.
Abstract: This letter presents a new circularly polarized patch antenna with loaded shorting elements to achieve symmetric broadside radiation and size reduction. The loaded elements are parasitic to the driven patch, but are shorted to the ground plane. Conventionally, shorting pins or walls are a common technique for reducing the size of the antenna. However, deterioration in broadside radiation with high cross-polar level occurs. The proposed shorting elements provide a solution for size reduction of the radiating patch while maintaining good broadside radiation pattern. Since the radiating patch is effectively shorted to the ground at the operating frequency, it is designated as a virtually shorted patch antenna (VSPA).

Journal ArticleDOI
Xi Chen1, Guang Fu1, Shuxi Gong1, Ya-Li Yan1, Wei Zhao1 
TL;DR: In this article, a novel circularly polarized (CP) annular-ring microstrip antenna (ARMSA) is proposed for American ultra-high frequency (UHF) radio frequency identification (RFID) readers.
Abstract: A novel circularly polarized (CP) annular-ring microstrip antenna (ARMSA) is proposed for American ultrahigh frequency (UHF) radio frequency identification (RFID) readers. The annular ring is fed by an equal-split power divider with 90° phase difference. For the compactness of the entire antenna, the divider with the shape of Archimedes gradual-change lines is designed at the inside of the annular ring. A circular parasitic patch is suspended above the ring to improve the impedance matching and bandwidth. It also enhances the performances of axial ratio (AR). The impedance bandwidth for S11 <; -10 dB and 3-dB AR bandwidth are 870-967 MHz (10.6% at 915 MHz) and 893-948 MHz (6%), respectively. The CP gain is 8.9 dBi at 915 MHz with the front-to-back ratio (F/B) of 16.5 dB. The proposed antenna is low profile as the total height is 0.043 λ0 (λ0 is the free-space wavelength).

Journal ArticleDOI
TL;DR: In this paper, a hybrid-fed circular patch antenna operating with TM11 and TM01 modes is presented, which can operate at an overlapped frequency range for 2.4-GHz WLAN applications, while TM11 mode reveals good broadside radiation patterns and TM 01 mode shows monopole-like radiation patterns.
Abstract: -In this letter, a novel hybrid-fed circular patch antenna operating with TM11 and TM01 modes is presented. By making use of a hybrid feed network, the two modes can be operated at an overlapped frequency range for 2.4-GHz WLAN applications, while TM11 mode reveals good broadside radiation patterns and TM01 mode shows monopole-like radiation patterns. The proposed antenna is fabricated and tested. The measured gain for the broadside mode is 7.1-9.1 dBi from 2.16 to 2.72 GHz (23.0%), and for the conical mode 3.4-4.3 dBi from 2.14 to 2.64 GHz (20.5%). High isolation (<; -40 dB) between the two feeding ports for the entire impedance bandwidth of the proposed antenna is achieved. The planar dual-port antenna provides different patterns and polarizations to take advantage of the pattern and polarization diversity for modern mobile communications.

Journal ArticleDOI
TL;DR: In this paper, a novel miniaturized periodic element for constructing a bandpass frequency selective surface (FSS) is proposed, which has better miniaturization performance with the dimension of a unit cell only 0.061 λ × 0.61, where λ represents the wavelength of the resonant frequency.
Abstract: In this letter, a novel miniaturized periodic element for constructing a bandpass frequency selective surface (FSS) is proposed. Compared to previous miniaturized structures, the FSS proposed has better miniaturization performance with the dimension of a unit cell only 0.061 λ × 0.061 λ , where λ represents the wavelength of the resonant frequency. Moreover, the miniaturization characteristic is stable with respect to different polarizations and incident angles of the waves illuminating. Both simulation and measurement are taken, and the results obtained demonstrate the claimed performance.

Journal ArticleDOI
TL;DR: In this paper, an enhanced planar elliptical dipole antenna design for ultrawideband (UWB) communication and impulse radar systems is presented, where elliptical slots are used on the dipole arms to enhance gain and return loss bandwidth.
Abstract: In this letter, an enhanced planar elliptical dipole antenna design for ultrawideband (UWB) communication and impulse radar systems is presented. The printed-circuit-elliptical (PCE) antenna has been investigated to be an effective radiator for UWB applications. To enhance gain and return loss bandwidth of the antenna, elliptical slots are used on the dipole arms. The gain performance of the antenna has been increased by means of elliptical slots in the frequency range from 2.7 to 11 GHz. The standing wave ratio is less than 2 (SWR < 2) along 94.4% of operation bandwidth from 1.1 to 11 GHz. The radiation pattern in E- and H-plane for certain frequencies, the return loss, and the gain performance are presented with the experimental and simulation results. Moreover, the time domain analysis of the antenna is presented. The antenna introduces low-level ringing and pulse distortion. Consequently, the antenna is very useful for impulse and UWB communication systems.

Journal ArticleDOI
TL;DR: In this paper, a dual-band antenna for radio frequency identification (RFID) reader applications covering free ISM bands of 2.37 GHz and 5.8 GHz is presented.
Abstract: A novel high-gain dual-band antenna for radio frequency identification (RFID) reader applications covering free ISM bands of 2.45 and 5.8 GHz is presented in this letter. The antenna is composed of a U-shaped copper strip with unequal arm, a printed rectangular ring, and the ground plane. A good impedance bandwidth of 120 MHz has been achieved from 2.37 to 2.49 GHz for the lower band, while the upper band covers 420 MHz (from 5.55 to 5.97 GHz). The U-shaped feeding strip excites the rectangular ring effectively by providing a good impedance matching with over 85% of total antenna efficiency in both the frequency bands and also 9.56 and 10.17 dBi gain in the lower and higher frequency band, respectively.

Journal ArticleDOI
TL;DR: In this article, a small-size dual-band implantable antenna operating in Medical Implant Communications Service (MICS) (402405 MHz) and Industrial, Scientific, and Medical (ISM) (2.48 GHz) bands was tested in vivo to investigate the effects of live tissue on the antenna performance.
Abstract: The main objective of this study is to test in vivo a small-size dual-band implantable antenna operating in Medical Implant Communications Service (MICS) (402405 MHz) and Industrial, Scientific, and Medical (ISM) (2.42.48 GHz) bands and to investigate the effects of live tissue on the antenna performance. To do so, we have designed and fabricated three identical antennas that were surgically implanted into rats at Mississippi State University's (MSU) College of Veterinary Medicine. X-ray images are also taken to ensure the proper placement of the antenna within the body. Results regarding return loss measurements and the performance change of the antenna are presented. We have also investigated possible candidate materials that can be used for encasing of the antenna for biocompatibility.

Journal ArticleDOI
TL;DR: In this paper, a loop antenna with ultrawide bandwidth is proposed to acquire high-resolution images from the inside of the human digestive tract, which is part of the outer wall of the capsule and uses a meandered line for resonance in an electrically small area.
Abstract: The capsule endoscopy system has been used to obtain an image from the inside of the human digestive tract. To acquire high-resolution images, a loop antenna with ultrawide bandwidth is proposed. It is part of the outer wall of the capsule, thus decreasing volume and increasing performance, and uses a meandered line for resonance in an electrically small area. The proposed antenna makes maximal use of the capsule's outer surface, enabling the antenna to be larger than inner antennas. The measured result shows that the gain of the proposed antenna is higher than that of inner antennas. Return loss and radiation pattern are investigated through simulation and measurement, showing that the proposed antenna has an ultrawide bandwidth of 260 MHz (from 370 to 630 MHz) for VSWR <; 2 and an omnidirectional radiation pattern. Using identical antenna pairs in the equivalent body phantom fluid, antenna efficiency is measured to 43.7% (-3.6 dB).

Journal ArticleDOI
TL;DR: In this paper, a hybrid DRA has been investigated to produce circular polarization over a wide frequency band for satellite navigation systems, and the obtained design was fabricated and measured, showing impedance matching from 1.08 to 1.82 GHz, i.e. over 50% bandwidth.
Abstract: Dielectric resonator antennas (DRAs) have been targeted in the past two decades as a potential solution for wideband antennas. Although DRAs offer wider frequency band and smaller size than patch antennas, their design to obtain good circular polarization over a wide frequency band can be challenging. In this letter, a new hybrid DRA has been investigated to produce circular polarization over a wide frequency band. The targeted application is to produce a compact antenna for satellite navigation systems. The obtained design was fabricated and measured, showing impedance matching from 1.08 to 1.82 GHz, i.e. over 50% bandwidth. The radiation characteristics of the antennas were also characterized. The achieved gain is over 1.5 dBic, and the axial ratio (AR) is under 1 dB at boresight over the 1.131.63 GHz frequency band. The half-power beamwidth is greater than 75°, and the axial ratio beamwidth (AR < 3 dB) is over 100° .