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Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE

Date 11-17 July 2010

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Displaying Results 1 - 25 of 1130
  • 3D integration of a band selective filter and antenna for 60 GHz applications

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB) |  | HTML iconHTML  

    The growing demand for higher data bit transfer has made the 60GHz band a prominent research area for the wireless community. In the United States, the Federal Communication Commission (FCC) has allocated the band of 57-64 GHz for the general public while the 57-66 GHz band covers the unlicensed band worldwide. The high frequency band promises over 1 Gb/s data rate over a short distance and enables highly compact and miniaturized systems. However, the design becomes more sensitive to errors from fabrication tolerances that can degrade the system performance drastically. In an effort to reduce these negative effects, a System-on-Package (SOP) approach is presented to integrate a band selective cavity filter and a vertical dipole antenna. The near 9 GHz spectrum of 57.24-65.88 GHz, which covers all the unlicensed 60 GHz bands worldwide, is divided into four bands of 2.16 GHz. The band selective filter has three states out of the four bands while the dipole antenna covers the entire band. The resulting system gives a gain of 3.6 dBi, 4.2 dBi, and 4.1 dBi at frequency points of 57.7 GHz, 61.2 GHz, and 64.1 GHz, which are the center frequency of each band. View full abstract»

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  • Dynamic real time tuning of antenna matching circuit in the receiving mode

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    We present a novel approach for adaptive tuning of receiving antenna impedance matching operating in a time-varying environment. Our approach utilizes perturbations of the tuning circuit to construct a system of two nonlinear equations. This system is then solved to determine the exact input impedance of the antenna. With this, the tuning circuit is then adjusted to match the antenna at the calculated input impedance. This cycle is repeated with a certain rate to take into account the dynamic surrounding environment in real time. View full abstract»

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  • Degrees of freedom of the field in unconditionally secure wireless communications

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    The aim of this conference paper is to identify the maximum number of useful spatial channels in artificial-noise based unconditional communication systems using the concept of the degrees of freedom of the field. The approach followed in this paper was firstly proposed in an ASSIST COST meeting and is strictly related to the MIMO communication system analysis carried out. View full abstract»

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  • Encryption key establishment using space-time correlated MIMO channels

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (149 KB) |  | HTML iconHTML  

    This paper investigates the establishment of secret encryption keys from temporally and spatially correlated MIMO channel matrices. The discussion first examines the influence of correlation on the secret key rate with the help of a simple SISO channel model that generates samples with correlation behavior that can be described in closed-form. This analysis reveals that an optimal sampling approach can be devised that minimizes the total time required to achieve a key with a specified length. The presentation also examines the decorrelation of measured channel samples, and demonstrates that independently removing spatial and temporal correlations fails to produce random variables that are truly decorrelated. Finally, attention turns to a method for quantizing the uncorrelated channel samples. Simulations using real channel measurements reconfirm the observations made using the simple channel model and demonstrate that while existing algorithms for channel quantization can be effective, their performance falls short of that predicted by the upper bound. View full abstract»

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  • Measured statistics of reciprocal channel key generation of indoor MIMO channels

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    There is growing interest in physical-layer security methods that exploit the random nature of the physical propagation channel to strengthen existing crypto-systems. In reciprocal channel key generation (RCKG), legitimate nodes (Alice and Bob) observe a common fluctuating channel to generate keys that are safe from the eavesdropper (Eve). Previous work derived expressions for the available key bits and those safe from an eavesdropper for MIMO systems with correlated complex Gaussian statistics. This paper applies these expressions to new MIMO measurements in indoor LOS and NLOS environments, indicating how propagation effects limit secure key generation and what key generation rates can be expected in practice. View full abstract»

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  • Securing wireless links at the physical layer through reconfigurable antennas

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    The purpose of this paper is to demonstrate how the capabilities of reconfigurable antennas can be used to enhance physical layer-based security algorithms for wireless systems. View full abstract»

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  • SINR improvement through reconfigurable antenna adaptation to handheld device orientation

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    The potential for signal to interference noise (SINR) improvement by using beamforming at a mobile station (MS) is well known. For example, the use of smart antennas in a mobile station is considered, and is shown that SINR improvements can be up to 40 dB for peer to peer communications and approximately 25 dB for microcell applications. In Knudsen and Pedersen considered the impact of the human head on the directionality of MS transmissions in a non-reconflgurable antenna. Despite the significant body of published work on smart antennas, there has been no published treatment we are aware of that specifically measures the motions typically experienced by handheld MSs such as cellular phones and smart phones and analyzes the SINR gains that can be achieved if these motions are measured in real time and used in setting the antenna configuration. The motivations for this work are strong. The gains that can be achieved by antenna adaptation are significant, and one can expect that even imperfect and/or delayed MS orientation information can, if provided to a smart antenna, lead to significantly improved SINR and therefore significantly improved link and service quality. Such adaptation is becoming more feasible in light of recent developments in reconfigurable antennas. View full abstract»

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  • Miniature radiation pattern reconfigurable antenna for 2.4 GHz band

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB) |  | HTML iconHTML  

    Reconfigurable antennas offer the possibility of changing characteristics over time to maintain a high quality wireless communications link as the propagation environment changes. Radiation pattern reconfigurable antennas are of particular interest because manipulation of the radiation pattern enables avoidance of noise source, improved security by directing signals only toward intended users, avoidance of signal fades, improved beam steering capability of phased array systems, and increased diversity gain [1]. Various designs have been proposed [2] to achieve radiation pattern and frequency reconfiguration. A key design issue for pattern reconfigurable antennas is that antenna dimensions must be electrically small for many wireless applications. Many types of reconfigurable antennas have been demonstrated, but significant pattern change can require electrically large antenna structures. The goal of this work is to achieve pattern reconfigurability with a compact, electrically small, low cost planar antenna design. We report on a reconfigurable antenna design that achieves these performance criteria for the ISM band. The antenna was simultaneously optimized for small size, low return loss, and high pattern reconfigurability. View full abstract»

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  • Small pixelled antenna with MEMS-Reconfigurable radiation pattern

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (269 KB) |  | HTML iconHTML  

    A MEMS reconfigurable antenna capable of steer the main beam over a wide range of angles has been designed. The use of a novel multi-size pixelled geometry combined with the parasitic elements modification technique has lead to a structure with a low number of MEMS-switches. It has been achieved a small size antenna (λ/2 x λ/2) which can make possible its integration in mobile terminals allowing robust communications. View full abstract»

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  • A simple approach to reducing mutual coupling in two closely-spaced electrically small antennas

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    A simple technique has been proposed to reduce the mutual coupling between two MTM-inspired electrically small antennas that are closely-spaced. This technique relies on the self-cancelation of the induced common-ground and near-field currents and does not require any additional structures, which in turn simplifies the design process and reduces the fabrication cost. We have shown that for two small antennas sized λ0/14.4 x λ0/21.4 and spaced edge-to-edge λ0/30.6 or center-to-center λ0/13.6, the mutual coupling of |S21| is reduced from -8.3 dB to -16.6 dB . View full abstract»

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  • A novel metamaterial CRLH ZOR microstrip patch antenna capacitively coupled to a rectangular ring

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (534 KB) |  | HTML iconHTML  

    In this paper, a novel rectangular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Complosite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a standard microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding rectangular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas. View full abstract»

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  • Electrically small tunable split ring resonator antenna

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB) |  | HTML iconHTML  

    A tunable SRR antenna is investigated both theoretically and experimentally. The proposed antenna has a variable radiation frequency from 1.81 GHz to 2.14 GHz with a tuning voltage between 0 and 9.5V. Simulated data show good agreement with measurement ones. Besides tuability, the proposed antenna has achieved a dimension reduction by 59.3 % compared with the monopole counterpart. View full abstract»

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  • Metamaterial inspired patch antenna miniaturization technique

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB) |  | HTML iconHTML  

    A new methodology is introduced to design miniaturized patch antennas based on an in situ GA optimization of a single horizontal complementary resonant structure. Simulation results show that the resonant frequency can be shifted from 5 GHz to 500 MHz providing a size reduction of 90%. At each frequency, the target reflection coefficient, which was set to -15 dB, was obtained within 10 iterations of the GA. These results are not necessarily optimal, and a reduction greater than 90% might be achieved by optimizing on efficiency as well as reflection coefficient. Further analysis using a multi-objective fitness function should provide significant improvement. View full abstract»

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  • Leaky-wave antennas with anisotropic metamaterials

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB) |  | HTML iconHTML  

    Leaky wave antennas can offer high directivity and frequency scanning [I]. An isotropic dielectric slab with refractive index n > 1 does not radiate effectively unless spatial variations are introduced to excite fast-wave space harmonics [I]. To realize uniform leaky wave structures, potentially in the optical domain, a metamaterial slab with n >C 1 has been proposed to achieve a narrow radiation beam [2, 3]. This approach suffers the limitation of large transverse slab dimensions, because the operating wavelength inside the slab is much greater than the free space wavelength, due to the small value of n [4]. Low refractive index metamaterials that require small material permeabilities face challenges of implementation [3]. In addition, radiation occurs in a narrow angular range between broadside and the critical angle sin(n), which limits beam scanning. Finally, we note that while a microstrip transmission line loaded with series capacitors and shunt inductors has been studied to realize metamaterial leaky-wave antennas in the microwave frequency regime [5], identifying the optical counterparts is difficult. To overcome these limitations, we present a forward/backward radiating leaky waveguide at optical wavelengths based on nonmagnetic uniaxially anisotropic metamaterials having permittivity tensors in which one component is different from the others in sign [6]. The resulting hyperbolic dispersion relation enables radiation from backfire (-90°) to endfire (90°), and the slab thickness can be small relative to the free space wavelength. View full abstract»

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  • Miniature dual-band and wideband antennas based on printed circuit emulation of anisotropy

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (370 KB) |  | HTML iconHTML  

    Several dual-band and wideband miniature antennas were introduced by harnessing the controllable dispersion properties of layered anisotropic media. A key aspect of the design is the emulation of anisotropy using printed coupled lines with lumped loads. Exciting the resonances of two closely spaced K-ω branches resulted in a miniature coupled double loop (CDL) antenna having λo/9.8 x λo/9.8 x λ<;/39.4 footprint and 2.65% bandwidth. As such, the CDL antenna exhibits 49% smaller footprint and 8% larger bandwidth than a standard patch antenna. We demonstrated that miniature CDL antennas can achieve much wider bandwidths (14.7%) when printed on thicker (λο/lθ.l) substrates. Also, a λο/θ x λo/9 miniature dual-band CDL antenna was presented for LI and L2 band GPS applications. Implementations and measurements of various designs are underway and will be presented at the conference. View full abstract»

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  • Experimental exploration of metamaterial substrate design for an electrically small patch-like antenna

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (377 KB) |  | HTML iconHTML  

    This paper discussed the design of rectangular spirals used to create an electrically small patch antenna with a μ-negative core (MNG) substrate and showed that varying the number of spirals placed on the individual boards provides added design freedom beyond selecting the number of turns. For an electrically small antenna with a fixed size, resonant frequencies were achieved from 220 MHz to 675 MHz by changing the parameters of the spirals that create the MNG substrate. Single spirals allow lower resonant frequencies than multiple spirals encompassing the same area with the same number of turns. This enables smaller antennas for a given wavelength. View full abstract»

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  • Radiation efficiency improvement of low profile antenna with metamaterial structure using LCP substrate with low profile copper foil

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (674 KB) |  | HTML iconHTML  

    EBG (Electromagnetic BandGap) structures have lately attracted considerable attention both for the surface wave suppression and low profile antennas. To achieve low profile antennas by using an EBG structure for the antenna substrate, the thinner EBG substrate as well as the smaller gap to the antenna above the EBG substrate is important. Furthermore, a smaller EBG substrate area is required to accommodate the antenna into small wireless equipments. We have proposed a small metamaterial structure by analogy with a mushroom-like EBG structure, which enables a dipole antenna just above the structure to match with 50Ω as well as EBG structures. View full abstract»

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  • A high gain circular polarization antenna using metamaterial slabs

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB) |  | HTML iconHTML  

    In this paper, we propose an advanced high gain circular polarization antenna consisting of metamaterial slabs. The high gain property is achieved by using metamaterial slabs with periodic circular lattices while circular polarization is obtained by inserting fan-shaped patches in the circular lattices. In addition, the right/left handed polarization is easily controlled by rotating metamaterial slabs. Details of the design, fabrication, test, and performance of the proposed antenna are presented. View full abstract»

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  • A 5.8 GHz high gain, aperture coupled rectenna utilizing a split ring resonator filter

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB) |  | HTML iconHTML  

    A high gain, aperture coupled rectifying antenna for 5.8 GHz operation is presented which has a measured gain of 9.3 dBi and an RF-to-DC conversion efficiency of 73%. Split ring resonators (SRRs) are utilized to suppress diode harmonics. View full abstract»

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  • Passive feed methods for meshed antennas

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (182 KB) |  | HTML iconHTML  

    Previous studies have concentrated on rectangular meshed patches. However, circular and triangular shapes can improve polarization and bandwidth characteristics not addressed in rectangular patches. One of the challenges with these shapes is effective feed design and an efficient fabrication method. To solve these two problems, we have examined several types of antenna feeds using inkjet printing with conductive ink on plastic substrate or copper tape on glass. Furthermore, it was found that printing methods are effective in fabricating meshed antennas and that passive feed methods can be easily and efficiently implemented for single patch or antenna array designs. View full abstract»

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  • A general representation of electromagnetic fields radiated by circular patch antennas

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    In this paper, the field distribution in the upper half space is divided into two regions: the fields in the upper hemisphere with r <;ae and the fields in the exterior region r > ae, where ae is a scale dependent on the geometry of the patch and the permittivity of the substrate. By employing dyadic Green's functions expanded in these two regions, an exact solution is obtained to both near and far fields of circular patch antennas. View full abstract»

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  • High power waveguide-fed reduced lateral wave antenna

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (242 KB) |  | HTML iconHTML  

    This research focuses on the development of a high-power waveguide-fed microwave antenna that has a reduced level of lateral radiation (radiation that travels along the supporting ground plane, potentially causing serious coupling, interference, and diffraction problems). A particular design is proposed, and simulations of this design verify the reduced lateral radiation behavior of the antenna. View full abstract»

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  • A new look into the cross-polarized radiation form a circular microstrip antenna and suppression using dot-shaped DGS

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1530 KB) |  | HTML iconHTML  

    The cross polarized (XP) radiation from a probe-fed circular patch, its variation with the change in probe location from the matched to slightly offset configuration, and the application of a pair of dot-DGS to suppress that the XP levels are investigated. Some significant results are provided based on a series of simulation and experimental studies. View full abstract»

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  • Front-to-back ratio improvement of a microstrip patch antenna by ground plane edge shaping

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (299 KB) |  | HTML iconHTML  

    In a microstrip patch antenna design on the finite size of ground plane, it shows significant performance degradation by surface waves. It is well known that the smaller ground plane size, the gain is decreased and the back lobe is increased. As the size of the ground plane is reduced, currents distribution of the ground plane edge is increased. These currents results in diffraction of both leaky and surface waves and the front-to-back ratio of a patch antenna is decreased due to the increased backward wave level. In this paper, ground plane edge shaping method is used to reduce these edge currents effect. By cutting out the edges of the ground plane of the patch antenna and forming the meandering edges, the front-to-back ratio of a patch antenna significantly improved. View full abstract»

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  • Finite-width conductor-backed coplanar waveguide-fed circularly polarized side-plane antenna

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (425 KB) |  | HTML iconHTML  

    The coplanar waveguide with a lower ground plane forms the conductor-backed coplanar waveguide (CBCPW). Due to the lower ground plane, the mechanical strength and heat-sinking capability of the conventional coplanar waveguide are improved. In practice, the substrate and the ground planes of the CBCPW are usually of finite width. The CBCPW mode and the microstrip-like mode coexist in the finite-width CBCPW. Both of them have zero cutoff frequency. The phase velocity of the microstrip-like mode (MSL) is slower than the CBCPW mode. Therefore, the MSL mode takes power away all the time. The leaky MSL mode causes the resonances of the side-plane conductors. The transmitted power is reduced by the reflected and radiated power when the side-plane conductors resonate. The unwanted radiation maybe degrades the performance of the finite-width CBCPW-fed antenna unless through-plated vias are placed at the inner edges of the side-plane conductors. Using through-plated vias increases the manufacturing cost. With proper design, the side-plane conductors fed by finite-width CBCPW can form a simple, vialess, unidirectional, and linearly polarized antenna. In this paper, a compact finite-width CBCPW-fed circularly polarized (CP) side-plane antenna is proposed. View full abstract»

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