Showing papers on "Antenna array published in 2010"

Orbital Angular Momentum in Radio—A System Study

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.

Multiple antenna spectrum sensing in cognitive radios

Abstract: In this paper, we consider the problem of spectrum sensing by using multiple antenna in cognitive radios when the noise and the primary user signal are assumed as independent complex zero-mean Gaussian random signals. The optimal multiple antenna spectrum sensing detector needs to know the channel gains, noise variance, and primary user signal variance. In practice some or all of these parameters may be unknown, so we derive the generalized likelihood ratio (GLR) detectors under these circumstances. The proposed GLR detector, in which all the parameters are unknown, is a blind and invariant detector with a low computational complexity. We also analytically compute the missed detection and false alarm probabilities for the proposed GLR detectors. The simulation results provide the available traded-off in using multiple antenna techniques for spectrum sensing and illustrates the robustness of the proposed GLR detectors compared to the traditional energy detector when there is some uncertainty in the given noise variance.

Multi-antenna based spectrum sensing for cognitive radios: A GLRT approach

Abstract: In this letter, we propose multi-antenna based spectrum sensing methods for cognitive radios (CRs) using the generalized likelihood ratio test (GLRT) paradigm. The proposed methods utilize the eigenvalues of the sample covariance matrix of the received signal vector from multiple antennas, taking advantage of the fact that in practice, the primary user signals to be detected will either occupy a subspace of dimension strictly smaller than the dimension of the observation space, or have a non-white spatial spectrum. These methods do not require prior knowledge of the primary user signals, or the channels from the primary users to the CR. By making different assumptions on the availability of the white noise power value at the CR receiver, we derive two algorithms that are shown to outperform the standard energy detector.

Invasive Weed Optimization and its Features in Electromagnetics

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.

Automotive direction finding system based on received power levels

Abstract: A system is provided for locating a vehicle. The system comprises a transmission device such as a key fob for transmission and receiving of a signal. Typically the key fob has a plurality of indicators such as LED indicators arranged in a circle. The key fob is adapted to transmit a radio frequency or microwave frequency transmission signal. An antenna array is positioned on or in a vehicle. The array comprises a plurality of antennas, generally arranged in a circular pattern. The array is adapted to receive the transmission signal from the transmission device which is converted to be analyzed by a microcontroller unit (MCU). The MCU is adapted to: (i) receive digital data converted from the transmission signal, (ii) calculate an angle of arrival (AOA) or direction of arrival (DOA) based on known components and an algorithm, and (iii) transmit a selection signal back to the key fob. A signal processing unit is coupled to the plurality of antennas and the MCU. The signal processing unit is adapted to receive the signal transmission from each antenna, convert the signal to digital data, and transmit the digital data to the MCU.

Dielectric Loaded Substrate Integrated Waveguide (SIW) ${H}$ -Plane Horn Antennas

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.

Cooperative Interference Management With MISO Beamforming

Abstract: In this correspondence, we study the downlink transmission in a multi-cell system, where multiple base stations (BSs) each with multiple antennas cooperatively design their respective transmit beamforming vectors to optimize the overall system performance. For simplicity, it is assumed that all mobile stations (MSs) are equipped with a single antenna each, and there is one active MS in each cell at one time. Accordingly, the system of interests can be modeled by a multiple-input single-output (MISO) Gaussian interference channel (IC), termed as MISO-IC, with interference treated as noise. We propose a new method to characterize different rate-tuples for active MSs on the Pareto boundary of the achievable rate region for the MISO-IC, by exploring the relationship between the MISO-IC and the cognitive radio (CR) MISO channel. We show that each Pareto-boundary rate-tuple of the MISO-IC can be achieved in a decentralized manner when each of the BSs attains its own channel capacity subject to a certain set of interference-power constraints (also known as interference-temperature constraints in the CR system) at the other MS receivers. Furthermore, we show that this result leads to a new decentralized algorithm for implementing the multi-cell cooperative downlink beamforming.

Mutual Coupling Reduction in Patch Antenna Arrays Using a UC-EBG Superstrate

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.

Introduction to Direction-Of-Arrival Estimation

Abstract: Direction-of-Arrival (DOA) estimation concerns the estimation of direction finding signals in the form of electromagnetic or acoustic waves, impinging on a sensor or antenna array. DOA estimation is used for locating and tracking signal sources in both civilian and military applications. This authoritative volume provides an overview and performance analysis of the basic DOA algorithms, including comparisons between the various types. The book offers you a detailed understanding of the arrays pertinent to DOA finding, and presents a detailed illustration of the ESPRIT-based DOA algorithms complete with their performance assessments. From antennas and array receiving systems, to advanced topics on DOA estimation, this book serves as a one-stop resource for professionals and students. Nearly 100 illustrations and more than 281 equations support key topics throughout.

System and methods for antenna optimiazation for wireless broadband communication

Abstract: A system and method for antenna optimization for wireless broadband communication is provided. Such an enhanced antenna array includes higher-gain antenna and lower-gain antenna. The beamforming antenna, both higher-gain and lower-gain, are designed to be able to transmit to and receive from another transceiver. The higher-gain antenna may be designed to form a more directional beam substantially closer to the horizon; whereas the lower-gain antenna is capable of forming a less directional beam at a distance further from the horizon. In both cases, the antenna may form their respective beams anywhere in the 360 degrees horizontally around the antenna array. The higher-gain antenna may include a coverage area from the horizon to a substantially acute angle from the horizon in the vertical direction. In contrast, the lower-gain antenna may have coverage from the substantially acute angle from the horizon to substantially vertical. The substantially acute angle may be approximately 10 degrees in some cases. In some cases the lower-gain antenna may include four elements. Likewise, in some embodiments, the higher-gain antenna may include four elements as well.

Secure communication over MISO cognitive radio channels

Abstract: In this paper, we address the physical-layer security issue of a secondary user (SU) in a spectrum-sharing cognitive radio network (CRN) from an information-theoretic perspective. Specially, we consider a secure multiple-input single-output (MISO) cognitive radio channel, where a multi-antenna SU transmitter (SU-Tx) sends confidential information to a legitimate SU receiver (SU-Rx) in the presence of an eavesdropper and on the licensed band of a primary user (PU). The secrecy capacity of the channel is characterized, which is a quasiconvex optimization problem of finding the capacity-achieving transmit covariance matrix under the joint transmit power and interference power constraints. Two numerical approaches are proposed to derive the optimal transmit covariance matrix. The first approach recasts the original quasiconvex problem into a single convex semidefinite program (SDP) by exploring its inherent convexity; while the second one explores the relationship between the secure CRN and the conventional CRN and transforms the original problem into a sequence of optimization problems associated with the conventional CRN, which helps to prove that beamforming is the optimal strategy for the secure MISO CR channel. In addition, to reduce the computational complexity, three suboptimal schemes are presented, namely, scaled secret beamforming (SSB), projected secret beamforming (PSB) and projected cognitive beamforming (PCB). Lastly, computer simulation results show that the three suboptimal schemes can approach the secrecy capacity well under certain conditions.

Trellis Coded Spatial Modulation

Abstract: Trellis coded modulation (TCM) is a well known scheme that reduces power requirements without any bandwidth expansion. In TCM, only certain sequences of successive constellation points are allowed (mapping by set partitioning). The novel idea in this paper is to apply the TCM concept to the antenna constellation points of spatial modulation (SM). The aim is to enhance SM performance in correlated channel conditions. SM considers the multiple transmit antennas as additional constellation points and maps a first part of a block of information bits to the transmit antenna indices. Therefore, spatial multiplexing gains are retained and spectral efficiency is boosted. The second part of the block of information bits is mapped to a complex symbol using conventional digital modulation schemes. At any particular time instant, only one antenna is active. The receiver estimates the transmitted symbol and the active antenna index and uses the two estimates to retrieve the original block of data bits. In this paper, TCM partitions the entire set of transmit antennas into sub-sets such that the spacing between antennas within a particular sub-set is maximized. The scheme is called trellis coded spatial modulation (TCSM). Tight analytical performance bounds over correlated fading channels are proposed in this paper. In addition, the performance and complexity of TCSM is compared to the performance of SM, coded V-BLAST (vertical Bell Labs layered space-time) applying near optimum sphere decoder algorithm, and Alamouti scheme combined with TCM. Also, the performance of all schemes with turbo coded modulation is presented. It is shown that under the same spectral efficiency, TCSM exhibits significant performance enhancements in the presence of realistic channel conditions such as Rician fading and spatial correlation (SC). In addition, the complexity of the proposed scheme is shown to be 80% less than the V-BLAST complexity.

Low-Cost High Gain Planar Antenna Array for 60-GHz Band Applications

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.

Noncoherent MIMO Radar for Location and Velocity Estimation: More Antennas Means Better Performance

Abstract: This paper presents an analysis of the joint estimation of target location and velocity using a multiple-input multiple-output (MIMO) radar employing noncoherent processing for a complex Gaussian extended target. A MIMO radar with M transmit and N receive antennas is considered. To provide insight, we focus on a simplified case first, assuming orthogonal waveforms, temporally and spatially white noise-plus-clutter, and independent reflection coefficients. Under these simplifying assumptions, the maximum-likelihood (ML) estimate is analyzed, and a theorem demonstrating the asymptotic consistency, large MN , of the ML estimate is provided. Numerical investigations, given later, indicate similar behavior for some reasonable cases violating the simplifying assumptions. In these initial investigations, we study unconstrained systems, in terms of complexity and energy, where each added transmit antenna employs a fixed energy so that the total transmitted energy is allowed to increase as we increase the number of transmit antennas. Following this, we also look at constrained systems, where the total system energy and complexity are fixed. To approximate systems of fixed complexity in an abstract way, we restrict the total number of antennas employed to be fixed. Here, we show numerical examples which indicate a preference for receive antennas, similar to MIMO communications, but where systems with multiple transmit antennas yield the smallest possible mean-square error (MSE). The joint Cramer-Rao bound (CRB) is calculated and the MSE of the ML estimate is analyzed. It is shown for some specific numerical examples that the signal-to-clutter-plus-noise ratio (SCNR) threshold, indicating the SCNRs above which the MSE of the ML estimate is reasonably close to the CRB, can be lowered by increasing MN. The noncoherent MIMO radar ambiguity function (AF) is developed in two different ways and illustrated by examples. It is shown for some specific examples that the size of the product MN controls the levels of the sidelobes of the AF.

Microwave Radar-Based Differential Breast Cancer Imaging: Imaging in Homogeneous Breast Phantoms and Low Contrast Scenarios

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.

Novel Ring Resonator-Based Integrated Photonic Beamformer for Broadband Phased Array Receive Antennas—Part I: Design and Performance Analysis

Abstract: A novel optical beamformer concept is introduced that can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The core of this beamformer is an optical beamforming network (OBFN), using ring resonator-based broadband delays, and coherent optical combining. The electro-optical conversion is performed by means of single-sideband suppressed carrier modulation, employing a common laser, Mach-Zehnder modulators, and a common optical sideband filter after the OBFN. The unmodulated laser signal is then re-injected in order to perform balanced coherent optical detection, for the opto-electrical conversion. This scheme minimizes the requirements on the complexity of the OBFN, and has potential for compact realization by means of full integration on chip. The impact of the optical beamformer concept on the performance of the full receiver system is analyzed, by modeling the combination of the PAA and the beamformer as an equivalent two-port RF system. The results are illustrated by a numerical example of a PAA receiver for satellite TV reception, showing that - when properly designed - the beamformer hardly affects the sensitivity of the receiver.

Balanced metamaterial antenna device

Abstract: This document describes designs and techniques for directly feeding an unbalanced transmission line with a balanced antenna using Composite Right and Left Handed (CRLH) and balun structures.

Pattern synthesis in time-modulated linear arrays through pulse shifting

Abstract: In this study, an innovative approach for the synthesis of time-modulated linear array (TMLA) antennas is presented. The switch-on instants of the time-modulated elements are taken into account as additional degrees of freedom to optimise the array pattern. Towards this end, a technique based on a particle swarm optimisation is proposed to fully exploit the dependence of the sideband radiations (SR) on the shift of the time pulses. A set of representative results are reported to assess the effectiveness of the proposed approach as well as its flexibility.

Design of a Beam Switching/Steering Butler Matrix for Phased Array System

Abstract: A compact broadband 8-way Butler matrix integrated with tunable phase shifters is proposed to provide full beam switching/steering capability. The newly designed multilayer stripline Butler matrix exhibits an average insertion loss of 1.1 dB with amplitude variation less than ±2.2 dB and an average phase imbalance of less than 20.7° from 1.6 GHz to 2.8 GHz. The circuit size is only 160 × 100 mm2, which corresponds to an 85% size reduction compared with a comparable conventional microstrip 8-way Butler matrix. The stripline tunable phase shifter is designed based on the asymmetric reflection-type configuration, where a Chebyshev matching network is utilized to convert the port impedance from 50 ? to 25 ? so that a phase tuning range in excess of 120° can be obtained from 1.6 GHz to 2.8 GHz. To demonstrate the beam switching/steering functionality, the proposed tunable Butler matrix is applied to a 1 × 8 antenna array system. The measured radiation patterns show that the beam can be fully steered within a spatial range of 108°.

Millimeter-wave quasi-optical integrated dielectric lens antenna and array thereof

Abstract: The invention relates to the technical field of radar, in particular to a millimeter-wave quasi-optical integrated dielectric lens antenna and an array thereof. The array consists of a microstrip integrated antenna, a dielectric lens, an objective lens, an array base, a reflecting mirror, a protective cover and a beam transfer switch; one end face of the dielectric lens is a hemisphere or an ellipsoid, while the other end face is a cylindrical section; the microstrip integrated antenna is generated by an dielectric substrate, the front surface of the dielectric substrate is closely adhered tothe cylindrical section of the dielectric lens and serves as a feed source, and the back surface is grounded; the hemispherical or ellipsoidal end face of the dielectric lens is an antenna radiating surface; the length of the cylindrical part of the dielectric lens can be changed; the antenna array is arranged into a linear array or an area array; the array base and the reflecting mirror have conical quasi-optical reflecting mirror surfaces; the focus of the objective lens of the linear array or the area array aligns with the central line of the dielectric lens; the protective cover is arranged outside; and the antenna array is controlled by the beam transfer switch. The antenna structure has strong shock resistance and dust prevention, and is suitable for millimeter-wave radars for planes, automobiles and ships, and receiving/emitting sensing of communication equipment.

Novel Ring Resonator-Based Integrated Photonic Beamformer for Broadband Phased Array Receive Antennas—Part II: Experimental Prototype

Abstract: An experimental prototype is presented that illustrates the implementation aspects and feasibility of the novel ring resonator-based optical beamformer concept that has been developed and analyzed in Part I of this paper . This concept can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The design, fabrication, and characterization of a dedicated chip are described, in which an 8 × 1 optical beamforming network, an optical sideband filter for single-sideband suppressed carrier modulation, and a carrier re-insertion coupler for balanced optical detection are integrated. The chip was designed for satellite television reception using a broadband PAA, and was realized in a low-loss, CMOS-compatible optical waveguide technology. Tuning is performed thermo-optically, with a switching time of 1 ms. Group delay response and power response measurements show the correct operation of the OBFN and OSBF, respectively. Measurements on a complete beamformer prototype (including the electro-optical and opto-electrical conversions) demonstrate an optical sideband suppression of 25 dB, RF-to-RF delay generation up to 0.63 ns with a phase accuracy better than ?/10 radians, and coherent combining of four RF input signals, all in a frequency range of 1-2 GHz.

Automatic positioning of diversity antenna array

Abstract: Embodiments of the invention provide an antenna system for connecting to a wireless device through a communication link. The antenna system comprising an antenna array configured to pre-scan frequency bands of radio signals in a plurality of antenna array directions, a transceiver connected to the antenna array. The transceiver is configured to analyze the signals received from the antenna array to obtain one or more parameters from one or more MIMO channels of the antenna array, and transmit the one or more parameters to the antenna controller. Further, the antenna system comprises a platform connected to the antenna array, wherein the platform is configured to position the antenna array, and a motor controller connected to the platform. The motor controller is configured to receive one or more position signals from the device, wherein the position signals correspond to a pre-scanned performance level of the communication link based on the parameters, and control the position of the antenna array by rotating the platform based on the position signals.

Direction of Arrival Estimation in Time Modulated Linear Arrays With Unidirectional Phase Center Motion

Abstract: A novel approach for estimating the direction of arrivals (DOAs) in time modulated linear arrays (TMLAs) with unidirectional phase center motion (UPCM) scheme is proposed in this paper. Based on the fact that the main beams of the patterns at different sidebands can be directed at different directions, the corresponding received signals can be used to compose a received data space. Thus, the spatial locations of the far-field sources can be estimated by using multiple signal classification (MUSIC) algorithm. Simulation results of the DOA estimation in an 8-element TMLA with the UPCM scheme validate the proposed approach, where the performance such as the accuracy and resolution of the DOA estimation is obtained through Monte-Carlo simulations. As compared to the DOA estimation based on conventional uniform linear arrays (ULAs), a much better resolution performance is obtained.

Beamsteering in Pattern Reconfigurable Arrays Using Directional Modulation

Abstract: An array with pattern-reconfigurable elements is used to generate a digital modulation by switching the elements for every symbol. This technique is known as directional modulation. Because the modulation is generated at the antenna level, it gives control over the directions in which data is sent, unlike baseband modulation which transmits the same data in all directions at different power levels. A procedure for determining how to switch the elements to transmit only in a specified direction is outlined. Results indicate that compared to a traditional reconfigurable array, the directional modulation array allows information to be sent over a narrower beamwidth. Additionally, the method provides more selectivity in the possible transmit angles. Measured and calculated results from a four-element reconfigurable array are presented.

Reducing the Number of Elements in the Synthesis of Shaped-Beam Patterns by the Forward-Backward Matrix Pencil Method

Abstract: The matrix pencil method (MPM) has been used to reduce the number of elements in the linear antenna array with a pencil-beam pattern. This work extends the MPM-based synthesis method to the synthesis of shaped-beam patterns by using the forward-backward matrix pencil method (FBMPM). The FBMPM-based synthesis method places a necessary restriction on the poles which correspond to element positions, and consequently obtains more accurate synthesis results, particularly for the synthesis of asymmetric patterns. Numerical examples show the effectiveness and advantages of the proposed method in the reduction of the number of elements for shaped-beam patterns.

On the accuracy of localization systems using wideband antenna arrays

Abstract: Accurate positional information is essential for many applications in wireless networks. Time-of-arrival (TOA) and angle-of-arrival (AOA) are the two most commonly used signal metrics for localizing nodes with unknown positions. In this paper, we consider a wireless network in which each node is equipped with a wideband antenna array capable of performing both TOA and AOA measurements. Since both the position and orientation of the agent are of interest, we propose a localization framework that jointly estimates these two parameters. The notion of equivalent fisher information is applied to derive the squared error bounds for the position and orientation. Since our analysis starts from the received waveforms rather than directly from the signal metrics, these bounds characterize the fundamental limits of the position and orientation accuracy. Surprisingly, our result reveals that AOA measurements obtained by wideband antenna arrays do not further improve position accuracy beyond that provided by TOA measurements.

Continuous aperture phased MIMO: Basic theory and applications

Abstract: Given the proliferation of wireless communication devices, the need for increased power and bandwidth efficiency in emerging technologies is getting ever more pronounced. Two technological trends offer new opportunities for addressing these challenges: mm-wave systems (60–100GHz) that afford large bandwidths, and multi-antenna (MIMO) transceivers that exploit the spatial dimension. In particular, there has been significant recent interest in mm-wave communication systems for high-rate (1–100 Gb/s) communication over line-of-sight (LoS) channels. Two competing designs dominate the state-of-the-art: i) traditional systems that employ continuous aperture “dish” antennas and offer high power efficiency but no spatial multiplexing gain, and ii) MIMO systems that use discrete antenna arrays for a higher multiplexing gain but suffer from power efficiency. In this paper, we propose a new communication architecture - continuous aperture phased MIMO - that combines the advantages of both designs and promises very significant capacity gains, and commensurate gains in power and bandwidth efficiency, compared to the state-of-the-art. CAP-MIMO is based on a hybrid analog-digital transceiver architecture that employs a novel antenna array structure - a high-resolution discrete lens array - to enable a continuous aperture phased-MIMO operation. We present the basic theory behind CAP-MIMO and the potential capacity/power gains afforded by it. We also highlight potential applications of CAP-MIMO in mm-wave communications.

Modular type cellular antenna assembly

Abstract: A individually formed radiating unit, an antenna array, and an antenna assembly are provided. The individually formed radiating unit includes a reflector, at least one radiating element integrated into a first side of the reflector, and a housing disposed on a second side of the reflector. The housing forms a chamber for housing a feed network.

UWB Circular Slot Antenna Provided with an Inverted-L Notch Filter for the 5 GHz WLAN Band

Abstract: —The study of a planar circular slot antenna for Ultrawideband (UWB) communications is presented. The integration on this antenna of a notch filter, to reduce the possible interferences with the 5GHz WLAN communications, has been discussed in detail. Four different structures, achieved by etching a suitable pattern on the antenna circular stub, have been considered, and their features have been compared. The antenna with symmetrical and inverted-L cuts shows the best performance, and it has been therefore realized and fully characterized. It shows very good matching features over the UWB band, and notable rejection of the 5 GHz WLAN band.