Ultra-wideband Antenna Array Research Articles

Compact, Dual-Polarized UWB-Antenna, Embedded in a Dielectric

A compact dual-polarized antenna is described for ultrawideband (UWB) applications. The main features of the antenna, besides an ultrawidebandwidth are low cross-polarization and small dimensions. The feed of the antenna is based on the tapered slot antennas, enclosed in a dielectric. The new antenna concept, including the feed of the antenna for dual-polarization and its integration, is described in detail. Prototypes are shown and their performances are demonstrated, based on simulation and measurement results in frequency and time domain. The antenna prototype input match is better than -10 dB, a maximal gain of 10.5 dBi and a mean polarization decoupling of approximately 17 dB in the main beam direction in the 3.1-10.6 GHz UWB band are achieved. In the time domain a peak value of 0.4 m/ns, a full width at half maximum of 100 ps and a ringing of 145 ps are measured. With a maximum antenna diameter of 35 mm and 53 mm length this new antenna is also suited for UWB antenna arrays.

A Transient UWB Antenna Array Used with Complex Impedance Surfaces

The conception of a novel Ultra-Wideband (UWB) antenna array, designed especially for transient radar applications through the frequency band (300 MHz–3 GHz), is proposed in this paper. For these applications, the elementary antenna must be compact and nondispersive, and the array must be able to steer in two dimensions. The geometry of the elementary antenna and its radiation characteristics are presented. The array beam steering is analyzed and a technique making the increase of the transient front-to-back ratio possible is described.

Time-Domain Design of UWB Vivaldi Antenna Array Using Multiobjective Particle Swarm Optimization

A method to obtain optimum tradeoffs (Pareto front) between sidelobe level (SLL) and beamwidth (BW) in time domain for ultrawideband (UWB) antenna arrays is presented. Multiobjective particle swarm optimization (MOPSO) is used to deal with these two conflicting objectives. In the optimization process, mutual coupling effects between elements are not considered. However, the multiple solutions obtained from MOPSO enable the designer to consider the mutual coupling effect as an additional constraint. Each element of the array is an antipodal Vivaldi antenna. The optimization template is applied for three different time-domain pattern descriptors. In comparison to arrays with the same number of elements reported in literature, the Pareto fronts obtained in this study provide lower BW and SLL. A four-element sample from resultant Pareto fronts was simulated by using CST Microwave Studio software. This array shows a 13.7-17.2 dBi gain over the whole frequency band from 3-11 GHz, 7.2° BW, and -12 dB SLL for energy pattern.

Beam steerable IR-UWB antenna array with FCC-compliant impulse generators

A novel method for beam steering with an active ultra-wideband antenna array is presented for impulse-radio ultra-wideband. The antenna array consists of four planar Vivaldi antennas in a collinear arrangement with an impulse generator circuit mounted chip-on-board on each antenna element. The beam steering is done by shifting the phase of the control signals triggering the impulse generators. In the array arrangement a measured beamwidth of 16° is achieved for an antenna spacing of 4 cm compared to 80° for a single Vivaldi antenna. Beam steering is experimentally demonstrated for a steering angle of 30°.

Interleaved Ultrawideband Antenna Arrays Based on Optimized Polyfractal Tree Structures

There is considerable interest in interleaving multiple phased array antennas into a single common aperture system. Current phased array antenna technology is limited to narrowband operation, leading to the appearance of grating lobes and strong mutual coupling effects when they are incorporated into the design of a common aperture system. To overcome this obstacle, a new class of arrays, called polyfractal arrays, has been introduced that possess natural wideband properties well suited for large-scale genetic algorithm optimizations. These arrays also possess recursive beamforming properties and an autopolyploidy-based chromosome expansion that can dramatically accelerate the convergence of a genetic algorithm. In addition, a robust Pareto optimization can be applied to reduce the peak sidelobe levels at several frequencies throughout the intended operating band, leading to ultrawideband antenna array designs. Because of their lack of grating lobes, these polyfractal arrays are ideal building blocks for interleaved antenna array systems. This paper develops these concepts, first creating ultrawideband array designs based on polyfractal geometries and then interleaving these designs into a common aperture system. Several examples of interleaved systems are discussed, with one two-array system possessing a peak sidelobe level of nearly -18 dB with no grating lobes over a 20:1 bandwidth with either of the component array mainbeams steered independently up to 60° from broadside.

Broadband array antenna with Marchand balun for 5.8 GHz band notched UWB application

AbstractA two‐element ultra wideband array antenna with a 5.8 GHz band‐notch function is proposed. A novel Marchand balun feeding structure is chosen for its great merit of the equi‐amplitude and 180° phase difference signals, making the omni‐directional of radiation pattern much better. A simple u‐shape slot is inserted into the radiating patch to create a frequency band‐stop characteristic. The measured VSWR less than 2 is from 3.1 to 10.6 GHz, and the frequency notch band is from 5.7 to 5.9 GHz. The measured results agree well with the simulated. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1537–1539, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24384

A Novel UWB Array with Band-Notched Characteristics

As wireless communication applications require more and more bandwidth, the demand for wideband antennas increases as well. For instance, the ultra wideband radio (UWB) utilizes the frequency band of 3.1–10.6 GHz. In this paper, a novel ultra-wideband (UWB) antenna array based on eight double-side printed hexagon-shaped dipoles for UWB applications is presented. The proposed antenna array has an impedance bandwidth of 1–12 GHz (return loss less than –10 dB), with one notched frequency at 3.1–3.95 GHz for S11 > –10 dB. The variety of notched frequency bands affected by the antenna parameters has also been discussed. With the use of a circular ground plane, the presented antenna has bidirectional radiation characteristics. The measured peak gain of the proposed antenna is 10.2–17.5 dBi over the operating frequency range.

AN ULTRA WIDEBAND IMPULSE OPTOELECTRONIC RADAR: RUGBI

An ultra wideband radar system based on a coherent emission of an ultra-wideband antenna array using photoconductive switching devices is proposed. The triggering process is obtained by the excitation of semiconductor samples in linear mode using a picosecond laser source. The emitting antenna system and the receiving antenna developed by the Research Institute XLIM present some specific qualities suitable for radiation and measurement of ultrashort pulses. The optical control of the sources allows to sum the

Combining magnetic resonance imaging and ultrawideband radar: A new concept for multimodal biomedical imaging

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and UWB radar. Furthermore, first in vivo experiments have been carried out, utilizing this new approach. Correlating the reconstructed UWB signals with physiological signatures acquired by simultaneous MR measurements, representing respiratory and myocardial displacements, gave encouraging results which can be improved by optimization of the MR data acquisition technique or the use of UWB antenna arrays to localize the motion in a focused area.

Laser distribution by optical fiber bundle in the ultrawideband antenna array

In a photoconductive semiconductor switch (PCSS) ultrawideband (UWB) array system, optical fiber bundles with several hundreds or more fibers are employed to distribute laser beam energy and yield multiple laser beams with the same energy and coherence. Ideally, if each fiber of the bundle is the same length, the laser beams transmit in the fiber and may arrive to the PCSS simultaneously in the UWB array system. In this work, the coupling rate of the fiber bundle is estimated. The experimental result of dividing laser energy shows that multiple lasers can be obtained by using a fiber bundle. Specifically, the experiments on the 17-PCSS antenna array radiation indicate that the pulses generated by PCSS give up only several picoseconds of time jitters, thus demonstrating that laser distribution by fiber bundle can be used for UWB coherent combination.

Planar 4‐element UWB antenna array and time domain characterization

AbstractIn this article, a novel planar ultra‐wideband (UWB) antenna array based on four identical UWB antenna elements for UWB applications is presented. The proposed antenna array yields an impedance bandwidth of 3.1–10.6 GHz with VSWR <2. Over the entire bandwidths, it has constant high gain, which is about 6.5–10.5 dBi, and a 60° 3‐dB beamwidth is obtained within the operational band. A planar 2‐element UWB antenna array and a band‐notched 4‐element UWB antenna array are also provided for references. Time domain descriptors of the proposed antenna array have been used to estimate short‐range UWB signal transmission, propagation, and reception. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3118–3123, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23874

A Broadband and High Isolation CPW Fed Microstrip Antenna Array

A new form of ultra wideband and high isolation microstrip antenna array with an optimum CPW feed is presented. The Finite Element Method (FEM) is employed for the analysis over the antenna frequency band, 1.68–4.85 GHz, (111%). Mutual coupling between entire elements of the antenna array is investigated and very high isolation (better than – 40 dB) is obtained over the entire antenna bandwidth. Antenna surface current distribution is simulated with HFSS and mutual coupling of the elements as well as E- and H-plane patterns are presented.

A RBFNN approach for DoA estimation of ultra wideband antenna array

The problem of direction of arrival (DoA) estimation of ultra wideband (UWB) electromagnetic (EM) waves is addressed and a radial-basis-function neural network (RBFNN) base approach is presented in this paper, in which the DoA estimation is achieved as a mapping which can be modeled using RBFNN trained with input–output pairs. Because RBFNN is characteristic of accurate approximation and good generalization, as well as robustness against interference and scattering from antennas, the proposed method can learn source direction findings of UWB array and work well in existence of manufacturing errors and mutual coupling of UWB array antennas. In order to get rapid training and avoid large network size, a hybrid leaning scheme for RBFNN is adopted. Firstly an unsupervised K-means clustering algorithm is employed to determine the centers of hidden neurons, then a recursive least square (RLS) algorithm is used to obtain the linear weights of the output layer. Moreover, in order to solve the multiple sources tracking of UWB array, we combine eigenvalue decomposition (EVD) with RBFNN to extract the DoAs of multiple sources. The effectiveness of our scheme is demonstrated through several numerical examples. The results show that this method is characteristic of high accuracy and robustness to mutual coupling, when compared to presently available methods in literatures.

UWB Array-Based Sensor for Near-Field Imaging

In this paper, the development of an ultra-wideband (UWB) array-based time-domain radar sensor for near-field imaging is described. The radar sensor is designed to be used within a vehicle-mounted multisensor system for humanitarian demining. The main novelty of the radar lies in the system design with a single transmitter and multichannel receiver. Design of the UWB antenna array is also novel. The radar produces 3D images of subsurface by 1D mechanical scanning. The imaging capability of the radar is realized via electronic steering of the receive antenna footprint in a cross-scan direction and synthetic aperture processing in an along-scan direction. Imaging via footprint steering allows for a drastic increase in the scanning speed.

Spatial correlation technique for UWB antenna arrays

A computation technique for predicting the spatial correlation coefficients, based on data captured by an ultra-wideband antenna array, is presented. Signal correlation coefficients obtained from adjacent array positions were calculated at each time bin. In addition, the application of this technique can lead to ultra-wideband multipath cluster identification. Time bins associated with high correlation values were selected as cluster arrival times and were compared with results estimated by the Sensor-CLEAN algorithm.

Optimization of waveforms for UWB circular and disk antenna arrays

The basic pulse waveform is an important factor that affects the angular resolution of UltraWideBand (UWB) antenna array. The optimization of these basic pulse waveform for circular and disk array is considered; the optimization problem can be simplified and translated into a simple form, which can be solved effectively. Several optimized waveforms are given, and the main lobes of energy pattern of these optimized waveforms are much narrower than those of corresponding Gaussian waveforms. Numerical results show that optimized waveforms achieve considerable improvement in angular resolution.

Microwave Imaging via Space–Time Beamforming: Experimental Investigation of Tumor Detection in Multilayer Breast Phantoms

Microwave imaging via space-time (MIST) beamforming has been proposed recently for detecting small malignant breast tumors. In this paper, we extend the previously presented two-dimensional space-time beamformer design to three-dimensional (3-D), and demonstrate its efficacy using experimental data obtained with a multilayer breast phantom. The breast phantom consists of a homogeneous normal breast tissue simulant covered by a thin layer of skin simulant. A small synthetic malignant tumor is embedded in the breast phantom. We have developed several tumor simulants that yield the range of dielectric contrasts between normal and malignant tissue that are expected in clinical scenarios. A microwave sensor comprised of a synthetic planar array of compact ultrawide-band (UWB) antennas is immersed in a coupling medium above the breast tissue phantom. At each position in the array, the antenna transmits a synthetically generated pulse (1-11 GHz) into the phantom. The received backscatter signals are processed by a data-adaptive algorithm that removes the artifact caused by antenna reverberation and backscatter from the skin-breast interface, followed by 3-D space-time beamforming to image backscattered energy as a function of location. Our investigation includes a numerical (finite difference time domain) and experimental study of the UWB antenna performance in the immersion medium, as well as a study of the influence of malignant-to-normal breast tissue dielectric contrast on dynamic range requirements and tumor detectability. This paper represents the first experimental demonstration of 3-D MIST beamforming in multilayer breast phantoms with malignant-to-normal dielectric contrasts down to 1.5 : 1 for a 4-mm synthetic tumor.

Time-domain array factor for UWB antenna array

A cross-correlation formulation for the computation of time-domain array factor for ultra-wideband (UWB) antenna arrays is presented. In addition, a dual band UWB waveform is proposed for high directivity and high-resolution radar imaging. The dual band UWB waveform is based on a frequency truncated, Gaussian modulated, higher-order sinusoidal UWB pulse.

Demonstration of a wide-band fiber-optic nulling system for array antennas

A novel technique for forming and steering squint-free wide-band nulls in the far-field pattern of an ultrawide-band array antenna is presented. The nulling system relies upon a fiber-optic dispersive prism tapped delay-line microwave filter to generate the appropriate nulling waveform. The null-forming architecture was integrated with a wide-band fiber-optic dispersive prism true-time-delay transmit beamformer for demonstration in an anechoic chamber. Measurements show null depths of the order of 15 dB over the 4-18-GHz bandwidth of the system for various steering angles. The demonstrated architecture may be used for simultaneous wide-band beamforming, sidelobe reduction, and jammer suppression.

Dynamic null steering in an ultrawideband time-steered array antenna

We develop a method for forming squint-free wideband nulls in the antenna pattern of an ultrawideband array antenna. The technique uses an optical dispersive-prism beam former to provide time-delayed microwave signals to each antenna element for forming a squint-free main beam. The amplitude-modulated optical carrier is propagated through a set of optical links. Each link feeds an array element and includes an amount of dispersion proportional to element position. Tuning the wavelength of the optical carrier controls the microwave signal's arrival-time delay gradient across the array. A dispersive-prism tapped delay-line microwave filter is used to frequency shape a nulling signal. The wideband nulls do not significantly distort the main beam and are steered independently of the main beam. The technique is applied to sidelobe nulling for a transmitter and for jammer suppression for a receiver array.