Ultra-wideband Antenna Array Research Articles

Planar array of right-angled isosceles triangular microstrip antenna using Koch and meander lines for the Internet of things

An ultrawideband antenna array using a right-angled isosceles triangular microstrip antenna as a basic element is presented using inset feed for applications in the Internet of things. A Koch fractal antenna array with defected ground plane is used to generate multiband applications. Further, meander lines are added to increase the equivalent inductance that reduces the size of the antenna and increases the bandwidth and gain. Antenna arrays have been constructed and experimentally studied. The measured results show good agreement with the numerical prediction and wideband operation.

Low Cross-Polarization Vivaldi Arrays

This paper introduces a Vivaldi-type ultra-wideband antenna array with low cross-polarization, termed the Sliced Notch Antenna (SNA) array. High cross-polarization when scanning in the non-principal planes has long been a problem in Vivaldi arrays without a universal solution. In this paper, we shed light on the root cause of this long-standing issue, clarifying that a high ratio of vertical-to-horizontal current potentials along the upper radiator fin is primarily responsible for elevated cross-polarization (and not strictly the element profile). This finding therein motivates the main technical innovation in the present work—a simple reconfiguration of the upper Vivaldi fin into a series of coupled conductor segments to effectively control the aforementioned current ratio for significant reductions in cross-polarization, without reducing element profile or considerably hindering the excellent match and radiation efficiency of the original Vivaldi. Theory and design methodology for the SNA array are formulated, and followed by a concise set of design guidelines that are applied to reconfigure a representative 10:1 Vivaldi element into an SNA for practical reference, exhibiting a 20 dB reduction in peak cross-polarization ratio. This paper considers the case of single-polarized arrays as a first introduction to the SNA, though the method has been verified to work equally well (if not better) in dual-polarized arrays.

A Noble UWB Array with Band Notch Characteristics

A miniaturized four-element microstrip array of dimension (22 × 19 × 1.58) mm3 has been designed for ultra wideband (UWB) application. Unlike existing UWB arrays, the new UWB array is proposed for multiband applications. The key contribution of this paper is that both the layers (upper and lower) of FR4 substrate have been used to design the radiating elements for achieving a compact UWB structure. It is a challenging task for the researchers to design a miniaturized UWB array that offers uniform gain as gain is the major limitation of a UWB antenna. In this paper, four antenna elements (two-element array on the upper surface and other two-element array on the lower surface) of same dimension of the each element have been designed in order to achieve a reduced size of the array. Array on the top surface has been connected with the array in the bottom surface through a cylindrical via of diameter 1.0 mm. This type of array design will open up a new dimension for the UWB antenna array designers by avoiding the necessity of large substrate area. Furthermore, a U-shaped microstrip resonator has been integrated with the array structure in the lower layer and as a result, a notch band has been created at WLAN band. The array has been studied both numerically and experimentally. Prototype antennas with two and four-element arrays have been fabricated, tested and a remarkable agreement has been observed between the measured and the simulated results.

A Compact UWB Koch Fractal Antenna for UWB Antenna Array Applications

In this paper, compact ultrawideband (UWB) antennas (1-Element and 2-Element) are presented in order to demonstrate application of fractal geometry in UWB antenna design, which helps to improve the antenna characteristics in a given smaller area. Some features of Euclidean shape geometry are improved after the application of fractals at the edges of the polygon. It is demonstrated that the application of Koch fractal in the antenna design helps to achieve the desired miniaturization, compactness and wideband operability due to its self-similar and space filling characteristics. An analytical expression is provided to calculate the effective length and area of the structure with the increase in iteration's order. Its performance is further compared with other fractal geometries such as Minkowski and Sierpinski curve. It is observed that the proposed Koch fractal based antenna yields the widest bandwidth and better gain compared to other fractal geometry based antennas. In addition, the time-domain analysis of the antenna is performed in terms of fidelity factor and its values are better than 0.81. 1-Element antennas shows operational bandwidth from 2.3 to 13.2 GHz with a maximum gain value of 3.8 dB, whereas in case of 2-Element antenna operating bandwidth is 2.3?14 GHz with a maximum gain value of 7.2 dB. Moreover, the radiation patterns of the single element and 2-Element are nearly omnidirectional. These characteristics offer opportunities to explore the proposed UWB antenna for various applications such as WPAN, WBAN, etc.

Multi-objective optimization for UWB antenna array by APSO algorithm

In this paper, a uniform circular antenna array (UCAA) combining genetic algorithm (GA) or asynchronous particle swarm (APSO) for finding out global maximum of multi-objective function in indoor ultra-wideband (UWB) communication system is proposed. The algorithm is used to synthesize the radiation pattern of the directional UCAA to reduce the bit error rate (BER), to increase received energy and channel capacity in indoor UWB communication system. Using the impulse response of multipath channel, the BER of the synthesized antenna pattern on binary antipodal-pulse amplitude modulation system can be calculated. Based on topography of the antenna and the shooting and bouncing ray/image techniques, the synthesized problem can be reformulated into a multi-objective optimization problem which would be solved by the GA and APSO. Numerical results show that the fitness value and convergence speed by APSO is better than those by GA. The results also show that for multi-objective problem APSO compared to GA can reduce the BER substantially. Moreover, APSO can get better results for both line-of-sight and non line-of-sight cases.

Planar, compact ultra‐wideband polarisation diversity antenna array

A new compact multiple-input multiple-output (MIMO) ultra-wideband (UWB) antenna array is presented. The antenna array initially consisted of two monopoles placed side by side at a distance of 4 mm. A strong mutual coupling was observed so the design was modified by rotating the second radiator at 90° at a distance of 1 mm. Wideband isolation is achieved by exploiting polarisation diversity of antenna elements. Simulation in HFSS and printed prototype results validate the high isolation, over 21 dB on the entire 2.5–12 GHz frequency range. A prototype was fabricated on a low loss substrate of Rogers TMM4 measuring 23 × 39.8 mm2. To evaluate the diversity performance, the envelope correlation coefficient was calculated resulting below −20 dB, thus ensuring good diversity performance. The compactness of the proposed UWB-MIMO design is finally compared against alternative solutions already present in the literature.

Flexible 16 Antenna Array for Microwave Breast Cancer Detection.

Radar-based microwave imaging has been widely studied for breast cancer detection in recent times. Sensing dielectric property differences of tissues has been studied over a wide frequency band for this application. We design single- and dual-polarization antennas for wireless ultrawideband breast cancer detection systems using an inhomogeneous multilayer model of the human breast. Antennas made from flexible materials are more easily adapted to wearable applications. Miniaturized flexible monopole and spiral antennas on a 50-μm Kapton polyimide are designed, using a high-frequency structure simulator, to be in contact with biological breast tissues. The proposed antennas are designed to operate in a frequency range of 2-4 GHz (with reflection coefficient (S11) below -10 dB). Measurements show that the flexible antennas have good impedance matching when in different positions with different curvature around the breast. Our miniaturized flexible antennas are 20 mm × 20 mm. Furthermore, two flexible conformal 4 × 4 ultrawideband antenna arrays (single and dual polarization), in a format similar to that of a bra, were developed for a radar-based breast cancer detection system. By using a reflector for the arrays, the penetration of the propagated electromagnetic waves from the antennas into the breast can be improved by factors of 3.3 and 2.6, respectively.

Development of method for synchronous spark excitation of ultra-wideband antenna array elements

To test the effectiveness of screening facilities and equipment to ensure information security simple compact generators of electromagnetic radiation is needed. For this purpose it is proposed to use spark generators-radiators of powerful ultra-wideband microwave pulses. A new method to synchronize the array of spark generators-radiators is offered. This method allows to simplify the synchronization of the antenna array. The analysis of dependence an array factor on switching time of fuses and voltage distribution on the plates of strip radiators at the time of fuses breakdown is conducted. The results of mathematical modeling parameters of the linear array of spark strip radiators are confirmed by experimental results. During the experiment the effect of coherent addition of pulses generated at the breakdown time of the spark gaps of strip radiators has been observed. As a result generator radiation directivity and power has increased.

Isolation improvement of dual feed patch antenna by assimilating metasurface ground

A new octagonal ring shape metasurface structure (MSS) has been design and implemented at the back of a dual feed planar printed Ultrawideband array antenna. The proposed MSS incorporated antenna has been design and fabricated on a high permittivity (epsilon(r)=15) ceramic filled biopolymer-based sandwich structured dielectric substrate. A significant improvement of isolation (S-21) between dual port array elements of the proposed antenna has been achieved by assimilating 6 x 9 octagonal ring shape MSS with near zero refractive index in the ground plane. Measurement result shows that the proposed antenna with MSS loading has been achieved the reflection coefficient (S-11<-10 dB) bandwidths of 1.3, 1.02, 0.75, and 1.8 GHz. Stable radiation patterns with the gains of 3.42, 4.14, 5.46, and 8.28 dBi have been measured at the resonant frequencies 3.1, 4.41, 6.2, and 8.75 GHz. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1406-1409, 2015

A radar-based breast cancer detection system using CMOS integrated circuits

An ultrawideband (UWB) radar-based breast cancer detection system, which is composed of complementary metal–oxide–semiconductor integrated circuits, is presented. This system includes Gaussian monocycle pulse (GMP) generation circuits, switching (SW) matrix circuits, equivalent-time sampling circuits, and a compact UWB antenna array. During the detection process, the GMP signal with the center frequency of 6 GHz is first generated and transmitted with a repetition frequency of 100 MHz. The GMP signal is sent to a selected transmitter antenna by the SW matrix module, and the reflected signal is captured by the receiver antennas. Next, the high-speed equivalent-time sampling circuits are employed to retrieve the reflected GMP signal. A confocal algorithm is used to reconstruct the breast image. The total size for the prototype module is $45~\textrm {cm} \times 30~\textrm {cm} \times 14.5$ cm in length, width, and height, respectively, which is dramatically smaller than the conventional detection systems. Using our proposed system, we demonstrate a successful detection of 1-cm cancer target in the breast phantom.

Flexible sixteen monopole antenna array for microwave breast cancer detection.

Radar based microwave imaging (MI) has been widely studied for breast cancer detection in recent times. Sensing dielectric property differences of tissues over a wide frequency band has been made possible by ultra-wideband (UWB) techniques. In this paper, a flexible, compact monopole antenna on a 100 μm Kapton polyimide is designed, using a high frequency structure simulator (HFSS), to be in contact with biological breast tissues over the 2-5GHz frequency range. The antenna parameters are optimized to obtain a good impedance match over the required frequency range. The designed antenna size is 18mm × 18mm. Further, a flexible conformal 4×4 ultra-wideband antenna array, in a format similar to that of a bra, was developed for a radar-based breast cancer detection system.

Second-Order Cone Programming for Scan-Plane Reconstruction for the Wavelength-Scaled Array

The wavelength-scaled array architecture reduces the element count in large, ultrawideband antenna arrays by segmenting the aperture into subapertures of varying sizes and bandwidths. This results in an asymmetrical aperture of dissimilar elements with associated patterns that require significant correction. Here, we assess narrowband array performance using its far-field pattern as obtained in two steps. First, we characterize individual elements using planar near-field measurements. Second, we use second-order cone programming to optimize the complex element weights that generate the desired individual far-field element patterns derived from those measurements. This document details the far-field optimization technique, referred to here as optimized scan-plane reconstruction, and uses it to demonstrate that the asymmetric wavelength-scaled array can support low global sidelobe reduction, deep localized nulls, and/or mainbeam scanning like a conventional symmetric array.

Synthetic Bandwidth Radar for Ultra-Wideband Microwave Imaging Systems

A synthetic bandwidth radar as an approach to build ultra-wideband (UWB) imaging systems is presented. The method provides an effective solution to mitigate the challenges of UWB antenna's implementation with ideal performance. The proposed method is implemented by dividing the utilized UWB into several channels, or sub-bands, and designing an antenna array that includes a number of antennas equal to the number of channels. Each of those antennas is designed to have excellent properties across its corresponding channel. As part of the proposed approach, a two-stage calibration procedure is used to accurately estimate the effective permittivity of a heterogeneous imaged object at different angles and the phase center of each antenna for accurate delay time estimation. When imaging an object, each of the antennas transmits and captures signals only at its channel. Those captured signals are properly combined and processed to form an image of the target that is better than the current systems that use array of UWB antennas. The presented method is tested on breast imaging using the band 3-10 GHz via simulations and measurements on a realistic heterogeneous phantom.

EQUIVALENT MODEL OF PHOTOSWITCH: APPLICATION TO THE UWB ANTENNA DESIGN INTEGRATING IMPULSE FEEDING

Optoelectronic devices triggered by a laser ∞ash and operating in linear switching regime allow the generation of short pulses with small time jitters (2ps typically). An Ultra Wide Band antenna array combining as many of this photoswitches as antennas has the advantage to increase the radiation power on one hand and to ofier the agility of the radiation beam on the other hand obtained by time delay of laser illumination. During the step of antenna design, it becomes important to take into account the photoswitch integration in order to increase the peak power and the frequency band of the generated output signal. This paper presents an equivalent model of photoswitch obtained with the transient solver of CST Microwave Studio coupled within CST Design Studio. The second part of this article is dedicated to the integration of a photoswitch even within the antenna.

ULTRA-WIDEBAND ANTENNA ARRAYS: SYSTEMS WITH TRANSFER FUNCTION AND IMPULSE RESPONSE

This paper proposes some approaches to model Ultra Wideband (UWB) antenna arrays. Based on the array factor, often stipulated as not adapted for the description of the properties of UWB arrays in the literature, an analytical expression of the beampattern is developed. The achieved results are coherent with other formulations and empiric studies proposed in the literature. Furthermore, a time-frequency modeling of UWB antenna arrays is proposed using the concept of array factor and antenna efiective length.

AN UWB MICROSTRIP ANTENNA ARRAY WITH NOVEL CORPORATE-FED STRUCTURE

A novel feed network based on the microstrip/slotline transition is proposed in this paper. This feed network not only has ultra-wide impedance bandwidth but also can improve space utilization and make the design of antenna array easier. Then an ultra-wideband (UWB) antenna array with four elements fed by the network is designed. The antenna array is simulated, manufactured and measured. The results show that the impedance bandwidth with return loss under i10dB is 88.76%, from 2.35GHz to 6.1GHz. Within the impedance bandwidth, the radiation performance is satisfactory, and the gain of the array is 2.1{7.1dB, higher than that of the element. The cross-polarization level of the array is lower than i20dB, just as the element. A reasonable agreement of results is achieved between simulation and measurement.

Aperture Synthesis Method in 3d Radio Tomography

A compact portable device has been proposed for three-dimensional (3D) radio tomography, comprising a planar ultra-wideband (UWB) antenna array, a system for generating and receiving UWB signals, a switching block for the UWB antennas, and a program for tomosynthesis of the radar images. Results of numerical modeling and processing of experimental data are presented, confirming the efficiency of the device.

Single-element based ultra-wideband antenna array concepts for wireless high-precision 2-D local positioning

Abstract. We generally categorize the approaches for ultra-wideband antenna array design, and consequently propose simplified concepts for antenna arrays for a high-precision, ultra-wideband FMCW radar 2-D local positioning system to obtain robustness against multi path interference, perform angle of arrival analysis, as well as instantaneous heading estimation. We focus on low-cost and mechanical robust, industrial-application ready antennas. The antenna arrays are optimized for operation in the 5 GHz to 8 GHz frequency range and are designed towards supporting full omnidirectional 360° as well as partial half-plane direction of arrival estimation. Two different concepts for vehicle- as well as wall-mounted antenna array systems are proposed and discussed. We propose a wideband unidirectional bow-tie antenna array element having 97% impedance and 37% pattern bandwidth and a robust vehicle mounted omnidirectional antenna element having more than 85% impedance and pattern bandwidth.

Forming of energy radiation patterns of ultra-wideband antenna arrays with a low side-lobe level

Analytical expressions have been obtained for calculating an optimal waveform of the pulse exciting elements of an ultra-wideband antenna array. The criterion of optimality is the minimum of integral side-lobe level. The proposed approach enables us to take into account the signal duration and spectrum limitations and also the impulse response of antenna elements.

THE DESIGN OF AN OPTICAL TIME STEERED ANTENNA BASED ON A NEW INTEGRATED TRUE TIME DELAY UNIT

In the framework of wide-band and ultra wide-band array antennas, an Optical Time Steered Antenna (OTSA) is presented, by considering the design strategies of a new True Time Delay (TTD) Control Unit in the Beam Forming Network (BFN). The unit has high reliability, low crosstalk, low switching time and potential low cost, being based on a low cost technology. Furthermore, due to its compactness and modularity, it can be easily grouped with other ones to make a control unit of large arrays. Difierent strategies and working conflgurations of the TTD control unit are presented as a trade-ofi among hardware complexity, insertion loss reduction and beam control capability. The design of an OTSA prototype is discussed by considering a realistic model simulating the behavior of a real world antenna and accounting for unavoidable non-realities, such as random, periodic and systematic errors introduced by each device exploited in the OTSA as well as mutual coupling between radiating elements. An optimal trimming strategy, able to compensate at best for BFN errors and based on the use of suitably located trimmers, is presented. Among other cases, to enlighten the potentialities of the OTSA, an all optical architecture providing a difierence beam squint free pattern is also proposed.