Ultra-wideband Antenna Elements Research Articles

Synthesis of Large Ultra-wideband Sparse Circular Planar Arrays Based on Rotationally Symmetric Structure

This article aims to improve the synthesis efficiency and radiation performance of large ultra-wideband (UWB) rotationally symmetric sparse circular planar arrays by using a modified differential evolution algorithm (MDEA). In the proposed MDEA, we adopt a new encoding mechanism in which an individual represents an element position expressed in polar coordinates. Importantly, such an encoding mechanism can facilitate the multiplication calculation for the array factor in the individual being updated while making it easier to meet the given minimum element spacing constraint. Moreover, to cater to the new encoding mechanism, some low-dimensional evolution operators are introduced to avoid the prematurity. In particular, the UWB rotationally symmetric sparse planar array synthesis problem is transformed into the sidelobe suppression problem of the array pattern at the highest frequency under the given array aperture, and the minimum spacing constraints is used to guarantee enough space to place physical UWB antenna elements. Two synthesis examples of UWB sparse planar arrays based on rotationally symmetric structures are presented. The results show that the peak sidelobe level (PSL) obtained by the proposed MDEA is significantly lower than the results obtained by some existing algorithms in an acceptable CPU time, which proves the effectiveness and superiority of the proposed MDEA.

Synthesis of Large Ultrawideband Sparse Planar Arrays by Utilizing a Cooperative Coevolutionary Iterative Fourier Transform

This letter introduces a cooperative coevolutionary iterative Fourier transform (CCIFT) technique to extend the conventional IFT to large ultra-wideband (UWB) sparse planar array synthesis. In the proposed CCIFT, a dense initial element position grid such as a spacing of half a wavelength at the highest frequency is adopted to avoid the presence of grating lobes at high frequency band, and a probability-assisted element selection mechanism is presented to guarantee the obtained array layout to meet a preset minimum spacing constraint, enabling the placement of physical UWB antenna elements. In addition, a cooperative coevolutionary strategy is presented to avoid prematurity by establishing the information interaction between different excitation distributions from multiple parallel IFT procedures. Two examples are conducted and results show that the CCIFT can achieve a considerably lower peak sidelobe level (PSL) than some state-of-art algorithms within an acceptable CPU time, which demonstrates its effectiveness and superiority.

Pattern diversity and isolation enhancement of UWB MIMO antenna based on characteristic modes for mobile terminals

AbstractA printed ultra-wideband (UWB) multiple input multiple output antenna with isolation enhancement and pattern diversity is presented, which is based on characteristic modes (CM) for upcoming wireless mobile platforms. The presented antenna is composed of dual UWB antenna elements (AEs) – an antipodal Vivaldi and a circular-shaped monopole positioned on the two opposite edges of the antenna's rectangular-shaped ground surface. The two AEs are capable to stimulate distinct modes in the ground surface and therefore obtaining the required distinct radiation (far-field) patterns and highly isolated AEs without introducing any decoupling structure (DS). The measured results demonstrate that both AEs are UWB with an operating frequency from 2.6 to 11 GHz. The measured isolation is more than 30.1 dB with a maximum value of 55 dB in UWB. The peak realized gain is over 0.83 dBi. The radiation efficiency is greater than 75%. The Envelope Correlation Coefficient is <0.08.

MODELING THE CHARACTERISTICS OF A BROADBAND ANTENNA SYSTEM FOR UAV DIRECTION FINDING

The paper presents the results of the development and modelling of a broadband antenna system for Unmanned Aerial Vehicle (UAV) direction finding. The research covered the issues of analytical description of the antenna system based on the prototype – the Vivaldi antennas. The article presents a mathematical description of the Vivaldi antenna element model. An experimental relationship between the geometrical parameters and characteristics of the antenna has been established. A review of the current state of the issue of designing antenna systems based on the concept of building ultra-wideband directional antenna elements in the absence of a phase centre has been carried out. The main trends in the modern design of broadband antenna systems are determined. The main parameters of the proposed broadband antenna are determined by the method of mathematical modelling. The parameters of the proposed antenna in the frequency range under various excitation conditions are studied, and the specifics of the application of such a system under the conditions of its possible use as part of UAV direction-finding complexes are given. The most optimal design option for an ultra-wideband antenna element is a design with an expanding slot (similar to Vivaldi antennas). At present, these antennas are widely used in various devices, namely, in radio reconnaissance devices, medical equipment, etc. Their popularity is due to the presence of advantages over other antennas, among which are a wide operating frequency range, simple design, simple manufacturing requirements, and high gain. In this paper, we considered Tapered Slot Antenna – an antenna with a widening slot. The antenna element designed and modelled in the article is a modified Vivaldi antenna (an antenna with a quasi-slot line with expansion), which is being developed for the direction-finding complex of the UAV. When calculating the TSA of the antenna element, the program for calculating the characteristics of the antennas MMANA was used in order to accelerate the study of the main laws for obtaining the required characteristics. Particular attention was paid to the possibility of changing the radiation pattern (RP) depending on the phase relations of the voltage at the input of the antenna elements.

Design of a co‐planar waveguide‐fed flexible ultra‐wideband ‐ multiple‐input multiple‐output antenna with dual band‐notched characteristics for wireless body area network

In this article, a co-planar waveguide-fed ultra-wideband (UWB) multiple-input multiple-output flexible antenna with dual band-notched characteristics on liquid crystal polymer substrate with high isolation for wireless body area network application is designed and fabricated. Two fan-shaped monopole UWB antenna elements are designed and placed vertically, with tampered feeder, asymmetrical ground plane and two C-shaped slots on the radiation patch. The measured working bandwidth can reach 2.63–11.6 GHz and the rejection bands are 3.25–4.36 and 5.41–6 GHz. The port isolation (S21) is better than −22 dB. When the bending radius is 35 and 45 mm, the antenna is measured for flexibility. In addition, the antenna is placed on human tissue to test its performance. All the results show that it has good radiation, high isolation and flexibility, and has broad application prospects in the wearable field.

Dual-band-notched UWB MIMO antennas with miniaturization using half-cutting technology

Abstract A compact four-element ultra-wideband (UWB) multiple-input–multiple-output (MIMO) antenna with dual polarization and dual-notched capabilities was developed and fabricated. The MIMO antenna is composed of four orthogonally placed half-cutting UWB antenna elements. This orthogonal placement improves the isolation. Furthermore, an L-shaped slot and a continuous bending slot are etched to realize the band-rejection function in the WiMAX and WLAN bands. The result shows that the antenna achieved operating bands of 2.9–16.5 GHz (140.2%, S11 < −10 dB), fully covering the UWB (3.1–10.6 GHz). The port isolation is greater than 23 dB in the frequency band of interest, excluding two rejected bands. Moreover, the MIMO antenna has excellent diversity performance, such as a low envelope correlation coefficient (<0.004), high diversity gain (approximately 10 dB), and good omnidirectional radiation characteristics.

Design and Analysis of a Compact UWB-MIMO Antenna with Improved Isolation for UWB/WLAN Applications

For space limited ultra-wideband (UWB) communication system, the small foot print of the multi-input multi-output (MIMO) antenna is highly desirable. A significant subject of the investigation is the creation of a small MIMO antenna with enhanced isolation and large operating bandwidth. To accomplish this object, a compact size two-port UWB-MIMO antenna is presented in this article. The proposed antenna consists of opposite faced semi-circular monopole radiating elements. The opposite orientation of the radiating elements is offered low envelope correlation coefficient (ECC) and good pattern diversity. The improved bandwidth and enhanced isolation are achieved by etching the ground plane with a rectangular defected ground structure structure. Antenna size optimization is taking placed with evolution of the compact size single UWB antenna element. The computer simulation tool is used to complete the design and optimization process. The optimized size of the proposed antenna is 20 × 20 mm2 or electrical size of 0.469 λ0 × 0.469 λ0. The fabricated prototype of the antenna is experimentally evaluated and validated by the comparison of the simulated and measured results. However, obtained results show well agreement. The proposed antenna has extended UWB bandwidth 2–12 GHz (fractional bandwidth of 142.8%) and improved isolation of less than 25 dB, and low value of ECC (0.05). The antenna size, isolation, operating bandwidth, and ECC are compared with previously reported work. Furthermore, the proposed antenna is preferable for WLAN and UWB applications.

A novel UWB MIMO antenna array with band notch characteristics using parasitic decoupler

ABSTRACT This paper presents a 4 × 4 multiple-input–multiple-output (MIMO) antenna array for ultra-wide band (UWB) applications with 5.5 GHz wireless local area network (WLAN) band rejection characteristics. The single UWB antenna element consists of modified patch antenna with partial ground plane. WLAN band has been rejected by etching a U-shaped slot in the antenna element. The antenna elements have been arranged in a planar geometry where each element is orthogonal to its adjacent element. A fan-shaped parasitic decoupler, that consists of four strip lines connected with a central square-shaped conductor, is placed among the antenna elements. The dimensions of the antenna array are 67 × 67 × 1.6 mm3. Full wave simulations and experiments have been conducted where measured peak gain and average isolation were 8.1 and −20 dB, respectively. The calculated envelop correction coefficient was less than 0.01.

Planar UWB MIMO Antenna With Pattern Diversity and Isolation Improvement for Mobile Platform Based on the Theory of Characteristic Modes

This communication presents a planar ultra-wideband multi-input multi-output antenna with pattern diversity and isolation improvement based on the theory of characteristic modes. The proposed antenna (for new-generation wireless mobile terminals) consists of two ultra-wideband antenna elements—a compact quarter loop and a circular planar monopole located on the opposite edges of a rectangular ground plane. These two antenna elements are able to excite different modes in the ground plane and thus realize the desired diverse radiation patterns and high isolation without any additional decoupling structures. The experimental results show that both antenna elements are ultra-wideband with impedance bandwidths (return losses more than 6 dB for the quarter-loop antenna and more than 10 dB for the circular planar monopole antenna) of 130% (2–9.5 GHz). The isolation is over 20 dB with a peak value of 50 dB. The realized gains are above 1.5 dBi. The total efficiencies are above 70%. The envelope correlation coefficient is less than 0.03 assuming that the antenna operates in an isotropic channel.

A Differential-Fed UWB Antenna Element With Unidirectional Radiation

A new differential-fed broadband antenna element with unidirectional radiation is proposed. This antenna is composed of a folded bowtie, a center-fed loop, and a box-shaped reflector. A pair of differential feeds is developed to excite the antenna and provide an ultrawideband (UWB) impedance matching. The box-shaped reflector is used for the reduction of the gain fluctuation across the operating frequency band. An antenna prototype for UWB applications is fabricated and measured, exhibiting an impedance bandwidth of 132% with standing wave ratio ≤ 2 from 2.48 to 12.12 GHz, over which the gain varies between 7.2 and 14.1 dBi at boresight. The proposed antenna radiates unidirectionally with low cross polarization and low back radiation. Furthermore, the time-domain characteristic of the proposed antenna is evaluated. In addition, a $2 \times 2$ element array using the proposed element is also investigated in this communication.

Compact MIMO Slot Antenna for UWB Applications

A compact four-element multiple-input–multiple-output (MIMO) antenna for portable wireless ultrawideband (UWB) applications is presented in this letter. The proposed UWB MIMO antenna has the compact size of $ 42 \times 25 ~\hbox{mm}^2$ . The microstrip-fed stepped-slot antenna acts as a single UWB antenna element. The UWB antenna covers the wide frequency band from 3.1 to 12 GHz. High isolation ( $ \geq 22~\hbox{dB}$ ) is achieved between the UWB antenna elements without any decoupling network. It is due to inherent directional radiation properties of slot antennas (SAs) and their asymmetrical placements. The measured impedance bandwidth of UWB MIMO antenna is from 3.2 to 12 GHz with the isolation better than 22 dB over the entire UWB spectrum. The envelope correlation coefficient (ECC) as well as channel capacity loss (CCL) are investigated, and they are within their acceptable limits.

SKALA, a log-periodic array antenna for the SKA-low instrument: design, simulations, tests and system considerations

The very demanding requirements of the SKA-low instrument call for a challenging antenna design capable of delivering excellence performance in radiation patterns, impedance matching, polarization purity, cost, longevity, etc. This paper is devoted to the development (design and test of first prototypes) of an active ultra-wideband antenna element for the low-frequency instrument of the SKA radio telescope. The antenna element and differential low noise amplifier described here were originally designed to cover the former SKA-low band (70-450MHz) but it is now aimed to cover the re-defined SKA-low band (50-350MHz) and furthermore the antenna is capable of performing up to 650MHz with the current design. The design is focused on maximum sensitivity in a wide field of view (+/- 45deg from zenith) and low cross-polarization ratios. Furthermore, the size and cost of the element has to be kept to a minimum as millions of these antennas will need to be deployed for the full SKA in very compact configurations. The primary focus of this paper is therefore to discuss various design implications for the SKA-low telescope.

DESIGN AND IMPLEMENTATION OF CONNECTED ANTENNA ARRAY FOR ULTRA-WIDEBAND APPLICATIONS

An integrated eight-element antenna array has been proposed for ultra-wideband (UWB) applications. It consists of eight UWB antenna elements and an eight-way binary-tree modified Wilkinson power divider. Any two adjacent elements in the array are connected to each other and share a common side, thus leading to a connected antenna array. Moreover, this arrangement can be utilized to avoid grating lobe level at higher frequencies. Each antenna element comprises a square ring patch and is excited by a tapered balun to achieve low cross-polarization levels. In order to validate the design, a prototype has been fabricated and measured. Both simulated and measured results confirm that the proposed integrated antenna array achieves a good performance of a reflection coefficient below -10 dB from 2.9 GHz to 10.8 GHz, including stable radiation patterns with low side lobe and cross-polarization levels, thus the antenna is promising for applications in UWB imaging systems.

Compact UWB Antenna Design for MIMO Applications

In this study, a compact printed Multiple-Input-Multiple-Output (MIMO) antenna with a dimension of 32×70 mm² has been proposed for Ultra-Wideband (UWB) systems applications. The design constitutes of two identical UWB antenna elements, which is etched onto a Taconic TLC-30 printed circuit board. The proposed antenna has been designed and simulated using computer simulation software. For validation purposes, antenna prototype is fabricated and tested. The UWB-MIMO antenna yields an impedance bandwidth of 2.9 to 12 GHz with a return loss of less than-10 dB. Furthermore, the isolation characteristic between the two antenna elements is more than 15 dB within the operating frequency range. The designed structure is found to provide good MIMO/diversity characteristic across the UWB band.

FOCUSING PROPERTIES OF ULTRA WIDEBAND TRANSIENT ARRAYS

Some new focusing properties of time-domain ultra wide band (UWB) focusing array antennas are presented. The large current radiator (LCR) is considered as the UWB antenna element. Each LCR is replaced by a set of inflnitesimal dipoles modeling both the near fleld and the far fleld patterns of the antenna element, as well as the coupling between the elements. Several antenna arrays with difierent sizes and numbers of elements are modeled. It is shown that similar to narrow band antennas, the actual maximum fleld region shifts from the intended focus region towards the antenna aperture.

Experimental Characterization of UWB Beamformers Based on Multidimensional Beam Filters

Ultrawideband (UWB) communication systems can benefit significantly by employing adaptive spatial filtering, or beamforming, using an array of UWB antenna elements. Previously, the authors have reported on a multidimensional and low-complexity beamforming technique that predicted significant improvements in communication system performance based on computational models of the radio channel. Here, the authors utilize a low-complexity spatial filter in conjunction with measured UWB signals using an experimental antenna array to demonstrate a significant improvement in system bit error rate using a real UWB channel in a multi-user environment.

Planar ultrawideband antenna array for short‐range wireless communications

AbstractIn this article, novel 2‐element and 4‐element planar ultrawideband (UWB) antenna arrays with bidirectional radiation patterns based on identical UWB antenna elements for UWB communications applications have been proposed, simulated and experimentally investigated. Each array is constructed by means of feeding omni‐directional printed UWB monopole antennas with a UWB power divider. The proposed 2‐element antenna array yields an impedance bandwidth of 110% (3.1–10.6 GHz) covering the whole UWB frequency bandwidth while the impedance bandwidth is multi‐band in case of the 4‐element antenna array because of the increasing effect of mutual coupling among antenna elements. The calculated gain of the 2‐element and 4‐element array is quite stable with about 3 and 6 dB higher than that of the single element, respectively. Both measured and calculated E‐plane radiation patterns of the array and the single element are almost the same while the H‐plane radiation patterns of the array are distinctively bidirectional compared to the omni‐directional pattern of the single element. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1061–1066, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25140

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

Free-space power combining and beam steering of ultra-wideband radiation using an array of laser-triggered antennas

A mode-locked laser is used to synchronize jitter-free ultrawideband (UWB) pulse generation at an array of UWB antenna elements. The jitter-free pulses radiated by each element add together in free space to produce a radiated field pattern that is steerable via optical true-time-delay techniques. The results from a three element array experiment are presented and used to develop a model for an N-element phased array. A transmission-line model is presented for a single array element, which includes the functions of energy storage, as well as UWB pulse generation and radiation.