Vivaldi Antenna Array Research Articles

A SIW Antipodal Vivaldi Array Antenna Design

A kind of compact SIW (substrate integrated waveguide) Vivaldi array antenna is proposed and analyzed. The antenna consisted of 4 Vivaldi structure radiation elements fed by an equal power divider with SIW technology. The radiation element is composed of antipodal index gradient microstrip lines on both sides of the substrate. The measured reflection coefficient of the array antenna is less than −10 dB from 8.88 GHz to 10.02 GHz. The measured gain of the array antenna is 13.3 dB on 9.5 GHz.

A Wideband End-Fire Conformal Vivaldi Antenna Array Mounted on a Dielectric Cone

The characteristics of a novel antipodal Vivaldi antenna array mounted on a dielectric cone are presented. By employing antipodal Vivaldi antenna element, the antenna array shows ultrawide bandwidth and end-fire radiation characteristics. Our simulations show that the cone curvature has an obvious influence on the performance of the conformal antenna, in terms of both the bandwidth and the radiation patterns. The thickness and permittivity of the dielectric cone have an effect on the bandwidth of the conformal antenna. Measurement results of both single antenna and conformal antenna array show a good agreement with the simulated results. The measured conformal antenna can achieve a −10 dBS11with bandwidth of 2.2–12 GHz and demonstrate a typical end-fire radiation beam. These findings provide useful guidelines and insights for the design of wideband end-fire antennas mounted on a dielectric cone.

Theory of cylindrical arrays of Vivaldi antennas in the single-mode approximation

Periodic arrays of Vivaldi antennas are considered. Cylindrical arrays infinite along one coordinate are analyzed. For arrays with axial symmetry, a model in the form of the Floquet channel is substantiated. For the Floquet channel of a cylindrical array, a model in the form of the Floquet channel of a planar array with variable period is proposed. Transmission of the fundamental mode of the Floquet channel is described in the single-mode approximation, in which only the forward and counter-propagating fundamental modes are taken into account. The scattering matrix of the Floquet channel of a cylindrical array is determined in the single-mode approximation. Relationships for the reflection coefficient in the quasi-periodic excitation mode are derived. Results of numerical calculations are presented.

Planar arrays of Vivaldi antennas in the single-mode approximation

Periodic arrays of Vivaldi antennas are considered. Planar arrays infinite along two coordinates are analyzed. A planar array is studied with the use of a well-known model in the form of the Floquet waveguide with variable parameters. Propagation of the fundamental mode of this structure is described in the single-mode approximation in which only forward and counter-propagating fundamental modes are taken into account. An equivalent circuit of the Floquet waveguide with variable parameters is proposed. The concept of the characteristic impedance of the wave of an array of slot transmission lines is introduced and used for calculation of the scattering matrix of the Floquet waveguide with variable parameters. Results of numerical calculations are presented.

Timed Vivaldi arrays for steerable energy pattern with low side lobes

A novel design of timed Vivaldi antenna arrays for steerable energy patterns is presented in this work. Three geometries are studied and designed in order to obtain an optimum energy pattern with low side lobe level (SLL) during beam steering: equally antenna array, unequally antenna array, and concentric ring array. The antenna elements are fed with the fifth derivative Gaussian pulse. The design process is carried out by the well-known sequential quadratic programming. Three design examples with 16 antenna elements are studied by considering different distribution of antenna positions. The mutual coupling phenomenon is considered by full wave simulations of Vivaldi antenna elements in the design examples. The results show a good performance of the steerable energy pattern with low SLL with ultra wideband operation.

Improvement on a 2 × 2 Elements High-Gain Circularly Polarized Antenna Array

A novel antipodal Vivaldi antenna with tapering serrated structure at the edges is proposed. Compared with traditional Vivaldi antennas without serrated structure, the gain of the designed antenna is significantly improved in the desired frequency band (4.5–7.5 GHz). In addition, a 2 × 2 Vivaldi antenna array with an orthorhombic structure is designed and fabricated to achieve a circular polarization (CP) characteristic. With this configuration, the 3 dB axial ratio bandwidth of the array reaches about 42% with respect to the center frequency of 6 GHz and a high gain is achieved as well. The novel Vivaldi antenna and CP antenna array both have ultrawide band (UWB) and high-gain characteristics, which may be applied to the field of commercial communication, remote sensing, and so forth.

C-Band Vivaldi Antenna and Its Array

A novel Vivaldi Antenna has been designed for IEEE C-band i.e. 4-8 GHz. The objective of the design is to achieve return loss better than -10 dB over the entire frequency range with a moderate gain ranging from 4-9 dB. The minimum half power beamwidth required in both Azimuth and Elevation planes is 500 so that designed Vivaldi Antenna element can be used for wide angle scanning. The designed antenna has been fed by a stripline that helps in efficient coupling of microwave power to slotline. The triplicate structure of Vivaldi Antenna helps in reducing the spurious radiations from stripline feed. A 5×1 H-plane C-Band Vivaldi Antenna array has been designed to find out the effect of array environment on the characteristics of Vivaldi Antenna. All the designs, simulations and analysis have been done in CST Microwave Studio 2011.

Generation of OAM Radio Waves Using Circular Vivaldi Antenna Array

This paper gives a feasible and simple solution of generating OAM-carrying radio beams. Eight Vivaldi antenna elements connect sequentially and fold into a hollow cylinder. The circular Vivaldi antenna array is fed with unit amplitude but with a successive phase difference from element to element. By changing the phase difference at the steps of 0, ±45°, ±90°, ±135°, and 180°, the OAM radio beam can be generated with mode numbers 0, ±1, ±2, ±3, and 4. Simulations show that the OAM states of ±2 and ±3 are the same as the traditional states, while the OAM states of 0, ±1, and 4 differ at the boresight. This phenomenon can be explained by the radiation pattern difference between Vivaldi antenna and tripole antenna. A solution of distinguishing OAM states is also proposed. The mode number of OAM can be distinguished with only 2 receivers.

Ladder Arrangement Method for Stealth Design of Vivaldi Antenna Array

A novel stealth design method for X-band Vivaldi antenna arrays is proposed in this paper by ladder arrangement along radiation direction. Two-element array, eight-element array, and 3 × 7-element array are investigated in this paper. S parameters, RCSs, and radiation patterns are studied, respectively. According to the ladder arrangement of Vivaldi antennas presented, 16.3 dBsm maximal RCS reduction is achieved with satisfied radiation performance. As simulated and measured, results demonstrate that the effectiveness of the presented low RCS design method is validated.

Improvements in a 4-Element High Gain Directional UWB Antenna Array

In this paper, a novel serrated structure at the edges of the antipodal Vivaldi antenna is introduced. Compared with the Vivaldi antenna without serrated structure, the novel structure antenna has a better Front-to-Back ratio (F/B ratio). Additionally, when building a 4-element array with mirror image elements placed alternately along the H plane, the cross-polarization level at the boresight is reduced a lot compared to conventional array configuration. The design of the novel 4-element Vivaldi antenna array with mirror image elements described in this paper experimentally produces a gain with a range of 9∼15 dBi, F/B ratio more than 15 dB, and cross-polarization level at the boresight is reduced more than 10 dB from 3.5 GHz to more than 10.6 GHz with –10 dB return loss. The novel antenna array can be used for directional UWB systems.

DEVELOPMENT OF A NOVEL UWB VIVALDI ANTENNA ARRAY USING SIW TECHNOLOGY

A compact Vivaldi antenna array printed on thick substrate and fed by a Substrate Integrated Waveguides (SIW) structure has been developed. The antenna array utilizes a compact SIW binary divider to significantly minimize the feed structure insertion losses. The low-loss SIW binary divider has a common novel Grounded Coplanar Waveguide (GCPW) feed to provide a wideband transition to the SIW and to sustain a good input match while preventing higher order modes excitation. The antenna array was designed, fabricated, and thoroughly investigated. Detailed simulations of the antenna and its feed, in addition to its relevant measurements, will be presented in this paper.

An EBG spatial power combiner

AbstractA new electromagnetic bandgap (EBG) spatial power combiner is proposed. The prototype consists of the design of the EBG ground holes structure, the active‐EBG coupler, and the Vivaldi antenna array. A 17 dB system gain coupled with a 5.5 GHz of impedance bandwidth and good out‐of‐band suppression has been achieved. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1534–1536, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23421

DESIGN OF COMPACT VIVALDI ANTENNA ARRAYS FOR UWB SEE THROUGH WALL APPLICATIONS

Two different types of Vivaldi antenna arrays have been designed for UWB see through wall applications. The first is a 16 × 1 antipodal Vivaldi antenna covering 8-12 GHz, and the second is an 8×1 tapered slot antenna for 2-4 GHz frequency range. The array elements are optimized to have a compact size and almost constant gain with frequency. Wilkinson power dividers were designed and fabricated to compose the feed network for the Vivaldi antenna arrays. Measured results of the manufactured antipodal and tapered slot Vivaldi antenna arrays are in excellent agreement with the simulated ones, with a gain of more than 13dBi and 12 dBi respectively within their respective operating band. The first array is geared towards see through dry wall with high resolution, while the second is designed at lower frequencies to allow see through concrete wall applications. Full arrays were manufactured and connected to multi-throw switches and have been utilized as part of synthetic aperture radar.

Novel switched sector beam planar UWB antenna

AbstractA planar Vivaldi array antenna that can achieve four sector radiation patterns in the azimuth plane is presented. Prototypes of the proposed antenna operating within 3.1–10.6 GHz for ultrawideband applications were designed and constructed. Measured and simulated results are used to demonstrate the performance of the antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1185–1187, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22388

Solution of large complex problems in computational electromagnetics using higher-order basis in MoM with out-of-core solvers

In a recent invited paper in the IEEE Antennas and Propagation Magazine, some of the challenging problems in computational electromagnetics were presented. One of the objectives of this note is to simply point out that challenging to one may be simple to another. This is demonstrated through an example cited in that article. The example chosen is a Vivaldi antenna array. What we discuss here also applies to the other examples presented in that article, but we have chosen the Vivaldi antenna array to help us make our point. It is shown in this short article that a higher-order basis using a surface integral equation a la a PMCHWT (Poggio-Miller-Chu-Harrington-Wu-Tsai) method-of-moments formulation may still be the best weapon that one have in today's arsenal to deal with challenging complex electromagnetic analysis problems. Here, we have used the commercially available code WIPL-D to carry out all the computations using laptop/desktop systems. The second objective of this paper is to present an out-of-core solver. The goal is to demonstrate that an out-of-core 32-bit-system-based solver can be as efficient as a 64-bit in-core solver. This is quite contrary to the popular belief that an out-of-core solver is generally much slower than an in-core solver. This can be significant, as the difference in the cost of a 32-bit system can be 1/30 of a 64-bit system of similar capabilities using current computer architectures. For the 32-bit system, we consider a Pentium 4 system, whereas for the 64-bit system, we consider an Itanium 2 system for comparison. The out-of-core solver can go beyond the 2 GB limitation for a 32-bit system and can be run on ordinary laptop/desktop; hence, we can simultaneously have a much lower hardware investment while better performance for a sophisticated and powerful electromagnetic solver. The system resources and the CPU times are also outlined.

Effect of Dielectric Permittivity on Infinite Arrays of Single-Polarized Vivaldi Antennas

The effect of dielectric substrate on the performance of infinite arrays of single-polarized Vivaldi antennas is studied by computing the input impedance of an antenna in an array environment by using full wave method of moments techniques. It is found that dielectric permittivity plays an important role in the wideband performance of such arrays, and comparison with dielectric-free cases for similar geometries is also included to bring out the impact of the substrate. In particular, increasing dielectric permittivity improves the bandwidth considerably (bandwidth up to 10:1 is predicted). The parametric variation due to permittivity is presented in detail, and optimization involving other design parameters is discussed. Results from a parallel plate waveguide simulator technique employed to assess and compare the array performance of Vivaldi with different dielectric permittivities qualitatively support the predicted effect of dielectric substrate.

Research on ultra-wide band planar Vivaldi antenna array

Planar Vivaldi antenna, with attractive performance compared with conventional TEM horn antennas, was introduced and used to form array. Normalized radiation energy pattern was adopted to characterize the transmit and receive behavior of ultra-wide-band (UWB) antenna array. Finite-difference time-domain (FDTD) was used to analyze the array. Radiation energy pattern in H plane was measured in outdoor region, for the difficulty of installing, E plane pattern was not measured. Measured and simulated results indicate that the planar Vivaldi antenna array can be used in the practical UWB radar and communication system, which can increase the gain, as it has narrow beam width. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2117–2120, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21873

A non-overlapping domain decomposition method with non-matching grids for modeling large finite antenna arrays

A non-overlapping domain decomposition method (DDM) is proposed herein to solve Maxwell equations in R 3 . In this work, the Maxwell equations are discretized using a vector finite element method with hierarchical H(curl) vector basis functions. There are two major ingredients in the proposed non-overlapping DDM: (a) A proper 1st order transmission condition to enforce field continuity across domain boundaries and (b) A cement technique to allow non-matching grids for neighboring domains. Moreover, a detail Fourier analysis of the transmission condition for a canonical half-space example is presented. The analysis provides significant insights into the convergence behavior of the proposed non-overlapping DDM for solving electromagnetic radiation problems, such as the large finite antenna arrays. Particularly for the antenna arrays, the proposed non-overlapping DDM is extremely efficient since the formulation can easily incorporate geometrical repetitions. Exponentially tapered notch (Vivaldi) antenna arrays with size up to 100 × 100 elements are solved on a common PC to validate the proposed non-overlapping DDM.

TIME-DOMAIN ULTRA-WIDEBAND IMAGING RADAR EXPERIMENT FOR VERIFYING SUPER-RESOLUTION IN NONLINEAR INVERSE SCATTERING

This paper presents an experimental verification of the super-resolution phenomenon in nonlinear inverse scattering using a time-domain (TD) ultra-wideband (UWB) imaging radar system developed at the University of Illinois at Urbana-Champaign. The TD-UWB microwave imaging radar system successfully combines the UWB impulse radar system and a nonlinear inverse scattering imaging algorithm, the distorted-Born iterative method (DBIM), for nondestructive evaluation (NDE) and remote sensing purposes. The experimental data were collected from a limited view angles using a switched Vivaldi antenna array which consists of five transmitters and six receivers. The experimental data are processed with the DBIM, and show that it can resolve features smaller than the half-wavelength dictated by the Rayleigh criterion. The experimental results also demonstrate that DBIM can recover information on the backside of a penetrable scatterer even though scattering data are collected only from limited view angles from the front side of the scatterer.

Novel low-cost beam-steering techniques

This paper summarizes and compares several techniques for beam steering without the use of conventional ferrite or solid-state phase shifters. Three methods are presented: a microstrip patch antenna array fed by a dielectric image line (DIL) controlled by a reflector plate, a multimicrostrip line fed Vivaldi antenna array controlled by piezoelectric transducers (PETs) and a movable grating film fed by dielectric image line. Both theoretical analyses and experimental measurements have been carried out. The measurement results agree very well with the predictions. These new techniques have many advantages, including low cost, broad bandwidth, low loss, wide scan angle, and simplicity. These low-cost beam-steering techniques should have many applications in microwave and millimeter-wave commercial systems.