Planar Dipole Array Research Articles

Low-Profile Differentially-Fed Tightly-Coupled Dipole Array

Introduction. Tightly coupled dipoles currently belong to one of the most popular types of antenna arrays. Their main advantages include an electrically low-profile height, the ability to scan the beam across a wide sector of angles without the onset of scan blindness, and a low level of cross-polarization. In recent years, the number of publications on the topic of antenna arrays of this type has increased significantly. The authors have paid sufficient attention to baluns included in the antenna array elements. However, the possibility of implementing a differentially-fed scheme in antenna arrays of this type remains poorly studied. This makes the study of this subject especially relevant in the development of radio devices where such feed technique is preferable.Aim. Differentially-fed tightly-coupled dipole array design and study.Materials and methods. The following materials were used to create the prototype: copper sheet, ceramic glass substrate ST-50-1, dielectric RO3003. A numerical study of the characteristics was carried out in the ANSYS HFSS environment; an experimental study of the prototype was carried out in an anechoic chamber using an automated measuring complex and a vector network analyzer.Results. The results of designing a planar antenna array of tightly-coupled dipoles for the X-band are presented. In the antenna array, each of the dipole arms is fed using a separate coaxial cable, while the two arms of one dipole are fed out-of-phase. The results of a numerical study of the characteristics of an 8 × 8 antenna array made from the developed elements are presented. Across the range from 6.5 to 12.25 GHz, the average active VSWR does not exceed 3, while the gain varies from 21.5 to 25.7 dBi. The possibility of beam scanning in a sector of angles up to ±45° is shown. The results of an experimental study of the radiation characteristics and matching of the prototype of a single element are presented.Conclusion. The importance of taking into account the effects that arise at the edges of finite antenna arrays during simulations is shown. The feasibility of manufacturing and measuring antenna array prototypes with a large number of elements is experimentally confirmed. The proposed element design demonstrates the possibility of implementing the differentially-fed scheme in tightly coupled antenna arrays.

Synthesizing Circularly Polarized Multi-Beam Planar Dipole Arrays With Sidelobe and Cross-Polarization Control by Two-Step Element Rotation and Phase Optimization

In this article, a novel method is presented to synthesize multi-beam circularly polarized (CP) patterns with sidelobe level (SLL) and cross-polarization level (XPL) suppression for planar dipole arrays by optimizing both element rotations and excitation phases. Multiple sets of excitation phases are adopted as optimization variables other than the determined values according to the rotation angles in the conventional sequentially rotated technique (SRT) and the random sequentially rotated technique (RSRT), so as to improve the performance of the obtained CP multi-beam patterns. This releases many more degrees of synthesis freedom but leads to a new problem of demanding excessive computation resources for a planar rotated dipole array with multiple CP patterns. Then, a two-step rotation and phase optimization strategy is proposed to effectively solve this optimization problem. In the initial step, the common element rotations and approximated excitation phases composed of the common phase parts plus the beam focusing phase parts are found for multiple desired CP patterns with different beam directions. And then, a refining step is performed to refine the excitation phases individually for each CP beam for improved pattern performance. Four representative examples of synthesizing multi-beam patterns with both SLL and XPL suppression are provided to verify the effectiveness of the proposed method. Comparisons with the conventional SRT and RSRT are also provided to show the superiority of the proposed method.

An Asymptotic Approach for the Scan Impedance in Infinite Phased Arrays of Dipoles

This work presents an analytic model to derive the scan impedance of planar infinite phased arrays of dipoles at a dielectric interface when only the (0, 0) Floquet mode propagates. The proposed model builds on the boundary conditions met by the fundamental Floquet mode at the interface to provide a novel derivation of the equivalent circuit for the scan impedance. The analysis is also extended to include the effect of a sufficiently thick grounded substrate that does not affect the elements’ current distribution and does not interact with the evanescent fields. Next, formulas for the ratio of intensity radiated toward each half-space for an interfacial array are provided. In a consecutive step, an asymptotic approximation is derived for the current distribution in arrays of arbitrary loaded dipoles, and the reactance of a dipole in the array environment is related to the inductance of a grid of wires. This model constitutes a useful tool to clearly identify the role of the different array variables (dipole dimensions, relative permittivity of the substrate, periodicity, end load, and scan angle in the principal planes) on the scan impedance by simple expressions and equivalent circuits. The model predictions are in good agreement with full-wave simulations and with previously published works.

Wideband Planar Phased Array Antenna Based on Artificial Magnetic Conductor Surface

A wideband planar dipole array based on artificial magnetic conductor (AMC) surface is presented for phased array applications. One wideband in-phase hexagonal AMC cell is realized firstly. An X-band planar dipole is modified by employing a detached H-shaped patch and four L-shaped stubs for impedance bandwidth enhancement. The active VSWR with different scanning angles and the radiation pattern of center element in small array are simulated. For demonstration, a prototype of 45° linearly polarized array with the elements of 4 × 32 is fabricated and measured. From the measurements, it can provide a stable gain over the entire scan range of ±45° within 8-11 GHz. Meanwhile, the difference of two orthogonal polarization components keeps less than 3.5 dB below 11 GHz as the beam scanning. It shows good performance in low-profile and low cost phased array antennas.

Planar Dipole Array Antenna Design for Mobile Robot Communications at 5.6 GHz

Mobile robot communications are important in mobile robot systems, especially robot teamwork. Reliable communications are important for data transmission and control. Beamforming can improve communications performance to improve system’s reliability. This paper proposed beamforming array antenna at 5.6 GHz with 4 planar dipole elements. These antennas are arranged on azimuth plane. We conduct computer simulation of antenna design and beamforming scenarios. Beamforming is made by controlling power and phase of each antennas. We found that the designed antenna is suitable for beamforming at azimuth plane. It is confirmed by computer simulation of phased array antenna. The antenna has 1.3538 GHz bandwidth and more than 6 dB main lobe magnitude.

All-Around Beam Switched Antenna With Dual Polarization for Drone Communications

This communication presents a drone-to-drone adaptive beam switched antenna with 360° beam coverage and dual polarizations. The proposed antenna maintains the all-around beam coverage with high directivity based on 16 concentric planar Yagi-Uda dipole array. The high gain dipole array beams are configured by eight vertical polarization elements and eight horizontal polarization elements with directors and reflectors. Depending on various communication environments, a single beam, multiple beams with identical polarization, or multiple beams with different polarizations can be adaptively controlled for highly reliable drone-to-drone communication. To ensure the compactness in the antenna array, 16 concentric planar antenna elements are arranged in an orthogonally crossed manner with optimized vertical and horizontal transition matching circuits. Each Yagi-Uda dipole element for vertical or horizontal polarization showed a measured peak gain of 6.35 and 6.40 dBi at 5.5 GHz, respectively. The proposed antenna was integrated with sub-6 GHz transceiver and microcontroller unit (MCU) to verify the switched beam performance with dual polarization. Also, the Tx and Rx operation at random beam conditions was tested by using two proposed antennas and showed an excellent performance from 5 to 6 GHz.

A Wideband Absorber of Load Dipoles on a Dielectric Substrate with Inductive Ground Plane

AbstractA planar array of dipoles with matched loads in air backed by a ground plane at a quarter wavelength would become an absorber with a −10‐dB bandwidth of about 10%. Obviously, if the air substrate behind the dipoles is replaced by a dielectric substrate, the physical thickness of the absorber, saying a quarter wavelength, can be reduced. Meanwhile, as the incident waves illuminate on the absorber, the reflections are mainly from three ways, which are the air‐dielectric interface, the back scattering of the loaded dipole as a receiving antenna, and the ground plane. This paper shows that with the combination of the three reflections and a suitable dielectric constant together with its dipole separations, the −10‐dB bandwidth of the absorber increases to 20% and beyond. To further decrease the thickness of the dipole‐based absorber, inductive ground plane is introduced to replace the normal ground; phase analyses of the dipole‐based absorber with inductive ground is also given to explain the feasibility of the proposed technique. Both simulations and measurement results show that, with the proposed technique above, not only the thickness of the dipole‐based absorber can be decreased from a quarter wavelength to less than fifth wavelength, but also the −10‐dB bandwidth of the reflection can be enhanced from 20% to 48% or so.

Synthesizing Uniform Amplitude Sparse Dipole Arrays With Shaped Patterns by Joint Optimization of Element Positions, Rotations and Phases

This paper presents a novel method for synthesizing sparse dipole arrays with shaped patterns by joint optimization of element positions, rotations and phases. Such joint optimization exploits maximum available degrees-of-freedom under the assumption of uniform amplitude excitations to improve the shaped power pattern synthesis performance, and it leads to a reduced number of elements and simpler feeding network without using unequal power dividers for the array. The copolarization (COP) and cross-polarization patterns for a rotated dipole array are derived in a 2-D case, and then the vectorial shaped pattern synthesis problem is formulated as finding the optimal solution by maximally approaching the desired COP pattern shape under multiple constraints on the sidelobe level (SLL) and cross-polarization level (XPL). In addition, an asymmetric mapping method is incorporated into the proposed joint optimization, so that the minimum element spacing constraint can be also used for the synthesis of planar sparse dipole arrays. The comprehensive learning particle swarm optimization (CLPSO) algorithm is adopted to optimize the element positions, rotation angles and phases. A set of synthesis experiments including linear and planar rotated dipole arrays with a different pattern shape requirements are conducted to validate the effectiveness and robustness of the proposed approach. Synthesis results show that the proposed approach can save about 17.24% – 55.86% elements as well as many unequal power dividers for test cases.

Gain-Enhanced Planar Log-Periodic Dipole Array Antenna Using Nonresonant Metamaterial

In this communication, a novel nonresonant metamaterial (MTM) structure is proposed to enhance the gain of the clamped-mode planar log-periodic dipole array (CMPLPDA) antenna fed by substrate integrated waveguide. The proposed MTM structures composed of a series of metallic semiring patches are printed on both sides of the antenna substrate, featuring low loss, broadband, and easy integration. Different arrangements of the nonresonant MTM with respect to the dipoles of the CMPLPDA antenna are investigated and compared. The proposed gain-enhanced method based on the nonresonant MTM has been studied through both numerical simulations and experiments. Compared to the original CMPLPDA antenna without any MTM inclusions, the proposed CMPLPDA antenna fully loaded with nonresonant MTM inclusions exhibits a gain enhancement of at least 1.6 dB (up to 4 dB at 27 GHz) within the operating band of 26–40 GHz in the simulations, which is also validated by the experiments.

Diffraction by a truncated planar array of dipoles:A Wiener–Hopf approach

We present a rigorous solution to the problem of scattering of a semi-infinite planar array of dipoles, i.e., infinite in one direction and semi-infinite in the other direction, thus presenting an edge truncation, when illuminated by a plane wave. Such an arrangement represents the canonical problem to investigate the diffraction occurring at the edge-truncation of a planar array. By applying the Wiener–Hopf technique to the Z-transformed system of equations derived from the electric field integral equation, we provide rigorous close form expressions for the dipoles’ currents. We find that such currents are represented as the superposition of the infinite array solution plus a perturbation, which comprises both edge diffraction and bound surface waves excited by the edge truncation. Furthermore, we provide an analytical approximation for the double-infinite sum involved in the calculation which drastically reduces the computational effort of this approach and also provides physically-meaningful asymptotics for the diffracted currents.

Spherical Equivalent Dipole Array Theory and Its Applications to Complex Electromagnetic System

The equivalent dipole array is an effective method for emission source modeling to solve practical electromagnetic engineering problems. In this paper, a spherical equivalent dipole array method (SEDAM) is proposed to model practical and complex electronic systems. Unlike the planar equivalent dipole array method (PEDAM), SEDAM is derived in the spherical coordinate system and is more suitable for large electromagnetic equipments. In addition, SEDAM can achieve accurate emission prediction around electronic systems of arbitrary structures, where PEDAM is not easy to be used. We first derived the analytical relationship between magnetic fields and magnetic dipole moments in the spherical coordinate system. To model the complex systems, several equivalent dipoles are properly placed on a spherical surface which encloses the equipment under test (EUT). By superposition of the fields generated by all the equivalent dipoles, the equivalent relational matrix is constructed and the weights for each dipole are solved. Then, the weighted dipole array can be used to predict the emission fields at desired locations. The proposed method is first verified through a numerical simulation. The results show that the proposed SEDAM outperforms the PEDAM in terms of accuracy. It is further validated through a measurement. The measurement results show that SEDAM can model the practical and complex electronic systems and predict their electromagnetic emission with acceptable accuracy.

A Planar Dipole Array Surface for Electromagnetic Energy Harvesting and Wireless Power Transfer

We present a design of an electromagnetic energy harvesting surface inspired by an array of printed metallic dipolar elements. The unit cell of the proposed harvester is based on two printed asymmetric off-center fed dipoles. As a proof of concept, a finite array of $9 \times 3$ unit cells was analyzed numerically and experimentally. The array was first analyzed for maximizing radiation to ac absorption where each dipole was terminated by a resistor across its gap. For dc conversion, the resistors were the replaced by Schottky diodes. The simulation results show radiation to ac harvesting efficiency of 99%. An overall radiation to dc harvesting efficiency of 76% was obtained experimentally, which, to the best of the authors’ knowledge, exceeds the performance of all previous energy harvesting surfaces. Another critical feature of the proposed designs is enhancing the power per diode in order to maximize its turn-ON time.

Broadband Planar Log-Periodic Dipole Array Antenna Based RF-Energy Harvesting System

ABSTRACT In this paper, a low-cost planar log periodic dipole array antenna has been described using triangular dipole elements for broadband RF energy harvesting applications. The antenna measured bandwidth for VSWR ≤ 2 is from 570 to 2750 MHz (1:4.8), which covers all the cellular bands. The radiation pattern is uniform over the entire frequency range. The measured gain is 7.2 dBi with less than ±0.5 dB variation over the entire bandwidth. A Schottky diode-based voltage doubler rectifier is used to convert RF energy to DC voltage. A broadband impedance matching network using an exponentially tapered microstrip line between log periodic antenna and rectifier has been designed. At a distance of 25 m from the cell tower, a voltage of 1.7 V was obtained using the developed broadband RF energy harvesting system across a load of 4.7 kΩ. A voltage of 3 V was obtained across the same load while initiating a call from a cell phone.

Compact log‐periodic dipole array antenna with bandwidth‐enhancement techniques for the low frequency band

A compact planar log-periodic dipole array (LPDA) antenna operating from 0.55 to 9GHz with high measured gain is proposed to be implemented in a reverberation chamber as a source antenna. To minimise the total size of the LPDA antenna, variants of top-loading techniques are utilised, and a much smaller spacing factor is opted to specify the spacing between the elements. However, miniaturisation of the LPDA antenna limits the antenna's wideband characteristics over the desired range of frequencies. Hence, a feedline meander and a trapezoidal stub are incorporated into the design as impedance matching techniques to effectively enhance the bandwidth performance especially for the lower band of the antenna's operating frequency range. The LPDA antenna exhibits radiation patterns with and without a radome having the measured gain ranging from 2.48 to 7.89 dBi and from −1.20 to 7.94 dBi, respectively.

항공기 탑재용 경량화 지지 구조를 갖는 평면 LPDA 안테나 설계

본 논문에서는 항공기 탑재용 경량화 지지 구조를 갖는 평면 LPDA(Log-Periodic Dipole Array) 안테나를 제안한다. 제안된 안테나는 항공기 탑재에 적합하도록 가볍고, 구조적 진동에 견딜 수 있는 평면형 골격 지지 구조를 적용하여 설계하였다. 평면형 골격 지지 구조의 재질은 강도와 온도 특성이 우수한 Peek(Polyether ether ketone)를 사용하였으며, 제안된 안테나는 지지 구조 양면에 LPDA 안테나 방사소자를 결합하여 제작되었다. 지지 구조 유전체로 인하여 변화된 입력 임피던스는 일부 방사소자 간격과 길이를 조절하여 매칭시켰다. 설계된 평면 LPDA 안테나의 10-dB 반사손실 대역폭은 시뮬레이션 및 측정 결과, 각각 0.4~3.1 GHz(7.3:1), 0.41~3.5 GHz(8.2:1)로 광대역이었다. 평균 이득은 0.5~3 GHz 대역내에서 시뮬레이션은 평균 6.77 dBi, 측정은 6.55 dBi이었다. 따라서 설계된 안테나는 가볍고 견고한 구조와 광대역 지향성 방사특성을 가져 항공기 탑재 용도로 적합함을 확인하였다. This paper proposes a planar Log-Periodic Dipole Array(LPDA) antenna with light-weight supporting structure for installing on an aircraft. The proposed antenna is designed by applying a planar skeleton supporting structure that has light-weight for an aircraft and is capable of withstanding structural vibration. The material of the planar skeleton supporting structure is a Polyether ether ketone(Peek) which has excellent characteristics on strength and temperature. The proposed antenna is fabricated by attaching the radiating elements of the LPDA on both sides of the supporting structure. The changed input impedance due to the dielectric material of the supporting structure was compensated for by controlling the distance and length of several radiating elements. The 10-dB return loss bandwidths of the designed planar LPDA antenna with light-weight supporting structure are obtained as 0.4~3.1 GHz(7.3:1) in the simulation and 0.41~3.5 GHz(8.2:1) in the measurement. The average gains in 0.5~3 GHz band are 6.77 dBi in the simulation and 6.55 dBi in the measurement. Therefore, we confirm that the designed antenna is appropriate to be installed on an aircraft due to its light-weight structure and wideband directional radiation characteristics.

Broadband planar dipole array Antenna with double C-shaped slit elements for digital TV broadcasting transmission

This research has proposed a planar rectangular dipole antenna enclosed in double C-shaped parasitically slit elements (i.e., radiator element) on a double-cornered reflector for bandwidth enhancement. In the study, simulations were first carried out to determine the optimal parameters of the radiator element and then a radiator element prototype was fabricated and mounted onto a double-cornered aluminum reflector. The simulated and measured |S11|<–10 dB of the antenna element covered the frequency ranges of 451–901 MHz (66.6%) and 455–886 MHz (64.3%), respectively. The gain was enhanced by the subsequent deployment of multiple radiator elements to fabricate a four-element vertically array antenna on an elongated double-cornered reflector. The simulated and measured |S11|<−10 dB of the array antenna, respectively, covered the 410–991 MHz (82.9%) and 415–886 MHz (72.4%) frequency ranges. The proposed array antenna radiates unidirectionally across the DTV frequency band with a measured front-to-back ratio and cross polarization >20 and <−23 dB, respectively. The simulated and measured half-power beam widths in the E and H planes were respectively 56° ± 13° and 20° ± 6°; and 57° ± 13° and 21° ± 6°. In addition, the simulated and measured gains of the array antenna were 12.8–16.4 dBi and 11.3–15.8 dBi along the 470–862 MHz frequency range. This proposed array antenna is thus suitable for DTV broadcasting transmission. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:466–478, 2016.

Multi-Objective Synthesis of Filtering Dipole Array Based on Tuning-Space Mapping

In the paper, we apply tuning-space mapping to multi-objective synthesis of a filtering antenna. The an- tenna is going to be implemented as a planar dipole array with serial feeding. Thanks to the multi-objective approach, we can deal with conflicting requirements on gain, imped- ance matching, side-lobe level, and main-lobe direction. MOSOMA algorithm is applied to compute Pareto front of optimal solutions by changing lengths of dipoles and pa- rameters of transmission lines connecting them into a se- rial array. Exploitation of tuning space mapping signifi- cantly reduces CPU-time demands of the multi-objective synthesis: a coarse optimization evaluates objectives using a wire model of the filtering array (4NEC2, method of moments), and a fine optimization exploits a realistic pla- nar model of the array (CST Microwave Studio, finite inte- gration technique). The synthesized filtering antenna was manufactured, and its parameters were measured to be compared with objectives. The number of dipoles in the array is shown to influence the match of measured param- eters and objectives.

Equilibrium states of planar arrays of magnetic dipoles with allowance for exchange interaction

Equilibrium states of planar square arrays of magnetic dipoles have been studied. It has been shown that, in the presence of exchange interaction, the main equilibrium states are configurations with the orientation of dipoles along the diagonal of the system, along its side, and vortex configurations with different location of the center of the vortex and different magnitudes of the magnetic moment of the system. Conditions for transitions between equilibrium configurations caused by the planar field that acts on the entire array and by the local normal field acting on part of dipoles entering into the system have been considered. The possibility of transitions between the configurations has been shown and the changes in the total magnetic moment due to the action of the field on separate dipoles of the system has been discussed.

Equilibrium state of planar arrays of magnetic dipoles in the presence of exchange interaction

This article investigates the equilibrium states of square-planar arrays of magnetic dipoles. It has been demonstrated that in the presence of an exchange interaction the main equilibrium states are the configurations of dipoles oriented along the system diagonal, along its side, as well as configurations with vortex structures, which may differ by location of the vortex center and, respectively, by magnitude and direction of the magnetic moment of the system. Also the conditions for transitions in the equilibrium configurations, when influenced by a plane field affecting the whole array, or by a normal local field affecting a part of the system dipoles, were considered. The possibility to control magnetic moment of the dipoles system through transitions between different vortex configurations, including a configuration with zero total magnetic moment, has been shown.

Ultra‐wideband planar LPDA antenna with mode converter balun

A new balun used for feeding a planar log-periodic dipole array antenna (PLPDA) is proposed. This balun, which is based on mode conversion, converts gradually the transmission mode from quasi- TEM (coaxial cable) to full TEM (balanced line), with an accessible excitation current property (ECP), which is not achievable in classical feeding techniques (infinite or self balun). To validate this approach, an ultra-wideband (UWB) PLPDA antenna was designed with these balun structures for operating in the L and S bands (1-4 GHz) and the results were compared in terms of reflection coefficient and radiation pattern. A PLPDA antenna with a mode converter balun was fabricated. Results show that the proposed balun is a low length (10 mm) frequency-independent (4.5 GHz based on |S11|<-10 dB) device useful for feeding the UWB PLPDA antenna. Moreover, antenna's ECP can be modified, which is necessary for phase centre variation compensation.