Two-element Array Research Articles

A dual-band dipole array antenna with fan-beam radiation for biomedical and telecommunications applications

This study introduces a new technique for achieving dual-band functionality in a printed dipole antenna with integrated balun feeding without additional elements. By employing an optimization algorithm, the fundamental parameters of the antenna are extracted, resulting in an antenna design that operates effectively in two distinct frequency bands of 2.4–2.5 and 5–6 GHz for WLAN/ISM and biomedical applications. By implementing the proposed design in a two-element array structure, the antenna successfully achieved a fan-beam radiation pattern in both frequencies. The array antenna exhibits fan-beam radiation patterns and peak gains of 6.90 dB and 7.84 dB, respectively, in two frequency bands: 2.06–2.52 GHz and 5.09–5.93 GHz. According to the proposed design, the array antenna has measured half-power beamwidths (HPBWs) of 38.34° and 25.14° in the two frequencies specified. The overall dimensions of the antenna are 1.100λ × 0.563λ × 0.004λ. This research design offers advantages such as smaller dimensions, higher gain, and a more straightforward structure compared to dual-band array antennas with fan beam radiation patterns.

High isolation MIMO antenna array for multiband terahertz applications

The advancement of future technology seeks to create wireless systems capable of achieving faster data transfer rates. One solution to confront this challenge is by employing Multiple-Input Multiple-Output (MIMO) systems. Nonetheless, the primary obstacle in assessing MIMO performance revolves around the size and spacing of the antennas to maintain isolation among the ports. Consequently, it is essential to devise an approach to tackle these challenges, with the utilization of a DGS as a viable and promising approach. Hence, in this study, we developed a dual-frequency MIMO system featuring two linear array antennas with two elements each and configured to function at 128 GHz and 178 GHz. Initially, this design is conceived as a single-element structure before evolving into a two-element MIMO antenna array configuration. The antenna's physical dimensions are 2.7 × 3.65 × 0.15 mm3, and it consists of two linear array nodes positioned at a separation distance of 0.18 mm. Additionally, the antenna delivers peak gains of 5.16 dB and 6.24 dB at frequencies of 128 GHz and 178 GHz, respectively. The values of various MIMO performance indicators meet stringent standards with ECC values below 0.012 and a DG of approximately 10 dB. Furthermore, the TARC remains below 0 dB. The aim of this research is to create a novel design for a THz antenna that can achieve a wide bandwidth and a high gain while maintaining the standard compact antenna size necessary for THz applications.

Highly isolated pin-loaded millimeter wave MIMO antenna array system for IoT-based smart environments

The Internet of Things (IoT) based wireless devices are mainly designed for rapid indoor millimeter-wave (mmW) communication systems. These systems often require high gain mmW antennas within a wideband MIMO framework. This work presents a high performance quad element pin-loaded multiple-input multiple-output (MIMO) antenna array for mmW communications that can be utilized within IoT-enabled smart environment. The novelty of these antenna elements lies in the incorporation of unique flower-shaped slots and shorting pins in each patch of a two-element antenna array. Moreover, a four-port MIMO antenna system is created by arranging the two element arrays in an orthogonal configuration. By employing this pattern diversity technique and incorporating shorting pins in each individual element, the adverse mutual coupling effects between adjacent elements are effectively mitigated. Experimental validation of the MIMO array prototype confirms the minimum isolation of 34 dB and high port isolation of 72 dB over the operating bandwidth from 26.31–30.25 GHz (3.96 GHz). Notably, these features together with lower correlation values and higher diversity gain, make it a good choice for mmW-based IoT devices in smart environments.

Metasurface-based dual-sense circularly polarized antenna for MIMO/full-duplex applications.

This paper introduces a two-element antenna array with dual-sense circular polarization, wideband operation, and high isolation characteristics. The antenna consists of two conventional truncated corner patches and an extra layer of metasurface (MS) located above the radiating patches. The overall dimensions of the proposed antenna are 0.92 λ0 × 0.73 λ0 × 0.05 λ0 and the element spacings are 0.02 λ0 and 0.39 λ0 with respect to edge-to-edge and center-to-center spacings. For validation, measurements on a fabricated antenna prototype are carried out. The measured data demonstrate that the presented MS-based antenna has a wide operating bandwidth of 14.5% with high isolation of better than 26 dB. The excellent performance could be concluded from the results of the investigation, which indicates that the proposed MS-based antenna could be a good candidate for multiple-input multiple-output (MIMO) and full-duplex applications.

Planar array antenna coupled InGaAs/InAlAs multi-quantum well optical modulator for 60 GHz band millimeter wave signals

A Fe-InP-based planar array antenna-coupled InGaAs/InAlAs multiple quantum well (MQW) optical phase modulator is proposed and demonstrated for radio over fiber (RoF) applications with 60 GHz-band millimeter-wave wireless signals. The modulator comprises five types of five-layer asymmetric coupled quantum wells (FACQWs) and a two-element array antenna. The FACQWs are designed to have a significant electric-field-induced refractive index change with small electric fields induced in the antenna. In the fabricated modulator, a carrier-to-sideband ratio (CSR) of up to 45.9 dB was successfully obtained at a power density of 11 W/m2, corresponding to a phase shift of 10.1 mrad. Furthermore, data transmission of a 2 GHz modulated wave with a 60 GHz wireless carrier wave was demonstrated.

Mutual coupling reduction of a two-port MIMO antenna using defected ground structure

In response to the escalating demand for high data rates and the expanding user base, multiple input multiple output (MIMO) technology has recently become of paramount importance in addressing the imperative for high-capacity communication systems aligned with emerging standards. In this paper, a single antenna element that achieves a wideband frequency coverage by adjusting the slots ‘dimensions and a satisfactory gain of 6.4 dBi is presented. To enhance the antenna's gain and capabilities, we introduced a MIMO antenna designed to operate within the frequency range of 36.8 to 40.9 GHz. The proposed MIMO antenna configuration consists of two-element arrays etched on a compact 25.94×26.76×1.3 mm³ Rogers RT/duroid 5880 substrate. While maintaining the operational band and enhancing gain, a critical challenge involving inadequate isolation between the two antenna elements is encountered due to the confined area. To effectively tackle this issue, a parametric study on the inter element distance between antennas is conducted and Defected Ground Structure (DGS) is implemented. This refinement results in a substantial 3.6 dB enhancement in isolation, which is found to be lower than -31 dB, a notable improvement in impedance matching, and a remarkable high gain of approximately 7.7 dBi is achieved. Besides, the analysis of the MIMO metrics demonstrates that they consistently fall within acceptable ranges, with the antenna showcasing an envelope correlation coefficient of approximately 0.005 and a commendable diversity gain of around 9.99 dB. The proposed antenna's combined attributes, including its compact, simple, and low-profile design, position it as a highly promising choice for 5 G communication system and future miniature devices intended for Internet of Things (IoT) applications.

Design and Simulation of a High Performance 5G mm-Wave MIMO Antenna Array for Mobile Applications

This paper presents the design and simulation of an efficient multiple input multiple output (MIMO) antenna array for 5G millimeter-wave (mm-wave) mobile applications. With a dielectric constant of 2.2 and a loss tangent of 0.0009, the substrate employed is a Rogers RT5880 that is 0.254 mm thick. The 37 GHz frequency spectrum, reserved for millimeter-wave mobile applications for 5G, is covered by the proposed MIMO antenna arrays. The single antenna element has a gain of 6.44 dBi, which is increased to 7.89 dBi with a two-element array configuration and 10.88 dBi with a four-element array configuration. The proposed MIMO antenna array performance metrics—including reflection coefficient, VSWR, radiation efficiency, and gain—are seen and discovered to be below the accepted threshold. In the desired operating frequency band, it is noticed that more than 85% of the proposed MIMO antenna array's radiation efficiency is achieved. According to simulation findings, the proposed design may be potentially feasible for mobile applications using millimeter waves in the 5G network.

Способ построения двухэлементной цифровой антенной решетки для оценки угловых координат радиосигналов со сверхразрешением с повышенной точностью на основе нижней границы Крамер-Рао

In the paper an effective method for optimal placement of directional antenna elements for digital spatial signal estimation is discussed. The digital antenna array evaluates spatial coordinates with the subsequent beamforming. However, as it is well known, the relative position of antenna elements, their number and the shape of the radiation pattern have a significant impact on the quality of the spatial pseudospectrum. The paper uses the previously obtained expression for estimating the Cramer-Rao lower bound to reduce the number of antenna elements without losing the accuracy of direction-of-arrival estimation of the signals. For example, a two-element array is obtained. The elements have a flat-top radiation pattern. It is shown that the accuracy of the MUSIC method in the obtained array is higher or comparable to the array composed of three elements.

Investigation of mutual coupling coefficients in dual-polarized antenna arrays

Background. Antenna arrays are widely used in various fields of radio engineering, such as radio and telecommunications, satellite communication systems, etc. One of the important characteristics of an antenna array is its radiation pattern. The estimation of impedance matrices, scattering matrices, and partial radiation patterns is usually performed based on the results of numerical electrodynamic modelling. In the case of a large number of antenna elements, such modelling and optimization of the array requires significant time.
 Aim. To investigate the mutual coupling between dual- polarised antenna elements included in a linear antenna array.
 Methods. Modelling of antenna arrays based on cross-dipole elements was performed using methods of electrodynamic modelling software. The study of the mutual coupling of antenna elements in the antenna array and verification of the developed mathematical model were carried out by numerical methods.
 Results. A physical interpretation of that there is no almost interaction between the elements operating in orthogonal polarizations, and the coefficients of mutual coupling decrease with increasing distance between antenna elements is given. Proposed a simplified model of mutual coupling, which reduces the computational complexity of the problem of determining the mutual coupling matrices.
 Conclusion. It is developed a mathematical technique that allows to calculate the characteristics of antenna arrays with a large number of antenna elements, meanwhile electrodynamic modelling is carried out only for an isolated antenna element and a two-element array.

A Decoupling Technique for Beamforming Antenna Arrays Using Simple Guard Trace Structures

This paper discusses decoupling techniques for suppressing electromagnetic coupling between elements of beamforming antenna arrays. Guard trace structures, which are commonly used for crosstalk reduction on printed circuit board technology, are proposed to be inserted between the array elements for coupling reduction. Two types of guard trace structures, i.e., straight guard traces and serpentine guard traces, were explored, and the effect of using via holes on both types of guard traces was studied. For this purpose, two-element antenna arrays with guard trace structures inserted between array elements were designed and simulated. The simulation results showed that a straight guard trace with vias (straight GTV) and a serpentine guard trace without vias (serpentine GT) could effectively reduce EM coupling between elements of array antennas. To verify the simulation results, prototypes of antenna arrays with straight GTV and serpentine GT were realized and measured. The measurement results showed coupling reductions of 5 dB and 6.4 dB could be achieved when straight GTV and serpentine GT are inserted between two array elements separated by edge-to-edge distances of 4 mm and 9.05 mm, respectively. Therefore, the proposed decoupling technique is suitable for beamforming antenna arrays with a very close distance between array elements.

Boiling Histotripsy Using Dual-Frequency Protocol on Murine Breast Tumor Model and Promotes Immune Activation.

Histotripsy is an ultrasound-guided, noninvasive, nonthermal ablation therapy that can mechanically lyse target tissues. There have been no reports of enhanced histotripsy for large-volume triple-negative breast cancer (TNBC). This study aims to verify the ability of a novel approach of dual-frequency mode combined with two-stage millisecond-length ultrasound pulses (DF-TS) to accelerate the treatment of murine subcutaneous 4T1 tumors and determine immune changes after treatment. A custom-designed 1.1-/2.2-MHz two-element confocal-annular array was used to treat approximately 6-mm tumors under ultrasound guidance and real-time monitoring. Two-stage millisecond-length ultrasound pulses were used to generate approximate cuboid ablation volumes (diagonal 5-6 mm) within each tumor, with a dose of 100 pulses/point. Immune effects were characterized by changes of pro-inflammatory cytokine levels and infiltration levels of immune cells. In all targeted treatment areas, bubble cloud activity was visualized by ultrasound monitoring. The novel protocol resulted in elliptical and controllable sized lesions, reducing the number of scanning points, and was generally well tolerated. After treatment, tumor growth experienced a seven-day stagnation period, the survival period of mice was prolonged, and the levels of pro-inflammatory cytokines and immune cell infiltration increased. This study demonstrates that DF-TS boiling histotripsy (BH) has a noninvasive, efficient, and precise ablation ability for TNBC and potentially enhances immune responses.

Response Surface Modeling of the Steady-State Impedance Responses of Gas Sensor Arrays Comprising Functionalized Carbon Nanotubes to Detect Ozone and Nitrogen Dioxide.

Carbon nanotube (CNT) sensors provide a versatile chemical platform for ambient monitoring of ozone (O3) and nitrogen dioxide (NO2), two important airborne pollutants known to cause acute respiratory and cardiovascular health problems. CNTs have shown great potential for use as sensing layers due to their unique properties, including high surface to volume ratio, numerous active sites and crystal facets with high surface reactivity, and high thermal and electrical conductivity. With operational advantages such as compactness, low-power operation, and easy integration with electronics devices, nanotechnology is expected to have a significant impact on portable low-cost environmental sensors. Enhanced sensitivity is feasible by functionalizing the CNTs with polymers, metals, and metal oxides. This paper focuses on the design and performance of a two-element array of O3 and NO2 sensors comprising single-walled CNTs functionalized by covalent modification with organic functional groups. Unlike the conventional chemiresistor in which the change in DC resistance across the sensor terminals is measured, we characterize the sensor array response by measuring both the magnitude and phase of the AC impedance. Multivariate response provides higher degrees of freedom in sensor array data processing. The complex impedance of each sensor is measured at 5 kHz in a controlled gas-flow chamber using gas mixtures with O3 in the 60-120 ppb range and NO2 between 20 and 80 ppb. The measured data reveal response change in the 26-36% range for the O3 sensor and 5-31% for the NO2 sensor. Multivariate optimization is used to fit the laboratory measurements to a response surface mathematical model, from which sensitivity and selectivity are calculated. The ozone sensor exhibits high sensitivity (e.g., 5 to 6 MΩ/ppb for the impedance magnitude) and high selectivity (0.8 to 0.9) for interferent (NO2) levels below 30 ppb. However, the NO2 sensor is not selective.

Design of a Compact Microstrip Decoupled Array

A one-dimensional mono-pulse microstrip antenna plays an important role in target detection, tracking, recognition and imaging. However, feeding and coupling are the main reasons for the large size of the mono-pulse antenna, which is not conducive to miniaturization and integration. A miniaturized mono-pulse antenna is proposed to reduce the size and improve the integration in antenna design. The proposed antenna has a more compact size and good isolation, with a well-maintained radiation pattern and zero depth. The antenna unit size is 0.19 λ0 × 0.19 λ0 × 0.006 λ0. The overall antenna size is 78 mm × 78 mm × 1.48 mm (0.63 λ0 × 0.63 λ0 × 0.0012 λ0). In this communication, a general decoupling feeding network for two-element microstrip array antennas is also designed. Experiment validations confirm that the operating frequency of the designed antenna system is at 2.45 GHz with a gain of 5.54 dBi. The return loss of the sum and difference ports is 16.14 dB and 15.2 dB, respectively. The isolation of the ports is 36.6 dB. The proposed miniaturized mono-pulse antenna is approximately 64% smaller in size compared to previous versions.

Wide band and high gain microstrip antenna using planar series array 4×2 element for 5G communication system

The 5G communication system requires an antenna as a receiving device that has high performance including wide bandwidth and high gain. Microstrip antennas have advantages such as low cost, suitable for high frequencies and easy to integrate with other devices. One of the disadvantages of microstrip antennas is their narrow bandwidth and low gain. Therefore, microstrip antennas with wide bandwidth and high gain are especially needed to support 5G communication systems. This paper provides a solution by proposed a wide bandwidth and high gain microstrip antenna operating at a resonant frequency of 3.5 GHz for a 5G communication system. The proposed antenna was developed in four stages starting from a single element, a two-element series array, a 4-element series array and a 4×2-element planar series array. A series planar array technique is proposed to increase the gain and bandwidth of the microstrip antenna simultaneously. In this paper, simulations and measurements from the proposed antenna are displayed and compared comprehensively to show the performance improvement from each stage of the development of the proposed model. Based on the measurement results, the designed antenna has an impedance bandwidth (IBW) of 0.6 GHz and fractional bandwidth (FBW) of 17.14 % with a frequency range of 3.11–3.71 GHz and maximum gain of 12.2 dB at a resonant frequency of 3.5 GHz. The bandwidth and gain of the antennas increased by 205 % and 99.03 % compared to single element antennas, respectively. Therefore, the proposed antenna can be recommended to be used as a receiving antenna for 5G communication systems

Investigation of Planar Isolators for Mutual Coupling Reduction in Two-Dimensional Microstrip Antenna Arrays

The design of isolators to reduce mutual coupling in large two-dimensional antenna arrays is complex and requires significant computational effort. This work attempts to alleviate this problem by applying different types of planar isolators in different orientations and experimenting first with two-element microstrip antenna arrays. A U-shaped planar transmission line isolator, a U-shaped planar transmission line-based destructive ground structure, and a planar neutralization line structure are designed to reduce E-plane or H-plane coupling in two-element microstrip antenna arrays. A mutual coupling reduction of approximately 6 dB is achieved. Four combinations of these planar isolators are compared and analyzed in a four-element microstrip antenna array. An optimal combination is then obtained by using two reversely placed U-shaped line isolators, which reduce the mutual coupling by more than 6.1 dB. The study is also extended to a 5 × 5 antenna array. Similar results of mutual coupling reduction are obtained. In addition to simulation, both two-element and 25-element microstrip antennas have been constructed and tested. The agreement of the simulation results with the measured results confirms the effectiveness of the decoupling structures.

A Millimeter-Wave Antipodal Linearly Tapered Slot Antenna Array for 5G Wireless Communication

This paper presents an antipodal linearly tapered slot antenna (ALTSA) array with the newly emerging substrate-integrated coaxial line (SICL) technology. Each element of the proposed array consists of two vertically stacked antipodal tapered slot antennas (TSA) with the inner conductor of a SICL as the shared fin. The vertical symmetry of this radiating element structure significantly suppresses the cross-polarization level. By employing a SICL-based power splitter with differential outputs, a two-element array with horizontal symmetry is formed. With the inner conductors of two parallel SICLs combined as the flaring metal shared by adjacent tapered slots, the main beam squint is effectively suppressed. Experimental results show an actual −10-dB impedance bandwidth (BW) of 24.5∼34.4 GHz, and the realized gain range measured is 16.1∼18.7 dBi. The cross-polarization levels are −39.4 dB/−40.7 dB at 30 GHz for the E-/H-planes. The measured results agree well with the simulated data which demonstrates the feasibility of the proposed SICL-based ALTSA scheme in the potential 5 G·millimeter-wave (mmWave) applications.

Superdirective Unidirectional Mixed-Multipole Antennas: Designs, Analysis, and Simulations

Highly directive antenna systems that will address the needs of space-limited Internet-of-Things devices and their NextG applications are in demand. Compact high-frequency high-directivity alternatives to complex, power hungry phased arrays are desired. Several compact, unidirectional mixed-multipole antennas (UMMAs) based upon mixtures of primarily dipoles and quadrupoles are reported. The simulated performance characteristics of these 28 GHz near-field resonant parasitic (NFRP) antennas, notably their large peak directivities and front-to-back ratios, are presented; they are all demonstrated to be superdirective while having attractive radiation efficiencies. Uniform endfire arrays of active closely-spaced equal-length idealized wire dipoles are exemplified as reference cases. The Rayleigh quotient (RQ) method typically used to determine their amplitude coefficients is extended for the first time to achieve unidirectional versions. Comparisons between these unconstrained and constrained RQ-designed arrays are made. While the performance characteristics of the single-source broadside-radiating UMMAs approach those of the reference arrays, a direct comparison of a realizable UMMA with the analogous unequal-length, non-uniformly-spaced idealized dipole array demonstrates its superiority. A two-element UMMA array that is scalable to a larger number of elements is also presented and shown to be superdirective, illustrating that the attractive properties of its individual elements are maintained even when mutual coupling occurs.

Speech enhancement using dual microphone adaptive noise canceller

Subject of research. The subject of the study is the issue of rational placement of microphones of the main and reference channels of a two-channel adaptive noise canceller (ANC) for speech enhancement in presence of acoustic interference from a point source. An increase of the signal-to-noise ratio (SNR) at the output of the ANC relative to the input value of the main channel was chosen as a criterion for rational placement. The limitations of the model of direct propagation of signals in reverberation conditions are considered. Methods. The estimation of the SNR at the inputs of the main and reference channels is obtained on the basis of a geometric model of point sources of signal and interference and on the analytical expressions for transfer functions between signal and interference sources and microphones of the main and reference channels for a planar model of signal propagation in a free field. The main results. The conditions for microphones placement of dual channel ANC, increasing SNR, are determined. The conditions for reference channel microphone placement at a given position of main channel microphone are determined. Limitations of ANC efficiency under reverberation conditions are investigated. It is shown that the microphone of the reference channel should be located near the interference source. For large rooms, the use of dual-microphone arrays is proposed and possible signal processing algorithms (conditions of their application) are considered. To use a two-element microphone array, additional information about the position of the target source is required. Practical significance. The obtained results can be useful for distant speech acquisition in the presence of acoustic interference.

Self-Decoupled Dual-Frequency Patch Antennas via Hybrid Coupling Interface Technique

This letter presents a novel hybrid coupling interface (HCI) technique to achieve self-decoupling between two dual-frequency patch antennas (DFPAs) for the first time, with no need to introduce external structures. To this end, a decoupling condition based on a detailed network analysis indicates the key to realizing self-decoupling at two operating frequencies simultaneously is that the DFPA must have two independent CIs, which is different from the single-band self-decoupling achieved by using mixed coupling in a single CI. Then, an actual DFPA with HCI, composed of a rectangular patch and a short-circuited <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> /4 microstrip resonator, is proposed and constructed in a two-element array with another one, which demonstrates that decoupling can be realized by adjusting the radius of the shorting pin conveniently. Finally, experimental results show that the in-band isolation between two antennas can be enhanced beyond 15 dB across two operating frequency ranges of 3.77 ∼ 3.94 GHz (4.4%) and 4.59 ∼ 4.72 GHz (2.8%).

Design of Frequency Scanning Coupled-Resonator Two-Element Array Antenna

In this brief, we present one type of frequency scanning coupled-resonator two-element array antenna and its corresponding equivalent circuit synthesis method. This antenna consists of several series-coupled resonators, the non-radiating resonators are cascaded between two radiating resonators. Since the antenna only has resonators and coupling structures, the threeports coupled-resonator circuit model can be used to explain the working principle and predict the performance of this antenna. The analysis of circuits with different orders indicates that the fractional bandwidth can control the scanning rate and the scanning rate and range can be both affected by the number of non-radiating resonators. Finally, two antennas with three and four resonators are designed in PCB form to validate the method. The third-order (fourth-order) antenna can scan 54.1∘ (64∘) in a 5.87% (5.54%) bandwidth centered at about 3.5 GHz.