Adjacent Antennas Research Articles

Research on methods to enhance the survivability of AWACS with FDA against anti‐ARMs on a battlefield

AbstractThe Airborne Warning and Control System (AWACS) are pivotal assets in aerial operations, necessitating specialised protection measures, and serving as prime targets for enemy anti‐radiation missiles (ARMs). This paper explores approaches to enhance the battlefield survivability of frequency diverse array AWACS (FDA‐AWACS) by incorporating airborne radar technology onto the platform. The study commences by analysing the typical operational methods of anti‐radiation missiles. Following this, a deception model is formulated for the frequency diverse array (FDA) against the passive radar homing head of anti‐radiation missiles utilising the adjacent antenna single‐pulse amplitude‐comparison direction‐finding technique. Expanding on this groundwork, the research further assesses the deceptive impacts of FDA‐AWACS on direction finding cross‐location techniques. Simulation results validate that FDA‐AWACS can effectively counter the threat of anti‐radiation missiles by diminishing their direction‐finding and positioning systems.

A Sub-6 GHz 8 × 8 MIMO Antenna Array for 5G Metal-Frame Mobile Phone Applications

This article introduces a broadband sub-6 GHz 8 × 8 MIMO (multi-input multi-output) antenna array for 5G (fifth-generation) metal-frame mobile phone applications. The unique advantage of this compact antenna design is its placement in the corners of the mobile phone, allowing for significant PCB board space reduction. The proposed antenna’s 6 dB impedance bandwidth ranged from 3.3 to 6 GHz, covering the n77/78/79 and WiFi-5GHz bands. The main radiating element was an open-slot antenna coupled by a T-shaped structure connected to a 50-Ω transmission line. The size of the single-antenna element was 12.25 mm × 2.5 mm × 7 mm, and these antennas were symmetrical at four corners of the smartphone. A wide slot and neutral line were incorporated to reduce mutual coupling between adjacent antennas. The MIMO antenna array achieved isolation above 12 dB. The peak realized gain ranged from 2 to 5.28 dBi, and the total efficiency spanned 37% to 71%. The ECC (envelope correlation coefficient) was less than 0.34, and the CC (channel capacity) ranged from 33 and 41 bps/Hz.

Design of a compact quad-port wideband printed MIMO antenna for vehicular communication environment

ABSTRACT A wideband quad-port Multiple Input Multiple Output (MIMO) antenna with efficient isolation characteristics for 5 G New Radio (5 G-NR) applications is presented. The proposed antenna works in the span of 3–6 GHz frequency covering the n77/n78/n79 bands also covering the 5 G-V2X band (3300–5000 MHz), LTE-46 band (5150–5925 MHz) and Dedicated Short Range Communication (DSRC) at 5.9 GHz band. The single element of the MIMO antenna structure is modelled by an elliptical structure stacked on a rectangular patch along with the feedline on the conducting plane. The ground plane is modelled as a rhombic design providing a Defected Ground Structure (DGS) to provide the resonance at the desired frequency band. Later, the antenna is evolved as a four-element MIMO system by arranging the antenna elements orthogonal to each other with a distance of separation between the adjacent antenna elements considered to be 10 mm. The all-inclusive dimension of the proposed antenna is 65 × 65 mm2. The simulated MIMO structure is fabricated and measured for antenna parameters and MIMO parameters such as isolation characteristics and MIMO diversity performances. The simulated values are obtained at acceptable limits with the measured values for the proposed wideband frequency range of operation. The compact, wideband antenna is found to be suitable for various 5 G-NR applications, especially Wi-Fi-assisted Vehicular Communication in the sub-6 GHz frequency range.

Design of Broadband Phased Array Feed Using Stereolithographic Additive Manufacturing Heterogeneous Integrating Technology for Fast Radio Burst Observation

Herein, a stereolithography appearance 3‐D printed phased array feed (PAF) on radio telescopes based on broadband Vivaldi antenna elements covering 4–10 GHz, which meets the requirements of low cost, lightweight, and compact volume, is designed and proposed. The prototype is integrated with two orthogonal linear polarized 4 × 5 arrays, each of which is composed of 20 Vivaldi antenna elements. The distance between adjacent antenna elements is 1/2 λ in both E‐plane and H‐plane. By increasing thickness of the slice elements compared with traditional end‐fire arrays on printed circuit board, the wide‐band impedance matching is realized. The mutual impedance matrix of the dual‐polarization array is calculated and the equivalent circuit of the active and parasitic elements is demonstrated. Due to the orthogonal parasitic elements inserted between the adjacent active antennas, equivalent capacitance is introduced in the tightly coupled array. The measured active voltage standing wave ratio of the manufactured PAF exhibits 4–10 GHz operating bandwidth for both broadside radiation and 45° scan in both E‐ and H‐plane polarization. The proposed wideband PAF has a promising potential application prospect in fast radio burst and other astronomic observation.

Compact multi‐band eight‐element MIMO antenna with decoupled antenna pairs for 5G mobile terminal applications

AbstractThis paper presents a novel design method for a tri‐band multiple in multiple out (MIMO) antenna. The antenna consists of four sets of identical antenna pairs arranged on the two side frames. Three resonant modes can be obtained using a microstrip coupling feed structure by employing different branches in antenna unit design. The working frequencies of the modes can be adjusted independently. Moreover, in each pair of antennas, two antenna units were closely arranged and a decoupling grounding branch was employed between the adjacent antennas to ensure good isolation. The tri‐band eight‐element MIMO antenna operates at 3.5, 4.9, and 5.6 GHz and the isolations were better than 14 dB. The proposed antenna had a low profile of 0.06 and good isolation so it has potential applications in 5G mobile terminals.

High Isolation MIMO Antenna System for 5G N77/N78/N79 Bands.

This paper presents a symmetric dual-band multiple-input multiple-output (MIMO) antenna system tailored for fifth-generation (5G) mobile terminals. Operating within the 5G frequency bands N77/N78 (3.4-3.6 GHz) and N79 (4.8-5.0 GHz), the proposed MIMO system achieves high isolation between adjacent antenna elements through slotting and self-decoupling technologies. Antenna elements are strategically positioned on two frames perpendicular to the smartphone's main board. Each antenna element integrates a rectangular microstrip radiator on the inner frame surface, accompanied by a grounded rectangular ring on the outer frame surface. The feed line, situated atop the main board, connects to an external SMA connector located at the main board's bottom. Measurement results reveal isolations exceeding 20 dB for the lower band and 24 dB for the higher band. The fabricated and tested MIMO antenna system demonstrates excellent agreement between simulation and measurement outcomes.

A Dual-Band 8-Antenna Array Design for 5G/WiFi 5 Metal-Frame Smartphone Applications.

This paper presents a dual-band 8-port multiple-input multiple-output (MIMO) antenna specifically designed for fifth-generation (5G) smartphones, featuring two open-slot metal frames. To enhance impedance matching and improve isolation between adjacent antenna elements, each antenna element employed a coupling feed. All simulation results in this paper come from Ansys HFSS. The operational frequency bands of the proposed antenna spanned 3.36-4.2 GHz for the lower band and 4.37-5.95 GHz for the higher band, covering 5G New Radio (NR) bands N78 (3.4-3.6 GHz) and N79 (4.4-4.9 GHz), as well as WiFi 5 (5.15-5.85 GHz). Notably, the antenna demonstrated outstanding isolation exceeding 16.5 dB within the specified operating bands. The exceptional performance positions the proposed antenna as a promising candidate for integration into 5G metal-frame smartphones.

Linear Phased Metamaterial Incorporated Patch Antenna Array at 28 GHz for 5G Base Stations

This article presents a 1×6 linear phased antenna array implemented with metamaterial incorporated patch antennas for 5G base stations. The single element antenna was modelled on Rogers RT/duroid 5880 substrate in the dimensions of 7.8×7.8×0.254 mm3 with metamaterial incorporated partial ground plane and complementary metamaterial incorporated patch. This metamaterial incorporated antenna structure is resonating in 22.03–33.55 GHz at central frequency of 28 GHz with 40% impedance bandwidth with respect to the –10 dB return losses. With aim to design a radiating structure for 5G base stations and in order to enhance the gain, a six element phased array was developed using the abovementioned single element antenna with inter element spacing 7.8 mm between the adjacent antenna elements. In the analysis of this phased array, we observed acceptable diversity parameters (isolation, ECC, DG, CCL, and MEG) and presented beam steering capabilities by changing the phase difference between the adjacent ports. The proposed six element phased array antenna is capable to steer the beam to ±43.5° and capable to cover 5G NR n-257, n-258 and n-261 bands with significant gain and efficiency.

Design of a Compact and Minimalistic Intermediate Phase Shifting Feed Network for Ka-Band Electrical Beam Steering.

Intermediate phase shifting is a footprint- and cost-reduction technique for reconfigurable feed networks. These feed networks are utilized in antenna arrays to perform electrical beam steering. In intermediate phase shifting, a phase shifter is shared between two adjacent antennas. Conventionally, antennas only have individual phase shifters. With shared phase shifters, we reduce the number of components and the footprint by 25%. Consequently, this decreases the price and enables designs at millimeter-wave frequencies where space is limited due to frequency-dependent antenna spacing. This intermediate phase shifting is demonstrated by designing a reconfigurable feed network for the Ka-band that generates a continuous phase shift profile for beam steering. Due to the use of varactors and a novel biasing method, it does not require expensive beamformer integrated chips or lumped components for biasing. The feed network is combined with a 4 × 4 antenna array to demonstrate its beam-steering capabilities. The result is a high-density and minimalistic design that fits in a small volume of 25.6 × 25.6 × 0.95 mm3. With this small antenna array, the main beam is steered at ±40∘ broadside, providing full 1D and restricted 2D steering. It is a potential candidate for wireless sensor and mobile networks.

Non-uniform distributed silicon optical phased array for high directionality and a wide steering range.

A non-uniform distributed silicon optical phased array (OPA) is proposed and numerically demonstrated to realize high directionality and a wide range for beam steering. The OPA is composed of grating antennas with dual-layer corrugations along silicon strip waveguides, which can achieve a high directionality of 0.96 and a small divergence angle of 0.084°. To reduce the crosstalk between adjacent antennas and realize a wide steering range, the genetic algorithm is improved and utilized to arrange the locations of grating antennas. As a proof of concept, a 32-channel non-uniform distributed OPA is designed and thoroughly optimized. The simulation results successfully demonstrate a two-dimensional wide steering range of 70∘×18.7∘ with a side-mode suppression ratio (SMSR) over 10dB.

AN X/Ku DUAL-BAND SHARED APERTURE UNIFORM LINEAR ANTENNA ARRAY FOR AIRBORNE SYNTHETIC APERTURE RADAR APPLICATIONS

An amplitude distribution of shared aperture antenna array for airborne SAR applications using a dual-band (X/Ku-band) synthesis is presented in this research. It is utilizing a linear arrangement with 1 × 8 antenna elements and a series feeding mechanism to operate in the X/Ku bands. The proposed shared aperture antenna array has eight elements providing a uniform array in the X and Ku bands. To realize the proposed scanning array, the X/Ku-band antenna array takes an inter-element spacing of 0.7 λ, which provides a scanning angle of ± 25°. When the space between adjacent antenna arrays is effectively used to reduce the influence of mutual coupling, the synthesis array's X-band and Ku-band antenna arrays can perform well in isolation. The uniform linear array exhibits Side Lobe Level (SLL) of -23.9 dB in X-Band and -24.7 dB in Ku-Band, with maximum realized gains of 14.2 dBi in X-Band and 15.7 dBi in Ku-Band. The isolation between bands and ports exceeds 25 dB. The uniform amplitude distribution shared aperture antenna (UAD SAA) has accepted an SLL performance of -13.5 dB. Additionally, it displays a uniform (X/Ku-band 200/144 MHz) impendence bandwidth that is relatively wide.

A twelve element dual-band MIMO antenna for 5G smartphones.

In this paper, a 12x12 dual-band MIMO antenna for 5G smartphones is proposed. It operates in the sub 6 GHz (2.4GHz and 3.5GHz) frequency bands. The MIMO antenna elements are printed on an FR4 epoxy substrate that has a thickness of 0.8mm. The main substrate measures 150 × 75 × 0.8 mm3, while the side substrates have dimensions of 75 × 6 × 0.8mm3. The twelve dual-band antenna elements are compact in size. Each antenna element size is reduced significantly, which is 11.20 × 5.98 mm2(0.0896λ × 0.04784λ). These antenna elments are arranged in such a way that the MIMO antenna not only provides polarization diversity but also helps in achieving good performance in terms of isolation, which is more than 13.5 dB between two adjacent antenna elements. Another significance of the proposed antenna is that both the frequency bands can be tuned independently by varying the corresponding length of each arm. The performance parameters like efficiency is around 40-56% for the lower band and it is 48-62% for the upper band. The envelope correlation coefficient (ECC) is below 0.04 in both frequency bands for the proposed dual band MIMO antenna.

Uniform/Selective Heating Microwave Oven Using High Efficiency GaN-on-GaN HEMT Power Amplifier

A high-efficiency uniform/selective heating microwave oven was developed. Because the power amplifier requires high-efficiency characteristics to function as a microwave source, a free-standing Gallium Nitride (GaN) substrate was applied in this study. By applying a harmonic tuning circuit, an output power of 71 W and PAE of 73% were achieved in pulsed operation, and an output power of 63 W and PAE of 69% were achieved in CW operation. Moreover, we fabricated a prototype PA module that consists of an oscillator, a driver amplifier, PA, and other RF circuits. The output power was controlled by pulse width modulation to maintain high efficiency regardless of output power. We evaluated the arrangement of antenna polarizations to isolate each antenna. By suppressing the interference of output from adjacent antennas, it is possible to irradiate the object on the top surface of the antenna, thereby demonstrating heating characteristics with small temperature unevenness. The prototype microwave oven successfully demonstrated uniform/selective heating.

Ten-Port MIMO Inverted-F Antenna for LTE Bands 43/48/49 Bands Smartphone Applications

This paper presents a design and performance analysis of a 10-element 5G massive Multiple Input Multiple Output (m-MIMO) antenna array for sub-6 GHz mobile handsets, specifically for Long Term Evolution (LTE) bands 43 (3600–3800 MHz) and 48/49 (3550–3700 MHz) applications. The proposed antenna array consists of ten closely spaced inverted-F antennas with a compact size of 20 × 9 mm2 of a single element. The proposed antenna array provides high efficiency and low correlation between the antenna elements, which result in increased data rate and enhanced signal quality. The performance of the antenna array is evaluated in terms of the radiation pattern, diversity gain, efficiency, and correlation coefficient. The simulation and measured results show that the proposed antenna array achieves an approximate peak gain of 2.8 dBi and a total efficiency of 65% at the resonance frequency of 37 GHz and a low correlation coefficient of 0.07 between the adjacent antenna elements. Moreover, the single and two-hand modes are also given in order to highlight the potential of such a structure as a smart mobile terminal. The simulated results are discovered to be in excellent agreement with the measured values. We think this structure has a bright future in the next generation of smart mobile phones based on the performance and the measured findings.

Isolation Enhancement for Vivaldi Antennas Using Hyperbolic Metasurface

In this communication, we propose a block-and-guide method of enhancing isolation between Vivaldi antennas in the whole X-band using hyperbolic metasurface (HMS). The HMS consists of periodic parallel metallic strips patterned on a thin dielectric substrate. Due to its strong anisotropy, the HMS exhibits a passband for electromagnetic (EM) waves propagating along the strip direction while a stopband for EM waves propagating along the orthogonal direction. When the HMS is placed close to the opening end of Vivaldi antenna, broadside radiation of the antenna can be suppressed while the end-fire radiation is almost unaffected, leading to enhanced isolation between adjacent antennas. Rather than adding auxiliaries in between antennas, the HMS can be readily integrated into the antenna radiator structure, which is more favorable for practical applications, especially in compact space. To verify this method, the prototype was fabricated and measured. Both simulated and measured results show that when the distance is 0.5λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength of 10.0GHz) between two Vivaldi antenna elements, the isolation can be increased by at least 10.0dB in the whole X-band. This work provides an alternative to enhance isolation between wideband end-fire antennas and may find applications in radar, wireless communication, etc.

A compact 4 × 4 reconfigurable MIMO antenna design with adjustable suppression of certain frequency bands within the UWB frequency range

This paper introduces a novel 4 × 4 multiple-input multiple-output (MIMO) antenna design with a reconfigurable operating band within the Ultra-Wideband (UWB) range. The antenna consists of four rectangular radiating elements arranged symmetrically and orthogonally on a defected ground plane. The design incorporates switching elements that allow adjustable and reversible suppression of specific bands within the UWB range, enabling the antenna to operate in three different modes: UWB, X-band, and dual-band with sub-6GHz and X-band. Thus, a single UWB antenna can serve as three different antennas, suppressing certain frequencies as required. To mitigate mutual coupling between adjacent antenna elements, four thin stubs are strategically placed at the center of the ground plane, forming a square with open corners. When one of the antenna elements is excited, this structure acts as an insulator, ensuring that the surface current is confined solely to that element and not induced in others. Experimental verification of the proposed design was performed by fabricating and testing the antenna. The results indicated good agreement between simulation and measurement data for various parameters, including S-parameters, radiation patterns, gains, and MIMO parameters such as envelope correlation coefficients (ECC), diversity gain (DG), mean effective gain (MEG), and total active reflection coefficient (TARC).

Simultaneous Suppression of Cross-Band Scattering and Coupling Between Closely Spaced Dual-Band Dual-Polarized Antennas

When two antennas working in different frequency bands are placed in proximity, they suffer from strong cross-band interactions that degrade their radiation performance and reduce the isolation between them. This paper presents holistic methods to simultaneously suppress cross-band scattering and coupling. Specifically, we develop a systematic solution to suppress the scattering of low-band (LB) antennas to high-band (HB) radiation as well as the scattering of HB antennas to LB radiation using three new techniques. This leads to much reduced cross-band coupling between the LB and HB antennas. The proposed methods are applied to a “1 LB + 1 HB” dual-band array configuration with only one LB cross-dipole and one HB cross-dipole placed side-by-side to exclude the effects of the array topology. The robustness of the proposed methods is comprehensively verified for different scenarios by simulations and experiments. Furthermore, the methods are evaluated in a “1 LB + 4 HB” array configuration. In addition to effectively suppressing cross-band scattering and coupling, the proposed methods also demonstrated a significant reduction in in-band coupling between adjacent HB antennas.

Codebook Based Antenna Configuration: A New Network Planning Paradigm for mmWave Mobile Communication Systems

To configure the azimuths and downtilts of massive antennas optimally is of great importance for the mmWave mobile communication systems to support diverse services, however, it is always computationally forbidden due to the huge number of possible combinations in real-world mobile networks. In this paper, we develop an effective and efficient method to deal with this intractable optimization task. First, we explore the most promising azimuth and downtilt configurations of each antenna with a branch-and-bound procedure followed by a semi-definite relaxation algorithm, which finally generates a codebook with finite elements to reduce the unnecessary searches for similar or unpromising configurations during global search; second, a Monte Carlo tree search method is introduced to iteratively optimize the azimuths and downtilts of all antennas, aiming at alleviating the mutual interference of adjacent antennas to maximize the signal-to-interference ratio of the target service area, during which the generated antenna configuration codebook guides the iterative search process efficiently. Experiment results in real urban scenarios show that our proposed method can produce the best signal-to-interference ratio coverage as compared with state-of-the-art ones. Moreover, the proposed algorithm can scale up straightforwardly, making it a competitive choice for large-scale network optimization.

High Isolated 10-MIMO Antenna Elements for 5G Mobile Applications

The enormous increase in gadgets has resulted in a data rate shortage insufficient to satisfy the user's needs. The multiple input multiple output (MIMO) technique is substantially deployed in the 5G wireless communication system to increase channel capacity and provide sufficient throughput. However, MIMO antennas are associated with mutual coupling, especially between closely spaced antenna elements, resulting in a low MIMO performance. Therefore, effective isolation techniques are essential to reduce the mutual coupling between the adjacent MIMO antenna elements. A hybrid decoupling technique of self-isolation and an orthogonal mode approach has been proposed to provide significant isolation for high MIMO order 5G mobile applications. A compact self-isolated 10 × 10 MIMO antenna system has been proposed for 5G mobile phone applications operating at the 3.5 GHz frequency band. The antennas act as radiating and isolating elements simultaneously, providing significant isolation. Furthermore, the self-isolated 10-MIMO antenna elements are printed on double side edges of FR-4 small substrates orthogonal to the system substrates, forming an orthogonal mode that enhances the self-decoupling approach. The s-parameters results indicate significant isolation of less than -19 dB between the adjacent 10-MIMO antenna elements. Likewise, the evaluation results of the MIMO performance metrics such as envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), and channel capacity Loss (CCL), are less than 0.006, 9.97 dB, -10 dB, and 0.08 bits/s/Hz respectively. The isolation result and the evaluated MIMO performance metrics demonstrate that the proposed 10-MIMO antenna system is sufficient for 5G mobile applications.

Large-scale assembly of geometrically diverse metal nanoparticles-based 3D plasmonic DNA nanostructures for SERS detection of PNK in cancer cells

The organization of geometrically diverse metal nanoparticles into a core/satellite structure at a large scale is a promising strategy for improve SERS performance due to hot spots localized enrichment and signal increase. However, due to the lack of extensional frames and strong electrostatic repulsion between plasma NPs, the fabrication of such 3D architectures with a high-density periodic hotspot in the focus volume has proven exceedingly difficult. Herein, we demonstrate a facile large-scale assembly of geometrically diverse metal nanoparticles strategy for constructing spatially extended 3D plasmonic nanostructures resembling “signal towers” based on RCA-mediated periodic organization of gold nanospheres (GNS) surrounding gold nanorods (GNRs). Using cancer cell T4 PNK as a model, a padlock probe with 5′- hydroxyl (P-circle) was designed as the T4 PNK substrate. The center Au nanorod was coated with P1 and served as a “pedestal” to allow substantial loading of P-circle after target phosphorylation to initiate the rolling ring amplification reaction (RCA). The resultant DNA nanowire serves as an “antenna” to successively lock numerous Raman reporter P2 (Cy3-P2-SH) through base pairing at regular intervals. Finally, the 3D plasma DNA nanostructures that resemble “signal towers” could be obtained by placing a large number of GNS with a strong affinity for Au–S. The proposed 3D SERS sensor exhibited a sensitivity of LOD as low as 0.274 mU/mL, which was attributed to a substantial electromagnetic field enhancement at the inter-nanoparticle gaps between the adjacent pedestal and antenna. Moreover, by exploiting the synergistic effect of the periodically extended DNA scaffold generated by RCA amplification and the co-assembly of thiol ligand, the loaded GNS can be extended to three-dimensional space, forming a high-density periodic hotspot in the focal volume, thereby ensuring high enhancement and high reproducibility of Raman signals. In addition, this method can be used to quantify T4 PNK in HeLa cells, demonstrating its applicability in diagnosing and estimating PNK-related diseases in complex fluids.