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This research paper is proposed to cater the design requirements of phased array antenna with side lobes pertaining for radio frequency (RF) wireless domain applications. As wireless communications have become an inevitable part of our lives as-on- date, designing smaller and lighter mobile terminals is one of the critical requirements for the development of wireless systems. A single antenna gives only a small directivity, whereas in terms of increased directivity an antenna array can be a possible candidate. Considerable optimization methods for synthesizing array pattern have started to emerge thereby achieving a pattern of desired one related to the application we work in. The major factor which drives the far field structure in phased array antenna with an allowable side lobe level is the power distribution among the array of elements. This paper presents a novel method for side lobe level (SLL) suppression in amplitude tapered planar array structure and it is compared with different distribution methods relating to array coefficients with prime focus on Taylor, Chebyshev and Gaussian distributions. CST Microwave Studio software is used to simulate various distributions and it is compared with characteristics such as gain, directivity, beam width and side lobe level suppression.

This paper introduces an advanced meta-heuristic optimization technique, namely, Atom Search Optimization (ASO) for the synthesis of linear and planar arrays. Synthesis of array antenna is a traditional electromagnetic problem. Investigations have been made by many researchers on synthesis of various antennas by applying several algorithms. ASO is a global optimization algorithm based on atom dynamics in dealing with different challenging problems. The ASO is applied to the array synthesis of the symmetric and asymmetric linear array antennas. To verify the effectiveness of the ASO algorithm, a comparative analysis of simulation results and published results for linear arrays has been made. The ASO optimized non uniform amplitude coefficients have been applied to the ON elements of the two ring concentric circular array. A comparative analysis with Firefly algorithm (FA) and Flower Pollination Algorithm (FPA) show the proposed algorithm is a comprehensive optimization algorithm in antenna array pattern synthesis.

Since most studies for estimating an angle-of-arrival (AOA) based on the antenna array have considered the antenna array with a single configuration, they are not proper to simultaneously estimate AOAs of multiple signals with various frequencies. In this paper, we introduce a cascade AOA estimation technique consisting of CAPON and Beamspace Multiple Signal Classification (MUSIC), based on a Combined Array Antenna (CAA) with Uniform Rectangular Frame Array (URFA) and Uniform Circular Array (UCA), for enhancing the above problem. In addition, we provide the computational complexity analysis for showing the low computational complexity of this technique comparing to the conventional technique.

Recently, thinning an antenna has resulted in attractive antenna radiation characteristics enhancement. This performance enhancement using a thin antenna array is achieved because the inter-coupling effects of the array elements are reduced. Though the thinning both reduces the weight of the antenna and enhances the radiation characteristics, iterative algorithms can further enhance the performance and hence, in this research, an optimizer algorithm and inter-coupling reducing mechanisms are applied. The excitation weights of the individual array elements are thinned by turning some of the elements off while some of the elements are turned on. The purpose of the thinning is to enhance the antenna performances like reduced SLL, high directivity, reduced power consumption and flexible radiation pattern. The SLL attenuation mechanism is applied to reduce the SLL in addition to the SLL reduction using the thinning and beamforming. Hence, in this paper, the three techniques (thinning, beamforming and SLL attenuation) are proposed to be integrated to enhance the antenna radiation characteristics. In general, the proposed combined method has resulted in much better SLL reduction, directivity improvement, and power wastage reduction.

In this paper, a new optimized quadrant pyramid antenna array (O-QPAA) structure is proposed for back lobe minimization of planar antenna arrays (PAA). Based on the PAA size, it is thought to be formed of a number of concentric co-planar squared antenna arrays (SAA) or rectangular antenna arrays (RAA) placed in the X-Y plane. Initially, to construct a non-optimized QPAA, these concentric SAAs or RAAs are distributed vertically along the Z-axis with uniform vertical spacing. Thereby, the QPAA is treated as a hybrid of uniform SAAs or RAAs and a linear antenna array (LAA). However, the QPAA may have a main beam and back lobe of the same amplitude. To address this issue, the O-QPAA structure is proposed, which allows for the minimization of the back lobe while still controlling the QPAA pattern features such as side lobe level (SLL) and half power beamwidth (HPBW). The particle swarm optimization (PSO) approach is employed in this O-QPAA structure to identify the optimal values of the three main QPAA parameters, which are inter-element spacing within each SAA or RAA, vertical spacing, and the non-uniform excitations of the LAA to form the entire O-QPAA radiation pattern.

This paper presents a high-gain slotted ridge waveguide array antenna (SRWAA) with inductive diaphragms, which can realize a wide-sector beam with a low sidelobe simultaneously. The proposed antenna can cover a wide detection range and avoid interference from other directions. The expected excitation distribution for the antenna array is extracted through a beamforming method. To reduce the influence of the dispersion phenomenon on signal quality, inductive diaphragms are inserted into the sidewall of the ridge waveguide, which is fully analyzed from the point of the equivalent circuit. A cut-off-mode power divider is utilized, which can control the power ratio flexibly. A SRWAA working at 24.125 GHz, including a six-way feeding network, and a 6×24 slot array with the size of 330 mm × 66.8 mm is designed and fabricated. The measured sidelobe level (SLL) and half-power beamwidth (HPBW) in the elevation plane are -19.6 dB and 54.41°, with the counterparts in the azimuth plane -29.8 dB and 3.15°, respectively. The measured peak gain is 22.3 dBi at 24.125 GHz. The measured results are in good agreement with the simulated ones. This work has the potential to be applied in air detection, anti-unmanned aerial vehicles (UAVs), meteorological radar, and imaging radar.

An antenna-in-package (AiP) of end-fire and dual-polarization at 28 GHz is presented. It is formed by four periodic antennas of broad bandwidth and high-isolation, fabricated by the low-temperature co-fired ceramics technology. The dual-polarizations are realized by integrating a horizontal metal stripline-coupled dipole with a vertical magneto-electric monopole, incorporated into a multilayer architecture for compactness. The AiP skillfully implements vertical vias and horizontal strip lines in the cavities between antennas to improve isolation and polarization purity. This AiP has numerically been examined for end-fire high gain and beam steering in user equipment (UE) applications. The prototype was measured to show good isolation lower than -25 dB from 26.5 to 29.5 GHz and agree with full-wave simulations. The antenna array is finally integrated with 1x4 boresight radiation microstrip antennas to form a complete UE AiP.

A simple decoupling method between two closely-located dual-polarized slot antennas is proposed in this communication. Based on substrate integrated waveguide (SIW), the dual-polarized antenna is realized using cross-shaped slot and U-shaped feed line, and two identical elements are closely located in edge-to-edge space of only 0.031λ0 to form the multiple-input-multiple-output (MIMO) array, where λ0 is the free-space wavelength at the center operating frequency. Wideband characteristics, high dual-polarized isolation, and low envelope correlation coefficient (ECC) are realized by introducing a superstrate with gradient relative permittivity (GRP) above the array. The GRP is obtained using drilling hole arrays on low-cost FR-4 materials. To validate the proposed design, the antenna array is fabricated and measured. The measured result shows that 13 dB and 16 dB isolation enhancements are provided for two orthogonally polarized fields, simultaneously. Moreover, the measured operating bandwidth is from 8 GHz to 10.35 GHz (about 25.6%, the isolation is more than 20 dB), and the ECC between two antennas is less than -52 dB for E1-pol and -62.4 dB for E2-pol over entire operating band. The proposed method has the potential to be used in MIMO wireless systems.

This communication presents a compact end-fire leaky wave antenna (LWA) is presented on the coplanar stripline (CPS) with narrow width property under a new operation mechanism. By periodically loading stubs between two strip lines in parallel, the leaky region of its fundamental mode can be generated in the CPS with forward beam scanning property, and the end-fire radiation is realized at the frequency where its normalized phase constant is equal to one. Since the leaky region of the fundamental mode owns a relatively low cutoff frequency, the proposed antenna generally has the property of small overall size in this region. The end-fire operating frequency is firstly discussed based on the circuit model, and the corresponding radiation property is then analyzed from the antenna array point of view. The leakage constant as well as characteristic impedance of the proposed antenna are further investigated with the full-wave extraction method. Moreover, a modified structure is proposed as the last element of the antenna to leak out the rest of the energy at its end. Finally, a CPS leaky-wave prototype antenna is designed and fabricated, where the measured results show good agreement with the simulated ones and thus validate the predicted performances.

This paper describes a compact dual-polarized endfire antenna array for 5G millimeter-wave (mmWave) mobile application. The dual-polarized endfire antenna element is constructed by a compact open-ended cavity with cavity mode for vertical polarization (VP) radiation and open-slot mode for horizontal polarization (HP) radiation. With the integrated design of VP and HP elements, the proposed antenna shows much more compact size compared to existing schemes. To enhance the bandwidth of low-profile VP radiation, a slot is etched on the cavity to create a new mode for dual-resonance response, realizing a wide bandwidth of 24.5~29.5 GHz for both polarizations. In addition, radiation pattern modification techniques are employed to achieve good endfire beams with high front-to-back ratio for both polarizations, thus enabling a high peak gain of 10.3 dBi and 11.3 dBi for VP and HP, respectively. A wide beam scanning range of ±50° with realized gain above 7 dBi is realized at 27 GHz for both polarizations. In virtue of compact size, wide bandwidth, high gain, and good spatial coverage, the proposed design strategy is promising for future 5G mmWave mobile phones.

We consider a directional antenna array in an ultraviolet (UV) scattering communication ad-hoc network. To efficiently characterize the link gain coverage of a single antenna, we propose an algorithm based on one-dimensional (1D) numerical integration and an off-line data library. We also investigate the two-dimensional (2D) scattering intensity distribution, which shows that the link gain profile can be well fitted by elliptic models. In addition, assuming that the node distribution of an ad-hoc network obeys Poisson point process (PPP), we investigate the network connectivity probability and the minimum power that the network remains connected under different antenna parameters, and compare the performance of directional antenna array with that of omnidirectional antenna array. Numerical results show that employing directional antenna arrays can effectively reduce the power required for network connectivity. Moreover, we consider a two-layer network using dirctional antenna array, and design adaptive node assignment and power allocation to increase the minimum rate. Numerical results show that the proposed algorithm can improve the minimum node rate by more than 10%. Moreover, similar performance gain can be observed even considering the overhead of a media-access control (MAC) layer protocol.

This paper presents a gain-equalized Ka-band Rotman lens-fed antenna by using phase gradient transmission lines (PGTLs). With PGTLs, the variation trend of the output progressive phase differences among the feeding ports are inverted. The aperture loss of the planar antenna array is then partially compensated by the efficiency of the lens when performing a wide-angle beam scanning. Hence, gain equalization is achieved among multiple beams with an acceptable gain degradation. To reduce the total size, the Rotman lens with PGTLs, the feeding networks, and the antenna array are stacked vertically. Meanwhile, the feeding network is implemented with substrate integrated coaxial lines, suppressing the parallel-plate-mode inside the multilayer structure. In order to validate the proposed design, a compact Rotman lens fed antenna operating at 24.75-27.5 GHz (FBW=10.5%) is designed and fabricated. The results show that the gain drop of the Rotman lens-fed multibeam antenna is reduced from 4.4 dB to 1.5 dB at the design frequency of 26 GHz, covering a wide angular range between ±56∘.

This manuscript presents a novel broadband dual-polarized filtering patch antenna array using low-temperature co-fired ceramic (LTCC) process for 5G millimeter-wave applications. The filtering antenna element is implemented by using a ±45° polarized patch antenna fed by two pairs of differential L-type probes. An additional square ring and open strips are connected to each probe, resulting in radiation nulls and realizing the lower/upper stopband rejection level over 24 dB with skirt selectivity. The cross coupling among these structures not only introduces filtering responses, but also contributes to broadening the passband of 24.25-29.5 GHz covering 5G n257/n258/n261 bands. The antenna performance is validated by equivalent circuits based on transmission line models, which reveals clearly the principles of filtering antenna step by step and provides guidelines for further designs. The proposed filtering antenna element is expanded to a 4×4 filtering antenna array with shunt fed feeding networks. The spacing between elements is 0.48 λ0. The measured results demonstrate that the array performs good filtering characters including high stopband rejection, high selectivity, and wide upper stopband up to 40 GHz, where the antenna efficiency (considering radiations from all the directions) is less than 5%. In addition, the differential feeds provide symmetric radiation patterns with low cross-polarized counterparts. Compared with other reported works, the proposed filtering antenna/ array has excellent performances of wideband, high stopband rejection and wide upper stopband for potential 5G millimeter-wave applications.

This letter proposes a hybrid decoupling structure consisting of a neutralization dielectric board, metal baffle, and feeding network to enhance the isolation in a compact large-scale base station array. Both the neutralization- and partition-based schemes are utilized to reduce the mutual coupling between antennas. The neutralization dielectric board provides a new signal path to cancel the original mutual coupling, and the metal baffle is employed to suppress the propagation of the space electromagnetic wave. The antenna elements in the vertical direction are excited by a feeding network. A 44 dual-polarized antenna array with a horizontal edge-to-edge distance of 0.38 free-space wavelength is designed and fabricated to demonstrate the effectiveness of the proposed structure for large-scale arrays for base station application. Simulated and measured results show that the voltage standing wave ratio is less than 1.7, and the isolation between any two ports in the array is better than 20 dB within the entire operating frequency band. Stable radiation patterns with a good front-to-back ratio and cross-polarization ratio are achieved.

A planar single-layer parasitic swastika-shaped structure, which serves as an effective isolator, is developed for mutual coupling reduction in wideband, high-density circularly polarized (CP) arrays. A closely spaced two-element CP antenna array demonstrates the efficacy of the approach. The currents induced by the CP coupling are effectively canceled out when this isolator is integrated into it. The antenna elements are co-planar. They are arranged with a center-to-center distance of 0.4λ L (λL) being the wavelength of the lower bound of the array's operational bandwidth) and have an extremely small edge-to-edge distance of ∼ 0.024λ L. The parasitic element yields an increase of the isolation level between the antenna elements of more than 9.4 dB over the entire operational band, with a maximum improvement of 20.4 dB. Moreover, the antenna elements realize a modest maximum gain improvement of ∼ 1.2 dB in the boresight direction over the same band. The overlapped impedance matching and 3 dB axial ratio (AR) bandwidths cover the range of 1.7-2.7 GHz, a ∼ 45% fractional bandwidth. A prototype was fabricated and measured; the measured results are in good agreement with their simulated values.

A novel leaky-wave antenna (LWA) array capable of bilateral beamforming is investigated for applications in indoor and short-distance mobile communication. The antenna array is designed on a double-layer substrate-integrated waveguide (SIW) with a multiport feeding network. The upper layer is a four-port SIW with a tapered open stopband suppression structure and two tapered radiating slot arrays. By adjusting the periods and widths of slots, the two slot arrays radiate in different directions, and their radiation fields satisfy the cosecant-squared distribution. The lower layer is a single-port SIW power divider with an allocation ratio of 1:5 using a Z-shaped junction. There are transitions at both ends of the lower SIW for coupling energy up into the radiation layer. When feeding the upper layer from its two input ports individually, two dual broad-beams with beam directions of ± 25° and ± 45° can be generated, thus achieving amplitude-shaped dual-beam switching for smart beam switching antenna systems applied in short-distance mobile communication. When feeding the whole double-layer array through the input port of the power divider, the above two dual beams will be superposed together and form a cosecant-squared radiation pattern, which is suitable for uniform radio wave coverage along straight areas. The proposed array was fabricated and measured to validate its performance, and the results showed the efficiency of the design.

Near-field radar cross-section (NF-RCS) of a target depends on antennas’ radiation and can be maximized by adjusting the radiation patterns. It is justified by the power return ratio and can be computed by a comparison method. A theoretical foundation of operational mechanism for phased arrays of antennas is presented to produce conformal radiations for NF-RCS enhancement. The target’s scattering coefficients are extracted from operating the antenna array’s digital phase shifters to steer the resulting beams in this work. The scattering matrix is then analyzed by the singular value decomposition (SVD) to determine the antennas’ excitations for maximum NF-RCS with estimation stability. It results in orthogonal beams for the two-way radiations of antenna arrays to interpret the scattering mechanisms. The feasibility is validated by HFSS full-wave simulations and experimental measurement data.

Large-scale antenna arrays employed by the base station (BS) constitute an essential next-generation communications technique. However, due to the constraints of size, cost, and power consumption, it is usually considered unrealistic to use a large-scale antenna array at the user side. Inspired by the emerging technique of reconfigurable intelligent surfaces (RIS), we firstly propose the concept of user-side RIS (US-RIS) for facilitating the employment of a large-scale antenna array at the user side in a cost- and energy-efficient way. In contrast to the existing employments of RIS, which belong to the family of base-station-side RISs (BSS-RISs), the US-RIS concept by definition facilitates the employment of RIS at the user side for the first time. This is achieved by conceiving a multi-layer structure to realize a compact form-factor. Furthermore, our theoretical results demonstrate that, in contrast to the existing single-layer structure, where only the phase of the signal reflected from RIS can be adjusted, the amplitude of the signal penetrating multi-layer US-RIS can also be partially controlled, which brings about a new degree of freedom (DoF) for beamformer design that can be beneficially exploited for performance enhancement. In addition, based on the proposed multi-layer US-RIS, we formulate the signal-to-noise ratio (SNR) maximization problem of US-RIS-aided communications. Due to the non-convexity of the problem introduced by this multi-layer structure, we propose a multi-layer transmit beamformer design relying on an iterative algorithm for finding the optimal solution by alternately updating each variable. Finally, our simulation results verify the superiority of the proposed multi-layer US-RIS as a compact realization of a large-scale antenna array at the user side for uplink transmission., 13 pages, 11 figures, accepted by IEEE Transactions on Communications

A new type of reconfigurable negative group delay (NGD) circuits based on active transversal filter topology is introduced in this work. By incorporating varactors with the NGD circuit at the input and output ports of active transversal filter based on distributed amplifiers (DAs), one can notably enhance the tunability for both amplitude and phase responses, thereby enabling NGD characteristic synthesis with a wider reconfigurable range. In this article, the proposed reconfigurable NGD circuits are applied to create both tunable non-Foster elements and tunable squint-free beamforming networks, which are verified by experiment. Furthermore, a general N-stage transfer function for the proposed reconfigurable NGD circuit is derived, in which a two-stage particular case is given as an illustrative proof-of-concept example. Based on the reconfigurable NGD circuits, a prototype of a tunable negative capacitor is fabricated and measured, of which the capacitance can be tuned from -1.0 to -4.0 pF over a bandwidth of 100 MHz at 1 GHz or around 10% relative bandwidth. In addition, such an NGD circuit is utilized to create a low-dispersion superluminal transmission line, which enables a reconfigurable series antenna feedline for squint-free beam steering. Experimental results show that the main beam of the NGD antenna array has a tuning range from -15° to 15° within a squint-free bandwidth of 100 MHz at 2 GHz or within a relative bandwidth of around 5%.

Publisher Copyright: Author Additive manufacturing (AM) is a rapidly developing field, which potentially decreases the manufacturing costs and enables increasingly complex antenna shapes. Metal-based AM might be particularly useful for manufacturing antennas at millimeter-wave (mm-wave) range, because these antennas are physically small enough making AM cost efficient, and manufacturing accuracy could still suffice for good electrical performance. In this letter, two additively manufactured and identical machined fully metallic Ka-band Vivaldi antenna arrays are compared. The manufactured antenna arrays are compared using RF measurements to conclude the feasibility of AM for manufacturing antenna arrays at mm-wave frequencies. Comparison of the measured radiation patterns and realized gains of each of the antenna arrays between 26 and 40 GHz shows close to identical radiation patterns for all the arrays. A loss in realized gain of 0.5-1.5 dB is observed in the AM arrays when compared to the machined array due to the used materials and the surface roughness.

This study proposes a broadband dual-polarized solar cell phased array antenna. It is constructed by using crisscross distributed metal-meshed tie-shaped dipoles, an optical transparent glass substrate, feeding probes and ground probes, a solar cell, and a metal ground. The meshed tie-shaped dipoles are sputtered on the top surface of the glass substrate. Circular metal-meshed patches located at the crisscrossing points of the dipoles on the back surface of the glass substrate are introduced to extend the operational bandwidth of the solar cell antenna. The solar cell was placed on the ground of the antenna. We fabricated a sample of the solar cell antenna and measured the electromagnetic characteristics and its power output. The results of the measurements agreed with those of simulations. The proposed solar cell antenna array had a wide operational bandwidth of 2.5-5 GHz, a wide two-dimensional range of the phase scanning angle of ±45°, a high aperture efficiency of 68.9%–84.1%, and a high relative maximum output power ratio of 87.1% compared with a pure solar cell. It is scalable, and can be used in a self-sustained 5G wireless communication system for sub-6 GHz applications.

In this paper, two wideband dual-polarized Dielectric Resonator Antennas (DRA) for X band radar applications are presented. The design procedure is started with designing a linear polarized DRA fed by a microstrip line. The feedline is optimized to excite the HEM11δ mode of DRA which corresponds to magnetic monopole like radiation. Then, a novel quadrature hybrid is designed in the feeding structure to provide both left (LHCP) and right-handed (RHCP) circular polarization. Finally, two antenna prototypes are fabricated and tested: a dual (right hand and left hand) circular polarization DRA with omni-directional pattern, and an enhanced gain version of dual-polarized CP DRA with a directive pattern. The measurement results of antennas confirm wideband impedance bandwidth (34% and 38.8%) as well as wideband Axial Ratio (AR) one (23% and 30%) in element and array structures, respectively. The antennas also provide both RHCP and LHCP radiation. The first antenna contains monopole-like radiation which is aimed at wireless systems with omnidirectional pattern requirements. The second, a 2*1 antenna array, which presents around 9 dB across the entire band. The presented antennas are good candidates for radar applications such as weather monitoring, air traffic control, and vehicle speed detection.

A method of improving the diversity and capacity of MIMO systems in non-isotropic multipath environments by loading a scatterer array is proposed. The difference between array diversity and superresolution imaging is discussed first. The phase differences caused by the “effective space” between adjacent antenna elements are the critical factors of diversity enhancement. The scatterer array, which is made of crossstructure periodically, is placed on top of the antenna array to adjust the phase center of the radiation pattern of each antenna port. By increasing the “equivalent size” of the antenna array, the correlation of part of the adjacent ports in the antenna array is decreased; thus, the array diversity is improved. Through a set of comparative examples, the effectiveness of the scatterer array is clearly demonstrated.

In this paper, an 88 dual-polarized antenna array with high gain and broad bandwidth is proposed for Q-band millimeter-wave(mm-wave) application. Metallic pillars and cavities act as magneto-electric dipoles fed by a 1 to 4 backed cavity with cross-shaped slots. The cross-shaped slots are adopted to excite two orthogonal linear polarizations. A feeding network with shared vias is designed to construct the antenna array. An 88 dual-polarized antenna is fabricated and measured. The measured impedance bandwidths are 13.4% from 34.7 to 39.7 GHz and 14.4% from 34.6 to 40.1 GHz for the two ports, respectively. The 3-dB gain fluctuation bandwidth is 8% for the two ports. The maximum gain is up to 24.8 dBi due to less substrate loss in the radiation structure. Attributed to its high gain and high efficiency, the proposed antenna is a promising candidate for mm-wave applications.

A novel electrically reconfigurable circular polarizer with high efficiency is proposed. The combination of a slot and a metal strip inclined at a certain angle could achieve circularly polarized radiation. Therefore, the polarization of the antenna can be controlled by controlling the metal strip. The proposed circular polarizer structure is simple, which is realized by two crossed dipoles printed on the top and bottom of the PCB, respectively. A microstrip coupled slot antenna is used to feed the polarizer. By controlling the PIN diode in the middle of the dipole, switching between two circular polarizations is realized. Based on the proposed antenna element, a 22 antenna array is implemented with a sequentially rotated (SR) feeding network. With the difference in the feeding phase, the radiation beam of the array can be changed while switching the polarization state. Measured results show that the antenna element achieves a peak gain of 6.4 dBic with an overall axial ratio (AR) bandwidth of 2.44-2.5 GHz for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) with radiation efficiency of about -1 dB. The proposed antenna features high efficiency, electronically reconfigurable polarization, and low cost, which is well suited for base station application

This communication presents the design of a wideband circularly polarized (CP) antenna array based on sequential rotation (SR) technique that is excited by a substrate integrated coaxial line (SICL) with mature and stable processing technology for millimeter-wave (mm-wave) applications. Initially, the influence of the amplitude and phase errors of the feeding network on the axial ratio of the CP array is analyzed, and the detailed design scheme of the wideband CP array based on SR technology is summarized, which can be used to design SR CP array with wide bandwidth and high polarization purity. Then, a SICL-fed 4 × 4 CP array working at mm-wave band and that is composed of two substrate layers and a bonding film layer is designed. The radiation element is processed with a larger chamfering, which can realize elliptically polarized radiation in a broadband range, and the impedance bandwidth is significantly expanded relative to the working state of linearly polarized and circularly polarized, which has a significant impact on the final array working bandwidth enhancement. The feeding network and radiation elements are directly connected in the same plane. Finally, the proposed antenna is processed and measured to verify the theory and design scheme in this paper. Over the frequency range of 25.0 to 34.0 GHz, the measured 1.5-dB axial ratio bandwidth of the fabricated prototype is 30.5 %, and the return losses are less than -10 dB. The maximum measured peak gain is 16.5 dBi.

In this letter, a planar broadband higher-order mode millimeter wave (MMW) microstrip patch antenna array with low sidelobe level (SLL) is presented. For the antenna element, antiphase-TM30 mode is excited by unequally etching the radiating patch with two transverse slots. Meanwhile an SIW-based pin-loaded slot coupling feeding structure is introduced to achieve merits of broadband, low cross polarization and low backward radiation. Then a one-eight power divider with in-phase unequally tapered amplitude distribution is adopted to excite an eight-element array with SLL. The GCPW-SIW transition structure is also selected to achieve broadband impedance matching. Finally, both element and array antenna are optimized and fabricated for verification. For the antenna array, the measured -10 dB impedance bandwidth is from 25.1 to 31.3 GHz (22%) with a maximum gain of 14.6 dBi at 29.5 GHz and a 3dB gain bandwidth of 27.9%. And the measured SLL at 26, 28 and 30 GHz are all less than 20 dB. Index TermsMillimeter-wave (MMW), broadband, higher-order mode, low sidelobe level (SLL).

This paper presents a conformal ultra-high-frequency (UHF) radio frequency identification (RFID) reader antenna array for doorway portal applications. The dual-patch antenna is only 100 mm wide and right-angled (V-shaped) to fit the corners of a regular portal. Patches are arranged orthogonally to create horizontal and vertical-linearly polarized fields at near-zones and at far-field distances they provide slant-polarized fields. Beam steering is enabled by phase delaying the array elements to enhance the field coverage within the doorway portal. The antenna operates in the European UHF RFID band (865-868 MHz) with a 38 MHz, 10 dB impedance bandwidth. The antenna’s azimuth and elevation half-power beamwidth is 90° and 130°. The azimuth beam is tilted to 35° from the boresight where the gain is peaked at 5.5 dBi. This antenna is low-profile, low-cost and flame retardant and paintable. Inherited properties of the antenna’s substrate make the antenna non-toxic, self-extinguishing, lightweight and highly chemical resistant. The reader antenna is compatible with both RAIN and non-RAIN alliance UHF RFID readers.

In this communication, a grid frequency selective surface (GFSS) is developed for cross-band near-field mutual coupling suppression. The unit cell of the GFSS consists of a break metal strip and a parallel LC resonator. The GFSS realizes low-stop property at 1.7-2.4 GHz (B1 band) and high-pass property at 3.3-3.8 GHz (B2 band). The novel GFSS is applied in a 5G dual-band antenna array with one B1 band antenna and four B2 band antennas. The cross-band mutual coupling coefficients are reduced from -14 dB to lower than -35 dB at the B1 band. Meanwhile, the radiation patterns of the B2 band antenna element are not affected due to the non-scattering feature of the GFSS. The dual-band base-station antenna array prototype is fabricated and measured to demonstrate the effectiveness of the proposed design in cross-band mutual coupling reduction.

In this article we present a miniaturized multiband metamaterial-based antenna for array applications, operating with good radiation performance over the LTE and UMTS uplinks within the 800–3000 MHz range. Each antenna element consists of a radiator and a metamaterial reflector. The former is a miniaturized Archimedean spiral antenna with an integrated matching line. The latter is placed 39 mm below the radiator and is shared among the multiple elements in the array application. The radiator is very compact, a square of 75 mm per side, equivalent to only 0.2 (0.75) times the free-space wavelength at 800 MHz (3000 MHz). The reflector is incorporated to achieve half-space radiation and is implemented with a novel multi-layered metamaterial structure to improve the radiation efficiency. The metamaterial, moreover, is used in a non-conventional way. In fact, we take advantage of its complete phase-response function, behaving, thus, as magnetic or electric conductor in different parts of the band. In this way, the in-phase reflection is not limited by the typical narrow bandwidth of artificial magnetic conductors. The measured S11 parameter is less than -8 dB and the simulated gain is greater than 4.2 dBi in a range exceeding the one covered by the UMTS and LTE uplinks. Furthermore, a 2×2 antenna array was also built. The reflections of each element are similar to those obtained in the single-element antenna.

A novel method to realize positive phase response of antenna element is proposed conceptually and applied in ±45-deg dual-polarized dual-beam series-fed metasurface antennas (MSAs). It takes the features of stable beam angle within the relative bandwidth of 10% and dual-polarized dual beams. Benefiting from the positive phase response zone of the antenna, the long-line effect is eliminated and the phase response between the elements is reshaped as expected. Therefore, a stable beam of series-fed array oriented at specific angle is guaranteed accordingly. To achieve the ±45-deg dual-polarized dual-beam performance, a four-port MSA element with interwoven feeding network is designed and used for further array design. For demonstration, one prototype of MSA array is designed. Considering the band of 4.7 GHz to 5.2 GHz (10%), the beam angle of the MSAs based on positive phase response control (PPRC) method is oriented to 30 deg, and the variation versus frequency is less than 6 deg, which is smaller than the variation of 19 deg for traditional array. The simulation and measurement results show that stable beam angle is achieved for the dual-polarized series-fed MSA array, indicating a promising candidate for base-station application.

Next-generation wireless communication requires antennas with excellent performance and low-profile structures. A low-profile broadband dual-polarized base station antenna array with an Artificial Magnetic Conductor (AMC) reflector and cross-polarization suppression structures is proposed. Cross-polarization is effectively suppressed by introducing the structures among the antenna elements with almost no impact on the other antenna performances, and the cross-polarization suppression mechanism is analyzed theoretically. The AMC reflector reduces the antenna profile only 0.12 λ0 (λ0 is the free-space wavelength at 4 GHz). Prototypes of the antenna element and the five-element antenna array are fabricated, and the simulated and measured results indicate that both achieve good performance over the entire operating frequency band. The antenna array has high isolation (> 28 dB), a wide operating bandwidth (3.14-5.32 GHz, 51.5%), and stable radiation performances (XPD > 29 dB, gain > 15 dBi, FBR > 37 dB). The proposed antenna array with good performance and a low profile, may be a candidate for 5G communication applications.

This paper presents a novel unequal power divider based on an inverted microstrip gap waveguide. This new geometry can achieve a large power ratio of the two output ports and a small phase difference less than 5°. Based on this novel geometry, a few distinctive unequal power dividers with different output power ratios were proposed for designing a low sidelobe array antenna at 39 GHz. To verify the design, a 16×16 antenna array was designed and measured. The measurement results indicate that the entire array antenna achieves a -10 dB impedance bandwidth of 18.5% (in the range of 35.9-43.2 GHz), a gain greater than 29 dBi from 37.5 to 41.8 GHz and an antenna efficiency greater than 50% over the entire operating frequency band. Based on the application of the newly invented distribution network, the proposed array antenna is below -23 dB on both the E-and H-planes at 37-42 GHz. Furthemore, the radiation pattern of the entire array complies with the ETSI-Class II standard for all azimuth angles.

In this paper, a wideband filtering antenna based on substrate integrated waveguide (SIW) structure for millimeter-wave (mm-Wave) applications is proposed and studied. The proposed antenna is developed using multilayer printed circuit board (PCB) technology. It consists of an SIW feeding structure with a coupling slot, differential-fed L-shaped probes as well as radiating patches. Such architecture provides wide impedance bandwidth along with good filtering characteristic in the lower stopband. Simultaneously, by introducing a pair of open slots on the individual radiating patch as well as two shorting loops on top of the coupling slot, good filtering response in the upper stopband is obtained. The suppression level in the lower stopband is then further improved by introducing a pair of shorted stubs in the coupling slot region. The proposed filtering antenna features no extra filtering circuits, wide bandwidth as well as low profile. To verify the proposed structure and design philosophy, antenna array prototypes have been designed, fabricated and measured. It achieves a 29% bandwidth from 23.5 to 31.5 GHz. Good agreement is achieved between simulated and experimental results. The proposed antenna array is particularly suitable to be applied in 5G (the fifth generation) mm-Wave backhaul communications.

This communication presents a low-profile and low scattering wideband planar phased antenna array with enhanced coupling (PAA-EC). The proposed chessboard-like PAA-EC consists of two different types of low-profile planar antenna elements that have similar radiation performance in the X-band. In addition, the two types of antenna elements have a 180° ± 37° reflection phase difference over the X-band, which guarantees the cancelation of scattering fields for low scattering purpose. On the other hand, an 8×8 reference PAA-EC and a low scattering PAA-EC are developed and fabricated to validate the radiation performance and scattering characteristics. The simulated and measured results show that the proposed low-profile planar PAA-EC operates in the 8-12 GHz band with ±45° scanning range. It also achieves at least 9-dB scattering cross section (SCS) reduction in the 8-15.2 GHz band as compared with the reference PAA-EC.

A compact dual-polarized base station antenna with filtering characteristics is proposed in this letter. The antenna is composed of a reflector, two balun structures, and two orthogonal half-wavelength radiation arms. The radiation arm mainly consists of multiple transmission lines of different widths which can be equated to inductance or capacitance. The elaborately designed radiation arm not only ensures a wideband operation but also helps to achieve low-pass filtering characteristics, without using an extra parasitic structure. For demonstration, a 45 dual-band dual-polarized antenna array operating at 690-960 MHz and 1710-2690 MHz are fabricated and measured. The implemented array (690-960 MHz) achieves stable half-power beamwidth (HPBW) of 65 10 and polarization isolation of 27 dB. Due to the filtering performance of the proposed antenna, stable high gain (17.51 dBi) and HPBW of 65 6 also can be realized at 1710-2690 MHz. The proposed antenna is suitable for the base-station application.

Biomimetic antenna arrays inspired by the fly Ormia ochracea showed a promising improvement of the angle estimation capabilities of radar sensors. So far, there is usually a loss of output power associated with this improvement decreasing the detectability of weak radar targets. In this paper, an electronically switchable two-element biomimetic antenna array is presented for the first time. This array provides the possibility to switch between a biomimetic antenna mode with enhanced phase sensitivity and a conventional antenna mode with better SNR. Circuit requirements are discussed, the design process is described, and a realization in the 77-GHz range using PIN diodes as switching elements is presented. Radar measurements verify the concept. By switching, the phase sensitivity of the realized array can be enhanced by a factor of 3 with a relative power loss of maximum 14 dB.

It is known that the most reliable communication in hard-to-reach places such as the Arctic, Tundra, Taiga is satellite communication [1-5]. Therefore, for satellite communications, it is necessary to develop your own antenna arrays. This article discusses a waveguide-slot antenna array with a Luneburg lens for a mobile satellite communications terminal, which provides a continuous and stable signal. This antenna operates in the 10.9 to 14.5 GHz frequency range. Possesses vertical polarization. The overall dimensions of the antenna array are: diameter of the diagram-forming lens 256 mm (thickness 5 mm, material FLAN 2.8 (epsilon 2.8, tangent delta 0.0015)); waveguide length 600 mm (internal section 10.5 mm by 5 mm, filling FLAN 2.8). Slotted waveguide antennas and lens are made of standard FLAN 2.8 material (epsilon 2.8, tangent delta 0.0015) 5mm thick, foiled on both sides. There are 17 coaxial cables to the HF switch (equal lengths are not required), the scanning step in elevation is 5 degrees. When using 54 waveguide-slot antennas and 18 switch inputs, a scanning sector in elevation of 90 degrees is provided. All the nodes were pre-modeled separately a cylindrical Luneburg lens with suitable waveguides, excited by slits; slotted waveguide antennas; coaxial-waveguide transitions.

In this article, we propose a novel reflector-back cavity-low-band (LB)/high-band (HB) configuration for the dual-band dual-polarized base station antenna array design. The HB antennas are embedded in the opening sections of the loop radiating arms of the LB antennas. Clear and independent radiating environments are fulfilled by using two different types of reflectors (large planar reflector and back cavity). The mutual effects between the LB and HB antennas help to acquire good impedance matching and stable radiation patterns. Loop-like LB radiators work as directors in the HB, thereby effectively suppressing the side and back radiations of the HB antennas. Dual-function open slots are loaded on the ground stubs of the LB baluns, serving as impedance transformer in the LB but filtering structures in the HB. The experimental results validate that the proposed antenna array successfully covers bandwidths of 0.69–0.96 and 3.3–3.8 GHz (VSWR < 1.5) for 4G/5G applications. The port isolations are higher than 38 and 25 dB in the LB and HB, respectively. With the two independent radiating environments formed in the two bands, both LB and HB antennas exhibit stable unidirectional radiation patterns. The antenna gains and HPBWs are also satisfactory in both bands.

Future moderate-band (MB) high-power microwave sources will take advantage of having a small size and a low cost. However, the output power of existing designs is limited by the dc voltage supply. To tackle this issue, this article proposes a novel scalable high-power microwave source based on the concept of coherent stimulated emission. The proposed microwave source consists of an antenna array, in which the two arms of each dipole antenna are connected with a fast-rise time switch and charged by a dc voltage source. Each antenna unit is triggered by the incoming wave radiated from the previous unit and then oscillates and correspondingly produces a new electromagnetic wave to trigger the next one. Both simulations and experiments show that the output waves of multiple antenna units are in phase, and the output power is accordingly enhanced. Compared with the existing MB high-power microwave sources, the proposed microwave source is able to significantly boost the maximum output power by applying more automatically triggered antenna units, featuring strong scalability and less limitation by the dc voltage supply.

Mutual coupling between the space-borne antenna has an essential impact on the communication characteristics of a wireless link to submerged submarines. In this article, the mutual coupling between antennas of a circular array in an anisotropic plasma over a very low-frequency (VLF: 3–30 kHz) range is investigated. An expansion of the currents into phase modes enables us to develop an efficient method to analyze the mutual coupling between antennas. The $N$ -coupled integral equations for antennas of an array are first derived with full consideration of the mutual coupling effect. By making use of the phase modes combined with the method of moment (MoM), the $N$ -coupled integral equations are decomposed into independent ones and solved for each phase mode. Computations and discussions show that the self and mutual impedances of antennas are increased with the geomagnetic field tilt angle. Moreover, the mutual impedance is decreased with the increasing electrical separation, thereby indicating that the mutual coupling effect is weakened as the separation increases. The accuracy of the proposed method is verified by comparing the computed results with experiments and simulation using commercial electromagnetics software FEKO.

This paper is concerned with the problem of simultaneously tracking the direction-of-arrival (DOA) of far-field multiple moving sources/users in wireless communications using the vector-signal received by an antenna array of $N$ elements. The antenna array can be rigid (fixed array locations) or flexible (time-varying array locations), and it is used in conjunction with a “manifold extender”, a spatiotemporal state-space model and a Kalman-type tracking approach for non-stationary wireless channels. In particular, two tracking approaches are proposed. The first is based on an arrayed Extended Kalman Filter (arrayed-EKF) algorithm and the second on an arrayed Unscented Kalman Filter (arrayed-UKF) algorithm. Furthermore, if the array is rigid the spatiotemporal state-space model incorporates the DOAs and the angular velocities of the sources, while if it is flexible it also includes the array locations in the set of state-variables. The performance of the two approaches using both rigid and flexible arrays is evaluated using computer simulation studies and compared with a subspace tracking algorithm and a particle filter method under the same conditions. The results show that the arrayed-UKF and the arrayed-EKF show superior tracking performance, especially for low SNRs.

In this article, a dual-polarized planar phased array with high polarization isolation and low cross-polarization is presented operating from 4 to 18 GHz, i.e., 4.5:1. The proposed array is comprised of tightly coupled dipoles with integrated coupled-Marchand baluns. To improve the uniformity of fields distributed on the array, the center-feeding dipole is used in this design instead of the conventional edge-feeding one at first. Then, the outer conductors of the feed are composed of a group of shorted vias with the proper number and position. Based on these methods, the output balance of the balun is significantly improved, resulting in high isolation between ports with different polarization modes. Furthermore, this feed has a natural ability to suppress the D-plane common mode resonance. The capacitive metallic annular plate over adjacent radiating elements and the thick aluminum plate with an air cavity placed under the array are employed together to suppress the in-band coupled-loop modes. The infinite array simulation indicates that the array can achieve transmit (Tx)/receive (Rx) isolation more than 48 dB at broadside. Isolation better than 32 and 30 dB can be achieved when scanning to 45° in E-/H-planes and 60° in E-plane, respectively. The cross-polarization level is below −54 dB at broadside and remains below −29 dB when scanning to 60° in E-plane as well as 45° in H-plane. A $12\times12$ dual-polarized antenna array is fabricated and measured to validate the correctness of this design. This type of antenna can be applied in wideband simultaneous transmit and receive (STAR) monostatic systems.

Introduction. Introduction. Low-profile effective antenna systems (AS) with maintained directional characteristics in a wide sector of scanning angles are required for satellite communication at mobile objects. This article investigates the directional characteristics of a subarray based on a Fabry–Perot cavity and an antenna array with mechanoelectrical beam steering.Aim. To investigate a Fabry–Perot based antenna array with mechanoelectrical beam steering and to estimate its gain and directivity at different scanning angles.Materials and methods. Computer simulations were carried out using the finite element method (FEM), finite difference time domain (FDTD) method and template based post-processing.Results. A subarray based on a Fabry–Perot cavity for an antenna array with mechanoelectrical beam steering was simulated. The efficiency of the subarray comprised at least 65 % in the 11.9…12.5 GHz frequency band. An antenna array based on a Fabry–Perot cavity with mechanoelectrical beam steering was developed and investigated. The calculated characteristics of the developed antenna array agreed well with those obtained experimentally. The gain degradation did not exceed 2.5 dB in the 0…70° scanning angle range. The advantages of using antenna elements based on a Fabry–Perot cavity and developing on their basis mobile satellite antenna systems with wide-angle scanning are noted.Conclusion. The use of a radiator based on a Fabry–Perot cavity and the development on it basis an antenna array with mechanoelectrical beam steering provides an antenna efficiency of no less than 0.5 with a gain degradation of no more than 2.5 dB in the scanning angle range 0…70° from 11.9 to 12.5 GHz.

This paper presents a convolution neural network (CNN)-based direction of arrival (DOA) estimation method for radio frequency (RF) signals acquired by a nonuniform linear antenna array (NULA) in unmanned aerial vehicle (UAV) localization systems. The proposed deep CNN, namely RFDOA-Net, is designed with three primary processing modules, such as collective feature extraction, multi-scaling feature processing, and complexity-accuracy trade-off, to learn the multi-scale intrinsic characteristics for multi-class angle classification. In several specific modules, the regular convolutional and grouped convolutional layers are leveraged with different filter sizes to enrich diversified features and reduce network complexity besides adopting residual connection to prevent vanishing gradient. For performance evaluation, we generate a synthetic signal dataset for DOA estimation under the multipath propagation channel with the presence of additive noise, propagation attenuation and delay. In simulations, the effectiveness of RFDOA-Net is investigated comprehensively with various processing modules and antenna configurations. Compared with several state-of-the-art deep learning-based models, RFDOA-Net shows the superiority in terms of accuracy with over 94% accuracy at 5 dB signal-to-noise ratio (SNR) with cost-efficiency.

A dual-band dual-polarized antenna array is considered to analyze the operating mechanism of the resonant coupling in multiband multiarray antennas, firstly. The considered antenna is composed of a lower band (LB) antenna operating from 690 to 960 MHz and two columns of higher band (HB) subarrays operating from 1690 to 2690 MHz. Then, a novel method of suppressing the resonant coupling interference by using ferrite cores is proposed. It is implemented by loading ferrite cores on the feed cables of the HB elements. The resonant coupling interference is caused by the LB common-mode currents distributed on the HB feed cables. It will seriously distort the LB radiation patterns. With the ferrite cores, the LB common-mode currents are eliminated, and then, the distorted LB radiation patterns are completely restored. Furthermore, the loaded ferrite cores hardly affect the performance of the HB elements.

The traditional common-offset ground penetrating radar method measures point by point along the survey line with a single transmitter and a single receiver. Due to the influence of the antenna radiation power and the low-pass filtering function of the earth medium, an intense amplitude gain cannot be obtained when the signal is intercepted. This article addresses a plane beam signal ground penetrating radar array observation method based on high radiation power gain. The transmitting antenna array simultaneously excites the pulse signal with the same centre frequency. All the transmitted signals interfere with each other at the near surface to form a plane beam signal, and the electromagnetic energy is superimposed mutually to increase the radiation power. We applied the plane beam signal ground penetrating radar array method to different geological models constructed by the finite difference time-domain (FDTD) algorithm for numerical simulation in this research. Since there are various offsets in the array ground penetrating radar observation method, we introduce a composite frequency shift-perfect matching layer (CFS-PML) based on the recursive convolution method as the absorbing boundary condition. It eliminates the problem of secondary reflection caused by the angle variation of the incident wave. The research result shows that the plane beam signal illuminates the target uniformly in space, can eliminate the discontinuity in profile data caused by the directivity of the antenna, improve the stability and quality of the echo signal, and enrich the target response parameters.

Minimum Redundancy Linear Arrays (MRLAs) and Uniform Linear Arrays (ULAs) investigation conducted with the possibility of using them in future 5G smart devices. MRLAs are designed to minimize the number of sensor pairs with the same spatially correlated delay. It eliminates selected antennas from the entire composite antenna array and preserves all possible antenna spacing. MRLAs have attractive features for linear sparse arrays, even if the built-in surface is deformed, it works without problems. To our knowledge, MRLAs have not been applied to smart devices so far. In this work, a 7-element ULAs and 4-element MRLAs (same aperture) were used for the simulation. The Half Power Beamwidth (HPBW) is 0.666 and the Null-to-Null Beamwidth ( ) is 1.385 in ψ-space. In comparison, the standard 4-element arrays are 1.429 and 3.1416, while the standard 7-element linear arrays are 0.801 and 1.795 respectively. Experimental results show that 4-element MLRAs have a narrower mean beam, much higher sidelobes and shallow nulls. Therefore, in terms of main lobe features, 4- elements MRLAs have an improvement over the standard 7-element ULAs. Doi: 10.28991/esj-2021-SP1-05 Full Text: PDF

Context. The aim of the article is to analyze the throughput of the LTE-A mobile network on the uplink using an adaptive linear equidistant antenna array. Objective. Suggestions have been made for the possibility of using adaptive antenna arrays to increase bandwidth in LTE-A mobile networks and analyze the benefits of its use compared to the standard type of base station antenna Method. To achieve this result, a computer model of noise analysis of the mobile network in the form of a flat regular hexagonal antenna array consisting of 7 three-sector cells was developed. To estimate the benefit from the use of adaptive antenna arrays, two options were analyzed: when using a standard antenna array of the LTE-A network, and an adaptive linear equidistant antenna array. During the simulation, 100 random placements of subscribers of useful and interference signals were performed and the minimum, maximum and average gain from the use of adaptive antenna arrays was calculated. The average value of the gain for the adaptive antenna array in the direction of the subscriber station, which generates a useful signal of 5.69 dB more than the standard antenna array of the LTE-A network. At the same time, there is a significant reduction in the gain of the adaptive antenna in the direction of the interference subscriber stations, namely, for those with the highest interference level, the gain is 32.84 dB and 28.33 dB, respectively. To clearly show the gain in the qualitative characteristics of the network, a bandwidth analysis was performed for different types of antennas. The bandwidth distribution (transport block size) for 50 resource blocks using an adaptive equidistant linear antenna array compared to a standard antenna array is presented. Results. It is shown that due to the use of adaptive antenna systems, the average bandwidth increases from 11 Mbit/s to 35 Mbit / s for all types of distribution considered channels. Conclusions. The article proposes the use of adaptive antenna arrays to increase the bandwidth of the LTE-A network. The simulation of bandwidth for 50 resource blocks showed that in the presence of internal system interference when using standard antennas of base stations, the average bandwidth is from 11.2 Mbps to 12.3 Mbps. At the same time, due to the use of adaptive antenna systems, the average bandwidth increases from 11 Mbit/s to 35 Mbit/s for all types of multipath channels considered.