This paper presents a millimeter-wave end-fire dual-polarized (DP) array antenna with symmetrical radiation patterns and high isolation. The DP radiation element is formed by integrating a quasi-Yagi antenna (providing horizontal polarization) into a pyramidal horn antenna (providing vertical polarization), resulting in a DP radiation element with a symmetrical radiation aperture. To efficiently feed the DP element while maintaining high isolation, a mode-composite full-corporate-feed network is employed, comprising substrate-integrated waveguide supporting the TE10 mode and substrate-integrated coaxial line supporting the TEM mode. This design eliminates the need for additional transition structures, achieving excellent mode isolation and a reduced substrate layer number. A 1 × 4-element DP array prototype operating at 26.5–29.5 GHz using low temperature co-fired ceramic technology was designed, fabricated, and measured. The test results indicate that the prototype achieves an average gain exceeding 10 dBi for both polarizations within the operating band. Thanks to the symmetrical DP radiation element and mode-composite full-corporate-feed network, symmetrical radiation patterns for both polarizations are observed in both the horizontal and vertical planes, along with a high cross-polarization discrimination of 22 dB and polarization port isolation of 35 dB.

This paper presents a wideband dual-polarized in-band full duplex antenna which can also suppress the higher order modes. A dual differential capacitive feeding scheme is proposed to increase the isolation between the co-located transmitter and receiver ports. The proposed design uses λ/4 resonators in close vicinity of the radiating patch to provide spurious-free characteristics. Further, a parasitic patch placed above the radiating patch at height “h” is used to enhance the input matching, impedance bandwidth, and gain of the proposed design. The key features of the proposed structure are its wide impedance bandwidth (∼20%), high inter-port isolation (>58 dB) throughout the entire operating frequency range (2.26–2.76 GHz), and simultaneous suppression of higher order modes which makes it a suitable candidate for modern wireless application. Finally, a prototype is fabricated and measurement results are in good agreement with simulation results.

In this paper, we propose a hybrid sparse array design utilizing Delaunay Triangulation algorithm for element positioning and Convex algorithm for element excitation optimization. This Delaunay Triangulation algorithm yields a radiation pattern devoid of grating lobes. Then Convex algorithm is used to optimize the element excitations to further decrease side-lobe-level. The minimum inter-element distance is as large as 8 times of wavelength. The peak-side-lobe-level can be −17.3 dB. Furthermore, beam steering can be achieved with good performance within 80° field-of-view range.

In this work, a compact active integrated antenna based on a highly compatible antenna-in-package (AiP) solution is proposed. It consists of two sections, namely, a cover plate integrated with an antenna and a package backplane that carries a GaN power amplifier (PA) die. The proposed AiP solution not only provides efficient interconnection between the antenna and the GaN PA die while providing physical shielding, but also provides impedance compensation for the die to improve the matching performance. Besides, a plated through hole array is designed inside the package backplane to significantly improve heat dissipation performance. The proposed AiP solution is compatible with radio frequency integrated circuit (RFIC) dies with different pin arrangements. Two prototypes are fabricated and measured for validation. The first prototype is the active integrated antenna based on the GaN PA, which shows an impedance bandwidth of 25.7–28.7 GHz, a peak gain of 31 dBi, and a dimension of 8 mm × 8 mm × 1.7 mm. Another prototype is based on a GaN front-end module (FEM) die integrating the PA and low noise amplifier, which demonstrates better EVM and ACPR than the conventional design with separate antenna and FEM.

A reconfigurable leaky-wave antenna and its application capable of electronically steering the beam within the entire hemisphere is presented. The original antenna is designed as a 1D array of conducting patches on a dielectric substrate coupled by varactors in series with interdigital capacitors. The beam of this antenna is driven by a DC bias that controls the capacitances of the varactor diodes over a frequency range from 8 to 8.2 GHz. Simulations showed a change in the direction of the main radiation pattern within 55° at 8 GHz by varying the varactor capacitances in the range of 0.1 to 1 pF. The maximum gain is 10 dBi and the side lobe level is -10 dB. The fabricated antenna sample operates at an applied DC voltage between 0 and 12 V, which corresponds to varactor capacitances controlled in the range of 1 to 0.15 pF. This gives a range of elevation angles equal to 40°. The application of the antenna in a reconfigurable star-type structure is proposed. The direction of the main lobe of the radiation pattern in azimuth is controlled by switching between the centrally excited eight antenna arrays using PIN diodes. The direction of radiation in elevation is controlled by the DC bias of the varactors of a particular array switched to “ON”. This complex beam steering throughout the hemisphere represents a novel character of the presented antenna. The antenna has a planar structure. Low-cost printed circuit board technology was used for its fabrication.

This article proposes a hexagonal shaped circularly polarized (CP) antenna at ultra-high frequency (UHF) for radio frequency identification (RFID) and X-band applications. Initially, the antenna operates only in X-band and to convert this CP dual-band antenna asymmetric ground plane and four electromagnetic band gap structures are employed. A metasurface consisting of two complementary metamaterial structures is positioned above the patch at a 9 mm distance to enhance the gain and impedance bandwidth in both the bands. The presented antenna whose electrical dimension 0.48 λg × 0.48 λg × 0.02 λg achieves an impedance bandwidth of 796 MHz and of 4.24 GHz in UHF–RFID and X-band spectrum, respectively. The proposed antenna achieves circular polarization and has a bandwidth of 995 MHz and 796 MHz which spans 2.28–3.28 GHz and 10.44–11.24 GHz, respectively, with a 3 dB axial ratio. In addition to these, a stable radiation characteristic with an average gain of 6 dBi at both 2.45 GHz and 11.21 GHz are achieved which makes it suitable for RFID based real time logistic warehousing applications.

A circularly polarized broadband antenna is designed for Wi-Fi 7 applications. The patch antenna is modeled in the shape of G, and the feed position is adjusted to produce the arms with a length difference of λ/4. The G-shaped patch antenna has shown an impedance bandwidth of 5% (6.16−6.48 GHz) and a peak gain of 6.3 dBi. The metasurface is structured with a periodic array of 4 × 4 patches. The metasurface is sandwiched between dielectric substrates beneath the G-shaped patch. The outcome of these combinations has achieved an impedance bandwidth of 41% (4.85−7.37 GHz) and an axial ratio bandwidth of 26% (5.26−6.83 GHz), and the antenna achieved a peak gain of 7.45 dBic.

Designing and developing smart antennas with adaptive radiation characteristics is an integral part for present-day communication systems. The versatile capabilities of Time-modulated fourth-dimensional (4D) antenna arrays can provide that crucial adaptability if properly designed. This work discusses an effective analysis of 4D antenna arrays to achieve less-attenuating radiation patterns with simultaneously suppressed sidelobe and sidebands. The 4D arrays offer an additional benefit over standard arrays in the sense that the requisite amplitude tapering to lower the undesired radiations can be accomplished by controlling only the switch ON times of the radiating elements instead of using attenuators. The idea of splitting pulses by keeping the total switch ON durations constant, is exploited here as an additional degree of freedom for beamforming of all the radiation patterns. The unwanted radiations in terms of sidelobes as well as sideband radiations (SRs) at the fundamental and harmonic frequencies, respectively are simultaneously minimized to improve the radiation efficiencies of the 4D array. To address the conflicting aims for the synthesis of radiation patterns, a wavelet-mutation based heuristic method is also proposed. The multi-objective problem in hand is modulated in to a single objective cost function as minimization problem. The proposed outcomes are reported and compared with other state of the art works related to the same domain. Furthermore, a detailed statistical analysis is also provided to identify the strengths and weaknesses of the proposed approach.

In this paper, a polarization-reconfigurable antenna fed by a coplanar waveguide (CPW) using a stepped structure is presented. The main parts of the proposed antenna consist of a CPW-fed monopole and four branches. After studying and analyzing the structure and mechanism of the antenna, it was found that different polarizations can be generated by adjusting the antenna’s structure. Based on the mechanism, four PIN diodes are utilized and inserted between the four branches and the monopole for the switching. By controlling the ON/OFF states of the four PIN diodes, the antenna can switch among left-hand circular polarization (LHCP), right-hand circular polarization (RHCP), and linear polarization (LP). The optimized antenna has been fabricated and measured. Measured results indicate that the antenna’s −10-dB impedance bandwidth for LP is 15.93%, covering the frequency range from 2.3 to 2.71 GHz. The overlap bandwidth of −10-dB impedance and 3-dB axial ratio for the LHCP mode is 18.96%, covering frequencies from 2.1 to 2.54 GHz. For the RHCP mode, the overlap bandwidth is 20.5%, covering frequencies from 2 to 2.52 GHz. At all the three polarization modes, the antenna is capable of covering the 2.4-GHz WLAN band (2400–2480 MHz) as well as the LTE TD 2300 band (2300–2400 MHz).

This paper presents a notched ultra-wideband antenna designed to suppress interference from narrowband communication systems. The antenna features a defected ground structure and a stepped microstrip feedline for improved impedance matching and enhanced bandwidth. A bent slot structure is incorporated into the radiating patch to achieve the band-notched characteristic. It has a wide tunable frequency range which allows for flexible adjustment of the notch frequency. Traditional optimization methods, such as numerical analysis, are computationally expensive and inefficient, while heuristic algorithms are less precise. To address these challenges, an improved one-dimensional convolutional neural network (1DCNN-IPS) model is proposed for optimizing the bent slot design more efficiently. The trained 1DCNN-IPS model can accurately predict the antenna’s electromagnetic parameters, reducing mean squared error and training times compared to traditional methods. This provides an efficient and precise solution for antenna structural optimization.

This paper presents an effective approach to a compact antenna system incorporating a single artificial magnetic conductor (AMC), designed to operate in the GSM and WiFi frequency bands. The proposed system features a dual-band AMC single element measuring 60 × 60 mm2 with $\pm90^{\circ}$ bandwidths of 100 and 170 MHz. A comprehensive parametric study was conducted to optimize performance and determine the AMC phase while maintaining the compact size of the antenna system. Significant improvements in gain were observed, from −1.61 to 1.88 dBi at 0.9 GHz and from 3.33 to 5.66 dBi at 2.45 GHz. Additionally, the complete system achieves a compact electrical size of 0.18λ0 × 0.18λ0 × 0.048λ0, with an increased front-to-back ratio of 12.3 and 19.9 dB at both frequencies. Finally, measurements of the fabricated prototype show good agreement with the simulation results.

This paper elaborates the design and analysis of cross-aperture-coupled twin port ceramic radiator. Stimulation of alumina ceramic using a cross slot helps to produce circular waves within 7.35–7.8 GHz. The polarization diversity concept helps to improve the separation level by above 25 dB. Loading of double negative unit cell made metasurface (MS) improves the antenna gain over 11.5 dBi within the working spectrum. Machine learning (ML) techniques, i.e. Decision Tree and Random Forest are utilized to predict the |S11|/Axial ratio parameters. Experimental verification/ML prediction and optimized simulated consequences confirm that the structured radiator works efficiently between 7.21 and 8.2 GHz with over 25 dB isolation between the ports. Directive pattern and decent values of (MIMO) parameters make the radiator applicable for the 6G communication system.

In this article, a simple model is proposed to compute the effective dielectric constant, resonant frequency, quality factors, input impedance, bandwidth and gain of a coaxial probe fed annular ring patch antenna loaded with several dielectric layers. This model is based on conformal mapping technique, cavity model and single resonant parallel R-L-C circuit. The computed values employing the present model are compared with experimental and simulation results. The present model shows good agreement with experimental and simulation results.

This paper presents a low-profile, triple-band elliptical coplanar waveguide-fed antenna designed using the split-ring resonator technique. An artificial magnetic conductor with three zero-phases of the reflection coefficient is incorporated as a reflector to improve the antenna gain. The results show a gain enhancement of 3.4, 5.65, and 1.5 dBi at the three frequency bands of interest centered on 2.45, 5.2, and 8 GHz, respectively. The first two operational bands are Industrial, Scientific and Medical bands (2.33–2.59 and 4.97–5.48 GHz) that can be particularly used for wireless local area network and Bluetooth applications, while the third band (7.48-8.59 GHz) is suitable for military and satellite communications. The proposed solution that is designed, fabricated, and tested exhibits a good agreement between measured and simulated results.

This paper presents the design and implementation of a novel single-fed microstrip hexagonal patch antenna, which operates on 2.4 GHz by employing three-dimensional (3D) printing technologies for circular polarization (CP) with wide 3 dB beamwidth. It was fabricated using a thermoplastic polymer-based material through a 3D printer and subsequently coated with copper. The design of the antenna consists of identical hexagonal slots in mesh grid fashion. These slots are filled with air and perturbations are introduced, by partially filling them with rectangular chunks of the polymer. This produces asymmetry in the substrate layer which leads to the splitting of the degenerate modes of the patch antenna, thus producing CP waves. The presence of volume fraction of air influences the effective permittivity and as a result the axial ratio beamwidth enhances to 176∘. The substrate was created as a double layer, lightweight unit using fused deposition modeling. A copper layer was then added to the underside of the lower substrate to serve as ground. The 3D gain of the antenna is found to be 7.01 dB. The proposed low-profile antenna has the potential to be incorporated in IoT and smart devices, intelligent transport systems, and GPS tracking.

This paper presents the design of a phase gradient metasurface lens (MSL) that enables the orbital angular momentum (OAM) beam convergence alleviating the limitations of the OAM beams in far-field wireless communication. An MSL of a specific constitutive electromagnetic parameter, i.e., relative refractive index, in front of a traditional Uniform Circular Array is designed at 10 GHz. In the presence of the lens, the beam converges from 58∘ to 24∘ for +1 and –1 OAM modes. The proposed MSL can also be used for second-order (±2) OAM modes. The experimental verification performed on the laboratory prototype agrees well with the simulated results. The purity analysis also confirms that the OAM beams passing through the lens maintain high mode purity, thereby not disturbing the phase distribution in the corresponding OAM modes. The designed lens can be used in point-to-point and defense communications.

Accurate absorption analysis of metasurface absorbers, considering all reflected modes, is critical. This corrigendum addresses a significant error in recent papers [19 and 20] as two selected samples, which misinterpret absorption mechanisms by neglecting the main contribution of cross-polarized reflections. According to the review of highly authoritative and highly referenced research, metasurface absorbers with losses can achieve wideband absorption, while low-loss structures typically exhibit resonant narrowband absorption or convert incident power to cross-polarized reflections – an aspect overlooked in [19 and 20]. We present key principles for accurate simulation in HFSS software, emphasizing correct handling of symmetrical and asymmetrical meta-cells and determining all reflected components. Re-analysis of the designs in [19 and 20] using these simulation principles reveals a significant overestimation of reported absorption; they are, in fact, polarization converters rather than perfect absorbers. Finally, we propose potential recommendations for these designs without using a loss mechanism.