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This article presents a novel compact design of an annular ring microstrip antenna (ARMSA), which has two stacked annular rings and is fabricated on a FR4 substrate for radar and satellite applications. The presence of different kinds of slots made the design of the recommended antenna very unique for Ku band applications. This novel compact structure of the antenna provided enhanced bandwidth and high gain. The suggested antenna works in Ku band and has 2.70 GHz bandwidth and 8.42 dB gain, which makes it suitable for satellite applications. The quality parameters of the proposed annular ring microstrip antenna have been compared with other existing annular ring microstrip antennas, which shows its efficient performance. [ABSTRACT FROM AUTHOR]

An efficient gain-enhancement technique for millimeter wave (mmWave) planar patch antennas (PPAs) using a novel slot-loaded and segmented-cavity backed structure is newly proposed in this study. By incorporating a main radiator with a rectangular slot and employing a muli-layered segemented-cavity, the proposed antenna design significantly increases antenna gain beyond conventional approaches. Unlike traditional patch antennas or those with shorting pin structures, our gain-enhanced PPA utilizes the rectangular slot to electrically expand the radiation aperture, while the addition of substrate integrated pillars acorss multiple segmented ground layers markedly improves antenna directivity. The strategric use of a segmented cavity not only facilitates flexible impedance matching but also ensures consistent performance within the n257 band, accompanied by minimal gain variation. To verify the gain enhancement from the conventional patch, the proposed antenna was fabricated with a size of 1.03 λ0 × 1.03 λ0 × 0.1 λ0 at 28 GHz. The measured 10-dB impedance bandwidth was 12.14 % with a maximum measured gain of the 11.28 dBi at 28 GHz. Compared to the measured gain of the conventional PPA with the same size, the gain was 39.6 % higher, which represents the highest gain per total antenna volume observed for a single PPA in the mmWave spectrum for high-gain applications, to the best of our knowledge.

Open resonant cavity antenna (ORCA) and its recent advances promise attractive features and possible applications, although the designs reported so far are solely based on the classical electromagnetic (EM) theory and general perception of EM circuits. This work explores machine learning (ML)-assisted antenna design techniques aiming to improve and optimize its major radiation parameters over the maximum achievable operating bandwidth. A state-of-the-art method, e.g., parallel surrogate model-assisted hybrid differential evolution for antenna synthesis (PSADEA) has been exercised upon a reference ORCA geometry revealing a fascinating outcome. This modifies the shape of the cavity which was not predicted by EM-based analysis as well as promising significant improvement in its radiation properties. The PSADEA-generated design has been experimentally verified indicating 3dB-11dB improvement in sidelobe level along with high broadside gain maintained above 17 dBi over the 18.5% impedance bandwidth of the ORCA. The new design has been theoretically interpreted by the theory of geometrical optics (GO). This investigation demonstrates the potential and possibilities of employing artificial intelligence (AI)-based techniques in antenna design where multiple parameters need to be adjusted simultaneously for the best possible performances.

Antennas with complex radiation characteristics can enhance the adaptability of radiofrequency systems in complex electromagnetic environments. However, The realization of complex targets is extremely challenging for conventional antenna design methods. It is difficult to find a suitable initial topology of the antenna with complex radiation characteristics. Therefore, in this paper, topology optimization is used to explore the initial structure with complex radiation properties. A two‐dimensional lossy thin layer model based on the transitional boundary condition is constructed, and target field functions for complex radiation are proposed. To verify the effectiveness of the algorithm, a high gain antenna with 10.2 dBi is realized, which has the highest aperture efficiency compared with the literature in similar directions. Then, for more complex targets, the radiation patterns of arbitrary direction null, arbitrary direction beam, and equal‐amplitude dual beam are realized, respectively. The topology optimization algorithm provides a new approach for the design of complex multitarget antennas. [ABSTRACT FROM AUTHOR]

This paper presents a simple, low-profile rectangular microstrip patch antenna operating in the V-band for WiGig applications. The initial design involves a rectangular microstrip patch antenna modified by inserting a small circular slot into the radiating patch to adjust the resonance at 60 GHz and enhance its reflection coefficient performance. To support the proposed structure, a fully grounded Rogers RT/Duroid-5880 dielectric substrate, having a dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.12 mm, is employed. The final design measuring 4 x 7.4 x 0.12 mm³ attains a stable gain above 10.33 dBi over the operational band with a maximum realized gain of 10.61 dBi and a minimum S11 value of – 60 dB at the center frequency. Likewise, the proposed antenna achieves a minimum VSWR of 1.026. In addition, the antenna realizes an impedance bandwidth of 2.22 GHz extending from 58.809 GHz to 61.029 GHz and a radiation efficiency above 89%. The CST is utilized for antenna design, simulations, and optimizations, while HFSS validates the simulation results. The simulation outcomes from both software simulators indicate a good level of agreement. Keywords: V-Band, Compact antenna, High gain antenna, Circular slots, WiGig ap [ABSTRACT FROM AUTHOR]

This article describes the design and fabrication of a 4 × 4 MIMO antenna array intended for operation at 60 GHz. The antenna comprises of half-circular p-shaped radiator connected with a microstrip line printed on the Rogers 4003 substrate of area 22.5 × 22.5 mm2 with εr, thickness, and tan δ of 3.5, 0.203 mm, and 0.0027, respectively. This single radiator is doubled and connected to the power divider to obtain a 1 × 2 antenna array for gain enhancement purposes. The array model is duplicated on the same substrate to achieve 2 ports and 4 ports MIMO antenna. Thereafter, the model is experimentally fabricated and tested to validate the simulated results. The measured results demonstrate the antenna's 60 GHz operating bandwidth extended from 57 GHz to 63 GHz and with insertion losses ≤ −30 dB between ports (1,2) and (1,4) (the orthogonal ports), while it equals around ≤ −23 dB between ports (1,3) (the mirrored ports) within the achieved band with good consistency between both simulated and tested results. Also, it has achieved a gain of more than 9 dBi at 60 GHz with a broadside radiation pattern in both planes. Furthermore, the MIMO parameters are also carried out (ECC, DG, CCL, MEG, and TARC). The ECC is below 0.0025, the DG is approximately 10 dB, the CCL is below 0.2 bits/s/Hz, the MEG is −3 dB and the TARC is below −10 dB over the achieved frequency band. All the MIMO parameters are investigated to prove the diversity characteristics of the antenna array which supports the antenna to be suitable for the 60 GHz communication.

In the realm of mmWave communication and connectivity, integrating chips and antennas into a cohesive system is paramount. Given this, planar antenna arrays have become indispensable. In this article, we introduce a novel antenna array tailored for mmWave applications, characterized by its high directivity. Distinctively, this new array employs a flat-panel radiator, ensuring an augmented gain without necessitating additional superstrate layers. To validate its potency, a 4 × 4 flat-panel array with dimensions of 3.74 λ0 × 3.74 λ0 × 0.106 λ0 at 28 GHz including a ground plane was designed and tested for n257 band. The standalone array element exhibited a bandwidth of 20.6%, centered at 28.5 GHz. Furthermore, a 1 × 16 mmWave feed network was designed and amalgamated with the array elements to assess the comprehensive antenna performance. The measured peak gain of 21.3 dBi at 28.5 GHz was observed with the measured half power beamwidth of 15° while the gain variation within the operation band was less than 3 dB. [ABSTRACT FROM AUTHOR]

This letter presents a design of a high gain uniplanar end‐fire electrically small antenna. The design starts from an equivalent antenna of an antenna array with two half‐wavelength dipoles, which consists of two linear strips and produces the end‐fire unidirectional radiation. Two U‐shaped strips are utilized to replace the linear strips, which makes the antenna compact. In addition, a spilt‐ring resonator is loaded to make the realized gain of the electrically small antenna increase by ~2 dB. An antenna prototype is fabricated and measured. The measurements reveal that the proposed antenna has a peak realized gain of 6.02 dBi and a front‐to‐back ratio of 12.71 dB at its resonance frequency of 747.8 MHz. Its size is only 0.254 λ0 × 0.184 λ0 × 0.0037 λ0, and ka = 0.984. The measured realized gain exceeds both the Harrington and Kildal–Best ka‐based upper limits. [ABSTRACT FROM AUTHOR]

This paper presents a waveguide–slot antenna to generate a radiation beam with high gain fed by a low-loss feeding network at 110 GHz. The proposed antenna consists of a compact eight-way power divider and a waveguide–slot array. The eight-way power divider provides equal-amplitude and alternative-phase excitation for the slot array, and each of them supports two waveguides. The integral structure is implemented by two layers with a channeled substratum and a slotted superstratum. To verify the proposed slot array, the designed array is fabricated with computer numerical control (CNC) milling and measured. The measured peak gain of the designed antenna is 32 dBi at 110 GHz. The proposed antenna with a simple structure provides a promising solution to develop high gain antenna in upper millimeter-wave and sub-terahertz (THz) applications. [ABSTRACT FROM AUTHOR]

This paper proposes an effective planar mmWave switched beamforming antenna array with low complexity and wide beam coverage. The proposed structure is configured using multiple linearly polarized self-beam-tilting-antenna (SBTA) elements, eliminating the requirement of a phase-adjustable block for beamforming. Each SBTA element can generate different main beam directions by itself without using complicated feed networks. Moreover, unlike typical Butler matrix-based beamforming arrays, the proposed SBTA array does not require passive hybrid couplers to adjust the phases for beamforming operations. Accordingly, the proposed feed network-less antenna avoids circuit complexity, feed network insertion losses, or increases in size and fabrication costs, rendering it suitable for mmWave compact antenna applications. To verify the proposed concept and beamforming performance, a 1 × 4 SBTA array was fabricated at 28 GHz using a conventional printed circuit board (PCB) process. The size of the fabricated antenna (excluding test connectors) was 1.12 λ0 × 1.68 λ0 × 0.08 λ0 (λ0 for free-space wavelength), and the measured 10-dB impedance bandwidth was approximately 5.9 %. Furthermore, the measured main beam switching directions were found at −34°, −52°, +51°, and +38° with measured gains of 6.7, 6.1, 5.9, and 6.6 dBi, respectively, at 28 GHz.

In this paper, a fractal antenna is proposed for wideband application. It has a resonance frequency of 5 GHz, and has been designed using an FR4 substrate with a width and a length of 40 mm and patch with a width, length of 35.288 mm. The proposed antenna has been made with five iterations, and the result obtained multiband behavior and agrees with the various efficient wireless applications. In the proposed antenna, there are four bands response at frequencies 1.6, 2.9,5.2, and 6 GHz, and bandwidth percentage are 4.56%, 7.89%, 12.13%, and 4.6%. It also covers application in 1.5–1.7, 2.8–3.1, 4.8–5.4, and 5.9–6.2 GHz. The gain and the directivity of the proposed antenna is measured as 15.885 dBi greater than other fractal antennas to date, and 7.422 dBi respectively. The proposed antenna has been implemented successfully using IE3D and the result has been tested successfully using a key sight vector analyzer. [ABSTRACT FROM AUTHOR]

This paper proposes an effective planar mmWave switched beamforming antenna array with low complexity and wide beam coverage. The proposed structure is configured using multiple linearly polarized self-beam-tilting-antenna (SBTA) elements, eliminating the requirement of a phase-adjustable block for beamforming. Each SBTA element can generate different main beam directions by itself without using complicated feed networks. Moreover, unlike typical Butler matrix-based beamforming arrays, the proposed SBTA array does not require passive hybrid couplers to adjust the phases for beamforming operations. Accordingly, the proposed feed network-less antenna avoids circuit complexity, feed network insertion losses, or increases in size and fabrication costs, rendering it suitable for mmWave compact antenna applications. To verify the proposed concept and beamforming performance, a 1 × 4 SBTA array was fabricated at 28 GHz using a conventional printed circuit board (PCB) process. The size of the fabricated antenna (excluding test connectors) was 1.12 λ 0 × 1.68 λ 0 × 0.08 λ 0 (λ 0 for free-space wavelength), and the measured 10-dB impedance bandwidth was approximately 5.9 %. Furthermore, the measured main beam switching directions were found at −34°, −52°, +51°, and +38° with measured gains of 6.7, 6.1, 5.9, and 6.6 dBi, respectively, at 28 GHz. [ABSTRACT FROM AUTHOR]

A wideband periodic leaky-wave antenna (LWA) is proposed in this paper. By using lossy dielectric material inside the wedge-like guide as medium for wave propagation, a leaky mode is excited and results in widening the bandwidth. For certain tangential losses, this leaky-wave antenna achieves 20.34% 3-dB gain bandwidth with maximum gain of 19.7 dBi. The antenna experiences low side lobe level (SLL) in general and low cross-polarization over the operating frequency, making the antenna suitable for millimeter-wave (mm-wave) applications.

This article proposes a high‐gain quasi‐Yagi antenna using nested metaresonator structures with a systematic design approach. The nested metaresonators are used as a director element instead of conventional strip directors. The gain enhancement of the proposed antenna is based on strong electromagnetic coupling between the driver and metaresonator director elements. The proposed antenna has a gain of 7.6–9 dBi with a bandwidth of 8.6% between 2.43 and 2.65 GHz (S11≤−10 ${S}_{11}\le -10$ dB). It achieves a maximum gain increase of 4 dBi compared to the conventional quasi‐Yagi antenna and 2 dBi compared to the four‐director quasi‐Yagi antenna. The proposed antenna can be used for wireless communication applications that require high gain. [ABSTRACT FROM AUTHOR]

In this article, a single-layer frequency selective surface (FSS)-loaded compact coplanar waveguide (CPW)-fed antenna is proposed for very high-gain and ultra-wideband applications. At the initial stage, a geometrically simple ultra-wideband (UWB) antenna is designed which contains CPW feed lines and a multi-stub-loaded hexagonal patch. The various stubs are inserted to improve the bandwidth of the radiator. The antenna operates at 5–17 GHz and offers 6.5 dBi peak gain. Subsequently, the proposed FSS structure is designed and loaded beneath the proposed UWB antenna to improve bandwidth and enhance gain. The antenna loaded with FSS operates at an ultra-wideband of 3–18 GHz and offers a peak gain of 10.5 dBi. The FSS layer contains 5 × 5 unit cells with a total dimension of 50 mm × 50 mm. The gap between the FSS layer and UWB antenna is 9 mm, which is fixed to obtain maximum gain. The proposed UWB antenna and its results are compared with the fabricated prototype to verify the results. Moreover, the performance parameters such as bandwidth, gain, operational frequency, and the number of FSS layers used in the proposed antenna are compared with existing literature to show the significance of the proposed work. Overall, the proposed antenna is easy to fabricate and has a low profile and simple geometry with a compact size while offering a very wide bandwidth and high gain. Due to all of its performance properties, the proposed antenna system is a strong candidate for upcoming wideband and high-gain applications. [ABSTRACT FROM AUTHOR]

A high gain antenna with Mu-near-zero metasurface (MNZ-MS) is introduced in this work. The proposed antenna can be utilized for future 5G applications. The patch antenna is designed on the upper face of the square substrate with a ground plane at the bottom face. To improve the antenna gain, a layer of MNZ-MS unit cells is placed above the antenna substrate with 0.48 λ 0 air space between the two layers, where λ 0 is the wavelength in free space at the resonance frequency of 26.3 GHz. The MNZ-MS layer consists of four double-sided split square resonators. The overall thickness of the proposed antenna is 0.66 λ 0. To approve the execution of the proposed antenna, a prototype model is manufactured and tested. The outcomes fulfill a reflection coefficient lower than −10 dB over the frequency spectrum of 26–28 GHz. A gain improvement better than 5 dB is obtained compared to the gain of the reference patch at the center frequency of 26.3 GHz. [ABSTRACT FROM AUTHOR]

Studying the geometry of electromagnetic band gap (EBG) structures in 1 and 3 dimensions is useful for achieving effective directional radiation, high gain, and side-lobe attenuation of antennae. This paper presents an EBG antenna, whose radiating source is a rectangular notched patch, which can be used for applications around 20 GHz. Two conventional woodpile dielectric structures with a triangular lattice are presented in a comparative study to extract the best physical and electromagnetic performance in terms of directivity, bandwidth, and gain; these are the square and the cylindrical rods. These two structures' electromagnetic and geometrical limits allow the design of a 3D EBG structure called an icosahedral structure. The proposed antenna is composed of different ceramic substrates (the Arlon AR 450, (h = 0.48 mm, ɛr = 4.5, El Tand = 0.0035) on which the radiating element is placed, the Rogers TMM 13i, (ɛr = 12.85, El Tand = 0.0019) for the 3D icosahedral structure; and the Taconic TLY-5A, (ɛr = 2.17, El Tand = 0.0009) for the 1D lateral walls). With a substrate-plated radiation source coupled with a 3D icosahedral structure and surrounded by a vertically mounted 1D structure, a directivity of 19 dBi was obtained with a realized gain of 17.7 dB and an optimal coupling (antenna–EBG material) at 19.8 GHz. These results are encouraging given the antenna size of 33.41 × 27.87 × 37.36 mm3. [ABSTRACT FROM AUTHOR]

In the realm of mmWave communication and connectivity, integrating chips and antennas into a cohesive system is paramount. Given this, planar antenna arrays have become indispensable. In this article, we introduce a novel antenna array tailored for mmWave applications, characterized by its high directivity. Distinctively, this new array employs a flat-panel radiator, ensuring an augmented gain without necessitating additional superstrate layers. To validate its potency, a 4 × 4 flat-panel array with dimensions of 3.74 λ0 × 3.74 λ0 × 0.106 λ0 at 28 GHz including a ground plane was designed and tested for n257 band. The standalone array element exhibited a bandwidth of 20.6%, centered at 28.5 GHz. Furthermore, a 1 × 16 mmWave feed network was designed and amalgamated with the array elements to assess the comprehensive antenna performance. The measured peak gain of 21.3 dBi at 28.5 GHz was observed with the measured half power beamwidth of 15° while the gain variation within the operation band was less than 3 dB.

This paper presents a waveguide–slot antenna to generate a radiation beam with high gain fed by a low-loss feeding network at 110 GHz. The proposed antenna consists of a compact eight-way power divider and a waveguide–slot array. The eight-way power divider provides equal-amplitude and alternative-phase excitation for the slot array, and each of them supports two waveguides. The integral structure is implemented by two layers with a channeled substratum and a slotted superstratum. To verify the proposed slot array, the designed array is fabricated with computer numerical control (CNC) milling and measured. The measured peak gain of the designed antenna is 32 dBi at 110 GHz. The proposed antenna with a simple structure provides a promising solution to develop high gain antenna in upper millimeter-wave and sub-terahertz (THz) applications.

This paper presents the design of wideband and high gainFrequency Selective Surface (FSS) loaded antenna for ultra-wideband (UWB) wireless applications requiring high-gain. The antenna consists of a monopole and an FSS reflector. Initially, a conventional rectangular monopole antenna is modified using slot and stub to achieve wide operational bandwidth and size reduction. This modified antenna shows 50% miniaturization compared to a primary rectangular monopole, having a wide impedance bandwidth of 3.6-11.8 GHz. Afterward, an FSS is constructed by the combination of circular and square ring structures. The FSS array consisting of 8×8-unit cells are integrated with the antenna as a reflector to enhance the performance of the proposed miniaturized UWB antenna. The loading of FSS results in an improvement of at least 4 dBi gain in the entire operational bandwidth. Moreover, the antenna's bandwidth is also increased at the lower frequency band due to the presence of the FSS. A prototype of the antenna is fabricated and tested to verify the simulation results. The simulation and measurement results show that the antenna offers a wideband -10 dB impedance bandwidth ranging from 2.55-13GHz with a stable peak gain of 8.6 dBi and retains the radiation pattern stability. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of antipodal Vivaldi antennas (AVAs) for breast cancer detection. In order to enhance the antenna gain, different techniques such as using the uniform and non-uniform corrugation, expanding the dielectric substrate and adding the parasitic patch are applied to original AVA. The design procedure of two developed AVA structures i.e., AVA with non-uniform corrugation and AVA with parasitic patch are presented. The proposed AVAs are designed on inexpensive FR4 substrate. The AVA with non-uniform corrugation has compact dimension of 50×50mm2 or 0.28λL×0.28λL, where λL is wavelength of the lowest operating frequency. The antenna can operate within the frequency range from1.63GHz to over 8 GHz. For the AVA with parasitic patch and uniformcorrugation, the overall size of antenna is 50×86mm2 or 0.24λL×0.41λL. It can operate within the frequency range from 1.4GHz to over 8 GHz. The maximumgain forAVA with non-uniform corrugation and AVA with parasitic patch and uniform corrugation are 9.03 and 11.31 dBi, respectively. The corrugation profile and parasitic patch of the proposed antenna are optimized to achieve the desired properties for breast cancer detection. In addition, the proposed AVAs are measured with breast phantom to detect cancerous cell inside the breast and the performance in detecting cancerous cell are discussed. Themeasured result can confirmthat the proposedAVAs can detect unwanted cell inside the breast while maintaining the compact size, simple structure and low complexity in design. [ABSTRACT FROM AUTHOR]

This paper presents a method for sidelobe level (SLL) reduction, return loss improvement, and bandwidth enhancement in notch-loaded TM30 mode rectangular patch antennas. In this method, a fractal-slot is introduced in the center of notch-loaded patch to remove the unwanted out-of-phase current regions. It is shown that a combination of the fractal-slot and notch loading technique can achieve significant improvement in SLL, return loss, and bandwidth of notch-loaded TM30 mode without compromising gain or symmetry of radiation patterns. Moreover, the method also gives an additional degree of freedom to improve the impedance matching without changing the feed location. A prototype of the antenna is fabricated to verify the proposed method. The proposed antenna shows a measured gain of 13 dBi with a low SLL of −16 dB. Furthermore, it shows symmetrical patterns in both planes with cross-polarization (X-pol) levels of less than 35 dB. An under-sampled $4\times 4$ array of the proposed antenna is also presented by utilizing its low SLL property to simplify the complexity of feed networks in high gain array antennas. The array offers the same directivity and SLL as that of an $8\times 8$ array of fundamental mode rectangular patch elements in the same area.

This paper presents the design of a flat-panel metasurface reflectarray antenna fed by a circular horn antenna for satellite applications. A metasurface-based reflectarray antenna is similar to a flat-panel reflector and is characterized by a reflection angle adjustment that is free from the well-known Snell's law. This was done by compensating the angle of the incident wave using the structure of each unit cell. A unit cell of the designed metasurface is composed of a dual-ring resonator. Many satellites use a reflectarray antenna due to its flat-panel structure and the capability of steering the reflection angle of the incident wave. This paper presents the detailed design procedure using a commercial 3D EM simulator and the operation principle of the flat-panel metasurface reflectarray antenna, including the simulation setup, design environment and automation. The proposed design method is scalable to any EM solvers for numerical analysis. A reflectarray composed of a 16 × 16-unit cell array at 5.8 GHz (C-band) was designed and validated by measurement as a proof of concept. It is excited by a low-cost linearly polarized circular horn cantenna. The measured antenna gain and radiation patterns show good agreement with the simulation. The measured antenna gain of the reflectarray was 22.4 dBi (cross-pol suppression level: 36 dB), and the reflection angle was 15° at normal incidence. [ABSTRACT FROM AUTHOR]

The design and development of a small-sized, high gain ultra wide band (UWB) antenna based on different substrate materials are presented for on body wireless body area network (WBAN) applications. In the present scenario, on-body wearable antennas wave propagation and radiation pattern characteristics have been rigorously explored for study along with the growth of wireless body area networks. The major focus of the presented work is to perform comparative analysis of different substrate materials on performance of a novel, small sized, high gain UWB antenna design suitable for on body WBAN applications. The comparative investigation of the effect of different substrates materials i.e. FR4, Jeans, Rubber, Fleece, Polyester and Rogers RT 5880 on the designed antenna performance for has been performed. The FR4 substrate material found to optimum for proposed UWB antenna that has an overall measurement of 30 mm × 35 mm × 1.2 mm, possesses a large impedance bandwidth of 119.3%, and exhibits high gain and directivity. The peak measured gain and directivity are realized as 6.0 dB and 6.739 dBi respectively at 11.1 GHz. The performance parameters results of designed and fabricated antenna have been investigated and found to be in good compliance. The simulation and evaluation outcomes of the fabricated antenna demonstrate the suitability of the presented FR4 based antenna for WBAN utilization to be operable for communication in the UWB band. [ABSTRACT FROM AUTHOR]

A generic field analysis technique for a liquid antenna along with a novel high‐gain structure of water antenna is presented in this article. The antenna design has liquid material as a conducting radiator contained within a tube, placed on a grounded dielectric substrate. This monopole antenna is fed by a coaxial feed, having the radiating pin inside liquid. The antenna is divided into different regions, and boundary conditions are applied to obtain the resultant field equation. The proposed technique is validated using simulated and measured results, with an existing design with seawater as radiator, and helps to predict the E‐field of water antenna in advance to be used as a reconfigurable antenna. Parametric analysis is done to achieve the best antenna design, and a high‐gain water antenna with gain value of 23.53dB, resonating at 2.9GHz having a bandwidth of 1.08GHz is proposed and fabricated. The high gain is achieved by placing a superstrate on top of the structure at a cavity height of 11mm. This seawater monopole antenna delivers broad bandwidth with high gain and is an attractive option to be used as a reconfigurable antenna. [ABSTRACT FROM AUTHOR]

A design of high-gain Fabry-Perot cavity (FPC) antenna is presented with non-uniform frequency selective surface (FSS) superstrate and electromagnetic band gap (EBG) reflecting ground. The non-uniform FSS superstrate and EBG ground are utilized to flexibly control the attenuation constant $\alpha $ over a large antenna aperture while ensuring the resonance condition of the FPC. The uniformity of the amplitude of the aperture field is improved significantly while obtaining appropriate radiation efficiency. Therefore, the high gain and high aperture efficiency can be achieved within a desirable bandwidth. The theoretical gain estimation is conducted to prove the superiority of the proposed antenna over a referenced uniform one. A straight-forward design methodology is proposed based on the radial leaky-wave theory and the modified transverse equivalent network (TEN) model. The non-uniform high-gain FPC antenna with a diameter of $6.6\lambda _{0}$ is designed at the frequency of 15 GHz. Simulated results show that a gain of 24.6 dBi with an aperture efficiency of 67.9% has been achieved. The measured gain is 24.0 dBi with an aperture efficiency of 58.4%. The 10dB return loss bandwidth and 3 dB gain bandwidth are 5.3% and 3.2%, respectively. The proposed antenna overcomes the limit on aperture efficiency and gain of conventional uniform FPC antennas, and the presented methodology can guide the design of two-dimensional non-uniform high-gain FPC antennas.

A novel design approach to high-gain, wideband, dual-resonant, closely-spaced, three-element Yagi-Uda antenna is advanced. The antenna is comprised by a full-wavelength, principal sectorial dipole, a circular metallic flat reflector, and a sectorial director. At first, a multi-source model is developed to predict the initial values of the key antenna parameters, e.g., the flared angle/radius of the director, and the separation between them. Then, as theoretically predicted, numerically simulated and experimentally validated, the flared angles of the principal radiator and the director are eventually determined as 270° and 180°, respectively. They are further tightly coupled at a close separation of 0.024-wavelength to yield relatively compact size and high gain simultaneously. Prototype antenna with a circular metallic reflector successfully exhibits an impedance bandwidth up to about 40%, with in-band maximum gain up to 10.4 dBi and gain fluctuation less than 3 dB. Finally, the antenna is comparatively studied with other Yagi-Uda antennas to highlight its unique wideband and high gain characteristics.

A two-dimensional (2D) periodic leaky-wave antenna (LWA) is proposed in this article. Using dielectric-filled wedge-like waveguide as medium for wave propagation, the quasi-TEM wave inside the guide is leaked through periodic rings of narrow slots, resulting in high gain frequency-dependent beam. Due to the two-dimensional nature of the antenna, along with the slots distribution, the radiation has low side lobe level (SLL) without the need to extend the length of the antenna as in the case of periodic one-dimensional (1D) LWA. The measured gain of the antenna is 20.34 dBi with SLL less than −13 dB and cross-polarization less the −28 dB. The antenna is proposed for millimeter-wave (mm-Wave) applications.

In this article, a single-layer frequency selective surface (FSS)-loaded compact coplanar waveguide (CPW)-fed antenna is proposed for very high-gain and ultra-wideband applications. At the initial stage, a geometrically simple ultra-wideband (UWB) antenna is designed which contains CPW feed lines and a multi-stub-loaded hexagonal patch. The various stubs are inserted to improve the bandwidth of the radiator. The antenna operates at 5–17 GHz and offers 6.5 dBi peak gain. Subsequently, the proposed FSS structure is designed and loaded beneath the proposed UWB antenna to improve bandwidth and enhance gain. The antenna loaded with FSS operates at an ultra-wideband of 3–18 GHz and offers a peak gain of 10.5 dBi. The FSS layer contains 5 × 5 unit cells with a total dimension of 50 mm × 50 mm. The gap between the FSS layer and UWB antenna is 9 mm, which is fixed to obtain maximum gain. The proposed UWB antenna and its results are compared with the fabricated prototype to verify the results. Moreover, the performance parameters such as bandwidth, gain, operational frequency, and the number of FSS layers used in the proposed antenna are compared with existing literature to show the significance of the proposed work. Overall, the proposed antenna is easy to fabricate and has a low profile and simple geometry with a compact size while offering a very wide bandwidth and high gain. Due to all of its performance properties, the proposed antenna system is a strong candidate for upcoming wideband and high-gain applications.

Integrated lens antennas are widely used in high gain and beam steering applications at millimeter-wave frequencies. The ILA has often large height and suffers from significant scan loss. In this article, we demonstrate a low-profile, efficient, and scanloss-reduced integrated metal-lens antenna (IMLA). An IMLA is a combination of a dielectric lens and metal–plate lens. A 16- $\lambda _{0}$ diameter IMLA is designed using the HDPE and 58 stainless steel plates to achieve the $f/d$ of 0.69. The simulated aperture and radiation efficiency of the IMLA are 73% and 92%, respectively. At 76 GHz, the simulated and measured realized gains of the fabricated IMLA are 31.24 and 31 dBi, respectively. The IMLA is designed to steer the main beam to ±30°. The scan loss is reduced by tilting the radiation pattern of the feeds at offset positions along the focal plane. The radiation pattern of the square waveguide feed is tilted using asymmetrical dielectric pins. The asymmetrical dielectric pins reduce the simulated gain scan loss of the IMLA by more than 1.5 dB at 30° steering angle. The simulation results show that the inclination of the feed radiation pattern helps limit the scan loss of the IMLA to 4.1 and 4.3 dB in the H- and E-planes for 30° steering angle, respectively. The measured scan loss of the manufactured IMLA is 3.8 and 6.2 dB in the H- and E-plane, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a 60 GHz connected slots linear-phased array feeding a high-gain semi-symmetric lens antenna. This design provides high gain, broadband, and beam-steering capabilities for gigabit rate access and backhaul communications. The connected slots antenna array (CSAA) is excited at 16× equidistant points which not only yields spatial power combining but also allows the progressive phase changes to steer the beam in ±45° in azimuth plane. To characterize the CSAA-fed lens antenna, four different power splitters are fabricated which steer the main beam in 0, 15, 30, and 45°. The lens is designed in a way to overcome the scan loss and get comparatively higher gain when beam is steered away from the broadside. The measured results show 25.4 dBi maximum gain with 3 dB gain bandwidth covering the full band 57–66 GHz whereas 3 dB beam-steering range is ±45° for all frequencies. Besides, the half power beamwidth is 6 and 10° in elevation (E-plane) and azimuth plane (H-plane), respectively. [ABSTRACT FROM AUTHOR]

In this paper, an output power reconfigurable rectenna array is proposed for the first time to harvest RF energy. The proposed rectenna array can be used to capture abundant RF energy with high conversion efficiency in a wide range of input power levels and load impedance at 1.88, 2.35, 3.5, and 4.9 GHz simultaneously. The output DC power of the proposed rectenna array can be changed exponentially by altering the on-off state of the switches located between the antenna and the rectifier. The measured result shows that the output power is linearly related to the number of opened switches. Therefore, the proposed rectenna array can be flexibly applied to battery-free or low-power-requiring devices according to their different power needs.

By introducing a V‐shaped air slot in antenna substrate, the peak gain can be improved significantly for traditional Vivaldi antennas without size enlargement and additional components. The air slot is conformal to the radiating conductors of the target Vivaldi antenna, and can force the electromagnetic wave to propagate within the central dielectric part between the antenna's opening slot, by decreasing the effective dielectric permittivity of the regions along the radiating conductors. As a result, the wave distributes more evenly within the radiating aperture comparing with the traditional designs, especially at high frequencies, hence the peak gain can be enhanced. In addition, the removal of antenna back substrate is evaluated on radiation characteristics, which can further improve antenna gain and front‐to‐back ratio. For verification, three antennas within operating frequency band from 0.8 to 6.0 GHz are designed with the same dimensions (220 mm × 256 mm) but different configurations. The simulations show that the peak gain increases from 2.0 to 12.0 dBi gradually for the air slot loaded antenna. The gain increment is about 4–6 dB from 4.0 to 6.0 GHz comparing with the one without air slot. A sample antenna with both air slot and removal of back substrate is fabricated and measured. The measured reflection is better than −10 dB from 0.8 to 6.0 GHz, and the measured gains at (0°,0°) direction are from 2.3 to 11.0 dBi. The antenna patterns at high‐band shows that the main lobe in E‐Plane is narrowed successfully after introducing the V‐shaped air slot. The experimental data agree well with the prediction with in‐band radiation efficiency better than 65%. [ABSTRACT FROM AUTHOR]

A superstrate loaded cylindrical dielectric resonator antenna is developed and demonstrated for dual-band circular polarization. The proposed antenna employs a microstrip-fed rotated cross-shaped slot coupling technique for exciting the dielectric resonator (DR). The design is developed in a straight forward way. Firstly, the DR is coupled with a conventional plus-shaped slot and operates in linear polarization mode at 7.4 and 11.2 GHz. Secondly, the slot is rotated by 10° to enable out-of-phase excitation and ensure circular polarization at the above-mentioned frequencies. In the third step, a square dielectric superstrate is placed above the DR which creates multiple reflection and enhance the gain up to ~8 dBi in both the frequencies without affecting other performances. The development stages are discussed in detail. The proposed design is demonstrated through prototype fabrication and characterization. This antenna can be used for X-band satellite communications. [ABSTRACT FROM AUTHOR]

This article describes the design and fabrication of a 4 × 4 MIMO antenna array intended for operation at 60 GHz. The antenna comprises of half-circular p-shaped radiator connected with a microstrip line printed on the Rogers 4003 substrate of area 22.5 × 22.5 mm 2 with ε r , thickness, and tan δ of 3.5, 0.203 mm, and 0.0027, respectively. This single radiator is doubled and connected to the power divider to obtain a 1 × 2 antenna array for gain enhancement purposes. The array model is duplicated on the same substrate to achieve 2 ports and 4 ports MIMO antenna. Thereafter, the model is experimentally fabricated and tested to validate the simulated results. The measured results demonstrate the antenna's 60 GHz operating bandwidth extended from 57 GHz to 63 GHz and with insertion losses ≤ -30 dB between ports (1,2) and (1,4) (the orthogonal ports), while it equals around ≤ -23 dB between ports (1,3) (the mirrored ports) within the achieved band with good consistency between both simulated and tested results. Also, it has achieved a gain of more than 9 dBi at 60 GHz with a broadside radiation pattern in both planes. Furthermore, the MIMO parameters are also carried out (ECC, DG, CCL, MEG, and TARC). The ECC is below 0.0025, the DG is approximately 10 dB, the CCL is below 0.2 bits/s/Hz, the MEG is -3 dB and the TARC is below -10 dB over the achieved frequency band. All the MIMO parameters are investigated to prove the diversity characteristics of the antenna array which supports the antenna to be suitable for the 60 GHz communication., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)

A new design perspective that utilizes the diffracted fields from planar metallic sheets to implement high gain, low profile, and low-cost antenna at 60 GHz is presented. The proposed antenna is matched over the 60-GHz ISM band (57-64 GHz). The proposed antenna can be employed in a linear antenna array with one wavelength distance between the array elements without generating grating lobes. The proposed antenna structure is suitable for short range, low power applications. The proposed antenna is vialess planar structure. The simplicity of the structure is advantageous in relaxing the fabrication process requirements.

In this paper, experimental evaluations over the frequency range of a 57–64 GHz for an improved millimeter wave (MMW) imaging/detection system have been conducted. The main objective behind this work is to examine the performance of a high gain and low profile multi sine corrugated AFTSA antenna sensor in the detection of metallic, non-metallic weapons and suspected liquids hidden by clothing, plywood, and plastics. A microwave holography technique based on time domain reflectometry (TDR), which utilizes amplitude information recorded over a 2D aperture, reconstructs a focused image of the target. 60 GHz ISM band imaging detection experiments elaborate the ability for the detection of concealed weapons or other threatening items placed on a body phantom, easily penetrating clothing material of different thicknesses, as well as able to detect through plywood and plastics. The MMW image is detected using a 2D linear scanning platform which generates XY movement, with a $30\times30$ cm2 mechanical range for the object field of view and oriented perpendicular with respect to a lens focal plane. This work is performed with a cross range resolution of $\delta {x}=\delta {y}= 3$ mm achieving a $100\times100$ pixels MMW image. The mechanical setup scanning method is similar to synthetic aperture array with a single AFTSA antenna element measurement, ideal for investigating the probe for 60 GHz band imaging and in detecting concealed threatening items at security surveillance checkpoints. [ABSTRACT FROM AUTHOR]

A multi‐state high gain antenna based on metasurface is proposed. The antenna is composed of two stacking layers and a ground plane. The metasurface is constituted by two layers with the same size. And both of the two layers contain a copper patch array which is formed by 4 × 4 square copper cells uniformly distributed along x and y directions. The metasurface antenna is excited by the aperture coupled structure. The structure is consists of an anomaly microstrip line and a narrow slot etched in the ground plane. Genetic algorithm (GA) is adopted to optimize all the parameters and obtain the best performance of the metasurface antenna. By appropriately choosing the dimensions of the antenna, the proposed antenna can be achieved with the impedance bandwidth (RL≥10 dB) of about 340 MHz (7.8% at 4.36 GHz), 180 MHz (3.6% at 5.02 GHz), and 2800 MHz (41.1% at 6.81 GHz). The peak gain of the proposed antenna is 10.1dBi, 6.9 dBi, and 10.5dBi at 4.26 GHz, 5 GHz, and 7 GHz. In addition, the proposed metasurface antenna can work in multistate, which makes it an excellent candidate for practical applications. [ABSTRACT FROM AUTHOR]

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This paper presents a beam steerable low-profile lens antenna with a flat top wide beam and a high gain operating at 10.10 GHz. It consists of a graded index metasurface (GIMS) lens placed on the top of a microstrip patch antenna (MPA) radiator. An ultrathin linear graded index metasurface (LGIMS) and a radial graded index metasurface (RGIMS) lens were designed for the magnitude and phase transformation of the radiated beam from the microwave radiator. First, an LGIMS lens antenna was designed by placing an LGIMS on the top of an MPA radiator at an optimum height. A maximum measured gain of 16.37 dBi indicating a maximum gain enhancement of 11.50 dB with beam steering in a conical plane with a vertex angle of 84° was observed. Next, a flat top beam (FTB) antenna with a stable gain band was designed by placing an RGIMS on top of an LGIMS lens antenna. The measured peak gain of 14.82 dBi with an FTB pattern having a 1 dB gain variation range of about 96° is observed. Furthermore, the movement of the LGIMS and the RGIMS on top of the radiator results in continuous beam scanning with a maximum gain variation of 1 dB in a conical plane with a vertex angle of about 100°. A maximum gain of 14.82 dBi with a maximum gain enhancement of 10.30 dB at 10.15 GHz was obtained due to the linear and angular movement of the LGIMS and the RGIMS in the FTB antenna. The simulated and measured results are in good agreement. [ABSTRACT FROM AUTHOR]