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 <inline-formula><tex-math notation="LaTeX">Ka</tex-math></inline-formula>-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.
The design of a compact, wideband antenna with omnidirectional radiation pattern is proposed. The antenna occupies a cylindrical volume and is composed of a conducting body of revolution, parasitic ...top ring shorted to the ground plane via a meander line, dielectric material, and two parasitic metallic posts. The conducting body of revolution is employed to act as a wideband feeding structure. The parasitic top ring with the meander line and the dielectric material is utilized to reduce the lowest frequency of operation; hence, size reduction is achieved. The detailed analysis of the antenna performance is provided with the help of vector surface current distribution. The proposed design provides a VSWR lower than 2.5:1 from 0.69 to 3.35 GHz with a bandwidth of 4.86:1. The antenna has a diameter of <inline-formula> <tex-math notation="LaTeX">0.115\lambda _{\mathrm {max}} </tex-math></inline-formula> and a height of <inline-formula> <tex-math notation="LaTeX">0.092\lambda _{\mathrm {max}} </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">\lambda _{\mathrm {max}} </tex-math></inline-formula> is the free-space wavelength at the lowest frequency of operation. An antenna prototype is designed, fabricated, and measured. The measured VSWR is consistent with the simulated one. The measured maximum realized gain varies from 1.3 to 6 dBi. The total efficiency of the proposed antenna is above 80% within the operating band. By excluding the impedance mismatching, the simulated radiation efficiency is found to be above 93%. A good agreement is achieved between simulated and measured far-field radiation patterns.
Compact and lightweight antennas are required for future ground communication systems to provide wide-angle <inline-formula> <tex-math notation="LaTeX">4\pi </tex-math></inline-formula> steradians ...coverage for man-pack radio communication units carried by soldiers on the ground. Two innovative "Bunker" antennas at K-band are described in this article. The novelty includes antenna deployment from folded to unfolded configurations, compact size, low mass, <inline-formula> <tex-math notation="LaTeX">4\pi </tex-math></inline-formula> steradians coverage, low cost, wide bandwidth performance, and built-in radome for protection from severe environmental conditions. Design of these antennas, trades, RF simulations, mechanical design, antenna deployment, and material selection leading to product development are described for the first time in this article. A prototype antenna has been fabricated and measured results are presented. An excellent correlation between measured and simulated patterns has been achieved. The Bunker antenna has very wide frequency bandwidth of 86% covering Ku and Ka secondary frequency bands in addition to its primary K-band and thus could in the future replace three antennas on a dedicated man-pack with a single tri-band antenna solution.
This September issue contains two sets of articles: the Special Issue on Low-Cost Wide-Angle Beam-Scanning Antennas and Regular papers. This Special Issue is motivated by the fact that wide-angle ...beam-scanning antennas are becoming increasingly more important in many applications, including communications, sensing, and automotive.
With the rapid evolution of the wireless communications, fifth-generation (5G) communication has received much attention from both academia and industry, with many reported efforts and research ...outputs and significant improvements in different aspects, such as data rate speed and resolution, mobility, latency, etc. In some countries, the commercialization of 5G communication has already started as well as initial research of beyond technologies such as 6G.MIMO technology with multiple antennas is a promising technology to obtain the requirements of 5G/6G communications. It can significantly enhance the system capacity and resist multipath fading, and has become a hot spot in the field of wireless communications. This technology is a key component and probably the most established to truly reach the promised transfer data rates of future communication systems. In MIMO systems, multiple antennas are deployed at both the transmitter and receiver sides. The greater number of antennas can make the system more resistant to intentional jamming and interference. Massive MIMO with an especially high number of antennas can reduce energy consumption by targeting signals to individual users utilizing beamforming.Apart from sub-6 GHz frequency bands, 5G/6G devices are also expected to cover millimeter-wave (mmWave) and terahertz (THz) spectra. However, moving to higher bands will bring new challenges and will certainly require careful consideration of the antenna design for smart devices. Compact antennas arranged as conformal, planar, and linear arrays can be employed at different portions of base stations and user equipment to form phased arrays with high gain and directional radiation beams. The objective of this Special Issue is to cover all aspects of antenna designs used in existing or future wireless communication systems. The aim is to highlight recent advances, current trends, and possible future developments of 5G/6G antennas.
With the increasingly multiple-input multiple-output (MIMO) applications in ultra-wideband (UWB) communication systems, antenna researchers face big challenges in designing compact operational ...geometries that meet the essential demand of achieving high isolation among antenna elements over the ultra-wide operating bandwidth. Disposed antenna elements orthogonally are seen to be the most common methodology to reduce mutual coupling of MIMO antenna by exploiting polarisation diversity performance. In such configuration, the mutual coupling mainly depends on the inter-element spacing, which it may not be in line with the compact structure. In this Letter, taking the advantages of symmetry of planar UWB antennas, asymmetric feeding scheme miniaturising technique is utilised to improve the inter-element isolation of a reference MIMO antenna made up of four previously designed slot antenna elements, closely-disposed orthogonally. Analytical results have validated the design concept and the improved MIMO antenna using the halved-chopped elements, showing good performance in terms of impedance matching, isolation, radiation features, signal correlation, and system fidelity factor.
A novel coaperture antenna based on the concept of mode composite transmission line and named mode composite antenna (MCA) is proposed in this communication. The MCA combines the structure of a ...monopole antenna and a substrate integrated waveguide (SIW) slot antenna to form a new coaperture antenna. Because of the structure sharing characteristic in MCA, it can reduce the size of the antenna. The MCA serves as the monopole antenna supporting the surface current on the antenna patch in its low-band operation. In its high-band operation, the SIW will support TE 10 to excite the slot array. The two-mode operation has high isolation which makes the MCA a promising candidate for multiband application. The measured and simulated results agreed well and validated the feasibility of the MCA.
Wireless capsule endoscopy (WCE) systems are used to capture images of the human digestive tract for medical applications. The antenna is one of the most important components in a WCE system. In this ...paper, we present novel small antenna solutions for a WCE system operating at the 433 MHz ISM band along with a link budget analysis. The in-body capsule transmitter uses an ultrawideband outer wall conformal loop antenna, whereas the on-body receiver uses a printed monopole antenna with a partial ground plane. A colon-equivalent tissue phantom and CST Gustav voxel human body model were used for the numerical studies of the capsule antenna. The simulation results in the colon-tissue phantom were validated through in vitro measurements using a liquid phantom. According to the phantom simulations, the capsule antenna has −10 dB impedance matching from 309 to 1104 MHz. The ultrawideband characteristic enables the capsule antenna to tolerate the detuning effects due to electronic modules in the capsule and due to the proximity of various different tissues in gastrointestinal tracts. The same design methodology was applied to on-body antennas followed by in vitro and ex vivo measurements for validation. The on-body antenna exceeds −10 dB impedance matching from 385 to 502 MHz both in simulations and measurements. The path loss for the radio link between an in-body capsule transmitter and an on-body receiver using our antenna solutions, in simulations and measurements, is less than 50 dB for any capsule orientation and location, ensuring sufficient signal level at the receiver, hereby enabling an improved capsule endoscope.
This article presents a new type of hybrid antenna that combines the multiresonant modes produced by a liquid dielectric resonator antenna (DRA) and a magnetoelectric (ME) dipole. Such a combination ...could not be easily realized by using conventional solid dielectrics due to fabrication and air-gap problems. An aperture-fed ME dipole for 4.1-5.3 GHz is firstly designed using a standard structure and a relatively small dimension. Then, a hybrid antenna is built by loading the ME-dipole with an aperture-fed cylindrical liquid DRA. Without increasing the antenna size and/or modifying the ME-dipole structure significantly, the hybrid antenna has realized a much wider bandwidth from 2.45 to 5.3 GHz after loading the liquid material. Moreover, it is found that the resonances of the ME-dipole are not simply shifted to lower frequencies after using the dielectric loading, it has strategically combined the multiple resonances of the electric dipole, magnetic dipole, DRA, and feeding slot. The mode combination principle and design guideline have been presented. As an example, a prototype of the proposed hybrid antenna has achieved a 73.5% fractional bandwidth with an electrical size of <inline-formula> <tex-math notation="LaTeX">0.66\times 0.66\times 0.16\,\, \boldsymbol {\lambda }_{\mathbf {0}}^{3} </tex-math></inline-formula> at the center frequency (3.88 GHz), over 5 dBi (up to 7 dBi) broadside gain, total efficiency >80%, and beamwidth around 80°-120° across the frequency band. The proposed hybrid antenna has advantages in terms of wide bandwidth, smaller size, and simple structure compared with other ME-dipoles and traditional wideband antennas. The idea of this antenna design could be extended to other ME-dipole and DRA structures.
This article describes a dual-polarized and high-gain shared-aperture antenna operating in <inline-formula> <tex-math notation="LaTeX">{X} </tex-math></inline-formula>- and Ka -bands. The proposed ...shared-aperture antenna is implemented by combining a folded transmitarray (TA) antenna operating in Ka -band and a Fabry-Perot (FP) cavity antenna operating in <inline-formula> <tex-math notation="LaTeX">{X} </tex-math></inline-formula>-band together. In this configuration, the shared aperture serves as a phase-shifting surface for the TA antenna and as a partially reflective surface for the FP antenna simultaneously. Since both of the two antennas radiate into free space through the same physical aperture, the aperture reuse efficiency of the proposed shared-aperture antenna is 100%. A four-layered, metallic double-ring structure is selected as the unit cell (UC) to implement the shared aperture to fulfill the aforementioned requirements. It is found that the frequency responses of the UC in <inline-formula> <tex-math notation="LaTeX">{X} </tex-math></inline-formula>- and Ka -bands are highly independent, which can be controlled separately to facilitate the antenna design and optimization. Two dual-polarized patch antennas operating in <inline-formula> <tex-math notation="LaTeX">{X} </tex-math></inline-formula>- and <inline-formula> <tex-math notation="LaTeX">{K}\text{a} </tex-math></inline-formula>-bands are utilized to enable a dual-polarized manner of the proposed shared-aperture antenna. The simulated results reveal that the proposed shared-aperture antenna has −10 dB bandwidth of 9.8-10.2 GHz and 26.5-29 GHz with the realized gain of 14.8 dBi (at 10 GHz) and 24.4 dBi (at 28 GHz) in two polarizations. All the simulations are experimentally verified.
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