A Millimeter-Wave Compact Pattern Reconfigurable Antenna Array With Improved Spatial Coverage

Millimeter-wave (mmWave) antennas and antenna arrays have gained significant attention due to their pivotal role in emerging wireless communication, sensing, and imaging technologies. With the rapid deployment of 5G and the transition toward 6G networks, the demand for compact, high-gain, and reconfigurable mmWave antennas has intensified. This article highlights recent advancements in mmWave antenna technologies, including hybrid beamforming using phased arrays, dynamic beam-steering enabled by liquid crystal and MEMS-based structures, and high-capacity MIMO architectures. We also examine the integration of metamaterials and metasurfaces for miniaturization and gain enhancement. Applications covered include wearable antennas with low-SAR textile substrates, conformal antennas for UAV-based mmWave relays, and high-resolution radar arrays for autonomous vehicles. The study further analyzes innovative fabrication methods such as inkjet and aerosol jet printing, micromachining, and laser direct structuring, along with advanced materials like Kapton, PDMS, and graphene. Numerical modeling techniques such as full-wave EM simulation and machine learning-based optimization are discussed alongside experimental validation approaches. Beyond communications, we assess mmWave systems for biomedical imaging, security screening, and industrial sensing. Key challenges addressed include efficiency degradation at high frequencies, interference mitigation in dense environments, and system-level integration. Finally, future directions, including AI-driven design automation, intelligent reconfigurable surfaces, and integration with quantum and terahertz technologies, are outlined. This comprehensive synthesis aims to serve as a valuable reference for advancing next-generation mmWave antenna systems.

This paper discusses the design of a high gain right-hand circularly polarized millimeter-wave frequency reconfigurable antenna array. The 16-element antenna array is designed to reconfigure its operating frequency over both K- and Ka-bands. More specifically, the reconfigurability is ensured through the integration of a modified ring resonator along with the array’s sequentially rotated stacked feeding network. The ring resonator is designed to reconfigure its operating frequency over four distinct bands with center frequencies at 25 GHz, 26 GHz, 27.75 GHz and 29 GHz, respectively. Such integration enables the proposed millimeter-wave antenna array to exhibit unique radiation characteristics by maintaining circular polarization with an Axial Ratio (AR) < 1 dB in a fractional bandwidth of 37.5% between 21.2 GHz and 31 GHz. A Figure of Merit that takes into account the array’s axial ratio, sidelobe levels and fractional bandwidth is developed to highlight the unique performance of the presented millimeter-wave circularly polarized array in comparison to available work in the literature. The fabricated antenna array shows good agreement with the simulated data where it is found that the measured realized gain exceeds 12 dBic with sidelobe levels of less than −17.5 dB over the various frequency bands of the frequency reconfigurable antenna array.

This paper presents a compact dual-band and dual-polarized millimeter-wave patch antenna array with satisfactory performance on element mutual coupling and beam scanning capabilities. Using capacitive feed technique and stacked configuration with extra parasitic strips, the proposed antenna array is able to achieve a wide operating bandwidth in both the low- and high-bands. In order to reduce the array&#x2019;s footprint, and to enhance the beam scanning performance in both bands, the element spacing is shrunk to less than 0.36 wavelength at 26 GHz. To improve the isolation between array elements due to their small spacings, two effective decoupling approaches are adopted, which result in a 6-dB isolation enhancement. The overall size of the proposed antenna array is only 18.2 mm <inline-formula> <tex-math notation="LaTeX">$\times4.1$ </tex-math></inline-formula> mm <inline-formula> <tex-math notation="LaTeX">$\times1.07$ </tex-math></inline-formula> mm, which is smaller than some industrial mm-Wave antenna modules released recently. Our simulation shows that the antenna array can fully cover the 5G NR bands of n258&#x007E;n261 simultaneously. The four-element array provides &#x00B1;60&#x00B0; and &#x00B1;45&#x00B0; beam scanning performance in the low- and high-bands, respectively. The experimental data of reflection coefficient, mutual coupling, and radiation patterns confirm with the simulated results, rendering the proposed array to be a good candidate for 5G mm-Wave communications.

A test concept is presented for millimeter-wave antennas and arrays using metallic probes inserted in the reactive near-field of the single radiating element. Several probe techniques are disclosed where the disturbance of the antenna radiator feed impedance, typically encountered due to the insertion of the metallic probe into the reactive near-field of the radiator, is negligible. Simulations and experiments show the stable feed impedance and a transmission magnitude from the antenna feed to the probe port of about -20 dB. At the same probe port, the unwanted coupling from neighboring radiator elements is smaller by 10 dB. The technique is applied to patch antennas, planar dipole antennas, and to a class of package-embedded antennas. The advantages of the proposed concept for the production test of millimeter-wave transceiver-integrated antenna array modules are discussed.

We introduce new millimeter-wave corner antenna arrays (MWCA) with eight axially placed printed dipoles fed by an integrated symphase network. The antenna array is placed between two metal plates that make the corner reflector. The antennas were simulated and realized in the frequency range about 26 GHz, which is popular for microwave communication networks. Three antennas, with different H-plane beamwidths (intended for azimuth) of 55', 1100, and 1800, were investigated, simulated, and realized. The bandwidths of all of the antennas were wider than 12%. The losses in all of the antennas were less than 1 dB. The agreement between simulated and measured results was very good. Millimeter-wave corner antenna arrays are low in cost and very simple to realize, and are also suitable for integration.

Bandwidth enhancement of the millimeter-wave high-gain antenna arrays with air-filled waveguide feed networks is investigated in this paper. A novel wideband full-corporate feed network topology composed of X-shaped power dividers arranged in multi-layers is proposed. By combining the feed network with the wideband waveguide-feed horn antenna elements, two arrays with sizes of $8\times 8$ and $16\times 16$ are implemented in the V-band. With the help of the commercial metallic three-dimensional (3D) printing technology, the array geometries can be realized conveniently in a whole piece. Excellent operating performance, including a wide impedance bandwidth of 43% for $|\mathrm{s}_{11|}< -10dB$, a gain of up to 33.9 dBi, and stable and symmetrical radiation patterns are obtained by the $16\times 16$ array. This work offers a new means to enhance the bandwidth of the millimeter-wave antenna array with a large size to more than 40% and proves the feasibility of the metallic 3D printing in 60-GHz antenna array design as well. Benefitted from good performance and ease of realization, the arrays would be a good candidate for future applications in millimeterwave wideband communication systems.

In this paper, a high performance 5G millimeter-wave phased antenna array for 37–40 GHz mobile application is proposed. The proposed antenna array is based on dipole antenna with two opening holes. It is shown that compared to previous designs our antenna array design has good antenna performance in terms of antenna gain and scanning property within the entire frequency range.

A millimeter-wave high-gain dual-polarized antenna array with an enhanced bandwidth is presented. An innovative air-filled differential feeding cavity loaded with a short-ended cross-shaped waveguide is investigated to serve as the feed network and the mode splitter simultaneously of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\,\,\times2$ </tex-math></inline-formula> dual-polarized subarrays. Wideband characteristics and a compact planar size that are desirable for the wideband array design are achieved. Moreover, a wideband dual-polarized waveguide-fed magnetoelectric (ME) dipole antenna with a lightweight self-support geometry and wideband H-plane parallel feed networks with modified dual-layered configurations are proposed, which are convenient to connect with the differential feeding cavity directly. With the use of a commercial metallic 3-D printing facility, the proposed radiating elements, feeding cavities, and feed networks can be combined successfully in a whole piece with a lightweight geometry. The printed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8 \times 8$ </tex-math></inline-formula> array prototype operating in the Ka-band confirms a wide bandwidth of about 30%, a gain of up to 28.5 dBi, and stable unidirectional radiation patterns for the two polarizations. Benefitted from the advantages of the promising wideband dual-polarized radiations and convenience of fabrication, the proposed antenna array would be attractive for millimeter-wave polarization diversity applications.

In this paper, the integration design of a millimeter-wave filtering patch antenna array fed by a substrate integrated waveguide (SIW) four-way anti-phase filtering power divider is proposed. The multilayer four-way anti-phase filtering power divider handily implemented using the intrinsic field distribution of TE 20 -mode in SIW is proposed for miniaturization. The signal of the lower substrate integrated waveguide cavity (SIWC) bandpass filter is directly coupled to the upper TE 20 -mode SIW through a coupling slot. The intrinsic field distribution of TE 20 -mode SIW is used to generate anti-phase signals. This filtering power divider can be utilized as the feeding structure of a millimeter-wave filtering antenna array. To verify the design concept, a 28-GHz SIW-fed 1 × 4 filtering patch antenna array with three-layer substrates is designed and fabricated. The measured results show a fractional bandwidth of 5.03% ranging from 27.15 to 28.55 GHz, a peak gain of 11.1 dBi, cross-polarization levels lower than -20 dB, symmetric radiation patterns in both E-plane and H-plane, and high selectivity.

The increased data traffic and change in the requirements of users paved the way for exploring the unexplored millimeter range of frequencies. These ranges of frequencies are best suitable for communication purposes, especially for 5G applications. Antennas are a key element in communication systems. Since the millimeter-wave antennas possess compact size, multiple antennas are used in the form of an array. The antenna arrays are popularly used since it benefits the performance of output parameters. This paper gives a brief description of millimeter-wave technology and its basic characteristics along with design considerations and design challenges of antennas at millimeter-wave frequency. This paper also covers some of the millimeter-wave antenna and antenna array designs.

This paper proposes a wideband millimeter-wave (MMW) antenna array based on the printed ridge gap waveguide (PRGW). The element of the array consists of a shorted circular patch and a parasitic shorted half annular patch. To improve the impedance bandwidth, the element is fed by using a coupling slot and the distance between the two shorted radiating structure is optimized. Then a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\times 4$</tex> linear array is developed to increase the realized gain. The simulation results indicate that a -10-dB impedance bandwidth of 10.3 % (26.5 ~ 29.5 GHz, center frequency at 28.0 GHz) is realized for the array antenna. Besides, within its operating band, the realized gain of this array is above 10.5 dBi and the peak gain reaches 12.6 dBi.

Millimeter-wave multi-beam antenna arrays with passive beam-forming networks are attractive for future millimeter-wave base stations and mobile devices employing the multiple input multiple output (MIMO) technique owing to their advantages of simple structure, low cost and low power consumption. Several kinds of millimeter-wave multi-beam antenna arrays with one or two dimensional beams were investigated. The patch or the slot antenna was selected as the radiating element of most designs because of their simple geometries and convenience of integration. However, due to the narrow bandwidth performance or the unstable radiation pattern across the operating band, these designs generally suffer from narrow impedance bandwidth or radiation pattern bandwidth. Moreover, most arrays are linearly polarized. As well known, dual-polarized arrays are widely used for wireless communication systems operating at lower microwave frequencies because of significant advantages of polarization diversity and enhancing channel capacity. Therefore, dual-polarized arrays would also be attractive for emerging wireless systems operating at millimeter-wave frequencies. Recently, a new class of wideband antennas designated as the magneto-electric (ME) dipoles was proposed. By applying the concept of complementary antenna, the basic structure consists of a planar electric dipole and a shorted quarter-wave patch antenna working as an equivalent magnetic dipole. The ME dipole has excellent performance including wide impedance bandwidth, nearly identical radiation patterns in two orthogonal planes, low back radiation, low cross polarization, and stable gain over the operating band, and maintains a simple structure as well. In this talk, a novel substrate integrated waveguide (SIW) fed aperture-coupled dual-polarized magneto-electric (ME) dipole antenna will be presented at millimeter-wave frequencies. By applying the aperture coupling as the excitation scheme, the dual-polarized radiations can be easily excited by two sections of SIW located in two layers of print circuit board (PCB). Besides, it has good characteristics including wide bandwidth, high radiation efficiency, symmetrical radiation patterns, low back radiation, low cross polarizations and high isolation between the two input ports. Based on the radiating element, a 2 × 2 dual-polarized two-dimensional multi-beam array working at the 60-GHz band is then designed. Owing to good performances of the ME dipole antenna, the proposed array has wide bandwidth and symmetrical radiation patterns.

This letter presents a common-aperture design scheme of sub-6GHz and millimeter-wave (mm-wave) antennas for 5G metal-rimmed smartphone. The sub-6GHz antenna can form a high-efficiency antenna covering WWAN/LTE multiple bands by referring to the previous scheme of dual-loop structure composed of metal frame and the ground plane of PCB motherboard. The millimeter-wave antenna consists of a connected slot antenna array (CSAA) etched on the top metal frame and a monopole antenna array (MAA) arranged on the top ground clearance region. Due to the end-fire characteristics of connected slot antenna array and the broad-fire characteristics of monopole antenna array, the proposed millimeter-wave antenna for smartphone has good radiation uniformity in three-dimensional space. In addition, a band stop matching circuit are introduced into sub-6GHz antenna and a high pass filter (HPF) are introduced into millimeter-wave antenna to solve the interference problem of millimeter-wave antenna to sub-6GHz antenna in common-aperture design.

This communication describes a novel concept of designing millimeter-wave (mm-wave) dielectric resonator antenna (DRA) arrays, in which the DRA element and part of its feeding network can be codesigned and cofabricated using the printed circuit board technology. Conventionally, the DRA and its feed are designed and fabricated using different dielectric materials. As a result, a large error might take place when mounting the DRA to its feed, which will result in significant influences to the performance of the antenna, especially to those operating in the mm-wave band. The proposed concept of the substrate integrated DRA provides a possibility to minimize the above mounting errors, by shaping the DRA and its feed together using the same material and fabrication process. Two kinds of antenna element, which separately exhibits linear and circular polarization, are designed at Ka-band. In order to demonstrate the feasibility of the proposed elements for array applications, two four-element antenna arrays in cooperation with different feeding networks and transitions are also designed, fabricated, and measured. Investigations show good agreement between simulation and measurement. The proposed substrate integrated DRA array can be easily extended to larger scales and has great potential to be integrated into mm-wave transceiver modules.

Small millimeter-wave antenna designs present particular difficulties when measured. With most available antenna chambers and ranges originally designed for larger size and lower frequencies, physically smaller antennas are dwarfed by the large support structures and cannot be efficiently characterized. Modification of these existing ranges for small antennas and high frequencies may prove to be very difficult as large positional and RF equipment are not easily modified or replaced. Additionally, equipments associated with millimeter-wave antenna measurements such as vector network analyzers, high frequency cable, and adapters, are typically very expensive and often exceed the cost of the rest of the system. With such difficulties, a custom antenna range, designed for the smaller size antennas operating at millimeter-wave frequencies is an attractive and cost-effective solution. In this presentation, a novel portable millimeter-wave bipolar planar near-field antenna measurement system is introduced.