This paper presents a broadband circularly polarized (CP) antenna array for millimeter-wave applications, and the antenna array has the advantages of wide impedance bandwidth (IBW), novel CP design, and low profile. The antenna unit consists of a two-layer substrate and two pairs of magnetoelectric dipoles. Stepped microstrip lines coupled by rectangular slits form a feeder network for easy integration. The axial ratio bandwidth (ARBW) is extended because a pair of parasitic patches is loaded and an elliptical perturbation is added. The simulation results show that the antenna has an ARBW of 18.6% (26.4–31.9 GHz) and an IBW of 45.5% (20.6–32.7 GHz), with a gain greater than 7.11 dBic in the IBW. To improve the gain of the antenna, a 2 × 2 antenna array is designed, fabricated, and measured. The measured results show that the array has an ARBW of 16.6% (26.42–31.21 GHz), an IBW of 41.6% (22.28–33.97 GHz), a peak gain of 13.89 dBic in the IBW, the cross-polarization levels in the xoz-plane and yoz-plane are above 20 dB, and a radiation efficiency greater than 89%.

This paper introduces a tri-band stacked elliptical patch antenna featuring a right-handed circular polarized, designed to operate at the L2, L5, and L1 Global Navigation Satellite System bands. Initially, an elliptic patch is constructed and fed by a probe feed to generate TM110 and TM210 modes at resonance frequencies calculated using Mathieu functions. The probe position is precisely adjusted to excite the quasi-orthogonal mode of TM110 to generate circularly polarized (CP) waves at the L2 and L5 bands. Subsequently, an eye-shaped aperture is engraved into the elliptical patch to enhance the axial ratio (AR) beamwidth in the L2 and L5 bands and stimulate the orthogonal mode of TM210 to produce CP waves at the L1 band. Lastly, a stacked partially elliptical parasitic element is placed beneath the upper slotted elliptical patch to enhance the orthogonality of TM210 surface current versions and thus improve the AR beamwidth at the L1 band. The proposed antenna shows low reflection coefficient values at 1.12–1.33 (L2/L5), and 1.5–1.66 GHz (L1). The AR beamwidths are 133/213∘, 167/163∘, and 36/103∘ at two orthogonal cutplanes at L5, L2, and L1 bands, respectively. The antenna also has decent gains of 6–6.9 dBic across the three bands.

In this study, a high-isolation multiple-input multiple-output (MIMO) microstrip patch antenna (MPA), which utilizes an orthogonal mode cancellation method is proposed. This method employs TM10 and TM01 modes, which are simultaneously excited in the rectangular passive MPA. Initially, a rectangular decoupling structure featuring polarization rotation characteristics is designed. Further studies show that by loading the polarization conversion parasitic structure (PCPS), the electric field of the spatial coupling wave can be transformed from the x-polarized TM10 mode to the y-polarized TM01 mode. Therefore, TM10 and TM01 modes from the excited antenna and decoupling structure are concurrently coupled to the passive antenna, forming an evident weak-field region on the passive antenna. Placing the feeding probe of the passive MPA within the weak-field region prevents signal reception at the port. Consequently, this results in an extremely low mutual coupling of −49 dB at a resonant frequency of 5.8 GHz. Finally, a prototype of the proposed antenna is fabricated and tested, and the measured results closely match the simulated results. Additionally, it is observed that PCPS slightly influences the performance of the MIMO antenna.

This research article proposes a dual-sense dual-port wideband circularly polarized (CP) multi-input multi-output (MIMO) antenna designed for Wi-Fi 6E applications. The main novelty lies in achieving CP for both ports using a truncated rectangular-shaped aperture. By incorporating design and spatial diversity and defective ground structure between the two radiators, the design improves isolation and enables the antenna to generate Left-Hand Circular Polarization (LHCP)depending on the selected feed port. The proposed MIMO rectangular dielectric resonator antenna demonstrates an impressive impedance-matching bandwidth (IBW)from 5.5 to 8.0 GHz (37.10%) as well as an axial ratio bandwidth (ARBW) covering from 6.0 to 6.55 GHz (12.20%). Additionally, the dual-port wideband CP MIMO antenna exhibits satisfactory diversity performance parameters. To validate the simulated results, a physical prototype is fabricated and subjected to experimental testing. The measured outcomes of the fabricated model align closely with the simulated results, confirming the accuracy of the design. With both MIMO and CP capabilities and improved isolation, this proposed model proves beneficial in reducing latency and minimizing the impact of multipath fading. Therefore, it stands as an excellent choice for future devices utilizing the Wi-Fi 6E band due to its broad IBW and overlappingAR.

A compact 12-element multiple-input multiple-output loop antenna array for a fifth-generation (5G) mobile phone is proposed. The operating band for the proposed antenna covers the long-term evolution 42 band, which spans a frequency range of 3.4–3.6 GHz. The size of the single antenna element is 5.85 × 4.9 mm2 (0.068λ0 × 0.057λ0), and 12 of these elements are positioned along two side edges of the mobile phone. This antenna is suitable for high screen-to-body ratio devices. The measured 6-dB impedance bandwidth is from 3.4 to 3.73 GHz. The measured total efficiency of the proposed antenna is 39–56% and the peak gain is 0–3.2 dBi. The transmission coefficient is less than −12 dB, the envelope correlation coefficient is less than 0.42, and the channel capacity is 45–50 bps/Hz.

An intra-band pattern-corrected decoupling vertical conducting wall is realized by dielectric substrate with conductor cladding on both side wall between two tightly spaced H-plane microstrip patches with λ0/20 edge-to-edge spacing. The wall is grounded and two symmetrical slots are etched on the vertical substrate. The measured results agree with the simulations, showing that the slotted vertical wall reduces the mutual coupling within the bandwidth to −30 dB and corrects the radiation beam tilt to be within −4.5° to 3° from the broadside direction. A gain reduction of 0.6 dB is observed compared to the gain without the slotted decoupling wall.

This research proposes an inexpensive technique for wireless image transfer for security and surveillance applications. The technique uses a 5.8 GHz transmitter and receiver module, along with external antennas in the real-time image transfer within a radius of 100 m. The transferred images are stored in a laptop using a Python code-based graphical user interface application. Different antennas, dipole, circular split-ring resonators, hexagonal split-ring resonators, and metamaterial antennas are utilized for comparison. The Blind/Referenceless Image Spatial Quality Evaluator method is used to assess the picture quality of transferred images to quantify image transfer performance when no ground truth or reference photos are supplied. According to the presented results, images transferred using metamaterial antennas have higher quality than those transferred with other types of antennas. For security considerations, such a system can communicate and store the images in real time.

For forthcoming wireless applications, a small and highly decoupled complementary split ring resonators (CSRR)–loaded co-planar waveguide (CPW)–fed antenna for dual-band applications is investigated. The low-profile antenna consists of a CSRR-loaded rectangular radiating element with a truncated bottom, giving a wideband performance over the frequency ranges of 5.28–5.52 GHz and 6–7.2 GHz. The antenna has been printed on a widely used FR4 substrate measuring 7.5 × 10.5 × 1.6 mm3 in volume. This research’s suggested antenna is turned into a 4 × 4 multi input multi output (MIMO) construction using a 25 × 25 mm2 printed circuit board. Individual antennas were isolated by nearly 20 dB without using a decoupling device. The antenna has been built, and the measured and simulated results correspond well. Computing envelope correlation coefficient (ECC), channel capacity (CC), and channel capacity loss (CCL) further validates the antenna’s performance (−). The antenna has an overall gain of around 2.54 dBi and a radiation efficiency of approximately 89% throughout the relevant spectral range, which is much better for wireless applications. The suggested antenna’s omnidirectional emission pattern makes it a potential contender for future wireless and cellular applications.