A miniaturized two-element microstrip antenna array is proposed for the millimeter wave band of 5-th Generation (5G) wireless communication systems. A surface of electromagnetic band gap structures (EBG) is applied as the ground for two closely packed patch antennas operating in 5G New Radio (NR) (26500 MHz - 29500 MHz) frequency band. With the help of the proposed EBG ground, the two E-shaped microstrip antenna elements can be placed in close proximity to each other by 0.3 wavelength center to center distance in free space at the center frequency, yet the mutual coupling between them can still reach to more than 23 dB within the whole band of interest, which is about 10 dB larger than that on normal ground. All major radiation characteristics of the two-element array are well reserved with the EBG ground. The proposed design can be used in multiple-input-multiple-output (MIMO) applications or as the building subarray of larger phased arrays at millimeter wave bands for mobile communication systems.

A circular polarised (CP) microstrip antenna loaded with sunflower‐shaped metasurface (SSM) to enhance the bandwidth using characteristic mode analysis is proposed in this communication. The SSM, divided into inner and outer parts by a ring, consists of equally spaced sectors of equal angles. In this design, the coupled corner‐truncated microstrip antenna with a slot in the centre is employed to obtain CP radiation by exciting two orthogonal modes, which have a 90° phase difference. Meanwhile, it demonstrates that the SSM structure significantly expands the operational bandwidth and exhibits a stable radiation pattern at high frequencies. Simulation and measurement results confirm that this SSM antenna achieves a wide operating bandwidth of 64.3% (4.5–8.76 GHz) and a 3‐dB axial ratio bandwidth of 30.6% (4.7–6.4 GHz), while maintaining a compact profile of 0.68 × 0.68 × 0 0.08 λ ₀ ³ .

This article presents a miniaturized wide-angle scanning phased array for fifth-generation (5G) application. A subarray of two closely packed patch antennas on electromagnetic bandgap structure (EBG) ground with the operating bandwidth of 2629GHz is used as the basic module of the linear array, which contains four equally spaced subarrays. The existence of the EBG ground enables the array to be compact in size (3.2×0.6×0.12λ_L³), yet the mutual coupling between each element can reach to more than 22dB within the whole band of interest. The EBG structures also contribute to the wide element radiation pattern of the aperiodic array and consequently the wide scanning angle performance of the array. The range of the main beam scan with EBG structure can reach from 70° to 70° with more than 6dB side lobe levels (SLLs) at 26.5GHz with 3dBi scanning gain loss. This proposed method enabling the array to be compact and wide in scanning angle is very attractive for 5G mobile terminal applications.

Coating diamond particle surfaces with a layer of high-temperature resistant nickel, which possesses weldability, effectively enhances the bonding strength between diamond particles and substrates in pre-grinding tools. This improves their stability and strength at high temperatures, thereby enhancing the performance, lifespan, and efficiency of grinding tools. This paper explores the electroless nickel plating process on diamond surfaces, analyzes the working principle of electroless nickel plating on diamond surfaces, and proposes the use of 2 g/L AgNO₃ solution and 2 g/L AgNO₃ + 10 mL/L NH₃·H₂O solution as Pd-free activating solutions. Experimental studies have demonstrated the feasibility of using silver nitrate as an activator, and it has been found that the 2 g/L AgNO₃ + 10 mL/L NH₃·H₂O solution achieves a higher surface plating ratio when used as an activator for electroless nickel plating on diamond surfaces. Based on this, through orthogonal and single-factor experimental methods, the effects of ammonia solution concentration, sodium hypophosphite concentration, plating temperature, and diamond particle size on electroless nickel plating on diamond surfaces were investigated. The optimal process for electroless nickel plating on diamond surfaces was obtained: ammonia solution concentration of 17.5 mL/L, sodium hypophosphite concentration of 33 g/L, and plating temperature of 80 °C. Under this process, using diamond particles with a size of 120/140 for electroless nickel plating, a surface plating ratio of 10.75% electroless nickel-plated diamond can be achieved.

An ultra‐wideband circular polarized (CP) antenna array with nonperiodic elliptical shape metasurface (MTS) for millimeter‐wave (mm‐w) applications is proposed in this paper. The element in this array uses fragmented elliptical patches as the MTS and features an elliptical notch microstrip patch beneath it, acting as the primary radiator. Characteristic mode analysis (CMA) was used to analyze the evolution process of the structure and demonstrate the working principle of ∣S ₁₁ ∣ and axial ratio (AR) bandwidth broadening. Based on the proposed element, a 4 × 4 antenna array is designed to achieve higher gain. And the element and arrays are fabricated and measured to verify the design. The measured performance of the proposed element achieves an impedance bandwidth of 89%, covering the frequency range from 15.5 to 40.5 GHz, along with an AR bandwidth of 62.3% (16–30.5 GHz), and reaches a maximum gain of 8 dBi. For the antenna array configuration, the impedance bandwidth spans from 15 to 41 GHz, while the AR bandwidth extends over 17.7–33 GHz, and the peak gain reaches 17.9 dBi. This design highly appropriates for broadband applications in mm‐w satellite applications.