A Sub-6 GHz MIMO Antenna Array for 5G Wireless Terminals

This paper presents a novel antenna with its array and MIMO configuration for the 5G sub-6 GHz applications. The proposed antenna element operates at the central frequency of 5.57 GHz dedicated for Sub-6 GHz 5G communication applications. The antenna element holds a circular-shaped radiating portion with an inner-circular slot, plus a rectangular slot at its right edge to make the proposed design resonate at the desired frequency band. The RT5880 substrate is used with a thickness of 0.787 mm, and the low-loss tangent of 0.0009. To achieve a desired gain of 12 dB, a four-element array configuration is adopted, which improved a bore side gain to 12.4 dB from 6.66 dB. Then, the two-port configuration is adopted such that the isolation achieved between them is more than −30 dB. The total efficiency of the proposed antenna array is observed to be more than 80% within the operating bandwidth. Moreover, the Specific Absorption Rate (SAR) analysis is also presented for the proposed MIMO configuration, obeying the standard value (i.e., <2 W/kg for any 10 g of tissue). The measured results are in good agreement with the simulated results. All the simulations of the proposed design are performed in the CST MWS software.

Omnidirectional Microstrip Patch Antenna for 2.4 GHz Wireless Communications

Antenna studies on various wireless communication systems have been carried out by many academics. In this research, the omnidirectional microstrip patch antenna (MPA) is proposed, manufactured, and tested. The operating bandwidth of the antenna is quite suitable for the different applications. The proposed antenna fabricated on the flame retardant (FR-4) substrate with a volume of 75.85 × 57.23 × 1.59 mm3. Computer simulation technology (CST) studio used to design and simulate. Experimental results show that the return loss (RL), bandwidth (BW), voltage standing wave ratio (VSWR) and input impedance (Zin ) are -25.26 dB, 61 MHz, 1.12 and 54.46 Ω, respectively. The antenna operates at 2.42 GHz (from 2.39 to 2.45 GHz), which has good performance in the Wi-Fi, Bluetooth, and ZigBee communications.

Double slot aerosol jet printed antenna for X-band applications

A double slot antenna for X-band applications was designed and aerosol jet printing technology was used to fabricate the prototype with silver nano-ink on a flexible polyimide substrate. We investigated the microwave losses of printed antennas in the range from 100 kHz to 27 GHz, obtained at sintering temperatures of 200 °C and 250 °C. Double slot X-band antennas have been calculated and measured. It was found that an operating bandwidth of the printed antenna is 10% in the region of the central frequency of 10.5 GHz. Thus, the possibility of forming antennas on flexible polymer substrates with high functional characteristics by aerosol jet printing method has been demonstrated.

A Super Wideband Directional Compact Vivaldi Antenna for Lower 5G and Satellite Applications

In this paper, a super wide band (SWB) Vivaldi antenna has been proposed for lower 5G bands in Sub-6 GHz and satellite applications (S, C, X, Ku, and K band) using various performance improvement techniques. In the presented Vivaldi antenna, different slots are applied not only to increase the gain and directivity but also to get operating frequency at the intended specific frequency range. All dimensions of those slots were chosen by using the sweep parameter method. Ten corrugated side slots, two circular slots, and one via have been used to enhance the performance especially bandwidth and gain of the antenna. At the edge of wireless communication, we want to enhance two key aspects within the communication systems: the quality of service and the cost. The proposed antenna incorporates a simple structure and small size with dimensions of 45 × 35 × 0.79 mm3. Thus, after design, optimization, and simulation, the antenna produces a good reflection coefficient over the very large operating bandwidth of 23.19 GHz, 1 < VSWR < 2, maximum gain of 10.2 dBi, and average radiation efficiency of above 90%, which can be recommended as a suitable antenna for lower 5G as well as satellite applications. The antenna is designed, simulated, and analyzed by using computer simulation technology microwave studio (CST-MWS). Finally, the performance of the Vivaldi antenna has been validated by FEKO and HFSS software, and we achieved a very good matching among the results.

Design of an S-Band Phased Array with Modified Dipoles

A wideband, low cross-polarization, high-gain, and wide-angle scanning antenna array is presented in this paper. The antenna array contains 8 subarrays in the horizontal dimension, and each subarray contains 4 unit cells. A two-side printed dipole with an amendatory equivalent circuit model is adopted, and the metal vias are introduced in the element design to ameliorate the cross-polarization level. A radome, acting as the wide-angle impedance matching layer, is introduced to achieve wide-angle scanning. A prototype of a 4 × 8 array is fabricated and measured. The results show that the operating bandwidth of aperture efficiency (BWAE) above 60% is about 26.7% from 2.6 GHz to 3.4 GHz. The measured scanning loss in the H-plane is 2.7 dB when scanning up to 60° with active voltage standing wave ratio (VSWR) <3, and the gain can achieve 21 dB at 3 GHz with a cross-polarization level below −30 dB at all angles.

Field Decorrelation and Isolation Improvement in an MIMO Antenna Using an All-Dielectric Device Based on Transformation Electromagnetics

This work presents a new technique for enhancing the performance of a multiple-input multiple-output (MIMO) antenna by improving its correlation coefficient ρ. A broadband dielectric structure is designed using the transformation electromagnetics (TE) concept to decorrelate the fields of closely placed radiating elements of an MIMO antenna, thereby decreasing ρ and mutual coupling. The desired properties of the broadband dielectric wave tilting structure (DWTS) are determined by using quasi-conformal transformation electromagnetics (QCTE). Next, the permittivity profile of the DWTS is realized by employing air-hole technology, which is based on the effective medium theory, and the DWTS is fabricated using the additive manufacturing (3D printing) technique. The effectiveness of the proposed technique is verified by designing two-element patch-based MIMO antenna prototypes operating at 3 GHz, 5 GHz, and 7 GHz, respectively. The proposed technique helped to reduce the correlation coefficient ρ in the range of 37% to 99% in the respective operating bandwidth of each MIMO antenna, thereby, in each case, improving the isolation between antenna elements by better than 3 dB, which is an excellent performance.

Analysis and design of diode physical limit bandwidth efficient rectification circuit for maximum flat efficiency, wide impedance, and efficiency bandwidths

Generally, a conventional voltage doubler circuit possesses a large variation of its input impedance over the bandwidth, which results in limited bandwidth and low RF-dc conversion efficiency. A basic aspect for designing wideband voltage doubler rectifiers is the use of complex matching circuits to achieve decade and octave impedance and RF-dc conversion efficiency bandwidths. Still, the reported techniques till now have been accompanied by a large fluctuation of the RF-dc conversion efficiency over the operating bandwidth. In this paper, we propose a novel rectification circuit with minimal inter-stage matching that consists of a single short-circuit stub and a virtual battery, which contributes negligible losses and overcomes these existing problems. Consequently, the proposed rectifier circuit achieves a diode physical-limit-bandwidth efficient rectification. In other words, the rectification bandwidth, as well as the peak efficiency, are controlled by the length of the stub and the physical limitation of the diodes.

S Band Hybrid Power Amplifier in GaN Technology with Input/Output Multi Harmonic Tuned Terminations

In this paper, the design, fabrication, and measurements of an S band multi harmonic tuned power amplifier in GaN technology is described. The amplifier has been designed by exploiting second and third harmonic tuning conditions at both input and output ports of the active device. The amplifier has been realized in a hybrid form, and characterized in terms of small and large signal performance. An operating bandwidth of 300 MHz around 3.55 GHz, with 42.3 dBm output power, 9.3 dB power gain and 53.5% power added efficiency PAE (60% drain efficiency) at 3.7 GHz are measured.

UWB Dual-Band-Notched Lanky-Leaf-Shaped Antenna with Loaded Half-Square-Like Slots for Communication System

A novel printed compact single-layer dual-band-notched antenna for the use of ultra-wide band (UWB) is proposed in this paper, and one lanky-leaf-like structure with a coplanar waveguide (CPW) feed is designed as the radiated element for a large operating bandwidth. To realize the dual-band-notched characteristics of microwave access (WiMAX) and wireless local area networks (WLAN), two half-square-like slots are etched on the metallic surface. The fabricated prototype of this proposed antenna has a compact size of 27 × 32 mm2 and operates at 2.8 GHz to 10 GHz, excepting for rejection bands at 3.06–3.83 GHz and 5.05–5.96 GHz. Nearly omnidirectional radiation patterns are obtained in the working band. Furthermore, one conformal design on cylinder and transfer characteristics are made to validate its potential application. These findings indicate that this antenna can be taken as a promising option for use in the UWB communication field.

Analysis and Development of an Efficient Cross-Slot Loaded Compact Electromagnetic Band Gap Antenna

This paper is devoted to a novel Electromagnetic Band Gap (EBG) single-feed circularly polarized microstrip EBG antenna with compact size proposed for C-Band applications. The antenna structure will include eight slits introduced at the boundary and the corners in the radiating square patch with a cross-slot at the center. The provided study will effectively approve the various proposed structures and interest occupied by these types of antennas in the enhancement of output parameters (gain, directivity, radiation efficiency, and bandwidth) without much affecting the operating bandwidth at C-band. At first, the concept and the realization of a directive and circularly polarized antenna using an electromagnetic band gap material whose circular polarization is generated by the structure itself is discussed. The analysis and simulation results are presented for an antenna operating at 6.1 GHz using computer Simulation Technologies (CST). Furthermore, the new compact circular polarized EBG antenna, compared to experimental results, will confirm the pre-studied goal of these kinds of antennas such as radiation efficiency, polarization purity, radiation efficiency, high directivity, and gain.