E-shaped patch with reactive impedance surface for high gain and broadband circularly polarized antenna

A low-profile circularly polarized (CP) antenna with high gain and broad bandwidth is aimed at 5-GHz Wi-Fi applications using a symmetrical E-shaped patch. Initially, the radiating element is modeled as a symmetrical E-shape. An array of 4 × 4 rectangular patches are arranged periodically to make up a reactive impedance surface (RIS) structure. Furthermore, the RIS structure is deployed in the middle of a symmetrical E-shaped radiating patch and a perfect electric conductor (PEC) ground plane. As a result, the broadband CP is achieved with high gain. The above-mentioned combinations have achieved a −10-dB reflection coefficient bandwidth of 21.4% (4.92–6.1 GHz) and a 3-dB axial ratio (AR) bandwidth of 15.5% (5.25–6.1 GHz), and the antenna has attained a gain of 7.45–7.53 dBic.     

Miniaturized six-ring elliptical monopole-based MIMO antenna for ultrawideband applications

This paper proposes a miniature two-element Multiple Input Multiple Output (MIMO) antenna dedicated to UWB applications. The proposed MIMO design has a very low profile of 30 × 20 × 1.6 mm³. The proposed antenna is carefully designed and optimized using HFSS simulation software. As a proof of concept, the proposed design is realized and experimentally tested for MIMO applications. The proposed structure, printed on an FR4 substrate, comprises two symmetrical elliptical conductive patches on the upper side and a modified ground plane on the lower one. Each radiating element includes six elliptical rings. The modified ground plane consists of a T-shaped strip and two semielliptical slots etched opposite the feed line. All the parameters of the design are carefully optimized to achieve an ultrawide bandwidth antenna spanning from (136.08%) 3.1 to 16.3 GHz. The results are discussed and analyzed in terms of bandwidth, gain, efficiency, radiation pattern, diversity gain, envelope correlation coefficient (ECC), total active reflection coefficient (TARC), and mean effective gain (MEG). All simulated results are found to be in good accordance with experiments. The design reveals attractive features for UWB applications. A good isolation (17 dB) between the two radiators is achieved despite the close proximity using the suggested ground plane geometry.     

Differential space–time modulation for DS‐CDMA systems

Differential space–time modulation (DSTM) schemes were recently proposed to fully exploit the transmit and receive antenna diversities without the need for channel state information. DSTM is attractive in fast flat fading channels since accurate channel estimation is difficult to achieve. In this paper, we propose a new modulation scheme to improve the performance of DS‐CDMA systems in fast time‐dispersive fading channels. This scheme is referred to as the differential space–time modulation for DS‐CDMA (DST‐CDMA) systems. The new modulation and demodulation schemes are especially studied for the fast fading down‐link transmission in DS‐CDMA systems employing multiple transmit antennas and one receive antenna. We present three demodulation schemes, referred to as the differential space–time Rake (DSTR) receiver, differential space–time deterministic (DSTD) receiver, and differential space–time deterministic de‐prefix (DSTDD) receiver, respectively. The DSTD receiver exploits the known information of the spreading sequences and their delayed paths deterministically besides the Rake‐type combination; consequently, it can outperform the DSTR receiver, which employs the Rake‐type combination only, especially for moderate‐to‐high SNR. The DSTDD receiver avoids the effect of intersymbol interference and hence can offer better performance than the DSTD receiver. Copyright © 2001 John Wiley & Sons, Ltd.     

Design of compact fractal patch antenna for X/Ku/K-band applications

This paper presents a fractal-based compact new monopole antenna for wideband applications. The miniaturization has been achieved by incorporating Minkowski and Koch-snowflake fractals. The proposed antenna design is etched on top of Rogers RT/5880 dielectric material with a dimension of $8.10\times 8.10$ mm². The antenna is designed, analyzed, fabricated, and tested in the laboratory. The proposed geometry operates over a 8.62–22.40 GHz with fractional bandwidth (FBW) of 88.84% and VSWR is less than 2. The proposed monopole antenna exhibits nearly omnidirectional radiation patterns over the entire resonating band with a gain of 1–2.91 dBi and a radiation efficiency of more than 60.5%. Also, the measured results of the prototype make an excellent agreement with the simulated counterpart. Further, the antenna gives good time-domain characteristics. Therefore, the proposed miniaturized antenna can be used in X/Ku/K-band applications.     

Co-located and space-shared multiple-input multiple-output antenna module and its applications in 12 × 12 multiple-input multiple-output systems

In this study, we developed a co-located and space-shared multiple-input multiple-output (MIMO) antenna module with a modular design and high integration level. The proposed antenna pair includes a half-wavelength loop antenna and a dipole-type antenna printed on the front and back sides of a compact modular board. Owing to their modal orthogonality, these two independent antenna elements are highly self-isolated and free of additional decoupling components, even though they are assembled at the same location and within the same space. Thus, the proposed antenna is attractive in 5G MIMO systems. Furthermore, the proposed co-located and space-shared MIMO antenna module was employed in a 5G smartphone to verify their radiation and diversity performances. A 12 × 12 MIMO antenna system was simulated and fabricated using the proposed module. Based on the results, the proposed module can be employed in large-scale MIMO antenna systems for current and future terminal devices owing to its high integration, compactness, simple implementation, and inherent isolation.