A wideband hybrid dielectric resonator antenna (DRA) consisting of a rectangular slot patch and a perforated stacked cylindrical dielectric resonator (DR) is proposed. A rectangular slot was etched on the grounding side of a microwave laminate (ϵs =3.38) to excite the hybrid resonator at a high frequency. The stacked DR used consists of three different layers of permittivity, in which air-cavity was introduced internally to form a perforated structure. With a proper stacking arrangement of the perforated DRs on top of the rectangular slot, their operating frequencies were merged together to produce a wideband hybrid DRA. It was found that the combination of the stacked DR with perforated structure in the hybrid element had yielded an impedance bandwidth of as wide as 75.8% (12.2 GHz - 27.1 GHz). Huge improvement in bandwidth was successfully achieved in this study in comparison to that without a perforated structure of only 48.9%. Simulation of the antenna was performed in time domain using Computer Simulation Technology (CST) and was subsequently verified with the measurement results. The average simulated and measured directivity of the antenna were recorded to be 6.05 dBi and 5.65 dBi, respectively, with a stable broadside radiation throughout the operating range of frequency. The radiation characteristics were seen to be broadside in both the E-plane and H-plane.

Multiple-input and multiple-output (MIMO) is currently regarded as key technology for long term evolution (LTE) but a critical effect is mutual coupling (S 21) due to space constraint in miniaturized design. A compact-size antenna with low mutual coupling would be an ideal choice for better system performance. This paper describes the design of a small-size (48×48 mm 2) MIMO antenna system with low mutual coupling for LTE 800 MHz applications. The antenna system comprises of two FR-4 substrate layers; one printed with two meander line antennas (MLAs), the other printed with reactive impedance surface (RIS) and defected ground structure (DGS). The properties of the antenna like S-Parameters, excited surface current distribution, far-field radiation pattern and diversity performance characteristics were studied. The results indicated that MLAs rendered compactness to the system. Introduction of air gap (AG) between the two substrates, DGS and periodic square patches of RIS resulted in 452 MHz bandwidth and mutual coupling of-41.18 dB between antenna elements. The performance of the proposed design compared with other reported geometry has been demonstrated. Parameters including bandwidth, ratio of antenna area/improvement in S 21 , antenna efficiency and the envelope correlation coefficient were compared. Considering the results, the present system appears to be comparatively more efficient.

This paper focuses on the topic of joint communication and radar sensing (JCRS) and its applications in the scope of upcoming sixth-generation (6G) technology. While the fifth-generation applications have reached the consumer market in the last few years, JCRS has been identified as one of the key technologies for next generation networks. The role of JCRS will vary, ranging from tasks such as radar coordination, context awareness for communication, enhanced security, increased availability, and improving the resilience and trustworthiness of future networks. In this work, the niche of JCRS technology in the future 6G ecosystem, as well as several potential applications, are discussed with a focus on RF hardware. The use of centimeter (cmWave) and millimeter (mmWave) frequency spectrums in the context of JCRS system implementation have been further elaborated. After presenting the near-term application scenarios, the circuit implementation perspectives are investigated in terms of radio frequency (RF) front-end architectures, antenna implementation, and phased arrays. Different communication and radar antenna options are compared, and the best candidates are identified. The packaging options are also presented. From circuit and system perspectives, link budget and self-interference cancellation (SIC) are highlighted. Furthermore, future directions including the next steps on the path to enabling JCRS technology are presented throughout this article. Prior works focused more on physical layers and network capabilities of JCRS systems, with less focus on hardware possibilities; to fill this gap, this article aims to contribute to this exciting research topic with a holistic review of RF hardware, highlighting the diversity of applications and the available technologies to tackle the near- and long-term needs of consumer applications.

The upcoming generation of wireless systems is expected to integrate both communication and sensing capabilities by flexibly allocating resources, including hardware. Phased array antenna (PAA) systems are already vital in communication systems and radars and, therefore, have been intensively studied for several decades. Considering the availability of multiple review assessments for PAA implementation and signal processing, this article fills an existing gap by evaluating the hardware challenges and possibilities for sharing a PAA towards deployable integrated sensing and communication (ISAC) applications. Both types of applications impose tight and often divergent antenna-performance requirements, such as control over beam shape, scanning resolution, and side lobe tolerance. The inherent performance trade-offs, such as pencil beam for refined sensing versus broader beam for instantaneous coverage, highlight the complex design priorities that must be tailored to the application to achieve optimal joint system performance. This paper evaluates state-of-the-art antenna array structures and beamforming techniques in the context of ISAC systems. Although less popular due to their inherent limitations, passive beamforming networks are particularly highlighted for several proposed solutions, e.g., reciprocity and multibeam concept, and elaborated through a design and measurement by the authors. This article addresses the theoretical challenges that emerge while realizing a phased array out of a single element, their impact on sensing and communication performances, and finally, a summary of their mitigation techniques from the state-of-the-art. Selected simulation and measurement results from the authors support the discussions. The paper presents a set of PAA performance matrices for the ISAC system and their related joint benefits or trade-offs. The key enablers towards PAA sharing for ISAC systems, including quasi-circulator, gain-boosting lens, and electromagnetic bandgap structures, are presented, highlighting contemporary technological developments and related theoretical aspects. With the in-depth review, the authors also demonstrate proof of concept for the selected technologies through design steps, simulations, and measurements.