Rakesh Nath Tiwari

This paper presents a compact 4 × 4 multiple input multiple output antenna designed to operate at triple-band frequencies of 28, 29.58 and 32.82 GHz. The antenna is fabricated on a Rogers RT 5880 substrate with overall dimensions of 13 × 13 × 0.254 mm ³ . The antenna operates over three frequency bands: 27.70–28.32 GHz, 29.44–29.91 GHz, and 32.72–33.10 GHz, with realized gains of 7.8 dBi, 4.8 dBi, and 7.6 dBi, respectively. Mutual coupling between the antenna elements is effectively reduced by the combined effect of orthogonal element orientation and a fan-shaped slot in the ground plane, yielding isolation levels >22 dB across the three operating bands. The surface current distribution analysis of the perturbed ground plane is presented to demonstrate the decoupling mechanism between the adjacent radiating elements. The antenna exhibits excellent diversity performance, with an envelope correlation coefficient below 0.004, a diversity gain close to 10 dB, a mean effective gain below −3.5 dB, and a channel capacity loss below 0.26 bits/s/Hz. The calculated antenna results are validated with the measurements and found suitable for 5G smartphones, IoT systems and vehicular communications.

The design and analysis of a 1 × 4 mm-wave MIMO antenna in a lateral configuration are presented. The antenna utilizes a square slotted patch structure and demonstrates triple-band operation at 28/38/43 GHz. The first band offers antenna bandwidth from 27.79 to 28.35 GHz (0.56 GHz), while the second band spans 37.68 to 38.43 GHz (0.75 GHz) and the third band covers 42.56–43.55 GHz (0.99 GHz), respectively. The antenna is fabricated on Rogers RO3003 with material permittivity of 3.0, a loss tangent of 0.001, and a substrate height of 0.25 mm. For both bands, the antenna demonstrates the isolation > 20 dB. It also provides peak gain values of 6.54 dBi at 28 GHz, 7.10 dBi at 38 GHz, and 6.11 dBi at 43 GHz with an average radiation efficiency of 82%. Key diversity metrices including ECC, MEG, and CCL were evaluated. The ECC remains below 0.022, and the CCL of the antenna is below 0.32 bits/s/Hz, which is favorable for MIMO systems. These results indicate that the reported MIMO antenna is suitable for future 6G communication systems.

This paper presents the design and analysis of a graphene-based patch antenna for terahertz (THz) communication applications. The proposed antenna has a compact footprint of 60 μm × 60 μm and employs an inset-fed modified graphene patch to achieve dual-band operation. The antenna exhibits resonances at 0.58 THz and 1.01 THz, with |S₁₁| below −30 dB, indicating excellent impedance matching. The tunability of graphene is investigated by varying the chemical potential and relaxation time, and the antenna performance is optimized accordingly. It is observed that higher values of chemical potential and relaxation time enhance the surface conductivity of graphene, resulting in improved impedance matching and radiation efficiency. A detailed parametric study is also carried out by varying the dimensions of the slot etched on the patch. The results demonstrate that slot dimensions significantly influence both impedance matching and resonance frequency tuning. The antenna achieves a gain > 2.53 dBi and total efficiency exceeding 60% across both operating bands. The radiation patterns in both E- and H-planes are nearly omnidirectional at 0.58 THz and 1.01 THz, making the design suitable for near-field THz applications. The electromagnetic performance of the proposed graphene patch antenna is analyzed using CST Microwave Studio.

In this manuscript, a graphene-based four-port linear MIMO antenna is proposed for terahertz (THz) applications. The antenna is designed on a polyimide substrate with a compact footprint of 60 µm × 240 µm × 4 µm. A modified triangular patch with a tip-fed configuration is employed to enhance asymmetric current distribution, enabling dual-band operation at 2.88 THz and 4.36 THz. A parametric analysis is carried out by varying the chemical potential and relaxation time of graphene to optimize the antenna performance in terms of S-parameters. The proposed design achieves an inter-element isolation > 20 dB, with a realized gain exceeding 3.28 dBi and radiation efficiency above 65% across both operating bands. Furthermore, key MIMO diversity parameters are evaluated, demonstrating an envelope correlation coefficient (ECC) ≤ 0.008 and channel capacity loss (CCL) ≤ 0.27 bits/s/Hz over the entire operating range. The total active reflection coefficient (TARC) remains stable under varying excitation phase conditions, indicating minimal mutual coupling between adjacent ports. An equivalent circuit model is also developed to validate the simulated results. The antenna is analyzed using CST Microwave Studio, and the obtained results confirm its suitability for emerging THz wireless applications.

The leadless cardiac pacemaker is a revolutionary device for bradycardia patients. It is a single-component, capsule-type implantable medical device that corrects the heart's electrical function when the heart rate falls below the standard value of 60 beats per minute. The remote monitoring feature enables the leadless pacemaker to monitor bradycardia patients’ heart health, and it is only possible due to the ultra-compact antenna of the implantable leadless pacemaker's biotelemetry system. This article reviews the leadless pacemaker's antennas for biotelemetry and power telemetry systems, the importance of intra-cardiac communication for dual-chamber leadless pacemakers, and future requirements of leadless pacemaker antennas. Considering the real-time device architecture, some crucial aspects of antenna design in the simulator are given by briefing the research conducted to date. Furthermore, experimental verification of the antenna's functioning in the cardiac environment is also provided by summarizing different approaches used by previous studies. Dual-chamber leadless pacing communication and the requirement of leadless pacemaker antennas in 5G/6G IoT healthcare environment are also briefly discussed.