This paper presents an ultra-miniaturized implant antenna with a volume of 22.22 mm ³ in the Medical Implant Communication Service (MICS) frequency band 402-405 MHz to be integrated with a leadless cardiac pacemaker. The proposed antenna has a planar spiral geometry with a defective ground plane exhibiting a radiation efficiency of 3.3% in the lossy medium with more than 20 dB of improved forward transmission, while the coupling can be further enhanced by adjusting the thickness of the antenna insulation and the antenna size according to the application area. The implanted antenna demonstrates a measured bandwidth of 28 MHz, covering beyond the MICS band needs. The proposed circuit model of the antenna describes the different behaviors of the implanted antenna over a wide bandwidth. The antenna interaction within human tissues and the improved behavior of the electrically small antenna are explained in terms of radiation resistance, inductance, and capacitance that are obtained from the circuit model. The results are demonstrated using electromagnetic computations and are validated by the measurement using liquid phantom and animal experiments.

This paper presents a design methodology for the implementation of a miniaturized square patch antenna and its circuit model for 5.15 GHz ISM band. The miniaturization is achieved by employing concentric complementary split ring resonator (CSRR) structures in between the patch and ground plane. The results are compared with the traditional square patch antenna in terms of area, bandwidth, and efficiency. The area is reduced with a ratio of 1/4 with respect to the traditional patch. The miniaturized square patch antenna has an efficiency, bandwidth, and reflection coefficient of 78%, 0.4%, and −16 dB, respectively. The measurement and circuit modeling results show a good agreement with the full-wave electromagnetic simulations.

In this letter, we propose fundamental path loss (PL) models which play vital roles in promoting the intraheart communication system design of future deeply implanted leadless pacemakers inside the cardiac chambers. Initially, employing a plane wave approach yields the attenuation of the electric field in homogeneous heart tissue, while a modified Friis equation in the lossy medium is utilized to evaluate the power transmission between transmitting and receiving antennas in homogeneous heart tissue in the far-field zone. An Hertzian dipole excitation is used to separate the mismatch and ohmic losses of the antenna from the path loss in an anatomical human body simulation environment. Based on this theoretical and full-wave simulation setup, PL models are derived and comprehensively compared at different potential frequency bands [Medical Implant Communication Service (MICS) 402-405 MHz, Wireless Medical Telemetry Service (WMTS) 608-614 MHz, Industrial, Scientific, and Medical (ISM) 867-869 MHz, and 2400-2500 MHz], and the validity of applying the Friis equation in this scenario is verified.

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.

In this paper, a planar polarization independent resonant cavity antenna (RCA) is proposed to achieve higher gain with a single patch connection instead of using antenna arrays with additional feeding losses. The planar metasurface is based on sub-wavelength complementary circular metallic patches, which provide the same magnitude and phase response for both TE and TM polarized waves. In order to excite the metasurface, an aperture coupled antenna with a circular patch is used to make its integration easier with the metasurface. The proposed antenna design works from 8.97 GHz to 13.1 GHz with a measured 3dB gain bandwidth of 24.2 % and it is used to increase the antenna’s gain from 8 dBi up to 14.67 dBi. The RCA achieves the measured bandwidths (input matching <-10 dB) above 4 GHz or 37.4 %, among the highest reported in the literature with 2 layers.

In this paper, a triple-band 1 × 2 and 1 × 4 microstrip patch antenna array for next-generation wireless and satellite-based applications are presented. The targeted frequency bands are 3.6, 5.2 and 6.7 GHz, respectively. Simple design procedures and optimization techniques are discussed to achieve better antenna performance. The antenna is designed and simulated using Agilent ADS Momentum using FR4 substrate (ε_r= 4.2 and h = 1.66 mm). The main patch of the antenna is designed for 3.6 GHz operation. A hybrid feed technique is used for antenna arrays with quarter-wave transformer-based network to match the impedance from the feed-point to the antenna to 50 Ω. The antenna is optimized to resonate at triple-bands by using two symmetrical slits. The single-element triple-band antenna is fabricated and characterized, and a comparison between the simulated and measured antenna is presented. The achieved simulated impedance bandwidths/gains for the 1 × 2 array are 1.67%/7.75, 1.06%/7.7, and 1.65%/9.4 dBi and for 1 × 4 array are 1.67%/10.2, 1.45%/8.2, and 1.05%/10 dBi for 3.6, 5.2, and 6.7 GHz bands, respectively, which are very practical. These antenna arrays can also be used for advanced antenna beam-steering systems.