In this work, we propose a low-profile single-layer coplanar waveguide (CPW)-fed metasurface (MTS) antenna with broadband circular polarization radiation. With the help of characteristic mode analysis (CMA), a 3 × 4 metasurface is analyzed to reveal the useful modes supported by the structure. Consequently, two modes with orthogonal current distribution, broadside radiation, and nearly 90° phase difference over a wide frequency band are chosen as operation modes. Moreover, the modal near-field of the aforementioned modes shows that, unlike conventional microstrip patches, the entire proposed metasurface supports two kinds of extraordinary TM modes namely e- TM ₃₀ and e-TM ₀₄ . Accordingly, a rotated CPW feeding line is used to excite the two modes without adding an extra layer as reported in the literature, making the design simpler and easier to manufacture. Based on that, a low profile antenna of 0.058λ ₀ has been designed and fabricated. The measured results show an impedance bandwidth (IBW) of 25% (4.87-6.26 GHz), 3-dB axial ratio band (AR) of 19.42% (5.30-6.44 GHz), and a maximum gain of 8 dBi.

In this paper, we present a novel design of a compact miniaturized dual-band antenna for industrial, scientific, and medical (ISM) implantable applications working at 915 MHz and 2.4 GHz. The proposed antenna has a compact size of ( $6\times 6\times0.25$ mm3). The antenna shows a wide bandwidth of 12.6% at the lowest frequency and 12.8% at the highest frequency and gain values of −21.8 dBi and −19.2 dBi at 915 MHz and 2.4 GHz, respectively which are relatively high for implantable applications. The design has been done for healthy and unhealthy tissues (adenocarcinoma). Furthermore, the fabricated prototype has been tested in minced pork as a suitable real tissue to validate the simulated results. Finally, a comparison with the recently published state-of-the-art solutions is provided showing good results in terms of size, bandwidth and gain.

A compact circularly polarized (CP) implantable antenna working at 915 MHz, at the industrial, scientific, and medical (ISM) band, is developed in this article. The proposed radiator is based on a fully planar and low-profile patch antenna with a ground plane and different slots but without any via holes, which makes the structure a good candidate for implantable devices. The circular polarization is achieved by means of introducing a surrounding and asymmetrical U-shaped structure. A meander line has been included in the inside of the U-shaped structure to increase the electrical length of the antenna without increasing its mechanical dimensions. An impedance bandwidth of 18.9% from 810 to 980 MHz and an axial ratio of 17.2% from 850 to 1010 MHz have been achieved. The proposed antenna has a compact size of $5.2\times 5.6\times0.25$ mm ³ , which seems to be the smallest antenna over the recently reported implantable antennas. In addition, the proposed antenna achieves a relatively high gain value of −23 dBi.

This paper proposes a new triple-band monopole antenna based on Complementary Split Ring Resonators (CSRR) perturbing the ground plane (GND). The antenna consists of an inverted-L-shaped monopole fed by a modified microstrip line with two CSRRs cut out of the ground plane. The operational bands are independently controlled by the CSRR unit cell parameters. In addition, the antenna presents a dual-polarization performance (vertical polarization at 2.4 GHz band and horizontal polarization at both 3.6 and 5.9 GHz bands). The designed antenna is fully planar and low profile avoiding the vias with the ground plane and covering the WLAN, WiMAX, and IEEE 801.11p bands at 2.45, 3.6, and 5.8 GHz. A compact prototype (0.32λ0 × 0.32λ0 being λ0 is the wavelength corresponding to the lowest resonance frequency) has been fabricated and measured showing good agreement between simulations and measurements. The measured impedance bandwidths are 10% (2.38-2.63 GHz), 2.5% (3.54-3.63 GHz), and 20% (5.83-7.12 GHz) whereas the measured gains are 1.34, 0.68, and 2.65 dBi at 2.4, 3.6, and 5.9 GHz respectively.

In this paper, we present the developement of a miniaturized wireless power transfer (WPT) for spinal cord (SC). The system comprises a dual-band implantable antenna, a wearable slotted patch antenna and a half-wave rectifier. It introduces a miniaturized dual-band implantable antenna, combining meandered line and spiral techniques to achieve wide impedance bandwidths. The transmitter antenna demonstrates an impedance bandwidth below - 10 dB, spanning a fractional impedance bandwidth of approximately 5.5% from 1.42 GHz to 1.5 GHz. On the other hand, the dual-band implantable antenna receiver and the rectifier were designed on a two-layer printed circuit board (PCB), the compactness of the system is improved by integrating the rectifier circuitry directly onto the bottom of the implanted antenna, streamlining the overall design. Its dimensions are 7 × 7 × 0.5 mm³, achieves impedance bandwidths of 20.5% and around 17% at the industrial, scientific, and medical (ISM) frequency of 915 MHz and 1470 MHz, respectively. Furthermore, the proposed WPT system achieves a power transfer efficiency (PTE) of 1.15%, by improving the coupling between the receiving (Rx) and transmitting (Tx) antennas using magnetic-based designs, thereby reducing human tissue losses. Finally, the measured results obtained inside minced pork shows a high degree of agreement with the expected performance, validating the system’s performance in realistic biological environments.

Wireless power transfer (WPT) in biomedical implants has become a vital area of research and innovation, primarily because it eliminates the need for frequent and invasive battery replacements. Biomedical implants, such as pacemakers, neural stimulators, and drug delivery systems, require reliable and long-term power sources to ensure their functionality. Traditionally, these devices relied on batteries that necessitated surgical interventions for replacement once implanted. However, such procedures pose risks of infection, tissue damage, and patient discomfort. WPT offers a non-invasive solution to this challenge by enabling energy transmission through electromagnetic fields or other techniques. Various methods have been proposed and studied in the literature for transferring power wirelessly within the human body. Capacitive coupling, inductive coupling, and resonant inductive coupling are among the most common methods. Each type has its own advantages and limitations based on factors such as range and power efficiency. By advancing WPT technology, researchers are enhancing the reliability, safety, and convenience of biomedical implants, improving the quality of life for millions of patients worldwide.