This communication presents the design of a dual-band circular implantable antenna for biomedical applications. The proposed antenna operates at the Medical Implant Communication Services (MICS) band (402-405 MHz) and Industrial Scientific and Medical (ISM) band (2400-2483.5 MHz). The antenna occupies an area of ${\rm{\pi \times 10^{2} \times 2.54\ mm^{3} (797.96\ mm^{3})}}$ . The dual-band is realized in a circular patch by deploying via holes, open-ended slots in the ground plane and a superstrate. The prototype antenna is fabricated and measured using tissue-equivalent liquid model and pork meat to verify the suitability design. The proposed antenna has a peak gain of -33.1 and -14.55 dBi at 400 MHz and 2.45 GHz respectively. The specific absorption rate is 241.5 W/Kg for 1g of Tissue with a maximum input power of 6.625mW. Furthermore, the proposed antenna's salient features are compared with the state-of-the-art implantable antennas.

A compact circular structured monopole antenna for ultrawideband (UWB) and UWB dual-band notch applications is designed and fabricated on an FR4 substrate. The UWB antenna has a hybrid configuration of the circle and three ellipses as the radiating plane and less than a quarter-lowered ground plane. The overall dimensions of the projected antennas are 16 × 11 × 1.6 mm³, having a −10 dB impedance bandwidth of 113% (3.7–13.3 GHz). Further, two frequency band notches were created using two inverted U-shaped slots on the radiator. These slots notch the frequency band from 5–5.6 GHz and 7.3–8.3 GHz, covering IEEE 802.11, Wi-Fi, WLAN, and the entire X-band satellite communication. A comprehensive frequency and time domain analysis is performed to validate the projected antenna design’s effectiveness. In addition, a circuit model of the projected antenna design is built, and its performance is evaluated. Furthermore, unlike the traditional technique, which uses the simulated surface current distribution to verify functioning, characteristic mode analysis (CMA) is used to provide deeper insight into distinct modes on the antenna.

The design, fabrication, and experimental validation of wideband reflectarray with concentric coupled half-square rings operating at 26.5 GHz for 5G communication is presented in this paper. The proposed unit cell has a simple square patch enclosed within the coupled half-square rings. The varying delay line length attached to the outer ring provides a phase variation of 420°. A center-fed reflectarray antenna constructed with circular geometry (12.6 diameters) using 413 elements offers a measured gain of 27.1 dBi and 51.25% of aperture efficiency at its center frequency. The measured 3- and 1-dB gain bandwidth of 45% and 28.6% along with a side lobe level (SLL) of −17.6 dB are achieved. The measured cross-polarization level is less than −28 dB. Thus, the proposed wideband reflectarray has evolved into a provocative candidate for applications like base station antennas in earth exploration satellites, mobile base station satellites, and radio astronomy satellites.

A novel wideband reflectarray antenna (RA) is designed for 5G millimeter (mm) wave communications in the frequency range of 26.5–36 GHz. The proposed unit cell is constructed using a grid periodicity of 0.52 ${{\lambda }_0}{ }$ that offers 636° phase change through phase delay lines (PDLs) ( ${{\theta }_{\text{s}}}$ ). These PDLs are attached to the outer end of the unit cell comprising semi-circular rings. Bandwidth enhancement is achieved by incorporating a corrugated slot technique and a suitable air gap beneath the substrate. The proposed center-fed reflectarray is composed of 513 elements distributed in a circular aperture (13.46 ${{\lambda }_0}$ ). Using mirror-symmetrical distribution of the unit cells, a cross-polarization reduction as low as −50 dB is realized. At 30 GHz, RA has a measured peak gain of 28.2 dBi, a sidelobe level of −14.3 dB, and an aperture efficiency of 31.4%. The prototype antenna is fabricated, and the simulation results are experimentally validated. The measured 1-dB and 3-dB gain bandwidths of the proposed reflectarray antenna are 31.3% and 41.6%, respectively. The proposed broadband reflectarray can be a potential choice for inter-satellite services like inter-satellite networking/satellite positioning and control; fixed satellite services such as GPS satellite synchronization and data direct to home TV; and satellite position fixing.