Planar antennas have become an integral component in modern biomedical instruments owing to their compact structure, cost effectiveness, and light weight. These antennas are crucial in realizing medical systems such as body area networks, remote health monitoring, and microwave imaging systems. Antennas intended for the above applications should be conformal and fabricated using lightweight materials that are suitable for wear on the human body. Wearable antennas are intended to be placed on the human body to examine its health conditions. Hence, the performance of the antenna, such as its radiation characteristics across the operating frequency bands, should not be affected by human body proximity. This is achieved by selecting appropriate conformal materials whose characteristics remain stable under all environmental conditions. This paper aims to highlight the effects of human body proximity on wearable antenna performance. Additionally, this paper reviews the various types of flexible antennas proposed for biomedical applications. It describes the challenges in designing wearable antennas, the selection of a flexible material that is suitable for fabricating wearable antennas, and the relevant methods of fabrication. This paper also highlights the future directions in this rapidly growing field. Flexible antennas are the keystone for implementing next-generation wireless communication devices for health monitoring and health safety applications.

Miniaturization of planar antennas is the first intention in antenna design for Ultra-Wideband (UWB) applications in which the surface wave effects reduce the antenna efficiency, gain and limit the bandwidth of microstrip antennas. The ground plane effects are minimized using a Defected Ground Structure (DGS) and multiple slots. A compact antenna size including both ground plane and radiator etched on the printed circuit board is 17mm x 22mm x 1.588mm is proposed. Addition of an asymmetrical strip and cutting slots on the antenna provides an enhancement in operating bandwidth of 2.9 to 11.4 GHz for 10dB return loss and the average radiation efficiency is 88.5% respectively. In particular, the impedance performance of the patch radiator is mainly due to the surface wave currents in the ground plane. The antenna results in an omnidirectional radiation pattern over the operating bandwidth with a gain of 2dB and VSWR of 1 to 2.

A Staircase monopole antenna with microstrip line feed for improved bandwidth and high gain. The etching of staircase steps at the bottom and the top of the rectangular patch antenna improves the impedance matching both at lower and at high frequencies. The implementation of the slots at the top of the patch and the ground plane leads to an improved bandwidth ratio of 5.875: 1. The overall size of the proposed antenna is 72 x 63 x 1.588 mm³, and it has multiple resonances at 2GHz, 4 GHz, 5.8GHz and 7.4 GHz. A fractional bandwidth of 141% is achieved for the return loss of less than -10 dB. The antenna accomplishes a gain of 5.87 dBi. The monopole antenna detects the presences of tumor location from the skin layer of the human breast model.