Antennas, when brought into close proximity with RF reflective objects or lossy human tissue, will show a degradation in performance. This degradation is visible in the input impedance as a function of frequency and in the radiation pattern, gain and efficiency. In the presentation we will show two examples of miniature antennas designed for on-body use that exhibit a negligible performance degradation when brought near or onto the human body. One of the examples comprises a miniature, curved microstrip patch antenna for application on the wrist (Figure 1). Here, the ground plane of the patch antenna has been used to form a shielding between the antenna and the environment. The other example is a coplanar waveguide printed monopole antenna, embedded in a low-loss dielectric body to contain the fields and thus minimize reactive tuning (Figure 2). Furthermore the short ground plane of this antenna has been modified to suppress coaxial cable current radiation. In the designs, the human body has been modeled as a curved, layered medium consisting of skin, fat, muscle, bone and, when appropriate, dura, cerebrospinal fluid and brain tissue. We will present the CST designs, the realized prototypes and the measurement results will be presented.
Hubregt J. Visser, PhD, Holst Centre – IMEC-NL