This thesis is focused on the design and simulation of miniaturized antennas for wireless biomedical sensors. The motivation of the work was to provide a solution for wireless systems that are embedded or placed on the body. Currently, small antennas are on demand to be implanted inside the body or placed closely to the body. The performance of such antennas, gain and efficiency, is affected by the lossy tissues that surround them. The goal of this work was to design antennas that are placed on a living body and integrated with a sensor system implanted in living tissue, to measure the dielectric properties of the tissue. The antenna type that this work was based on is Planar Inverted F Antenna (PIFA). The assumption was that the antenna is placed on skin layer and not embedded inside a tissue layers. A few antennas were designed and simulated. Two major studies were performed. First, an antenna, which was originally proposed in literature for wireless communication systems, was adopted and revised for biomedical applications. The antenna performance while it was on two tissue layers (skin and fat) was studied and optimized. The objective was to understand how miniaturization and the surrounding environment affect the antenna resonance frequency and performance. A second study was performed to design a novel PIFA antenna to improve the performance and reduce the size further