In this paper, the biocompatibility of a battery less back-mountable deep brain stimulation (DBS) device is analyzed. To conduct the work, a circular planar inverted F antenna (PIFA) at the resonance frequency of 915 MHz is proposed. The dimension of the antenna is 20 × 19. 8904 × 1. 5mm3. In the proposed antenna, the radiating layer is meandered, and FR-4 material with e r = 4.18, tanδ = 0.02 is used as the substrate with a thickness of 1.5 mm. The bandwidth of the designed antenna is 56.71 MHz at a return loss of −10 dB in free space. Functional and biological aspects are considered here. The functional aspect includes input impedance, resonance frequency, gain pattern, radiation efficiency of the antenna, and the biological aspect involves electric field distribution, and SAR value. A complete rat model is used here. Safety regulation is verified in this paper by the specific absorption rate (SAR) distribution in tissues surrounding the back-mountable passive DBS device. The finite difference time domain (FDTD) based EM simulation software XFdtd is used to determine the electric field distributions which has an impact on the SAR value.