Implantable medical devices, especially brain implants, show great promise for applications such as epilepsy detection, Parkinson’s disease regulation, and brain–computer interfaces. However, battery-based power supplies suffer from degradation, surgical replacement risks, and limited compatibility with miniaturization, motivating wireless power transfer (WPT) as a promising alternative. Among various approaches, ultrasonic WPT is particularly attractive due to its strong penetration capability, no electromagnetic interference, and favorable safety profile. This thesis presents the design and implementation of a high-efficiency receiver (RX) circuit for ultrasonic WPT applications, with a focus on biomedical implants. Several rectifier topologies are investigated. Although the current-mode rectifier (CMR) demonstrates promising characteristics, its performance is significantly limited in ultrasonic WPT due to the low quality factor of the transducer. Consequently, the cross-coupled rectifier is ultimately selected for its simplicity and superior conversion efficiency. A boost converter is integrated to further increase the rectified voltage, with its duty cycle serving as the sole tunable parameter for impedance matching. Based on the maximum power transfer theorem, an adapted perturb and observe (P\&O) maximum power point tracking (MPPT) algorithm is developed to dynamically adjust the duty cycle, thereby achieving automatic impedance matching and maximizing the power delivered to the load. The start-up issue is resolved through the implementation of a maximum-voltage selector, ensuring stable operation from system initialization. Simulation results demonstrate a peak overall system efficiency of 83.55\%, with the cross-coupled rectifier and boost converter achieving efficiencies of 91.55\% and 91.26\%, respectively. The proposed system maintains high efficiency under varying load and input conditions, validating its feasibility for reliable and efficient power delivery in ultrasonic WPT systems for brain implants.