The advancement of capsule endoscopy toward higher-resolution imaging and multifunctional capabilities has significantly increased power consumption, rendering traditional low-frequency (kHz) wireless charging methods and limited battery capacities insufficient. We present a miniaturized 6.78 MHz wireless power transfer (WPT) system that eliminates magnetic cores and leverages compact MHz coils to drastically reduce both transmitter and receiver size. A three-dimensional orthogonal receiving coil design achieves near-zero mutual coupling, enabling independent operation without interference, with outputs combined via full-bridge rectification and filtering. A prototype, validated through modeling, simulation, and experiments under varying positions and orientations, delivers up to 1.681 W with 23.0 \% peak efficiency. These results demonstrate efficient high-frequency wireless charging in a compact form factor, offering a viable solution for next-generation capsule endoscopes.
