Figure 4.

Optimizing wireless inductive energy harvesting using a prototype chip with laser‐programmable fuses. a) Microphotograph of the prototype chip featuring fuse‐connected capacitors for resonance RF tuning, a rectifier, and a digital engine. b) Schematic of the 3‐stage cross‐coupled rectifier and capacitors. c) Graphs depicting the average clock frequency recovered via BPSK demodulation, showing the effect of external Tx power source levels (at 915 MHz) and tuning capacitances in both air and liquid head phantom environments respectively (n = 3). d) Plot illustrating the relationship between the threshold Tx power for chip activation as a function of the incident Tx tone frequency and matching capacitance. e) Illustration of the Tx coil and microchip's location in relation to the Tx coil (left) and simulation results of wireless efficiency in various positions (right). f) Measured Tx threshold power level depending on the location of the microchip and tuning capacitance (left). Dependence of clock frequencies on the Tx power for three microchips, shown in two configurations: non‐optimal (right top) and optimal (right bottom), indicating the efficiency improvement in the latter (packet number for data points = 200 for each condition, the legend shows matching capacitance value in each chip). Abbreviations: cap.: capacitance, CLK: clock frequency.