Patent ID: 8862054

Claim:
A radio power converter operable to convert an inputted environmental electromagnetic wave into a direct-current voltage, comprising: an antenna including a coil, a fixed capacitor, and a variable capacitor; a rectifier which outputs a rectified signal from an alternate-current signal outputted from the antenna; a decoupling capacitor which is charged with the rectified signal so that the rectified signal is held as a direct-current voltage; and a VDD level determination circuit which divides the direct-current voltage being held and outputs N control signals (where N is a positive integer) to control a value of the variable capacitor, wherein the antenna receives an environmental electromagnetic wave having the same frequency as an antenna resonance frequency to convert the environmental electromagnetic wave into an electric power that is to charge the decoupling capacitor and to thereby increase the direct-current voltage, wherein the antenna resonance frequency is changed by varying the variable capacitor depending upon a value of the direct-current voltage increased, wherein the antenna receives the environmental electromagnetic wave in a frequency band that corresponds to the direct-current voltage being increased and to thereby increase the direct-current voltage to a desired direct-current voltage, and wherein an interval of assigning a voltage range of the direct-current voltage being increased specifies a single antenna resonance frequency to be set to the antenna and has a narrow voltage range as a value of the increased direct-current voltage becomes close to the desired direct-current voltage.