Contactless receiver, resonant circuit, and variable capacitance element

Abstract

A contactless receiver is provided with a receiving section and a rectification section. The receiving section has a resonant circuit including a resonant capacitor having a variable capacitance element formed with a ferroelectric material, a capacitance of the variable capacitance element changing according to a received voltage at a predetermined frequency, and a resonance coil connected to the resonant capacitor. The rectification section converts an alternating current voltage output from the receiving section into a direct current voltage.

What is claimed is: 
     
         1 . A contactless receiver comprising:
 a receiving section including a resonant capacitor, and a resonant coil connected to the resonant capacitor, the resonant capacitor including a variable capacitance element having a ferroelectric layer formed with a ferroelectric material, a first electrode arranged on one side of the ferroelectric layer, and a second electrode arranged on the opposite side of the ferroelectric layer, and a capacitance of the variable capacitance element changing according to a received voltage at a predetermined frequency; and   a rectification section connected to the first electrodes and the second electrodes, via leads, respectively, and operable to convert the alternating current voltage output from the receiving section.   
     
     
         2 . The contactless receiver according to  claim 1 , further comprising a signal processing section which operates with the direct current voltage output from the rectification section for demodulating received signals. 
     
     
         3 . The contactless receiver according to  claim 1 , wherein the variable capacitance element has a characteristic that the capacitance of the variable capacitance element becomes smaller or larger when the received voltage becomes higher within a predetermined voltage range within a range in which the received voltage changes. 
     
     
         4 . The contactless receiver according to  claim 1 , wherein the received voltage corresponding to a maximum capacitance of the variable capacitance element is equal to or smaller than a minimum operating voltage of the signal processing section.