Title:
NONCONTACT TYPE INFORMATION CARD
Document Type and Number:
Japanese Patent JP3761001
Kind Code:
B2
Abstract:
PROBLEM TO BE SOLVED: To evade the application of overvoltage without impairing the writing characteristic by controlling the resonance frequency of a resonance circuit which transmits a prescribed frequency band of the voltage generated according to the change of a magnetic field based on the output of a rectifier means which rectifies the output of the resonance circuit.
SOLUTION: When an information card 23 comes extremely close to the loop antenna of a reader/writer, the electric power energy that is received by a loop antenna 10 of the card 23 is increased. Since the receiving voltage is applied to a variable capacitance element C23 via a pure resistance element R23, the resonance is shifted by the receiving voltage, and the receiving efficiency is lowered. Therefore, the voltage received by the antenna 10 of the card 23 is suppressed and the overvoltage protection is attained. The capacitance varies to lower the receiving efficiency even of receiving voltage becomes too large and the too large receiving voltage is evaded owing to use of the element C23, i.e., a capacitance element constructing a parallel resonance circuit and varying its capacitance by the applied voltage.
Inventors:
Shigeru Arisawa
Application Number:
JP32517095A
Publication Date:
March 29, 2006
Filing Date:
November 20, 1995
Export Citation:
Assignee:
ソニー株式会社
International Classes:
G06K17/00; G06K19/07; G07B15/02; H03J5/00; H04B5/02; (IPC1-7): G06K17/00; G06K19/07; H03J5/00; H04B5/02
Domestic Patent References:
| JP5128319A | ||||
| JP6096300A |
Attorney, Agent or Firm:
Keiki Tanabe
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