Noncontact IC card reader/writer

• US 7,182,266 B2
• Filed: 06/29/2004
• Issued: 02/27/2007
• Est. Priority Date: 06/30/2003
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yoshinaga, Hiroshi, Hirata, Akihiko, Tanaka, Masahiko, Deguchi, Futoshi, Haruyama, Hiroaki
• Primary Examiner(s): Frech; Karl D.
• Application Number:
  US10/878,633
• Publication Number:
  US 20050029351A1
• Time in Patent Office: 973 Days
• Field of Search: 235/439, 235/449, 235/450, 235/451, 235/380, 235/382, 235/375, 235/492, 235/487
• US Class Current: 235/492
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer

Abstract

The object of the invention is to provide a small-sized noncontact IC card reader/writer that can enhance the efficiency of an amplifier at a low cost. To achieve the object, in the invention, a loop antenna that supplies electric power and a send signal to a noncontact IC card by electromagnetic induction and acquires a receive signal from the noncontact IC card by load fluctuation, a first resonance circuit for resonating the loop antenna with a desired first frequency, a radio transmitter that supplies electric power and send data to the loop antenna via the first resonance circuit and further, a radio receiver that acquires the receive signal from the loop antenna via a second resonance circuit connected to the loop antenna via a coupling capacitor and resonated with a desired second frequency are provided, the radio transmitter and the radio receiver are respectively connected to CPU, and a low-pass filter for removing a high frequency, a class E amplifier and a modulator are connected to the radio transmitter in series.

Claims

1. A noncontact IC card reader/writer that communicates data with a noncontact IC card, comprising:

an antenna, which supplies electric power and a transmitting signal to the noncontact IC card;

a first resonance circuit, which resonates the antenna;

a radio transmitter, which supplies both electric power and transmitting data to the antenna via the first resonance circuit; and

a CPU that controls an operation of the radio transmitter,

wherein the radio transmitter comprises a low-pass filter, an amplifier and a modulator, and the low-pass filter, the amplifier and the modulator are connected in series.

2. A noncontact IC card reader/writer according to claim 1, wherein:

the class E amplifier comprises a FET for a switching device;

the gate of the FET is connected to a signal generator;

the drain of the FET is connected to both an end of a first coil and an end of a loading network; and

the source of the FET is connected to the modulator.

3. A noncontact IC card reader/writer according to claim 2 wherein the loading network comprises a first capacitor, a second coil and a second capacitor, and a constant of the loading network is set to a desired value by arranging the first capacitor, the second coil and the second capacitor so that the functions as a class E amplifier.

4. A noncontact IC card reader/writer according to claim 3 wherein the loading network has an input terminal and an output terminal, wherein both an end of the first capacitor and an end of the second coil are connected to the input terminal of the loading network, the other end of the second coil is connected to the second capacitor and the other end of the second capacitor is connected to the output terminal of the loading net work.

5. A noncontact IC card reader/writer according to claim 4, wherein:

the low-pass filter has an input terminal and an output terminal,

the third capacitor and the third coil are connected between the input terminal and the ground in series,

an end of the fourth coil is connected to the input terminal,

an end of the fifth coil is connected to the other end of the fourth coil,

the other end of the fifth coil is connected to the output terminal of the low-pass filter,

an end of the fourth capacitor is connected between the fourth coil and the fifth coil, and

the other end of the fifth capacitor is connected to the other end of the fifth coil.

6. The noncontact IC card reader/writer according to claim 5, wherein:

the third capacitor and the third coil respectively arranged in series between the input terminal and the ground are also used for a compensating circuit for removing reactance.

7. A noncontact IC card reader/writer according to claim 3, wherein the low-pass filter comprises a third capacitor, a third coil, a fourth coil, a fifth coil, a fourth capacitor and a fifth capacitor.

8. A reader/writer that communicates data with a noncontact recording medium, comprising:

an antenna, which supplies electric power and a transmitting signal to the noncontact recording medium;

a first resonance circuit, which resonates the antenna;

a radio transmitter, which supplies both electric power and transmitting data to the antenna via the first resonance circuit; and

a CPU that controls an operation of the radio transmitter,

wherein the radio transmitter comprises a low-pass filter, an amplifier and a modulator, and the low-pass filter, the amplifier and the modulator are connected in series.

9. A noncontact IC card reader that communicates data with a noncontact IC card, said reader comprising:

a loop antenna which supplies electric power and a signal to the non-contact IC card by electromagnetic induction and receives a signal from the non-contact IC card by load fluctuation;

a first resonance circuit which resonates the loop antenna with a first predetermined frequency;

a radio transmitter which supplies electric power and transmits data to said loop antenna via said first resonance circuit; and

a radio receiver which receives the signal from said loop antenna via a second resonance circuit coupled to said loop antenna via a coupling capacitor and resonated with a second predetermined frequency,

wherein said IC card reader includes a CPU, said radio transmitter includes a low-pass filter, a class E amplifier and a modulator, said radio transmitter and said radio receiver are respectively coupled to said CPU, said low-pass filter removes a high frequency, and said class E filter and said modulator are coupled in series with each other.

10. A non-contact IC card reader according to claim 9, wherein:

said class E amplifier includes a FET for switching, a signal generator for generating a signal and a first coil one end of which is coupled to a power source;

a gate of said FET is coupled to said signal generator;

a drain of said FET is coupled to the other end of said first coil; and

a source of said FET is coupled to said modulator.

11. A noncontact IC card reader according to claim 10, wherein:

said IC card reader further comprises a loading network coupled between said class E amplifier and said low-pass filter;

said loading network includes a first capacitor one end of which is grounded, a second capacitor and a second coil;

the other end of said first capacitor and one end of said second coil are coupled to an input terminal of said load network;

the other end of second coil is coupled to one end of said second capacitor;

the other end of second capacitor is coupled to an output terminal of said load network; and

a constant in said load network is determined to cause said class E amplifier to function in a condition of a class E.

12. A non-contact IC card reader according to claim 11, wherein:

said low-pass filter includes a third capacitor, a fourth capacitor, a fifth capacitor, a third coil, a fourth coil and a fifth coil;

said third capacitor and said third coil are coupled in series between an input terminal of said low-pass filter and ground;

one end of said fourth coil is coupled to an output terminal of said low-pass filter;

one end of said fifth coil is coupled to the other end of said fourth coil;

the other end of fifth coil is coupled to an output terminal of said low-pass filter;

said fourth capacitor has one end connected to ground and is coupled between said fourth coil and said fifth coil; and

said fifth capacitor has one end connected to ground and is coupled to the other end of said fifth coil.

13. A noncontact IC card reader according to claim 12, wherein said third capacitor and said third coil function to remove reactance.