TRANSMITTER/RECEIVER FOR RADIO COMMUNICATION, RFID SYSTEM AND RECEIVING METHOD FOR TRANSMITTER/RECEIVER FOR RADIO COMMUNICATION

• US 20090027169A1
• Filed: 07/17/2008
• Published: 01/29/2009
• Est. Priority Date: 07/26/2007
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: MOCHIZUKI, Shinichirou, KONDO, Ryoichi
• Granted Patent: US 8,285,224 B2
• Time in Patent Office: Days
• US Class Current: 340/10.200
• 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
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04Q 2213/13095 PIN / Access code, authentication

Abstract

A transmitter/receiver for radio communication according to an embodiment of the present invention has: a transmission circuit for generating a transmission signal; a demodulation circuit for demodulating a receive signal; an antenna circuit for transmitting the transmission signal from the transmission circuit and receiving the receive signal and guiding the receive signal to the demodulation circuit; a phase shift circuit which is connected between the transmission circuit and the antenna circuit; and a switching circuit which switches between outputting a superimposed signal of the transmission signal and the receive signal between the phase shift circuit and the antenna circuit to the demodulation circuit, and outputting a superimposed signal of the transmission signal and the receive signal between the transmission circuit and the phase shift circuit to the demodulation circuit.

Claims

1. A transmitter/receiver for radio communication, comprising:

a transmission circuit for generating a transmission signal;

a demodulation circuit for demodulating a receive signal;

an antenna circuit for transmitting said transmission signal from said transmission circuit, and receiving said receive signal and guiding said receive signal to said demodulation circuit;

a phase shift circuit which is connected between said transmission circuit and said antenna circuit; and

a switching circuit which switches between outputting a superimposed signal of the transmission signal and the receive signal between said phase shift circuit and said antenna circuit to said demodulation circuit, and outputting a superimposed signal of the transmission signal and the receive signal between said transmission circuit and said phase shift circuit to said demodulation circuit.

4. The transmitter/receiver for radio communication according to claim 1, further comprising a matching circuit which is connected between said transmission circuit and said antenna circuit, wherein a part of said matching circuit, or said matching circuit, is used as said phase shift circuit.

6. The transmitter/receiver for radio communication according to claim 1, wherein a phase shift amount of said phase shift circuit is (2N-1) times of 45 degrees of a carrier wave in said transmission signal (N is a positive integer)±

15 degrees.

9. The transmitter/receiver for radio communication according to claim 1, wherein said receive signal is generated by a load modulation system, and said demodulation circuit or said first and second demodulation circuits use an amplitude demodulation system.

12. The transmitter/receiver for radio communication according to claim 1, further comprising a control circuit for having said switching circuit perform switching when a demodulation signal from said demodulation circuit cannot be recognized within a predetermined time.

15. The transmitter/receiver for radio communication according to claim 1, wherein said switching circuit is switched so as to select a greater amplitude demodulation signal.

18. The transmitter/receiver for radio communication according to claim 1, further comprising a control circuit which causes said switching circuit to perform switching repeatedly and causes said switching circuit to stop switching when a demodulation signal from said demodulation circuit can be recognized.

21. An RFID system, comprising:

an RFID reader/writer which uses the transmitter/receiver for radio communication according to claim 1; and

an RFID tag which replies with a response signal to said RFID read/writer according to a command signal from said RFID reader/writer.

2. A transmitter/receiver for radio communication, comprising:

a transmission circuit for generating a transmission signal;

a demodulation circuit for demodulating a receive signal;

an antenna circuit for transmitting said transmission signal from said transmission circuit, and receiving said receive signal and guiding said receive signal to said demodulation circuit;

a phase shift circuit which is disposed between said transmission circuit and said antenna circuit; and

a switching circuit which switches between connecting said transmission circuit and said demodulation circuit to said antenna circuit not via said phase shift circuit, and connecting said transmission circuit and said demodulation circuit to said antenna circuit via said phase shift circuit.

7. The transmitter/receiver for radio communication according to claim 2, wherein a phase shift amount of said phase shift circuit is (2N-1) times of 45 degrees of a carrier wave in said transmission signal (N is a positive integer)±

15 degrees.

10. The transmitter/receiver for radio communication according to claim 2, wherein said receive signal is generated by a load modulation system, and said demodulation circuit or said first and second demodulation circuits use an amplitude demodulation system.

13. The transmitter/receiver for radio communication according to claim 2, further comprising a control circuit for having said switching circuit perform switching when a demodulation signal from said demodulation circuit cannot be recognized within a predetermined time.

16. The transmitter/receiver for radio communication according to claim 2, wherein said switching circuit is switched so as to select a greater amplitude demodulation signal.

19. The transmitter/receiver for radio communication according to claim 2, her comprising a control circuit which causes said switching circuit to perform switching repeatedly and causes said switching circuit to stop switching when a demodulation signal from said demodulation circuit can be recognized.

22. An RFID system, comprising:

an RFID reader/writer which uses the transmitter/receiver for radio communication according to claim 2; and

an RFID tag which replies with a response signal to said RFID read/writer according to a command signal from said RFID reader/writer.

3. A transmitter/receiver for radio communication, comprising:

a transmission circuit for generating a transmission signal;

an antenna circuit for transmitting said transmission signal from said transmission circuit, and receiving said receive signal and guiding said receive signal to said transmission circuit side;

a phase shift circuit which is connected between said transmission circuit and said antenna circuit;

a first modulation circuit which is connected to a node between said phase shift circuit and said antenna circuit;

a second demodulation circuit which is connected to a node between said transmission circuit and said phase shift circuit; and

a switching circuit which switches between outputting a demodulation signal from said first demodulation circuit, and outputting a demodulation signal from said second demodulation circuit.

5. The transmitter/receiver for radio communication according to claim 3, further comprising a matching circuit which is connected between said transmission circuit and said antenna circuit, wherein a part of said matching circuit, or said matching circuit, is used as said phase shift circuit.

8. The transmitter/receiver for radio communication according to claim 3, wherein a phase shift amount of said phase shift circuit is (2N-1) times of 45 degrees of a carrier wave in said transmission signal (N is a positive integer)±

15 degrees.

11. The transmitter/receiver for radio communication according to claim 3, wherein said receive signal is generated by a load modulation system, and said demodulation circuit or said first and second demodulation circuits use an amplitude demodulation system.

14. The transmitter/receiver for radio communication according to claim 3, further comprising a control circuit for having said switching circuit perform switching when a demodulation signal from said demodulation circuit cannot be recognized within a predetermined time.

17. The transmitter/receiver for radio communication according to claim 3, wherein said switching circuit is switched so as to select a greater amplitude demodulation signal.

20. The transmitter/receiver for radio communication according to claim 3, further comprising a control circuit which causes said switching circuit to perform switching repeatedly and causes said switching circuit to stop switching when a demodulation signal from said demodulation circuit can be recognized.

23. An RFID system, comprising:

an RFID reader/writer which uses the transmitter/receiver for radio communication according to claim 3; and

an RFID tag which replies with a response signal to said RFID read/writer according to a command signal from said RFID reader/writer.

24. A receiving method for a transmitter/receiver for radio communication provided with a transmission circuit for generating a transmission signal, a demodulation circuit for demodulating a receive signal, and an antenna circuit for transmitting said transmission signal from said transmission circuit, and receiving said receive signal and guiding said receive signal to said demodulation circuit, the method comprising the steps of:

shifting a phase of said receive signal, when a demodulation signal from said demodulation circuit cannot be recognized within a predetermined time; and

demodulating a superimposed signal of a phase-shifted receive signal and transmission signal in said demodulation circuit.

25. A receiving method for a transmitter/receiver for radio communication provided with a transmission circuit for generating a transmission signal, a demodulation circuit for demodulating a receive signal, and an antenna circuit for transmitting said transmission signal from said transmission circuit, and receiving said receive signal and guiding said receive signal to said demodulation circuit, the method comprising the steps of:

performing repetitive demodulation which alternately repeats demodulation of a superimposed signal of a transmission signal and a receive signal, and demodulation of a superimposed signal of a phase-shifted receive signal and transmission signal in said demodulation circuit; and

stopping said repetitive demodulation in said demodulation circuit when a demodulation signal from said demodulation circuit can be recognized.