Interrogator of moving body identification device

• US 20050205676A1
• Filed: 08/01/2002
• Published: 09/22/2005
• Est. Priority Date: 08/01/2002
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Saito, Takeshi
• Granted Patent: US 7,277,681 B2
• Time in Patent Office: Days
• US Class Current: 235/439
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10386 the interrogation device being of the portable or hand-handheld type, e.g. incorporated in ubiquitous hand-held devices such as PDA or mobile phone, or in the form of a portable dedicated RFID reader
• CPC Class Codes: H04M 1/0254 comprising one or a plurality of mechanically detachable modules

Abstract

To reduce the size, weight and cost of an interrogator which is included in an RFID system and required to have a high output power, the interrogator for transmitting a signal shares a radio wave source or a power supply with a portable wireless terminal such as a mobile phone or a portable communication device. For this purpose, a radio frequency transmitter signal is subjected to amplitude modulation by information to be transmitted to a transponder. Furthermore, part of the radio frequency transmitter signal extracted using a coupler is used to perform synchronous detection on a radio frequency receiver signal returned from the transponder, and data coming from the transponder are extracted.

Claims

1. An interrogator which, together with a transponder, makes up a radio frequency identification system, comprising:

a transmitter/receiver circuit for generating a radio frequency transmitter signal;

a power amplifier for power amplifying the radio frequency transmitter signal;

an antenna for radiating the radio frequency transmitter signal outputted by the power amplifier;

wherein the transmitter/receiver circuit, the power amplifier and the antenna are provided for a portable wireless terminal;

a circuit for performing amplitude modulation on the radio frequency transmitter signal by information to be transmitted to a transponder; and

a mixer which outputs transponder data by performing synchronous detection, using a part of the radio frequency transmitter signal as a carrier, on a radio frequency receiver signal returned from the transponder and received by the antenna.

2. The interrogator according to claim 1, wherein the circuit for performing amplitude modulation is provided in an input stage of the power amplifier.

3. The interrogator according to claim 2, further comprising:

a coupler for extracting the part of the radio frequency transmitter signal by coupling to the radio frequency transmitter signal outputted by the power amplifier; and

a circulator which, being positioned between the coupler and the antenna, extracts the radio frequency receiver signal outputted by the antenna discretely from the radio frequency transmitter signal being sent to the antenna and supplies the radio frequency receiver signal thus extracted to the mixer for performing synchronous detection.

4. The interrogator according to claim 3, wherein the circuit for performing amplitude modulation is an ASK (Amplitude Shift Keying) modulation circuit.

5. The interrogator according to claim 3, wherein the circuit for performing amplitude modulation is a gain control system in which a gain is controlled by a control signal, the control signal being information to be transmitted to the transponder.

6. The interrogator according to claim 4, wherein at least the ASK modulation circuit, the power amplifier, the coupler, the circulator and the mixer are arranged on one same circuit board.

7. The interrogator according to claim 4, wherein at least the ASK modulation circuit, the power amplifier, the coupler, the circulator and the mixer are arranged on one same IC substrate.

8. The interrogator according to claim 5, wherein at least the coupler, the circulator and the mixer are arranged on one same circuit board.

9. The interrogator according to claim 5, wherein at least the coupler, the circulator and the mixer are arranged on one same IC substrate.

10. An interrogator which, together with a transponder, makes up a radio frequency identification system, comprising:

a first antenna, provided for a portable wireless terminal, for radiating radio waves of a first radio frequency transmitter signal;

a second antenna for receiving the radio waves radiated from the first antenna and outputting the first radio frequency transmitter signal;

a divider for dividing the first radio frequency transmitter signal outputted by the second antenna;

a rectifier for rectifying one of the first radio frequency transmitter signals outputted by the divider and outputting a power supply;

an ASK (Amplitude Shift Keying) modulation circuit for performing amplitude modulation on the other of the first radio frequency transmitter signals outputted by the divider by information to be transmitted to the transponder and outputting the amplitude-modulated signal as a second radio frequency transmitter signal;

a third antenna for radiating the second radio frequency transmitter signal outputted by the ASK modulation circuit; and

a mixer for performing synchronous detection on a radio frequency receiver signal returned from the transponder and received by the third antenna by using part of the second radio frequency transmitter signal as a carrier and outputting transponder data.

11. The interrogator according to claim 10, further comprising:

a coupler for extracting the part of the second radio frequency transmitter signal by coupling to the second radio frequency transmitter signal outputted by the ASK modulation circuit; and

a circulator which, being positioned between the coupler and the third antenna, extracts the radio frequency receiver signal outputted by the third antenna discretely from the second radio frequency transmitter signal being sent to the third antenna and supplies the radio frequency receiver signal thus extracted to the mixer for performing synchronous detection.

12. The interrogator according to claim 11, wherein at least the second antenna, the third antenna, the divider, the rectifier, the ASK modulation circuit, the mixer, the coupler and the circulator are formed in a unitary structure.

13. The interrogator according to claim 11, wherein the information to be transmitted to the transponder and the transponder data outputted by the mixer are supplied to the portable wireless terminal as data to be processed by the portable wireless terminal.

14. The interrogator according to claim 10, wherein the second antenna has a cylindrical structure with a built-in antenna coil and an internal diameter of the second antenna is such that the first antenna is insertable in the second antenna to come into close contact with the second antenna.

15. An interrogator which, together with a transponder, makes up a radio frequency identification system, comprising:

a first antenna provided for a portable wireless terminal for radiating radio waves of a first radio frequency transmitter signal;

a second antenna for receiving the radio waves radiated from the first antenna and outputting the first radio frequency transmitter signal;

a rectifier for rectifying the first radio frequency transmitter signal outputted by the second antenna and outputting a power supply;

an oscillator circuit for generating a signal of a particular frequency;

an ASK (Amplitude Shift Keying) modulation circuit for performing amplitude modulation on the signal of the particular frequency outputted by the oscillator circuit by information to be transmitted to the transponder and outputting the amplitude-modulated signal as a second radio frequency transmitter signal;

a third antenna for radiating the second radio frequency transmitter signal outputted by the ASK modulation circuit; and

a mixer for performing synchronous detection on a radio frequency receiver signal returned from the transponder and received by the third antenna by using part of the second radio frequency transmitter signal as a carrier and outputting transponder data.

16. The interrogator according to claim 15, further comprising:

a coupler for extracting the part of the second radio frequency transmitter signal by coupling to the second radio frequency transmitter signal outputted by the ASK modulation circuit; and

a circulator which, being positioned between the coupler and the third antenna, extracts the radio frequency receiver signal outputted by the third antenna discretely from the second radio frequency transmitter signal being sent to the third antenna and supplies the radio frequency receiver signal thus extracted to the mixer for performing synchronous detection.

17. The interrogator according to claim 16, wherein at least the second antenna, the third antenna, the rectifier, the oscillator circuit, the ASK modulation circuit, the mixer, the coupler and the circulator are formed in a unitary structure.

18. The interrogator according to claim 16, wherein the information to be transmitted to the transponder and the transponder data outputted by the mixer are supplied to the portable wireless terminal as data to be processed by the portable wireless terminal.

19. The interrogator according to claim 15, wherein the particular frequency of the signal is approximately equal to or higher than the frequency of the first radio frequency transmitter signal of the portable wireless terminal.

20. The interrogator according to claim 15, wherein the second antenna has a cylindrical structure with a built-in antenna coil and an internal diameter of the second antenna is such that the first antenna is insertable in the second antenna to come into close contact with the second antenna.