Rf ID Tag Device

• US 20090033462A1
• Filed: 02/21/2005
• Published: 02/05/2009
• Est. Priority Date: 02/27/2004
• Status: Active Grant

• Current Assignee: Hitoshi Kitayoshi
• Original Assignee: Intelligent Cosmos Research Institute
• Inventors: Sawaya, Kunio, Kitayoshi, Hitoshi
• Granted Patent: US 8,179,263 B2
• Time in Patent Office: Days
• US Class Current: 340/10.100
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/79 Systems using random coded signals or random pulse repetition frequencies , e.g. "Separation and Control of Aircraft using Non synchronous Techniques" [SECANT]
• CPC Class Codes: G01S 7/023 Interference mitigation, e.g. reducing or avoiding non-intentional interference with other HF-transmitters, base station transmitters for mobile communication or other radar systems, e.g. using electro-magnetic interference [EMI] reduction techniques auxiliary means for detecting or identifying radar signals or the like G01S7/021; means for anti-jamming G01S7/36
• 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 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/07786 the antenna being of the HF type, such as a dipole
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• CPC Class Codes: H01Q 1/248 provided with an AC/DC converting device, e.g. rectennas
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 9/065 Microstrip dipole antennas patch antenna H01Q9/0407
• CPC Class Codes: H01Q 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence
• CPC Class Codes: H02J 50/005 Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/27 characterised by the type of receiving antennas, e.g. rectennas
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H04B 1/59 Responders; Transponders

Abstract

The present invention aims to overcome the drawback with conventional RFID tag devices having a short communication range, and expand the communication range to several times or more that in the conventional scheme. The conventional scheme is based on equilibrium feeding/equilibrium modulation (a two-terminal circuit for antenna operation), whereas the present invention is based on disequilibrium feeding/equilibrium modulation (a three-terminal circuit for antenna operation). The conventional scheme is based on simple rectification of received RF signals, whereas the present invention employs a circuit based on a combination of a stub resonance-based, impedance transformation boosting scheme and a ladder boosting scheme. The conventional scheme is based on ASK or BPSK modulation, whereas the present invention is based on passive modulation, but can employ a QPSK modulation circuit.

Claims

1-20. -20. (canceled)

21. An RFID tag device comprising a divided microstrip antenna, a power receiving circuit based on a combination of a stub resonance-based, impedance transformation RF boosting scheme and a ladder boosting/rectifying scheme, and a local oscillator circuit for generating a response subcarrier signal.

22. The RFID tag device according to claim 21, wherein a dividing position of the divided microstrip antenna is slightly deviated from a longitudinal center point across strip conductors by at least 5% or more with respect to the length.

23. The RFID tag device according to claim 21 being an RF tag as a modulation scheme of which a passive QPSK modulation method is usable.

24. The RFID tag device according to claim 21, wherein impedance modulation elements of the divided microstrip antenna are respectively connected to opposite ends in a strip conductor width direction so as to connect divided conductors.

25. The RFID tag device according to claim 24, wherein the impedance modulation elements are PIN diodes or varactor diodes.

26. The RFID tag device according to claim 25, wherein the impedance modulation elements constitute a voltage or current controlled three-terminal element using a transistor, rather than a diode.

27. The RFID tag device according to claim 21, wherein a capacitance of 1 pF/GHz or less is used for connecting the power receiving circuit and an antenna feeding point to perform high-impedance capacitive feeding.

28. The RFID tag device according to claim 21, wherein capacitive load impedances in a stub resonator and a ladder boost rectifier circuit of the power receiving circuit are parallel resonant, and further, the capacitive feeding impedance are series resonant.

29. The RFID tag device according to claim 21, wherein when considering longitudinal connections of capacitors in the ladder boost rectifier circuit of the power receiving circuit as GND- and receiving-side rails, capacitor capacitance of the receiving-side rail is smaller than that of the GND-side rail, a first diode between GND and a receiving point is eliminated, and a high-frequency and high-impedance input is receivable by a DC short.

30. The RFID tag device according to claim 23, wherein a logic circuit including a ¼

frequency divider, a shift register and a data selector is used in the passive QPSK modulation method.

31. The RFID tag device according to claim 30, wherein MPSK modulation is applied by using a 1/M frequency divider, an M-stage shift register and an M-input data selector.

32. The RFID tag device according to claim 23, wherein response information including a tag ID code, etc. is recorded to a memory in units of two bits in accordance with the passive QPSK modulation method.

33. The RFID tag device according to claim 23, including an output timing generator circuit for obtaining an output enable signal in the passive QPSK modulation method.

34. The RFID tag device according to claim 33, wherein the output timing generator circuit generates a train of pulses with a random delay time having a fixed width and a fixed frame cycle, based on a source voltage size and a clock signal.

35. The RFID tag device according to claim 21, wherein by using a transducer such as a temperature sensor quartz resonator as the local oscillator circuit for generating the response subcarrier signal, a sensor function capable of allowing its oscillating frequency to be read by an external unit is additionally used.

36. A position detecting method for a mobile object having no RFID tag, wherein in a system composed of an RFID device as claimed in claim 21 and one or more master devices (interrogators), whether or not an obstacle is present in a radio wave propagation path extending between each RFID tag device and each interrogator is determined based on the presence or absence of communication between the RFID tag and the interrogator.

37. The position detecting method for a mobile object having no RFID tag according to claim 36, wherein a plurality of radio wave propagation paths present between each RFID tag and each interrogator are distinguished based on a combination of a local oscillating frequency for generating a response subcarrier of each RFID tag, a response timing, a frequency of an interrogation radio wave outputted from the interrogator and timing of generating the interrogation radio wave.

38. A position detecting method for a mobile object having an RFID tag, wherein radio waves at two or more frequencies are transmitted to an RFID tag device as claimed in claim 21 from an interrogator having two or more antennas dedicated for reception or used for transmission and reception, and based on a difference in phase between receiving antennas in a signal for response thereto, maximum likelihood determination of a position of the RFID tag is performed.

39. The position detecting method for a mobile object having an RFID tag according to claim 38, wherein in order to enable a three-dimensional RFID tag position determination, an interrogation device having four or more antennas dedicated for reception or used for transmission and reception is used to eliminate a commonly measured distance offset by obtaining a group delay time in each radio wave propagation path based on four or more sets of frequency responses measured for the two or more frequencies, and obtaining a difference in delay time with reference to at least one of the sets.

40. The RFID tag device according to claim 21, including two or more tag antennas in order to expand its possible communication range.

41. A communication method, wherein an RFID tag device as claimed in claim 40 periodically changes directionality of an intense response subcarrier radio wave, which is synthesized by periodically changing a phase of a local oscillating signal provided to each tag antenna for generating a response subcarrier signal, thereby returning an intense response radio wave toward an interrogator in a wide area.