JPH1155165A - Transmitter/receiver for rf tag - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmitter/receiver for RF tag which can strengthen electromagnetic induction coupling with an RF tag which is provided on an article having a circular outer form. SOLUTION: This RF tag having a circular coil 201 is embedded in a tray 200 and by the side of a large number of piled trays 200, a coil 10 of the RF tag transmitter/receiver is arranged. In this case, the shape of the coil 10 of the RF tag transmitter/receiver is curved along the outer form of the tray 200. Thus, an average interval between the coil 10 of the RF tag transmitter/ receiver and the coil 201 embedded in the tray 200 can be reduced, and electromagnetically induced coupling with the RF tag can be strengthened, so that a large number of RF tags can be communicated all at once.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an RF tag transceiver for communicating with an RF tag by electromagnetic induction.

[0002]

2. Description of the Related Art FIG. 6 shows a block diagram of an electromagnetic induction type RF tag system. The RF tag transceiver 1 (interrogator) and the RF tag (responder) 2 are configured to perform transmission and reception using electromagnetic induction.
Transmits an interrogation signal to the RF tag 2, and the RF tag 2 transmits the ID information and the like stored in the RF tag 2 to the RF tag transceiver 1 as a response signal by the interrogation signal.

For this purpose, the RF tag transceiver 1 includes a transmission circuit 11, a magnetic field generation circuit 12, a magnetic field detection circuit 13, a reception circuit 14, and an information processing circuit 15, and the information processing circuit 15
Thus, transmission and reception processing for the RF tag 2 is performed using the circuits 11 to 14. Power is supplied from a power supply circuit 16 to each circuit of the RF tag transceiver 1.

The RF tag 2 includes a magnetic field detection circuit 21,
It includes a receiving circuit 22, a transmitting circuit 23, a magnetic field generating circuit 24, and an information processing circuit 26. When an inquiry signal is received from the RF tag transceiver 1, ID information and the like are transmitted to the RF tag transceiver 1.
Is configured to be transmitted to. In addition, power is supplied from a power supply circuit 25 to each circuit of the RF tag 2. The power supply circuit 25 includes the RF tag transceiver 1.
A circuit that creates a power supply voltage based on a signal transmitted from the power supply can be used.

In the above configuration, the magnetic field generation circuit 12 in the RF tag transceiver 1 and the magnetic field detection circuit 21 in the RF tag 2, and the magnetic field detection circuit 13 in the RF tag transceiver 1 and the magnetic field generation circuit 2 in the RF tag 2
Each of the coils 4 is provided with a coil (for example, a loop coil having a size of several cm to several meters), and signals are transmitted and received by electromagnetic induction between the coils.

In this case, the RF tag transceiver 1 transmits an AC magnetic field of a predetermined carrier frequency (often modulated by a predetermined signal), and the RF tag 2 receiving the magnetic field similarly transmits the predetermined frequency to the predetermined frequency. (Often modulated with a signal carrying information unique to the RF tag 2), and the RF tag transceiver 1 receives the transmitted magnetic field,
The RF tag transceiver 1 detects the presence of the RF tag 2 and detects information of the RF tag 2 in a non-contact manner.
Note that the carrier frequency may be several tens kHz to several tens.
0 kHz is mainly used. As a signal modulation method, an FSK (Frequency Shift) that changes the frequency of an AC magnetic field at a predetermined bit rate (several kbits / sec, about several tenths of the carrier frequency) is used.
Keying) method, PSK (Pha) that changes phase
se Shift Keying method, ASK (Amplitude Shift Key) for changing amplitude
ing) method is used.

[0007] The coils used in the magnetic field generating circuit 12 and the magnetic field detecting circuit 13 in the RF tag transceiver 1 may be provided separately or may be one common coil. Similarly, the coils used for the magnetic field detection circuit 21 and the magnetic field generation circuit 24 in the RF tag 2 may be provided separately, or may be one common coil.

[0008] Such an RF tag system is widely used by its name such as an ID card, a data carrier, or a transponder.

[0009]

The above-described RF tag 2 is provided on an article. In this case, the RF tag 2 is often of a card type (rectangular parallelepiped) in which a transmission / reception coil is disposed, and the coil of the RF tag 2 and the coil of the RF tag transceiver 1 are easily coupled. In addition, it is common to use both coils so as to face each other in the axial direction.

However, when the article provided with the RF tag 2 has a circular outer shape, for example, a circular dish of a restaurant, the RF tag 2 is embedded in the dish. 2 and the coil of the RF tag transceiver 1 cannot be opposed to each other, so that the electromagnetic induction coupling becomes weak,
Even if the RF tag transceiver 1 is arranged in the lateral (radial) direction of a large number of stacked dishes, there is a problem that the number of RF tags 2 that can communicate at once decreases.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an RF tag transceiver capable of enhancing electromagnetic induction coupling with an RF tag provided on an article having a circular outer shape.

[0012]

To achieve the above object, according to the first aspect of the present invention, the coil (10) of the transceiver for the RF tag is characterized in that it has a curved shape. Thereby, electromagnetic induction coupling with an RF tag embedded in an article having a circular outer shape can be strengthened.

In this case, as in the second aspect of the present invention, the antenna section (101) having the curved surface (101a) is provided.
The coil (10) according to claim 1 can be stored and used therein. Further, in the invention according to claim 3, the temperature of the coil (10) constituting the resonance circuit (301) is detected, and when the temperature of the coil (10) decreases, the loss of the resonance circuit (301) is increased. Because
Even when the usage environment of the RF tag is low, the time constant of the transient phenomenon of the resonance circuit can be set to a predetermined value or less to prevent communication failure.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a diagram showing a state in which coils 10 of an RF tag transceiver 1 are arranged beside a plate 200 in which a large number of coils are stacked, (A) is a plan view, (B) is a front view,
(C) is a side view. FIG. 2 shows the internal structure of the dish 200. In this embodiment, the coil 10 of the RF tag transceiver 1 and the coil 201 of the RF tag 2 are:
One coil is used for both transmission and reception.

As shown in FIG. 1, the coil 10 of the RF tag transceiver 1 has a curved shape, and is disposed beside a large number of stacked dishes 200. This coil 1
The main part of the RF tag transceiver 1 (circuits except for the circuits 12 and 13 of the RF tag transceiver 1 shown in FIG. 6) connected to 0 is omitted. As shown in FIG. 2, the RF tag 2 includes a coil 201 and a main body of the RF tag 2 connected to the coil 201 (circuits 21 and 24 of the RF tag 2 shown in FIG. 6). (Except for the circuit part) 202 are embedded. The coil 201 is formed in a circular shape similar to the outer shape of the dish 200 as shown by a dotted line in FIG.

Here, the mutual inductance between the two coils is calculated by Neumann's formula in electromagnetics (shown in Equation 1).

[0017]

(Equation 1)

In this equation 1, M is a mutual inductor
, Μ is the magnetic permeability of the space containing the coil, c₁Is one of
Integration path along the shape of the il, c_TwoOf the other coil
Integral path along the shape, dl₁Is the integration path c₁Top minute line segment
(Vector), dl_TwoIs the integration path c_TwoThe upper minute line segment
), The operator "." Is a scalar product, r₁₂Is the integration path c ₁
Upper minute line segment dl₁And integration path c₁Upper minute line segment dl₁When
Is the distance. Therefore, the mutual inductance between the two coils
The reactance M is the integration path c₁And integration path c_TwoThe interval between is average
The smaller the target, the larger.

In the present embodiment, as shown in FIG.
Since the coil 10 of the tag transceiver 1 has a curved shape along the outer shape of the plate 200, the average distance between the coil 10 of the RF tag transceiver 1 and the coil 201 embedded in the plate 200 can be reduced. Yes, coil 10 and coil 2
01 can be increased. Since the voltage induced in the coil 201 is proportional to the mutual inductance, the voltage induced in the coil 201 from the coil 10 can be increased. Therefore, as shown in FIG. 1, even when a large number of dishes 200 are placed one on top of another, communication with a large number of RF tags 2 can be performed at once.

Referring to FIG. 3, an RF tag transceiver 1 is connected to a portable remote terminal, a remote handy terminal (hereinafter, RHT).
An embodiment is shown in the case where it is used for (100). (A)
Is a plan view, (B) is a front view, and (C) is a side view. In FIG. 3, the RHT 100 includes an antenna unit 101 and a RHT main unit 102. Antenna unit 1
01 stores the coil 10 having the shape shown in FIG.
The surface 101a that is disposed to face 0 is a curved surface.
The RHT main unit 102 includes a liquid crystal display 102a for displaying communication contents and the like, and operation keys 102b, and internally has functions equivalent to those of the circuit unit excluding the coil of the RF tag transceiver 1 shown in FIG. doing.

Therefore, the antenna unit 1 of the RHT 100
01 is disposed on the side of the plate 200 so as to face the plate 200.
00 and communicate with the RF tag 2 embedded therein to read ID information and the like stored therein. Next, a specific configuration of a circuit that generates a magnetic field using the coils 10 and 201 (the magnetic field generation circuits 12 and 24 illustrated in FIG. 6) will be described. FIG. 4 shows the configuration.

Transmission circuit (transmission circuits 11 and 23 in FIG. 6)
Is input to the input terminal 302, the grounded emitter circuit 303 constituting the current source supplies a current proportional to the voltage input to the input terminal 302 to the resonance circuit 301, and the resonance circuit 301 Is operated in resonance. The resonance circuit 301 includes a transmission coil (corresponding to the coils 10 and 201) 301a and a capacitor 302b.
The specification of the transmission coil 301a is determined such that the time constant of the transient phenomenon of resonance at a high temperature in the temperature range to be used is about the limit limited by the communication speed.

Here, the resonance circuit 301 performs damped oscillation, and the time constant τ of the amplitude attenuation is given by τ = 2L / R, where L is the inductance of the coil and R is the effective resistance of the coil.
It is. When the time constant τ is longer than the transmission time of one bit of the modulation, a defect occurs in the modulation result. In an extreme case, communication becomes impossible. When the use environment of the RF tag 2 is low, the Q of the resonance circuit 301 is increased and the loss is reduced, so that the time of the transient phenomenon of the resonance is lengthened, which causes communication failure.

For this reason, in the present embodiment, a temperature detection circuit 304 and a resistance control circuit 305 are provided. The temperature detection circuit 304 includes a thermistor (temperature detection unit) 304a that is thermally coupled to the transmission coil 301a.
And a bias resistor 304b. The resistance control circuit 305 includes an NPN transistor 305a and a resistor 305b.

When the temperature of the transmission coil 301a is lower than a predetermined temperature, the resistance value of the thermistor 304a thermally coupled to the transmission coil 301a increases, so that the base voltage of the transistor 305a of the resistance control circuit 305 increases. The transistor 305a is turned on, and the resistor 305b is connected to the resonance circuit 301. Thus, the resistor 305
By connecting b in parallel to the resonance circuit 301, it is possible to increase the loss of the resonance circuit 301 and reduce the time of the resonance transient to less than the limit due to the communication speed so that communication failure due to the transient does not occur. it can.

When the resistor 305b is connected in parallel with the resonance circuit 301 (in an AC manner), the transistor 305
a, but a relay or power MOSFET
You may make it use switch means of low impedance, such as T. Further, a thermistor 3 is used as a temperature detecting means.
Although the temperature sensor using 04a has been described, another temperature sensor such as a temperature-sensitive reed switch may be used.

Further, as shown in FIG. 5, the resistance value is several k.
A temperature-sensitive element (positive-characteristic thermistor PTC or the like having a predetermined Curie temperature) 306 having a characteristic of Ω to several hundred kΩ and having a positive temperature coefficient is used.
You may make it connect in parallel with a. Further, the temperature compensation of the resonance circuit described above can be performed not only in the magnetic field generation circuits 12 and 24 but also in the magnetic field detection circuits 13 and 21.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a coil of an RF tag transceiver according to an embodiment of the present invention is arranged beside a multiplicity of stacked dishes.

FIG. 2 is a diagram showing a cross-sectional configuration of the dish shown in FIG.

FIG. 3 is a diagram showing an embodiment in which the present invention is applied to a portable remote terminal RHT.

FIG. 4 is a diagram showing a specific configuration of a circuit for generating a magnetic field by a coil in the embodiment shown in FIGS. 1 and 3;

FIG. 5 shows another embodiment of the one shown in FIG.

FIG. 6 is a diagram showing a block configuration of an electromagnetic induction type RF tag system.

[Explanation of symbols]

1: RF tag transceiver, 2: RF tag, 10, 201 ...
Coil, 100 RHT, 101 Antenna, 301
... Resonant circuit, 301a coil, 301b capacitor, 304 temperature detecting circuit, 304a thermistor, 3
05: resistance control circuit, 306: temperature-sensitive element.

Claims (3)

[Claims] An RF tag transceiver including a coil (10) for performing communication by electromagnetic induction with an RF tag (2) provided on an article (200), wherein the coil (10) ) Has a curved shape. 2. An antenna unit (101) for accommodating the coil (10), the antenna unit (101) having a curved surface (101) facing the article (200).
R according to claim 1, characterized in that: a)
Transceiver for F tag. 3. A resonance circuit (301) including the coil (301a) and a capacitor (301b);
Detecting the temperature of the coil (10) and detecting the temperature of the coil (10);
3. The RF tag transceiver according to claim 1, further comprising means (304, 305, 306) for increasing a loss of the resonance circuit (301) when the temperature of the RF tag decreases.