JPH11313018A - Transmission circuit and transmission method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve power efficiency when transmitting a reply from a tag to a reader / writer. SOLUTION: An alternating magnetic field supplied from a lead writer side is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and a weight of a load connected to both ends of the antenna circuit is switched. An impedance switching means (4, 5) for changing the impedance of the antenna circuit 1 in accordance with the content of data transmitted to the reader / writer in a transmission circuit returning a reply from the tag to the reader / writer; Control means for controlling a switching operation of the impedance switching means so as to control a frequency of a signal transmitted from the antenna circuit 1 to be a subcarrier frequency of a frequency of an alternating magnetic field supplied from the lead writer side. It is provided so that a carrier that is not received by the reader / writer is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit and a transmission method, and more particularly, to a data structure in which a tag operates using an alternating magnetic field transmitted from a reader / writer side as an operation power source and returns a reply to the reader / writer side. It is suitable for use in a carrier system.

[0002]

2. Description of the Related Art Conventionally, in a data carrier system, an alternating magnetic field supplied from a transmission antenna on a reader / writer side is received by an antenna coil built in a tag side to generate an induced voltage, which is rectified to rectify the induced voltage. And the tag receives the signal transmitted from the reader / writer side by modulating the alternating magnetic field.

That is, in such a data carrier system, since an operation power supply is not built in the tag side, the power available on the tag side is very small, and is usually several mW or less in many cases.

Since the power available on the tag side is proportional to the strength of the alternating magnetic field sent from the reader / writer side, when the distance between the tag and the reader / writer is short, the antenna circuit on the tag side is used. In this case, a strong alternating magnetic field can be obtained, so that large power can be obtained.

However, when the distance between the tag and the read writer is long, the induced voltage generated in the coil of the antenna circuit built in the tag side becomes small, so that the power available on the tag side becomes small. Become. Therefore, in order to extend the communication distance between the reader / writer and the tag,
It is required that the tag side operates with very small power.

On the other hand, in order to reliably transmit and receive information in the data carrier system, it is necessary to output a signal stronger than ambient noise from the tag side. However, outputting a strong signal consumes a large amount of power, and there is a limit to increasing the signal transmitted from the tag side. Therefore, the power consumption of the tag side and the signal strength at the time of transmitting the reply are determined in a balanced manner.

FIG. 6 shows a conventional example of a transmission circuit provided in a tag. Generally, using a circuit called a load switch SW, the weight of a load _RL connected to the antenna circuit 1 built in the tag is periodically changed, and an alternating current supplied from a lead writer (not shown) is used. An operation of applying amplitude modulation to a signal induced from a magnetic field is performed.

For example, as shown in FIG. 7, when the load switch SW is turned on and off by a square wave of the frequency fS to the frequency (fR) signal of the alternating magnetic field sent from the read / writer side, "f
R ± fS ”is generated. The lead writer side detected the presence or absence of the signal and a change in phase and received a signal from the tag.

As described above, the reply signal is transmitted from the tag side to the reader / writer side. On the reader / writer side, one of the two frequency signals of “fR ± fS”, that is, , “FR + fS” or one of the signals “fR−fS”. Of course, to improve communication accuracy,
Although signals of both frequencies can be received, generally only signals of one frequency are selected and received.

[0010]

Therefore, in the conventional data carrier system, a reply signal is generated even on one frequency not used for reception, and a reply signal on a frequency not used for reception is generated. Power was wasted.

[0011] This means that the power efficiency when transmitting a reply from the tag side to the reader / writer side is reduced. The present invention has been made in consideration of the above-described problem, and has as its object to improve power efficiency when a reply is transmitted from a tag to a reader / writer.

[0012]

The transmitting circuit of the present invention receives an alternating magnetic field supplied from a reader / writer side by an antenna circuit built in the tag side to obtain an operating power supply on the tag side, and obtains the above-mentioned antenna circuit. In a transmission circuit used in a data carrier system that returns a reply from the tag side to the read writer side by switching the weight of a load connected to both ends of the antenna, the impedance of the antenna circuit is transmitted to the read writer side. Impedance switching means for changing in accordance with the content of data to be transmitted, and controlling the switching operation of the impedance switching means, so that the sub-carrier generated below the frequency of the alternating magnetic field supplied from the lead writer side is transmitted to the antenna circuit. And control means for performing control so as to generate the data. Another feature of the transmission circuit of the present invention is that an alternating magnetic field supplied from a read / writer side is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and the antenna circuit In the transmission circuit used in the data carrier system that returns a reply from the tag side to the read writer side by switching the weight of the load connected to both ends of the first antenna circuit, the first circuit connected to one end of the antenna circuit And a load circuit comprising a second load connected to the other end of the antenna circuit and a first end of the antenna circuit intermittently connected to a predetermined potential through the first load. A second interrupting circuit for interrupting the other end of the antenna circuit to a predetermined potential via the second load; and a second interrupting circuit for operating the interrupting means. Detecting means for generating a timing signal corresponding to the peak of the alternating magnetic field supplied from the lead writer, and an alternating signal supplied from the reader / writer in response to the timing signal generated by the timing detecting means. Frequency dividing means for dividing the frequency of the magnetic field, wherein the first intermittent circuit and the second
The intermittent operation of the intermittent circuit is controlled to change the impedance of the antenna circuit, and the subcarrier generated below the frequency of the alternating magnetic field supplied from the read writer side is generated by the antenna circuit to generate the subcarrier. It is characterized by responding to the side.

According to the transmission method of the present invention, an alternating magnetic field supplied from a reader / writer is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and is connected to both ends of the antenna circuit. By switching the weight of the load, in the transmission method used in the data carrier system that returns a reply from the tag side to the read writer side, the impedance of the antenna circuit according to the content of the data transmitted to the read writer side It is characterized by performing an impedance switching process for changing the impedance and a control process for controlling the sub-carrier generated below the frequency of the alternating magnetic field supplied from the read / writer side by the antenna circuit. Another feature of the transmission method of the present invention is that an alternating magnetic field supplied from the read / writer side is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and the antenna circuit In a transmission method used in a data carrier system that returns a reply from the tag side to the read writer side by switching the weight of a load connected to both ends of the antenna circuit, the first side connected to one end of the antenna circuit A first disconnection process for disconnecting one side end of the antenna circuit to a predetermined potential via a load of the antenna circuit, and a first disconnection process of the antenna circuit via a second load connected to the other side end of the antenna circuit. A second interrupting process for interrupting the other end to a predetermined potential, and a timing signal for performing the interrupting process corresponding to a peak of an alternating magnetic field supplied from the lead writer side. And a frequency dividing process for dividing the frequency of the alternating magnetic field supplied from the lead writer side in accordance with the timing signal generated by the timing detecting process. The frequency of the divided frequency controls the intermittent operation in the first and second intermittent processes to change the impedance of the antenna circuit, and the frequency is changed below the frequency of the alternating magnetic field supplied from the lead writer. It is characterized in that generated subcarriers are generated by the antenna circuit and respond to the read writer side.

[0014]

Since the present invention has the above technical means, a load is connected to each of one end and the other end of the antenna circuit of the tag, and the one end and the other end of the antenna circuit are independently intermittently connected. By doing so, it is possible to perform intermittent control corresponding to the polarity of the alternating magnetic field induced at one end of the antenna circuit and the polarity of the alternating magnetic field induced at the other end. Generation of unused frequencies is suppressed, and power efficiency is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a transmission circuit and a transmission method according to the present invention will be described with reference to the drawings. FIG.
1 is a circuit diagram illustrating a schematic configuration of a transmission circuit according to the present embodiment. As shown in FIG. 1, the transmission circuit according to the present embodiment includes:
An alternating magnetic field supplied from the read writer side is received by the antenna circuit 1 including the coil L ₁ and the capacitor C ₁ to obtain an operation power supply on the tag side.

[0016] Then, the induced voltage in the antenna circuit 1, the four diodes full-wave rectified by full-wave rectifying circuit 2 and formed by bridge connection, such as an internal circuit 3 which are stored in the capacitor C _P It is the operating power supply.

In the present embodiment, it is connected to ground CG _ND via the series circuit of the resistors one end S ₁ of the antenna circuit 1 R ₁ and transistor T _r1. Also,
The other end S ₂ via a series circuit of resistors R ₂ and transistor T _r2 is connected to ground CG _ND.

The above resistor R₁And R_TwoIs the antenna circuit
1 of the load circuit 4.
T_r1And T_r2Is a component of the intermittent circuit 5. Book
In the embodiment, as described above, one side end S₁And the other side
Edge S_TwoResistor R ₁, R_TwoAnd transistors
T_r1, T_r2To provide the one side end S₁And others
Side end S_TwoIs the ground point CG_NDIndependently
It is made to continue.

The resistors R ₁ and R ₂ and the transistor T
_r1 and _Tr2 constitute an impedance switching means for changing the impedance of the antenna circuit 1 in accordance with the content of data to be transmitted to the reader / writer.

The timing detecting circuit 6, the first frequency divider 7a and the second frequency divider 7b, and the multiplexer 8 constitute a control means for controlling the switching operation of the impedance switching means.

The timing detection circuit 6 includes the antenna circuit 1
To detect the peak of the alternating magnetic field induced by
It is configured as shown in FIG. In other words, between the one end of the antenna circuit 1 S ₁ and the ground point CG _ND resistor 1
Delay filter 10 comprising a capacitor 1 and a capacitor 12
Is connected, and a second delay filter 20 including a resistor 21 and a capacitor 22 is connected between the other end S ₂ and the reference potential point CG _ND .

The resistor 11 and the capacitor 1
The signal extracted from the connection point 2 is the comparator COM
The signal supplied to the positive input terminal of P1 and taken out from the connection point between the resistor 21 and the capacitor 22 is a comparator C
It is provided to the negative input terminal of OMP1.

FIG. 3 shows operation waveforms of the timing detection circuit 6 configured as described above. As shown in FIG. 3 (b), the signal applied between the one side end S ₁ and the other end S ₂ is an AC waveform, between the one side end S ₁ and the reference potential point CG _ND the first half-wave rectified signal is output to the second half-wave rectified signal is output between the other end S ₂ and the reference potential point CG _ND.

The phases of the first half-wave rectified signal and the second half-wave rectified signal are opposite to each other. FIG.
As shown in (e) and (f), the delay amount of the first delay filter 10 and the delay amount of the second delay filter 20 need not be large.

For example, since the period of the input signal frequency may be about the same, a large capacity is not required to realize the timing detection circuit 6 of the present embodiment. Further, even if the delay time varies, there is little effect on the inversion timing of the two waveforms, so that there is an advantage that an accurate inversion timing can be detected.

With the above configuration, the inversion timing of "H" / "L" of the output c of the comparator COMP1 is substantially the timing of the peak of the input signal waveform as shown in FIG. ing. Since this is true regardless of the amplitude of the input signal, accurate timing detection can be performed. The timing detection operation can be further stabilized by adding hysteresis to the operation of the comparator COMP1.

As described above, the transmission circuit of the present embodiment generates a timing signal that matches the timing at which the signal received by the tag reaches a peak value from the alternating magnetic field from the reader / writer.

The first frequency divider 7a for generating the timing signal operates at the timing of the rising edge of the timing signal which coincides with the timing when the input signal reaches the peak value. Further, the second frequency divider 7b operates at the falling timing of the timing signal that matches the timing when the signal reaches the peak value.

[0029] Then, by the control signal of the first frequency divider one end of Q1 signal and QB1 signal 7a S _1, transistor T _r1 other end S ₂ side, T _r2, lead writer A reply signal is sent to. Incidentally, it is possible to reverse the phase of the reply signal by switching the control signal of the transistor T _r1, T _r2 intermittently one side end S _1, the other end S _2.

Similarly, the Q2 signal of the second frequency divider 7b and Q2
The B2 signal, capable of transmitting signals reply at each one side end S _1, the control signals of the other end S ₂ side transistor T _r1, T _r2 possible. Also in this case, one end S ₁ and the other end S
It is possible to reverse the phase of the reply signal by switching the control signal of the transistor T _r1, T _r2 intermittently _2.

Further, outputs Q1 and Q2, and output QB
If the operation of replacing 1 and QB2 is performed, the 4-phase PSK (Q
(PSK) modulation, and a reply signal can be sent to the reader / writer side.

FIG. 4 is a waveform chart showing the operation of each part of the transmission circuit shown in FIG. In FIG. 4, (a) shows a waveform of a signal induced in the antenna circuit 1, and a hatched portion indicates a period during which a signal from the tag side of this embodiment is actually transmitted to the reader / writer side. Is shown.

FIG. 4B shows a timing detection signal output from the timing detection circuit 6, which detects the peak voltage of the input signal waveform.

FIG. 4C shows a signal waveform output from the first frequency divider 7a, and FIG. 4D shows a signal waveform output from the second frequency divider 7b. It has been a control signal supplied to the gate of the transistor T _r1, T _r2. Since the second frequency divider 7b receives a signal from the timing detection circuit 6 via the delay inverter 9, the signal waveform of FIG. 4D is delayed by a half cycle with respect to the signal waveform of FIG. ing.

[0035] As shown in FIG. 4, in the transmission circuit of the present embodiment, the first transistor T _r1 is ON in the positive potential region of the first half of the signal transmitted to the reader and writer side
Operates, and in the second half negative region, the second transistor _Tr2
Turns ON.

By operating as described above, the transmission circuit of the present embodiment can generate only a signal component having a half frequency of the input signal and transmit a reply to the reader / writer. As a result, current consumption for signal components that are not received by the reader / writer can be reduced, so that power efficiency when transmitting a reply to the reader / writer can be greatly improved, and communication distance can be greatly increased. be able to.

When the same power is consumed as in the conventional case, a stronger signal than in the conventional case can be returned to the reader / writer side, so that the reliability of data transfer can be greatly improved. Further, since the transmission circuit of the present embodiment can be realized by a standard CMOS circuit,
It is suitable for implementing an IC for data carry.

In the above embodiment, a circuit for generating a timing signal using the two frequency dividers 7a and 7b is configured. However, as shown in FIG. 5, the frequency divider 7a, the D flip-flop 11, the multiplexer 12, inverter 10,
13 can be used.

In the above embodiment, an example has been described in which the intermittent control is performed at half the frequency transmitted from the reader / writer, but the frequency at which the intermittent control is performed is limited to ２. N / m (n,
m may be a natural number).

[0040]

According to the present invention, it is possible to reduce the current consumption for generating a signal component that is not received on the read writer side, so that the communicable distance between the read writer and the tag can be greatly increased. . Further, a signal stronger than before can be returned using the same power consumption as before, and the reliability of data transfer can be greatly improved. Further, since the circuit of the present invention can be realized by a standard CMOS circuit, the data carry can be suitably formed into an IC.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a schematic configuration of a tag according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a timing detection circuit in FIG.

FIG. 3 is a waveform chart for explaining an operation of the timing detection circuit of FIG. 2;

FIG. 4 is a waveform chart for explaining an operation of the transmission circuit according to the embodiment;

FIG. 5 is a circuit diagram showing a modification of the tag.

FIG. 6 is a circuit diagram illustrating an example of a conventional transmission circuit.

FIG. 7 is a waveform chart showing an operation of the transmission circuit of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Antenna circuit 2 Full-wave rectifier circuit 3 Internal circuit 4 Load circuit 5 Intermittent circuit 6 Timing detection circuit 7a 1st frequency divider 7b 2nd frequency divider 8 Multiplexer 9 Delay inverter R ₁ , R ₂ resistor S ₁ Side end S ₂ Other side end C G _ND Ground potential

Claims (4)

[Claims] An alternating magnetic field supplied from a reader / writer is received by an antenna circuit built in a tag side to obtain an operation power supply on the tag side, and the weight of a load connected to both ends of the antenna circuit is reduced. By switching, in a transmission circuit used in a data carrier system that returns a reply from the tag side to the read writer side, impedance switching for changing the impedance of the antenna circuit according to the content of data transmitted to the read writer side Means, and control means for controlling the switching operation of the impedance switching means, and controlling the sub-carrier generated below the frequency of the alternating magnetic field supplied from the lead writer side to be generated by the antenna circuit. A transmission circuit, comprising: 2. An alternating magnetic field supplied from a lead writer side is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and the weight of a load connected to both ends of the antenna circuit is reduced. In a transmission circuit used in a data carrier system that returns a reply from the tag side to the read writer side by switching, a first load connected to one end of the antenna circuit, and another end of the antenna circuit A load circuit comprising a second load connected to the first load, a first interrupting circuit for interrupting one end of the antenna circuit to a predetermined potential via the first load, and the second load A second interrupting circuit for interrupting the other end of the antenna circuit to a predetermined potential via a second interrupting circuit; and a timing signal for operating the interrupting means. A timing detecting means for generating a peak corresponding to an alternating magnetic field supplied from the iter side; and dividing a frequency of the alternating magnetic field supplied from the lead writer side in accordance with a timing signal generated by the timing detecting means. Frequency dividing means for controlling the gating operation of the first gating circuit and the second gating circuit at the frequency divided by the frequency dividing means to change the impedance of the antenna circuit, A sub-carrier generated below the frequency of the alternating magnetic field supplied from the side, generated by the antenna circuit, and responding to the read-writer side. 3. An alternating magnetic field supplied from a lead writer side is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and the weight of a load connected to both ends of the antenna circuit is reduced. In a transmission method used in a data carrier system that returns a reply from the tag side to the read writer side by switching, an impedance switching process that changes the impedance of the antenna circuit according to the content of data transmitted to the read writer side And a control process of controlling the sub-carrier generated below the frequency of the alternating magnetic field supplied from the read / writer side by the antenna circuit. 4. An alternating magnetic field supplied from a read writer side is received by an antenna circuit built in the tag side to obtain an operation power supply on the tag side, and the weight of a load connected to both ends of the antenna circuit is reduced. In the transmission method used in the data carrier system which returns a reply from the tag side to the read writer side by switching, one side of the antenna circuit via a first load connected to one side end of the antenna circuit A first disconnection process for disconnecting the terminal to a predetermined potential, and disconnecting the other end of the antenna circuit to a predetermined potential via a second load connected to the other end of the antenna circuit A second intermittent process, and a timing detection process for generating a timing signal for performing the intermittent process in accordance with a peak of an alternating magnetic field supplied from the lead writer side. Performing a frequency dividing process for dividing the frequency of the alternating magnetic field supplied from the lead writer side in accordance with the timing signal generated by the timing detecting process, and performing the frequency dividing by the frequency dividing process by the frequency dividing process. Controlling the gating operation in the first gating process and the second gating process to change the impedance of the antenna circuit, and changing the subcarrier generated below the frequency of the alternating magnetic field supplied from the lead writer side to the antenna circuit And transmitting a response to the reader / writer side.