JP2018098650A - Reader/writer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To widen rating of a demodulation circuit that is applicable to a reader/writer.SOLUTION: A reader/writer 1 comprises: a carrier generation part 2; an antenna 6; a frequency setting part 3 for setting a frequency of a carrier signal that is generated by the carrier generation part 2; an amplifier 4; a carrier control part 5 which controls the frequency setting part 3; and a demodulation circuit 9. The demodulation circuit 9 includes an envelope detection part 7 and a converter 8 into which an analog signal from the envelope detection part 7 is input and which outputs a digital signal corresponding to the analog signal. When transmitting a carrier signal for power charge from the antenna 6 to a tag 10, the carrier control part 5 causes the frequency setting part 3 to divide the frequency of the carrier signal into multiple steps and increase the frequency of the carrier signal step by step, such that the frequency of the carrier signal is increased gradually to a specified frequency.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reader / writer that performs data communication with a tag, and more particularly to a technique for controlling the frequency of a carrier signal.

  As a reader / writer, for example, as shown in Patent Document 1 below, a reader / writer that transmits a carrier wave signal modulated according to data to be communicated from an antenna is known. The tag receives and demodulates this carrier wave signal, and generates and holds data to be communicated. Also, in such a reader / writer, for example, as shown in Patent Document 2 below, a demodulation circuit that receives a subcarrier signal from a tag and demodulates data to be communicated from the received subcarrier signal. Is provided.

JP 2012-198872 A Japanese Patent No. 3017757

  By the way, in the conventional reader / writer shown in each of the above patent documents, in general, a demodulation circuit having a rating capable of withstanding the voltage generated based on the inrush current generated immediately after transmitting the carrier wave signal is considered. Was adopted. For this reason, in the conventional reader / writer, the demodulating circuits that can be employed are limited or expensive.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to expand the rated range of a demodulator circuit applicable to a reader / writer.

  A reader / writer according to one aspect of the present invention is a reader / writer that performs data communication with a tag, and transmits a carrier signal to the tag, a carrier wave generation unit that generates a carrier wave signal, and from the tag An antenna for receiving the subcarrier signal, a frequency setting unit which is provided between the carrier generation unit and the antenna and sets the frequency of the carrier signal generated by the carrier generation unit, and controls the frequency setting unit And a demodulation circuit that demodulates a subcarrier signal received by the antenna, the demodulation circuit receiving a carrier signal transmitted from the antenna and a subcarrier signal received by the antenna. And a detector that outputs an analog signal corresponding to the envelope of the received signal, and an analog signal from the detector. A converter that outputs a digital signal corresponding to an analog signal, and the control unit transmits the carrier signal for power charging from the antenna to the tag by the frequency setting unit. This frequency is gradually increased to a specified frequency by increasing the frequency in stages in a plurality of stages.

  ADVANTAGE OF THE INVENTION According to this invention, the range of the rating of the demodulation circuit applicable to a reader / writer can be expanded.

It is a block diagram which shows the principal part structure of the reader / writer which concerns on one Embodiment of this invention. (A) And (B) is a timing chart which respectively shows the voltage which generate | occur | produces based on the carrier wave signal after amplification and the inrush current in the reader / writer of this embodiment. (A) And (B) is a timing chart which respectively shows the voltage which generate | occur | produces based on the carrier wave signal after amplification and the inrush current in a comparative example.

  Hereinafter, a reader / writer according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a main configuration of a reader / writer according to an embodiment of the present invention. The reader / writer 1 of the present embodiment performs data communication with a passive tag 10. The reader / writer 1 modulates the carrier wave signal according to the data to be communicated or the power charge of the tag 10 and transmits the modulated carrier wave signal to the tag 10. The reader / writer 1 demodulates the subcarrier signal received from the tag 10 to generate data to be communicated. The reader / writer 1 and the tag 10 constitute a radio tag communication system using RFID (Radio Frequency Identification).

  In addition, the reader / writer 1 of this embodiment performs data communication using, for example, ASK (Amplitude Shift Keying) modulation. Thereby, in this embodiment, the circuit configuration of the reader / writer 1 can be simplified as compared with the case where data communication using conventional amplitude modulation or the like is performed.

  Similarly, the tag 10 also modulates the subcarrier signal in accordance with the data to be communicated, transmits the modulated subcarrier signal to the reader / writer 1, and demodulates the carrier signal received from the reader / writer 1. Generate data.

  Here, although the frequency of the subcarrier signal is different from the frequency of the carrier signal, even if the frequency of the subcarrier signal is the same as the frequency of the carrier signal, that is, the reader / writer 1 and the tag 10 have the same frequency. You may send and receive signals.

  As shown in FIG. 1, the reader / writer 1 includes a carrier generation unit 2, a frequency setting unit 3, an amplifier 4, a carrier control unit 5, an antenna 6, an envelope detection unit 7, a converter 8, and capacitors C1, C2, etc. It is configured with. In the reader / writer 1, the envelope detector 7, the converter 8, and the capacitor C <b> 2 constitute a demodulation circuit 9 that demodulates the subcarrier signal from the tag 10 received by the antenna 6. The converter 8 can be an operational amplifier or a comparator. The amplifier 4 can be a transistor, an inverter, an operational amplifier, or the like.

  The carrier wave generation unit 2 includes an oscillation circuit (not shown). The carrier wave generation unit 2 generates a carrier wave signal having a predetermined frequency (for example, 13.56 MH or less).

  The frequency setting unit 3 determines the frequency of the carrier signal in advance by increasing the frequency of the carrier signal input from the carrier generation unit 2 in a plurality of stages according to the frequency level switching signal output from the carrier control unit 5. Set to the specified frequency. For example, the frequency setting unit 3 changes the frequency level of the carrier wave signal at two levels. The frequency setting unit 3 outputs the changed carrier wave signal to the amplifier 4. The frequency setting unit 3 increases the frequency of the carrier signal input from the carrier wave generation unit 2 by a predetermined value every time the frequency level switching signal is input from the carrier wave control unit 5. The maximum frequency set by the frequency setting unit 3 is a specified frequency (for example, 13.56 MHz) used for communication with the tag 10. That is, the frequency setting unit 3 gradually increases the frequency of the carrier wave signal input from the carrier wave generation unit 2 to the specified frequency by increasing the frequency in a plurality of stages.

  The amplifier 4 amplifies the amplitude of the carrier signal output from the frequency setting unit 3. The amplifier 4 is switched to an on state or an off state based on an instruction signal from the carrier wave control unit 5. When switched on, the amplifier 4 amplifies the amplitude of the carrier signal and outputs a carrier signal. When switched off, the amplifier 4 does not amplify the amplitude of the carrier signal. Output. That is, the amplifier 4 is configured to perform the ASK modulation, and the amplifier 4 sets the amplitude level of the carrier wave signal (that is, the voltage level of the carrier wave signal) in accordance with the instruction signal from the carrier wave control unit 5. Amplified (modulated) and output to H level (High level; voltage level for charging power of tag 10) or L level (Low level; generic name for each amplitude level when modulating according to data to be communicated) To do.

  The carrier wave control unit 5 is configured using a processor such as a CPU (Central Processing Unit), an MPU, and an ASIC, and controls the frequency setting unit 3 and the amplifier 4. Specifically, the carrier wave control unit 5 outputs the frequency level switching signal to the frequency setting unit 3 when generating a carrier signal for charging the power of the tag 10. The carrier wave control unit 5 sets the amplifier 4 in the on state or the off state depending on whether or not to generate a carrier signal for charging the power of the tag 10. That is, the carrier wave control unit 5 controls the amplification factor of the amplifier 4 in accordance with whether or not to generate a carrier signal for charging the power of the tag 10, so that the H level or L level carrier signal is output from the amplifier 4. Output. The carrier wave control unit 5 is an example of a control unit in the claims.

  The antenna 6 is used for both transmission and reception, and transmits the carrier wave signal amplified by the amplifier 4 to the tag 10 and receives the subcarrier signal from the tag 10.

  The carrier signal output from the amplifier 4 and transmitted from the antenna 6 and the subcarrier signal received by the antenna 6 are input to the envelope detector 7 via the capacitor C1. The envelope detector 7 is configured by using a voltage doubler circuit, inputs a carrier wave signal and a subcarrier signal as a received signal, extracts an envelope of the received signal, and outputs an analog signal corresponding to the envelope To do.

  The high frequency component of the analog signal corresponding to the envelope output from the envelope detector 7 (signal corresponding to the rising and falling of the envelope) is applied to the converter 8 through the capacitor C2. A pair of input terminals of the converter 8 is applied with a signal corresponding to the rise and fall of the envelope and a DC offset voltage vf due to voltage division, and from the output terminal of the converter 8 a digital corresponding to the envelope. A signal is output. The envelope detector 7 is an example of a detector in the claims.

The tag 10 includes a memory 31, a communication control unit 32, and an antenna 33.
The memory 31 stores data obtained by demodulating the carrier wave signal from the reader / writer 1. The communication control unit 32 controls communication with the reader / writer 1. The antenna 33 transmits / receives information to / from the reader / writer 1 by transmitting / receiving carrier waves and subcarriers.

  Here, in the reader / writer 1, at the start of data communication between the reader / writer 1 and the tag 10, the carrier wave control unit 5 switches the amplifier 4 from the off state to the on state. As a result, a carrier signal having an H level amplitude is output from the amplifier 4 as a carrier signal for charging the power of the tag 10. The carrier wave signal having the amplitude of H level is transmitted from the antenna 6 to the tag 10. The carrier wave signal (radio wave) is received by the antenna 33 of the tag 10, and the tag 10 is precharged (power charged) by the power of the carrier wave signal, so that the tag 10 becomes operable.

  In the reader / writer 1, the carrier wave control unit 5 controls the amplification factor of the amplifier 4 according to whether or not the carrier signal for power charging of the tag 10 is generated, and the amplitude of the carrier wave signal output from the amplifier 4. Modulate the level to H level or L level. This modulated carrier wave signal is transmitted from the antenna 6. In the tag 10, when a carrier wave signal (radio wave) having an H level amplitude is received by the antenna, power charging is performed. When a carrier wave signal (radio wave) having an L level amplitude is received by the antenna, The carrier signal is demodulated, and a digital signal indicating data to be communicated is generated and stored in the memory 31.

  That is, in the reader / writer 1, during the period of receiving data from the tag 10, the carrier wave control unit 5 outputs, for example, an L level carrier signal from the amplifier 4, and this L level carrier signal is transmitted from the antenna 6. The In the tag 10, a subcarrier signal modulated according to data to be transmitted to the reader / writer 1 is generated by reflection of a carrier wave signal (radio wave) at the antenna on the tag 10 side, load control of the antenna, and the like. The subcarrier signal is transmitted from the antenna 33 to the reader / writer 1.

  In the reader / writer 1, the L level carrier signal output from the amplifier 4 and the subcarrier signal modulated by the tag 10 and received by the antenna 6 are input to the envelope detector 7 via the capacitor C 1. The envelope detector 7 receives these carrier signals and subcarrier signals as received signals, extracts the envelope of the received signals, and outputs an analog signal corresponding to the envelope. At this time, the carrier signal output from the amplifier 4 is at L level, and the subcarrier signal received by the antenna 6 is modulated, so that the envelope changes the level of the subcarrier signal received by the antenna 6. It will be corresponding. Then, a high-frequency component of the analog signal corresponding to the envelope, that is, a signal corresponding to the rising and falling of the envelope of the subcarrier signal is applied to the converter 8 through the capacitor C2. Thus, a digital signal indicating data from the tag 10 is output from the output terminal of the converter 8.

  Here, when the power of the tag 10 is charged, when the amplifier 4 is switched from the off state to the on state and the transmission (output) of the carrier wave signal having the amplitude H level from the antenna 6 is started, the output of the amplifier 4 is 0. Therefore, an inrush current is generated corresponding to the rise of the output of the amplifier 4, and a voltage generated due to the inrush current is applied to the converter 8 through the capacitor C2.

  Therefore, in the reader / writer 1, when the carrier wave control unit 5 transmits the carrier signal for power charging from the antenna 6 to the tag 10, the frequency setting unit 3 divides the frequency of the carrier signal into a plurality of stages. And gradually increase to a specified frequency. In the present embodiment, the frequency setting unit 3 increases the frequency of the carrier signal from the carrier wave generation unit 2 in two steps to increase it to a prescribed frequency.

  For example, as shown in FIG. 2A, in the reader / writer 1, the amplitude of the carrier wave signal is amplified from the time t0 when the amplifier 4 is turned off to the time t1 when the amplifier 4 is turned on. Inrush current is not generated.

  Then, the carrier wave control unit 5 sends the frequency level switching signal to the frequency setting unit 3 from the time point t1 to the time point t2 when the frequency level switching signal is output to the frequency setting unit 3, and the carrier wave generation unit The frequency f1 (FIG. 2A) of the carrier signal h1 from 2 is changed to a predetermined frequency smaller than the predetermined frequency. The frequency setting unit 3 outputs the carrier signal h1 after the frequency change to the amplifier 4.

  When the time further elapses and time t2 is reached, the carrier wave control unit 5 further sends a frequency level switching signal to the frequency setting unit 3 at this time. In accordance with this frequency level switching signal, the frequency setting unit 3 changes the frequency f1 of the carrier wave signal h1 to the frequency f2 (FIG. 2A) which is the predetermined frequency. The frequency setting unit 3 outputs the carrier signal h2 after the frequency change to the amplifier 4.

  Here, since the frequency f1 is smaller than the prescribed frequency f2, the frequency level of the carrier wave signal h1 is lower than the frequency level of the carrier wave signal h2. That is, in the demodulation circuit 9, the number of carrier signal inputs per unit time input from the amplifier 4 via the capacitor C1 is reduced from the number of inputs after time t2 between time t1 and time t2. It will be. Therefore, as shown in FIG. 2B, the voltage v1 generated based on the inrush current applied to the converter 8 at the rising edge of the carrier signal h1 at the time point t1 is avoided from being steep, and the voltage v1 is It can be kept low.

  Further, the rising width of the carrier wave signal h2 at the time point t2 corresponds to the difference between the level of the carrier wave signal h1 and the level of the carrier wave signal h2. Also, the voltage v2 generated on the basis of the inrush current applied to the converter 8 is suppressed to a low level. Furthermore, since the voltage v1 generated based on the inrush current decreases from the time point t1 to the time point t2, the voltage v2 generated based on the inrush current at the time point t2 is generated based on the reduced inrush current. Even if it is superimposed, the voltage generated based on the inrush current that is superimposed can be prevented from exceeding the rated voltage vd of the converter 8. That is, even if the voltage level of the carrier wave signal is increased by setting the amplifier 4 to the H level, the voltage generated based on the inrush current is increased by the stepwise increase in frequency in this way, so that the rated voltage vd of the converter 8 is increased. It becomes possible to prevent exceeding.

  As described above, in the reader / writer 1 of the present embodiment, the maximum value of the voltage generated based on the inrush current generated in the demodulation circuit 9 when the carrier wave signal is output can be suppressed. 9, it is not necessary to separately provide suppression components (capacitors, resistors, etc.) in order to suppress the voltage generated based on the inrush current, or to use an expensive converter with a large rated voltage vd. 9 can be simplified, and the cost can be reduced and an inexpensive demodulator circuit 9 can be configured. That is, according to this embodiment, the rated range of the demodulation circuit 9 applicable to the reader / writer 1 can be expanded.

  3A and 3B are timing charts showing voltages generated based on the amplified carrier wave signal and the inrush current in a general reader / writer as a comparative example. As shown in FIG. 3A, in a general reader / writer that does not have the frequency setting unit 3 as described above, a carrier wave signal having a predetermined frequency f2 is directly output from the carrier wave generation unit to the amplifier and demodulated. Since the voltage is input to the circuit, the voltage v3 generated based on the inrush current becomes steep at the time point t1 when the amplifier is turned on. Therefore, the value suddenly increases as the rated voltage vd of the converter 8. A rating that can withstand the voltage based on the inrush current is required. On the other hand, according to the above-described embodiment, when the carrier wave signal is amplified by the amplifier 4 when transmitting the carrier signal for power charging to the tag 10, the frequency is divided into two stages and increased to a fixed frequency. Therefore, even if an inrush current occurs, the value thereof is reduced as compared with the comparative example, so that the rated width of the converter 8 applicable as the demodulation circuit 9 is expanded.

  In the present embodiment, the frequency setting unit 3 increases the frequency of the carrier signal in two stages. However, the present invention is not limited to this, and the frequency of the carrier signal output to the amplifier is defined. There is no limitation as long as the frequency is gradually increased to the frequency.

  In the above description, the configuration in which the carrier wave control unit (control unit) controls the frequency setting unit and the amplifier has been described. However, the present invention is not limited to this. For example, two different control units are provided. A configuration may be provided in which the frequency setting unit and the amplifier are controlled independently of each other using these two control units.

  In the above description, the configuration for performing data communication using ASK modulation has been described. However, the present invention is not limited to this. For example, the amplification factor of the amplifier is set in three stages other than H level and L level. A configuration in which data communication using conventional amplitude modulation for modulating a carrier wave signal is performed by changing as described above may be used.

  Moreover, the structure and process demonstrated using FIG. 1 thru | or FIG. 3 are only one Embodiment of this invention, and are not the meaning which limits this invention to the said structure and process.

1 Reader / Writer 2 Carrier Generation Unit 3 Frequency Setting Unit 4 Amplifier 5 Carrier Control Unit (Control Unit)
6 Antenna 7 Envelope detector (detector)
8 Converter 9 Demodulator 10 Tag

Claims (1)

A reader / writer that communicates data with tags,
A carrier generation unit for generating a carrier signal;
An antenna for transmitting a carrier signal to the tag and receiving a subcarrier signal from the tag;
A frequency setting unit that is provided between the carrier generation unit and the antenna and sets a frequency of a carrier signal generated by the carrier generation unit;
A control unit for controlling the frequency setting unit;
A demodulation circuit for demodulating a subcarrier signal received by the antenna,
The demodulation circuit includes:
A detector that inputs a carrier signal transmitted from the antenna and a subcarrier signal received by the antenna as a received signal, and outputs an analog signal corresponding to an envelope of the received signal;
A converter that inputs an analog signal from the detector and outputs a digital signal corresponding to the analog signal;
When the control unit transmits a carrier signal for power charging from the antenna to the tag, the frequency setting unit divides the frequency of the carrier signal into a plurality of stages and increases the frequency step by step. Reader writer that gradually increases to the frequency of.