JP4605076B2 - RF device and RF data transmission method - Google Patents

Description

  The present invention relates to an RF device that performs non-contact data transmission by transmitting and receiving radio frequency signals and an RF data transmission method using the same.

  Conventionally, in RFID (Radio Frequency Identification), data transmission is performed between radio interrogators (interrogators (readers, base stations, etc.)) and responders (cards, tags, labels, sensor units, etc.).

  In the conventional general RFID, the operation mode on the wireless tag side includes a transmission mode, a reception mode, and an activation signal (wake-up signal) reception mode. When the radio tag does not receive a radio frequency signal for a certain period of time, it enters an activation signal reception mode and waits for the activation signal. After receiving this activation signal, it waits in the reception mode for a certain period of time. If there is any command from the reader or the like in this reception mode, the wireless tag enters the transmission mode and transmits a predetermined response signal.

In particular, in an RFID using a wireless tag that does not incorporate a battery in the wireless tag, the wireless tag uses a carrier wave transmitted from a reader or the like as a direct current power by a rectifier circuit and serves as an operating power source for the internal circuit. (See Patent Document 1)
Here, a circuit configuration of a semiconductor chip built in the wireless tag disclosed in Patent Document 1 will be described with reference to FIG.

  FIG. 1 is a circuit block diagram of a semiconductor chip built in the tag 7. The tag receiving antenna coil 8 receives the first and second reader carrier waves transmitted from the reader. The rectifier circuit 9 rectifies a signal obtained from the tag receiving antenna coil, and supplies DC power to all circuit units including a nonvolatile memory built in the tag. The filter 10 is a high-pass filter for taking out the second reader carrier wave from the signal obtained from the tag receiving antenna coil 8. The amplification / shaping circuit 11 amplifies and shapes the output signal of the filter 10. The first frequency dividing circuit 12 receives the output signal of the amplification / shaping circuit 11, divides the frequency, and creates a tag carrier wave 17 from the second reader carrier wave. The second frequency dividing circuit 13 receives the output signal of the first frequency dividing circuit and generates a memory read clock 16. The nonvolatile memory 14 is realized by EPROM, EEPROM or the like, and an identification code recorded in advance is read by a memory read clock obtained from the second frequency dividing circuit 13. The modulation circuit 15 is configured by, for example, an exclusive OR circuit, etc., and phase-modulates the tag carrier wave 17 generated by the first frequency divider circuit 12 with a nonvolatile memory read signal. The tag transmission antenna coil 18 transmits the output signal of the modulation circuit 15 to the reader.

In this way, two carrier waves having different frequencies are received, one of the carrier waves is used for creating a DC power source of the semiconductor circuit, and the other carrier wave is used for reading the semiconductor nonvolatile memory. .
JP-A-7-155431

  In the conventional RFID, since it is necessary to activate the control circuit in the reception mode when waiting for a signal within a certain period of time, battery consumption is large. In addition, an activation signal receiving circuit including an antenna is required. For example, in a keyless entry system of an automobile, an LF band signal of 125 kHz is used for a start signal. However, the reception antenna for the LF band signal is large in itself, which is a problem of downsizing the module.

  Further, in the configuration of Patent Document 1, if the distance between the transmission antenna and the reception antenna is close within the wireless tag, the signal transmitted by the user may be received by itself, and the signal processing circuit may be saturated and may not operate normally. There is. Furthermore, if the reception antenna also serves as a transmission, a transmission signal flows to the power supply circuit side, and a problem arises that necessary transmission power cannot be obtained.

  In addition, if two different frequencies are used for the wireless signal used for the power supply of the wireless tag and the wireless signal for exchanging data between the wireless tag and the reader, a filter is required to separate the two frequency signals. Thus, there is a problem that the wireless tag becomes structurally large and costs increase.

  In addition, antenna coils for the transmitting antenna and the receiving antenna are required, which is a factor that hinders downsizing.

  In addition, in a data transmission system that transmits and receives radio frequency signals such as RFID using a wireless tag that does not have a built-in battery, the reader supplies power so that data can be transmitted to and from the wireless tag when the wireless tag is close to a predetermined distance. However, since the carrier wave is always transmitted even during standby when data transmission is not performed, there is a problem in terms of reducing power consumption.

  The above-mentioned problems are not limited to RFID in a narrow sense, but generally occur in RF devices and RF data transmission methods that transmit and receive data using radio frequency signals without contact.

  Accordingly, an object of the present invention is to provide an RF device that can solve the above-described problems and can be reduced in size and power consumption as a whole, and an RF data transmission method using the same.

An RF device according to the present invention performs non-contact data transmission by transmitting and receiving radio frequency signals (radio waves), and includes an antenna that receives a high-frequency signal and a power distribution circuit that distributes power of the high-frequency signal received by the antenna. And a control circuit for processing one high frequency signal distributed by the power distribution circuit as a received signal, and a battery, and rectifies the electromotive voltage of the battery and the other high frequency signal distributed by the power distribution circuit. And a power supply circuit that outputs an addition voltage of the converted DC power supply voltage as a power supply voltage for the control circuit, and the control circuit does not operate with the electromotive voltage of the battery but operates with the addition voltage. It is a feature.

  The high-frequency signal is a digital modulation signal in which, for example, a frequency modulation (FSK) signal, a phase modulation (PSK, QPSK) signal, or an amplitude modulation (QAM) signal is intermittently generated on the time axis.

  The power distribution circuit is, for example, a Wilkinson distribution circuit.

  Further, for example, the power supply circuit includes a battery, and outputs a sum voltage of a DC power supply voltage converted by rectification of the high-frequency signal and an electromotive voltage of the battery as a power supply voltage for the control circuit. It does not operate with the electromotive voltage of the battery, but operates with the added voltage.

The RF data transmission method according to the present invention performs non-contact data transmission by radio signal between an RF device having data to be transmitted and a reader, and the reader modulates a frequency modulation (FSK) signal and a phase modulation ( PSK, QPSK) signal or amplitude modulation (QAM) signal is intermittently generated on the time axis, and a radio signal is transmitted by the RF device in a section existing on the time axis of the radio signal. A signal is converted into electric power to generate a DC power supply voltage, and the radio signal is received using an addition voltage of an electromotive voltage of a battery included in the RF device and a DC power supply voltage converted from the radio signal as a power supply voltage. And a control circuit that transmits the data is activated, and the control circuit does not operate with the electromotive voltage of the battery but operates with the added voltage. Is characterized in that the the to.

  (1) Since a high frequency signal received by an antenna is distributed, one of the high frequency signals is processed as a reception signal, and the other high frequency signal is rectified and converted into a DC power supply voltage. Therefore, a small and low-cost RF device can be configured.

  (2) By making the high frequency signal a frequency modulation signal such as FSK, a phase modulation signal such as PSK, QPSK, or an amplitude modulation signal such as QAM, a digital modulation signal that is generated intermittently on the time axis. Since the processing as the received signal is performed only when a carrier wave exists, when the control circuit is operated by a battery built in the RF device, the overall power consumption can be reduced and the battery life can be extended. Also, the apparatus on the side of transmitting the radio frequency signal, such as a reader, transmits the radio frequency signal only when transmitting the inquiry command to the RF device, so that the power consumption can be reduced.

  (3) By using a Wilkinson distribution circuit as the power distribution circuit, when a response signal is returned from the control circuit processed as a reception signal (whether active transmission or passive transmission), the transmission signal Does not wrap around (does not return) to the power supply circuit side), the reception side and the transmission side can be operated independently, and the necessary transmission power can be obtained without loss. In addition, a switch circuit for switching between transmission and reception is not necessary.

  (4) A battery is provided in the power supply circuit, and an addition voltage of the DC power supply voltage converted by the rectification of the high-frequency signal and the electromotive voltage of the battery is output as the power supply voltage for the control circuit. It does not operate with voltage, but operates with the added voltage, so there is no need to activate the control circuit in reception mode when waiting for a signal, and to suppress power consumption when a battery is built in Battery life can be extended.

<< First Embodiment >>
The RF device according to the first embodiment will be described with reference to FIGS.
FIG. 2 is a block diagram showing the configuration of the RF device according to the first embodiment. In FIG. 2, the RF device 100 and the reader 200 constitute an RF data transmission system. In the RF device 100, the antenna 21 transmits and receives a radio frequency signal to and from the antenna 31 of the reader 200 using a near electromagnetic field or a radiated electromagnetic field. The signal transmission / reception circuit 22 outputs a reception signal from the antenna 21 to the power distribution circuit 23 and outputs a transmission signal from the transmission circuit 28 to the antenna 21.

  The power distribution circuit 23 distributes the received signal as two high-frequency signals, outputs one to the activation circuit 24, and outputs the other to the demodulation circuit 26. The startup circuit 24 rectifies the high-frequency signal output from the power distribution circuit 23 to generate a DC voltage, and outputs it to the power supply 25. The power supply 25 is, for example, a circuit including a battery, and supplies an addition voltage of the output voltage from the activation circuit 24 and the electromotive voltage of the battery to the control circuit 29 as a power supply voltage. The configuration of the activation circuit 24 will be described later.

  The control circuit 29 is a circuit using a C-MOS semiconductor chip and does not operate with the electromotive voltage of the battery and remains stopped. That is, there is almost no power consumption at this time. When the added voltage of the output voltage from the start circuit 24 and the electromotive voltage of the battery reaches the voltage required for starting the control circuit 29, the control circuit starts its operation.

  The demodulation circuit 26 receives the high frequency signal from the power distribution circuit 23 as a received signal and converts it into a digital data string. The receiving circuit 27 inputs the digital data string and performs a predetermined process. For example, a predetermined inquiry command from the reader 200 is decoded, and the transmission circuit 28 is activated to respond to the command. Thereby, the transmission circuit 28 transmits a preset identification code or the like.

  FIG. 3 is a circuit diagram showing a configuration example of the starting circuit 24. This circuit is a circuit in which a battery is added to a so-called one-stage Cockcroft-Walton circuit. With such a configuration, an addition voltage of the output voltage from the power distribution circuit 23 and the electromotive voltage of the battery is output from the activation circuit 24.

FIG. 4 is a waveform diagram of each part of FIG. The input signal (a) is an input signal received by the antenna 21 in FIG. In this example, it is an FSK signal, and there are a section in which a carrier wave exists and a section in which no carrier wave exists. When a carrier wave is present, the power supply voltage applied to the control circuit 29 exceeds the voltage required for the operation of the control circuit 29. Therefore, as shown in (b), the control circuit 29 operates only during the period in which the carrier wave exists.
As shown in (c), the demodulated signal demodulates the FSK signal, and the receiving circuit 27 reads digital data as shown in (d).

  In this example, the number of bits in one burst is deliberately reduced for the sake of explanation.

  FIG. 5 is a timing chart specifically showing the transmission timing and the reception timing. As already described, as shown in (a) and (b), the power supply of the RF device 100 is turned on during the period t0 to t5 in which the carrier wave of the radio frequency signal transmitted from the reader exists.

  Immediately after the power is turned on, the wireless tag waits to receive a question command from the reader. As shown in (c), after the power of the RF device is turned on, a question command is received from the reader during a period of t1-t2. If a question command is received, processing corresponding to that is performed, and predetermined data is transmitted during a period of t3-t4 as shown in (d). When the reader receives data from the RF device, the reader terminates the series of processes and terminates transmission at the timing t5 (cuts off the carrier wave).

According to the first embodiment, the following effects are obtained.
Since the high-frequency signal received by the antenna is power-distributed, one of the high-frequency signals is processed as a received signal, and the other high-frequency signal is rectified and converted into a DC power supply voltage. Only a small and low-cost RF device can be configured.

  In addition, since processing as a received signal is performed only when a carrier wave exists, overall power consumption can be reduced, and the life of the battery built in the RF device can be extended. Also, the apparatus on the side of transmitting the radio frequency signal, such as a reader, transmits the radio frequency signal only when transmitting the inquiry command to the RF device, so that the power consumption can be reduced.

  In the example shown in FIG. 4, data transmission / reception is performed by frequency modulation (FSK). However, phase modulation such as PSK and QPSK, and amplitude modulation such as QAM may be used. When amplitude modulation is used, the output voltage of the startup circuit 24 changes depending on the amplitude, but the circuit and usage conditions can be determined so that the control circuit 29 is started even when the data value is the lowest in QAM or the like. That's fine.

<< Second Embodiment >>
Next, an RF device according to a second embodiment will be described with reference to FIG.
In the second embodiment, portions corresponding to the signal transmission / reception circuit 22 and the power distribution circuit 23 shown in FIG. 2 are specifically shown. Further, the configuration of the control circuit is different from that shown in the first embodiment.

  In FIG. 6, the antenna 41 in the RF device 101 is coupled to the antenna 31 of the reader 200 in the near electromagnetic field or transmits and receives a radiated electromagnetic field. The filter 42 cuts off a frequency band other than the frequency band used in the RF data transmission system, and suppresses the influence of interference waves and spurious. The power distribution circuit 43 constitutes a Wilkinson distribution circuit by inductors L1 and L2, a resistor R, and capacitors C1, C2 and C0.

  The rectifier circuit / voltage amplifier circuit 44 rectifies and amplifies the voltage of one high-frequency signal distributed by the power distribution circuit 43. This rectifier circuit / voltage amplifier circuit 44 is a circuit corresponding to the starting circuit 24 in FIG. 2, and the voltage obtained by adding the voltage amplified voltage to the electromotive voltage of the battery included in the power supply circuit 45 exceeds a predetermined value. Voltage is amplified so that the control circuit 50 is activated when the

  The demodulation circuit 46 in the control circuit 50 demodulates the other high frequency signal distributed by the power distribution circuit 43. The reception circuit 47 decodes the inquiry command transmitted from the reader 200 from the demodulated signal, and activates the transmission circuit 48.

  The control circuit 50 includes a sensor 49. For example, when this RF data transmission system is used in a TPMS (Tire Pressure Monitoring System), the sensor 49 detects the pressure, temperature, and angular velocity of the automobile tire. When the transmission circuit 48 is activated by the reception circuit 47, the detection signal of the sensor 49 is converted into digital data and transmitted.

  According to the second embodiment, since the Wilkinson distribution circuit is used as the power distribution circuit 43, the transmission signal does not pass through the power distribution circuit 43 to the rectifier circuit / voltage amplification circuit 44 and the power supply circuit 45 side. Therefore, the reception side and the transmission side can be operated independently, and necessary transmission power can be obtained without loss. In addition, a switch circuit for switching between transmission and reception is not necessary.

<< Third Embodiment >>
Next, an RF device according to a third embodiment will be described with reference to FIG.
FIG. 7 is a block diagram showing the configuration of the RF device according to the third embodiment. The difference from the RF device shown in FIG. 2 is that no battery is built in the RF device 102 side. That is, the power conversion circuit 33 directly generates and gives a power supply voltage to the control circuit 29 by rectifying and smoothing one high-frequency signal distributed by the power distribution circuit 23.

  When the power conversion circuit 33 includes a charging circuit using a capacitor, for example, the carrier of the radio frequency signal transmitted from the reader 200 is charged as power, and the power is used at the time of transmission. In the case where a charging circuit using a capacitor or the like is not provided, a non-modulated carrier wave of a radio frequency signal from the reader 200 is received and transmitted using a so-called mirror subcarrier system that modulates a load viewed from the antenna 31 of the reader 200. That is, the transmission circuit 28 performs data transmission by changing the amount of reflection and the phase from the antenna 21 by switching the termination / open state of the antenna 21.

  In any of the first to third embodiments described above, when the RF device actively transmits to the reader, transmission and reception are performed using the same frequency band between the reader and the RF device. Data transmission may be performed by dividing the band of the transmission signal and the band of the reception signal within the frequency band. In this case, for example, the signal transmission / reception circuit 22 shown in FIGS. 2 and 7 is configured by a duplexer.

  When transmission / reception is performed between the reader and the RF device using the same frequency band, a transmission / reception change-over switch may be used as the signal transmission / reception circuit 22 to perform transmission and reception in a time division manner.

10 is a block diagram of a semiconductor chip disclosed in Patent Document 1. FIG. It is a block diagram which shows the structure of RF device which concerns on 1st Embodiment. FIG. 3 is a block diagram illustrating a configuration example of a startup circuit in FIG. 2. It is a wave form diagram which shows the relationship of modulation / demodulation of a radio frequency signal. It is a timing chart which shows the example of transmission / reception timing. It is a block diagram which shows the structure of RF device which concerns on 2nd Embodiment. It is a block diagram which shows the structure of RF device which concerns on 3rd Embodiment.

Explanation of symbols

21, 31, 41-antenna 29, 50-control circuit 30-reader side transmission / reception circuit 43-power distribution circuit 100-102-RF device 200-reader

Claims (4)

An RF device that performs non-contact data transmission by transmitting and receiving radio frequency signals,
An antenna for receiving high-frequency signals;
A power distribution circuit that distributes power of a high-frequency signal received by the antenna;
A control circuit for processing, as a received signal, one high-frequency signal that is power-distributed by the power distribution circuit;
A power supply circuit comprising a battery, and outputting a sum voltage of the electromotive voltage of the battery and a DC power supply voltage obtained by rectifying and converting the other high-frequency signal distributed by the power distribution circuit as a power supply voltage for the control circuit; ,
Equipped with a,
The RF device is characterized in that the control circuit does not operate with the electromotive voltage of the battery but operates with the added voltage .   The RF device according to claim 1, wherein the high-frequency signal is a digital modulation signal in which a frequency modulation signal, a phase modulation signal, or an amplitude modulation signal is intermittently generated on a time axis.   The RF device according to claim 1, wherein the power distribution circuit is a Wilkinson distribution circuit. In an RF data transmission method for performing non-contact data transmission with a wireless signal between an RF device having data to be transmitted and a reader,
By the reader, a radio signal in which a frequency modulation signal, a phase modulation signal or an amplitude modulation signal is intermittently generated on the time axis is transmitted,
From the RF device, the radio signal is converted into electric power in a section existing on the time axis of the radio signal to generate a DC power supply voltage, and an electromotive voltage of a battery included in the RF device and the radio signal The control circuit that activates the control circuit that transmits the data while receiving the wireless signal using the addition voltage with the DC power supply voltage by the conversion of the power supply voltage, and does not operate the control circuit with the electromotive voltage of the battery, An RF data transmission method characterized by operating with an addition voltage .

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