JP7164227B2 - Low power radio frequency identification method and apparatus - Google Patents

Description

The present invention relates to the field of radio frequency identification (RFID), and more particularly to a method for radio frequency identification with low power consumption and a device thereof.

Radio Frequency Identification (RFID) is a type of wireless communication technology that uses radio signals to identify a specific target and read/write associated data, creating a mechanical interface between the identification system and the specific target. or no need to establish optical contact. A radio signal is an electromagnetic field tuned to radio frequencies that uploads and transmits data from a tag attached to an item to automatically identify and track said item. Some tags do not require batteries because they obtain their energy from the electromagnetic field emanating from the identification device during identification. There is also a tag body that has a power supply and actively emits radio waves. Tags contain electronically stored information and are identifiable within a few meters. Unlike barcodes, radio frequency tags do not have to be located within the viewing angle of the identification device and may be embedded within the object being tracked.

The applications of radio frequency identification are extremely widespread and many industries operate radio frequency identification technology. For example, radio frequency tags are attached to vehicles in production so that manufacturers can track their progress on the production line, track the location of chemicals in warehouses, attach radio frequency tags to livestock and pets, Active identification of livestock and pets (preventing multiple livestock from using the same ID), employees using radio frequency identification ID identification cards to enter locked areas of buildings, vehicle radios For example, frequency transponders are used to collect tolls for toll roads and parking lots.

However, in these applications mentioned above, the devices that read the radio frequency identification all belong to the devices that connect to the fixed power supply (commercial power supply), and there is no need to consider the power consumption relatively. FIG. 1 is an operating waveform diagram showing a conventional radio frequency identification method. As shown in FIG. 1, this example takes the commonly used radio frequency identification tag EM4100/4200 as an example. The communication protocol is shown in Table 1 below.

It has 9 header bits and 32 data bits. The EM4100/4200 has a Bit Period of 512 us, which requires 32 ms to completely decode 64 data bits and 4.6 ms to completely decode 9 header bits. However, the actual detection time required is longer than the above numerical value. If the start time Toff is 100 ms and the power consumption is 5 mA, the start time Ton is 32 ms, the power consumption is 45 mA, and the average power consumption is (100*5+36.6*45)/136.6≈15. 7 mA is obtained.

However, when applying radio frequency identification technology to devices with batteries, such power consumption was unacceptable. For the above technique, the start time Toff can be extended by reducing power consumption, but there is a side effect of slowing down the reaction speed.

Therefore, the inventor of the present invention thought that the above-mentioned drawbacks could be improved, and as a result of earnest studies, the present inventors came up with the proposal of the present invention that effectively solves the above-mentioned problems with a rational design.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radio frequency identification method and apparatus with low power consumption. In other words, it reduces the amount of power consumption and allows the device to keep working for a long time in situations where the power source is limited.

To solve the above problems, a low power consumption radio frequency identification method according to one aspect of the present invention is applied to a radio frequency identification tag reader,
step A of proceeding to a normal sleep mode;
Step B of executing a wake-up sequence at each predetermined time and transmitting a probe signal from the coil;
Step C of detecting whether the energy magnitude of the coil is less than a threshold;
D, returning to step A if the energy magnitude of the coil exceeds the threshold.

Also, in the low power radio frequency identification method according to the present invention, before returning to step A if the energy magnitude of the coil exceeds the threshold, providing a correction threshold based on a background value; and executing a threshold correction sequence that substitutes the threshold with the correction threshold.

Further, in the low power consumption radio frequency identification method according to the present invention, when the energy magnitude of the coil is less than the threshold, continuously transmitting a carrier wave signal; and decoding the return data.

In the low power consumption radio frequency identification method according to the present invention, after decoding the return data, the step of determining whether or not the radio frequency identification code has been obtained; providing a corrected threshold value based on the background value; and substituting the corrected threshold value for the threshold value.

Yet another aspect of the invention is a low power radio frequency identification device. This device
an LC resonant circuit including a coil;
a wakeup circuit connected to the LC resonant circuit;
the low power consumption radio frequency identification device operates in a normal sleep mode;
executing a wake-up sequence at each predetermined time and transmitting a probe signal from the coil;
The wake-up circuit detects whether the energy magnitude of the coil is less than a threshold, and returns to the normal sleep mode if the energy magnitude of the coil exceeds the threshold.

Also, in the low power consumption radio frequency identification device according to the present invention, the wake-up circuit comprises a peak detector, a filter circuit and a comparison circuit. A peak detector is used to detect the voltage peak value of the coil and outputs a peak signal. A filter circuit, coupled to the peak detector, receives the peak signal, performs a low pass filter, and outputs a filtered signal. a comparison circuit includes a first input terminal for receiving the filter signal and a second input terminal for receiving a threshold signal; if the comparison signal output by the comparison circuit is in the first state for longer than the threshold time, the low consumption Controlling the power radio frequency identification device back to the normal sleep mode and executing a correction sequence to adjust the threshold signal based on background values.

Further, in the low power consumption radio frequency identification device according to the present invention, when the comparison signal output from the comparison circuit is in the first state for a time shorter than the threshold time, the low power consumption radio frequency identification device detects the carrier signal. It controls continuous transmission, receives return data returned by the tag, and decodes the return data.

Also, in the low power consumption radio frequency identification device according to the present invention, the wake-up circuit further comprises a digital-to-analog conversion circuit for outputting the threshold signal. The threshold signal is adjusted by adjusting the digital threshold input by the digital-to-analog conversion circuit when the low power radio frequency identification device executes the correction sequence.

The spirit of the present invention is to use the normal sleep mode, transmit a carrier wave signal (detection signal) for a short period of time, and detect the energy level of the coil to determine whether there is a radio frequency tag in the coil, This reduces the power consumption of the radio frequency identification reader. Thus, the present invention is applicable to devices using batteries.

Other features of the present invention will become apparent from the description of the specification and accompanying drawings.

1 is an operation waveform diagram showing a conventional radio frequency identification method; FIG. 1 is a circuit block diagram showing a low power consumption radio frequency identification device according to a preferred embodiment of the present invention; FIG. 1 is a flow chart illustrating a low power radio frequency identification method according to a preferred embodiment of the present invention; 1 is a flow chart illustrating a low power radio frequency identification method according to a preferred embodiment of the present invention; Fig. 3 is a flow chart showing the sub-steps of step 305 of the low power radio frequency identification method according to a preferred embodiment of the present invention; Fig. 3 is a circuit diagram showing a wake-up circuit 202 of a low power radio frequency identification device according to a preferred embodiment of the present invention; FIG. 4 is an operating waveform diagram of the low power consumption radio frequency identification device without radio frequency tag according to the preferred embodiment of the present invention; FIG. 4 is an operating waveform diagram with a radio frequency tag in the low power consumption radio frequency identification device according to the preferred embodiment of the present invention; FIG. 4 is an operating waveform diagram of the low power consumption radio frequency identification device without radio frequency tag according to the preferred embodiment of the present invention; FIG. 4 is an operating waveform diagram with a radio frequency tag in the low power consumption radio frequency identification device according to the preferred embodiment of the present invention; Fig. 3 is a circuit diagram showing a wake-up circuit 202 of a low power radio frequency identification device according to a preferred embodiment of the present invention;

Preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments described below do not limit the content of the present invention described in the claims. Moreover, not all the configurations described below are essential requirements of the present invention.

FIG. 2 is a circuit block diagram showing a low power consumption radio frequency identification device according to a preferred embodiment of the present invention. Referring to FIG. 2, the low power consumption radio frequency identification device comprises a control circuit 200 , an LC resonant circuit 201 and a wakeup circuit 202 . The LC resonant circuit 201 includes a switch circuit 203, a coil L1, and a capacitance C1. A wakeup circuit 202 is connected to the LC resonant circuit. For purposes of explanation, the present invention takes a battery-powered radio frequency tag reader as an example. In order to save power, this radio frequency tag reader normally operates in normal sleep mode. Execute the wakeup sequence once at each predetermined time, such as 100 ms.

When the radio frequency tag reader wakes up, the control circuit 200 controls the LC resonant circuit 201 to transmit a probe signal PB from the coil L1. This detection signal PB is a very short carrier wave signal such as 250us. Also, the wake-up circuit 202 detects whether the magnitude of the energy of the coil L1 (generally determined by the envelope of the coil signal, but the present invention is not limited to this) is less than a threshold. . The threshold is mainly used to determine whether there is a radio frequency tag on coil L1. When there is a radio frequency tag in the coil L1, the radio frequency tag consumes the energy of the detection signal PB transmitted by the coil L1. Therefore, when the detection signal PB is lower than the above threshold, it is determined that the coil L1 has a radio frequency tag. If the magnitude of the energy on coil L1 (envelope of coil L1) exceeds a threshold, determine that coil L1 does not have a radio frequency tag. At this time, the control circuit 200 controls the low power radio frequency identification device according to the embodiment of the present invention to return to the normal sleep mode. In the above embodiment, since the probe signal PB is only 250 us, the power consumption is reduced to about 1/1 in the condition of transmitting the signal once every 100 ms compared to the conventional method of continuously providing the magnetic field. Decrease to 400. If the resonant current is 45mA, it is reduced to 5.1125mA compared to the prior art. This value corresponds approximately to the standby current. Power consumption is only increased by about 100uA/s compared to the situation of waiting for the whole time.

FIG. 3 is a flowchart illustrating a low power radio frequency identification method according to a preferred embodiment of the present invention. As shown in FIG. 3, in this embodiment, the low power radio frequency identification method includes the following steps.
Step S301: Start.
Step S302: Proceed to normal sleep mode.
Step S303: Perform a wake-up sequence at each predetermined time, and transmit a probe signal from the coil.
Step S304: Detect whether the energy magnitude of the coil is less than the threshold. If the energy magnitude of the coil exceeds the threshold, return to step 302 to continue the normal sleep mode. If the energy magnitude of the coil is less than the threshold, it indicates that the tag of the coil has consumed the energy of the above detection signal, and go to step S305.
Step S305: Execute a decoding sequence.

FIG. 4 is a flowchart illustrating a low power radio frequency identification method according to a preferred embodiment of the present invention. 3 and 4, the embodiment of FIG. 4 additionally adds step S401 of providing a correction threshold based on a background value and performing a threshold correction sequence of substituting the threshold with the correction threshold. ing. If a user inadvertently places a conductor or other object near the coil, the energy in the detected signal will be absorbed, increasing the probability of false positives from the low power radio frequency identification device. In order to reduce the probability of misjudgment, in this embodiment, the threshold is corrected further based on the background value to avoid the occurrence of misjudgment.

FIG. 5 is a flow chart showing the sub-steps of step 305 of the low power radio frequency identification method according to the preferred embodiment of the present invention. Referring to FIG. 5, the substeps of step S305 are shown below.
Step S501: Continuously transmit a carrier signal. If it determines that there is a tag in the coil, it will continuously transmit a carrier signal to energize the tag and wait for return data from the tag.
Step S502: Receive reply data returned by the tag.
Step S503: Decrypt the above reply data.
Step S504: Determine whether the radio frequency identification code has been obtained. If it is determined to be negative, it indicates that there was an erroneous determination in step S304, and there is a possibility that there is a problem with the threshold value, and correction is required, and the process proceeds to step S505. If it is determined that it has been acquired, the process proceeds to step S506.
Step S505; if determined no, perform a threshold correction sequence to provide a corrected threshold according to the background value, and replace the threshold with the corrected threshold. After that, the process returns to step S302 to continuously enter the sleep power saving mode. After the threshold is modified, erroneous judgments will not occur easily, wake-up will not be performed, and further power saving effect will be achieved.
Step S506: If it is determined that it has been acquired, the tag executes a wakeup and performs a corresponding operation.

FIG. 6 is a circuit diagram showing wake-up circuit 202 of a low power radio frequency identification device according to a preferred embodiment of the present invention. Referring to FIG. 6, this wakeup circuit 202 comprises a peak detector 601, a filter circuit 602 and a comparison circuit 603. FIG. A peak detector 601, in this embodiment implemented with a diode, a resistor and a capacitance, is used to detect the voltage peak value of coil L1 and outputs a peak signal VP. Filter circuit 602, implemented in this embodiment with electrical resistance and capacitance, is connected to peak detector 601, receives peak signal VP, performs a low-pass filter, and outputs filtered signal VF. Comparator circuit 603 includes a first input for receiving filter signal VF and a second input for receiving threshold signal (reference voltage in this embodiment) Vref, and the output of the comparator circuit outputs a comparison signal CP.

FIG. 7A is an operation waveform diagram without a radio frequency tag in the low power consumption radio frequency identification device according to the preferred embodiment of the present invention. FIG. 7B is an operation waveform diagram with a radio frequency tag in the low power consumption radio frequency identification device according to the preferred embodiment of the present invention. 7A and 7B, PB denotes a probe signal and VF denotes a filter signal. It can be seen that the filtered signal VF is hardly attenuated in the absence of a radio frequency identification tag, whereas the filtered signal VF is greatly attenuated in the presence of a radio frequency identification tag.

FIG. 8A is an operating waveform diagram of the low power consumption radio frequency identification device without radio frequency tag according to the preferred embodiment of the present invention. FIG. 8B is an operation waveform diagram with a radio frequency tag in the low power consumption radio frequency identification device according to the preferred embodiment of the present invention. Referring to FIGS. 8A and 8B, as described above, the filter signal VF is hardly attenuated in the absence of the radio frequency identification tag, so that the filter signal VF remains higher than the reference voltage Vref for a long period of time. Signal CP is maintained in positive saturation for a long time. In the absence of a radio frequency identification tag, the filtered signal VF is greatly attenuated, so that the filtered signal VF remains greater than the reference voltage Vref for only a short period of time, and the comparison signal CP remains in positive saturation for a short period of time. The control circuit 200 determines whether or not the coil L1 has a tag according to the length of time that the comparison signal CP is maintained in the positive saturation state.

FIG. 9 is a circuit diagram showing wake-up circuit 202 of a low power radio frequency identification device according to a preferred embodiment of the present invention. 6 and 9, the difference between the two circuits is that the wakeup circuit 202 additionally includes a digital-analog converter 901 . In this embodiment, when the low power radio frequency identification device performs the correction sequence described above based on the background value, this reference voltage outputs the internal digital threshold to the digital-to-analog converter 901 described above, A digital-to-analog converter 901 converts the digital threshold to an analog reference voltage Vref, thereby representing the threshold signal.

In summary, the spirit of the present invention is to use the normal sleep mode, transmit a carrier wave signal (detection signal) for a short time, and detect the energy magnitude of the coil, so that the coil has a radio frequency tag. Determining whether or not the radio frequency identification reader consumes less power, making the invention applicable to battery powered devices. Also, in the preferred embodiment, a scheme that continuously modifies the threshold value based on the background value makes the radio frequency tag reader's decision more accurate.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit and interpret the present invention. It goes without saying that the present invention can be modified and improved without departing from its spirit, and that equivalents thereof are included in the present invention.

200 control circuit 201 LC resonant circuit 202 wake-up circuit 203 switch circuit L1 coil C1 capacitance PB detection signal S301 step S302 of the low power radio frequency identification method according to the preferred embodiment of the present invention; Step S303 of the power radio frequency identification method Step S304 of the low power radio frequency identification method according to the preferred embodiment of the present invention Step S305 of the low power radio frequency identification method according to the preferred embodiment of the present invention Step S401 of the low power radio frequency identification method Performing a threshold correction sequence S501 Sub-step S502 of step 305 of the low power radio frequency identification method according to the preferred embodiment of the present invention Low power radio according to the preferred embodiment of the present invention Sub-step S503 of step 305 of the frequency identification method Sub-step S504 of step 305 of the low power consumption radio frequency identification method according to a preferred embodiment of the present invention Step 305 of the low power consumption radio frequency identification method according to a preferred embodiment of the present invention sub-step S505 of step 305 of the low power consumption radio frequency identification method according to the preferred embodiment of the present invention sub-step S506 of step 305 of the low power consumption radio frequency identification method according to the preferred embodiment of the present invention sub-step 601 peak detection device 602 filter circuit 603 comparison circuit VP peak signal VF filter signal CP comparison signal Vref threshold signal (reference voltage)
901 Digital-to-Analog Converter

Claims (5)

A low-power radio frequency identification method applied to a radio frequency identification tag reader, comprising:
step A of proceeding to a normal sleep mode;
Step B of executing a wake-up sequence at each predetermined time and transmitting a probe signal from the coil;
Step C of detecting whether the energy magnitude of the coil is less than a threshold;
D, returning to step A if the energy magnitude of the coil exceeds the threshold ;
If the energy magnitude of the coil is less than the threshold,
continuously transmitting a carrier signal;
receiving reply data sent back by the tag;
and decoding the return data;
After decrypting the reply data,
determining whether a radio frequency identification code has been obtained;
if not, performing a threshold correction sequence, providing a corrected threshold based on a background value, and substituting the corrected threshold for the threshold . Radio frequency identification method. Performing a threshold correction sequence that provides a correction threshold based on a background value and substitutes the threshold with the correction threshold before returning to step A if the energy magnitude of the coil exceeds the threshold. The low power consumption radio frequency identification method of claim 1, further comprising the steps of: an LC resonant circuit including a coil;
a wakeup circuit connected to the LC resonant circuit;
The low-power radio frequency identification device operates in a normal sleep mode,
executing a wake-up sequence at each predetermined time and transmitting a probe signal from the coil;
the wake-up circuit detects whether the energy magnitude of the coil is less than a threshold;
if the energy magnitude of the coil exceeds the threshold, return to the normal sleep mode;
If the time during which the comparison signal of the comparison circuit output is in the first state is shorter than the threshold time,
controlling the low-power radio frequency identification device to continuously transmit a carrier signal;
Receive the reply data sent by the tag,
A low power radio frequency identification device, characterized in that it decodes the return data . The wakeup circuit is
A peak detector that is used to detect the voltage peak value of the coil and outputs a peak signal;
a filter circuit connected to the peak detector for receiving the peak signal, performing a low pass filter, and outputting a filtered signal;
a comparison circuit including a first input for receiving the filtered signal and a second input for receiving a threshold signal;
controlling the low power radio frequency identification device to return to the normal sleep mode if the comparison signal output by the comparison circuit is in the first state for longer than a threshold time; 4. A low power radio frequency identification device according to claim 3 , characterized in that it performs a correction sequence to adjust the threshold signal. The wakeup circuit is
further comprising a digital-to-analog conversion circuit for outputting the threshold signal;
The digital-to-analog conversion circuit adjusts an input digital threshold such that the threshold signal adjusts when the low power radio frequency identification device executes the correction sequence. 5. The low power consumption radio frequency identification device of claim 4 .

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