TWI764106B - Method for radio frequency identification with low power consumption and device thereof - Google Patents

Abstract

A method for radio frequency identification with low power consumption and a device thereof are provided in the present invention. The method for radio frequency identification with low power consumption is adapted for a radio frequency tag reader, the method includes: the step A, entering a constant sleep mode; the step B, performing a wake-up sequence every preset period, and sending a probe signal from a coil; the step C, detecting whether the energy of the signal on the coil is smaller than a threshold; and the step D, coming back to the step A if the energy of the signal on the coil is greater than the threshold.

Description

Low power consumption radio frequency identification method and device

The present invention relates to a radio frequency identification (RFID) technology, and further, the present invention relates to a low power consumption radio frequency identification method and device.

Radio Frequency Identification (RFID) is a wireless communication technology that can identify specific targets and read and write related data through radio signals without the need to establish mechanical or optical contact between the identification system and the specific target. The radio signal transmits the data from the tag attached to the item through the electromagnetic field tuned to the radio frequency to automatically identify and track the item. Some tags can get energy from the electromagnetic field emitted by the identifier when they are identified, and do not need batteries; there are also tags themselves that have power and can actively emit radio waves. The tags contain electronically stored information and are identifiable within a few meters. Unlike barcodes, RFID tags do not need to be within the line of sight of the identifier and can also be embedded within the object being tracked.

Radio frequency identification is extremely versatile, and many industries use radio frequency frequency identification technology. By attaching RFID tags to a car in production, the factory can easily track the progress of the car on the production line. Warehouses can track the location of medicines. Radio frequency tags can also be attached to livestock and pets to facilitate positive identification of livestock and pets (to prevent several livestock from using the same identity). Radio-frequency identification cards allow employees to gain access to locked parts of buildings, and radio-frequency transponders in cars can also be used to collect toll roads and car parks.

However, in the above-mentioned applications, the devices for reading RFID are all devices coupled to a fixed power supply (mains power), relatively speaking, it is relatively unnecessary to consider the part of power consumption. FIG. 1 is an operation waveform diagram of a radio frequency identification device of the prior art. Please refer to Figure 1. In this example, a commonly used RFID tag, such as EM4100/4200, is used as an example. Its communication protocol is described in Table 1 below:

It has 9 header bits and 32 data bits. The bit period (Bit Period) of EM4100/4200 is 512us, and it takes 32ms to completely decode 64bits of data bits. It takes 4.6ms to fully decode 9 header bits, and the actual detection time needs to be longer than the above number The words are going to be long. Assuming that the off time Toff is 100ms and the power consumption is 5mA, the on time Ton is 32ms and the power consumption is 45mA, it can be known that the average current consumption is (100*5+36.6*45)/136.6≒15.7mA.

However, if the RFID technology is to be applied to a device with a battery, such power consumption is unacceptable. For the above technology, if the power consumption needs to be reduced, the off time Toff can be increased, but the side effect is that the response speed will be reduced.

An object of the present invention is to provide a low-power consumption radio frequency identification method and device, which can reduce power consumption and enable the device to maintain operation for a long time under the condition of limited power supply.

In view of this, the present invention provides a low power consumption radio frequency identification method suitable for a radio frequency identification tag reading device. The low power consumption radio frequency identification method includes: step A: entering a normal sleep mode; step B: each preset time, perform a wake-up procedure, and send a probe signal (Probe Signal) from a coil; Step C: detect whether the magnitude of the energy on the coil is less than a threshold value; and Step D: when the magnitude of the energy on the coil is greater than the Threshold value, go back to step A.

According to the low power consumption radio frequency identification method according to the preferred embodiment of the present invention, when the magnitude of the energy on the coil is greater than the threshold value, before returning to step A, the method further includes: performing a threshold value correction procedure, according to the background value , a calibration threshold value is given, and the calibration threshold value is used to replace the threshold value.

Low power consumption radio frequency according to the preferred embodiment of the present invention The identification method, wherein, when the magnitude of the energy on the coil is smaller than the threshold value, further comprises: continuously sending a carrier signal; receiving a return data returned by a tag; and decoding the return data.

According to the low power consumption radio frequency identification method according to the preferred embodiment of the present invention, after decoding the returned data, the method further comprises: judging whether to obtain the radio frequency identification code; For the background value, a correction threshold value is given, and the threshold value is replaced by the correction threshold value.

The present invention further provides a low power consumption radio frequency identification device. The low power consumption radio frequency identification device includes an LC resonance circuit and a wake-up circuit. The LC resonant circuit includes a coil. A wake-up circuit is coupled to the LC resonance circuit. The low power consumption RFID device operates in a normal sleep mode, wherein a wake-up procedure is performed every preset time, and a probe signal (Probe Signal) is sent from the coil, wherein the wake-up circuit detects the amount of energy on the coil Whether it is less than a threshold value, when the magnitude of the energy on the coil is greater than the threshold value, return to the normal sleep mode.

According to the low power consumption radio frequency identification device according to the preferred embodiment of the present invention, the wake-up circuit includes a peak detector, a filter circuit and a comparison circuit. The peak detector is used to detect the voltage peak value of the coil and output a peak value signal. The filter circuit is coupled to the peak detector, receives the peak signal, performs a low-pass filter, and outputs a filtered signal. The comparison circuit includes a first input terminal and a second input terminal, wherein the first input terminal receives For the filtering signal, the second input terminal receives a threshold signal, wherein when the time of the comparison signal output by the comparison circuit in the first state is greater than a threshold time, the low power consumption RFID device is controlled to return to the normal sleep mode, A calibration procedure is performed to adjust the threshold signal according to the background value.

According to the low power consumption radio frequency identification device according to the preferred embodiment of the present invention, when the comparison signal output by the comparison circuit is in the first state for less than a threshold time, the low power consumption radio frequency identification device is controlled to continuously send a carrier signal ; receive a return data returned by a tag; and decode the return data.

According to the low power consumption radio frequency identification device according to the preferred embodiment of the present invention, the wake-up circuit further comprises: a digital-to-analog conversion circuit for outputting the threshold signal, wherein the low power consumption radio frequency identification device performs the calibration During the procedure, the digital threshold value input by the digital analog conversion circuit is adjusted, and the threshold signal has been adjusted.

The spirit of the present invention is to use the normal sleep mode and send a short-time carrier signal (detection signal), and detect the energy on the coil to determine whether there is a radio frequency tag on the coil, thereby reducing the power consumption of the radio frequency identification reading device , so the present invention can be applied to devices using batteries.

In order to make the above-mentioned and other objects, features and advantages of the present invention more clearly understood, preferred embodiments are hereinafter described in detail in conjunction with the accompanying drawings.

200: Control circuit

201: LC Resonant Circuit

202: Wake up circuit

203: switch circuit

L1: Coil

C1: Capacitor

PB: Probe Signal

S301~S305: each step of the low power consumption radio frequency identification method of a preferred embodiment of the present invention

S401: Perform a threshold value correction procedure

pregnancy

S501~S506: sub-steps of step 305 of the low power consumption radio frequency identification method of a preferred embodiment of the present invention

601: Peak Detector

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

FIG. 1 is an operation waveform diagram of a radio frequency identification device of the prior art.

FIG. 2 is a circuit block diagram of a low power consumption radio frequency identification device according to a preferred embodiment of the present invention.

FIG. 3 is a flowchart of a low power consumption radio frequency identification method according to a preferred embodiment of the present invention.

FIG. 4 is a flow chart of a low power consumption radio frequency identification method according to a preferred embodiment of the present invention.

FIG. 5 is a flow chart of sub-steps of step 305 of the low power consumption RFID method according to a preferred embodiment of the present invention.

FIG. 6 is a circuit diagram of the wake-up circuit 202 of the low power consumption RFID device according to a preferred embodiment of the present invention.

FIG. 7A is an operation waveform diagram of a low power consumption RFID device without an RFID tag according to a preferred embodiment of the present invention.

FIG. 7B is an operation waveform diagram of a low power consumption RFID device having an RFID tag according to a preferred embodiment of the present invention.

FIG. 8A is an operation waveform diagram of a low power consumption RFID device without an RFID tag according to a preferred embodiment of the present invention.

FIG. 8B shows a low power consumption radio frequency identification according to a preferred embodiment of the present invention. Operational waveforms of RFID tags on other devices.

FIG. 9 is a circuit diagram of the wake-up circuit 202 of the low power consumption RFID device according to a preferred embodiment of the present invention.

FIG. 2 is a circuit block diagram of a low power consumption radio frequency identification device according to a preferred embodiment of the present invention. Please refer to FIG. 2 , the low power consumption RFID device includes a control circuit 200 , an LC resonance circuit 201 and a wake-up circuit 202 . The LC resonance circuit 201 includes a switch circuit 203, a coil L1 and a capacitor C1. The wake-up circuit 202 is coupled to the LC resonance circuit. For convenience of description, the present invention takes a battery-driven radio frequency tag reading device as an example. In order to save power, the radio frequency tag reading device usually operates in a normal sleep mode. The wake-up procedure is performed only once every preset time period, such as 100ms.

When the RFID reading device is woken up, the control circuit 200 controls the LC resonant circuit 201 to send a probe signal (Probe Signal) PB from the coil L1. The probe signal PB is a very short carrier signal. For example, a 250us carrier signal. At the same time, the wake-up circuit 202 detects whether the magnitude of the energy on the coil L1 (generally, it can be determined by using the envelope envelope of the signal on the coil, but the invention is not limited to this) whether it is less than a threshold value. The main purpose of the threshold value is to judge whether the radio frequency tag is placed on the coil L1. When the radio frequency tag is placed on the coil L1, the radio frequency tag will consume the energy of the detection signal PB sent by the coil L1, so if the detection signal PB is lower than the above threshold value, it can be determined that an radio frequency tag is placed on the coil L1. When the magnitude of the energy on the coil L1 (the package of the coil L1) is greater than the threshold value, it is determined that no radio frequency tag is placed on the coil L1. At this time, the control The circuit 200 controls the low power consumption radio frequency identification device according to the embodiment of the present invention to return to the normal sleep mode. However, in the above-mentioned embodiment, since the probe signal (Probe Signal) PB is only 250us, compared with the traditional method of continuously providing the magnetic field, under the condition of sending a signal every 100ms, the power consumption can be reduced by about 1/400. Electricity, assuming a resonant current of 45mA, can be reduced to 5.1125mA compared to the prior art. This value is almost equivalent to the standby current. Compared with full-time standby, the power consumption increases by about 100uA/s.

FIG. 3 is a flowchart of a low power consumption radio frequency identification method according to a preferred embodiment of the present invention. Please refer to FIG. 3, in this embodiment, the low power consumption radio frequency identification method includes the following steps:

Step S301: Start.

Step S302: Enter a normal sleep mode.

Step S303 : at each preset time, a wake-up procedure is performed, and a probe signal (Probe Signal) is sent from a coil.

Step S304: Detect whether the magnitude of the energy on the coil is less than a threshold value. When the magnitude of the energy on the coil is greater than the threshold value, go back to step 302 to continue the normal sleep mode. When the magnitude of the energy on the coil is less than the threshold value, it means that there is a label on the coil that consumes the energy of the detection signal, and the process proceeds to step S305.

Step S305: Perform a decoding process.

FIG. 4 is a flow chart of a low power consumption radio frequency identification method according to a preferred embodiment of the present invention. Please refer to FIG. 3 and FIG. 4. Here, the embodiment of FIG. 4 additionally adds a step S401 : performing a threshold value calibration procedure, setting a calibration threshold value according to the background value, and replacing it with the calibration threshold value the threshold value. Because the user may accidentally place conductors or other Objects in the vicinity of the coil cause the energy of the detection signal to be absorbed, thereby increasing the probability of false positives for low-power consumption RFID devices. In order to reduce the probability of misjudgment, in this embodiment, the threshold value is also corrected according to the background value. Avoid misjudgment.

FIG. 5 is a flow chart of sub-steps of step 305 of the low power consumption RFID method according to a preferred embodiment of the present invention. Please refer to FIG. 5, the sub-steps of step S305 include:

Step S501: Continue to send a carrier signal. When it is determined that there is a tag on the coil, the carrier signal needs to be continuously sent to give energy to the tag, and wait for the tag to return data.

Step S502: Receive a return data returned by a tag.

Step S503: Decode the above returned data.

Step S504: Determine whether to obtain a radio frequency identification code. If the judgment is negative, it means that the judgment is wrong in step S304, the threshold value may have a problem and needs to be corrected, and then step S505 is performed. If it is determined to be yes, go to step S506.

Step S505 ; when the judgment is negative, perform a threshold value calibration procedure, set a calibration threshold value according to the background value, and replace the threshold value with the calibration threshold value. After that, go back to step S302, and continue to enter the sleep power saving mode. Since the threshold value is corrected, it is not easy to be awakened by misjudgment, which further achieves the effect of more power saving.

Step S506; when the judgment is yes, wake up and execute the action corresponding to the tag.

FIG. 6 is a circuit diagram of the wake-up circuit 202 of the low power consumption RFID device according to a preferred embodiment of the present invention. Please refer to FIG. 6 , the wake-up circuit 202 includes a peak detector 601 , a filter circuit 602 and a comparison circuit 603 . In this embodiment, the peak detector 601 is implemented by a diode, a resistor and a capacitor, and is used to detect the voltage peak value of the coil L1 and output a peak value signal VP. In this embodiment, the filter circuit 602 is implemented by a resistor and a capacitor, and the peak value is coupled The detector 601 receives the peak signal VP and performs a low-pass filter to output a filtered signal VF. The comparison circuit 603 includes a first input terminal and a second input terminal, wherein the first input terminal receives the filtering signal VF, the second input terminal receives a threshold signal (the reference voltage in this embodiment) Vref, and the output of the comparison circuit The terminal outputs the comparison signal CP.

FIG. 7A is an operation waveform diagram of a low power consumption RFID device without an RFID tag according to a preferred embodiment of the present invention. FIG. 7B is an operation waveform diagram of a low power consumption RFID device having an RFID tag according to a preferred embodiment of the present invention. Please refer to FIG. 7A and FIG. 7B at the same time, PB represents the probe signal (Probe Signal), and VF represents the filter signal. It can be seen that in the absence of the RFID tag, the filtered signal VF is hardly attenuated, but with the RFID tag, the filtered signal VF is severely attenuated.

FIG. 8A is an operation waveform diagram of a low power consumption RFID device without an RFID tag according to a preferred embodiment of the present invention. FIG. 8B is an operation waveform diagram of a low power consumption RFID device having an RFID tag according to a preferred embodiment of the present invention. Please refer to Figure 8A and Figure 8B at the same time. From the above, in the case of no RFID tag, the filtered signal VF will hardly be attenuated, so the filtered signal VF will be greater than the reference voltage Vref for a long time. Therefore, the comparison The signal CP will maintain positive saturation for a long time. In the case of RFID tags, the filtering signal VF is seriously attenuated, so the filtering signal VF is greater than the reference voltage Vref only for a relatively short time, so the comparison signal CP only maintains positive saturation for a relatively short time. The control circuit 200 can determine whether a label is placed on the coil L1 by comparing the time period that the signal CP maintains positive saturation for a long period of time.

FIG. 9 is a circuit diagram of the wake-up circuit 202 of the low power consumption RFID device according to a preferred embodiment of the present invention. Please refer to FIG. 6 and FIG. 9 , the difference between the two circuits is that the wake-up circuit 202 additionally adds a digital-to-analog converter 901 . In this example, when When the low power consumption RFID device performs the above-mentioned calibration procedure according to the background value, the reference voltage can be output to the above-mentioned digital-to-analog converter 901 through the internal digital threshold value, and the digital-to-analog converter 901 converts the digital threshold value into an analog The reference voltage Vref, so the reference voltage can be used as a representative of the threshold signal.

To sum up, the spirit of the present invention is to use the normal sleep mode and send a short-time carrier signal (detection signal), and detect the amount of energy on the coil to determine whether there is an RFID tag on the coil, thereby reducing RFID reading. The power consumption of the device, so the present invention can be applied to the device using the battery. Furthermore, in a preferred embodiment, the method of continuously changing the threshold value according to the background value is also adopted, so that the determination of the radio frequency tag reading device is more accurate.

The specific embodiments proposed in the detailed description of the preferred embodiments are only used to facilitate the description of the technical content of the present invention, rather than restricting the present invention to the above-mentioned embodiments in a narrow sense, without exceeding the spirit of the present invention and applying for patents below The situation of the scope, the various changes and implementations made, all belong to the scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope of the appended patent application.

S301~S305: each step of the low power consumption radio frequency identification method of a preferred embodiment of the present invention

Claims (4)

A low power consumption radio frequency identification method, suitable for a radio frequency identification tag reading device, the low power consumption radio frequency identification method comprises: step A: entering a normal sleep mode; step B: performing a wake-up procedure every preset time, and A probe signal (Probe Signal) is sent from a coil; Step C: Detect whether the magnitude of the energy on the coil is less than a threshold value; and Step D: When the magnitude of the energy on the coil is greater than the threshold value, go back to Step A , wherein, when the magnitude of the energy on the coil is smaller than the threshold value, it further includes: continuously sending a carrier signal; receiving a return data returned by a tag; and decoding the return data, wherein, decoding the return data After the data is obtained, it further includes: judging whether to obtain the radio frequency identification code; and when the judgment is no, performing a threshold value calibration procedure, setting a calibration threshold value according to the background value, and replacing the threshold value with the calibration threshold value. The low power consumption radio frequency identification method as described in claim 1, wherein, when the magnitude of the energy on the coil is greater than the threshold value, before returning to step A, further comprising: A threshold value calibration procedure is performed, a calibration threshold value is given according to the background value, and the threshold value is replaced by the calibration threshold value. A low power consumption radio frequency identification device, comprising: an LC resonance circuit, including a coil; a wake-up circuit, coupled to the LC resonance circuit; wherein, the low power consumption radio frequency identification device operates in a normal sleep mode, wherein each At a preset time, a wake-up procedure is performed, and a probe signal (Probe Signal) is sent from the coil, wherein the wake-up circuit detects whether the magnitude of the energy on the coil is less than a threshold value, and when the magnitude of the energy on the coil is greater than the The threshold value is returned to the normal sleep mode, wherein when the time of the comparison signal output by the comparison circuit in the first state is less than a threshold time, the low power consumption RFID device is controlled to continuously send a carrier signal; a return data; and decoding the return data, wherein the wake-up circuit further includes: a digital-to-analog conversion circuit for outputting the threshold signal, Wherein, when the low-power consumption radio frequency identification device performs the calibration procedure, the digital threshold value input by the digital-to-analog conversion circuit is adjusted, and the threshold signal has been adjusted. The low power consumption radio frequency identification device as claimed in claim 3, wherein the wake-up circuit comprises: a peak detector for detecting the voltage peak of the coil and outputting a peak signal; a filter circuit coupled to the peak a detector, which receives the peak signal and performs a low-pass filter to output a filtered signal; and a comparison circuit, which includes a first input end and a second input end, wherein the first input end receives the filtered signal, The second input terminal receives a threshold signal, wherein when the time of the comparison signal output by the comparison circuit in the first state is greater than a threshold time, the low power consumption RFID device is controlled to return to the normal sleep mode, and a calibration is performed The program adjusts the threshold signal according to the background value.

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