KR101187910B1 - RFID reader and method for controlling thereof - Google Patents

Abstract

The present invention relates to an RFID reader capable of correcting a signal of an RFID tag when the signal is distorted by inspecting a signal received from the RFID tag, and a control method thereof. The present invention comprises the steps of: processing an encoded received signal received from the outside to generate an input signal having a plurality of channel signals; Checking each channel signal for violation of modulation rules; Comparing the number of errors in violation of the modulation rules of each of the channel signals to select the channel signal having the least error as a selection signal; Determining the type of error in the selection signal; Generating a correction signal by correcting an error of the selection signal according to the type of error; And decoding the correction signal to generate received data.

Description

RFID reader and method for controlling it

The present invention relates to an RFID reader and a control method thereof, and more particularly, to an RFID reader capable of identifying a tag and recording and reading additional information by an identification number of a corresponding object stored in a tag attached to each object, and control thereof. It is about a method.

Recently, wireless communication technology is widely used in all industries including distribution. As an example in which wireless communication technology is used, there are technical fields such as smart card and radio frequency identification (RFID). RFID system can be applied to various applications such as logistics management marker, electronic identification card, electronic money, credit card by inputting various information into integrated circuit chip.

The wireless communication technology may be used to obtain information about a product wirelessly. For this purpose, the wireless communication system includes an RFID tag attached to the product and a reader for wireless communication with the RFID tag. The RFID tag is provided with an antenna and an RFID chip so that information from the reader is stored and updated in the RFID chip through the antenna, and information stored in the RFID chip is transmitted to the reader through the antenna.

Recently, UHF wireless recognition system using Ultra High Frequency (UHF) band of 860MHz ~ 950MHz band is used as RFID system. UHF wireless recognition system of the ultra high frequency band has the advantage of fast transmission speed and the amount of data that can be transmitted on the frequency.

In an RFID system using RFID technology, an RFID tag modulates and reflects a radio signal transmitted from an antenna of a reader according to information stored in an RFID chip, and the reader reads information stored in the RFID chip from the modulated and reflected radio signal. Done.

On the other hand, since some of the information read from the RFID tag is lost or distorted through the RF signal receiver of the reader, an error may occur in the process of reading the information read from the RFID tag.

An object of the present invention is to provide an RFID reader and a control method thereof capable of correcting a signal of an RFID tag when the signal is distorted by inspecting a signal received from the RFID tag.

The present invention comprises the steps of: processing an encoded received signal received from the outside to generate an input signal having a plurality of channel signals; Checking each channel signal for violation of modulation rules; Comparing the number of errors in violation of the modulation rules of each of the channel signals to select the channel signal having the least error as a selection signal; Determining the type of error in the selection signal; Generating a correction signal by correcting an error of the selection signal according to the type of error; And decoding the correction signal to generate received data.

In the case of the 1-bit error, the immediately preceding bit of the symbol without signal inversion becomes an error bit, and the data of the error bit is inverted to correct the error.

In the case of the multi-bit error, calculating a start position and an end position where the error occurs in the selection signal and setting a correction range; Moving the data within the correction range back one bit; And a bit of the start position becomes an error bit, and inverting data of the error bit, thereby correcting the error.

Another aspect of the present invention, the receiving signal processing unit for processing the encoded received signal received from the outside to generate an input signal having a multi-channel signal; And a controller for inspecting an error in violation of a modulation rule in the channel signal, correcting an error of the channel signal when the error occurs, generating a correction signal, and decoding the correction signal to generate received data. Provide an RFID reader.

An error checker for checking the error in each of the channel signals, an error checker for determining a type of the error, correcting an error of the channel signal according to the type of the error, and generating a correction signal; A decoder may be provided for decoding the correction signal to generate received data.

According to the RFID reader and its control method according to the present invention, it is possible to correct an error included in a signal received from an RFID tag.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an RFID reader 10, which is a preferred embodiment of the present invention. 2 is a block diagram of the inside of the control unit 200 in the RFID reader 10 of FIG.

Referring to the drawings, the RFID reader 10 includes a received signal processor 100; Control unit 200; And an output signal processor 300. The RFID reader 10 may form an RFID system together with an RFID tag. The RFID tag may be attached to each object and store ID of the object. The RFID reader 10 may identify the RFID tag and may record additional information into or read from the RFID tag.

The reception signal processor 100 may generate an input signal having a multi-channel signal by processing the encoded reception signal received from the outside. The controller 200 may check an error in violation of the modulation rule in the channel signal, correct the error of the channel signal when an error occurs, generate a correction signal, and decode the correction signal to generate received data.

In addition, the control unit 200 may generate an output signal transmitted to the tag. The output signal processor 300 configured as a mixer may generate an output signal to be transmitted to the outside by combining the output signal having the I / Q channel into one signal.

There are various international standards such as data coding, modulation, anti-collision, data decoding and demodulation. Currently, EPC Class 1 Generation 2 [3] (hereafter C1 Gen2) has been registered in ISO / IEC, and is widely used internationally.

The RFID reader 10 according to the present embodiment may be based on the operation of the RFID system based on the C1 Gen2 standard. In addition, the present invention is not limited thereto, and the RFID reader 10 may be operated by a communication method according to various international standards such as a data encoding, a modulation method, an anti-collision method, a data decoding and a demodulation method.

In the RFID system, the response power (-60dBm) from the tag to the reader is very small compared to the transmission signal power (30dBm) from the RFID reader to the RFID tag. Therefore, the performance of the reader depends largely on how well the RFID reader receiver recovers the response signal of the tag. This environment acts as a deciding factor in the performance of the portable reader. In the case of a portable reader, the user's reader environment is the same as that of the mobile environment, and the operating environment is worse than the fixed type due to the multipath fading, frequency selective fading, and exposure to noise that occur in the mobile environment. In such an environment, the performance of the reader receiver for processing the response signal of the tag determines the performance of the entire portable RFID system.

In particular, an error may occur in the process of reading the information read from the RFID tag because some of the information read from the RFID tag is lost or distorted through the RFID signal receiving units 101 and 120 of the RFID reader 10.

Therefore, the RFID reader 10 according to an exemplary embodiment of the present invention checks an error in an input signal input through the RFID signal receivers 101 and 120, and corrects the error when an error occurs. . Therefore, the performance of the RFID system can be improved.

The reception signal processor 100 may generate an input signal having a multi-channel signal by processing the encoded reception signal received from the outside. The reception signal may be received from the outside through the reception antenna 101 from the RFID tag. In this case, the received signal may be a modulated analog signal received through the receiving antenna 101, and the input signal may be a digital signal that can be processed by the controller 200 by processing the received signal.

The received signal received from the RFID tag may be encoded by frequency modulation 0 (FM0). In this case, the RFID reader 10 needs to convert the received signal and decode the FM0.

In the ISO / IEC 18000-6 standard, FM0 is a common modulation technique used for response signals from defined RFID tags to RFID readers. Types include Type A, Type B, and Type C. Type A and Type B should use only FM0, and Type C should use either FM0 or Miller Subcarrier, but FM0 uses simpler data and waveforms than Miller Subcarrier. There is an advantage that it is easy to do.

The reception signal processor 100 may include a band pass filter (BPF), a balun 110, a mixer 120, a low pass filter (LPF), and an analog-to-analog converter. Digital Converter, ADC). A band pass filter (BPF) and a low pass filter (LPF) may remove noise from each signal.

The received signal is input to the mixer 120 after passing through the band pass filter (BPF) and the balun. The mixer 120 may convert the noise canceled and converted received signal and output the converted I channel baseband signal and the Q channel baseband signal. As the mixer 120, a homodyne receiver may be used. In this case, the mixer 120 may include a quadrature-phase mixer indicating a phase difference between an in-phase mixer and 1/2 π radians.

The channel signal generated by the mixer 120 may include an I channel signal and a Q channel signal. The I channel signal may correspond to the cosine component of the received signal, and the Q channel signal may correspond to the sine component of the received signal.

The multi-channel signal is converted into an input signal of a digital signal through a low pass filter (LPF) and an analog to digital converter (ADC).

The input signal may include preamble and frame data. At this time, the preamble may be input in the order of the frame data.

The preamble is located in front of the frame data to indicate that the frame data starts from the next. The controller 200 may generate received data from frame data among input signals. If the preamble is detected, the control unit 200 determines that a response is input, and extracts and processes a binary signal as long as necessary for FM0 decoding after the preamble.

The controller 200 may check an error in violation of the modulation rule in the channel signal, correct the error of the channel signal when an error occurs, generate a correction signal, and decode the correction signal to generate received data. To this end, the controller 200 may include an error checker 210, an error corrector 220, and a decoder 230.

The controller 200 may be a central processing unit of the RFID reader 10, and may be a general CPU (Central Processing Unit) or a microcomputer or a digital signal processor (DSP).

The error check unit 210 may check an error in each channel signal. The error correction unit 220 may determine the type of error and generate a correction signal by correcting the error of the channel signal according to the type of error. The decoder 230 may generate received data by decoding the correction signal.

The channel signal may include 0 symbols and 1 symbols represented by 2 bits having a value of 0 or 1, respectively. 3, symbols representing 0 and 1, respectively, are shown. Transitions occur between successive symbols. Accordingly, as shown in FIG. 3, two symbols indicating 0 and one symbol indicating 1 may be provided according to the transition state.

In the RFID system, it is possible to determine whether there is an error when FM0 decoding by converting a signal received from a tag into a binary signal. The symbols of FM0 are as shown in FIG. As shown in FIG. 3, a transition occurs between symbols and a zero symbol transition occurs in the middle of a symbol. If no transition occurs between the symbols, the rule of FM0 is violated and an error may be determined.

Therefore, the error check unit 210 checks each symbol position in the channel signal, checks whether the signal is inverted between the symbols, and determines that the modulation rule is violated when there is no signal inversion between the symbols. can do.

The main reason for violating the rules of FM0 is distortion in the signal received via the Air Interface. In this case, the signal after passing through the RFID signal receiving units 101 and 120 is lost or distorted.

In addition, a case may occur where the signal is delayed. That is, in the binary signal, the actual RFID tag is transmitted 1 bit, but is recognized as 2 bits in the RFID reader 10. In these cases, the rule of FM0 is violated, so it can be determined as an error case.

The error correction unit 220 compares the number of errors in violation of the modulation rules of each channel signal, selects the channel signal having less error as the selection signal, determines the type of the error in the selection signal, and selects the type according to the type. Correct the error contained in the signal.

First, while FM0 decoding is performed, the number of violations of FM0 and position information of one normal symbol of the I channel signal and the Q channel signal are stored. It also stores the rule violation location of FM0. Compare the number of FM0 violations between channels to select the signal of the channel with fewer error occurrences.

By comparing the error types of the I channel signal and the Q channel signal, if an error occurs only once, it is determined to be a 1-bit error.

The error type may be one bit error and multiple bit error. One bit error is when an error occurs in one symbol of the channel signal. The multi-bit error is when an error occurs in a plurality of symbols in the channel signal.

In particular, a multi-bit error may be a case where one of the binary bits in the preceding symbol is not recognized because the bit is lost or distorted too short, resulting in a large number of errors due to the effect that the incoming signals are advanced by one bit. have.

In the case of 1-bit error, the immediately preceding bit of the symbol without signal inversion becomes an error bit, and the data of the error bit is inverted to correct the error. 4 shows a correction method in the case of a 1-bit error. The next symbol of the symbol indicated by the dotted line in the selection signal did not transition.

Therefore, the immediately preceding bit of the symbol without signal inversion can be regarded as an error bit. Therefore, by inverting the data of the error bits, the error can be corrected to generate the power failure signal. That is, in the case of 1-bit error, the LSB (Least Significant Bit) of the preceding symbol is not reversed.

In the case of a multi-bit error, a correction range is set by calculating a start position and an end position at which an error occurs in the selection signal, shifting the data within the correction range by one bit, and the bit at the start position becomes an error bit. By inverting the data of the bit, the error can be corrected. 5 and 6 illustrate a correction method in the case of a multi-bit error.

In the case of a multi-bit error, the correction range is determined from the previous symbol where no symbol transition occurs to the normal one symbol. As shown in FIG. 5, when the number of bits in the correction range is N, the Nth bit is removed and the third to Nth bits are delayed by one bit so as to be the fourth to Nth bits. Copies and adds the same bit as the 1st bit to the 2nd bit.

In this case, when one of the following bits is stretched and distorted, one bit is recognized as two bits and thus may not be damaged until the end. Therefore, it is preferable to specify a correction range. 6 shows a flow of matters described so far.

If the FM0 rule is violated after the error correction process and the FM0 decoding process, the re-recognition process designated for each tag type can be performed. Alternatively, if the FM0 rule is not violated but the data recovery is not performed normally, it will be determined as an error in the CRC (Code Redundancy Code) check and may be re-recognized.

In addition, the controller 200 may generate an output signal. The output signal may have a plurality of channels. The output signal processing unit 300 may generate an output signal to be transmitted to the outside by combining the output signal having a plurality of channels into one signal.

The output signal processor 300 may include a band pass filter (BPF), a balun 110, a mixer 320, a low pass filter (LPF), and a digital-to-digital converter. Analog Converter, DAC) can be provided. The transmission signal may be transmitted to the RFID tag through the transmission antenna 301.

7 is a flowchart of a control method (S700) of the RFID reader according to the preferred embodiment of the present invention.

Referring to the drawings, the control method (S700) of the RFID reader may be performed in the control unit 200 of the RFID reader 10 shown in Figs. In the control method (S700) of the RFID reader, for the same matters as those described for the RFID reader 10, this is referred to, and detailed description thereof will be omitted. The control method S700 of the RFID reader may check an error included in an input signal generated from a received signal received from an RFID tag, and correct the error. Therefore, the control method (S700) of the RFID reader can improve the performance of the RFID system.

To this end, the control method (S700) of the RFID reader includes an input signal generation step (S705); Modulation rule violation checking step (S710, S720); Selection signal selection steps S730, S740, and S750; An error type determination step (S760); Error correction steps (S770, S780); And a decoding step (S790).

In the input signal generation step (S705), the encoded signal received from the outside is processed to generate an input signal having a plurality of channel signals. In the modulation rule violation checking step (S710, S720), each channel signal is checked for violation of the modulation rule.

In the selection signal selection steps S730, S740, and S750, the number of errors in violation of the modulation rules of the respective channel signals is compared to select a channel signal having fewer errors as the selection signal. In the error type determination step (S760), the type of error is determined from the selection signal.

In the error correction steps S770 and S780, an error of the selection signal is corrected according to the type of error to generate a correction signal. In the decoding step S790, received data is generated by decoding the correction signal.

The plurality of channel signals may include an I channel signal corresponding to a cosine component of the received signal and a Q channel signal corresponding to a sine component of the received signal. The received signal may be a modulated analog signal received from an RFID tag through a receive antenna, and the input signal may be a digital signal that may be processed by a controller of the RFID reader by processing the received signal.

In the modulation rule violation checking step (S710, S720), a symbol position is checked in each channel signal (S710), and whether a modulation rule is violated in each channel signal (S720).

Meanwhile, the received signal received from the RFID tag may be encoded by frequency modulation 0 (FM0). In this case, the RFID reader needs to convert the received signal and perform FM0 decoding. Thus, the modulation rule may be an FM0 modulation rule.

In the selection signal selection steps S730, S740, and S750, it is determined whether an error occurs (S730), and when an error occurs, the number of errors that violate the modulation rule of each channel signal is compared (S740), and as a result, the error. A channel signal having few values is selected as the selection signal (S750). In operation S730, if an error does not occur, a decoding step S790 may be performed.

At this time, by checking each symbol position in the channel signal, and whether the signal inversion between each symbol is checked, it can be determined that the modulation rule is violated when there is no signal inversion between symbols.

In the error type determination step (S760), the type of error is determined in the selection signal. The error type may include a 1-bit error and a multi-bit error. One bit error is when an error occurs in one symbol of the channel signal. The multi-bit error is when an error occurs in a plurality of symbols in the channel signal.

In the error correction steps S770 and S780, a correction signal is generated by correcting an error of the selection signal according to the type of error. When the error type is a 1-bit error, the 1-bit error correction step S770 is performed, and the error type is corrected. In the case of the multi-bit error, a multi-bit error correction step S780 may be performed.

In the 1-bit error correcting step S770, the immediately preceding bit of the symbol without signal inversion becomes an error bit, and the data of the error bit is inverted to correct an error. 4 illustrates a correction method in the case of a 1-bit error. The next symbol of the symbol indicated by the dotted line in the selection signal is not transitioned.

Therefore, the immediately preceding bit of the symbol without signal inversion can be regarded as an error bit. Therefore, by inverting the data of the error bits, the error can be corrected to generate the power failure signal. That is, in the case of 1-bit error, the LSB (Least Significant Bit) of the preceding symbol is not reversed.

In the multi-bit error correction step (S780), a correction range is set by calculating a start position and an end position at which an error occurs in the selection signal, shifting the data within the correction range by one bit, and the bit at the start position becomes an error bit. The error can be corrected by inverting the data of the error bit. 5 and 6 illustrate a correction method in the case of a multi-bit error.

The multi-bit error correction step S780 may include a correction range calculation step S781, a data movement step S782, and an error bit inversion step S783.

In the correction range calculation step (S781), a correction range is set by calculating a start position and an end position at which an error occurs in the selection signal. In the data movement step S782, the data within the correction range is shifted backward by one bit. In the error bit inversion step S783, the bit at the start position becomes an error bit and inverts the data of the error bit.

In the case of a multi-bit error, the correction range is determined from the previous symbol where no symbol transition occurs to the normal one symbol. As shown in FIG. 5, when the number of bits in the correction range is N, the Nth bit is removed and the third to Nth bits are delayed by one bit so as to be the fourth to Nth bits. Copies and adds the same bit as the 1st bit to the 2nd bit.

In this case, when one of the following bits is stretched and distorted, one bit is recognized as two bits and thus may not be damaged until the end. Therefore, it is preferable to specify a correction range. 6 shows a flow of matters described so far.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

1 is a block diagram schematically showing an RFID reader as a preferred embodiment according to the present invention.

FIG. 2 is a block diagram schematically illustrating the inside of a controller in the RFID reader of FIG. 1.

3 is a diagram schematically illustrating an embodiment of symbols included in a channel signal.

4 is a diagram schematically illustrating a correction method in the case of a 1-bit error.

5 is a diagram schematically illustrating a correction method in the case of a multi-bit error.

FIG. 6 is a diagram schematically illustrating a method of correcting a plurality of bit errors of FIG. 5.

7 is a flowchart schematically showing a control method of an RFID reader as a preferred embodiment according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10: RFID reader, 100: receiving signal processing unit,

200: control unit, 300: output signal processing unit,

210: error check unit, 220: error correction unit,

230: Decoder.

Claims (15)

Processing an encoded received signal received from the outside to generate an input signal having a plurality of channel signals; Checking each channel signal for violation of modulation rules; Comparing the number of errors in violation of the modulation rules of each of the channel signals to select the channel signal having the least error as a selection signal; Determining the type of error in the selection signal; Generating a correction signal by correcting an error of the selection signal according to the type of error; And And decoding the correction signal to generate received data. The method of claim 1, And the plurality of channel signals include an I channel signal corresponding to a cosine component of the received signal and a Q channel signal corresponding to a sine component of the received signal. The method of claim 1, And a 0 symbol and a 1 symbol represented by 2 bits having a value of 0 or 1, respectively, of the channel signal. The method of claim 1, The control method of the RFID reader for checking the position of each symbol in the channel signal, and whether the signal inversion between each symbol, by determining that the modulation rule is violated when there is no signal inversion between the symbols. . The method of claim 3, And the error type comprises a one bit error in which the error occurs in one of the symbols in the channel signal and a multiple bit error in which the error occurs in a plurality of the symbols in the channel signal. The method of claim 5, In the case of the 1-bit error, the immediately preceding bit of the symbol without signal inversion becomes an error bit, and the data of the error bit is inverted so that the error is corrected. The method of claim 5, In the case of the multi-bit error, setting a correction range by calculating the start position and the end position where the error occurred in the selection signal, moving the data within the correction range back by one bit, and the start position And a bit becomes an error bit, and inverting data of the error bit, thereby correcting the error. A reception signal processing unit processing an encoded reception signal received from the outside to generate an input signal having a plurality of channel signals; An error check unit for checking an error in each of the channel signals; Comparing the number of errors in violation of the modulation rules of each of the channel signals to select the channel signal with less error as the selection signal, determine the type of the error in the selection signal, An error correction unit for correcting an error of the channel signal to generate a correction signal; And And a decoder for decoding the correction signal to generate received data. delete Claim 10 has been abandoned due to the setting registration fee. 9. The method of claim 8, The error checker checks each symbol position in the channel signal and checks whether the signal is inverted between the symbols, and determines that the modulation rule is violated when there is no signal inversion between the symbols. RFID reader. Claim 11 was abandoned upon payment of a setup registration fee. The method of claim 10, RFID reader comprising 0 symbols and 1 symbol represented by 2 bits each having a value of 0 or 1; delete Claim 13 was abandoned upon payment of a registration fee. 12. The method of claim 11, And wherein the error type comprises a one bit error in which the error occurs in one of the symbols in the channel signal and a multiple bit error in which the error occurs in a plurality of the symbols in the channel signal. Claim 14 has been abandoned due to the setting registration fee. 14. The method of claim 13, In the case of the 1-bit error, the immediately preceding bit of the symbol without signal inversion becomes an error bit, and the data of the error bit is inverted to correct the error. Claim 15 is abandoned in the setting registration fee payment. 14. The method of claim 13, In the case of the multi-bit error, a correction range is set by calculating a start position and an end position at which the error occurs in the selection signal, shifting data within the correction range backward by one bit, and the bit at the start position is an error bit. RFID reader to correct the error by inverting the data of the error bit.

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