KR100943766B1 - Method for excluding offset noise, method and apparatus for receiving tag signal - Google Patents

Abstract

The present invention relates to an offset distortion canceling method, a tag signal receiving method and apparatus.

In the present invention, the tag signal receiving apparatus performs filtering to remove the high frequency component and the noise component from the tag signal received from the RFID tag, and removes the offset distortion signal. Thereafter, the tag signal receiver generates an edge signal from the tag signal from which the high frequency component, the noise component, and the offset distortion signal are removed, and determines bit data based on the generated edge clock based on the generated edge signal.

RFID, tag, offset distortion, edge signal, tag data, bit data

Description

Method for removing offset distortion, method and apparatus for receiving tag signal {Method for excluding offset noise, method and apparatus for receiving tag signal}

The present invention relates to an offset distortion canceling method, a tag signal receiving method and apparatus. In particular, the present invention relates to a method for removing offset distortion signals, a tag signal receiving method, and an apparatus in a radio frequency identification (RFID) reader.

The present invention is derived from the research conducted as part of the IT growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Telecommunication Research and Development. [Task Management No .: 2006-S-023-02, Title: RFID System Advancement Technology Development] .

In general, Radio Frequency Identification (RFID) uses radio frequency to read or record information from a tag having unique identification information in a non-contact manner to identify tagged objects, animals, and people. A technology that enables recognition, tracking, and management. The RFID system is composed of a plurality of tags (electronic tags or transponders) attached to an object or animal with unique identification information, and an RFID reader (Reader or Interrogator) for reading or writing the information of the tags. The RFID system is classified into mutual induction and electromagnetic waves according to the intercommunication method between the reader and the tag, and is classified into active and passive types according to whether the tag operates with its own power. It is divided into short wave, microwave and microwave.

Meanwhile, a tag signal receiving apparatus of a conventional RFID reader performs ASK (Amplitude-Shift Keying) demodulation on a tag signal input to an antenna and generates bit data from the ASK demodulated tag signal. Therefore, the conventional tag signal receiving apparatus has a disadvantage in that it does not respond when the tag signal is changed to the PSK scheme or when the ASK scheme and the PSK scheme are simultaneously performed.

In addition, when the tag signal receiving apparatus of the conventional RFID reader generates distortion noise due to an offset phenomenon or the like in a tag signal inputted through an antenna and passes through an analog unit, when ASK demodulation occurs, performance deterioration occurs and it is impossible to detect reliable tag data. There are disadvantages.

Accordingly, there is a need for a method and apparatus capable of successfully restoring tag data regardless of a modulation scheme, even when distortion noise due to an offset phenomenon exists in a tag signal input through an antenna.

An object of the present invention is to provide an offset distortion cancellation method, a tag signal receiving method, and an apparatus for successfully restoring tag data regardless of a modulation scheme.

Offset distortion removing method in a radio frequency identification reader according to a feature of the present invention for achieving the above object,

Calculating a continuous value of a tag signal from a signal received at a radio frequency identification tag; Adjusting the gain of the continuous tag signal average value; And removing the offset distortion signal from the received signal using the average value of the successive tag signals with the gain adjusted.

In addition, the tag signal receiving method in a radio frequency identification reader according to another aspect of the present invention,

Removing an offset distortion signal from the received signal using a continuous tag signal average value calculated through a moving average filter from a signal received from a radio frequency identification tag; Generating an edge signal from the signal from which the offset distortion signal has been removed; Detecting edge information from the edge signal; And determining bit data corresponding to a tag signal based on the edge clock generated from the edge information.

In addition, the tag signal receiving apparatus according to an aspect of the present invention,

A filter unit for outputting a signal from which a high frequency component and a noise component are removed from a signal received from a radio frequency identification tag; An offset signal removing unit outputting a signal from which an offset distortion signal is removed from the signal output from the filter unit; An edge signal generator for generating an edge signal from the signal output from the offset signal remover; An edge information detector for extracting edge information from the edge signal and generating an edge clock corresponding to the edge information; And a data decoding unit for determining bit data based on the edge clock and detecting the preamble based on the bit data.

According to the present invention, the tag signal receiving apparatus of the RFID reader can acquire the tag data robust and reliable to the offset distortion signal faster without performing a separate switching according to the modulation scheme.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… group” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software.

Hereinafter, a tag signal receiving apparatus and method in a radio frequency identification (RFID) reader according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a structural diagram illustrating a tag signal receiving apparatus 100 according to an embodiment of the present invention, which shows a tag signal receiving apparatus 100 in an RFID reader.

Referring to FIG. 1, the tag signal receiving apparatus 100 includes a demodulator 110, an edge information detector 120, and a data decoder 130.

The demodulator 110 includes a filter 111, an offset signal remover 112, and an edge signal generator 113. The demodulator 110 is received from an RFID tag through a reader antenna (not shown) and an analog part (not shown). An edge signal is generated and output from a baseband tag signal (I channel / Q channel tag signal) inputted through. Here, the I channel tag signal and the Q channel tag signal mean that a tag signal which is a sine wave signal is associated with a complex coordinate system.

The filter unit 111 filters the input baseband tag signal, that is, the I channel tag signal and the Q channel tag signal, respectively, and removes and outputs unwanted high frequency components and noise components. Here, when the input tag signal is FM0 (Frequency Modulation 0), the filter unit 111 filters using a low pass filter, and the input tag signal is a Miller sub-carrier. ) Signal is performed using a band pass filter.

The offset signal removing unit 112 removes the offset distortion signal from the tag signal output from the filter unit 111 and outputs the offset distortion signal. At this time, the offset signal removing unit 112 removes and outputs an offset distortion signal for each of the I channel tag signal and the Q channel tag signal.

The edge signal generator 113 outputs an edge signal from the signal output from the offset signal remover 112. Here, the edge signal refers to a signal that contains information of the point at which the sign of the slope of the tag signal changes.

The edge information detector 120 detects edge information from the edge signal output from the demodulator 110 and generates an edge clock corresponding to the detected edge information.

The data decoding unit 130 analyzes an edge clock output from the edge information detection unit 120 to determine bit data, and outputs tag data using the determined bit data.

2 is a structural diagram illustrating an offset signal remover 112 according to an embodiment of the present invention.

 Referring to FIG. 2, the offset signal removing unit 112 includes a moving average filter (MAF) 1121, a gain unit 1122, and a subtractor 1123.

 The MAF 1121 continuously calculates an average value of the I channel tag signal and the Q channel tag signal respectively filtered and output from the filter unit 111. The continuous average value of the tag signal calculated as described above is adjusted by the gain unit 1122, and the subtractor 1123 is input to the offset signal removing unit 112 using the average value of the continuous tag signal whose gain is adjusted. The offset distortion signal is removed from each tag signal to be output.

3 is a structural diagram illustrating an edge signal generator 113 according to an embodiment of the present invention.

Referring to FIG. 3, the edge signal generator 113 includes a matched filter 1131, an absolute value generator 1132, a squarer 1133, a summer 1134, and a level determiner 1135. .

In general, the matched filter refers to a filter whose filter factor matches the characteristics of a known input signal, and indicates a maximum output value when the corresponding signal is input, and the matched filter 1131 in the tag signal receiving apparatus 100 is offset. When the I channel tag signal and the Q channel tag signal from which the offset signal is removed are input by the signal remover 112, each tag signal is filtered to detect an accurate edge signal. Here, the I channel tag signal and the Q channel tag signal are filtered using the same coefficient, and the coefficients of the matching filter 1131 vary depending on the shape of the tag signal. That is, in order to accurately detect the edge signal from the tag signal, the tag signal receiving apparatus 100 sets the coefficients of the matching filter 1131 corresponding to the shape of the tag signal.

When the tag signal is an FMO signal and a " 0 " symbol having one transition in one symbol is set as the basic signal of the matching filter 1131, the coefficient of the matching filter 1131 is expressed by Equation 1 below. Is the same as

Here, nTerm is a variable for determining the shape of the matched filter 1131, and nSamp is an order of the matched filter 1131, and is set equal to the number of samples per symbol for demodulation of the received tag signal.

That is, when the tag signal is input close to the square pulse, the RFID tag signal receiving apparatus 100 sets the coefficient of the matched filter similar to the shape of the tag signal by increasing the nTerm value, and the tag signal is sinusoidal due to band limitation. When input close to the pulse, the nTerm value can be reduced to set the coefficient of the matched filter similarly to the shape of the tag signal.

On the other hand, each signal filtered through the matched filter 1131 is passed through the absolute value generator 1132, the squarer 1133, summed in the summer 1134 and output as one first edge signal.

 The level determiner 1135 removes a noise component of a specific level from the first edge signal output from the summer 1134 and outputs a second edge signal.

As described above, the tag signal receiving apparatus 100 may simply use a binary phase shift key (BPSK) or amplitude using a matched filter 1131, an absolute value generator 1132, a squarer 1133, and the like. An edge signal of a received tag signal may be generated by being modulated by an amplitude shift key (ASK). In addition, even if the link frequency (LF) of the RFID tag changes, it is possible to accurately detect the edge component of the tag signal. Accordingly, the tag data decoding processing speed of the tag signal receiving apparatus 100 is improved, and the reliability of the tag data is also increased.

4 is a structural diagram illustrating a data decoding unit 130 according to an embodiment of the present invention.

4, the data decoding unit 130 includes a bit data determiner 131 and a preamble detector 132.

The bit data determiner 131 restores a data pulse (decoded data) from the edge clock output from the edge information detector 120, and determines the bit data based on the pulse width of the recovered data pulse. For example, when the FM0 tag signal is input, the bit data determiner 131 may determine that the pulse width of the recovered data pulse is narrow as bit 0 and the wide pulse width is bit 1.

The preamble detector 132 detects a preamble of the tag signal based on the bit data output from the bit data determiner 131, and outputs tag data using the detected preamble. That is, a preamble containing start information of tag data is detected from bit data, and tag data is detected and output based on the preamble.

As described above, the tag signal receiving apparatus 100 generates bit data corresponding to the tag signal by using the edge signal generated from the baseband tag signal received through the antenna and input through the analog unit, thereby generating the tag signal. Regardless of the modulation scheme, it is possible to generate reliable bit data for the tag signal.

Next, a tag signal receiving method of the tag signal receiving apparatus 100 according to an exemplary embodiment of the present invention will be described in detail with reference to the drawings.

5 is a flowchart illustrating a tag signal receiving method of the tag signal receiving apparatus 100 according to an exemplary embodiment of the present invention.

6 illustrates an example of a baseband tag signal input to a tag signal receiving apparatus according to an exemplary embodiment of the present invention, and illustrates a tag signal distorted by a high frequency component, a noise component, and an offset distortion signal. will be. 7 illustrates an example of a tag signal from which a high frequency component, a noise component, and an offset distortion signal are removed according to an exemplary embodiment of the present invention.

8 is a flowchart illustrating a method for generating an edge signal of the tag signal receiving apparatus 100 according to an exemplary embodiment of the present invention, and FIG. 9 is a flowchart illustrating a method of generating an edge signal according to an exemplary embodiment of the present invention. An example is shown.

10 is a flowchart illustrating an edge clock generation method according to an exemplary embodiment of the present invention, and FIG. 11 illustrates an example of an edge clock and data pulses (decoded data) generated based on edge information.

Referring to FIG. 5, the tag signal receiving apparatus 100 performs filtering to remove unwanted high frequency components and noise components from a baseband tag signal received through an antenna from an RFID tag and input through an analog unit (S101). . At this time, the tag signal receiving apparatus 100 performs filtering on the baseband tag signal, that is, the baseband I channel tag signal and the Q channel tag signal, respectively. When the tag signal is the FM0 signal, the low pass band filtering is performed. If the tag signal is a Miller subcarrier signal, bandpass filtering is performed.

Thereafter, the tag signal receiving apparatus 100 removes and outputs an offset distortion signal from the I channel tag signal and the Q channel tag signal from which the high frequency component and the noise component are removed (S102).

6 illustrates an example of a tag signal distorted by a high frequency component, a noise component, and an offset distortion signal, and FIG. 7 illustrates a high frequency component and noise by the tag signal receiving apparatus 100 through steps S101 and S102. An example of a tag signal from which component and offset distortion signals are removed is shown.

Referring to FIG. 7, it can be seen that the high frequency component, the noise component, and the offset distortion signal are alleviated in comparison with the tag signal shown in FIG. 6.

Referring back to FIG. 5, the tag signal receiver 100 removes the offset distortion signal from the tag signal and then generates an edge signal using the tag signal from which the high frequency component, the noise component, and the offset distortion signal are removed (S103). .

8 is a flowchart illustrating a method of generating an edge signal of the tag signal receiving apparatus 100.

Referring to FIG. 8, the tag signal receiving apparatus 100 first generates a first edge signal through a matching filter 1131, an absolute value generator 1132, a squarer 1133, and a summer 1134 (S201). ).

The generated first edge signal is compared with the reference level signal (S202). A portion of the first edge signal higher than the reference level signal is output as it is (S203), and a portion lower than the reference level signal is outputted as 0 to generate a second edge signal (S204). ). That is, the tag signal receiving apparatus 100 outputs the second edge signal from which the noise of a level lower than the reference level signal is removed from the first edge signal as the final edge signal. Therefore, the tag signal receiving apparatus 100 may detect edge information without error from the edge signal from which the noise is removed later. FIG. 9 illustrates an example of a first edge signal and a second edge signal generated by the above-described method. 9, it can be seen that the second edge signal has a low level of noise removed from the first edge signal.

Referring back to FIG. 5, when an edge signal is generated, the tag signal receiving apparatus 100 detects edge information from the edge signal and generates an edge clock corresponding to the detected edge information (S104). That is, the tag signal receiving apparatus 100 detects edge information, which is information about an edge (a point at which the sign of the slope of the tag signal changes), from the edge signal generated from the tag signal, and checks the edge information based on the detected edge information. Generate an edge clock that is enabled.

10 is a flowchart illustrating a method of generating an edge clock in the tag signal receiving apparatus 100.

Referring to FIG. 10, an edge signal is continuously sampled at a first time point n-dn, a second time point n, and a third time point n + dn, and a point to be determined whether the second time point is a current peak point. If it is a sampling time point corresponding to, the tag signal receiving apparatus 100 obtains the level (x (n-dn), x (n), x (n + dn)) of the edge signal for each sampling time point (S301). . Then, the first reference value dx_high and the second reference value dx_low at the second time point n to determine whether it is a peak point are calculated using Equation 2 below (S302).

dx_high = x (n + dn)-x (n)

dx_low = x (n)-x (n-dn)

Here, dn = 1, 2, 3, ... denotes sampling intervals between the time points used for generating reference values. That is, it is a value that determines how far the level of sampling time point is used for generating the first reference value and the second reference value based on the point to be determined. For example, dn = 1 means that the level of the neighboring sampling point is used to generate two reference values. Dn = 2 means that the level of the sampling point away from the current sampling point is used to generate two reference values. do. If the interval between sampling points used to generate the reference value is adjusted in this way, when the local peak noise signal exists in the edge signal, the dn value can be adjusted to a value greater than 1 to minimize the influence of the local peak noise. There is an advantage.

Meanwhile, when the two reference values are calculated as described above, the tag signal receiving apparatus 100 checks whether the two reference values satisfy a preset condition (S303). That is, it is checked whether the first reference value is less than or equal to 0 (dx_high <= 0) and the second reference value is greater than 0 (dx_low> 0). That is, the edge signal level at the sampling time point (the second time point) that is the current determination target is larger than the edge signal level at the previous sampling time point (the first time point), and the edge signal level at the next sampling time point (the third time point) is Check whether the signal level is less than or equal to the edge signal level at the current sampling time point (second time point).

When it is determined that the two reference values satisfy the preset condition, the tag signal receiving apparatus 100 may determine that the sampling point (second time point) has a peak point at which the slope of the edge signal changes from positive (+) to negative (-). It determines with (n), and produces | generates the edge information corresponding to a peak (S304). The edge clock corresponding to the peak of the edge signal is generated based on the generated edge information (S305). On the other hand, when the two reference values do not satisfy the preset condition, the above-described processes (S301 to S303) are repeatedly performed until the peak point is found.

Referring back to FIG. 5, the tag signal receiving apparatus 100 generates a data pulse whose level is changed from 0 to 1 or 1 to 0 whenever an edge clock is generated based on the edge clock, and the pulse of the generated data pulse. Bit data is determined based on the width (S105). For example, when the input tag signal is an FM0 signal, it is determined to be bit 0 if the pulse width of the data pulse is smaller than the reference pulse width, and bit 1 if it is wider than the reference pulse width. 11 illustrates an example in which the tag signal receiving apparatus 100 generates an edge clock from an edge signal and generates a data pulse (decoded data) based on the edge clock.

Referring back to FIG. 5, when bit data is determined, the tag signal receiving apparatus 100 detects the preamble of the tag signal by analyzing the bit data (S106). That is, a preamble including start information of specific data useful among tag signals is detected from the bit data, and tag data is detected based on the preamble.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a structural diagram showing a tag signal receiving apparatus according to an embodiment of the present invention.

2 is a structural diagram illustrating an offset signal remover according to an exemplary embodiment of the present invention.

3 is a structural diagram illustrating an edge signal generator according to an exemplary embodiment of the present invention.

4 is a structural diagram illustrating a data decoding unit according to an embodiment of the present invention.

5 is a flowchart illustrating a tag signal demodulating method of a tag signal receiving apparatus according to an exemplary embodiment of the present invention.

6 illustrates an example of a baseband tag signal input to a tag signal receiving apparatus according to an exemplary embodiment of the present invention.

7 illustrates an example of a tag signal from which a high frequency component, a noise component, and an offset distortion signal are removed according to an exemplary embodiment of the present invention.

8 is a flowchart illustrating a method of generating an edge signal of a tag signal receiving apparatus according to an exemplary embodiment of the present invention.

9 illustrates an example of a first edge signal and a second edge signal according to an embodiment of the present invention.

10 is a flowchart illustrating an edge clock generation method according to an embodiment of the present invention.

11 illustrates an example of an edge clock and a data pulse generated based on edge information according to an embodiment of the present invention.

Claims (10)

delete delete In the method of receiving a tag signal in a radio frequency identification reader, Removing an offset distortion signal from the received signal using a continuous tag signal average value calculated through a moving average filter from a signal received from a radio frequency identification tag; Generating an edge signal from the signal from which the offset distortion signal has been removed; Detecting edge information from the edge signal; And Determining bit data corresponding to a tag signal based on an edge clock generated from the edge information; Tag signal receiving method comprising a. The method of claim 3, Performing filtering to remove high frequency components and noise components from the received signal. More, The removing step, And removing the offset distortion signal from the filtered signal from which the high frequency component and the noise component are removed. The method of claim 3, The generating step, Generating a first edge signal from the signal from which the offset distortion signal is removed using a matched filter; And Generating the edge signal by removing a noise component of a specific level from the first edge signal. Tag signal receiving method comprising a. The method of claim 5, The received signal includes an I channel tag signal and a Q channel tag signal, And a coefficient of the matching filter is set equally to each of the I channel tag signal and the Q channel tag signal. The method of claim 3, The detecting step, Obtaining edge signal levels of successive first, second and third views; Calculating a first reference value based on the edge signal levels of the first time point and the second time point; Calculating a second reference value based on the second time point and the edge signal level of the second time point; Determining whether an edge signal at the second time point is a peak point based on the first reference value and the second reference value; And Detecting the edge information based on the edge signal of the second time point when the second time point is a peak point Tag signal receiving method comprising a. The method of claim 7, wherein The determining step, Generating the edge clock corresponding to the peak point based on the edge information; Generating a data pulse based on the edge clock; And Generating the bit data based on a pulse width of the data pulse Tag signal receiving method comprising a. A filter unit for outputting a signal from which a high frequency component and a noise component are removed from a signal received from a radio frequency identification tag; An offset signal removing unit outputting a signal from which an offset distortion signal is removed from the signal output from the filter unit; An edge signal generator for generating an edge signal from the signal output from the offset signal remover; An edge information detector for extracting edge information from the edge signal and generating an edge clock corresponding to the edge information; And A data decoding unit for determining bit data based on the edge clock and detecting the preamble based on the bit data Tag signal receiving apparatus comprising a. The method of claim 9, The offset signal removing unit, A moving average filter for calculating a continuous signal average value by filtering the signal output from the filter unit; A gain unit for adjusting and outputting a gain of the signal average value; And A subtractor for removing the offset distortion signal from the signal output from the filter unit using the signal output from the gain unit Tag signal receiving apparatus comprising a.

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