JP2020141315A - Wireless signal demodulating device, wireless signal demodulating program, and wireless signal demodulating method - Google Patents

Abstract

To provide a wireless signal demodulating device that suppresses false positives.SOLUTION: A wireless signal demodulation device includes a rising edge detection unit that detects a rising edge of the envelope of a wireless signal that is obtained by modulating frame data including a synchronization pattern and a plurality of symbols, a rising edge detection unit that detects the rising edge of the envelope, a first time difference acquisition unit that acquires a first time difference between the detected rising edge and the rising edge detected one symbol before the rising edge, a second time difference acquisition unit that acquires a second time difference between the detected falling and the raising detected next to the falling, and a data management unit that demodulates or discards wireless signals in units of sections corresponding to the frame data, demodulates a wireless signal of a section including a predetermined pattern when the envelope includes the predetermined pattern of the first time difference and the second time difference, and discards a wireless signal of a section not including the predetermined pattern when the envelope does not include the predetermined pattern.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radio signal demodulation device, a radio signal demodulation program, and a radio signal demodulation method.

Conventionally, an RFID (Radio Frequency Identifier) tag radio signal is obtained by sampling an ASK (Amplitude-Shift Keying) modulated reception signal to detect a rising edge and measuring the period from the rising edge detection to the next rising edge detection. There is a method for identifying (see, for example, Non-Patent Document 1).

2005 Ministry of Economy, Trade and Industry consignment project. Rationalization of energy use in 2005. Electronic tag system development research project. (Electronic tag demonstration experiment in the media content industry). report. March 2006. Japan Publishing Infrastructure Center, a limited liability intermediary corporation.

By the way, the packet length of the radio signal that the RFID tag responds to the reading signal of the RFID reader is as short as 7 symbols at the minimum, and it is not easy to distinguish it from other radio waves including noise and the like. Therefore, in the method of identifying based only on the period from the rising edge detection to the next rising edge detection as in the conventional reading method, the RFID reader may erroneously detect a signal other than the wireless signal as a wireless signal. Further, even if the signal is other than the radio signal of the RFID tag, the same false detection may occur if the packet length is short.

Therefore, it is an object of the present invention to provide a radio signal demodulation device, a radio signal demodulation program, and a radio signal demodulation method that suppress false detection.

The radio signal demodulator according to the embodiment of the present invention has a fall detection unit that detects the fall of the envelope of a radio signal in which frame data including a synchronization pattern and a plurality of symbols is modulated, and a fall detection unit that detects the rise of the envelope. The first time difference acquisition unit that acquires the first time difference between the rise detection unit, the rise detected by the rise detection unit, and the rise detected by the rise detection unit one symbol before the rise, and the above. The second time difference acquisition unit that acquires the second time difference between the falling edge detected by the falling edge detection unit and the rising edge detected by the rising edge detection unit after the falling edge, and the radio signal in the frame data. A data management unit that demodulates or discards in units of corresponding sections, and when the envelope contains predetermined patterns of the first time difference and the second time difference, demodulates the radio signal of the section including the predetermined patterns. A data management unit that discards a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern is included.

It is possible to provide a radio signal demodulation device, a radio signal demodulation program, and a radio signal demodulation method that suppress false detection.

It is a figure explaining the operation of the wireless signal demodulation apparatus 100 of embodiment. It is a hardware block diagram of the wireless signal demodulation apparatus 100 of embodiment. It is a figure which shows the synchronization pattern and PSDU included in the frame of the response signal of the RFID tag. It is a figure explaining the method of discriminating a pattern in a PIE method. It is a figure which shows two threshold values at the time of detecting the falling edge and the rising edge of the response signal of the RFID tag 10. It is a figure which shows the characteristic of the false detection probability with respect to a high threshold value HTH. It is a figure which shows the structure of the wireless signal demodulation apparatus 100 of embodiment. It is a figure which shows the characteristic of the discard rate with respect to a high threshold value HTH. It is a figure which shows the table data which associated with the SNR and the high threshold value HTH which gives the minimum value of the discard rate in each SNR. It is a figure which shows the flowchart which shows the process which the control device 110 of a wireless signal demodulation device 100 executes. It is a figure which shows the structure of the radio signal demodulation apparatus 100M of the modification of embodiment. It is a figure which shows the relationship between the discard rate and false detection probability with respect to a high threshold value HTH in a high sensitivity mode and a low sensitivity mode. It is a figure which shows the table data which associated the high-sensitivity mode and low-sensitivity mode with high threshold value HTH. It is a figure which shows the flowchart which shows the process which the control device 110M of a wireless signal demodulation device 100M executes.

Hereinafter, embodiments to which the radio signal demodulation device, the radio signal demodulation program, and the radio signal demodulation method of the present invention are applied will be described.

<Embodiment>
FIG. 1 is a diagram illustrating the operation of the wireless signal demodulation device 100 of the embodiment. The wireless signal demodulator 100 is, for example, an RFID reader that reads the RFID tag 10, distinguishes the response signal 10A of the RFID tag 10 from the signals other than the response signal 10A of the RFID tag 10, noise, and the like, and the RFID tag 10 The response signal 10A is demolished, and signals other than the response signal 10A of the RFID tag 10 and noise and the like are discarded. In the following, a system including the RFID tag 10 and the radio signal demodulation device 100 as an RFID reader will be referred to as an RFID system.

FIG. 1 shows, as an example, a state in which the radio signal demodulator 100 correctly discriminates between the radio wave 1A and the thermal noise 2 emitted by the Sigfox terminal 1 so as not to be erroneously detected as the response signal of the RFID tag 10.

The wireless signal demodulator 100 discards even if it receives the radio wave 1A and the thermal noise 2 emitted by the Sigfox terminal 1, demodulates the response signal 10A of the RFID tag 10, further decodes it, and reads the data (ID). ..

FIG. 2 is a hardware configuration diagram of the wireless signal demodulation device 100 of the embodiment. The radio signal demodulation device 100 executes the radio signal demodulation program of the embodiment. The method realized by the radio signal demodulation device 100 executing the radio signal demodulation program is the radio signal demodulation method of the embodiment.

The wireless signal demodulation device 100 includes a CPU (Central Processing Unit) 51, a memory 52, a display 53, a keyboard 54, an I / F (Interface) 55, and a bus 56. The CPU 51, the memory 52, the display 53, the keyboard 54, and the I / F 55 are connected to each other by the bus 56.

The CPU 51 realizes the radio signal demodulation method by reading and executing the radio signal demodulation program recorded in the memory 52.

The memory 52 includes a storage device such as an HDD (Hard Disk Drive), a volatile memory such as a RAM (Random Access Memory), and the like. The HDD stores a wireless signal demodulation program, data used by the CPU 51 when executing the wireless signal demodulation program, and the like. The RAM temporarily stores a wireless signal demodulation program executed by the CPU 51, data obtained when the wireless signal demodulation program is executed, and the like.

The display 53 is a display device that displays an image or the like used for operating the wireless signal demodulation device 100, and may be integrated with a touch panel.

The keyboard 54 is an input device used by the user when operating the wireless signal demodulation device 100. The I / F 55 is an external connection device for connecting the wireless signal demodulation device 100 and the external device.

FIG. 3 is a diagram showing a synchronization pattern and a PSDU (Physical Layer Convergence Protocol) included in a frame of a response signal of an RFID tag. Here, as an example, the synchronization pattern and PSDU included in the response signal of the RFID tag according to version 2.0.1 of EPC Gen2 are shown. Since the RFID system adopts the PIE method (Pulse Interval. Encoding), the synchronization pattern and PSDU shown in FIG. 3 conform to the PIE method.

FIG. 3A shows a Frame-Sync pulse signal as a synchronization pattern. Frame-Sync includes three sections: delimiter, data-0, R => T calibration (RTcal). The length of the pulse signal in the three sections is the length of three symbols. Frame-Sync is placed at the beginning of the frame.

The Delimiter is an L (Low) level section of a predetermined length (fixed length), and the length is set to a unique length of 12.5 μs ± 5% by version 2.0.1 of EPC Gen2. .. The length of data-0 is 1 Tari (type A reference interval), and the length of R => T calibration is determined to be 2.5 Tari or more and 3.0 Tari or less. Both data-0 and R => T calibration include L-level PW (Pulse Width) sections. The lengths of the PW sections of data-0 and R => T calibration are equal.

The PSDU shown in FIG. 3B is a part of the frame of the response signal of the RFID tag other than Frame-Sync, and may include a code and data, or may include only a code. The PSDU is placed after Frame-Sync in the frame. The length of the pulse signal of the PSDU is at least 4 symbols. Therefore, the total length of Frame-Sync and PSDU is at least 7 symbols.

FIG. 3B shows four symbols in the sequence of “1”, “0”, “0”, and “1” as an example. The symbols "0" and "1" both include one PW section, and "0" and "1" can be distinguished by different lengths of sections other than the PW section.

Here, the pulse signal for one symbol is represented by a section including one PW section (L level section) in which the pulse drops in the RFID system adopting the PIE method, and the pulse becomes H level at the beginning of the section. It is the time of rising, and the end of the section is the time of the end of the PW section (the time of transition from L level to H level).

FIG. 4 is a diagram illustrating a pattern discrimination method in the PIE method. FIG. 4 shows, as an example, pulse signals representing the four symbols “1”, “0”, “0”, and “1”. Further, FIG. 4 shows a pattern discrimination method in Non-Patent Document 1 for comparison, in addition to the pattern discrimination method according to the embodiment. Hereinafter, the pattern discrimination method in Non-Patent Document 1 will be referred to as a pattern discrimination method of a known example.

Here, in order to make it easier to understand the pattern discrimination method, a method of detecting the falling edge and the rising edge using a pulse signal to obtain the time difference A and B will be described, but in reality, the falling edge is described from the envelope before demodulation. The rise will be detected.

The pattern discrimination method of the known example is to detect only the rising timing indicated by the white triangle (Δ) and to arrange the time difference A between adjacent rising edges (a pattern in which a plurality of time differences A are arranged in chronological order). ), It is determined whether or not it is a response signal of the RFID system.

In the pattern determination method of the embodiment, in addition to the order of the time difference A between adjacent rising edges according to the pattern discrimination method of the known example, the falling edge timing indicated by the black triangle (▲) is detected. , The order of arrangement of the time difference B from the falling edge to the next rising edge (a pattern in which a plurality of time difference Bs are arranged in chronological order) is used to determine whether or not the signal is a response signal of the RFID system.

FIG. 5 is a diagram showing two threshold values for detecting the falling edge and the rising edge of the response signal of the RFID tag 10. The response signal shown in FIG. 5 is an example of a wireless signal.

Here, the falling edge and the rising edge of the response signal of the RFID tag 10 are detected using two threshold values. The higher of the two thresholds is the high threshold HTH, which is an example of the first threshold. The lower of the two thresholds is the low threshold LTH, which is an example of the second threshold. The low-threshold LTH and the high-threshold HTH described here have a relationship of LTH = 1-HTH as an example, but it is not necessary to have such a relationship.

The radio signal demodulator 100 detects the falling edge of the response signal when the level of the response signal changes from the high threshold value HTH or more to the low threshold value LTH or less. Further, the radio signal demodulation device 100 detects the rise of the response signal when the level of the response signal changes from the high / low threshold value LTH or less to the threshold value HTH or more.

The time differences A and B shown in FIG. 4 are actually obtained by detecting the falling edge and the rising edge of the envelope using the low threshold value LTH and the high threshold value HTH as shown in FIG.

FIG. 6 is a diagram showing the characteristics of the false positive probability with respect to the high threshold HTH. In FIG. 6, the horizontal axis represents the high threshold HTH and the vertical axis represents the false positive probability. The false detection probability is a probability that the wireless signal demodulator 100, which is an RFID reader, erroneously detects a signal other than the response signal of the RFID tag 10 as the response signal of the RFID tag 10.

The false detection probability was observed at 1 Msps (Megasamples per second) under the condition that the radio signal demodulator 100 receives the signal once every 10 milliseconds. The characteristics were created by selecting the value of the minimum false positive probability obtained at each SNR with an emphasis on reception sensitivity.

In FIG. 6, for comparison, the false detection probability in the pattern discrimination method of a known example is shown by a broken line.

In the method of a known example, when the high threshold HTH is 0.7, the false detection probability is about 5 × ^10-6 , and when converted into a numerical value when the radio signal demodulator 100 receives radio waves continuously for one hour, It will be about 1.4 times / hour. That is, if the radio wave is received for one hour, erroneous detection will occur one or more times. This is a value that can be said to have many false positives.

On the other hand, in the method of the embodiment (solid line), since the time difference B is seen in addition to the time difference A, the false detection probability is about 8 × 10 ^-7 when the high threshold HTH is 0.7. When converted into a numerical value when the radio signal demodulator 100 receives radio waves continuously for one hour, it is about 0.25 times / hour. This is about 1/6 of the probability in the case of the method of the known example, and it can be seen that it can be sufficiently reduced.

FIG. 7 is a diagram showing the configuration of the wireless signal demodulation device 100 of the embodiment. The radio signal demodulation device 100 includes an antenna 101, a control device 110, a display 120, and an operation unit 130. The display 120 corresponds to the display 53 of FIG. 2, and the operation unit 130 corresponds to the keyboard 54 of FIG. In addition to the keyboard 54, the operation unit 130 may include a touch panel integrated with the keyboard 54 and the display 120 of FIG. 2, or may include other input devices such as a mouse.

The control device 110 includes a main control unit 111, an IQ output unit 112A, an envelope calculation unit 112B, a fall detection unit 113D, a rise detection unit 113U, a time difference acquisition unit 114A, 114B, an SNR acquisition unit 115, a threshold setting unit 116, and data management. It has a unit 117, a data analysis unit 118, and a memory 119.

Main control unit 111, IQ output unit 112A, envelope calculation unit 112B, fall detection unit 113D, rise detection unit 113U, time difference acquisition unit 114A, 114B, SNR acquisition unit 115, threshold setting unit 116, data management unit 117, data analysis The unit 118 represents the function of the control device 110 that executes the radio signal demodulation program. Further, the memory 119 functionally represents the memory 52 (see FIG. 2).

The main control unit 111 is a processing unit that controls the processing of the wireless signal demodulation device 100, and is an IQ output unit 112A, an envelope calculation unit 112B, a fall detection unit 113D, a rise detection unit 113U, a time difference acquisition unit 114A, 114B, and SNR. A process other than the processes performed by the acquisition unit 115, the threshold value setting unit 116, the data management unit 117, and the data analysis unit 118 is executed.

The IQ output unit 112A is connected to the antenna 101, acquires the I value and the Q value representing the amplitude and phase of the response signal of the RFID tag 10 that has received the read signal radiated from the antenna 101, and acquires the I value and the Q value, and the envelope calculation unit 112B. Output to.

The envelope calculation unit 112B calculates the envelope (envelope) of the response signal of the RFID tag 10 based on the I value and the Q value input from the IQ output unit 112A. More specifically, the envelope calculation unit 112B arranges the amplitude of the response signal obtained from the I value and the Q value input from the IQ output unit 112A in chronological order to form the envelope (envelope) of the response signal. Calculate. This is because the envelope is a time-series arrangement of the amplitudes of the response signals. The envelope calculation unit 112B outputs the envelope (envelope) of the response signal to the falling detection unit 113D, the rising detection unit 113U, and the SNR acquisition unit 115.

The fall detection unit 113D detects the fall from the envelope of the response signal input from the envelope calculation unit 112B by using the two threshold values shown in FIG. 5, and also detects the time when the fall occurs. The fall detection unit 113D outputs the time when the fall occurs to the time difference acquisition unit 114B, and outputs the time when the fall occurs and the time when the fall occurs to the data management unit 117.

The rise detection unit 113U detects the rise from the envelope of the response signal input from the envelope calculation unit 112B by using the two threshold values shown in FIG. 5, and also detects the time when the rise occurs. The rise detection unit 113U outputs the time when the rise occurs to the time difference acquisition units 114A and 114B, and outputs the time when the rise occurs and the time when the rise occurs to the data management unit 117.

The time difference acquisition unit 114A acquires the time difference between the rise time input from the rise detection unit 113U and the previous rise time input from the rise detection unit 113U. Since this time difference corresponds to the time difference A shown in FIG. 4, it will be described below as the time difference A. The time difference acquisition unit 114A outputs data representing the time difference A to the data management unit 117.

The time of the previous rise corresponds to the time of the rise one symbol before the time of the rise input from the rise detection unit 113U at the present time. The time difference acquisition unit 114A is an example of the first time difference acquisition unit, and the time difference A is an example of the first time difference.

The time difference acquisition unit 114B acquires the time difference between the fall time input from the fall detection unit 113D and the rise time input from the rise detection unit 113U thereafter. The rise time input from the rise detection unit 113U is the rise time of the envelope that first occurs after the fall of the envelope occurs.

Since the time difference acquired by the time difference acquisition unit 114B corresponds to the time difference B shown in FIG. 4, it will be described below as the time difference B. The time difference acquisition unit 114B outputs data representing the time difference B to the data management unit 117. The time difference acquisition unit 114B is an example of the second time difference acquisition unit, and the time difference B is an example of the second time difference.

The SNR acquisition unit 115 acquires (obtains) the SNR (Signal to Noise Ratio) based on the noise level stored in the memory 119 and the envelope of the response signal input from the envelope calculation unit 112B. .. The SNR acquisition unit 115 outputs the SNR to the threshold value setting unit 116.

The SNR acquisition unit 115 holds the envelope of the response signal input from the envelope calculation unit 112B as an example, and corresponds to each frame based on the time indicating the timing of switching the frame input from the data management unit 117. The SNR is calculated by dividing the maximum value of the envelope of the interval by the noise level.

If the time representing the timing of frame switching is known, the section of the envelope corresponding to each frame (the section corresponding to one frame) can be known. Therefore, the SNR acquisition unit 115 sets the maximum envelope in the section of the envelope corresponding to each frame. The value can be calculated.

The threshold value setting unit 116 reads the optimum high threshold value HTH from the memory 119 using the SNR input from the SNR acquisition unit 115, and sets the high threshold value HTH and the low threshold value LTH in the fall detection unit 113D and the rise detection unit 113U. .. The low threshold LTH can be determined by 1-HTH using the read high threshold HTH.

The memory 119 has table data for storing the optimum high threshold HTH according to the SNR. This table data is table data that stores a combination of SNR and high threshold HTH for minimizing the discard rate.

Data indicating that a fall has occurred from the fall detection unit 113D and data indicating the time when the fall has occurred are input to the data management unit 117, and a rise has occurred from the rise detection unit 113U. Data representing the time when the rise occurred and data representing the time when the rise occurred are input.

Further, in the data management unit 117, data representing the time difference A is input from the time difference acquisition unit 114A, and data representing the time difference B is input from the time difference acquisition unit 114B.

The data management unit 117 identifies a pattern in which the fall and rise of the envelope occur in time series based on the data representing the time when the fall and rise occur and the data representing the time difference A and the time difference B. , Determine if the envelope is that of the response signal of RFID tag 10.

The data management unit 117 identifies Frame-Sync and PSDU based on the patterns of time difference A and time difference B, and identifies the beginning of the frame based on Frame-Sync. That is, the data management unit 117 can identify the start position and the end position of the frame based on Frame-Sync. The start position and end position of the frame are the switching positions of the frame.

If the envelope includes the predetermined patterns of the time difference A and the time difference B, the data management unit 117 determines that the envelope belongs to the response signal of the RFID tag 10, and demodulates the response signal of the section including the predetermined pattern. .. Further, when the envelope does not include the predetermined pattern, the data management unit 117 determines that the envelope does not belong to the response signal of the RFID tag 10, and discards the response signal in the section that does not include the predetermined pattern.

The predetermined pattern is a pattern of time difference A and time difference B indicating that it is a response signal of the RFID system.

Further, the data management unit 117 outputs data representing the time representing the timing of frame switching to the SNR acquisition unit 115.

The data analysis unit 118 decodes the response signal demodulated by the data management unit 117, and acquires the digital data contained in the PSDU.

In the memory 119, in addition to the data used in executing the radio signal demodulation program and the radio signal demodulation program, the data shown in FIG. 9 described later (table data storing the optimum high threshold HTH according to the SNR) is stored in the memory 119. Store. The memory 119 is an example of a first data holding unit, a second data holding unit, and a third data holding unit.

FIG. 8 is a diagram showing the characteristics of the discard rate with respect to the high threshold HTH. The discard rate characteristics for high threshold HTH are determined for multiple levels of SNR (10 dB, 13 dB, 15 dB, 18 dB, 20 dB). The characteristics shown in FIG. 8 are obtained by simulation. The discard rate is a probability (ratio) of discarding a section corresponding to one frame in the envelope of the radio wave received by the radio signal demodulation device 100.

When the high threshold HTH is changed as shown in FIG. 8, the discard rate takes a minimum value at a certain high threshold HTH. The high threshold HTH when taking the minimum value changes depending on the SNR. In FIG. 8, the minimum value in the characteristic of the discard rate at each SNR is circled (◯). It is considered that the reason why the discard rate changes depending on the SNR in this way is that there is an optimum high threshold HTH in each SNR.

Therefore, the wireless signal demodulation device 100 stores the table data shown in FIG. 9 in the memory 119. FIG. 9 is a diagram showing table data in which the SNR and the high threshold HTH that gives the minimum value of the discard rate in each SNR are associated with each other. The minimum values of the discard rate when the SNR is 10 dB, 13 dB, 15 dB, 18 dB, and 20 dB are 0.75, 0.7, 0.65, 0.6, and 0.6, respectively. If the high threshold value HTH is set according to the SNR using such table data, the discard rate can be minimized and the reception sensitivity can be improved.

FIG. 10 is a diagram showing a flowchart showing a process executed by the control device 110 of the wireless signal demodulation device 100.

When the process starts, the IQ output unit 112A acquires the I value and the Q value from the response signal of the RFID tag 10 and outputs them to the envelope calculation unit 112B (step S1).

The envelope calculation unit 112B obtains data representing the envelope of the response signal of the RFID tag 10 (data representing the waveform of the envelope) based on the I value and the Q value, and the fall detection unit 113D, the rise detection unit 113U, and the SNR acquisition unit. Output to 115 (step S2).

The SNR acquisition unit 115 acquires the SNR based on the noise level stored in the memory 119 and the envelope of the response signal input from the envelope calculation unit 112B, and outputs the SNR to the threshold value setting unit 116 (step S3). As an example, the SNR acquisition unit 115 may output the SNR obtained by rounding off the value of the first decimal place of the acquired SNR to the threshold value setting unit 116.

The threshold value setting unit 116 reads the optimum high threshold value HTH from the memory 119 using the SNR input from the SNR acquisition unit 115, and sets the high threshold value HTH and the low threshold value LTH in the fall detection unit 113D and the rise detection unit 113U. (Step S4).

The main control unit 111 determines whether or not a fall is detected by the fall detection unit 113D (step S5).

When the main control unit 111 determines that the fall detection unit 113D has not detected the fall (S5: NO), the main control unit 111 causes the fall detection unit 113D to detect the fall (step S6).

When the main control unit 111 finishes the process of step S6, the main control unit 111 returns the flow to step S5.

When the main control unit 111 determines in step S5 that a fall is detected by the fall detection unit 113D (S5: YES), it determines whether or not a rise is detected by the rise detection unit 113U (step S7). ).

When the main control unit 111 determines that the rise detection unit 113U has not detected the rise (S7: NO), the main control unit 111 causes the rise detection unit 113U to detect the rise (step S8).

When the main control unit 111 finishes the process of step S8, the main control unit 111 returns the flow to step S5. After the flow returns from steps S8 to S5, the flow proceeds from steps S5 to S7. This is because the fall has already been detected.

When the main control unit 111 determines in step S7 that the rise is detected by the rise detection unit 113U (S7: YES), the main control unit 111 advances the flow to step S9. Steps S5 to S8 are loop processes that are repeated until continuous falling edges and rising edges are detected.

The time difference acquisition unit 114A acquires the time difference A between the rise time input from the rise detection unit 113U and the previous rise time input from the rise detection unit 113U (step S9).

The time difference acquisition unit 114B acquires the time difference B between the fall time input from the fall detection unit 113D and the rise time input from the rise detection unit 113U after that (step S10).

The data management unit 117 determines whether or not the time difference A acquired by the time difference acquisition unit 114A is a normal time difference (step S11). The normal time difference for the time difference A is a predetermined time difference defined for the time difference A for the response signal of the RFID system, and has a width (plus or minus width) due to a predetermined margin. The data management unit 117 determines that the time difference A is normal if the time difference A acquired by the time difference acquisition unit 114A is within a predetermined time difference range.

When the data management unit 117 determines that the time difference A is normal (S11: YES), the data management unit 117 determines whether or not the time difference B acquired by the time difference acquisition unit 114B is a normal time difference (step S12). The normal time difference for the time difference B is a predetermined time difference determined for the time difference B for the response signal of the RFID system, and has a width (plus or minus width) due to a predetermined margin. The data management unit 117 determines that the time difference B is normal if the time difference B acquired by the time difference acquisition unit 114B is within a predetermined time difference range.

When the data management unit 117 determines that the time difference B is normal (S12: YES), the data management unit 117 demodulates the response signal in the section where the time difference A and B are determined to be normal (step S13).

The data analysis unit 118 decodes the response signal demodulated by the data management unit 117, and acquires the digital data contained in the PSDU (step S14).

On the other hand, if the data management unit 117 determines in step S11 that the time difference A is not normal (S11: NO), or if it determines in step S12 that the time difference B is not normal (S12: NO), the time difference The response signal in the section where A or B is determined to be abnormal is discarded (step S15).

When the main control unit 111 finishes the process of step S14 or S15, it finishes a series of processes (END).

As described above, in the wireless signal demodulation device 100 of the embodiment, in addition to the pattern in which the time difference A between adjacent rising edges is arranged in chronological order, the time difference B from the falling edge to the next rising edge is arranged in chronological order. The arranged pattern is used to determine if it is a response signal of an RFID system. If it is determined whether or not it is a response signal of the RFID system by using both the time difference A and the time difference B, the determination accuracy can be significantly improved as compared with the case where the determination is made only by the time difference A. This is because the time difference A alone may be indistinguishable from signals other than the response signal of the RFID system, noise, and the like.

In the simulation, if it is determined whether or not it is the response signal of the RFID system by using both the time difference A and the time difference B, the false detection probability is reduced to about 1/6 as compared with the case where the determination is based only on the time difference A. I was able to confirm that.

Therefore, it is possible to provide a radio signal demodulation device 100, a radio signal demodulation program, and a radio signal demodulation method that suppress false detection.

Further, by setting the high threshold value HTH and the low threshold value LTH to appropriate values, the discard rate can be reduced and the reception sensitivity of the RFID tag 10 can be improved.

In the above description, the mode for discriminating between the response signal of the RFID system and other signals, noise and the like has been described, but the present invention is not limited to the response signal of the RFID system. In particular, if the signal has a short data length, it may be erroneously detected as noise or the like. Therefore, such a signal may be discriminated from other signals and noise or the like.

Further, although the wireless signal demodulation device 100 has been described above, for example, if the horizontal axis is set to the frequency and the vertical axis is set to the radio wave intensity, and the frequency distribution of the radio wave intensity of the response signal of the RFID tag 10 is displayed on the display 120 The distribution of the response signal can be visualized. In such a case, the radio signal demodulation device 100 can be regarded as a radio wave visualization device. In addition to the response signal of the RFID tag 10, the radio wave visualization device has a frequency of all or any of BLE (Bluetooth Low Energy (registered trademark)), WiFi (registered trademark), and Bluetooth (registered trademark), for example. The distribution may be displayed on the display 120. By making the display color of each radio wave different, it is possible to visualize the distribution of a plurality of types of radio waves. Such a radio wave visualization device executes a radio wave visualization program to realize a radio wave visualization method.

Further, in step S4 of the flow, the threshold setting unit 116 reads the optimum high threshold HTH from the table data shown in FIG. 9, and applies the high threshold HTH and the low threshold LTH to the falling detection unit 113D and the rising detection unit 113U. The setting form has been described.

However, it is not necessary for the threshold value setting unit 116 to set the high threshold value HTH and the low threshold value LTH in the fall detection unit 113D and the rise detection unit 113U in this way. In this case, for example, predetermined high threshold value HTH and low threshold value LTH may be set in advance in the fall detection unit 113D and the rise detection unit 113U, or may be set to the values selected by the user. Good.

Further, the user may be able to select a mode for setting a high threshold value HTH and a low threshold value LTH.

FIG. 11 is a diagram showing a configuration of a radio signal demodulation device 100M of a modified example of the embodiment. In the following, the same components as those of the radio signal demodulation device 100 shown in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted.

The radio signal demodulation device 100M includes an antenna 101, a control device 110M, a display 120, and an operation unit 130. The wireless signal demodulator 100M executes a dedicated application program in order to allow the user to select a mode for setting a high threshold HTH and a low threshold LTH, and displays a GUI (Graphic User Interface) on a display 120 with a touch panel. Display the image of the button by.

The control device 110M includes a main control unit 111M, an IQ output unit 112A, an envelope calculation unit 112B, a fall detection unit 113D, a rise detection unit 113U, a time difference acquisition unit 114A, 114B, an input reception unit 115M, a threshold setting unit 116M, and data management. It has a unit 117, a data analysis unit 118, and a memory 119M.

Main control unit 111M, IQ output unit 112A, envelope calculation unit 112B, fall detection unit 113D, rise detection unit 113U, time difference acquisition unit 114A, 114B, input reception unit 115M, threshold setting unit 116M, data management unit 117, data analysis Section 118 represents the function of the control device 110M that executes the radio signal demodulation program. Further, the memory 119M functionally represents the memory 52 (see FIG. 2).

The main control unit 111M is a processing unit that controls the processing of the radio signal demodulation device 100M, and includes IQ output unit 112A, envelope calculation unit 112B, fall detection unit 113D, rise detection unit 113U, time difference acquisition units 114A and 114B, and inputs. Processes other than those performed by the reception unit 115M, the threshold value setting unit 116M, the data management unit 117, and the data analysis unit 118 are executed.

Further, the main control unit 111M executes an application program and performs a process of displaying an image of a GUI button or the like on a display 120 with a touch panel.

The input reception unit 115M receives a command input by the user of the wireless signal demodulation device 100M via the operation unit 130. The content of the command received by the input receiving unit 115M is input to the threshold value setting unit 116M via the main control unit 111M. Here, the command input by the user is, for example, a command for selecting a mode (high sensitivity mode or low sensitivity mode) for setting the values of the high threshold value HTH and the low threshold value LTH.

The threshold setting unit 116M reads the high threshold HTH corresponding to the mode (high sensitivity mode or low sensitivity mode) input from the input reception unit 115M from the memory 119M, and causes the falling detection unit 113D and the rising detection unit 113U to read the high threshold HTH. And set a low threshold LTH. The low threshold LTH can be determined by 1-HTH using the read high threshold HTH.

The memory 119M stores table data for storing a high threshold HTH in a high-sensitivity mode or a low-sensitivity mode, in addition to data used in executing the radio signal demodulation program and the radio signal demodulation program.

FIG. 12 is a diagram showing the relationship between the discard rate and the false positive probability with respect to the high threshold value HTH in the high sensitivity mode and the low sensitivity mode.

The characteristics of the discard rate with respect to the high threshold HTH shown in FIG. 12 (A) are the same as the characteristics shown in FIG. The high-sensitivity mode is a mode in which even a signal having a relatively small SNR is set to a high threshold value HTH in which the rate of demodulation is relatively high (the discard rate is relatively low). The low-sensitivity mode is a mode in which the rate of demodulating a signal having a relatively small SNR is not relatively high (relatively low (the discard rate is relatively high)) and the high threshold value HTH is set. The low sensitivity mode is an example of the first mode, and the high sensitivity mode is an example of the second mode.

Here, as an example, whether or not the demodulation rate is relatively high is determined by whether or not the discard rate is less than 10% (the probability of demodulation is 90% or more). Further, in the high sensitivity mode, the high threshold value HTH is set to 0.7, and in the low sensitivity mode, the high threshold value HTH is set to 0.6.

When the high threshold HTH is 0.7, the SNR is 13 dB and the discard rate is about 10%. Therefore, if the SNR is 13 dB or more, demodulation can be performed. That is, in the high sensitivity mode, demodulation is possible even at around 13 dB and 15 dB, which have a relatively low SNR.

On the other hand, when the high threshold HTH is 0.6, the discard rate is about 90% when the SNR is 13 dB, the discard rate is about 30% when the SNR is 13 dB, and the discard rate is when the SNR is 15 dB. Is about 9%, so in the low sensitivity mode, the SNR must be 15 dB or more to be sufficiently demodulated.

Further, as shown in FIG. 12B, when the high-sensitivity mode having a high threshold HTH of 0.7 and the low-sensitivity mode having a high threshold HTH of 0.6 are compared, the low-sensitivity mode has a false detection probability. It can be seen that the false detection probability is low.

As described above, the discard rate and the false detection probability are in a contradictory relationship, and the user may decide to set the high threshold value HTH depending on the usage of the user of the wireless signal demodulation device 100M and the like. Based on this idea, the wireless signal demodulator 100M allows the user to select a high-sensitivity mode or a low-sensitivity mode.

FIG. 13 is a diagram showing table data in which the high-sensitivity mode and the low-sensitivity mode are associated with the high threshold value HTH. As shown in FIG. 13, the high threshold HTH is set to 0.7 in the high sensitivity mode, and the high threshold HTH is set to 0.6 in the low sensitivity mode.

FIG. 14 is a diagram showing a flowchart showing a process executed by the control device 110M of the wireless signal demodulation device 100M.

When the process starts, the main control unit 111M executes the application program and displays the image of the GUI button or the like on the display 120 with the touch panel (step S01M).

The input reception unit 115M receives a command input by the user of the wireless signal demodulation device 100M via the operation unit 130 (step S02M). The command input by the user is a command indicating whether to set the high sensitivity mode or the low sensitivity mode.

The threshold setting unit 116M reads the high threshold HTH corresponding to the mode (high sensitivity mode or low sensitivity mode) input from the input reception unit 115M from the memory 119M, and causes the falling detection unit 113D and the rising detection unit 113U to read the high threshold HTH. And the low threshold LTH is set (step S03M).
The IQ output unit 112A acquires the I value and the Q value from the response signal of the RFID tag 10 and outputs them to the envelope calculation unit 112B (step S1).

The envelope calculation unit 112B calculates the envelope of the response signal of the RFID tag 10 based on the I value and the Q value, and outputs the envelope to the falling detection unit 113D and the rising detection unit 113U (step S2M).

Hereinafter, the same processing as in steps S5 to S15 of FIG. 10 is performed.

Then, when the process of step S14 or S15 is completed, the main control unit 111M ends the application program and ends a series of processes (END).

As described above, in the radio signal demodulation device 100M of the modified example of the embodiment, in addition to the pattern in which the time difference A between adjacent rising edges is arranged in chronological order, the time difference B from the falling edge to the next rising edge is time. A pattern arranged in series is used to determine whether or not it is a response signal of an RFID system.

Therefore, the false detection probability can be reduced to about 1/6 as compared with the case where the determination is made based only on the time difference A.

Therefore, it is possible to provide a radio signal demodulation device 100M that suppresses erroneous detection, a radio signal demodulation program, and a radio signal demodulation method.

Further, since the wireless signal demodulator 100M displays a GUI button for selecting a high-sensitivity mode or a low-sensitivity mode on the display 120 by executing an application program, the user can easily select a mode according to his / her own use. You can choose.

In the above, the mode in which the high threshold value HTH is set to 0.7 in the high sensitivity mode and the high threshold value HTH is set to 0.6 in the low sensitivity mode has been described, but the present invention is not limited to these values. It may be possible to set the value obtained by the user in the simulation.

Further, in the above, the rate of demodulating even a signal having a relatively small SNR is relatively high, and the high sensitivity mode having a relatively high false detection probability and the rate of demodulating a signal having a relatively small SNR are relatively low, and the false detection probability The mode that allows the user to select a low-sensitivity mode with a low probability has been described.

However, the user may be allowed to select whether to prioritize the discard rate or the false positive probability. If the user selects a mode in which the low discard rate is prioritized, the radio signal demodulator 100M may be set to the high sensitivity mode. Further, if the user selects a mode that prioritizes the low probability of false detection, the radio signal demodulator 100M may be set to the low sensitivity mode.

Although the radio signal demodulation device, the radio signal demodulation program, and the radio signal demodulation method of the exemplary embodiment of the present invention have been described above, the present invention is limited to the specifically disclosed embodiments. Instead, various modifications and changes can be made without departing from the scope of claims.

The following additional notes will be further disclosed with respect to the above embodiments.
(Appendix 1)
A falling edge detection unit that detects the falling edge of the envelope of a radio signal modulated with frame data including a synchronization pattern and a plurality of symbols,
A rise detection unit that detects the rise of the envelope, and
A first time difference acquisition unit that acquires the first time difference between the rise detected by the rise detection unit and the rise detected by the rise detection unit one symbol before the rise.
A second time difference acquisition unit that acquires a second time difference between the fall detected by the fall detection unit and the rise detected by the rise detection unit next to the fall.
A data management unit that demodulates or discards the radio signal in section units corresponding to the frame data, and includes the predetermined pattern when the envelope includes the predetermined patterns of the first time difference and the second time difference. A radio signal demodulation device including a data management unit that demodulates a radio signal in a section and discards a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern.
(Appendix 2)
The falling edge detecting unit and the rising edge detecting unit further include a threshold value setting unit that sets a first threshold value used for detecting the falling edge and the rising edge and a second threshold value lower than the first threshold value.
The fall detection unit detects the fall when the level of the envelope changes from the first threshold value or more to the second threshold value or less.
The radio signal demodulation device according to Appendix 1, wherein the rise detection unit detects the rise when the level of the envelope becomes from the second threshold value or less to the first threshold value or more.
(Appendix 3)
A first data holding unit that holds noise level data representing the noise level of the receiving system including the antenna that receives the radio signal, and a first data holding unit.
A third that holds table data representing the first threshold value or the second threshold value at which the ratio at which the radio signal is discarded is minimized at each of the plurality of signal noise ratios of the plurality of signal levels of the radio signal with respect to the noise level. Including 2 data holding parts
The threshold value setting unit reads out the first threshold value or the second threshold value corresponding to the signal noise ratio of the signal level of the radio signal received by the receiving system to the noise level in the table data, and the read-out first threshold value. The radio signal demodulator according to Appendix 2, wherein the first threshold value and the second threshold value are set using one threshold value or the second threshold value.
(Appendix 4)
The first mode in which the first threshold value is relatively small, the rate of false detection of the radio signal is relatively low, and the rate at which the radio signal is discarded is the first predetermined rate, and the first mode is higher than that of the first mode. A third data holding unit that holds data indicating that the threshold value is large, the rate of false detection of the radio signal is higher than that of the first mode, and the rate of discarding the radio signal is the second mode having a second predetermined rate. When,
Further including an operation receiving unit that accepts an operation for selecting the first mode or the second mode.
The radio signal demodulation according to Appendix 2, wherein the threshold value setting unit sets the first threshold value and the second threshold value using the first threshold value of the first mode or the second mode received by the operation reception unit. apparatus.
(Appendix 5)
Detecting the falling edge of the envelope of a radio signal modulated with frame data containing a synchronization pattern and multiple symbols,
Detecting the rise of the envelope and
Acquiring the first time difference between the rise detected by detecting the rise of the envelope and the rise detected by detecting the rise of the envelope one symbol before the rise.
Acquiring the second time difference between the falling edge detected by detecting the falling edge of the envelope and the rising edge detected by detecting the falling edge of the envelope after the falling edge.
It is to demodulate or discard the radio signal in the section unit corresponding to the frame data, and when the envelope includes the predetermined patterns of the first time difference and the second time difference, the section including the predetermined pattern. A radio signal demodulation program that causes a computer to perform a process including demodulating a radio signal and discarding a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern.
(Appendix 6)
Detecting the falling edge of the envelope of a radio signal modulated with frame data containing a synchronization pattern and multiple symbols,
Detecting the rise of the envelope and
Acquiring the first time difference between the rise detected by detecting the rise of the envelope and the rise detected by detecting the rise of the envelope one symbol before the rise.
Acquiring the second time difference between the falling edge detected by detecting the falling edge of the envelope and the rising edge detected by detecting the falling edge of the envelope after the falling edge.
It is to demodulate or discard the radio signal in the section unit corresponding to the frame data, and when the envelope includes the predetermined patterns of the first time difference and the second time difference, the section including the predetermined pattern. A method for demodulating a radio signal, which comprises demodulating a radio signal and discarding a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern.

10 RFID tag 100, 100M Wireless signal demodulator 101 Antenna 110, 110M Control device 113D Fall detection unit 113U Rise detection unit 114A, 114B Time difference acquisition unit 115M Input reception unit 116, 116M Threshold setting unit 117 Data management unit

Claims (6)

A falling edge detection unit that detects the falling edge of the envelope of a radio signal modulated with frame data including a synchronization pattern and a plurality of symbols,
A rise detection unit that detects the rise of the envelope, and
A first time difference acquisition unit that acquires the first time difference between the rise detected by the rise detection unit and the rise detected by the rise detection unit one symbol before the rise.
A second time difference acquisition unit that acquires a second time difference between the fall detected by the fall detection unit and the rise detected by the rise detection unit next to the fall.
A data management unit that demodulates or discards the radio signal in section units corresponding to the frame data, and includes the predetermined pattern when the envelope includes the predetermined patterns of the first time difference and the second time difference. A radio signal demodulation device including a data management unit that demodulates a radio signal in a section and discards a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern. The falling edge detecting unit and the rising edge detecting unit further include a threshold value setting unit that sets a first threshold value used for detecting the falling edge and the rising edge and a second threshold value lower than the first threshold value.
The fall detection unit detects the fall when the level of the envelope changes from the first threshold value or more to the second threshold value or less.
The radio signal demodulation device according to claim 1, wherein the rise detection unit detects the rise when the level of the envelope becomes from the second threshold value or less to the first threshold value or more. A first data holding unit that holds noise level data representing the noise level of the receiving system including the antenna that receives the radio signal, and a first data holding unit.
A third that holds table data representing the first threshold value or the second threshold value at which the ratio at which the radio signal is discarded is minimized at each of the plurality of signal noise ratios of the plurality of signal levels of the radio signal with respect to the noise level. Including 2 data holding parts
The threshold value setting unit reads out the first threshold value or the second threshold value corresponding to the signal noise ratio of the signal level of the radio signal received by the receiving system to the noise level in the table data, and the read-out first threshold value. The radio signal demodulator according to claim 2, wherein the first threshold value and the second threshold value are set using one threshold value or the second threshold value. The first mode in which the first threshold value is relatively small, the rate of false detection of the radio signal is relatively low, and the rate at which the radio signal is discarded is the first predetermined rate, and the first mode is higher than that of the first mode. A third data holding unit that holds data indicating that the threshold value is large, the rate of false detection of the radio signal is higher than that of the first mode, and the rate of discarding the radio signal is the second mode having a second predetermined rate. When,
Further including an operation receiving unit that accepts an operation for selecting the first mode or the second mode.
The radio signal according to claim 2, wherein the threshold value setting unit sets the first threshold value and the second threshold value using the first threshold value of the first mode or the second mode received by the operation reception unit. Demodulator. Detecting the falling edge of the envelope of a radio signal modulated with frame data containing a synchronization pattern and multiple symbols,
Detecting the rise of the envelope and
Acquiring the first time difference between the rise detected by detecting the rise of the envelope and the rise detected by detecting the rise of the envelope one symbol before the rise.
Acquiring the second time difference between the falling edge detected by detecting the falling edge of the envelope and the rising edge detected by detecting the falling edge of the envelope after the falling edge.
It is to demodulate or discard the radio signal in the section unit corresponding to the frame data, and when the envelope includes the predetermined patterns of the first time difference and the second time difference, the section including the predetermined pattern. A radio signal demodulation program that causes a computer to perform a process including demodulating a radio signal and discarding a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern. Detecting the falling edge of the envelope of a radio signal modulated with frame data containing a synchronization pattern and multiple symbols,
Detecting the rise of the envelope and
Acquiring the first time difference between the rise detected by detecting the rise of the envelope and the rise detected by detecting the rise of the envelope one symbol before the rise.
Acquiring the second time difference between the falling edge detected by detecting the falling edge of the envelope and the rising edge detected by detecting the falling edge of the envelope after the falling edge.
It is to demodulate or discard the radio signal in the section unit corresponding to the frame data, and when the envelope includes the predetermined patterns of the first time difference and the second time difference, the section including the predetermined pattern. A method for demodulating a radio signal, which comprises demodulating a radio signal and discarding a radio signal in a section that does not include the predetermined pattern when the envelope does not include the predetermined pattern.

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