Communication device and signal demodulation method

Abstract

The invention realizes a communication device and a signal demodulation method capable of reducing reception errors. A communication device (10) is provided with a reception unit (20) that demodulates a binary frequency shift modulated signal, and the reception unit has: a detection unit that detects a first bit, which is either a high bit or a low bit, along a time axis; and an estimation unit that estimates the presence of the second bit on the basis of the length of continuous time during which the first bit cannot be detected.

Description

Technical Field

[0001] The invention relates to a communication device and a signal demodulation method. Background Art

[0002] Radio Frequency Identification (RFID) systems are used in various fields including logistics management, production management, and access management.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] International Publication No. WO2010 / 110131 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] RFID systems that use electromagnetic waves (electromagnetic fields) in the low frequency (LF) band to send frequency-shifted modulation signals from tags to RFID readers / writers are also widely used. In the field where such RFID systems are applied, for example, electromagnetic waves emitted by other RFID systems or other devices become interference noise, which sometimes reduces the communication stability when communicating from tags to RFID readers / writers.

[0008] [Technical means to solve the problem]

[0009] In order to solve the above problem, a communication device in one form of the present disclosure includes a receiving unit, which demodulates a signal that is frequency-shift modulated with a binary value of a high bit and a low bit, and the receiving unit has: a detection unit, which detects a first bit that is either a high bit or a low bit from the received signal along a time axis; and an estimation unit, which estimates the existence of a second bit that is different from the first bit based on the length of continuous time during which the detection unit cannot detect the first bit. Through this form, a communication device that can reduce reception errors is realized.

[0010] In the above aspect, the detection unit may include a filter unit that passes the frequency component corresponding to the first bit in the received signal and reduces the frequency component corresponding to the second bit. This aspect provides a communication device that can effectively reduce reception errors in a communication device installation environment where a noise component of a frequency corresponding to the second bit exists.

[0011] In the above aspect, the detection unit may include a binarization unit that generates a binarized signal by applying a threshold value related to the intensity to the signal after passing through the filter unit. This aspect realizes a communication device that can accurately detect the first bit when the first bit is expressed with an amplitude of a predetermined period in the frequency shift modulated signal.

[0012] In the above aspect, the binarization unit may include a structure for performing a hysteresis operation using two threshold values. According to this aspect, a communication device capable of more accurately detecting the first bit is realized.

[0013] In the above aspect, the detection unit may include a first bit detection unit configured to detect the first bit based on the number of changes in the value of the binary signal. This aspect makes it easy to realize a communication device that can accurately detect the first bit.

[0014] In the above aspect, the detection unit may include an analog / digital (A / D) conversion unit that performs A / D conversion on the signal after passing through the filter unit. According to this aspect, the communication device can be easily realized.

[0015] In the above aspect, the detection unit may include: an A / D conversion unit that performs A / D conversion on the received signal; a partition signal generation unit that generates a partition signal of a specified time width cut out from the digital signal output by the A / D conversion unit; a frequency component strength calculation unit that sequentially calculates the strength of the frequency component corresponding to the first bit in the partition signal for a plurality of the partition signals; and a first bit detection unit that detects the first bit based on the time series data of the strength sequentially calculated by the frequency component strength calculation unit. Through this aspect, a communication device that can effectively reduce reception errors in a communication device installation environment where a noise component of a frequency corresponding to the second bit exists is realized.

[0016] In the above aspect, the receiving unit may further include: a noise evaluation unit for evaluating the electromagnetic wave intensity of the frequency band containing the frequency component corresponding to the first bit and the electromagnetic wave intensity of the frequency band containing the frequency component corresponding to the second bit in the environment where the communication device is installed; a determination unit for determining which of the high bit or the low bit is to be allocated to the first bit based on the evaluation result obtained by the noise evaluation unit; and a setting unit for switching the structure of the receiving unit based on the determination result obtained by the determination unit. Through this aspect, a communication device that can cope with the condition of the noise component in the installation environment of the communication device and effectively reduce reception errors is realized.

[0017] In the above embodiment, the noise evaluation unit may include: a first filter circuit that allows the electric signal of the frequency band including the frequency component corresponding to the first bit to pass through, and reduces the electric signal of the frequency band including the frequency component corresponding to the second bit; and a second filter circuit that allows the electric signal of the frequency band including the frequency component corresponding to the second bit to pass through, and reduces the electric signal of the frequency band including the frequency component corresponding to the first bit. Through this embodiment, a communication device including a noise evaluation unit is realized, and the noise evaluation unit can appropriately evaluate the electromagnetic wave intensity of the frequency band including the frequency component corresponding to the first bit and the electromagnetic wave intensity of the frequency band including the frequency component corresponding to the second bit in the environment where the communication device is installed.

[0018] In the form, the signal includes a first part corresponding to a preamble code composed of a plurality of consecutive high bits or low bits, and the receiving unit may further include: a determination unit that uses at least one of the intensity state of the frequency component corresponding to the high bit or the intensity state of the frequency component corresponding to the low bit in the first part of the received signal to determine which of the high bit or the low bit is assigned to the first bit; and a setting unit that switches the structure of the receiving unit based on the result of the determination obtained by the determination unit. Through this form, a communication device that can cope with the condition of the noise component in the setting environment of the communication device and effectively reduce reception errors is realized.

[0019] In order to solve the above problem, another form of communication device disclosed in the present invention includes a receiving unit, which demodulates a signal after frequency shift modulation with a binary value of a high bit and a low bit, and the receiving unit has: a high bit detection unit, which detects a high bit from the received signal along the time axis; a low bit estimation unit, which estimates the existence of a low bit based on the length of continuous time during which the high bit detection unit cannot detect a high bit, and outputs a first bit string after temporarily demodulating the signal; a low bit detection unit, which detects a low bit from the received signal along the time axis; a high bit estimation unit, which estimates the existence of a high bit based on the length of continuous time during which the low bit detection unit cannot detect a low bit, and outputs a second bit string after temporarily demodulating the signal; a demodulation unit, which outputs a third bit string after temporarily demodulating the signal from the received signal; and a bit determination unit, which determines the bit string after demodulating the signal by comparing the first bit string, the second bit string, and the third bit string. Through this form, a communication device that can reduce reception errors is realized.

[0020] In the above aspect, the following structure may be included, that is, it further includes a sending unit for wirelessly sending a command to a slave, and the signal is a wireless response from the slave to the command. Through this aspect, a communication device that can reduce reception errors and is applied to a communication system using a wireless response from a slave to a command is realized.

[0021] In the above aspect, the communication device may be an RFID reader. According to this aspect, an RFID reader capable of reducing reception errors is realized.

[0022] In order to solve the above problem, a signal demodulation method in one form of the present disclosure demodulates a signal after frequency shift modulation with two values ​​of a high bit and a low bit, and the signal demodulation method includes: a step of detecting a first bit as either a high bit or a low bit from the signal along a time axis; and a step of estimating the existence of a second bit, which is a bit different from the first bit, based on the length of continuous time during which the first bit cannot be detected. Through this form, a signal demodulation method that can reduce reception errors is realized.

[0023] [Effects of the Invention]

[0024] According to one aspect of the present invention, a communication device capable of reducing reception errors can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a diagram showing an overview of a communication device according to Embodiment 1 of the present disclosure and a communication system to which the communication device is applied.

[0026] Figure 2 This is a functional block diagram showing a main part configuration of a receiving unit of the communication device according to Embodiment 1 of the present disclosure.

[0027] Figure 3 This is a diagram for explaining the operation of a binarization unit in the receiving unit of the communication device according to Embodiment 1 of the present disclosure.

[0028] Figure 4 This is a functional block diagram showing a main part structure of a receiving unit of a communication device according to Embodiment 2 of the present disclosure.

[0029] Figure 5 This is a flowchart for explaining the operation of setting the switching of the demodulation process by the communication device according to the second embodiment of the present disclosure.

[0030] Figure 6 This is a functional block diagram showing a main part structure of a receiving unit of a communication device according to Embodiment 3 of the present disclosure.

[0031] Figure 7This is a functional block diagram showing a main part structure of a receiving unit of a communication device according to Embodiment 4 of the present disclosure.

[0032] Figure 8 This is a flowchart for explaining the operation of setting the switching of the demodulation process by the communication device according to the fourth embodiment of the present disclosure.

[0033] Fig. 9 This is a functional block diagram showing a main part structure of a receiving unit of a communication device according to Embodiment 5 of the present disclosure.

[0034] [Explanation of Symbols]

[0035] 1: Communication system

[0036] 10: Communication device

[0037] 20, 20A, 20B, 20C, 20D, 20E: Receiving unit

[0038] 21A, 21B, 21C, 21D: Detection department

[0039] 21Ea: High bit detection unit

[0040] 21Eb: Low bit detection unit

[0041] 22a: Low bit estimation unit (estimation unit)

[0042] 22b: High bit estimation unit (estimation unit)

[0043] 23: Demodulation unit

[0044] 24B, 24D: Noise Assessment Department

[0045] 25B, 25D: Judgment Unit

[0046] 26: Bit determination unit

[0047] 27B, 27D: Setting section

[0048] 30: Sending Department

[0049] 40: Control Department

[0050] 50: Network Communications Department

[0051] 60: Antenna

[0052] 70: Host device

[0053] 90: Tags

[0054] 211a: First filter unit (filter unit)

[0055] 211b: Second filter unit (filter unit)

[0056] 212: A / D conversion unit

[0057] 213: Binarization

[0058] 214: First bit detection unit

[0059] 215: Partition signal generation unit

[0060] 216a: First frequency component intensity calculation unit (frequency component intensity calculation unit)

[0061] 216b: Second frequency component intensity calculation unit (frequency component intensity calculation unit)

[0062] 217a: High bit detection unit (first bit detection unit)

[0063] 217b: Low bit detection unit (first bit detection unit)

[0064] Fa, FA, Fb, Fc, FC: bit string

[0065] G3C, G31, G32: Chart

[0066] S1~S8, S11~S24: Steps

[0067] SW1, SW2, SW3, SW4, SW5, SW6, SW7: Switching section

[0068] T1, T2, T3, T4, T5: Partition

[0069] Th1, Th2, Th3: Threshold

[0070] W1A, W1C, W2C, W2A, W3A, W4A, W4C, W4D, W4E: Signal waveform DETAILED DESCRIPTION

[0071] §1 Application Examples

[0072] pass Figure 1 and Figure 2 The communication device 10 shown in the structure is an example of a communication device of an application example of the present disclosure. The communication device 10 includes a receiving unit 20 (receiving unit 20A) that demodulates a signal subjected to frequency shift modulation using binary values ​​of an upper bit and a lower bit.

[0073] The receiving unit 20 (receiving unit 20A) includes a detecting unit 21A that detects the first bit (in the case of the first bit) of either the high bit or the low bit from the received signal along the time axis. Figure 2In addition, the receiving unit 20 (receiving unit 20A) includes a low bit estimation unit 22a (estimation unit) for estimating a second bit (in the case of the first bit) different from the first bit based on the length of time during which the first bit cannot be detected by the detection unit 21A. Figure 2 The existence of the low bit in the middle: 0) is inferred.

[0074] pass Figure 1 and Figure 6 The communication device 10 of the structure shown is also an example of a communication device of an application example of the present disclosure. The communication device 10 includes a receiving unit 20 (receiving unit 20C) that demodulates a signal that is frequency-shift modulated with two values ​​of a high bit and a low bit. The receiving unit 20 (receiving unit 20C) includes a detection unit 21C that detects the first bit (in the time interval) of either the low bit or the high bit from the received signal along the time axis. Figure 6 Middle is high bit: 1).

[0075] In addition, the receiving unit 20 (receiving unit 20C) includes a lower bit estimation unit 22a (estimation unit) for estimating a second bit (in the range of 1 to 300 ms) different from the first bit based on the length of time during which the first bit cannot be detected by the detecting unit 21C. Figure 6 Through the above application examples of the present disclosure, a communication device capable of reducing communication errors is realized.

[0076] §2 Structure Example

[0077] [Implementation method 1]

[0078] <Overview of communication system>

[0079] The embodiments of the present disclosure are described in detail below. Figure 1 This is a diagram showing an overview of a communication system 1 to which a communication device 10 according to Embodiment 1 of the present disclosure is applied.

[0080] The communication system 1 is a passive RFID system using electromagnetic waves in the LF band. The communication system 1 includes a communication device 10 and a host device 70 of the communication device 10 connected to the communication device 10 via an appropriate communication network. In addition, the communication system 1 includes a tag 90. An antenna 60 is connected to the communication device 10 so that wireless communication can be performed between the communication device 10 and the tag 90.

[0081] The tag 90 is a known passive wireless device also called a wireless tag, an integrated circuit (IC) tag, an RFID tag, a transponder, etc. The communication device 10 is a wireless communication device equivalent to the mother machine of the tag 90, also called an RFID reader, a tag reader, an RFID reader / writer, or simply a reader / writer, etc. When the communication device 10 transmits a command by wireless communication using electromagnetic waves (electromagnetic fields) of the LF frequency band, the tag 90 accumulates energy transmitted by the electromagnetic waves as electric energy and receives the command.

[0082] Then, the tag 90 uses the stored power to send a response (answer) to the command to the communication device 10. However, the application of the present invention is not limited to the technology related to the passive RFID system, and the present invention can also be applied to the RFID system in which the tag is equipped with a power source such as a battery.

[0083] <Communication device>

[0084] The communication device 10 includes a receiving unit 20, a transmitting unit 30, a control unit 40, and a network communication unit 50. The receiving unit 20 is a functional block that acquires information transmitted from the tag 90 to the communication device 10 from a signal received via the antenna 60.

[0085] The transmission unit 30 is a functional block that transmits a command to the tag 90 via the antenna 60 using electromagnetic waves in the LF band as a carrier wave. The network communication unit 50 is a communication interface for the communication device 10 to communicate with the host device 70 and the like via an appropriate communication network. The control unit 40 is an information processing device that controls the receiving unit 20, the transmission unit 30, and the network communication unit 50 to realize the functions of the communication device 10.

[0086] For example, the control unit 40 controls the transmission unit 30 according to the instruction of the upper device 70 received via the network communication unit 50, and transmits the required command to the tag 90 as the slave via the antenna 60. In addition, the control unit 40 controls the receiving unit 20 to receive the response (answer) of the tag 90 to the command, and obtains the data after demodulating the response from the receiving unit 20. In this way, the control unit 40 communicates with the upper device 70 via the network communication unit 50, and transmits the required information obtained from the obtained data to the upper device 70.

[0087] <Tag response>

[0088] Next, the signal format and the like related to the response from the tag 90 (transponder) are described. The following description of the signal format and data format is based on the International Organization for Standardization (ISO) 11784 / 11785 standard. The signal sent by the tag 90 is a frequency shift modulation (Frequency Shift Keying) signal (hereinafter referred to as FSK signal) modulated by the binary values ​​of high bit (high bit: binary 1) and low bit (low bit: binary 0).

[0089] In the modulated signal, the high bit is represented by a signal amplitude waveform of 16 cycles of a frequency of 123.2kHz. In addition, in the modulated signal, the low bit is represented by a signal amplitude waveform of 16 cycles of a frequency of 134.2kHz. That is, one high bit is transmitted in about 130μs, and one low bit is transmitted in about 119μs. In addition, the frequency of 134.2kHz is also the carrier frequency of the command signal issued by the communication device 10 as a reader / writer.

[0090] The response of the tag 90 to the communication device 10 includes a main body containing 112 bits of fixed-length data, and a communication frame of a pre-bit (Pre Bits) as a pre-synchronization code and an 8-bit start bit (Start Bits) following the pre-bit. The start bit is a fixed value 0b01111110. The pre-bit is a continuous 0 (low bit) of about 16 bits that is continuously output before the tag 90 outputs the start bit, for example, 0b0000000000000000. Here, "0b" is a symbol indicating that the following sequence is a binary value.

[0091] <Receiving Unit 20A>

[0092] Figure 2 This is a functional block diagram showing a main configuration of the reception unit 20A of the communication device 10 according to the first embodiment. Figure 2 The receiving unit 20A shown is an example of the receiving unit 20 of the communication device 10 in the first embodiment.

[0093] The receiving unit 20A has a detection unit 21A, which extracts and detects the upper bit from the FSK signal (refer to the signal waveform W1A) received by the communication device 10 from the tag 90. The detection unit 21A has a first filter unit 211a (filter unit), an A / D conversion unit 212, a binarization unit 213 and a first bit detection unit 214. These functional blocks process the FSK signal input to the detection unit 21A in the order described above. In addition, the receiving unit 20A has a low bit estimation unit 22a, which processes the signal output by the detection unit 21A (first bit detection unit 214), estimates the existence of the low bit and supplements it.

[0094] <First filter unit 211a>

[0095] The first filter unit 211a is a functional block that passes a signal component of a frequency of 123.2 kHz corresponding to the upper bits and reduces a signal component of a frequency of 134.2 kHz corresponding to the lower bits. The first filter unit 211a may be a low-pass filter or a band-pass filter having such a function.

[0096] When the FSK signal received from the tag 90 (see signal waveform W1A) passes through the first filter unit 211a, a signal with a frequency of 134.2kHz corresponding to the low bit cut off is obtained (see signal waveform W2A). Even if a noise component with a frequency of 134.2kHz is superimposed on the signal received by the communication device 10, such noise component is cut off and the signal is output from the first filter unit 211a.

[0097] <A / D Converter 212>

[0098] In Embodiment 1, the signal after passing through the first filter unit 211a is input to the A / D converter 212. The A / D converter 212 is a functional block that performs analog-to-digital conversion on the signal. The analog-to-digital conversion using the A / D converter 212 can be performed by appropriately applying a known method. For example, a comparator circuit can be used to perform the analog-to-digital conversion. In addition, the sampling period of the digital signal can also be set by a bit detection method based on a timer setting. Here, the sampling period of the analog-to-digital conversion using the A / D converter 212 is set to be sufficiently shorter than the period of the signal of the frequency 134.2kHz corresponding to the low bit, 7.45μs.

[0099] It is preferable to set the sampling period in the A / D converter 212 so that the period of the signal waveform corresponding to the low bit, 7.45 μs, is about 10 to 20 times the sampling period. By setting the upper limit of the sampling period to such a value, the waveform of the signal output by the first filter unit 211a can be fully expressed as a digital discrete value required for the subsequent processing. In addition, by setting the lower limit of the sampling period to such a value, the number of samples will not be increased too much.

[0100] <Binarization unit 213>

[0101] The binarization unit 213 generates and outputs a binarized signal (corresponding to the signal waveform W3A) from the digital signal (corresponding to the signal waveform W2A) output from the A / D conversion unit 212. The binarization unit 213 is a functional block that converts one cycle of an amplitude greater than a predetermined intensity into one pulse in the signal waveform input as a digital signal.

[0102] Figure 3 This is a diagram for explaining the operation of the binarization unit 213. The signal waveform W2A schematically shows the signal after passing through the first filter unit 211a. The graph G31 shows a waveform obtained by enlarging a part of the signal waveform W2A in the time axis direction, and each sampling data output by the A / D conversion unit 212 is represented by dots.

[0103] The intervals between the points in the graph G31 in the horizontal axis direction correspond to the sampling period of the analog-to-digital conversion in the A / D conversion unit 212. The vertical axis in the graph G31 represents the digital value of the intensity of the signal converted by the A / D conversion, that is, the value of the sampling data (hereinafter referred to as the sampling value). Figure 3 As indicated by the middle dotted line, in the binarization unit 213 , a threshold value Th1 and a threshold value Th2 are set for the sampled value.

[0104] The threshold Th1 and the threshold Th2 correspond to the digital values ​​obtained by A / D conversion, which correspond to the negative amplitude value and the positive amplitude value of the predetermined amplitude that are approximately equal to the magnitude of the analog signal (corresponding to the signal waveform W2A) input to the A / D conversion unit 212. That is, the central value of the threshold Th1 and the threshold Th2 is approximately equivalent to the amplitude 0 of the FSK signal. The threshold Th2 is larger than the threshold Th1, and is larger than the digital value obtained by A / D conversion that corresponds to the amplitude 0 of the FSK signal. The threshold Th1 is smaller than the digital value obtained by A / D conversion that corresponds to the amplitude 0 of the FSK signal.

[0105] However, depending on the noise environment, the threshold Th1 and the threshold Th2 do not necessarily need to be set in this way and can be changed appropriately. For example, when a noise component is superimposed on a frequency component corresponding to a high bit, the threshold Th1 or the threshold Th2 can be shifted according to the magnitude of the noise component.

[0106] In the time series sampling data, when the sampling value changes from a state less than the threshold value Th2 to a state greater than the threshold value Th2, the binarization unit 213 assigns a high binary value to each sampling data just before the next sampling value becomes less than the threshold value Th1. In addition, when the sampling value changes from a state greater than the threshold value Th1 to a state less than the threshold value Th1, the binarization unit 213 assigns a low binary value to each sampling data just before the next sampling value becomes more than the threshold value Th2.

[0107] Thus, the binarization unit 213 generates Figure 3 The sampled data outputted by the A / D converter 212 shown in the graph G31 is converted into a binary signal. The time series data converted into binary values ​​is Figure 3 In the diagram G32. Figure 2 In FIG. 1 , the time series data converted into binary values ​​by the binarization unit 213 is shown as a signal waveform W3A, and is shown at the same scale in the time axis direction as the signal waveform W2A showing the signal after passing through the first filter unit 211 a.

[0108] In the first embodiment, in the time region corresponding to the low bit in the FSK signal received from the tag 90, the binary value does not change in the signal output by the binarization unit 213. The reason for this is that since the amplitude of the signal corresponding to the low bit is reduced by the first filter unit 211a, a signal exceeding the range from the threshold Th1 to the threshold Th2 is not input to the binarization unit 213, and thus the binary value does not switch in the signal output from the binarization unit 213.

[0109] On the other hand, in the first embodiment, in the time region corresponding to the upper bit in the FSK signal received from the tag 90, a continuous pulse train having a number of pulses equal to the number of cycles of the signal with a frequency of 123.2 kHz is generated in the signal output by the binarization unit 213. As described above, the binarization unit 213 performs a hysteresis operation using two thresholds, so the transition of the binarization signal near the change point between the lower bit and the upper bit in the FSK signal received from the tag 90 is stable without causing ringing.

[0110] <First Bit Detection Unit 214>

[0111] The binarized signal (corresponding to the signal waveform W3A) output by the binarization unit 213 is processed by the first bit detection unit 214. Since the frequency component corresponding to the upper bit is selected by the first filter unit 211a, the first bit detection unit 214 extracts the upper bit from the binarized signal in the first embodiment.

[0112] When the first bit detection unit 214 detects a pulse in the binary signal, that is, when it detects a change from a continuously low state to a high state, it starts counting the number of pulses. When the number of pulses reaches 16, the counting of the number of pulses is reset and the number of pulses is continued. When there is no subsequent pulse after the number of pulses 16, the counting of the number of pulses is stopped.

[0113] Pulses can be counted by counting the number of changes in the binary signal, that is, the number of times the value rises or falls. The first bit detector 214 detects pulses in the binary signal and defines a period in which one high bit exists until the number of pulses reaches 16 (see signal waveform W4A).

[0114] Thus, the first bit detector 214 generates a digital signal in which 16 consecutive pulses in the binary signal are replaced with high binary data. Thus, the detector 21A having each functional block from the first filter unit 211a to the first bit detector 214 detects only the high bit (solid line in the signal waveform W4A) from the FSK signal received from the tag 90 along the time axis.

[0115] The output of the first bit detector 214 is also the output of the detector 21A. Thus, the detector 21A outputs a signal (see the solid line of the signal waveform W4A) in which a high bit is detected along the time axis based on the FSK signal (see the signal waveform W1A) received by the detector 21A from the tag 90.

[0116] The positions of the high bits in the time axis direction of the signal output by the detection unit 21A may be slightly different from the start position and the end position compared to the high bits in the FSK signal received by the communication device 10 from the tag 90. This is because, in the signal processing by the binarization unit 213, a hysteresis operation using two thresholds is performed as described above.

[0117] This is because the FSK signal received by the receiving unit 20A sometimes has a waveform disturbance in the transition region between the upper bit and the lower bit. This is because the use of A / D conversion in signal processing does not provide a resolution below the sampling period (sampling interval).

[0118] <Low Bit Estimation Unit 22a>

[0119] The lower bit estimation unit 22a estimates that the period during which the first bit detection unit 214 cannot extract the upper bit in the output of the detection unit 21A is the period of the lower bit (the dotted line in the signal waveform W4A).

[0120] The low bit estimation unit 22a estimates the presence of low bits based on the length of continuous time during which high bits cannot be detected in the signal that detects only high bits output by the detection unit 21A along the time axis. In the signal output by the first bit detection unit 214, the time interval between high bits is not necessarily an integer multiple of the duration of the low bits (about 119 μs).

[0121] Therefore, the low bit estimation unit 22a calculates the most reliable value as the number of low bits included between the high bits and the high bits based on the time interval between the high bits and the duration of the low bits (about 119 μs) to determine the number of low bits. In addition, the low bit estimation unit 22a similarly calculates the most reliable value as the number of high bits included in the duration of the high bits (the duration of the actual signal) and the duration of 1 bit of the high bit (about 130 μs) to determine the number of high bits.

[0122] In this way, the lower bit estimation unit 22a calculates and outputs the bit string FA as a result of the reception unit 20A demodulating the communication frame of the response received from the tag 90. The bit string FA output by the lower bit estimation unit 22a is also the output of the reception unit 20A.

[0123] <Effects, etc.>

[0124] According to the communication device 10 of embodiment 1 or the signal demodulation method of embodiment 1, the frequency component of the lower bit corresponding to the second bit which is different from the first bit in the received FSK signal is cut off by the first filter unit 211a. Therefore, even if noise having a frequency component corresponding to the lower bit which is the second bit is superimposed on the received FSK signal, the response from the tag 90 can be accurately demodulated.

[0125] As a cause of noise having a frequency component equivalent to a low bit, for example, electromagnetic waves emitted by a reader / writer different from the communication device 10 may be used. In addition, devices such as a power supply unit and a motor are also considered to be causes of noise in the LF band. According to Embodiment 1, a communication device is realized that can reduce the possibility of a decrease in communication stability with a tag even in an environment where such a noise source exists.

[0126] In the first embodiment, the detection unit 21A of the communication device 10 performs detection of the upper bit based on the binarization of the signal by the binarization unit 213 and the pulse counting by the first bit detection unit 214. However, the detection unit 21A may perform detection of the upper bit by applying envelope detection to the signal after passing through the first filter unit 211a. In this case, the detection unit 21A may perform detection of the upper bit based on the duration of the high binary value.

[0127] [Implementation method 2]

[0128] Another embodiment of the present invention is described below. In addition, for the sake of convenience, the same symbols are sometimes used to mark components having the same functions as the components described in the above embodiment, and the description thereof is not repeated. In the communication device 10 of the second embodiment, the structure of the receiving unit 20 is different from the receiving unit 20A in the first embodiment.

[0129] <Receiving Unit 20B>

[0130] Figure 4 This is a functional block diagram showing the configuration of the reception unit 20B of the communication device 10 according to the second embodiment. Figure 4 The receiving unit 20B shown is an example of the receiving unit 20 of the communication device 10 in the second embodiment.

[0131] The receiving unit 20B has a demodulation unit 23, which is a functional block that demodulates the FSK signal (refer to the signal waveform W1A) received from the tag 90 and outputs the bit string FA of the communication frame. The demodulation unit 23 includes a known demodulation circuit included in a general reader / writer. The demodulation unit 23 directly detects both the high bit and the low bit from the FSK signal and outputs them as the demodulated communication frame bit string.

[0132] The detection unit 21B of the second embodiment has the functional blocks of the detection unit 21A of the first embodiment, and further has a second filter unit 211b (filter unit). The second filter unit 211b passes the signal component of the frequency 134.2kHz corresponding to the low bit, and reduces the signal component of the frequency 123.2kHz corresponding to the high bit. The second filter unit 211b can be a high-pass filter circuit or a band-pass filter circuit having such a function.

[0133] The receiving unit 20B also has a high bit estimation unit 22b (estimation unit) in addition to the low bit estimation unit 22a of the receiving unit 20A of the first embodiment. The high bit estimation unit 22b is a functional block that estimates the existence of a high bit based on the length of continuous time during which the low bit cannot be detected in the signal output by the detection unit 21B along the time axis. That is, the low bit estimation unit 22a processes the signal output by the detection unit 21B (the first bit detection unit 214) to estimate and supplement the existence of the low bit, while the high bit estimation unit 22b estimates and supplements the existence of the high bit.

[0134] The receiving unit 20B further includes a noise evaluating unit 24B, a determining unit 25B, and a setting unit 27B. The noise evaluating unit 24B is a functional block that measures the noise component strength (background signal strength) at a frequency of 123.2 kHz and the noise component strength (background signal strength) at a frequency of 134.2 kHz in the environment where the communication device 10 is installed.

[0135] When demodulating the FSK signal (refer to the signal waveform W1A) received from the tag 90, the determination unit 25B determines which of the high bit and the low bit the receiving unit 20B assigns to the first bit based on the measurement result of the noise evaluation unit 24B. That is, the determination unit 25B determines which of the bits extracted from the FSK signal, i.e., the first bit, is to be set for demodulation by the receiving unit 20B. In addition, the determination result of the determination unit 25B may include a conclusion other than assigning the high bit to the first bit and assigning the low bit to the first bit.

[0136] The setting unit 27B is a functional block that controls switching of which functional block of the receiving unit 20B is to be used when demodulating the FSK signal (see signal waveform W1A) based on the determination result of the determination unit 25B. The switching units SW1 to SW4 are functional blocks that implement switching of the use of functional blocks under the control of the setting unit 27B.

[0137] <Action>

[0138] In the communication device 10 of the second embodiment, the operation of demodulating the FSK signal received from the tag 90 is switched according to the noise conditions in the environment in which the communication device 10 is installed. Figure 5 This is a flowchart for explaining the switching of such actions.

[0139] The communication device 10 of the second embodiment executes the command before sending a command to the tag 90. Figure 5The operation shown in the flowchart selects a function block, that is, switches the demodulation operation, and then sends a command to the tag 90. Then, the communication device 10 demodulates the response from the tag 90 using the function block set in the receiving unit 20B, that is, according to the selected demodulation operation.

[0140] Step S1: In the receiving unit 20B, the noise evaluation unit 24B obtains the background signal received by the antenna 60. The noise evaluation unit 24B evaluates the spectrum intensity of the frequency 134.2kHz and the spectrum intensity of the frequency 123.2kHz in the background signal. Such spectrum intensity evaluation can be performed by a known method. For example, the noise evaluation unit 24B can evaluate the spectrum intensity by performing analog-to-digital conversion on the background signal and applying Fast Fourier Transform (FFT).

[0141] Alternatively, the noise evaluation unit 24B may be configured to have the following two filter circuits. One is a bandpass filter (first filter circuit) that allows the frequency region including the frequency 123.2 kHz in the background signal (electromagnetic wave) received by the antenna 60 to pass through, and reduces the frequency band including the frequency 134.2 kHz. The other is a bandpass filter (second filter circuit) that allows the frequency region including the frequency 134.2 kHz in the background signal (electromagnetic wave) received by the antenna 60 to pass through, and reduces the frequency band including the frequency 123.2 kHz.

[0142] Then, the noise evaluation unit 24B can evaluate the noise using the intensity of the background signal that has passed through each bandpass filter. In addition, the bandpass filter of the noise evaluation unit 24B can be used as a circuit for the first filter unit 211a or the second filter unit 211b.

[0143] Step S2: Then, the determination unit 25B determines whether the spectrum intensity of the frequency 134.2kHz is greater than a specified value based on the evaluation result of the noise evaluation unit 24B. If it is determined to be greater, the process proceeds to step S3 (YES in S2). In other cases, the process proceeds to step S5 (NO in S2).

[0144] Step S3: The setting unit 27B selects the first filter unit 211a that cuts off the frequency 134.2kHz as the filter in the detection unit 21B. That is, the setting unit 27B selects Figure 4 The switch unit SW1 and the switch unit SW2 in the functional block diagram are controlled to select the first filter unit 211a to be applied to the signal processing for demodulation.

[0145] Step S4: Then, the setting unit 27B selects the low bit estimation unit 22a which processes the signal outputted from the detection unit 21B, estimates the existence of the low bit and supplements it as the estimation unit in the receiving unit 20B. Figure 4 The switch unit SW3 and the switch unit SW4 in the functional block diagram are controlled to select the application of the lower bit estimation unit 22a to the signal processing for demodulation.

[0146] When the flow reaches step S4, the setting unit 27B selects the first filter unit 211a, the A / D conversion unit 212, the binarization unit 213, the first bit detection unit 214, and the lower bit estimation unit 22a as the functional blocks for demodulating the FSK signal received from the tag 90. That is, in the above case, in the receiving unit 20B, the demodulation process of the FSK signal received from the tag 90 is set to be performed in exactly the same manner as in the first embodiment. In other words, in the above case, the detection unit 21B assigns the upper bit as the first bit extracted from the FSK signal. Then the flow ends.

[0147] Step S5: The determination unit 25B determines whether the spectrum intensity of the frequency 123.2kHz is greater than a predetermined value based on the evaluation result of the noise evaluation unit 24B. If it is determined to be greater, the process proceeds to step S6 (Yes in S5). Otherwise, the process proceeds to step S8 (No in S5).

[0148] Step S6: The setting unit 27B selects the second filter unit 211b that cuts off the frequency 123.2kHz as the filter in the detection unit 21B. That is, the setting unit 27B selects the second filter unit 211b that cuts off the frequency 123.2kHz as the filter in the detection unit 21B. Figure 4 The switch unit SW1 and the switch unit SW2 in the functional block diagram are controlled to select the second filter unit 211b to be applied to the signal processing for demodulation.

[0149] Step S7: Then, the setting unit 27B selects the upper bit estimation unit 22b which processes the signal outputted from the detection unit 21B and estimates and supplements the existence of the upper bit as the estimation unit in the receiving unit 20B. Figure 4 The switch unit SW3 and the switch unit SW4 in the functional block diagram are controlled to select the upper bit estimation unit 22b to be applied to the signal processing for demodulation.

[0150] When the flow reaches step S7, the setting unit 27B selects the second filter unit 211b, the A / D converter 212, the binarization unit 213, the first bit detector 214, and the upper bit estimation unit 22b as the functional blocks for demodulating the FSK signal received from the tag 90. In this case, in the detection unit 21B, the component of the frequency 123.2kHz corresponding to the upper bit is cut off from the FSK signal received from the tag 90, and the signal component of the frequency corresponding to the lower bit is processed in the opposite manner to the case of the first embodiment.

[0151] In this case, the detector 21B detects only the lower bit along the time axis from the FSK signal received from the tag 90. Then, the upper bit estimation unit 22b performs the opposite operation to the lower bit estimation unit 22a and supplements the signal output by the detector 21B with the upper bit.

[0152] In addition, in the above case, the detection unit 21B selects the lower bit as the first bit extracted from the FSK signal. Therefore, in the above case, the receiving unit 20B is set to reduce the possibility of communication stability reduction by demodulating the FSK signal received from the tag 90 even in an environment with a large noise component of the frequency 123.2kHz. Then the flow ends.

[0153] Step S8: The setting unit 27B selects to cause the demodulation unit 23 to perform the demodulation process in the receiving unit 20B. Figure 4 The switching unit SW1 and the switching unit SW4 in the functional block diagram in are controlled to select the demodulation unit 23 to be applied to the signal processing for demodulation.

[0154] Thus, in the installation environment of the communication device 10, when the noise components of the frequencies corresponding to the upper bits and the frequencies corresponding to the lower bits are small, the receiving unit 20B performs signal processing in a normal reader / writer that directly detects the upper bits and the lower bits. Then the flow ends.

[0155] <Effects, etc.>

[0156] According to the communication device 10 of Embodiment 2 or the signal demodulation method of Embodiment 2, it is possible to switch to a preferred method according to the state of interference noise in the setting environment to select the demodulation process of the FSK signal received from the tag 90. Therefore, according to Embodiment 2, it is possible to realize a communication device that can reduce the possibility of a decrease in communication stability with the tag under various conditions.

[0157] In Embodiment 2, when the result of the worry determination unit 25B determining the noise condition in the environment where the communication device 10 is installed is that the influence of the noise is large, the communication device 10 can operate as follows. As an example of a situation where there is such a worry, there can be cited a situation where the intensity of the noise component at a frequency of 123.2kHz and the intensity of the noise component at a frequency of 134.2kHz are both large.

[0158] If there is such a concern, the communication device 10 may send a command to the tag 90 after a delay timing instead of immediately sending a command to the tag 90. According to this operation, when noise is generated when a plurality of RFID readers are close to each other, communication errors can be effectively reduced.

[0159] In embodiment 2, determination unit 25B is configured to determine the condition of noise in the environment in which communication device 10 is installed, and setting unit 27B switches the demodulation action according to the result of the determination. However, setting unit 27B may not automatically switch the demodulation action according to the result of the determination by determination unit 25B, but communication device 10 may be configured in such a manner that, for example, the result of the determination is prompted to a host device or operator of communication device 10.

[0160] In the above case, when the host device or the operator refers to the result and instructs the communication device 10 to switch the demodulation operation, the communication device 10 may be configured to switch the demodulation operation through the setting unit 27B based on the instruction. Alternatively, the communication device 10 may be configured such that the setting unit 27B switches the demodulation operation according to a forced instruction from the host device or the operator regardless of the result of the determination by the determination unit 25B.

[0161] [Variant 1]

[0162] Modification 1 is an embodiment of the communication device of the present disclosure after partially changing the structure of Implementation Example 1. In the communication device 10 of Modification 1, the first filter unit 211a of Implementation Example 1 is replaced by the second filter unit 211b, and the low bit estimation unit 22a of Implementation Example 1 is replaced by the high bit estimation unit 22b (estimation unit).

[0163] That is, in the receiving unit 20 of the communication device 10 of Modification 1, the low bit is selected as the first bit extracted from the FSK signal. According to Modification 1, a communication device 10 that can reduce the possibility of reduction in communication stability even in an environment where the noise component of the frequency 123.2kHz is large is implemented. In addition, in the communication device 10 of Embodiment 2, the demodulation operation in the receiving unit 20B when the process of switching the operation reaches step S7 is the same as the demodulation operation in the communication device of Modification 1.

[0164] [Implementation method 3]

[0165] <Receiving Unit 20C>

[0166] Figure 6 This is a functional block diagram showing a main part configuration of a reception unit 20C of a communication device 10 according to the third embodiment. Figure 6 The receiving unit 20C shown is an example of the receiving unit 20 of the communication device 10 in the third embodiment.

[0167] The receiving unit 20C includes a detection unit 21C that extracts and detects a high bit from a signal (refer to the signal waveform W1C) that is an FSK signal received from the tag 90 by the communication device 10. The detection unit 21C includes an A / D conversion unit 212, a partition signal generation unit 215, a first frequency component intensity calculation unit 216a (frequency component intensity calculation unit), and a high bit detection unit 217a (first bit detection unit) that process the input FSK signal in the order described below.

[0168] In addition, the receiving unit 20C has a low bit estimation unit 22a, which processes the signal output by the detection unit 21C (high bit detection unit 217a), estimates the existence of the low bit and supplements it. In the third embodiment, the functions of the A / D conversion unit 212 and the low bit estimation unit 22a are the same as those of the A / D conversion unit 212 and the low bit estimation unit 22a in the first embodiment, respectively.

[0169] <Partition signal generation unit 215>

[0170] The partition signal generating unit 215 is a functional block that divides the FSK signal, which is a digital signal outputted from the A / D converter 212, into each partition and outputs the divided signal (see signal waveform W2C). The range of each partition is Figure 6 The signal waveform W1C of the FSK signal received from the tag 90 is schematically shown by marking symbols T1, T2, T3, . . .

[0171] The length of each partition is set to be shorter than the duration of the high bit and the low bit. In addition, each partition signal may be a FSK signal that is divided and cut out, but it is preferable that the portion of the original FSK signal is repeated in the adjacent partition. That is, for example, it is preferable that the partition signal of the partition T3 has a portion of the original FSK signal repeated with the partition T2 at the beginning of the period, and has a portion of the original FSK signal repeated with the partition T4 at the end of the period.

[0172] The length of each partition is preferably at least 2 / 3 of the duration of a high bit or a low bit. In the FSK signal, it is preferably set to allocate multiple partitions corresponding to one high bit or one low bit. The number of such allocations is preferably about 3 to 10. Therefore, the shift of the start position of each partition cut from the FSK signal is preferably about 10μs to 40μs.

[0173] <First Frequency Component Strength Calculation Unit 216a>

[0174] The first frequency component intensity calculation unit 216a is a functional block that calculates the spectrum intensity of the frequency 123.2kHz corresponding to the high bit for the signal of each partition (T1, T2, T3...) generated by the partition signal generation unit 215 (refer to Figure G3C). Such spectrum intensity calculation can be performed by a known method. For example, the first frequency component intensity calculation unit 216a can calculate the spectrum intensity by applying a fast Fourier transform (FFT) to the signal of each partition.

[0175] <High bit detection unit 217a>

[0176] The upper bit detector 217a generates the next digital signal based on the spectrum intensity of the frequency corresponding to the upper bit of each partition calculated by the first frequency component intensity calculator 216a. Regarding the time representing the partition, if the spectrum intensity of the partition is above the threshold value Th3 (see graph G3C), it has a high binary value.

[0177] Here, the so-called time representing the partition is the time corresponding to the partition in the FSK signal, preferably the time in the center of the partition. In addition, here, the threshold Th3 is set near the center of the spectrum intensity corresponding to the high bit situation and the spectrum intensity corresponding to the low bit situation.

[0178] In addition, here, for example, the maximum value of the spectrum intensity of each partition in the communication frame or the average value of the spectrum intensity of the upper bit point can be regarded as the spectrum intensity corresponding to the high bit situation. In addition, the minimum value of the spectrum intensity of each partition in the communication frame or the average value of the spectrum intensity of the lower bit point can be regarded as the spectrum intensity corresponding to the low bit situation.

[0179] Thus, when the spectrum intensity of the frequency corresponding to the upper bit is large, the first frequency component intensity calculation unit 216a and the upper bit detection unit 217a output a digital signal having a high binary value at that moment (see the solid line of the signal waveform W4C).

[0180] The position of the high bit in the time axis direction of the signal output by the detection unit 21C may be slightly different from the start position and the end position compared to the high bit in the FSK signal received by the communication device 10 from the tag 90. This is because the first bit detection unit 214 can also determine a binary value of high or low for the partition of the transition area including the high bit and the low bit in the FSK signal.

[0181] In addition, the reason is that in the FSK signal received by the receiving unit 20A, there is sometimes a disorder in the waveform in the transition area between the high bit and the low bit. In addition, the reason is that by using the A / D converter in signal processing, there is no accuracy in the position in the time axis direction below the sampling period (sampling interval).

[0182] <Low Bit Estimation Unit 22a>

[0183] As in the case of Embodiment 1, the lower bit estimation unit 22a calculates and outputs a bit string FC as a result of the reception unit 20C demodulating the communication frame of the response received from the tag 90. The bit string FC output by the lower bit estimation unit 22a is also the output of the reception unit 20C.

[0184] <Effects, etc.>

[0185] According to the communication device 10 of embodiment 3 or the signal demodulation method of embodiment 3, the frequency component of the lower bit corresponding to the second bit which is a bit different from the first bit in the received FSK signal is not considered in the demodulation process. Therefore, even if noise having a frequency component corresponding to the lower bit which is the second bit is superimposed on the received FSK signal, the response from the tag 90 can be accurately demodulated.

[0186] [Implementation method 4]

[0187] <Receiving Unit 20D>

[0188] In communication device 10 according to the fourth embodiment, the configuration of reception unit 20 is different from reception unit 20C in the third embodiment. Figure 7 This is a functional block diagram showing the configuration of the reception unit 20D of the communication device 10 according to the fourth embodiment. Figure 7 The receiving unit 20D shown is an example of the receiving unit 20 of the communication device 10 in the fourth embodiment.

[0189] The receiving unit 20D includes a demodulator 23, which is a functional block that demodulates the FSK signal (refer to the signal waveform W1C) received from the tag 90 and outputs a bit string FC of the communication frame. The receiving unit 20D also includes a high bit estimation unit 22b in addition to the low bit estimation unit 22a included in the receiving unit 20C of the third embodiment. The functions of the demodulator 23 and the high bit estimation unit 22b are the same as those of the second embodiment.

[0190] The detection unit 21D of the fourth embodiment has, in addition to the functional blocks of the detection unit 21C of the third embodiment, a second frequency component intensity calculation unit 216b (frequency component intensity calculation unit) and a low bit detection unit 217b (first bit detection unit). The second frequency component intensity calculation unit 216b is different from the first frequency component intensity calculation unit 216a in that the frequency spectrum intensity of the frequency 134.2kHz corresponding to the low bit is calculated.

[0191] The difference between the low bit detection unit 217b and the high bit detection unit 217a is that the low bit detection unit 217b outputs a digital signal having detected low bits based on the spectrum intensity corresponding to the low bits of each partition calculated by the second frequency component intensity calculation unit 216b. If the spectrum intensity corresponding to the low bits of each partition is above the threshold value Th4, the low bit detection unit 217b outputs a digital signal having a low binary value (refer to the solid line of the signal waveform W4D).

[0192] In the receiving unit 20D of the fourth embodiment, the second frequency component intensity calculation unit 216b, the lower bit detection unit 217b, and the upper bit estimation unit 22b can process the signal of each partition generated by the partition signal generation unit 215. Then, in the receiving unit 20D, the bit string FC as the result of demodulating the communication frame of the response can be output using the digital signal (refer to the solid line of the signal waveform W4D) from which the lower bit as the second bit is extracted.

[0193] Furthermore, the receiving unit 20D includes a noise evaluation unit 24D, a determination unit 25D, and a setting unit 27D. The noise evaluation unit 24D is a functional block that calculates the spectrum intensity of a time region corresponding to a pre-bit of a communication frame received by the communication device 10 from the tag 90. The determination unit 25D determines whether the receiving unit 20D allocates a high bit or a low bit to the first bit when demodulating the FSK signal (see signal waveform W1A) received from the tag 90.

[0194] That is, the determination unit 25D determines which bit, that is, the first bit extracted from the FSK signal, is to be used for demodulation by the receiving unit 20D. The determination result of the determination unit 25D may include a conclusion other than allocating the upper bit to the first bit and allocating the lower bit to the first bit.

[0195] The setting unit 27D controls switching of which functional block of the receiving unit 20D is used when demodulating the FSK signal (see signal waveform W1A) received from the tag 90 based on the determination result of the determination unit 25D. The switching unit SW5 to the switching unit SW7 are functional blocks that implement switching of the functional blocks to be used under the control of the setting unit 27D.

[0196] <Action>

[0197] In the communication device 10 of the fourth embodiment, the operation of demodulating the FSK signal received from the tag 90 is switched according to the condition of noise in the environment in which the communication device 10 is installed. Figure 8 This is a flowchart for explaining the switching of such actions.

[0198] After receiving a response from the tag 90, the communication device 10 of the fourth embodiment selects a function block used in the demodulation process of the communication frame, i.e., switches the demodulation operation, using the preamble of the communication frame. Then, the communication device 10 performs demodulation of the response from the tag 90 using the function block set in the receiving unit 20D, i.e., using the selected demodulation operation.

[0199] Step S11: The determination unit 25D controls the A / D conversion unit 212, the partition signal generation unit 215, and the noise evaluation unit 24D so that the noise evaluation unit 24D calculates the spectrum intensity of each partition of the communication frame for the FSK signal received from the tag 90. The noise evaluation unit 24D calculates the spectrum intensity of the frequency 123.2 kHz corresponding to the high bit and the spectrum intensity of the frequency 134.2 kHz corresponding to the low bit of the interval.

[0200] Step S12: Then, the determination unit 25D extracts the spectrum intensity of the partition corresponding to the pre-bit from the spectrum intensity of each partition of the communication frame. As described above, the pre-bit of the communication frame is a structure of approximately 16 consecutive low bits (for example, 0b0000000000000000). Therefore, in the interval corresponding to the pre-bit of the communication frame, the waveform of the frequency 134.2kHz of the signal from the tag 90 lasts for a maximum of 2.0ms. The determination unit 25D determines the interval corresponding to the pre-bit of the communication frame based on the end time of the command sent by the communication device 10 to the tag 90.

[0201] Step S13: Next, the determination unit 25D determines whether the spectrum intensity of the frequency 123.2 kHz corresponding to the upper bit is less than half of the spectrum intensity of the frequency 134.2 kHz corresponding to the lower bit, using the spectrum intensity in the section corresponding to the pre-bit extracted in step S12.

[0202] If it is judged to be less than half (Yes in S13), the process proceeds to step S14. In other cases (No in S13), the process proceeds to step S20. In the former case, it is judged that the noise component of the frequency 123.2kHz in the installation environment of the communication device 10 is small, and in the latter case, it is judged that the noise component is large.

[0203] Step S14: The determination unit 25D uses the spectrum intensity in the extracted interval corresponding to the pre-bit to calculate the threshold Th3 for binarization by the upper bit detection unit 217a. The determination unit 25D calculates the middle value of the spectrum intensity of the frequency 123.2kHz and the spectrum intensity of the frequency 134.2kHz as the threshold Th3.

[0204] Step S15: Then, the determination unit 25D operates the first frequency component strength calculation unit 216a, the high bit detection unit 217a, and the low bit estimation unit 22a to demodulate the data of the communication frame including at least the start bit. That is, the determination unit 25D demodulates the data by detecting the signal of the frequency 123.2kHz corresponding to the high bit. Since the noise component of the frequency 123.2kHz in the setting environment of the communication device 10 is small, the high bit (binary 1) in the start bit (0b01111110) can be demodulated.

[0205] Step S16: Then, the determination unit 25D extracts the spectrum intensity of the partition corresponding to the interval of continuous high bits of the start bit from the spectrum intensity of each partition of the communication frame calculated by the noise evaluation unit 24D. In the start bit of the communication frame, since there are 6 consecutive high bits, their duration is about 779μs. The determination unit 25D estimates the interval of continuous high bits based on the results of the processing of the first frequency component intensity calculation unit 216a, the high bit detection unit 217a and the low bit estimation unit 22a in step S15.

[0206] Step S17: Next, the determination unit 25D determines whether the spectrum intensity of the frequency 134.2 kHz corresponding to the low bits is less than half of the spectrum intensity of the frequency 123.2 kHz corresponding to the high bits, using the spectrum intensity in the interval where the high bits of the start bit extracted in step S16 are continuous.

[0207] If it is judged to be less than half (Yes in S17), the process proceeds to step S18. In other cases (No in S17), the process proceeds to step S19. In the former case, it is judged that the noise component of the frequency 134.2kHz in the installation environment of the communication device 10 is small, and in the latter case, it is judged that the noise component is large.

[0208] Step S18: The setting unit 27D selects to cause the demodulation unit 23 to perform the demodulation process in the receiving unit 20D. Figure 7 The switch unit SW5 and the switch unit SW7 in the functional block diagram are controlled to select the demodulation unit 23 to be applied to the signal processing for demodulation.

[0209] Thus, in the setting environment of the communication device 10, when the noise components of the frequency corresponding to the high bit and the frequency corresponding to the low bit are small, the receiving unit 20D performs the signal processing in the normal reader / writer that directly detects the high bit and the low bit. This is because in such a case, it is determined that it is appropriate to perform the normal demodulation processing. Then the flow ends.

[0210] Step S19: The setting unit 27D selects the demodulation process in the receiving unit 20D to be performed by the A / D conversion unit 212, the partition signal generation unit 215, the first frequency component strength calculation unit 216a, the upper bit detection unit 217a, and the lower bit estimation unit 22a. Figure 7 The switching units SW5 to SW7 in the functional block diagram are controlled to select these functional blocks to be applied to the signal processing for demodulation.

[0211] In the case, the demodulation process performed by the receiving unit 20D is the same as the demodulation process performed by the receiving unit 20C of the embodiment 3. In other words, in the case, the detection unit 21D assigns the high bit as the first bit extracted from the FSK signal. The reason is that it is judged that, in the setting environment of the communication device 10, the noise component of the frequency corresponding to the high bit is small, but the noise component of the frequency corresponding to the low bit is large. However, here, the value calculated in step S14 can also be used in the threshold value Th3 applied in the high bit detection unit 217a. Then the process ends.

[0212] Step S20: The determination unit 25D uses the spectrum intensity in the section corresponding to the extracted pre-bit to set the threshold Th4 for binarization by the low bit detection unit 217b. The determination unit 25D calculates half the spectrum intensity of the frequency 134.2 kHz as the threshold Th4.

[0213] Step S21: Then, the determination unit 25D operates the second frequency component strength calculation unit 216b, the low bit detection unit 217b, and the high bit estimation unit 22b to try to demodulate the data up to at least the start bit of the communication frame. That is, the determination unit 25D tries to demodulate the data by detecting the signal of the frequency 134.2kHz corresponding to the low bit.

[0214] Step S22: Then, the determination unit 25D determines whether the high bit of the start bit is detected in the section corresponding to the preamble of the communication frame in step S21. If it is determined that it is detected (yes in S22), the process proceeds to step S23. In other cases (no in S22), the process proceeds to step S24. In the former case, it is determined that the noise component of the frequency 134.2kHz in the installation environment of the communication device 10 is small, and in the latter case, it is determined that the noise component is large.

[0215] Step S23: The setting unit 27D selects the demodulation process in the receiving unit 20D to be performed by the A / D conversion unit 212, the partition signal generation unit 215, the second frequency component strength calculation unit 216b, the low bit detection unit 217b, and the high bit estimation unit 22b. Figure 7 The switching units SW5 to SW7 in the functional block diagram are controlled to select these functional blocks to be applied to the signal processing for demodulation.

[0216] In the above case, the demodulation process performed by the receiving unit 20D is different from the demodulation process performed by the receiving unit 20C of the third embodiment, and is performed by extracting only the frequency component corresponding to the low bit. In other words, in the above case, the detection unit 21D assigns the low bit as the first bit extracted from the FSK signal. The reason is that it is determined that in the setting environment of the communication device 10, the noise component of the frequency corresponding to the low bit is small, but the noise component of the frequency corresponding to the high bit is large. Then the process ends.

[0217] Step S24: The determination unit 25D determines that the response received from the tag 90 cannot be demodulated in the installation environment of the communication device 10. Then the flow ends.

[0218] <Effects, etc.>

[0219] According to the communication device 10 of Embodiment 4 or the signal demodulation method of Embodiment 4, it is possible to switch to a preferred method according to the state of interference noise in the setting environment to select the demodulation process of the FSK signal received from the tag 90. Therefore, according to Embodiment 4, a communication device capable of reducing the possibility of reduction in communication stability with the tag under various conditions is realized.

[0220] [Variant 2]

[0221] Variation 2 is an embodiment of the communication device of the present disclosure after a part of the structure is changed from Implementation Example 3. In the communication device 10 of Variation 2, the first frequency component strength calculation unit 216a, the high bit detection unit 217a, and the low bit estimation unit 22a of Implementation Example 3 are replaced by the second frequency component strength calculation unit 216b, the low bit detection unit 217b, and the high bit estimation unit 22b, respectively.

[0222] That is, in the receiving unit 20 of the communication device 10 of the modification 2, the low bit is selected as the first bit extracted from the FSK signal. According to the modification 1, the communication device 10 that can reduce the possibility of reduction in communication stability even in an environment where the noise component of the frequency 123.2kHz is large is realized. In addition, in the communication device 10 of the embodiment 3, the demodulation operation in the receiving unit 20C when the process of switching the operation reaches step 23 is the same as the demodulation operation in the communication device of the modification 2.

[0223] [Implementation method 5]

[0224] <Receiving Unit 20E>

[0225] Fig. 9 This is a functional block diagram showing the configuration of the reception unit 20E of the communication device 10 according to the fifth embodiment. Fig. 9 The receiving unit 20E shown is an example of the receiving unit 20 of the communication device 10 in the fifth embodiment.

[0226] The receiving unit 20E includes an upper bit detection unit 21Ea that extracts and detects an upper bit from the FSK signal (refer to the signal waveform W1A) received by the communication device 10 from the tag 90. The upper bit detection unit 21Ea includes a first filter unit 211a, an A / D converter 212, a binarization unit 213, and a first bit detection unit 214. The function and structure of the upper bit detection unit 21Ea are the same as those of the detection unit 21A in the first embodiment.

[0227] In addition, the receiving unit 20E has a low bit estimation unit 22a, which estimates and supplements the existence of low bits from the signal (refer to the solid line of the signal waveform W4A) output by the high bit detection unit 21Ea along the time axis based on the length of the continuous time when the high bit cannot be detected. The function of the low bit estimation unit 22a is the same as that in the first embodiment.

[0228] Thus, the receiving unit 20E calculates the bit string Fa after the upper bit detector 21Ea and the lower bit estimator 22a temporarily demodulate the FSK signal received from the tag 90. Temporary demodulation here means that the bit string Fa is not necessarily consistent with the bit string FA finally output by the receiving unit 20E.

[0229] The receiving unit 20E includes a low bit detection unit 21Eb that extracts and detects a low bit from the FSK signal received by the communication device 10 from the tag 90. The low bit detection unit 21Eb includes a second filter unit 211b, an A / D converter 212, a binarization unit 213, and a first bit detection unit 214. The functions of the second filter unit 211b, the A / D converter 212, the binarization unit 213, and the first bit detection unit 214 constituting the low bit detection unit 21Eb are the same as those in Embodiment 2 and the like.

[0230] In addition, the receiving unit 20E has a high bit estimation unit 22b, which estimates and supplements the existence of the high bit from the signal (refer to the solid line of the signal waveform W4E) output by the low bit detection unit 21Eb along the time axis and detects the low bit based on the length of the continuous time when the low bit cannot be detected. The function of the high bit estimation unit 22b is the same as that in the embodiment 2. In this way, the bit string Fb after the FSK signal received from the tag 90 is temporarily demodulated by the low bit detection unit 21Eb and the high bit estimation unit 22b is calculated inside the receiving unit 20E.

[0231] In addition, the receiving unit 20E includes a demodulator 23, which demodulates the FSK signal received from the tag 90 without cutting off the signal component of the frequency 123.2 kHz corresponding to the high bit and the signal component of the frequency 134.2 kHz. The function of the demodulator 23 is the same as that in Embodiment 2. In this way, the bit string Fc obtained by temporarily demodulating the FSK signal received from the tag 90 by the demodulator 23 is calculated inside the receiving unit 20E.

[0232] The receiving unit 20E further includes a bit determination unit 26 that determines a bit sequence FA to be output finally based on the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc. The bit determination unit 26 is a functional block that determines the bit sequence FA by comparing the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc based on the following rule.

[0233] The specific operation of the bit determination unit 26 is as follows. The bits at a certain position of each of the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc are all set to high bits (1). In this case, the bit determination unit 26 determines the value of the bit at the position of the output bit sequence FA to be high bits (1).

[0234] Regarding the bits at certain positions of each of the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc, two are set to high bits (1) and one is set to low bit (0). In this case, the bit decision unit 26 decides the value of the bit at the position of the output bit sequence FA to be the low bit (0).

[0235] One bit at a certain position of each of the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc is set to a high bit (1) and two bits to a low bit (0). In this case, the bit decision unit 26 decides the value of the bit at the position of the output bit sequence FA to be a high bit (1).

[0236] The bits at a certain position of each of the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc are all set to low bits (0). In this case, the bit decision unit 26 decides the bits at the positions of the output bit sequence FA to be low bits (0).

[0237] <Effects, etc.>

[0238] According to the communication device 10 of embodiment 5 or the signal demodulation method of embodiment 5, a communication device is implemented that demodulates the FSK signal received from the tag 90 and can reduce the possibility of reduced communication stability with the tag without switching the circuit under various conditions of interference noise in the setting environment.

[0239] For example, assume that in an environment where the communication device 10 is installed, noise interferes with a frequency component equivalent to a low bit. In the case, it can be expected that the bit string Fa based on the extraction of the frequency component equivalent to the high bit is accurately temporarily demodulated. However, in the case, in the bit string Fb based on the extraction of the frequency component equivalent to the low bit, or the bit string Fc in which the frequency component equivalent to the low bit is also detected, the high bit is erroneously temporarily demodulated as a low bit. Here, according to the communication device 10 of embodiment 5, the bit determination unit 26 operates as described above. Therefore, in the bit string FA output by the bit determination unit 26, the FSK signal received from the tag 90 is accurately demodulated.

[0240] In addition, for example, it is assumed that there is no interference from noise corresponding to low-bit frequency components and noise corresponding to high-bit frequency components in the environment where the communication device 10 is installed. In this case, the bit sequence Fa, the bit sequence Fb, and the bit sequence Fc are all accurately provisionally demodulated, and the bit sequence FA output by the bit determination unit 26 is also accurately demodulated.

[0241] 〔Software-based implementation example〕

[0242] The functions of the communication device 10 (hereinafter referred to as the "device") can be realized by a program for causing a computer to function as the device, and a program for causing a computer to function as each control block of the device (particularly the control unit 40, and each unit included in the receiving unit 20 that performs control or digital signal processing).

[0243] As the various units that perform control or digital signal processing and are included in the receiving unit 20, in particular, there can be listed a binarization unit 213, a first bit detection unit 214, a partition signal generation unit 215, a first frequency component intensity calculation unit 216a, a second frequency component intensity calculation unit 216b, a high bit detection unit 217a, a low bit detection unit 217b, a low bit estimation unit 22a, a high bit estimation unit 22b, a noise evaluation unit 24D, a determination unit 25B, a determination unit 25D, a setting unit 27B, and a setting unit 27D.

[0244] In the above case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and the storage device execute the program to implement the functions described in the above embodiments.

[0245] The program may also be recorded in one or more recording media that are not temporary and can be read by a computer. The recording medium may be included in the device or not. In the latter case, the program may also be supplied to the device via any transmission medium, whether wired or wireless.

[0246] In addition, part or all of the functions of each control block can also be realized by a logic circuit. For example, an integrated circuit having a logic circuit that functions as each control block is also included in the scope of the present invention. In addition, for example, the functions of each control block can also be realized by a quantum computer.

[0247] In addition, each process described in each embodiment may be performed by artificial intelligence (AI). In this case, AI may be executed in the control device or in other devices (such as edge computers or cloud servers).

[0248] 〔Summarize〕

[0249] The communication device of form 1 of the present disclosure includes a receiving unit, which demodulates a signal that is frequency-shift modulated with a binary value of a high bit and a low bit, and the receiving unit has: a detection unit, which detects a first bit that is either a high bit or a low bit from the received signal along a time axis; and an estimation unit, which estimates the existence of a second bit that is different from the first bit based on the length of continuous time that the detection unit cannot detect the first bit.

[0250] In the communication device according to aspect 2 of the present disclosure, in aspect 1, the detection unit includes a filter unit that passes a frequency component corresponding to the first bit in the received signal and reduces a frequency component corresponding to the second bit.

[0251] A communication device according to aspect 3 of the present disclosure is characterized in that in aspect 2, the detection unit includes a binarization unit that applies a threshold value related to intensity to the signal after passing through the filter unit to generate a binarized signal.

[0252] A communication device according to a fourth aspect of the present disclosure is characterized in that in the third aspect, the binarization unit performs a hysteresis operation using two threshold values.

[0253] A communication device according to aspect 5 of the present disclosure is characterized in that in aspect 3 or 4, the detection unit includes a first bit detection unit configured to detect the first bit based on the number of changes in a value in the binary signal.

[0254] A communication device according to aspect 6 of the present disclosure is configured such that, in any one of aspects 2 to 5, the detection unit includes an A / D conversion unit that performs A / D conversion on the signal that has passed through the filter unit.

[0255] In the communication device of form 7 of the present disclosure in form 1, the detection unit includes: an A / D conversion unit that performs A / D conversion on the received signal; a partition signal generating unit that generates a partition signal of a specified time width cut out from the digital signal output by the A / D conversion unit; a frequency component intensity calculation unit that sequentially calculates the intensity of the frequency component corresponding to the first bit in the partition signal for a plurality of the partition signals; and a first bit detection unit that detects the first bit based on time series data of the intensity sequentially calculated by the frequency component intensity calculation unit.

[0256] In the communication device of form 8 of the present disclosure, in any one of forms 1 to 7, the receiving unit further includes: a noise evaluation unit for evaluating the electromagnetic wave intensity of a frequency band including a frequency component corresponding to the first bit and the electromagnetic wave intensity of a frequency band including a frequency component corresponding to the second bit in an environment in which the communication device is installed; a determination unit for determining, based on a result of the evaluation obtained by the noise evaluation unit, whether a high bit or a low bit is allocated to the first bit; and a setting unit for switching the structure of the receiving unit based on a result of the determination obtained by the determination unit.

[0257] In the communication device of form 9 of the present disclosure in form 8, the noise evaluation unit has: a first filter circuit that allows the electric signal of the frequency band including the frequency component corresponding to the first bit to pass through, and reduces the electric signal of the frequency band including the frequency component corresponding to the second bit; and a second filter circuit that allows the electric signal of the frequency band including the frequency component corresponding to the second bit to pass through, and reduces the electric signal of the frequency band including the frequency component corresponding to the first bit.

[0258] In the communication device of form 10 of the present disclosure, in any one of forms 1 to 7, the signal includes a first part corresponding to a preamble code constituted in a plurality of consecutive forms of either high bits or low bits, and the receiving unit further comprises: a determination unit for determining which of the high bit or the low bit is to be allocated to the first bit using at least one of the strength state of the frequency component corresponding to the high bit or the strength state of the frequency component corresponding to the low bit in the first part of the received signal; and a setting unit for switching the structure of the receiving unit based on the result of the determination obtained by the determination unit.

[0259] The communication device of form 11 of the present disclosure includes a receiving unit, which demodulates a signal that is frequency-shift modulated with a binary value of a high bit and a low bit, and the receiving unit has: a high bit detection unit, which detects a high bit from the received signal along a time axis; a low bit estimation unit, which estimates the existence of a low bit based on the length of continuous time during which the high bit detection unit cannot detect the high bit, and outputs a first bit string after temporarily demodulating the signal; a low bit detection unit, which detects a low bit from the received signal along a time axis; a high bit estimation unit, which estimates the existence of a high bit based on the length of continuous time during which the low bit detection unit cannot detect the low bit, and outputs a second bit string after temporarily demodulating the signal; a demodulation unit, which outputs a third bit string after temporarily demodulating the signal from the received signal; and a bit determination unit, which determines the bit string after demodulating the signal by comparing the first bit string, the second bit string, and the third bit string.

[0260] A communication device according to aspect 12 of the present disclosure is one of aspects 1 to 11, wherein the communication device further includes a transmission unit that wirelessly transmits a command to a slave, and the signal is a wireless response from the slave to the command.

[0261] The communication device according to aspect 13 of the present disclosure is, in any one of aspects 1 to 12, an RFID reader.

[0262] The signal demodulation method of form 14 of the present disclosure demodulates a signal that has been frequency-shift modulated with binary values ​​of a high bit and a low bit, and the signal demodulation method includes: a step of detecting a first bit that is either a high bit or a low bit from the signal along a time axis; and a step of inferring the existence of a second bit that is different from the first bit based on the length of continuous time during which the first bit cannot be detected.

[0263] The present invention is not limited to the above-described embodiments and modifications, and various modifications can be made within the scope of the claims. Embodiments obtained by appropriately combining technical components disclosed in different embodiments and modifications are also included in the technical scope of the present invention.

Claims

1. A communication device, comprising a receiving unit, The receiving unit demodulates the signal after frequency shift modulation with the binary values ​​of high bit and low bit. The receiving unit has: a detection unit that detects a first bit that is either a high bit or a low bit from the received signal along a time axis; and The estimating unit estimates the presence of a second bit that is a bit different from the first bit based on the length of a continuous time during which the detecting unit cannot detect the first bit.

2. The communication device according to claim 1, wherein: The detection unit includes a filter unit. The filter unit passes a frequency component corresponding to the first bit in the received signal and reduces a frequency component corresponding to the second bit.

3. The communication device according to claim 2, wherein: The detection unit includes a binarization unit, The binarization unit generates a binarized signal by applying a threshold value related to intensity to the signal that has passed through the filter unit.

4. The communication device according to claim 3, wherein: The binarization unit performs a hysteresis operation using two thresholds.

5. The communication device according to claim 3, wherein: The detection unit includes a first bit detection unit, The first bit detection unit detects the first bit based on the number of changes in the value of the binary signal.

6. The communication device according to claim 2, wherein: The detection unit has an analog / digital conversion unit. The analog / digital conversion unit performs analog / digital conversion on the signal that has passed through the filter unit.

7. The communication device according to claim 1, wherein: The detection unit has: An analog / digital conversion unit, performing analog / digital conversion on the received signal; A partition signal generating unit, which generates a partition signal by cutting out a predetermined time width from the digital signal output from the analog / digital conversion unit; A frequency component strength calculation unit, which sequentially calculates the strength of the frequency component corresponding to the first bit in the partition signal for the plurality of partition signals; as well as The first bit detection unit detects the first bit based on the time series data of the intensity sequentially calculated by the frequency component intensity calculation unit.

8. The communication device according to any one of claims 1 to 7, wherein: The receiving unit also has: a noise evaluation unit that evaluates the electromagnetic wave intensity of a frequency band including a frequency component corresponding to the first bit and the electromagnetic wave intensity of a frequency band including a frequency component corresponding to the second bit in an environment in which the communication device is installed; a determination unit that determines whether a high bit or a low bit is to be allocated to the first bit based on the evaluation result obtained by the noise evaluation unit; as well as The setting unit switches the configuration of the receiving unit based on the result of the determination by the determination unit.

9. The communication device according to claim 8, wherein: The noise evaluation unit includes: a first filter circuit that passes an electrical signal of a frequency band including a frequency component corresponding to the first bit and reduces an electrical signal of a frequency band including a frequency component corresponding to the second bit; and a second filter circuit that passes the electrical signal of a frequency band including the frequency component corresponding to the second bit and reduces the electrical signal of a frequency band including the frequency component corresponding to the first bit.

10. The communication device according to any one of claims 1 to 7, wherein: The signal includes a first portion corresponding to a preamble code composed of a plurality of consecutive high bits or low bits, The receiving unit also has: a determination unit that determines which of the high bit or the low bit is to be allocated to the first bit using at least one of a state of intensity of a frequency component corresponding to the high bit or a state of intensity of a frequency component corresponding to the low bit in the first portion of the received signal; as well as The setting unit switches the configuration of the receiving unit based on the result of the determination by the determination unit.

11. The communication device according to any one of claims 1 to 7, wherein: The communication device further includes a sending unit. The sending unit wirelessly sends a command to the slave. The signal is a wireless response from the slave to the command.

12. A communication device, comprising a receiving unit, wherein the receiving unit demodulates a signal that is frequency-shift modulated using two values ​​of a high bit and a low bit, The receiving unit has: A high bit detection unit detects high bits from the received signal along the time axis; a low bit estimation unit estimates the existence of low bits based on the length of continuous time during which the high bit detection unit cannot detect high bits, and outputs a first bit string after temporarily demodulating the signal; A low bit detection unit detects low bits from the received signal along the time axis; a high bit estimation unit estimates the existence of high bits based on the length of continuous time during which the low bit detection unit cannot detect low bits, and outputs a second bit string after temporarily demodulating the signal; A demodulation unit, outputting a third bit string obtained by temporarily demodulating the received signal from the received signal; as well as The bit determination unit determines a bit sequence obtained by demodulating the signal by comparing the first bit sequence, the second bit sequence, and the third bit sequence.

13. The communication device according to claim 12, wherein: The communication device further includes a sending unit. The sending unit wirelessly sends a command to the slave. The signal is a wireless response from the slave to the command. The communication device according to claim 13 , which is a radio frequency identification reader.

15. A signal demodulation method for demodulating a signal after frequency shift modulation with a binary value of a high bit and a low bit, the signal demodulation method comprising: a step of detecting a first bit as either a high bit or a low bit from the signal along a time axis; and A step of estimating the presence of a second bit that is different from the first bit based on the length of continuous time during which the first bit cannot be detected.

Images