JP3629342B2 - Object identification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an object identification device, and in particular, by attaching a resonance tag including a resonance circuit to a specific object and receiving a signal wave induced in synchronization with the resonance circuit, the object moves within a predetermined area. The present invention relates to an object identification device that automatically detects passing.
[0002]
[Prior art]
For the purpose of preventing theft of merchandise at retail stores, etc., in a predetermined area, a transmitting device that transmits an electromagnetic wave whose frequency is repeatedly swept at a constant frequency in a continuous predetermined frequency band, and a receiving device that receives the electromagnetic wave A resonance tag including a resonance circuit that resonates at a predetermined frequency within the frequency band is attached to a product or the like, and a change in a signal received by the receiving device when the product passes through the area is detected and an alarm is generated. Various object identification devices have been developed.
[0003]
In this type of object identification device, the detection operation is reliably performed only when the object to be identified has passed, and it is not erroneously operated except when the object has passed. In order to suppress the influence of noise as much as possible, it is required to accurately detect only the electromagnetic wave changes that occur when it passes and pick up noise signals that are similar to those when the object has passed. The ingenuity is given.
[0004]
As this type of conventional object identification device, for example, the one described in Japanese Patent Publication No. 55-4275 can be cited. The apparatus described in this publication is configured to divide the receiving coil into two parts to cancel external noises, and to induce currents induced from the transmitting coil to the receiving coil with different in-phase components and π / 2 phases of the transmitting coil current. In comparison with the component, it is automatically deleted, and only the response current from the resonance circuit attached to the object to be identified is taken out to identify the object.
[0005]
Another example of the conventional object identification device is disclosed in Japanese Patent Laid-Open No. 7-249181. The apparatus described in the publication will be described as follows based on FIG. 10 and FIG.
[0006]
As shown in FIGS. 10A to 10C, this conventional object identification device uses a high frequency 54a of, for example, 7 MHz to 9 MHz, which is FM-modulated by a low frequency 53a output from a high frequency transmission device (OSC) 52. The power is amplified by the amplifier 55, and electromagnetic waves are transmitted from the transmitter antenna 60 toward the receiver antenna 70.
[0007]
The receiving unit 61 receives the electromagnetic wave transmitted from the transmitting unit antenna 60 with the receiving unit antenna 70, and takes out the high frequency 54a of the target frequency of, for example, 7 MHz to 9 MHz by tuning 63, as shown in FIG. On the other hand, a waveform that is synchronized with the waveform of the low-frequency transmission 53a demodulated by the FM demodulation 64 is shaped 67 to obtain a synchronized waveform 67a. On the other hand, the AM demodulation 65 is performed, and the change in the intensity of the electromagnetic wave is monitored by the level detection 66. If the signal level exceeds an arbitrary predetermined strength level, a signal is present. The signal waveform 68a is obtained as “none”. Further, the sampling timing of the arithmetic unit 69 is synchronized with the synchronous waveform 67a, and the signal waveform 68a corresponding to one period of the synchronous waveform 67a is monitored at each sampling timing, so that one period is included in the arithmetic unit 69. The binary frequency distribution of minutes is stored in the storage device 69M. By repeating this operation, information on a large number of binary frequency distributions is increased to generate a frequency spectrum distribution, thereby enabling arithmetic processing.
[0008]
The detection plate 56 as a specimen attaches a resonance circuit shown in FIG. 11A, which is tuned in a range of frequencies transmitted and received in the apparatus, to a product or the like. In addition, this apparatus includes a passage sensor 80 that senses passage of the specimen, a detection unit 81 thereof, and an output device 71 that outputs based on the calculation result of the calculation device 69.
[0009]
In any of the conventional techniques described above, a single resonance circuit such as the equivalent circuit shown in FIG. 11A is employed as a resonance circuit attached to an object to be identified. Signal processing by the receiver when such a single resonance circuit is present in a predetermined detection region of the object identification device is described as follows with reference to the time chart of FIG. The signal received by the receiver passes through a predetermined filter and is amplified, and only a high frequency component of a desired signal spectrum shown in FIG. 12A is input to a circuit for signal processing.
[0010]
The signal (a) in the time chart of FIG. 12 shows how fluctuation occurs due to the presence of a single resonance tag in the vicinity of one resonance point f1 (fmin <f1 <fmax) of the single resonance tag. . When this signal (a) exceeds predetermined positive and negative thresholds th1 and th2, a positive pulsed rectangular wave is output as shown in FIGS. 12 (c) and 12 (d). The passage of the object attached with is detected. FIG. 12B shows a frequency sweep of one cycle (fmax → fmin → fmax) of a transmission signal transmitted from the transmitter side of the object identification device.
[0011]
[Problems to be solved by the invention]
However, both of the conventional techniques described in the above two publications have the following problems because the resonant circuit attached to the object to be identified is a single resonant circuit that resonates only at a single frequency. It was.
[0012]
First, a received signal for detecting whether or not an object to be identified passes is generally input to an arithmetic processing means as a wideband signal that has passed through a predetermined bandpass filter, and is subjected to signal processing. The noise in the band is input unconditionally. For example, when high-frequency noise having a repetition period close to the sweep frequency is received, it may be determined that the object to be identified has passed, and a malfunction is relatively likely to occur.
[0013]
Also, if an object having resonance characteristics similar to the resonance circuit attached to the object to be identified exists in the vicinity of the antenna of the object identification device, an alarm is issued even though the object to be identified has not passed. Will cause a malfunction. For example, a slide door having a metal frame, a copper wire wound in a coil shape, or the like may have a resonance frequency similar to a resonance tag attached to a product or the like, and is likely to cause such a malfunction.
[0014]
Thus, in a conventional object identification device that detects the passage of an object using a resonance tag having a single resonance frequency within the sweep frequency, noise having a frequency that approximates the resonance frequency of the resonance tag, or the resonance tag When there is an object with similar resonance characteristics to the above, malfunction cannot be essentially prevented, and such malfunction occurs to a degree that cannot be ignored.Therefore, there is a problem that reliability as an object identification device is lacking. It was.
[0015]
In order to solve the above-described conventional problems, an object of the present invention is to provide a highly reliable object identification device that prevents occurrence of malfunction due to noise.
[0016]
[Means for Solving the Problems]
The object recognition apparatus of the present invention that achieves the above object includes a transmitting unit that transmits an electromagnetic wave having a frequency repeatedly swept at a constant period in a predetermined continuous frequency band, and a receiving unit that receives the electromagnetic wave transmitted from the transmitting unit. A resonance means attached to an object to be identified and resonating at a plurality of different frequencies within the predetermined frequency band within which the electromagnetic wave transmitted from the transmission means is swept, and the object between the transmission means and the reception means. And identifying means for identifying the passage of the object by detecting changes in the received signal of the receiving means at a plurality of resonance frequencies of the resonance means.
[0017]
With such a configuration, according to the present invention, since the resonance means that resonates at a plurality of different frequencies is used, the malfunction that has been a problem in the conventional example can be essentially prevented for the following reason. First, in the case of using a single resonance circuit as in the conventional example above, it is not negligible that noise that approximates the resonance frequency or an object having resonance characteristics similar to that of the resonance circuit exists by chance. Probability occurs, and in the conventional apparatus, the probability is directly related to the degree of malfunction. However, there is a very low probability that noise having a frequency approximating a plurality of different resonance frequencies or an object having resonance points approximating a plurality of different resonance frequencies at the same time exists in the vicinity of the object identification device.
[0018]
Therefore, as in the device of the present invention, when the resonance tag having a plurality of different resonance frequencies is attached to the object to be identified and the resonance has been detected at all the different resonance frequencies, the object has passed. By making the determination, it is possible to essentially prevent the malfunction that has occurred in the conventional example.
[0019]
In addition, since it is possible to realize a highly reliable object identification device that does not malfunction, it is not necessary to set a price that anticipates maintenance when a malfunction occurs, so that the selling price of the device can be significantly reduced.
[0020]
Of the present invention The identification means of the object identification device is , Received By determining the magnitude relationship between the filter that passes only the signal within the predetermined frequency band of the signals received by the transmission means and the set threshold value for the signal that has passed through this filter, the predetermined numerical value is obtained. Decode value output means for decoding in time series, and whether the time-series arrangement of numerical values decoded by the decode value output means matches the time-series arrangement of decode values when the object exists in a predetermined area Discriminating means for discriminating whether or not.
[0021]
Also, Of the present invention The decoded value output means is , Send Means for decoding the numerical value by applying a predetermined weight according to the sweep direction of the frequency of the electromagnetic wave transmitted by the transmitter and the positive / negative of the set threshold value.
[0022]
In this way, by performing predetermined weighting when outputting decoded values, it becomes easier to obtain a time-series arrangement of decoded values according to the complex characteristics of the signal waveform when using a resonance tag having a plurality of resonance frequencies. This makes it possible to more reliably identify the signal waveform due to the influence of noise or the like.
[0023]
The discriminating means includes a plurality of periods of frequency sweeps of electromagnetic waves transmitted by the transmitter in a number of periods equal to or greater than a predetermined ratio in a time-series array of numerical values decoded by the decoded value output means. And determining means for determining that the object exists in the predetermined area when it is detected that the object coincides with a time-series arrangement of decode values when the object exists in the predetermined area. Good. By including such a discriminating unit, even if an error occurs in the time series arrangement of the decoded values output from the decoded value output unit due to the influence of noise, the discriminating unit is prevented from malfunctioning. Reliability is improved.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an object identification device according to an embodiment of the present invention. The object identification apparatus according to the present embodiment shown in FIG. 1 receives a transmitter 1 that oscillates and transmits a high-frequency electromagnetic wave, receives the electromagnetic wave transmitted from the transmitter 1, performs predetermined signal processing, and A receiver 2 that identifies an object by performing an operation, and a two-resonance tag 3 that is attached to the object to be identified and has a resonance circuit that resonates at two frequencies within the range of transmission frequencies transmitted by the transmitter 1; It has. The transmitter 1 is provided with a transmitting antenna 10, and the receiving unit 2 is provided with a receiving antenna 20. The transmitting antenna 10, the receiving antenna 20, and the two-resonance tag 3 are extremely small compared to the wavelength of the electromagnetic wave signal in free space. Since both of these include coils (or loops), when the two-resonance tag 3 exists in a predetermined region between the transmitter 1 and the receiver 2, they are in an electrically coupled state. .
[0025]
In the object identification device of the present embodiment, transmitter 1 synthesizes an FM-modulated signal with a period of 100 Hz, for example, in the range of 7 MHz to 9 MHz, and transmits the signal from transmitting antenna 10 as an electromagnetic wave. . The electromagnetic wave transmitted from the transmitting antenna 10 is received by the receiving antenna 20, and predetermined signal processing and calculation are performed on the received signal by the receiver 2. When an object with the two-resonance tag 3 attached is present in a predetermined region between the transmitter 1 and the receiver 2, the receiver 2 detects resonance at two resonance frequencies of the resonance circuit of the two-resonance tag 3. And the object is identified.
[0026]
The transmitter 1 includes an oscillator 11, a voltage controlled wave oscillator 12, and an amplifier 13, as shown in a detailed block diagram in FIG. The oscillator 11 generates a sine wave signal of 100 Hz, for example. In the voltage controlled wave oscillator 12, for example, FM modulation of about ± 10% around 8 MHz is synthesized using the sine wave signal from the oscillator 11. The synthesized FM modulated signal is sent to the transmitting antenna 10 via the amplifier 13.
[0027]
FIG. 3 shows a detailed block diagram of the receiver 2. The electromagnetic wave signal transmitted from the transmitting antenna 10 is received by the receiving antenna 20 and enters the amplifier 22 through the RF band pass filter 21. The output of the amplifier 22 is sent to the detector 23 and further passes through the low pass filter 24 and the high pass filter 25. The low pass filter 24 removes the carrier wave component and the high frequency noise. The signal that has passed through the low-pass filter 24 passes through the high-pass filter 25, so that only the high-frequency component in the signal spectrum passes. The signal that has passed through the high-pass filter 25 is sent to the tag signal identification means 27 through the amplifier 26.
[0028]
The signal sent to the tag signal identification means 27 via the amplifier 26 has the waveform shown in FIG. 7B when the two-resonance tag 3 is used as in this embodiment. That is, when a resonance circuit including a resonance circuit having only one resonance point is used as in the conventional example, the signal waveform shown in FIG. 7A is 9 MHz to 7 MHz and vice versa, 7 MHz to 9 MHz. In this embodiment using the two resonance tags 3, as shown in FIG. 7B, the resonance signal appears only once during each frequency sweep of 9 MHz to 7 MHz and vice versa 7 MHz. The resonance signal appears twice during each frequency sweep from 1 to 9 MHz.
[0029]
Next, details of the two-resonance tag 3 used in the present embodiment will be described with reference to FIGS. As shown in FIG. 4A, the two-resonance tag 3 includes two resonance circuits 3a and 3b. These resonance circuits 3a and 3b are adjusted so that, for example, one resonance circuit 3a resonates with an electromagnetic wave signal of 8.2 MHz and the other resonance circuit 3b resonates with an 7.5 MHz electromagnetic wave signal.
[0030]
As shown in FIGS. 4A and 4B, each of the resonance circuits 3a and 3b has a flat spiral conductor 32 on the surface of a substrate 31 made of a thin plastic layer, and an inner side of the spiral conductor 32. Conductor plates 33, 34 formed on the front and back sides of the substrate 31, and a conductor plate 35 formed on the front and back sides of the substrate 31, on the outer side (lower side in the drawing) of the spiral conductor 32. , 36 are formed. 5 (a) and 5 (b) show the Va-Va line cross section and the Vb-Vb line cross section shown in FIGS. 4 (a) and 4 (b), respectively.
[0031]
FIG. 6 shows an equivalent circuit of the resonance circuit of the two-resonance tag 3, and the spiral conductor 32 is the inductor L of FIG. ₁ , L ₂ In addition, the capacitor composed of the conductive plates 33 and 34 is the capacitor C in FIG. ₁ , C ₂ In addition, the capacitor composed of the conductive plates 35 and 36 is the capacitor C in FIG. ₃ , C ₄ Correspond to each.
[0032]
Next, with reference to the time chart shown in FIG. 8, signal processing in the tag signal identification unit 27 of the object identification device of the present embodiment will be described. 8A shows a waveform corresponding to the signal waveform shown in FIG. 7B, and FIG. 8B shows a frequency sweep transmitted by the voltage controlled oscillator 12 of the transmitter 1. FIG. In each case, the horizontal axis is a time axis. In the signal (a), the carrier wave component and the high-frequency noise are removed by the low-pass filter 24, and only the high-frequency component of the signal spectrum passes through the high-pass filter 25, and then amplified by the amplifier 26 and input to the tag signal identification unit 27. It is a waveform of a signal, and shows a state in which fluctuation occurs due to the presence of the two-resonance tag 3 in the vicinity of two resonance points f1 and f2 (fmin <f1, f2 <fmax) of the two-resonance tag 3. . (A) In an ideal state where a signal other than a high frequency caused by fluctuation due to the presence of the two-resonance tag 3 is completely removed by the low-pass filter 24 and the high-pass filter 25, the two-resonance tag 3 is When it does not exist in the vicinity, it becomes a flat signal of the ground level.
[0033]
(B) of the time chart shown in FIG. 8 shows a frequency sweep of one cycle (fmax → fmin → fmax) of the transmission signal transmitted from the transmitter 1. 8 (c) to 8 (f) show the first half of the signal processing in the tag signal identification means 27. The signal shown in (c) in the middle stage is fmax to fmin in the frequency sweep shown in (b). An inverted signal of P (positive) is given during the period of time N, and N (reverse) is given during the period of time from fmin to fmax. The signal (d) is the signal of (a) of Comparator output with positive threshold th2, signal (e) is signal (a) Negative of Is a comparator output with a threshold value th1. Further, (f) in the time chart of FIG. 8 is a decoded value output with a predetermined weighting based on the output signals (c) to (e).
[0034]
The correlation between the output of the decoded value (f) in the time chart of FIG. 8 and the signals (c) to (e) is as follows. First, when the signal (c) is P (positive) and the signals (d) and (e) are both zero, a decoded value of “0” is output. In a state where the signal (c) is P (positive) and the signal (a) exceeds the threshold th2, that is, the signal (d) is positive and the signal (e) is zero, the weighted decoded value “2” Is output. When the signal (c) is P (positive) and the signal (a) exceeds the threshold th1, that is, when the signal (d) is zero and the signal (e) is positive, the decode value “1” is Is output.
[0035]
When the signal (c) is N (reverse), if both the signals (d) and (e) are zero, the decode value is “4”, that is, the signal (a) exceeds the threshold th2, ie, the signal When (d) is a positive output state of a pulsed rectangular wave and the signal (e) is zero, the weighted decode value is “6”, Threshold th1 When the signal exceeds the value, that is, when the signal (d) is zero and the signal (e) is a positive output of a pulsed rectangular wave, the decode value “5” is output. That is, the decode value when the signal (c) is N (reverse) is the same as the signal waveform of (a) when the signal (c) is P (positive) with respect to the threshold values th1 and th2. It is a numerical value obtained by adding “4” to a decoded value at a certain time.
[0036]
In this way, when the object attached with the two-resonance tag 3 passes through the vicinity of the area between the transmitter 1 and the receiver 2, the numerical value shown in the lower part (f) of FIG. Decoding is repeatedly performed in time series, with the period during which the frequency of the electromagnetic wave is swept as fmax → fmin → fmax as one period. Only when it is determined that the series of decoded values are output in this order, the tag signal identification unit 27 detects the passage of the two-resonance tag 3 by the state change shown in the state diagram of FIG.
[0037]
Next, signal processing in the state diagram of FIG. 9 will be described. S0 to S15 in the state diagram of FIG. 9 identify the respective decode values with the correspondence shown in the lower part (f) of FIG. First, if a state in which no signal is input continues for a certain time, the signal is reset to S0. If it is determined that the input signals by the comparators 2 and th2 are “0”, that is, the noise level, the signal is stopped at S0. ing. If the input signal is “2”, that is, if there is a comparator output weighted as “2”, the process proceeds from S0 to the next S1.
[0038]
The signal identification operation in S1 is as follows. When the input signal is “1”, that is, when there is an output from the comparator 1 and th1 weighted as “1”, the process proceeds from S1 to S2. When the input signal is other than “1” and there is no output from the comparators 1 and th1, that is, when it is determined that the level is a noise level or the P / N determination is P, the process stops at S1. If the P / N discrimination is N, the process returns to S0.
[0039]
Thereafter, the same signal discriminating operation is sequentially performed in S2 to S15, and if proceeding to S15, it is determined that the tag signal has been detected. In S3 and S11, in order to extract the feature that the signal waveform of FIG. 8A is depressed and becomes 0 in the middle of the two resonance points of the two-resonance tag 3, the output is caused by the feature. The decoded values “0” and “4” are discriminated. In the present embodiment, except for S3 and S11, the determination of the states of the decode values “0” and “4” is omitted, but by adding a state for determining the state of these decode values. The accuracy of the discrimination operation can be increased. In S7 and S15, the signal (c) in the time chart of FIG. 8 identifies the inversion from P (forward) to N (reverse) and the inversion from N (reverse) to P (forward), respectively.
[0040]
The determination operation shown in the state diagram of FIG. 9 can be realized by a gate array. Various detection methods other than the state diagram shown in FIG. 9 can be used to detect the passage of the two-resonance tag 3, but if a gate array is used, discrimination control can be easily and inexpensively changed by changing the program. It can be replaced with the method.
[0041]
In the above embodiment, the detection operation based on the decode value for one cycle has been described. However, if only one detection based on the decode value for one cycle has an error in the decode value, In order to avoid the inconvenience that the passage of the two-resonance tag 3 is not detected, a detection operation is performed based on a change in state for a predetermined period of a predetermined plurality of cycles. Only when a decoded value corresponding to passage is output, it can be set to determine that the two-resonance tag 3 has passed. By such a detection method, there is an advantage that even if an error occurs in the decoded value in the remaining 30% cycle, the passage of the two-resonance tag 3 is not missed. Normally, it takes at least 0.1 second or more for a person with an object such as a product to pass through the detection operable region between the transmitter 1 and the receiver 2 of the object identification device in the present embodiment. Therefore, when the frequency sweep is performed at 100 Hz, a decode value of 10 cycles or more is output within the time for one two-resonance tag 3 to pass. In this case, for example, it is possible to set so that it is determined that the two-resonance tag 3 has passed only when a decode value corresponding to the passage of the two-resonance tag 3 is output for seven or more times out of ten times.
[0042]
As described above, according to the object identification device of the present embodiment, by using the two-resonance tag 3, it is possible to suppress the influence of noise when identifying an object. Even if the threshold value is set relatively low, it is possible to maintain a certain level of reliability. As a result, the detection sensitivity of the object identification device can be improved.
[0043]
Another feature of the present embodiment is that the object is identified using frequency modulation that is swept with fmax → fmin → fmax as one period, that is, frequency sweeping in one continuous frequency band. is there. A plurality of resonance tags each having discretely different resonance frequencies are attached to a moving body to be identified, and a plurality of types of radio waves having predetermined frequencies corresponding to those resonance frequencies are transmitted to determine the presence of the plurality of resonance tags. A moving body identification device for detection is disclosed in Japanese Patent Laid-Open No. 2-198382. However, this conventional apparatus uses the two resonance tags of this embodiment in that a plurality of resonance tags are used to individually identify a plurality of types of moving objects based on a combination of resonances detected by a plurality of resonance tags. It is different from the apparatus of this embodiment in that it uses a tag and has a different purpose, and also requires a plurality of oscillators to transmit radio waves of a plurality of types of discrete frequencies.
[0044]
As in the object identification device of the present embodiment, by identifying an object using a frequency sweep of one continuous frequency band, it is possible to avoid a frequency band used in various communication fields, etc. There is a unique advantage that cannot be obtained by the apparatus disclosed in Japanese Patent Laid-Open No. 2-198382, in which a preferable frequency band with less influence can be easily selected.
[0045]
In the above embodiment, the two-resonance tag 3 is used as the resonance circuit attached to the object to be identified. However, the sweep frequency band of the oscillator 1 is within a range that can be disassembled for signal processing in the receiver 2. It is also possible to use a resonance tag that resonates at three or more frequencies. As the number of resonance points of the resonance tag increases, the probability of malfunction caused by the presence of another object having the same resonance point decreases, so that the influence of noise can be further suppressed.
[0046]
Further, the scope of the present invention is not limited to the disclosed contents of the above-described embodiment, and all modifications within the equivalent scope are included in the description of the claims.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a configuration of an object identification device according to an embodiment of the present invention.
2 is a block diagram showing a detailed configuration of a transmitter 1 of the apparatus shown in FIG. 1. FIG.
3 is a block diagram showing a detailed configuration of a receiver 2 of the apparatus shown in FIG. 1. FIG.
4A is a diagram showing details of the front surface of the two-resonance tag 3 used in an embodiment of the present invention, and FIG. 4B is a diagram showing details of the back surface of the two-resonance tag 3; .
5A is a view showing a cross section of the Va-Va line of the two-resonance tag 3 shown in FIGS. 4A and 4B, and FIG. 5B is a two-resonance shown in FIGS. 4A and 4B; It is a figure which shows the Vb-Vb line | wire cross section of the tag 3. FIG.
6 is an equivalent circuit diagram of the two-resonance tag 3 shown in FIGS. 4 and 5. FIG.
7A is a signal waveform of a signal sent to a tag signal identification unit via an amplifier when a resonance circuit including a resonance circuit having only one resonance point as in the conventional example is used; FIG. ) Is a diagram showing a signal waveform of a signal sent to the tag signal identification unit 27 via the amplifier 26 when the two-resonance tag 3 is used in the embodiment of the present invention.
FIG. 8 is a time chart for explaining a signal processing method in tag signal identification means 27 of the object identification device of one embodiment of the present invention.
9 shows the tag signal identification means 27 of the object identification device according to the embodiment of the present invention, based on the decoded value obtained as a result of the signal processing shown in FIG. It is a state diagram which judges that it detected.
10A is a diagram showing an outline of a conventional object identification device described in Japanese Patent Laid-Open No. 7-249181, FIG. 10B is a detailed block diagram of a transmission unit 51 shown in FIG. 10A, and FIG. FIG. 4 is a detailed block diagram of the receiving unit 61 shown in FIG.
11A is an equivalent circuit diagram of a resonance circuit of a single resonance tag used in the conventional object identification device described in JP-A-7-249181 shown in FIG. 10, and FIG. FIG.
12 is a time chart for explaining a signal processing method in the conventional object identification device described in Japanese Patent Laid-Open No. 7-249181 shown in FIG.
[Explanation of symbols]
1 Transmitter
2 receivers
3 2 resonance tag
3a, 3b resonant circuit
10 Transmitting antenna
20 Receiving antenna
27 Tag signal identification means
28 Alarm
31 substrates
32 Spiral conductor
33, 34, 35, 36 Conductor plate

Claims (2)

A transmission means for transmitting an electromagnetic wave whose frequency is repeatedly swept at a constant period in a predetermined continuous frequency band, a reception means for receiving an electromagnetic wave transmitted from the transmission means, and an object to be identified and attached to the transmission The resonance means that resonates at a plurality of different frequencies within the predetermined frequency band in which the electromagnetic wave emitted from the means is swept, and the object are in a predetermined region between the transmission means and the reception means An identification means for identifying the passage of the object by detecting a change in a reception signal of the reception means at a plurality of resonance frequencies of the resonance means ;
The discriminating unit discriminates a magnitude relationship between a filter that passes only a signal within a predetermined frequency band among signals received by the receiving unit and a threshold value that is set for the signal that has passed through the filter. Decode value output means for decoding a predetermined numerical value in time series, and a time-series arrangement of numerical values decoded by the decode value output means, the decode value when the object is present in the predetermined area Discriminating means for discriminating whether or not it matches the time-series arrangement of
The decoded value output means includes means for decoding numerical values by performing predetermined weighting according to the sweep direction of the frequency of the electromagnetic wave transmitted by the transmitter and the positive / negative of the set threshold value. . The discriminating means has a number of periods equal to or greater than a predetermined ratio in a time-series arrangement of numerical values decoded by the decoded value output means for a plurality of periods of frequency sweeping of electromagnetic waves transmitted by a transmitter. And a means for determining that the object exists in the predetermined area when it is detected that the object coincides with a time-series arrangement of decode values when the object exists in the predetermined area. 2. The object identification device according to 1.

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