JPH08263757A - Shoplifting preventing device - Google Patents

Abstract

PURPOSE: To report the generation of shoplifting by detecting the signal level of a received signal at intervals of a prescribed time within the same detection period as the frequency change period of a detection signal and detecting matching between the change pattern of the detected signal level and a set article detecting pattern. CONSTITUTION: The signal level of a received signal from a receiving antenna 5 of a receiver 7 is successively inputted as level data at the same period as the sweeping period of a detection signal transmitted from a transmitting antenna 1 of a transmitter 3 at intervals of a prescribed time in the sweeping period of each transmitting period and stored in a RAM in a CPU 21. The CPU 21 averages the level data for plural sweeping periods stored in the RAM every frequency and generates average data. Then the CPU 21 judges whether the change pattern of the average data matches a tag pattern obtained at the time of arranging merchandise M between the antennas 1, 5 or not. Thus the existence of the merchandise M, i.e., shoplifting is reported.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing shoplifting, and in particular, a resonance circuit having a predetermined resonance frequency as an object to be detected is previously attached to a product or the like, and the resonance circuit is used as a doorway or the like. The present invention relates to a shoplifting prevention device that electrically detects the existence of a shoplifting action and notifies the occurrence of shoplifting.

[0002]

2. Description of the Related Art Conventionally, as this type of device, for example, a transmitting antenna and a receiving antenna are installed on both sides of a doorway of a library or a store that sells a predetermined product, and the device is preliminarily attached to a rental item or a product. A detection signal of the same frequency as the resonance frequency of the resonance circuit (object to be detected) is constantly sent from the transmission antenna, the signal level of the reception signal from the reception antenna is detected, and the occurrence of shoplifting is detected. It has been put to practical use. That is, in this type of device,
Resonant circuits attached to products resonate, and there are products with resonant circuits attached between the transmitting antenna and the receiving antenna based on the level change of the received signal accompanying absorption and release of the energy of the transmitted signal. When the presence of the shoplifter is detected, a buzzer is sounded or a lamp is lit to detect the occurrence of shoplifting.

[0003]

However, in general,
In this type of anti-shoplifting device, the resonance frequency of the resonance circuit attached to the product varies due to manufacturing. Therefore, in order to reliably detect the presence (shoplifting) of the resonance circuit, the frequency of the detection signal sent from the transmitting antenna Are swept in a predetermined frequency range, and the receiving side receives signals in the entire frequency range and judges from the signal level whether there is a product or shoplifting. ing.

Therefore, in the conventional shoplifting prevention device, when a signal within the same frequency band as the detection signal for shoplifting detection (pulse noise, a transmission signal from another transmission device, etc.) enters from the outside, the signal of the received signal is received. There has been a problem that the level fluctuates greatly, and as a result, even persons who are not shoplifters are notified of the occurrence of shoplifting.

The present invention has been made in view of these problems, and an object of the present invention is to provide a shoplifting prevention device capable of always accurately detecting and notifying the occurrence of shoplifting.

[0006]

SUMMARY OF THE INVENTION The present invention as set forth in claim 1 made in order to achieve the above object, according to the present invention, is a transmitting antenna and a receiving antenna installed at predetermined intervals as illustrated by a solid line in FIG. Transmission means for transmitting a detection signal of a predetermined frequency from the transmission antenna, frequency control means for periodically changing the frequency of the detection signal in the transmission means within a predetermined frequency range, and reception from the reception antenna Article detection means for detecting the presence of an article having a resonance circuit whose resonance frequency is set within the frequency range between the transmitting antenna and the receiving antenna based on the signal level of a signal, and the article detection In the shoplifting prevention device, a notification means for notifying that the presence of the article has been detected by means is provided. The level detection means for detecting the signal level of the received signal in the same detection cycle as the frequency of the detection signal is changed, and at predetermined time intervals in each detection cycle, and the level detection means. It is determined whether or not the change pattern of the signal level in the detection cycle detected by the item detection pattern matches a preset article detection pattern,
When the change pattern of the signal level matches the article detection pattern, it is determined that the article is present between the transmitting antenna and the receiving antenna, and a determining unit that operates the notifying unit, It is characterized by having.

Next, the invention according to claim 2 is, in the shoplifting prevention device according to claim 1, as illustrated by the dotted line in FIG. 1, the article detecting means is further detected by the level detecting means. Storage means for sequentially storing the signal levels and a signal level for a predetermined detection cycle stored in the storage means, and an average value for calculating the average value of the signal levels detected at the same point in each detection cycle. And a determination unit that determines the presence of the article by sequentially taking in the average value for each point within the detection cycle calculated by the average value calculation unit as the signal level of the received signal. It is characterized by doing.

Further, the invention described in claim 3 is, in the shoplifting prevention device according to claim 1 or claim 2, as illustrated by the alternate long and short dash line in FIG. The signal level for each point is compared with two preset upper and lower determination levels of magnitude, respectively, to determine whether the received signal exceeds the upper determination level within the detection cycle. Upper / lower point detecting means for respectively detecting lower points which have become smaller than the lower determination level, and the number of upper and lower points detected by the upper / lower point detecting means in the detection cycle. And a pattern determination means for determining whether the change pattern of the signal level within the detection cycle matches a preset article detection pattern from the array state thereof. And butterflies.

Furthermore, the invention according to claim 4 is the same as that shown in FIG.
4. In the shoplifting prevention device according to claim 3, as illustrated by a chain double-dashed line in FIG. 5, the determination means further determines a region in which the upper point and the lower point are consecutive at a predetermined frequency within the detection period for pattern determination. Of the upper and lower points in the area set by the determination area setting means and the arrangement state thereof, and the pattern determination means sets the area within the detection cycle. It is characterized in that it is determined whether or not the change pattern of the signal level of (3) matches a preset article detection pattern.

[0010]

In the shoplifting prevention device according to the first aspect of the present invention configured as described above, the transmitting antenna and the receiving antenna are installed with a predetermined space therebetween, and the transmitting means is provided with a predetermined distance from the transmitting antenna. A frequency detection signal is transmitted, and the frequency control means causes the transmission means to periodically change the frequency of the detection signal within a predetermined frequency range. And
Article detection means, based on the signal level of the received signal from the receiving antenna, between the transmitting antenna and the receiving antenna,
The presence of an article having a resonance circuit whose resonance frequency is set within the frequency range is detected, and the notification unit notifies that the article detection unit detects the presence of the article.

In detecting the presence of an article (in other words, shoplifting) by the article detection means, first, the level detection means detects the same period as the cycle in which the frequency of the detection signal is changed by the frequency control means. The signal level of the received signal from the receiving antenna is detected in a cycle and at a predetermined time interval within each detection cycle, and the determination means detects the change pattern of the signal level in the detected detection cycle in advance. It is determined whether or not it matches the set article detection pattern, and when the signal level change pattern matches the article detection pattern, it is determined that an article exists between the transmitting antenna and the receiving antenna. To do.

That is, in the shoplifting prevention device of the present invention, the signal level of the received signal is detected at predetermined time intervals within the same detection cycle as the frequency change cycle of the detection signal, and the change pattern of the detected signal level is detected in advance. When the article detection pattern matches the set article detection pattern, it is determined that there is an article having a resonance circuit between the transmitting antenna and the receiving antenna, and the notifying means notifies the fact.

Therefore, according to the shoplifting prevention device of the present invention,
Even if a signal within the frequency range in which the frequency of the detection signal is changed (pulse noise, etc.) enters from the outside, the presence of the article, in other words, the occurrence of shoplifting, is not affected by the signal and is always detected. It can be accurately detected and notified.

Next, in the shoplifting prevention device according to claim 2, in detecting the presence of an article (shoplifting act) by the article detection means, first, the level detection means causes the shoplifting prevention device according to claim 1. Similarly, the signal level of the received signal is detected, and the detected signal level is sequentially stored in the storage means. Then, the average value calculation means reads out the signal level for a predetermined detection period stored in the storage means,
The average value of the signal levels detected at the same point in each detection cycle is calculated, and the determination means calculates the average value for each point in the detection cycle calculated by the average value calculation means as the signal of the received signal. The levels are sequentially taken in and the existence of goods (shoplifting) is judged.

That is, for example, the signal level of the received signal within one detection cycle detected by the level detection means at a predetermined time interval is used as it is, and the change pattern of the signal level within the detection cycle is recognized, which is an article. When it is determined whether or not it matches the detection pattern, compared to a conventional device that determines the presence of an article simply by whether the signal level of the received signal is higher (or lower) than the reference level for determining the article. For example, the detection accuracy of the article (in other words, the detection accuracy of the shoplifting act) can be sufficiently improved.

However, when the input signal from the outside is pulse noise and its frequency characteristic is close to the resonance characteristic of the resonance circuit provided in the article, the existence of the article is erroneously determined from the pulse noise. It is possible to lose it. Therefore, in the present invention, the change pattern of the signal level of the received signal within the detection period is not recognized by using the signal level of the received signal within one detection period detected by the level detection means as it is, but the level detection is performed. The signal level detected by the means is sequentially stored in the storage means, and the signal level of each point detected at a predetermined time interval in each of a plurality of detection cycles is extracted from the stored signal level. ,
By calculating the average value of each signal level and using that average value as the signal level of the received signal for change pattern recognition, when pulse noise with a frequency characteristic similar to the article detection pattern is input from the outside, The signal level for changing pattern recognition is prevented from changing according to the pulse noise.

Therefore, according to the present invention, as compared with the shoplifting prevention device according to claim 1, the accuracy of detecting the shoplifting action can be further improved, and the occurrence of the shoplifting action can be notified extremely accurately. It will be possible. Next, in the shoplifting prevention device according to claim 3, in determining the existence (shoplifting act) of the article by the determining means, first, the upper / lower point detecting means determines a predetermined time interval within the detection cycle. The received signal exceeds the upper determination level within the detection cycle by comparing the signal level for each point detected in step 2 with the preset upper and lower determination levels of magnitude 2 and lower respectively. Each of the upper points and the lower points that have become smaller than the lower determination level is detected, and the pattern determining means detects the number of the detected upper points and the lower points in the detection cycle and the arrangement state thereof from the detection cycle. It is determined whether or not the change pattern of the signal level inside matches the preset article detection pattern.

That is, according to the present invention, the signal level of the received signal is determined from the number of points where the received signal exceeds the upper determination level, the number of points where the received signal is smaller than the lower determination level, and the arrangement state thereof within one detection cycle. By grasping the characteristic of the change and determining whether or not the characteristic of the change matches the characteristic of the article detection pattern, the existence of the article and eventually the shoplifting action are determined.

Therefore, according to the present invention, in determining whether or not the change pattern of the signal level of the received signal matches the article detection pattern, the signal level of the received signal between the points in one detection cycle is determined. Calculate the deviation of
It is not necessary to analyze the change pattern, and the pattern determination can be easily performed.

Furthermore, in the shoplifting prevention device according to the fourth aspect, in determining the existence of goods (shoplifting act) by the determining means, first, the upper / lower point detecting means,
Similar to the device according to claim 3, the upper point and the lower point are detected within one detection cycle, and the detection result is input to the determination area setting means, and the determination area setting means causes detection within the detection cycle. Then, an area where the upper point and the lower point are continuous at a predetermined frequency is set as an area for pattern determination. Then, the pattern determination means, from the number of the upper point and the lower point in the set area and the arrangement state thereof, the change pattern of the signal level in the detection cycle matches the preset article detection pattern. Determine whether or not.

That is, in a region where the signal level of the received signal within the region from the lower determination level to the upper determination level is continuous within one detection period, the points are continuously transmitted from the transmitting means side to the receiving antenna. It is considered that the detection signal is input as it is, and if the arrangement state of the lower side point and the upper side point including this area is determined (for example, the state in which the upper side point and the lower side point alternately occur), Since the determination time becomes long and an erroneous determination may occur, in the present invention, by setting only the area where the upper point and the lower point occur at a predetermined frequency as the area for pattern determination,
The existence of goods, and hence the occurrence of shoplifting, can be determined at high speed and with high accuracy.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 is a block diagram showing the configuration of the shoplifting prevention device of the embodiment. As shown in FIG.
The shoplifting prevention device of this embodiment has a predetermined resonance frequency f0 (f0 = 8.23 MH in this embodiment) in a store selling video tapes, music compact discs, and the like.
The product M to which the L-C resonance circuit Ma having z) is attached in advance detects that the product M has passed near a specific entrance / exit, and notifies the occurrence of shoplifting. A pair of transmitting antenna 1 and receiving antenna 5, which are installed at a distance of 1.8 m), and a resonance circuit Ma.
Predetermined frequency range f1 to f2 including the resonance frequency f0 (in this embodiment, f1 = 7.38 MHz to f2 = 9.07 MH)
z) the transmitting device 3 for sending out the detection signal swept from the transmitting antenna 1, and the receiving device 7 for detecting and informing the occurrence of shoplifting action based on the received signal from the receiving antenna 5.
It consists of and. The resonance circuit Ma is attached to the product M after being formed on a dedicated tag called a tag, a price tag of the product, or the like.

The transmitter 3 has a predetermined frequency range (f1 to f1) according to a microcomputer (hereinafter, simply referred to as CPU) 9 including a CPU, a ROM, a RAM, etc., and frequency data (digital data) output from the CPU 9. f2)
Direct digital synthesizer (hereinafter, simply referred to as DDS) 11 that outputs a sine wave signal of
A low-pass filter (LPF) 13 that removes unnecessary harmonic components from the output signal of, and a variable attenuator 15 that attenuates the level of the signal output from the low-pass filter 13.
An amplifier (AMP) 17 for amplifying the output signal of the variable attenuator 15 and sending it as a detection signal from the transmitting antenna 1,
It has. The attenuation value of the variable attenuator 15 is set so that the output level of the detection signal transmitted from the transmitting antenna 1 falls within a predetermined specified value.

On the other hand, the receiving device 7 includes a CPU, a ROM, and an R.
Microcomputer equipped with AM, etc. (hereinafter simply referred to as CP
21), a reception signal from the reception antenna 5, and a bandpass filter (BPF) 23 that attenuates frequency components other than the reception band (f1 to f2) and a reception signal from the bandpass filter 23. Amplifying amplifier (A
MP) 25, a variable attenuator 27 that attenuates the amplified received signal level according to a control voltage from the outside, and C
According to the frequency data (digital data) output from the PU 21, a predetermined frequency range (in this embodiment, 18.08 to which is higher than the frequency of the detection signal by 10.7 MHz).
A direct digital synthesizer (hereinafter simply referred to as DDS) 29 as an oscillator that outputs a sine wave signal of 19.77 MHz), an amplifier (AMP) 31 that amplifies the output signal from the DDS 29, and an output signal of the amplifier 31. To input the required frequency component (18.08 to 19.7).
Band pass filter (BP) that passes only 7MHz
F) 33, the output signal from the band pass filter 33 and the received signal from the variable attenuator 27 are mixed, and the received signal is in the 10 MHz band (intermediate frequency fi = 10.
Mixer 35 for converting into a signal of 7 MHz) and mixer 35
The IF band pass filter (IF-B which attenuates frequency components other than the intermediate frequency fi by inputting the received signal from
PF) 37, an IF amplifier (IF-AMP) 39 that amplifies the output signal from the IF band pass filter 37, a detector 41 that detects the amplified received signal, and a detection voltage output from the detector 41. High-pass filter (HPF) 43 and low-pass filter (LP) that shape the signal waveform
F) 45 and the waveform-shaped detected voltage signal output from the low-pass filter 45 are converted into digital signals to generate CP.
A / D converter 47 for outputting to U21, and IF amplifier 39
From the diode 49 for detecting the 10.7 MHz reception signal output from the detector 41 to the detector 41, and the control voltage is output to the variable attenuator 27 so that the detection voltage from the diode 49 is always the predetermined reference voltage V. An automatic gain control circuit 51 for keeping the level of a received signal input to the detector 41 constant,
It is detected whether or not the detection voltage from the diode 49 is below a predetermined value, and when the voltage is below a predetermined value, the CPU 2
A comparator 53 that outputs a low-level signal ST to 1 and a lamp 55 and a buzzer 57 as notification means for notifying the occurrence of shoplifting are provided.

The control loop including the variable attenuator 27, the diode 49, and the automatic gain control circuit 51 controls the overall level of the received signal input from the IF amplifier 39 to the detector 41 by the detector 41. This is for stabilizing the level at which detection is possible, and is set so as not to follow a steep level change (for example, a change of 1 kHz or more) of the received signal.

In the shoplifting prevention device of this embodiment having such a configuration, the CPU 9 of the transmitting device 3 executes a sweeping process (FIG. 3) described later, so that the transmitting antenna 1
To f1 = 7.38 MHz to f2 = 9.07 MHz, the detection signal is swept and transmitted. Then, C of the receiving device 7
The PU 21 detects the signal level of the reception signal from the reception antenna 5 by executing the article detection process (FIG. 4) described later, and detects the presence or absence of shoplifting action based on the signal level.

Therefore, first, the sweep process as the frequency control means executed by the CPU 9 of the transmitter 3 will be described with reference to FIG. It should be noted that this sweeping process is always repeated when the transmitter 3 is powered on. As shown in FIG. 3, when the execution of the sweep process is started, first, in step (hereinafter referred to as S) 110, wait for 0.1 ms, and then in S120, the frequency data to be output to the DDS 11 is initialized. Then, f1 which is the minimum value of the sweep range
Frequency data representing (= 7.38MHz) is 1.5ms
Output during. Then, 7.38 MH from DDS11
A sine wave signal of z is output for 1.5 ms, and this sine wave signal is transmitted as a detection signal from the transmission antenna 1 via the low pass filter 13, the variable attenuator 15 and the amplifier 17. In this embodiment, the DDS 11, the low pass filter 13, the variable attenuator 15 and the amplifier 17 correspond to the transmitting means.

When 1.5 ms has elapsed, the subsequent S
At 130, the next frequency data is set and output to the DDS 11. In this embodiment, the frequency of the detection signal is f1 =
From 7.38MHz to f2 = 9.07MHz, 1.6
The frequency is increased in 80 steps over a period of ms, and the next frequency data output in S130 is the frequency Δf (Δf = ( f2-f1) /79=21.392kH
z) is data representing the frequency added.

Next, in S140, the time Δt (Δt = 1.6 m) per step for changing the frequency of the detection signal.
s / 79 = 20.253 μs) is passed, and when the time Δt is passed, the frequency data currently output to the DDS 11 is f2 (= 9.07 MHz) which is the maximum value of the sweep range in S150. ) Is reached. If it is determined in S150 that the frequency data has not reached the value indicating f2, the process returns to S130 and the frequency data is updated to the DDS 11 (S13).
0) and waiting for the time Δt per step (S140) are repeated.

On the other hand, if it is determined in S150 that the frequency data currently being output has reached the value representing f2, S
The process proceeds to 160, the output of the frequency data is stopped, and then the process returns to S110. Then, DDS11 is S1
The output of the sine wave signal is stopped only for the time (0.1 ms) to wait at 10, so that the detection signal is output for 0.1 time.
It is stopped for ms. Then, when 0.1 ms has elapsed, the processing from S120 to S160 is executed again, and after the frequency of the detection signal is held at f1 for 1.5 ms, Δt (= 20.253 μs) elapses. Every △
It is increased by f (= 21.392 kHz) and is again increased to f2.

That is, as a result of the execution of this sweeping process, the detection signal, as shown in FIG. 7A, has a transmission stop period of 0.1 ms (S110, S160) and a 1.5 ms output at 7.38 MHz. A constant frequency period (S120) and a 1.6 ms sweep period (S130 to S) in which the frequency is increased in 80 steps from 7.38 MHz to 9.07 MHz.
150), and a total of 3.2 ms is set as one cycle (hereinafter, referred to as a sweep cycle) and transmitted from the transmitting antenna 1. That is, in the sweep process, the frequency of the detection signal is
1.6m after maintaining at 7.38MHz for 1.5ms
Every time the time is increased (swept) from 7.38 MHz to 9.07 MHz in 80 steps over a period of s, the transmission of the detection signal is stopped for 0.1 ms.

Next, the article detecting process as the article detecting means executed by the CPU 21 of the receiving device 7 will be described with reference to FIG. It should be noted that this article detection process is also repeatedly executed whenever the receiving device 7 is powered on. FIG.
As shown in, when the execution of the article detection process is started, first, in S210, the inside of the CPU 21 is initialized, and
To DDS 29, the maximum value of the frequency change range is 19.7.
Frequency data representing 7 MHz (= f2 + fi) is output. Then, in the subsequent S220, the frequency of the reception signal from the reception antenna 5 is converted into the intermediate frequency fi by changing the transmission frequency of the DDS 29 in synchronization with the sweep cycle of the detection signal on the transmission device 3 side. A data acquisition process for detecting the signal level after frequency conversion is executed.

This data fetching process is executed as shown in FIG. That is, when this data acquisition process is started,
First, in S410, the signal ST from the comparator 53 is High.
It is determined whether or not the level has changed to the Low level, in other words, whether or not there is a falling change in the signal ST.

Here, the signal S output from the comparator 53
T will be described. First, in the reception device 7, the sine wave signal having a frequency higher than the detection signal by fi (= 10.7 MHz) is output from the DDS 29, and the sine wave signal and the reception signal from the reception antenna 5 (variable attenuator 27) are detected. Are mixed by the mixer 35, the frequency of the received signal is converted into the intermediate frequency fi, and the received signal after the frequency conversion is converted into fi
A narrow band IF bandpass filter 37 and an IF amplifier 39 that attenuate frequency components other than
And the diode 49. Immediately after the power of the receiving device 7 is turned on, by the process of S210,
The DDS 29 outputs a constant sine wave signal of 19.77 MHz (= f2 + fi). Therefore, after the power to the receiving device 7 is turned on, the IF amplifier 39 outputs a signal of a predetermined level only when the frequency of the detection signal transmitted from the transmitting antenna 1 becomes f2 (= 9.07 MHz).
By extension, the detection voltage from the diode 49 becomes a predetermined value or more, and the signal ST from the comparator 53 becomes High level. Then, after that, when the transmission of the detection signal is stopped as described above, the detection voltage of the diode 49 becomes equal to or lower than a predetermined value (approximately 0 V), and the signal ST from the comparator 53 becomes Low.
Change to a level.

That is, in this embodiment, after the power supply to the receiving device 7 is turned on, the signal ST from the comparator 53 is output at the timing when the transmission of the detection signal from the transmitting antenna 1 is first stopped.
It is configured so that a falling change occurs at the time. In S410 of the data acquisition process, this timing is detected.

If it is determined in S410 that the signal ST has fallen and changed, the process proceeds to S420 and D
Initially set the frequency data to be output to the DS29 to the minimum value of the frequency change range of 18.08 MHz (= f1 +
The frequency data representing fi) is output, and in the subsequent S430, the time (1.6 m) obtained by adding the transmission stop period (0.1 ms) of the detection signal and the constant frequency period (1.5 ms).
s) only wait.

Then, from the DDS 29, 18.08M
A sine wave signal of Hz is output for 1.6 ms, and this sine wave signal is input to the mixer 35 via the amplifier 31 and the bandpass filter 33. At this time, since the detection signal of 7.38 MHz is transmitted from the transmission antenna 1, in the reception device 7, the reception signal from the reception antenna 5 is frequency converted into a signal of 10.7 MHz by the mixer 35, and After being input to the detector 41 via the IF band pass filter 37 and the IF amplifier 39, the detection voltage from the detector 41 is waveform-shaped by the high pass filter 43 and the low pass filter 45, and then the A / D converter 47 is output. It is input to the CPU 21 via the.

Then, in the subsequent S440, the CPU 21 fetches the digital data (hereinafter referred to as level data) from the A / D converter 47 and stores it in the RAM, and in the subsequent S450, sets the next frequency data. DDS29
Output to. The next frequency data set in S450 is also set to the frequency of the sine wave signal currently output by the DDS 29 by one step in the sweep process, just as in S130 of the sweep process executed on the transmitter 3 side. Frequency per hit Δf (=
(21.392 kHz) is the data representing the frequency.

Then, in the following S460, it is determined whether 80 pieces of level data have been fetched, that is, the processing of S440 is performed by 80.
If it is determined that 80 level data have not been fetched, it is determined in S470 that follows.
After waiting for a time Δt (= 20.253 μs) per step in which the frequency of the detection signal is changed by the sweep process, S
Returning to 440, the processing of S440 to S470 is repeated.
On the other hand, if it is determined in S460 that 80 level data have been captured, the data capturing process ends.

That is, in the data fetching process, the comparator 53
It is detected that the sending of the detection signal is temporarily stopped by detecting the fall of the signal ST from (S).
410), 1.6m from the detection timing as a starting point
During s, the transmission frequency of DDS29 is 18.08MHz
(= F1 + fi) (S420, S430), and thereafter, just like the transmitting device 3, the transmission frequency of the DDS 29 is Δf (= 21.25 μs) every time Δt (= 20.253 μs) elapses. 392 kHz), and finally up to 19.77 MHz (= f2 + fi) in 80 steps (S450 to S470). Therefore, DDS29
Since, always fi (= 10.7MHz) than the detection signal
Only a high frequency sine wave signal will be output,
By extension, the received signal from the receiving antenna 5 is always converted into the signal of the intermediate frequency fi = 10.7 MHz and input to the detector 41.

Furthermore, in the data acquisition process, the DDS 29
Just before increasing the transmission frequency of Δf by Δf,
Signal level of received signal detected in 1 (detection voltage)
Are fetched as level data via the A / D converter 47, and the respective level data are sequentially stored in the RAM (S
440). In this embodiment, S440 corresponds to the level detecting means and the storing means.

Therefore, after the power is turned on, the data acquisition process is 1
When it is executed once, 80 pieces of level data D1, 1, D1, 2, ..., Are stored in the RAM as shown in the uppermost part of FIG.
D1 79 and D1 80 will be stored. Note that FIG.
In (B), D1 · n is the frequency of the detection signal transmitted from the transmitting antenna 1 is “(f1 + (n−1) · Δ”.
f): However, n represents the level data when it is an integer of 1 to 80.

Next, when the CPU 21 completes the execution of the data fetching process, the CPU 21 proceeds to S230 shown in FIG.
It is judged whether the data acquisition process has been executed 16 times,
When it is determined that the process has not been executed twice, the process returns to S220 and the processes of S220 and S230 are repeated.

As described above, S of the data acquisition process
When the processing after 420 is executed, after that, DDS2
7 outputs a sine wave signal having a frequency higher than that of the detection signal by fi, and the IF amplifier 39 outputs a reception signal of a predetermined level that has been frequency-converted to 10.7 MHz, as shown in FIG. Signal S from the comparator 53
T becomes Low level only when the transmission of the detection signal is stopped on the transmitter 3 side. Therefore, when the data acquisition process is performed after the power is turned on to the receiving device 7 for the second time or later, the timing at which it is determined in S410 that the signal ST has fallen and changed, that is, the detection signal. Is resynchronized with the timing at which the transmission of
The substantial process of S470 to S470 is executed.

When it is determined in S230 that the data fetching process has been executed 16 times, the process proceeds to S240. Therefore, when proceeding to S240, a total of 1280 (= 80 × 16) level data are stored in the RAM, as shown in FIG. 7B. In FIG. 7B, Dm · n represents the nth level data captured when the mth (mth sweep) data capture process is executed.

Next, in S240, the counter n is reset to 0, and in the subsequent S250, the counter n is incremented. Then, in S260, as described above, 16
In each data fetching process that has been executed once, a process as an average value calculating unit that calculates the average value Dn of the level data Dm · n (m = 1 to 16) stored in the nth RAM is executed.

Then, in the following S270, it is determined whether or not the value of the counter n has reached 80, that is, whether or not the calculation of the average value has been completed for all the 1st to 80th level data, and the counter is counted. When it is determined that the value of n is not 80, the process returns to S250 and S250 to S270.
Is repeated. Then, in S270, the counter n
When it is determined that the value of 80 has become 80, the process proceeds to S280, and all the average values D1 to D80 calculated in S260 are stored in the RAM.

As a result, as shown in the lowermost part of FIG. 7B, the level data detected at the same timing in each of the 16 data acquisition processes (that is, the detection signal of the same frequency is sent to the RAM). Received level when received) was averaged 8
0 average values D1 to D80 (hereinafter, average data D
(A) is stored. That is, in the present embodiment, for example, pulse noise occurs within the sweep frequency range (f1 to f2) of the detection signal, and as shown in FIG. 8A, in the receiving device 7, from the A / D converter 47 to the CPU 21. Even if the level data input to the RAM has a large level change, the average data DA (D
1 to D80), as shown in FIG. 8B, level data of a stable waveform that is not affected by pulse noise is stored.

Thus, the average data DA is stored in the RAM.
When is stored, whether or not the change pattern of the level data within one sweep cycle matches a preset article detection pattern (hereinafter, referred to as a tag pattern) based on the average data DA in S300. As a result of the determination, the received signal is the tag (resonance circuit M
It is determined whether or not the tag signal generated by a) is included, and if the tag signal is included, the lamp 55 and the buzzer 57 are driven for 1 second, and the product M exists between the transmitting antenna 1 and the receiving antenna 5. That is, in other words, the tag signal determination / alarm process (FIG. 6) described later that notifies that shoplifting has occurred is activated.

Then, the tag signal discrimination / warning process (S
300) is started, the process proceeds to S310, where the RAM
Of the level data stored in, the oldest data for one sweep cycle, that is, the data stored in the first data acquisition process
Eliminates 0 level data D1.1-D1-80, and m
Each level data Dm stored in the data acquisition process for the first time
RA as level data D (m-1) .. 1 to D (m-1) .80 stored from 1 to Dm.80 in the (m-1) th data acquisition process.
The data is stored again in M, and in the subsequent S320, the data fetching process shown in FIG. 5 is executed just as in the case of S220.
In addition, in the data acquisition process executed in S320, RA
The 80 level data stored in M are stored in the RAM as the latest level data D16-1 to D16.80.

When the execution of the data acquisition process is completed in S320, the process returns to S240 again, and S240
~ The process of S320 is repeated, and thereafter,
Every time 80 level data for one sweep cycle is acquired,
The average data DA is calculated using the level data for a total of 16 sweep cycles consisting of the level data for the current time and the level data for the immediately preceding 15 sweep cycles, and the presence or absence of the product M is calculated using the average data DA. Sequentially determine (whether shoplifting has occurred).

Next, the tag signal discrimination / warning process activated in S300 will be described with reference to FIG. It should be noted that this process is performed as an interrupt process for the series of article detection processes, which is the main routine, after the start-up, while the article detection process is stopped (for example, during the 1.6 ms waiting time in the data acquisition process executed in S320). ), Which corresponds to the determination means of the present invention.

As shown in FIG. 6, when this process is started, first, at S510, each value D of the average data DA.
1 to D80 are preset upper threshold VH
It is sequentially determined whether or not the value exceeds the upper threshold VH, and the value 1 is applied to the average data Dn that exceeds the upper threshold VH.
Is the average data D below the upper threshold VH.
As shown in the uppermost row of FIG. 9, each value D1 to A1 of the average data DA is set such that the value 0 is set for n.
Upper determination data DH (DH1 to DH80) indicating whether or not D80 exceeds the upper threshold VH is created.

In subsequent S520, it is sequentially determined whether or not each value D1 to D80 of the average data DA is smaller than a preset lower threshold VL, and the average data Dn smaller than the lower threshold VL is determined. Is set to 1 and the value 0 is set to the average data Dn that is equal to or lower than the lower threshold VL. As shown in the bottom of FIG. 9, each value D1 to D80 of the average data DA is set to the lower threshold. Lower determination data DL (DL1 to DL8) indicating whether or not it is smaller than VL
0) is created. The processes of S510 and S520 correspond to the upper / lower point detecting means of the present invention.

Then, in the subsequent S530, the counters n, i and the flag F used in the subsequent processing are initialized (reset), and one sweep obtained from the average data DA is carried out based on the respective judgment data DH, DL. A tag signal determination operation for determining whether or not the variation pattern of the received signal level within the cycle matches the variation pattern (tag pattern) of the tag signal is started. That is, first in S540, it is determined whether or not the value of the counter n is 80, which indicates that the determination operation for all points (n: 1 to 80) of the determination data DH and DH is completed, and the counter n is counted.
If the value of is 80, the process ends. On the other hand, if the value of the counter n is not 80, S55
At 0, the counter n is incremented (+1) and S
Moving to 560, each of the determination data DH and DL created above
Among them, whether or not the determination data DHn and DLn of the point n corresponding to the value of the counter n are both 0, in other words, the average data Dn of the point n is between the upper and lower thresholds VH and VL. Determine whether or not. If the determination data DHn and DLn are both 0, S
In step 570, the counter i is incremented (+
1) Then, in S580, it is determined whether or not the flag F is set (1). If the flag F is in the reset (0) state, the process proceeds to S540 again.

Next, in S560, the judgment data DH
Both n and DLn are not 0, and the determination data DHn and DLn
When it is determined that any one of n is 1, S59
At 0, it is determined whether the value of the counter i is 3 or more. If the value of the counter i is 3 or more, S60
At 0, the value of the counter n is set in the starting point data j1 representing the starting point of the later-described determination block, at S610, the flag F is set (1), and at S620, the counter i is initialized (i = 0. ), The process proceeds to S540 again. On the contrary, if the value of the counter i has not reached 3, the process directly proceeds to S620 and the counter i is initialized (i = 0).
Then, the process proceeds to S540.

Here, the counter i is the judgment data DH.
It is incremented when both n and DLn are 0 (S570), and is initialized when either of the determination data DHn and DLn is 1 (S620). This is the threshold V with the average data Dn above and below.
This is because the number of consecutive points between H and VL is counted, and the frequency region in which the received signal is stable can be known from the value of this counter i.

When either of the judgment data DHn and DLn is 1, it is judged whether the value of the counter i is 3 or more (S590). This is because the average data DA is the upper and lower thresholds VH. , VL to determine whether or not the average data DA is in the stable region between the upper and lower thresholds VH and VL in the frequency region of three points or more in which the frequency is lower than the point deviated from the stable region. Is.

That is, in this embodiment, as shown in FIG.
Average data D in the frequency range of 3 points or more
When A is in the stable region between the upper and lower thresholds VH and VL, the region is set as the 0 region in which the tag signal is not determined, and the average data DA is set to the upper and lower thresholds VH and VL. When it deviates from the stable region between VLs, a region having a high frequency from that point is set as a determination block for determining the tag signal.
The value of the counter n representing that point is set as the starting point data j1 representing the starting point of the determination block (S60
0), the fact that the judgment block has been entered by setting the flag F is stored (S610).

Next, in S580, when it is determined that the flag F is set, the process proceeds to S630, and it is determined whether or not the value of the counter i is 3 or more, as in S590. . Then, if the value of the counter i is 3 or more, in S640, a value (n-3) obtained by subtracting 3 from the current value of the counter n is set as the end point data j2 representing the end point of the determination block, and S650. In each of the judgment data DH and DL, from the judgment data DHj1 and DLj1 of the point n (= j1) corresponding to the start point data j1, to the judgment data DHj2 and DLj2 of the point n (j2) corresponding to the end point data j2. The area up to is set as the judgment block.

That is, after the start point data j1 representing the start point of the judgment block is set in S600, the average data DA is set in the stable area between the upper and lower thresholds VH and VL in the area where the frequency is higher than this starting point. A frequency region (0 region) in which the entered points are continuous for 3 points is searched, and as shown in FIG. 9, the point immediately before entering the 0 region is set as the end point of the determination block to determine the determination block.

The processing of S550 to S650 executed to determine the determination block in this way corresponds to the area determination means of the present invention. Then, when the determination block is set in this way, the process proceeds to S660, and in the determination block, from the number of points where the values of the determination data DH and DL are 1 in this determination block and the array state thereof, The change pattern of the average data DA (in other words, the waveform of the received signal) is recognized (pattern check), and the subsequent S
At 670, a process as a pattern determining means for determining whether the change pattern matches a preset tag pattern is performed.

That is, when the product M exists between the transmitting antenna 1 and the receiving antenna 5 and the resonance circuit Ma of the tag attached to the product M resonates with the detection signal, the reception signal level is shown in FIG. As described above, since it fluctuates up and down largely in the resonance frequency region, it is judged whether or not the average data DA fluctuates along this fluctuation pattern in the frequency region set as the judgment block.

In the present embodiment, (1) there are 2 points at which 1 is in the upper determination data DH in the above determination block.
Up to 4 consecutive points, and all the other points are 0 in both the upper determination data DH and the lower determination data DL. In other words, the average data DA is shown in FIG.
When fluctuating as shown in.

(2) In the upper judgment data DH, 2 to 4 points which become 1 are continuous, and the lower judgment data is placed in either the region where the frequency is lower than this point or the region where the frequency is higher, or both. When 1 to 5 points that become 1 in DL are consecutive. In other words, when the average data DA fluctuates as shown in FIGS. 10 (b) to 10 (d).

Average data DA in the decision block
It is determined that the change pattern of No. 1 matches the tag pattern, and otherwise, it is determined that all the change patterns do not match the tag pattern. If it is determined in S670 that the change pattern of the average data DA in the determination block does not match the tag pattern, in S680,
In order to set the next determination block, the flag F is reset, the process proceeds to S540 again, and it is determined in S670 that the change pattern of the average data DA in the determination block matches the tag pattern. , S690, the lamp 55 and the buzzer 57 are driven for 1 second to notify (alarm) that the product M is present between the transmitting antenna 1 and the receiving antenna 5, and the process is once ended.

As described above, in the shoplifting prevention device of this embodiment, the sweeping period is the same as the sweep period of the detection signal transmitted from the transmitting antenna 1, and the sweep period within each transmission period is a predetermined time. For each Δt, the signal level of the received signal from the receiving antenna is sequentially fetched as level data, stored in the RAM, and the stored level data for a plurality of sweep cycles (specifically, for 16 cycles) is stored for each frequency. Averaged data DA (D
1 to D80) and using this average data DA to determine whether or not the change pattern of this average data DA matches the tag pattern when the product M is placed between the antennas. Existence of product M,
In other words, a shoplifting act is determined.

Therefore, according to the shoplifting prevention device of the present embodiment, signals within the frequency range (f1 to f2) of the detection signal such as pulse noise and transmission signals from other communication devices enter from the outside. However, the occurrence of shoplifting can be detected extremely accurately without being affected by such signals.

In this embodiment, the average data D
In determining whether or not the change pattern of A matches the tag pattern, first, the average data DA
Upper judgment data DH representing points at which the respective values D1 to D80 of the upper threshold VH are exceeded, and lower judgment data DL representing points at which the respective values D1 to D80 of the average data DA are smaller than the lower threshold VL.
, And the average data DA is in a stable region between the upper determination data DH and the lower determination data DL from the entire frequency range (f1 to f2) of the generated determination data DH and DL. A frequency region sandwiched by three or more consecutive 0 regions is extracted as a determination block, and it is determined for each determination block whether or not the change pattern matches the tag pattern.

Therefore, according to the present embodiment, in determining whether or not the change pattern of the average data DA matches the tag pattern, the change pattern of the average data DA is spread over the entire frequency range within one sweep period. Therefore, it is not necessary to analyze and the pattern determination can be performed only by counting the number of points that become 1 in each determination data DH and DL, so that the shoplifting action can be determined at high speed and with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a block diagram showing a configuration of a shoplifting prevention device according to an embodiment.

FIG. 3 is a flowchart showing a sweep process executed on the transmitter side.

FIG. 4 is a flowchart showing an article detection process executed on the receiving device side.

FIG. 5 is a flowchart showing a data acquisition process executed in the article detection process.

FIG. 6 is a flowchart showing a tag signal determination / warning process activated along with the execution of the article detection process.

FIG. 7 is an explanatory diagram showing a detection signal transmission procedure and an average data generation procedure corresponding thereto.

FIG. 8 is an explanatory diagram showing a detection signal waveform and a change characteristic of average data generated by receiving the detection signal.

FIG. 9 is an explanatory diagram illustrating a generation procedure and a determination block of upper determination data and lower determination data.

FIG. 10 is an explanatory diagram showing an example of a change pattern of average data recognized as a tag pattern.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transmitting antenna 3 ... Transmitting device 5 ... Receiving antenna 7 ... Receiving device 9,21 ... Microcomputer (CPU) 11, 29 ... Direct digital synthesizer (D)
DS) 13,45 ... Low-pass filter 15, 27 ... Variable attenuator 17, 25, 31 ... Amplifier 23, 33 ... Band-pass filter 35 ... Mixer 37 ... IF band-pass filter 3
9 ... IF amplifier 41 ... Detector 43 ... High-pass filter 47 ... A
/ D converter 49 ... Diode 51 ... Automatic gain control circuit 53
... Comparator 55 ... Lamp 57 ... Buzzer M ... Product Ma ...
LC resonance circuit

Claims (4)

[Claims] 1. A transmitting antenna and a receiving antenna, which are installed at a predetermined interval, transmitting means for transmitting a detection signal of a predetermined frequency from the transmitting antenna, and a frequency of the detection signal to the transmitting means in a predetermined frequency range. A frequency control means for periodically changing the resonance frequency, and a resonance circuit in which a resonance frequency is set within the frequency range between the transmission antenna and the reception antenna based on a signal level of a reception signal from the reception antenna. In a shoplifting prevention device comprising: an article detecting unit that detects the presence of an article having the item; and an informing unit that notifies that the item detecting unit detects the presence of the item, The same detection cycle as the cycle in which the frequency of the detection signal is changed by the frequency control means, and a predetermined time interval within each detection cycle. And a level detection means for detecting the signal level of the received signal, and whether or not the change pattern of the signal level within the detection period detected by the level detection means matches a preset article detection pattern. And when the change pattern of the signal level matches the article detection pattern, it is determined that the article is present between the transmitting antenna and the receiving antenna, and the notifying means is activated. A shoplifting prevention device comprising: a judging means. 2. The article detecting means further includes a storage means for sequentially storing the signal levels detected by the level detecting means, and a signal level for a predetermined detection cycle stored in the storage means, and each detecting means. An average value calculating means for calculating an average value of signal levels detected at the same point in the cycle, and the determining means for each point in the detection cycle calculated by the average value calculating means. 2. The shoplifting prevention device according to claim 1, wherein the shoplifting prevention device according to claim 1, wherein the average value of the items is sequentially taken in as a signal level of the received signal to determine the presence of the article. 3. The determination means compares the signal level of each point in the detection cycle with two preset upper and lower determination levels of the magnitude and the lower determination level to determine whether the signal level is within the detection cycle. At upper and lower point detecting means for respectively detecting an upper point where the received signal exceeds the upper determination level and a lower point where the received signal becomes smaller than the lower determination level, and detected by the upper and lower point detecting means. Based on the number of the upper points and the lower points in the detection cycle and the arrangement state thereof, it is determined whether or not the change pattern of the signal level in the detection cycle matches the preset article detection pattern. The shoplifting prevention device according to claim 1 or 2, further comprising: pattern determining means. 4. The determination means further comprises determination area setting means for setting, as an area for pattern determination, an area in which the upper point and the lower point are consecutive at a predetermined frequency in the detection cycle. The means determines the article detection pattern in which the change pattern of the signal level in the detection cycle is preset from the number of upper points and lower points in the area set by the determination area setting means and the arrangement state thereof. The shoplifting prevention device according to claim 3, wherein it is determined whether or not they match.