JPH04229394A - Method for deenergizing resonance label and circuit constitution for performing this method - Google Patents

Abstract

PURPOSE: To facilitate the detection of a label which is not attenuated yet by transmitting maximum energy to a resonance label in short discharge time and by a low peak value as much as possible when a pulse group is discharged to attenuate the resonance label. CONSTITUTION: In the circuitry having transmission antennas to which the pulse of a pulse generation circuit is possible to be supplied, pulse generation circuits 1 to 4 are formed so as to discharge at least one pulse group (burst). An attenuation element R1 which is capable of switching from an attenuation state to an attenuation lost state via a switch device S1 is connected with transmission antenna C and L1.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION The present invention relates to a method according to the preamble of claim 1 and to an apparatus for carrying out this method.

BACKGROUND OF THE INVENTION A method of this kind has already been proposed in EP-A28
7 905, and has actually gained a good reputation. However, it must be taken into account that contradictory demands are placed on the energy emitted by the attenuator. This means that as high an energy as possible is transferred to the label, so that the label can be deenergized over as large a distance as possible and, for economic reasons, the manufacturing tolerances do not have to be too small. On the other hand,
There are legal limits in each state that limit the amount of energy that can be released. These upper limits are also necessary for the necessary compatibility with the components of the radio frequency protection device. Particularly problematic in this case are the peak value of the energy released and the input time.

OBJECTS OF THE INVENTION The object of the invention is to transfer maximum energy to the resonant label with as short an emission opening and as low a peak value as possible.

SUMMARY OF THE INVENTION In the present invention, the above-mentioned problems are solved by the energy reduction method as set forth in claim 1.

Operation The invention is based on measurement and realization. According to it, in a constant alternating magnetic field with a deenergizing frequency corresponding to the label, even after a relatively small oscillation train, there is an equilibrium between the incident energy and the energy dissipated by heat loss and release at the label. is achieved. Subsequent vibration trains emitted from the deenergizing antenna no longer increase the probability of deenergizing the resonant label much. As proposed in EP-A above, we do not process by one individual pulse, but by successive pulses in a group of pulses, so that each pulse carries out the excitation of the oscillatory circuit given by the label. means. The energy gradually released from the label is then accumulated and amplified, as it were, in this oscillating circuit. Therefore, for equal range, the individual pulses can be significantly weaker than before. Therefore, the possibility of interfering with other components is also greatly reduced. Because the individual pulses are weaker,
Using pulse groups of several pulses each does not significantly increase the total energy radiated. In one advantageous embodiment, feature a) of claim 2 is followed. In that case, a certain amount of energy based on the previously emitted pulse group remains in the label that has not yet been deenergized, and may contribute to vibration amplification as the case may be.
Burst pause time, i.e. two individual pulses each (
It would be possible to choose the time between bursts). It is also advantageous to provide features b) and/or c) of claim 2. A further advantageous specification based on the above findings is set out in feature e) of claim 2. Since several pulses are emitted within one pulse group, it is possible to take measures according to feature d) of claim 2. This allows possible manufacturing tolerances to be taken into account. The inventive circuit arrangement for implementing the inventive method is characterized by the features of claim 3. Claim 3 indicates two features as alternatives, but both features act to solve the same problem. This is because it must be remembered that the pulses emitted according to the invention should have a testable deenergizing effect. The damping circuit provided according to the second feature of claim 3 makes it easy to check whether deenergization has taken place. On the other hand, this circuit allows the range of the transmitter to be relatively large. It is thus possible, with reasonable cost and high efficiency, to supply the transmitting antenna with a relatively high instantaneous power at a low average power. By blocking or bridging this resistance during transmission, it is ensured that the transmission power is not absorbed in vain.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings. For example, pulse repetition frequency 20-3
A central timing pulse generator 1 of 0 Hz, for example 25 Hz, is powered by a power supply unit 15 . Power supply unit 15 may include one or more batteries, as implied by the symbol. The power supply unit 15 is also provided with a power supply connection terminal 16 and can switch between two power supplies. The timing pulse generator 1 may be provided with a synchronization coupling 17 so that it can be synchronized with other devices. The frequency of the timing pulse generator determines the number of transmissions (number of emitted pulses or bursts per unit time) of the attenuation circuit. To this end, from the slope of the rectangular transmission voltage of the timing pulse generator 1, short continuous gate pulses are produced via stage 2. Here, it would also naturally be possible to use a timing pulse generator 1 with a signal shape other than a rectangular pulse. However, it is advantageous to provide a subsequent pulse shaping step. This is because, in order to produce the gate pulse in stage 2, a slope as clear as possible is advantageous. This stage 2 is a kind of time element. This time element determines the burst time through the time of the square signal it produces. The time element can be formed, for example, as a monoflop that reacts to the rising slope of the square signal produced by the timing pulse generator 1. As mentioned in the introduction, since the energy delivered to the label is only really effective for a limited time, the time of the gate pulse must be correspondingly limited. The optimal number of pulses per pulse group is generally determined by the Q of the type of resonance label used in each case.
It depends on the coefficient. Labels with a high Q-factor often require more pulses than labels with a lower Q-factor before equilibrium is achieved between received and emitted energy. Here, already EP-A285
559, the Q-factor depends on the quality of the dielectric of the label on the one hand and on the size of the free-space conductive covering in the inductor winding on the other hand. The number of pulses per pulse group is Q/2, or half Q
It is convenient to calculate from the coefficients. For example, coefficient Q=
100 labels require approximately 50 pulses. this is,
For example, a pulse repetition frequency of 8 MHz corresponds to a gate pulse time of approximately 6 microseconds. Therefore, the duration of the gate pulse is up to 100 microseconds, but in most applications it can be much smaller, for example about 50 microseconds. In practice, it has been found that even 10 microseconds can be sufficient. Although these conditions may vary depending on the structure of the label and spatial conditions, useful results were obtained even in about 5 microseconds (±1 microsecond). In fact, it was achieved in just 1 microsecond. The gate pulse emitted by the time element 2 reaches the input of a gate circuit (AND gate) 3, the other input of which is coupled to a pulse train generator 4 which also produces the advantageous continuous square pulse. This gate 3 is opened by the gate pulse of the time element 2 and transmits a group of pulses emitted from the pulse train generator 4 at the corresponding time (burst time). The gate time is selected as described above to transmit the desired number of pulses. It is thus clear that stages 1-4 together constitute a proper pulse generating circuit emitting groups or bursts of pulses. These stages may include other circuits,
For example, it can be replaced by a high-frequency asynchronous pulse generator which is always excited by a time element. The high frequency step-start pulse generator automatically stops again after each start and emission of a predetermined number of pulses. However, such pulse generators generally require a certain amount of oscillation time, so the first described solution is preferred. As is known, resonant labels are subject to certain manufacturing tolerances. This should not be made too small for manufacturing reasons. Therefore, there is some deviation in the natural or resonant frequency of such labels. It is therefore advantageous if the pulse train generator 4 itself has a pulse repetition frequency modulator or, as mentioned above, is coupled to an external modulator 14. On the one hand, if only because it is advantageous to adapt it to the respective label used;
It is desirable to calibrate the frequency spectrum. In this case, stage 14 can be provided with an adjustment knob 18 that allows stepless calibration or switching. On the other hand, two methods are possible for modulating the pulse frequency. That is, modulation can occur within a single pulse group or between bursts. Since the burst time is relatively short, the first method has poor performance, at least unless combined with the second method. In the simplest manufacturing solution, the modulator is designed as a ramp generator. The ramp generator provides the pulse generator 4 with a continuous shift in pulse train frequency. This shift takes place within each pulse group itself, but also between pulse groups. However, as already mentioned, if the modulator 14 is controlled indirectly by the output of the amplifier 5 and thus via the gate pulse of the time element 2, then the frequency will change during the burst pauses between the individual pulse groups. No adjustments will be made. In this case, the length of the ramp reasonably corresponds to several times the time of the gate pulse and therefore elapses after several burst pulses. Amplifier 5 serves as a drive circuit for the final stage (output stage) 6. This final step obtains the operating voltage via the voltage converter 7. Like the high frequency oscillator 4, this is described as being connected to the power supply section. However, the voltage converter 7 can also have its own power supply in the case of battery power supply. The signal emerging from the final stage 6 is then fed to the transmitting antenna C, L1. Because the total energy demand is relatively low, it is easily possible to form the deenergization circuit as a battery power supply. In either case, the circuit can be combined with a conventional barcode scanner 19 or at least one of the two antennas CC, L1 and/or L2 mentioned above can be coupled to this scanner 19.
It is advantageous to attach it to the casing. The scanner 19 can be configured in various ways, but a planar scanner or a vertical scanner integrated into the cashier system is advantageous. The advantages of such an approach are obvious. Usually when reading a bar code attached to a resonant label, the scanner 19 simultaneously and automatically de-energizes the label. The de-energizing circuit is easy to form due to its small size (low de-energizing energy). For example, in the case of a flat scanner, the antenna can simply be mounted on top of the scanner as an accessory, and in the case of a vertical scanner, it can be placed conveniently in front of the scanner. In some cases, by holding the scanner directly on the label, a particularly high deenergization rate is guaranteed. As a result, the required deenergization energy can be further reduced. The scanner 19 is
The plug jack 20 can be used to connect to an adapter plug 21 having the circuit configuration described above. The scanner 19 then closes the switch 22 if necessary if the power supply is selectively switchable from battery power to network power. This switch also allows switching to battery power if necessary. As shown in FIG. 1, a further time element 9, which is designed, for example, as a monoflop, is connected to the output of the time element 2. Time element 9 produces a test pulse that is much longer than the pulse time of the gate pulse ejected by time element 2. This time element 9 is
For this purpose, it is triggered by the falling slope of the gate pulse coming out of stage 2. The receiver circuit identifies the label which continues to vibrate (and thus is clearly not yet de-energized). Such a signal arrives via the above-mentioned receiving antenna L2. In order to prevent overcontrol and destruction of the receiving part, a limiting stage 10 is connected downstream of the receiving antenna. When the high frequency amplifier 11 is released by the time element 9, the incoming signal is suitably amplified by this amplifier and sent to the analysis stage 12. The analysis step 12 activates optical and/or acoustic signal devices 23, 24 as shown schematically. It may be desirable to activate the signaling devices 23, 24 on different occasions. In most cases, it is preferred that the respective signaling device 23 or 24 issue a warning only if deenergization has not taken place. This is also a standard example. However, sometimes it is clear that deenergization has taken place at the signal device 23.
and/or confirmed by the operation of 24. In this case, selector switch 2 is added to the circuit described above.
Just connect 5. Through various logical combinations,
Optionally, other modes of the signaling devices 23, 24 are also possible. For example, the following information can be combined: "label identification", "label produces attenuated echo" (not attenuated), and "label echo suddenly disappears" (attenuated). Instead of being a simple switch as shown, the selector switch 25 can also be designed as a switch that can be adjusted to several positions. Finally, as is clear from FIG.
During the operation of 25, not only does the time element 9 open and close only one time window, but this time window signal reaches the switch stage S1 via the amplifier 8 (to match the impedance). By means of this switch stage S1, which is preferably formed by an electronic switch, the damping resistor circuit R1 is switched into the antenna circuit C, L1. The damping resistor circuit R1 can be formed from a single damping resistor or several elements in the manner described above. The attenuation resistor circuit R1 significantly reduces interference factors for the receiving circuit of the resonant antenna circuit R1. This makes it easy to re-detect any label echoes that may exist via the receiving antenna L2. Therefore, during the gate pulse when a burst is radiated and high energy is supplied to the antenna C, L1, the switch S1 is closed and the damping resistor circuit R1 is bridged. In order to prevent label deenergization from influencing the label deenergization system operating in the vicinity, the timing pulse generator 1 can be synchronized with the deenergization system. On the one hand, this can be done simply via the terminal 17 using a cable. On the other hand, the necessary synchronization signals can also be obtained wirelessly via existing receiving circuits. This receiver circuit includes means 26 (FIG. 1) for identifying the signal received by the label echo detection system and producing therefrom a synchronization signal suitable for synchronizing the pulse train delivery.
has been established. Additionally, it is desirable not only to synchronize the timing pulse generator 1 with other components via the terminal 17, but also to derive a synchronization signal from the circuit in order to know when a burst pause occurs. This can be done by means of the synchronization output 17'. In the embodiment according to FIG. 2, identical functional parts are provided with the same reference numerals as in FIG. In this case, some parts shown in FIG. 1 are omitted. These are parts that may actually be absent, or are actually present but not shown. In any case, individual features of the various embodiments can be exchanged or combined with one another. In this case as well, battery power supplies are primarily of interest, but circuit power supplies are likewise possible. Therefore, the connection with the barcode scanner 19 can also be seen. In order to simplify the circuit structure and to make it easier to accommodate the antennas C, L in the casing of the scanner 19, only one antenna C, L is provided here. This antenna operates as either a transmit antenna or a receive antenna. For this purpose, the output of the final stage 6 and the input of the limiting stage 10 are coupled to a controlled switch stage S1'. This switch stage couples the antennas C, L to either the output of the final stage 6 or the input of the limiting stage 10. The control of this switch stage S1' takes place via the time window signal of the time element 9 and the amplifier 8, analogous to the switch stage S1 in FIG. This circuit arrangement therefore requires less space and is very advantageous compared to known circuits, in which it is rather undesirable to provide such a switching possibility. The damping resistor R1 is connected as a resistor of the limiting stage 10 and can be bridged by the switching stage S1. However, the blocking may also be possible by methods other than bridging. If the label occupies an unfavorable position on the product relative to the transmitting antenna, for example at exactly right angles to the antenna, the label will receive little energy from the antenna. To rectify this, it is advantageous to provide a large number of transmit antennas, at least two. Two transmitting antennas C′ shown in FIG.
In the case of L1' and C''L1'', it is preferable (due to the phenomenon mentioned at the beginning of this paragraph) that these antennas stand at right angles to each other. Although generally not necessary, if two or more antennas are provided, they can be distributed at appropriate angles. In this case, it is important to distribute the output signal of the final stage 6 to the transmitting antennas C', L1' and C'', L1''. This can also be done by means of a switch step S1 associated with the antenna. This switch stage has the function of a multiplexer stage when there are several antennas. However, this multiplexer stage S
1'' is not controlled by the time element 9 like the other switch stages S1' and S1 associated with the antenna, but by a frequency divider 13. The gate pulse is split again, and in one half of the pulse time the pulses of one group of pulses are applied to the antennas C', L1' and in the other half of the pulse time to the antennas C'', L1''. Therefore, the gate pulse of stage 2 is longer than in Figures 1 and 2. Since an independent receiving antenna is used here, the antenna circuits C', L1'' and C', L1'' are provided with a damping element R1'.
and R1'' are recommended. These antenna circuits can be bridged for transmitting operation via switch stages S1a, S1b. Since the transmitting antennas operate sequentially, they only need to be excited by the time element 9. It would also be possible to synchronize using a frequency divider 13 instead of using a frequency divider 13. However, such a measure is not necessary in most cases.
'' by the output of the final stage could be excited in parallel rather than sequentially. However, this would mean splitting the energy, which could cause problems. Therefore, the multiplexer stage Preference is given to the configuration described above with S1''. Whether such a configuration with several transmitting antennas not found in the prior art processes with the above-mentioned burst signals and whether the above-mentioned cut-off attenuation configuration R1, R1' or R1'' exists. On the other hand, such a multiple antenna arrangement can also be advantageously provided in the arrangement according to FIG. 1 or 2. If there are several antennas, the entire arrangement can be It would be particularly advantageous to accommodate them in one casing 26, in which only the signal devices 24 and 23 are exposed.Such a casing 26 is densely designed for high frequencies and has at least one It has two inlet openings (and possibly also one exit opening, as in baggage X-ray screening machines at airports), which can optionally be closed with a lid, in which case the product de-energizes the label. In this case, the energization switch can be configured to close when the casing lid is closed.The energization switch generates a energization pulse or, as in the present invention, a group of pulses (burst). ) occurs. Many variations are possible within the framework of the invention. It is clear, for example, that stage 13 of FIG. It would also be possible to provide an additional time element controlled by and synchronized with stage 2 in order to control the switching device S1' of 2.However, it would be possible to provide an additional time element controlled by and synchronized with stage 2 to control the switching device S1' of 2. It is simple to use the simple element 9 when the casing 26 and the lid actuate the de-energizing trigger switch. De-energizing does not necessarily have to be done with such a switch. It is also possible to have a deenergizing signal constantly flowing through the housing 26, especially if the housing is designed as a pass-through housing.On the other hand, it is often possible to provide a small housing 26. Such a trigger switch is preferred even in cases where the trigger switch can be mounted in various locations (not shown).
By attaching it to itself, it can be centrally turned on or off, or all switch parts can be turned off. Also, at least a part of the circuit is operated in standby operation to some extent (for example, the timing pulse generator 1 or the pulse train generator 4), and other parts are cut off,
Or it is also possible to insert a trigger switch just between the power supply unit and the timing pulse generator 1. In this case, the gate switch 3 cannot be opened at all. Another possibility is to insert a trigger switch between the oscillator 4 and the AND gate 3. The oscillator 4 is then free to operate and is stopped only if desired. Finally, it is also possible to install a trigger switch between the voltage converter 7 and the final stage 6. In order to confirm theft, the antenna then provides a weak signal that only excites the resonance of the label if the trigger switch is not activated. However, in this case it is expedient to combine an operating mode switch for the evaluation circuit, which corresponds to switch 25 and has several switch positions. Thereby, a "theft identification signal" can be emitted if the transmitting antenna emits a weak label identification signal. On the other hand, only "label deenergized" or "label not deenergized" can be distinguished. As for the time element 2, this can be designed as a multivibrator, in particular an unstable multivibrator. However, the time element 2 can have a counter that counts the incoming pulses and forms the gate pulses based thereon.

[Brief explanation of the drawing]

1 represents a first embodiment of a circuit arrangement according to the invention, in particular for battery operation; FIG.

FIG. 2 is a diagram of an alternative configuration that simplifies the circuit.

FIG. 3: Modified embodiment with at least two antennas.

[Explanation of symbols]

1 Timing pulse generator 2 Time element 3 Gate circuit 4 Pulse train generator 5 Amplifier 9 Time element 12 Evaluation circuit 13 Synchronization circuit 14 Frequency modulation circuit 17 Synchronization terminal 18 Adjustment knob 19 Barcode scanner 25 Operation mode changeover switch 26
Casing C Antenna L Antenna R Attenuation element S Switch s Multiplexer

Claims (11)

[Claims] 1. A method for deenergizing a resonant label, comprising an oscillating circuit exciting a transmitter that emits energy in the form of pulses, the energy comprising at least a group of pulses (
A method characterized by the release in the form of a burst. 2. A method according to claim 1, characterized in that it has at least one of the following characteristics: a) at least two groups of pulses are emitted in succession, the burst times of each each shorter than the burst pause time between. b) The burst time of the pulse group is calculated from the Q-factor and the center frequency of the resonant label to be deenergized and is at most 100 ms, but preferably not more than 50 ms, especially 10 ms.
It does not exceed milliseconds, for example 5 milliseconds. c) the burst pause time is at least 10 times the burst time of each pulse group, preferably at least 1
00 times, especially for example 1000 times. d) In a pulse group with one pulse repetition frequency,
and/or modulated in successive pulse groups, the latter being more advantageous. e) Each pulse group contains at most 100, preferably eg 50 pulses. 3. A circuit arrangement for carrying out the method according to claim 1, comprising a transmitting antenna to which pulses of the pulse generating circuit can be supplied. a damping element (which is configured to emit a burst and/or which can be switched from a damping state to a damping-disappearing state via a switch device (S1; S1a, S1b);
R1; R1', R1'') is the transmitting antenna (C, L1; C
', L1', C'', L''). 4. Circuit arrangement according to claim 3, characterized in that it has one synchronization terminal (17, 17'), for example one synchronization input (17). 5. At least two transmitting antennas (C′, L1, C″, L1″), in particular perpendicular to each other, are arranged at an angle to each other, the pulse generating circuit (1
~4) The pulse group output from
5. The circuit according to claim 3 or 4, characterized in that the multiplexer (s1'') is controllable via a synchronizing circuit (13) connected to the pulse generating circuit (1-4). composition. 6. At least an antenna (C, L) is provided for transmission and reception, and said antenna (C, L) comprises a time element (1 to 4) synchronized with a pulse generating circuit (1 to 4). 9) The circuit arrangement according to any one of claims 3 to 5, characterized in that it is possible to switch from a transmitting operation to a receiving operation using a time element that determines, in particular, an opening during a burst pause. 7. The frequency modulation circuit (14) comprises, for example, a ramp generator, ie a pulse train generator (4) which emits the pulse groups of the pulse generator circuits (1 to 4) in order to change the frequency of the pulse group. Claim characterized in that the frequency modulation circuit (14) is provided with an adjustment knob (18) for adjustment, in particular for switching the frequency spectrum, for example from 8 MHz to 11 MHz. The circuit configuration according to any one of Items 3 to 6. 8. Circuit arrangement according to claim 3, characterized in that it has at least one battery for supplying current. 9. Combined with a barcode scanner (19), in particular a flat scanner or a vertical scanner,
At least one antenna (C, L1, L2;
9. The circuit configuration according to claim 3, wherein the circuits C, L) are housed in a scanner casing. 10. The circuit configuration according to claim 3, having at least one of the following features. a) An analysis circuit (12) equipped with an operation mode changeover switch (25) is provided, and at that time, depending on the selection, the display can be switched to a confirmation display in the case of successful energy reduction, or an alarm display in the case of failure in energy reduction. . b) the circuit arrangement is housed in a radiofrequency-tight casing (26) having at least one opening for holding the product to be tested, said opening being able to be closed with a lid; The deenergization trigger switch can be closed via the lid. 11. The receiving device is provided with means capable of identifying a signal emitted from a label detection device installed in the surroundings, as the case may be, and producing a synchronization signal suitable for synchronizing the pulse train emission based thereon. The circuit configuration according to any one of claims 3 to 10, characterized in that: