CN100524378C - System and method for detecting EAS/RFID tags using step listen - Google Patents

Abstract

A system and method for the real-time concurrent detection of 13.56 MHz RFID and 8.2 MHz EAS identification tags using a single stimulus signal.

Description

Use step listen to detect the system and method for EAS and RFID label

Technical field

The present invention relates generally to identification label, particularly detect the system and method for 8.2MHz eas tag and 13.56MHz ISO15693 RFID label simultaneously.

Background technology

Be used for various readings, tracking and/or detect EAS (eas system) label used and the use of RFID (radio-frequency (RF) identification) label just in Rapid Expansion.Level and smooth connection between existing EAS and RFID functional is to the determined consistent theme of RFID users interest; so that they make a profit, and keep they effectively protect low-cost subject of a sale's practicality to the EAS technology and the high executory cost that can not prove RFID investment from RFID.Yet, when identification label have the ability to receive the frequency of EAS and RFID, handle the EAS separately that returns from these labels or the classic method of RFID signal and show certain shortcoming or limitation.For example, the reader of these signals comprises 8.2MHzEAS transceiver and 13.56MHz RFID transceiver in the same encapsulation that drives stand-alone antenna.By the interference between two kinds of technology of traditional analog signal filtering technical finesse.Yet, utilize this kind structure, comprising: element redundancy (that is, and transceiver elements copy, antenna copy, or the like); Because frequency is the required filtering degree big (being estimated as 100dB) near the coherent signal difference of vibration of (less than 1 frequency multiplication) and 2 passbands of permission very; The demand of 2 antennas cause than arbitrary technology of independent configuration wide the structure (approximately twice) of Duoing; And even by these technology, performance is poorer than arbitrary technology of configuration separately.

Though " pulse is listened to " method (for example, launch a succession of different frequency the RF pulse signal so that the pulse of at least one frequency be positioned near the resonance frequency of identification label) relevant with the present invention, for example, the patent No. is 6,249,229 United States Patent (USP) (people such as Eckstein) is incorporated into herein by reference, one of these shortcomings are when using the RFID label, must have from the persistent signal of reader to launch to drive the RFID chip.

Can comprise two kinds of operator schemes with the RFID label communication: " label earlier speech " (TTF) or " reader-talks-first " (RTF).Under the TTF pattern, label is launched its information after receiving reader signal.On the contrary, under the RTF pattern, reader sends response to label firing order (for avoiding conflict) and label to those orders.Therefore, RTF is more complicated in two kinds of patterns, and what the present invention relates to is RTF operation.

Therefore, the system and method that still needs to detect EAS and RFID identification label signal simultaneously and avoid above-mentioned shortcoming.

Summary of the invention

RFID of the present invention " reader-talks-first " (RTF) concept requirement transmits the 13.56MHz carrier amplitude modulation of ordering to being used for to the RFID label.This is modulated at the form that is used for adopting as the carrier wave of ISO15693 or this main RFID technology of EPC (electronic product code) 10% modulation index difference.Modulation index, m is defined as:

$m=\frac{(V_{\max }-V_{\min })}{(V_{\max }+V_{\min })}$

And this modulation index is the tolerance of amplitude drop to the steady-state amplitude of R-T (reader is to label) signal; The timing of these drops is R-T method for communicating.The ISO15693 standard specifies two selections of m, promptly m=10% or m=100% (special, the ISO15693 standard specifies label must be with the reader modulation index operation of 10-30% or 100%).Most of readers and label manufacturer use m=10%.

When carrier wave forcing function amplitude reduces, owing to the excessive stored energy of having dispersed in those labels, so the carrier envelope that forms in this modulation is along the transient response of arbitrary LC resonant circuit in the magnetic field that has caused this system.As an example, detecting this stored energy transient phenomenon (being also referred to as " natural response ") is to be configured in the essence that the RF/EAS in the pulse listening system of assignee (that is Checkpoint Systems company) detects.By using and this related intrinsic physical characteristics of RFID label signalling, may comprise the functional intrinsic naturally aspect of EAS as system.In addition, the present invention allows the public use of most of transceiver components, avoids the cost in circuit and shared antenna structure copy and the poor efficiency in space.

Step listen system and method for the present invention provides in the detection performance of tag throughput, two kinds of technology and the advantage aspect the manufacturing cost.

As going through after a while, this system and method detects EAS and 13.56MHzHF (high frequency) RFID label simultaneously.As an example, the RFID technology of suggestion is obeyed ISO15693, and the use that is exclusively used in the custom code of SLI chip.

At safety door, the RFID command synchronization is correctly validated and is the main performance compression.There are two sync levels that needs are kept: in the RF at safety door place carrier synchronization and the AM between all safety doors (Modulation and Amplitude Modulation) command synchronization.The needs of AM command synchronization have far-reaching performance impact.The RFID label can be handled by the POS (point of sale) that lower power level is operated at the interface, and antenna directivity minimizes coupling and the shielding around the POS antenna, so but their free operant.How no matter safety door see the activity of other safety doors that run through storage.This requires between the safety door reader order modulation synchronously.The truth that the complicated factor of command synchronization responsibility that to be ISO15693 detect conflict and solution place the part reader.This means if wish and solve all RFID label collisions at all safety door places, so all safety doors must be communicated to the central synchronous source with the appearance of conflict, thereby the central synchronous source will order all readers to send newer command to manage conflict then, and no matter conflict whether occur in the quantity of the probability according to the conflict in a certain door, door at safety door place and required solution step quantity and among the fixed uncertainty handling capacity.The label density of supposing given arbitrarily safety door place is being less than 16 far away arbitrarily preset time.

About synchronously, I-code SLI " stock fast " custom code is used for 16 time slot poll RFID labels.Because the consideration of complicacy and handling capacity is not attempted directly managing conflict.Yet, because 16 time slot polling cycles have used 73.2 milliseconds (msec), the mask of four step rule conflict automatically can followingly circulate: no mask (all labels respond), mask=1 (only odd-numbered label response), mask=2 (only to connect the label response of LSB ending) and mask=3 (only the label with 2LSBs=" 11 " ending responds).When the rationally regular circulation time that former anti-collision sequence (scriptedanti-collision sequence) is allowed 292.8 milliseconds, this makes and solves automatically most the conflict.

There are two kinds of methods can set up synchronization links.A kind of is by all safety doors are physically connected together with line.Second kind is to utilize to need synchronous effect.Therefore, wireless synchronization system firing order modulation on the 13.56MHz carrier wave as usual.Every other safety door is sought this order modulation edge and it is set up phase locking in the system, and transmits this signal on their position separately.Similar method for synchronous is used for the 13.56MHz RF carrier wave of each safety door.

As previously mentioned, because two frequencies are mutually near (less than a frequency multiplication), real-time parallel simultaneously detects 13.56MHz RFID and 8.2MHz EAS is a challenge.Band-pass filtering especially is difficult to solve 8.2MHz EAS part, because the inverse relation between time domain and the frequency domain, that is, the filtering on the frequency domain is sharp keen more, and its transient response on time domain is long more.Because it is the time domain process in essence that eas tag detects, so only make two systems together synchronous operation be not a good selection.Two method head it offs are arranged, and wherein this a kind ofly has more technological challenge than another kind.

Description of drawings

To describe the present invention in conjunction with following accompanying drawing, in described accompanying drawing, identical Reference numeral refers to components identical, wherein:

Fig. 1 is a structural drawing of the present invention;

Fig. 2 is that the axle that waits of the exemplary column that uses of the present invention is surveyed a view;

Fig. 3 is a base in one of column, shows the best installation position of electronic component of the present invention;

Fig. 4 has described typical R FID reader RTF pumping signal (for example, 13.56MHz carrier wave);

Fig. 5 has described the RFID label signal (for example, 13.56MHz carrier wave) of response RTF pumping signal;

EAS natural response " ring " signal that Fig. 6 has described response RTF pumping signal (for example, 8.2MHz);

Fig. 7 is the structural drawing that transceiver is listened in common EAS pulse;

Fig. 8 is when Concept Testing, listens to the structural drawing of transmitter section of the modification of transceiver with the common EAS pulse of 13.56MHz operation;

Fig. 9 is the structural drawing of step listen test setting of the present invention;

Figure 10 is the structural drawing that EAS pulse listening system is revised as step listen receiver of the present invention;

Figure 11 describes the oscillograph track of EAS receiver base band when eas tag not occurring;

Figure 12 describes the oscillograph track of EAS receiver base band when eas tag occurring;

Figure 13 describes the antenna waveform of the low Q that shows sharp keen modulation edge;

Figure 14 is the antenna of low Q of RFID reader and the synoptic diagram of impedance matching network;

Figure 15 is that modulation the time realizes the chart of the amplitude of the preferred carrier frequency of sharp keen transition and less preferred carrier frequency to the time;

Figure 16 be the energy of carrier signal when modulation takes place to time diagram, the energy of the sharp keen decline transition of formation more of the present invention reduces with other and uses energy minimizing on the RFID reader of modulation; And

Figure 17 is the optionally antenna circuit of describing the RFID reader, the i.e. synoptic diagram of switch Q antenna circuit.

Embodiment

As shown in Figure 1, the present invention 20 comprises RFID reader 22 and the EAS step listen receiver 24 that is arranged in single shell 26 substantially, and each has separately antenna 28 and antenna 30.During operation, RFID reader 22 emission comprises RFID carrier frequency (for example, pumping signal 32 (Fig. 4) 13.56MHz), and by RTF order modulation.If have RFID label 10 and transferred to the RFID frequency, 10 emissions of RFID label can be by the response signal 34 (Fig. 5) of RFID reader 22 detections so.If (for example, 8.2MHz), eas tag 12 emissions (Fig. 6) can be by natural response " ring " signal 36 (being caused by pumping signal 32) of EAS step listen receiver 24 detections so also to be transferred to the EAS frequency near eas tag 12 also is present in.Should be appreciated that pumping signal 32 and " ring " signal 36 almost take place simultaneously, and RFID response signal 34 takes place after a while.

Fig. 2 has described a pair of exemplary safe column 71A and safe column 71B (for example, the Checkpoint Strata in shop import and export 73 ^TMThe PX column, or the like).As shown in Figure 3, the present invention 20 single shell 26 places among two safe column 71A and the 71B, is arranged in base 75 typically.Internal electric source 77 is RFID reader 22 and EAS step listen receiver 24 and the power supply of other related electronic devices.Should be appreciated that in the most wide in range scope of the present invention, also comprise RFID reader 22 and EAS step listen receiver 24 among each column 71A and the 71B.

Described system of the present invention 20 provides a kind of exemplary operation embodiment of system and method, and this system and method uses the step listen method, detects 13.56MHzRFID and 8.2MHz EAS identification label in real time simultaneously.In this work embodiment, use ISO15693 RFID agreement (will illustrate after a while).Described work embodiment comprises two parts test:

(1) notion part, only use EAS pulse listening system (as shown in Figure 7, also be called EAS transceiver 23, has EAS transmitter 23A, antenna 23C is listened in EAS receiver 23B and pulse), for example, the TR4024 pulse listening device of Checkpoint, but its EAS transmitter 23A ' is revised as emission 13.56MHz (sees Fig. 8, in the EAS transmitter 23A ' that revises, the radio frequency amplifier that is connected with Direct Digital 8.2MHz frequency synthesizer (DDS) is under an embargo (by the mark among Fig. 8 " X " expression), and outside 13.56MHz signal generator flows into bandpass filter (BPF)).Checkpoint EAS #410 test label 12 is used as target.

(2) " step listen " partly (Fig. 9), together with step listen antenna 30, in conjunction with EAS step listen receiver 24 use defer to ISO15693 RFID reader 22 (for example, the Philips remote reader),, for example, EAS step listen receiver is, as shown in figure 10, be revised as another receiver part of the TR4024 that forms EAS step listen receiver 24; Because RFID reader 22 (for example, the Philips remote reader) provides pumping signal 32, so the transmitter section 23A of EAS pulse listening system (perhaps transceiver) 23 is under an embargo (by the mark among Fig. 5 A " X " expression).Checkpoint EAS #410 test label 12 and Checkpoint RFID #551246 label 10 use as target.

Should be appreciated that Philips reader and Checkpoint TR4024 pulse listening system only as an example, and the present invention can implement by other conventional transceiver and reader.

As previously mentioned, exemplary EAS pulse listening system or transceiver 23 are to be used for Checkpoint Liberty ^TMThe standard electronic module TR4024 of production line.As shown in Figure 7, TR4024 comprises EAS transmitter 23A substantially and uses the EAS receiver 23B of digital signal processing (DSP) technology, together with direct digital frequency synthesis technology, realizes emission/receiving function.In addition, TR4024 supports the hardware and software of modification easily, so that finish the test that will describe in detail after a while.In addition, TR4024 has the ability to communicate by letter with other Checkpoint products by the internet.

Except EAS transmitter 23A is modified (seeing Fig. 8 EAS transmitter 23A ') for launching all transponder pulses with 13.56MHz fully, first (" notion ") part is listened to electron device (Fig. 7) by standard EAS pulse and is formed.Transmission mode is constant in other respects, and promptly dutycycle, pulse width and burst length remain unchanged.Then, this electron device be placed put in place and with Checkpoint Strata ^TMThe PX antenna equipment connects.System can detect Checkpoint EAS#410 test label 12.Especially, when label 12 is placed in 12 " apart from the time, electronic component is reported to the police.Test label 12 is parallel to antenna along the axis at 2-loop antenna top and moves.Label-Antenna Positioning is considered to help detect.The form that emission mode can be considered to amplitude code (ASK) is listened in pulse.Therefore, the test of this kind form is similar with the ISO15693 interrogator that is operated in 100% modulation rate.

Especially, implement this initial trial with check EAS ring with the 13.56MHz transmitter.Can think that the step listen operation under the method and 100% modulation index (on-off keying) is rationally equivalent.By moving with complete 100% modulation, system can be classified as the pulse listening system, rather than step listen.As shown in Figure 8, use switch 14 (be used in usually produce pulse among the EAS transmitter 23A listen to characteristic) to cut off the 13.56MHz transmitter, avoid during listening to, needing the harsh 13.56MHz rejection filter that requires.This test is the simple first step that realizes step listen under more typical 10% modulation index.

The EAS pulse listening system and the Checkpoint StrataPX antenna that only need modification in this experiment.It is necessary that electronic component is listened in change EAS pulse; Transmitter series is cut off the 13.56MHz signal driving power amplifier with the permission external feedback, and final driven antenna.Receiver and check algorithm are constant, that is, all pulse widths, RX sampling time and signal level remain unchanged.The structural drawing of transmitter 23A ' is listened in the EAS pulse that Fig. 8 shows modification.

In preferential direction, Checkpoint EAS #410 test label is placed in the interrogation.When label at Checkpoint Strata ^TMThe PX antenna 12 " within the time, the EAS system continue to report to the police.

The electromagnetic radiation that various management organizations regulation allows.There is huge difference between typical EAS frequency band that is allowed and the 13.56MHzISM frequency band.When providing same antenna formation emission 13.56MHz, in the electric current that allows, present 8.8x and increase.Utilize

Detection reaches maximal value 2.1x increment in detection to current function.Based on the conclusion of front, the maximum surveyed area of predicting each " door " is 25 ".The sideband requirement in the ISM 13.56MHz frequency band is not considered in this assessment.The rules problem more completely is discussed below.

In the test second (" step listen ") partly (Fig. 9) finished by EAS step listen receiver 24 (Figure 10) and RFID reader 22.EAS transmitter 23A does not need, and therefore disabled.In addition, EAS step listen receiver 24 is connected with little 3 circle circular loop antennas 30.This dispersion, receive only the quantity that antenna 30 reduces the 13.56MHz energy that is coupled to step listen receiver 24, and therefore reduce required receiver filtering level.RFID reader 22 is in order to " step " in the emission step listen in this is provided with.In addition, this reader 22 continues to provide its appointed function, promptly encourages and read ISO15693 RFID label 10.With the typical antenna that Q prototype antenna 28 replaces reader manufacturers to provide is provided.As described in detail later, need low Q antenna 28 to be provided at the fast rise and the fall time on modulation edge.These sharp edges are required to provide enough " step " before " listening to ".Test result shows that the 8MHz eas tag 12 place within 28,/30 six inch on the antenna causes and similar energy ring seen in the EAS system is listened in traditional pulse.Again, label 12 is placed in about all favourable position of antenna 28/30.Actual oscillograph track such as Figure 11 and shown in Figure 12.

Before the native system/method of discussion, provide the discussion of step listen methodology and ISO15693.

The step listen technology

ISO15693

The RFID agreement of standard, promptly ISO15693 has stipulated the method for RFID reader to label communication.Air interfaces specify use the reader of 13.56MHz carrier wave to label communication.Order from reader to label is established by the variation (also being " modulation edge " (modulation edges)) of all period interval the 13.56MHz carrier wave.These variations in the carrier amplitude, perhaps drop has constituted the basis of " step " in the step listen technology.So step listen can be considered to the secondary product of RFID ISO15693 standard.Yet, should be appreciated that as described in detail later, in the present invention 20, these variations or drop need " sharp keen " rather than slyness, and are called " decline transition " 32B (seeing Fig. 4 and Figure 13) hereinafter.One of key feature of the present invention 20 is modified to the sharp keen decline transition of this kind that provides in the pumping signal 32 32B for RFID reader 22 transmitters.

This ISO15693 carrier wave that has amplitude variations can be split as two different parts.First only is a constant amplitude RF carrier wave.And second portion is also at the on-off keying of 13.56MHz, and with first's homophase.It is possible separating according to the notion of this ISO signal of superposition theorem.Because eas tag will ring on its free-running frequency, irrelevant in case eas tag is brought into interrogation zone so with excitation frequency, in the order modulation along the exponential decay that 8MHz will take place on (drop of amplitude).As a result, the present invention 20 pumping signal 32 can be described to include the continuous signal of following composition: first unmodulated part 32A, sharp keen decline transition 32B, modulated part 32C and the sharp keen rising transition 32D that is followed by next unmodulated part 32A.

Can understand that RFID label 10 is with RFID response signal 34 responsing excitation signals 32, this RFID responds the variation of 34 signals based on a series of all period interval in the 13.56MHz carrier wave of label 10 receptions.On the contrary, whenever decline transition 32A excitation label 12, eas tag 12 is just launched its " ring " signal 36.Test specification RFID reader 22 and EAS step listen receiver 24 can within about 0.1 second, detect their labels separately.

Modulation edge and antenna Q

The ISO15693 standard code maximum on order modulation edge rise and fall time.This maximum constraints is easy to realize, yet what provide is circular modulation edge.These are along round more, and the EAS ring is difficult more.Therefore, step listen can not work to the reader/antenna of any ISO15693 of deferring to.

In order better to understand this point, the definition of Q must be discussed.Q is defined as " quality factor ", and is the tolerance of the acutance of frequency selectivity or antenna circuit peak value, and mathematical definition is:

Q＝f _cf÷BW (1)

Wherein, f _CfBe centre frequency or RFID reader transmitter frequency; And

BW is the bandwidth around centre frequency, and its response is not more than 3dB below the centre frequency of RFID reader antenna circuit.

Q also is considered to be in the tolerance of the storage of energy on the resonance frequency to energy consumption, in other words:

$Q={\mathrm{\ω}}_0\·\frac{L}{R}---\left(2\right)$

Wherein, ω ₀It is the resonance angular frequency of antenna circuit and L and R are the inductance and the resistance of antenna circuit.Should be appreciated that L and R only as an example, can use other antenna circuit configurations, wherein according to electric capacity (C), resistance (R) and/or inductance (L) definition Q.

Timeconstant (being defined as response rises/drop to 36.8% required time of its initial value) and frequency of utilization f ₀The Q of antenna circuit between have linear relationship.Particularly,

$\mathrm{\τ}=\frac{Q}{\mathrm{\π}\·f_0}---\left(3\right)$

Perhaps

Q＝τ·π·f ₀ (4)

Select rising/fall time of similar TR4024 pulse/listening system (τ ≈ 100ns), therefore provide,

Q＝4.3

This low value of Q requires to need different antennas, and this antenna is different from the standard antenna that RFID reader 22 is provided, or requires indirect specified standard antenna rising/fall time by ISO15693.

Step listen has been pointed out another Q requirement.In order to work at EAS and RFID wavestrip, antenna system need fully transmit energy on broadband spectrum.Clearly, traditional EAS wavestrip is distributed in 7.4MHz to 8.7MHz.So this antenna system need be operated in more than the 7.4MHz to 13.56MHz.

Q＝f _cf÷BW (1)

Perhaps

Q＝1.1

For the reception of EAS, preferred stand-alone antenna, rather than further reduce Q and the expensive emitted energy of waste.This has also alleviated the load of the required 13.56MHz rejection filter of EAS step listen receiver 24.

It should be noted that the Q that reduces antenna system need insert the resistance in series that meets tours antenna.But increase this loss of transmitter power compensate for emission acc power.Can increase the cost of all over products like this and electromagnetic radiation (electromagnetic radiation is described after a while in the text) is produced passive influence.

The wave filter requirement

In order to detect the 8MHz ring, the EAS receiver need filter the energy from ISO15693 reader transmitter.This huge 13.56MHz signal with respect to faint EAS ringdown, will make receiver blinding arbitrarily easily by its huge amplitude.In essence, do not need excitation, and need response.

The wave filter that need shift out the 13.56MHz carrier wave is difficult to realize.EAS and RFID wavestrip are less than an octave of separating.Circuit theory regulation filter transmission band needs many more limits (circuit component) to finish the decay of some the closer to its stopband.Because bandwidth and the inverse relation between the response time, required a considerable amount of limits will have a negative impact to transient response.Clearly, during modulation step, the energy attenuation of filter element can be covered the ring of eas tag.The general solidnever of problem is towards listening system.

Solution is for using active filter at the key position that runs through EAS step listen receiver 24 paths.Multiple feedback bandpass filter (MFBP) reduces transient response, but keeps frequency response characteristic.By using active filter,, also be reduced even the needs of inductance are not eliminated.

Active filter needs operational amplifier.Because the price of operational amplifier is more much higher than inductance, the cost of electronic original part increases.Operational amplifier is also to any system contribution broadband noise.By the effectiveness that this wave filter/feedback is carried out, the noise of this increase is in passband.So, should use the lowest noise operational amplifier (

).Also need very fast conversion ratio (slew-rate) (〉 500V/us).

Compromise is for using several series resonant circuits that are connected to MFBP filter input end and circuit ground.This will reduce the load of filtering active part, but prolong transient response.Usually, inductance has tolerant poor, need to be necessary adjustable inductance and/or electric capacity.

At last, the best approach of minimizing wave filter requirement is to use the stand-alone antenna that is used to receive the EAS signal.The coupling that RFID antenna and EAS only receive between the antenna can be minimized under the sensing range that does not influence system.

What is the EAS frequency?

Global management organization is limited in the EAS operation in the specific frequency band.These restrictions are applied to system transmitter, rather than passive eas tag.This label can be on the optional frequency that we wish resonance.

In the selection of frequency, need to consider some and performance-relevant problem.Near the natural resonance frequency of label, label will be stored many more energy to excitation frequency (transmitter) more.The sensing range of system is the direct result of the energy storage of label.The resonance frequency of this physical law hint label is in or near 13.56MHz, i.e. unique driving source in the step listen operation.

Yet, have some balances.Use resonance frequency to be in or produce maximized energy storage and need not special filtering near the eas tag of 13.56MHz, this is appreciable benefit.Yet difficulty is the detection of the exponential decay of eas tag.Covered the EAS ring by the RFID reader transmitter that the effectiveness of ISO15693 is moved continuously.Step listen requires to move the existence of seeking eas tag when jumping in RFID order modulation step or amplitude.Even, in this transition time, also be difficult to the tiny release of observation tag energy when excitation and resonance frequency the time not by a long sight.Make the frequency unanimity will further increase this problem.

The eas tag that uses resonance frequency to be different from 13.56MHz significantly causes the energy storage much lower.Yet this method has an important benefit.The frequency of separating EAS and RFID greatly, the requirement that alleviates wave filter.Remove this benefit, conclusion is that to exchange easier filter specification for label signal be not worthwhile mean method.Use is not a kind of good solution than the eas tag of low resonant frequency.

Existing EAS frequency band (7.4MHz to 8.7MHz) is the optimal selection of step listen operation.Label can be stored the energy of gratifying quantity from the pumping signal of 13.56MHz.Yet, ringing frequency apart from 13.56MHz enough far being detected.The demand harshness of EAS wave filter, but can realize.

Use this eas tag to also have other benefit.After EAS electronic component exploitation for many years, understood the tag system interaction more.Existing electronic circuit and algorithm can be transplanted to the step listen system.In fact, as mentioned above, during notion part and step listen part, all use the EAS receiver of revising.

The step listen test detail

In this experiment, uses three key hardware elements: Philips SLRM900 I code (code) reader (being used for RFID reader 22), the TR4024 (being used for EAS step listen receiver 24) that revises and antenna to (be used for RFID reader 22 28 be used for EAS step listen receiver 24 30).The laboratory equipment of Shi Yonging comprises double loop power supply, notebook computer, function generator (function generator) and oscillograph in addition.Structural drawing as shown in Figure 9.

Philips RFID reader

Philips SL RM900 I*code remote reader module offers the user as the part in the whole SL EV900 assessment tool bag.Kit also comprises straight-flanked ring antenna and matching network, demoware and I code RFID label selected works.

The antenna that provides has and is about 27 Q.According to aforesaid paragraph, this high quality factor makes modulation along detecting required circle than step listen.Describe in the text after a while and replace antenna and matching network.

The demoware of issuing together with kit is I code Demo v3.03.Notebook computer is that initial configuration and operation are necessary.

Run through the step listen experiment, I code I label is used to continuous checking R FID performance.

Reader 22 self is configured to 10% modulation index, and has 3.75 watts output power; Therefore Philips SL RM900 I*code remote reader has 0-4 watt adjustable output power range, but is test purpose, and output power remains on 3.75 watts, and this is provided with constant in the whole test.System works is in " reading sequence number " pattern.And though that several digital signal is used to make the TR4024 pulse listen to receiver in the non-insertion mode is synchronous, and reader hardware is not changed.

TR4024 revises

Because the energy source of step listen is from RFID reader 22, thus do not need TR4024 transmitter 23A, and therefore be under an embargo as shown in figure 10.Should be noted that TR4024 transmitter level simply is set to zero deficiency so that transmitter 23A forbids.This is set to 0VDC with power field effect transistor direct current guide rail (power FET DC rails).Still some flows through from the FET door and flows out to antenna 30.This causes some misleading results in early days in test.In addition, shunt capacitance/inductive bank (C112/L10, not shown) is removed to stop the EAS ring to be returned and passes the transmitter 23A that forbids.

It is at its acceptor circuit that the major part of TR4024 is revised.Main cause is the 13.56MHz pumping signal 32 that leaches from RFID reader 22.In addition, finish with the order modulating pulse of RFID reader 22 by the receiver ON/OFF gating (gating) of the FPGA among the TR4024 (field programmable gate array) control usually.

Wave filter is placed on several positions of running through receiver path.From antenna port,, on the L3 (not shown), produce the 13.56MHz antiresonant circuit by increasing shnt capacitor.Because only need in the input of diversity device, therefore input to output place and place wire jumper at the K6-A (not shown).Increase filter plate replaced C 192 (not shown).This daughter board is obtained from the part 4 of " RFID/RF-EAS CombinedSystems " by the design of Scientific Generics company.In order to realize the gating function of RFID reader, remove the R79 (not shown) and to replace from the wire jumper of RFID reader.This gating signal is the order modulation.In essence, the negative edge of modulation signal, i.e. " step " activates mixer/demodulator U17.Rising edge is forbidden this chip.

Phased array simulation software (PASS) configuration is set to maximum receiver yield value and zero transmitter output.Because only need the simulation part of receiver, therefore, the setting of all other palms (palm) all is incoherent.

In order to help EAS to detect, local oscillator is arranged on the fixing frequency.This is provided with the resonance frequency that frequency is in close proximity to eas tag 12.This makes that the base band ring is more prone to go up in sight at oscillograph 13 (Fig. 9).This is an advantage for receiver, but is impossible when using various eas tag.Signal is provided by the external signal generator (for example, function generator) that is connected with TP7 (not shown) among the TR4024.Removing the R41 (not shown) is coupled with airborne local oscillator (U8, not shown) preventing.

EAS step listen reader 24 need know when " listen to " the label ring.In order to reach this purpose, use the order modulation signal in the RFID reader 22.This signal is connected to AGC (automatic gain control) pin of TR4024 mixer/demodulator U17 (not shown).These method of attachment right and wrong are plug-type, therefore do not need impact damper.The reverse form of this signal is also referred to as " outside LO " in order to gating external signal generator (for example, function generator).This makes the phase relation between order modulation and the local oscillator all be consistent in each " step ".In these signals any is used for triggering oscillograph 13.

It is right to hang down Q RFID antenna and only receive the EAS antenna

The Q of required antenna directly relates to the signal that passes through necessity wherein.RFID reader transmitter is necessary to provide the pumping signal 32 with sharp keen modulation edge.Step listen relies on these " steps " along last abundance.As described above, the Q of the antenna that provides of RFID reader 22 is approximately 27.This provides BW and has only 502KHz, causes the minimum rise time, the t of arbitrary signal _r(signal transitted to for 90% required time from 10% of its final value) is:

$t_r=\frac{1}{\mathrm{\π}\·f_0}---\left(5\right)$

t _r＝0.6us

This kind antenna can not provide step listen.

New antenna and antenna circuit are necessary.Figure 14 has described a preferred embodiment of this new antenna/antenna circuit.When using " falling Q " resistor 40 to set up to be used for the suitable matching network 38 of RFID reader antenna 28, at centre frequency (f _Cf) under the 13.56MHz, inductance measuring (L) and resistance (R), then user's formula (2) is calculated Q.In case antenna 28 and fall Q resistance and be connected to matching network just records the frequency response of combiner circuit.When pumping signal 32 frequency departure 13.56MHz,, response is from being in/decaying to either direction near the harmonic peak (peak resonance) of 13.56MHz.The bandwidth of circuit (BW) is the frequency of the little 3dB of response ratio peak value.According to equation (1), calculate Q and with the comparison that obtains according to equation (2), and two calculated values are approaching.

The rise time of TR4024 transmitter belongs to the 100ns magnitude.Being inserted into the Q that equation (2) draws antenna is 4.26.Relation is that this low Q antenna suffers damage the sensing range of rfid system.Actual 6.4 the compromise Q that uses in experiment.Fall Q resistor (1%) by increasing the useful series connection that can reduce antenna circuit Q value, the Q value is as far as possible near 4.26.Sharp keen negative edge in the pumping signal 32 appears in the result.Notice can utilize the scope of Q value, for example, 6-7, wherein maximum Q value is required and keeps sharp keen modulation edge to limit, and the ability that minimum Q value is handled in-band noise by the RFID reader limits, because Q is low more, bandwidth and in-band noise are big more.

The actual measurement Q of new antenna is about 6.4.This will calculate the rise time of 150ns, approach the target of 100ns.The waveform that low as shown in figure 13 Q antenna place is measured.

As previously mentioned, only finish low Q by falling the Q resistor in each limit increase series connection of inductive coil.The R that increases, and the big fact of change of L in the new loop necessitate new impedance transformer network.Identical topology is used in the new coupling.Especially, incorporate differential L type network 38 (Figure 14) that antenna impedance are converted to 200 ohm (real numbers (rea lonly) only, that is, resistive) into.Balanced-to-unbalanced transformer (balun) 42 (preferred, Ruthroff balun) is converted to single-ended 50 ohm load (also only real number) with these 200 ohm of differential impedances, can be driven by the concentric cable (not shown) by 50 ohm transmitter.The synoptic diagram of new as shown in figure 14 antenna/matching network.

Balun42 is that the standard of RF emission is used, because it never provides balance transmission network (input wireless signal) to the interface of balanced system (RF detuner), and hence obtain one's name " balanced-unbalanced ".Especially, antenna structure is wired tours antenna (balance), yet 22 outputs of RFID reader need single-ended over the ground terminal (single-ended termination) (imbalance).Ruthroffba lun utilizes 10 circle imbalances to 20 circle balances.Usually, L type network is converted to other impedances (for example, only real number) with some impedances (real number and reactive (real and reactive)).Especially, the output of RFID reader 22 should be seen 50 ohmages (only real number).Balun with impedance from unbalanced 50 ohm 200 ohm of being converted to L type network 38 balances.

For the ring of " listening to " eas tag, use independent receiving antenna.The purpose of stand-alone antenna is to reduce the energy of the 13.56MHz that is coupled to the EAS receiver.Only as reminding, the eas tag ring is at the natural resonance frequency of label, perhaps 8.2MHz usually.In bigger 13.56MHz RFID signal was arranged, the ability of checking this small-signal was the key of step listen operation.By using stand-alone antenna, reduce the burden that the RFID energy that is coupled to the EAS receiver has reduced the receiver wave filter.

New antenna 30 is 5 inches of 5 circles (coils of 5 ") diameter.Select this number of turn, so synthetic antenna impedance and Checkpoint Liberty ^TMThe impedance phase that TR4024 ought see usually in the PX 2-annular seemingly.

Aspect the sharp keen decline transition 32B of realization, the modulation ratio of 13.56MHz carrier frequency is used the better of higher carrier frequency work.Can know in Figure 15 and see that when modulation took place, carrier amplitude was weakened in the single cycle of 13.56MHz signal, therefore obtain the sharp keen slope between unmodulated part 32A and the modulated part 32C.On the contrary, higher carrier frequency (for example, 20MHz) needs the middle amplitude in several cycles obtaining (modulating part 32A ' never) modulated part 32C ' before; In that event, not too sharp keen and round (and undesirable) decline transition 32B ' appears.Figure 16 has described with traditional RFID reader and has compared, the very fast energy attenuation of the RFID reader 22 of use the present invention's 20 modification (when modulation takes place).

European standard electromagnetic radiation (Regulatory-European Radiated Emissions)

The EAS excitation of typical relatively 7.4-8.7MHz, when when 13.56MHz is energized, the energy that the eas tag storage is less.Yet some of them can be overcome by bigger excitation, the managed mechanics limit of its maximal value.Following length attempts to quantize the increment of the antenna current that allowed when using the 13.56MHz energy source.

Between the magnetic field of the magnetic field of 8MHz EAS bandwidth assignment and 13.56MHz ISM bandwidth assignment, there is greatest differences.This ISM band is immoderate (unlicensed), and therefore allows bigger field.Because different frequencies and relevant pulse mode, directly relatively limit value is inapplicable.Yet,, can reach a result by in conjunction with test data and main field formula.Suppose that what use in the comparison is identical antenna.

Regulation and stipulation for the EAS frequency band, at 30 meters, allows to reach 51dBuV/m.The detecting device that uses is the quasi-peak value type.At RFID ISM frequency band, 30 meters limit values are 84dBuV/m.This detecting device is similarly the quasi-peak value type.

" the impairment factor " of quasi-peak detector tolerance distinctive signal.This detecting device is considered the dutycycle and the pulse repetition rate (PRF) of signal.PRF is low more, relative peak tolerance, and quasi-peak value tolerance will be low more.For the CW signal, as broad as long between quasi-peak value tolerance and the peak measure.Typical C heckpoint Strata ^TMTransmission mode presents between peak value and quasi-peak value tolerance and differs 5.4db.

In addition, need to consider frequency effect.The far field magnetic field formula that uses is:

$H_{\mathrm{\θ}}=\frac{{-\mathrm{\π}}^2\·a^2\·I\·e^{-j\·k\·r}\·\sin \mathrm{\θ}}{{\mathrm{\λ}}^2}---\left(6\right)$

Wherein, H _θBe magnetic density, and λ is wavelength (for example, 22.1 meters).Consider to rely on wavelength in the denominator, when using the 13.56MHz frequency band, compare, in magnetic field, have the increment of 8.7dB with 8.2MHz.Form 1 calculates the current increment that is allowed.

Form 1

The Europe electromagnetic radiation level compares, and 8.2MHz is to 13.56MHz

Frequency band	Quasi-peak value limit value (30 meters)	The peak value limit value changes
			8.2MHz EAS frequency band	51dBuV/m	56.4dBuV/m
13.56MHz ISM frequency band	84dBuV/m	84dBuV/m
				Gain	27.6dB
	Frequency effect	-8.7dB
				Network (Net)	18.9dB

In a word, transmitter current can be increased 18.9dB or 8.8x.

Up to the present discuss and only concentrate on the 13.56MH carrier wave.There is so-called sideband in strict limit value, perhaps the energy that is launched with the frequency that is different from 13.56MHz ± 7kHz.Especially, limit value drop 33.5dB ± energy beyond the 7kHz bandwidth.At distance carrier wave 150kHz place, the limit value other 10dB that drops.When increasing transmitter current or be sharp keen modulation when using low Q antenna, these sidebands limit and must be considered.Up to now, when the Q antenna was hanged down in use, experiment is presented at sideband did not have detectable increment.

Obstacle

Low Q antenna allows more wideer band noises to enter the RFID receiver.Suppose that the small drop in the RFID detection is owing to the lower antenna current from transmitter, and do not have broadband noise to enter receiver.Definite RFID performance degradation is unknown.The number percent that descends because of the receiver noise performance that increases is unknown.

Low Q antenna also will be wasted energy.The drop of antenna current can be drawn by following formula:

$\mathrm{\ΔI}=\sqrt{\frac{Q_2}{Q_1}}---\left(7\right)$

$\mathrm{\ΔI}=\sqrt{\frac{6.4}{27}}$

$=0.49$

The part of the energy of this waste can be remedied by active switch Q resistor (switching Qresistors).Effectively change and can change amplitude with antenna parallel resistor device value, and Q.This causes the fixed antenna (and Q) of 100% amplitude.In when modulation,, can connect booster resistor to reduce by 18% amplitude according to the ISO15693 standard.The resistance that increases reduce antenna Q and, more importantly, provide the sharp keen modulation edge that the step listen operation is wished.It should be noted that any resistance of connecting with antenna can be converted into equivalent resistance in parallel.When modulation can reformedly be this equivalent resistance in parallel.The synoptic diagram of this conception of species as shown in figure 17.At last, D level amplifier can be used as transmitter, further reduces " waste " energy.

For the convenience of carrying out, use the Generics wave filter among the TR4024 of modification.Decay at the 13.56MHz place is about 20dB.Do not observe the insertion loss.It should be noted that as the part of this kind wave filter, Generics recommends to revise the output transformer turn ratio.This is not changed included by step listen.Therefore, performance of filter can be modified.

Can improve with better wave filter realizability.Change immediately and will realize completely that Generics changes.In addition, active filter need be placed on the several stages that runs through receiver.Should merge multiple feedback bandpass filter (MFBP) and low noise high speed operation amplifier.Show when EAS uses identical antenna with rfid system, need the decay of 100dB.Follow stand-alone antenna, the quantity of required filtering tails off.Say that exactly the amount of required filtering depends on the coupling coefficient between two antennas.As all pulse listening systems, the transient response of any wave filter is vital for the receiver architecture based on time domain.

Comprehensive achievement of step listen depends on EAS receiver wave filter.Its ability of removing the 13.56MHz carrier wave directly influences EAS and detects distance.When antenna structure is determined, and coupling coefficient can calculate accurate wave filter requirement when determining.As initial step, the Generics wave filter should be carried out completely.According to this information, can determine that performance of filter and EAS detect the correlativity between the distance.The strong active filter of recommending is carried out.

As previously shown, antenna Q is extremely important.RFID reader-tag system needs high relatively Q transmitter/antenna to give the label energy supply.On the contrary, according to the frequency separation of EAS and RFID frequency band, EAS receives and relies on low Q system.The active Q-switching antenna helps to solve this two problems.

Be to be understood that, although when the modulation transition is that " decline transition " 32B (wherein, 13.56MHz signal is less than " rising transition ") time, preferred embodiment has the EAS receiver to be listened to, but comprises that the detection of natural response of eas tag is also within the present invention 20 maximum magnitude because of rising transition 32D.Preferably, this rising transition 32D is because the same cause of above-mentioned relevant decline transition 32B also is sharp keen.

Should be noted that equally test shows EAS step listen receiver 24 and RFID reader 22 can differ their labels separately of detection in about 0.1 second each other.Because the step listen operation is the synchronous operation of RFID and EAS, therefore, in the RFID operation, there is not performance loss.For this system user, this is shown as real-time function.In addition, because have only individual transmitter (for example, RFID reader 22) to be used to the functional of RFID and EAS, this causes that cost savings and package dimension reduce.On the contrary, when other attempted Coupled RF ID and EAS system, transmitter separately uses to be shared or stand-alone antenna.Disturb for fear of RF, these systems must be with the time division multiplex form by sequential operation.In essence, this configuration has only a system, and RFID or EAS can work at any time, and another system then waits for.The result is that the performance of two systems all reduces, and relatively poor real-time function.

Although describe the present invention in detail, it will be understood by those skilled in the art that and to do various variations and change to the present invention and do not depart from the spirit and scope of the invention with reference to particular instance of the present invention.

Claims (43)

1. be used for detecting from being adjusted at first signal of the EAS resonant circuit label of the frequency of EAS frequency band with from the system of the secondary signal of the RFID label that is adjusted to the frequency in the RFID frequency band, described system comprises:

Be used to launch the transmitter that transmits, described transmitting comprises the carrier signal of frequency in described RFID frequency band, and described carrier signal is the modulated amplitude that is used for sending to described RFID label order, described transmitting comprise when described and transmitting when touching described EAS resonant circuit label, causes that described eas tag launches the modulation edge of described first signal;

First receiver, described first receiver is adjusted to the frequency in described EAS frequency band, is used to receive described first signal, and described first signal comprises the natural response of described EAS resonant circuit; And

Second receiver, described second receiver is adjusted to the frequency in described RFID frequency band, is used to receive described secondary signal.

2. according to the system described in the claim 1, it is characterized in that described transmitter and described second receiver comprise a RFID reader.

3. according to the system described in the claim 2, it is characterized in that described transmitter and described second receiver are shared second antenna, described second antenna is used to launch and describedly transmits and receive described secondary signal.

4. according to the system described in the claim 2, it is characterized in that, described second antenna of the same use of described first receiver, described second antenna is in order to receive described first signal.

5. according to the system described in the claim 4, it is characterized in that, comprise about 6.4 figure of merit Q as described second antenna of common antenna.

6. according to the system described in the claim 5, it is characterized in that described common antenna comprises differential L type network.

7. according to the system described in the claim 6, it is characterized in that described common antenna also comprises balance one balun that is used for differential impedance is converted to single-ended load.

8. according to the system described in the claim 5, it is characterized in that described antenna comprises the Q-switch circuit.

9. according to the system described in the claim 4, it is characterized in that described first receiver comprises receiver path, and described receiver path comprises at least one active filter to leach described transmitting.

10. according to the system described in the claim 4, it is characterized in that described first receiver comprises receiver path, and described receiver path comprises series resonant circuit to leach described transmitting.

11. the system according to described in the claim 3 is characterized in that, described first receiver comprises first antenna that is different from described second antenna.

12. the system according to described in the claim 11 is characterized in that, described first antenna comprises a plurality of rings.

13. the system according to described in the claim 12 is characterized in that, described a plurality of rings comprise five rings.

14. the system according to described in the claim 1 is characterized in that, described transmitter is set to 10% modulation index.

15. the system according to described in the claim 1 is characterized in that, the output power of described transmitter is 3.75 watts.

16. the system according to described in the claim 1 is characterized in that, described modulation is along comprising the modulation edge that descends.

17. the system according to described in the claim 3 is characterized in that, described EAS frequency band comprises the frequency range of 7.4MHz to 8.7MHz.

18. the system according to described in the claim 17 is characterized in that, the described frequency in described EAS frequency band is approximately 8.2MHz.

19. the system according to described in the claim 3 is characterized in that, the described frequency in described RFID frequency band is 13.56MHz.

20. the system according to described in the claim 11 is characterized in that, described transmitter, described first receiver and described second receiver are included in the single shell.

21. the system according to described in the claim 20 is characterized in that, described single shell is included in the column among two safe columns of commercial center porch.

22. the system according to described in the claim 11 is characterized in that, described transmitter, described first receiver and described second receiver are included in the column among two safe columns of commercial center porch.

23. the system according to described in the claim 16 is characterized in that, described transmitting also comprises the first unmodulated part, described decline modulation edge part, modulated part, rising modulation edge part and the second unmodulated part.

24. the system according to described in the claim 23 is characterized in that, described transmitting comprises the frequency of 13.56MHz.

25. the system according to described in the claim 24 is characterized in that, described decline modulation is along comprising the sharp keen amplitude decrement that is between the described first unmodulated part and the described modulated part.

26. the system according to described in the claim 24 is characterized in that, described rising modulation is along comprising the sharp keen amplitude increment that is between the described modulated part and the described second unmodulated part.

27. the system according to described in the claim 24 is characterized in that, described transmitter is set to about 10% modulation index.

28. be used for detecting simultaneously from being adjusted to, said method comprising the steps of at first signal of the EAS resonant circuit label of the frequency of EAS frequency band with from the method for the secondary signal of the RFID label that is adjusted to the RFID frequency band:

(a) carrier signal of Modulation and Amplitude Modulation frequency in described RFID frequency band transmits with formation, and described transmitting comprises the modulation edge;

(b) described the transmitting of emission to touch described EAS resonant circuit label and described RFID label;

(c) by the described described modulation edge that transmits of described EAS resonant circuit label response, launch described first signal, described first signal comprises the natural response of the described resonant circuit in the described EAS resonant circuit label;

(d) by described the transmitting of described RFID label response, launch described secondary signal; And

(e) detect described first and second signals.

29. the method according to described in the claim 28 is characterized in that, the described step that detects described first and second signals comprises that use antenna separately receives described first and second signals.

30. the method according to described in the claim 28 is characterized in that, described EAS frequency band comprises the frequency range of 7.4MHz to 8.7MHz.

31. the method according to described in the claim 30 is characterized in that, the described frequency in described EAS frequency band is approximately 8.2MHz.

32. the method according to described in the claim 28 is characterized in that, the described frequency in described RFID frequency band is 13.56MHz.

33. the method according to described in the claim 28 is characterized in that, the described step of the described carrier signal of Modulation and Amplitude Modulation comprises carries out 10% modulation index.

34. the method according to described in the claim 28 is characterized in that, launches the described described step that transmits and comprises with described the transmitting of 3.75 watts output power emission.

35. the method according to described in the claim 29 is characterized in that, the described step that detects described first and second signals comprises first signal that filters described reception by described antenna separately on one's own initiative.

36. the method according to described in the claim 35 is characterized in that, the described step that detects described first and second signals is included in switch Q resistor in the described antenna separately.

37. the method according to described in the claim 28 is characterized in that, the described step of the described carrier signal of Modulation and Amplitude Modulation comprises:

Unmodulated continuous carrier signal is provided;

The described continuous carrier signal of Modulation and Amplitude Modulation is to form the modulated carrier signal of amplitude and when described Modulation and Amplitude Modulation begins and form in the described modulation edge one, wherein to produce sharp keen amplitude decrement; And

Discharge described Modulation and Amplitude Modulation to produce described unmodulating carrier signal and when carrying out described release, wherein to form another modulation edge when described.

38. the method according to described in the claim 37 is characterized in that, discharges described amplitude-modulated described step and comprises that also the sharp keen increment of setting up amplitude is to form described another modulation edge.

39. the method according to described in the claim 37 is characterized in that, described continuous carrier signal comprises the signal of 13.56MHz.

40. the method according to described in the claim 39 is characterized in that, described Modulation and Amplitude Modulation comprises 10% modulation index.

41. be used for detecting simultaneously from being adjusted to, said method comprising the steps of at first signal of the EAS resonant circuit label of the frequency of EAS frequency band with from the method that is adjusted in the secondary signal of the RFID label of RFID frequency band medium frequency:

(a) generation has transmitting of following feature: the first oscillator signal part with first amplitude, has the second oscillator signal part less than second amplitude of described first amplitude, and wherein between described first amplitude and described second amplitude, sharp keen decrement is arranged, and the 3rd oscillator signal part, and wherein between described first amplitude of described second amplitude and described the 3rd oscillator signal, sharp keen increment is arranged with described first amplitude;

(b) described the transmitting of emission to touch described EAS resonant circuit label and described RFID label;

(c) by the described described modulation edge that transmits of described EAS resonant circuit label response, launch described first signal, described first signal comprises the natural response of the described resonant circuit in the described EAS resonant circuit label;

(d) by described the transmitting of described RFID label response, launch described secondary signal; And

(e) detect described first and second signals.

42. the method according to described in the claim 41 is characterized in that, described first oscillator signal, described second oscillator signal and described the 3rd oscillator signal comprise the frequency of 13.56MHz.

43. the method according to described in the claim 42 is characterized in that, described transmitter configuration is 10% modulation index.

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