CN102004933B - Difference frequency mutual interference preventing method of RFID (Radio Frequency Identification Devices) system and difference frequency mutual interference preventing RFID system - Google Patents
Difference frequency mutual interference preventing method of RFID (Radio Frequency Identification Devices) system and difference frequency mutual interference preventing RFID system Download PDFInfo
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- CN102004933B CN102004933B CN 201010592552 CN201010592552A CN102004933B CN 102004933 B CN102004933 B CN 102004933B CN 201010592552 CN201010592552 CN 201010592552 CN 201010592552 A CN201010592552 A CN 201010592552A CN 102004933 B CN102004933 B CN 102004933B
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Abstract
The invention provides a mutual interference preventing method of an RFID (Radio Frequency Identification Devices) system, and a mutual interference preventing RFID system. An interference signal can be generated between the carrier frequency of each reader-writer antenna and an adjacent reader-writer antenna when the RFID system works; and the carrier frequencies of two adjacent reader-writer antennae are differentially set so that the frequency of the interference signal generated by the differentiation of the carrier frequencies of the two adjacent reader-writers is higher than the cut-off frequency of a detecting postpositional low-pass filter of a reader-writer receiving circuit when the two adjacent reader-writer antennae work together, that is to say, the interference signal is effectively removed, therefore a really needed baseband signal sent by an RFID label is demodulated. The invention solves the problem of unstable or false label read-write caused in such a way that derived frequency is generated due to the mutual interference of the adjacent reader-writer antennae when a plurality of the reader-writer antennae are densely distributed and work together.
Description
Technical field
The present invention relates to the REID field, particularly a kind of rfid system anti-mutual interference method and a kind of anti-mutual interference rfid system.
Background technology
At present, the RFID technology emerges in an endless stream in the application of all trades and professions.In the orientation management system of being made up of a plurality of rfid interrogators, each read write line respectively carries antenna; And when the antenna dense distribution of a plurality of read write lines and when using simultaneously, will inevitably produce the problem of disturbing mutually between each antenna.The generation of disturbing problem mutually can finally cause the failure of read write line read write tag, causes the RFID orientation management system malfunctioning.
In prior art solutions, can in the same area, use simultaneously in order to guarantee a plurality of read write lines, and no phase mutual interference between the antenna of each read write line, the common method that adopts is: one, control the distance between each antenna; Two, the emissive power of control carrier wave is to control its effectively coverage of read-write.The effect of two kinds of methods is equal to, and controls the coverage between two antennas exactly.But when the antenna dense distribution, and the position of antenna be can't change the time, and above method just can't have been proved effective.So the method for prior art can't thoroughly solve the problem of disturbing mutually between a plurality of antennas.
Summary of the invention
The technical problem to be solved in the present invention is to provide a kind of rfid system anti-mutual interference method and a kind of anti-mutual interference rfid system, the problem that each read write line institute disturbs mutually with generation signal between the antenna so that a plurality of read write lines are worked at the same time in the rfid system that solves prior art.
For solving the problems of the technologies described above, the invention provides a kind of anti-mutual interference rfid system, comprise: two or more rfid interrogators and corresponding to the electronic tag of each described rfid interrogator, described read write line has the rearmounted low-pass filter of detection, described different read write lines institute with the difference of the carrier frequency of antenna greater than described all read write lines with the cutoff frequency of detection postposition low-pass filter.
Optionally, the carrier frequency of described electronic tag is 125kHz-135kHz, and the carrier frequency that described reading and writing device antenna provides is 125kHz-135kHz.
Optionally, the cutoff frequency of the rearmounted low-pass filter of described detection is greater than the fundamental frequency of electronic tag modulating baseband signal.
The present invention also provides a kind of rfid system anti-mutual interference method, may further comprise the steps:
Two or more rfid interrogators are provided, and described read write line has the rearmounted low-pass filter of detection;
The carrier frequency of described reading and writing device antenna is set, make described different read write line with the difference of the carrier frequency of antenna greater than described all read write lines with the cutoff frequency of the rearmounted low-pass filter of detection.
Optionally, the carrier frequency of the electronic tag of described rfid system is 125kHz-135kHz, and the carrier frequency that described reading and writing device antenna provides is 125kHz-135kHz.
Optionally, the cutoff frequency of the rearmounted low-pass filter of described detection is greater than the fundamental frequency of electronic tag modulating baseband signal.
Rfid system anti-mutual interference method provided by the present invention and anti-mutual interference rfid system, when working, rfid system can produce undesired signal between the carrier frequency of each read write line and the adjacent reading and writing device antenna, differentiation arranges the carrier frequency of two adjacent reading and writing device antennas, when two adjacent reading and writing device antennas are worked simultaneously, the undesired signal frequency that the differentiation of two adjacent read write line carrier frequencies produces is greater than the rearmounted low pass filter cutoff frequency of detection in the read write line receiving circuit, namely remove undesired signal effectively, thereby demodulated the baseband signal that the RFID label of real needs sends.The invention solves a plurality of reading and writing device antennas when dense distribution is also worked at the same time, adjacent antenna is disturbed the frequency that causes deriving mutually and is produced, and causes the unstable or wrong problem of label read-write.
Description of drawings
Fig. 1 is the work synoptic diagram of rfid interrogator;
Fig. 2 is the work synoptic diagram of two rfid interrogators;
Fig. 3 read write line A carrier frequency is f
1=125kHz, read write line B carrier frequency is f
2Spectrogram during=128kHz before the envelope detection;
Fig. 4 read write line A carrier frequency is f
1=125kHz, read write line B carrier frequency is f
2Spectrogram during=128kHz after envelope detection and the low-pass filtering;
Fig. 5 read write line A carrier frequency is f
1=125kHz, read write line B carrier frequency is f
2Spectrogram during=135kHz before the envelope detection;
Fig. 6 read write line A carrier frequency is f
1=125kHz, read write line B carrier frequency is f
2Spectrogram during=135kHz after envelope detection and the low-pass filtering.
Embodiment
For above-mentioned purpose of the present invention, feature and advantage can be become apparent more, below in conjunction with accompanying drawing the specific embodiment of the present invention is described in detail.
Be to be illustrated by preferred embodiment below, the present invention is not limited to this specific embodiment certainly, and the known general replacement of one of ordinary skilled in the art is encompassed in protection scope of the present invention far and away.
Secondly, the present invention utilizes synoptic diagram to describe in detail, and when the embodiment of the invention was described in detail in detail, for convenience of explanation, synoptic diagram was disobeyed the local amplification of general ratio, should be with this as limitation of the invention.
Please referring to Fig. 1, Fig. 1 is the work synoptic diagram of rfid interrogator.The coverage of aerial signal when dotted portion is reading and writing device antenna 102 work among Fig. 1.Suppose the height of electronic tag 101 relative reading and writing device antennas 102 in read-write scope, this electronic tag 101 can be read and write in the scope shown in frame of broken lines so.Because be that single read write line works independently, obtain pure label baseband signal through behind envelope detection and the rearmounted low-pass filter, so can the be normally stable label that carries out of read write line is read and write.
Please referring to Fig. 2, Fig. 2 is the work synoptic diagram of two rfid interrogators.As shown in Figure 2, two identical or approaching read write line A and read write line B of carrier frequency are placed on together, and distance is very near between the antenna 202 that its difference is corresponding and the antenna 302.As can be seen from the figure, when two read write lines were worked simultaneously, the signal cover that its antenna 202 and antenna 302 send overlapped.Therefore when antenna 202 and antenna 302 are worked simultaneously, its separately signal cover in addition reached the other side's electronic tag position.So when read write line A and read write line B worked simultaneously, antenna 202 and antenna 302 not only can both receive the signal that electronic tag 201, electronic tag 301 send, and can also receive the carrier signal that the other side's antenna sends; A plurality of like this signals are easy interfering with each other very just.
The rfid system anti-mutual interference method and the anti-mutual interference rfid system that adopt the present invention to propose then can be prevented the generation that stop signal is disturbed mutually fully.Its core concept is by make difference on the frequency between two reading and writing device antennas, and the difference that makes frequency greater than read write line with the cutoff frequency of the rearmounted low-pass filter of detection, the undesired signal of deriving out so will be stopped by this low-pass filter, by the baseband signal of just having only label to send of low-pass filter.
Anti-mutual interference rfid system of the present invention comprises: two or more rfid interrogators, described read write line has the rearmounted low-pass filter of detection, described different read write lines institute with the difference of the carrier frequency of antenna greater than described all read write lines with the cutoff frequency of detection postposition low-pass filter.
Rfid system anti-mutual interference method of the present invention may further comprise the steps:
Two or more rfid interrogators are provided, and described read write line has the rearmounted low-pass filter of detection;
The carrier frequency of described reading and writing device antenna is set, make described different read write line with the difference of the carrier frequency of antenna greater than described all read write lines with the cutoff frequency of the rearmounted low-pass filter of detection.
When two adjacent rfid interrogators were worked simultaneously, establishing side's rfid interrogator was read write line A, and the opposing party's rfid interrogator is read write line B, then the output voltage U after detection of read write line A
DeComputing formula be:
U
de＝A+B?cos?Ωt+C?cos(ω
1-ω
2)t+D?cos?ω
1t+E?cos?ω
2t+F?cos(ω
1+Ω)t+G?cos(ω
1-Ω)t
+H?cos(ω
1+ω
2)t+I?cos?2ω
1t+J?cos(2ω
1-Ω)t+K?cos(2ω
1+Ω)t
Wherein, A is dc voltage value; B is that angular frequency is the voltage peak of Ω; ω
1Carrier voltage angular frequency for read write line A; ω
2Carrier voltage angular frequency for read write line B; C is that angular frequency is ω
2-ω
1Voltage peak; D is that angular frequency is ω
1Voltage peak; E is that angular frequency is ω
2Voltage peak; F is that angular frequency is ω
1The voltage peak of+Ω; G is that angular frequency is ω
1The voltage peak of-Ω; H is that angular frequency is ω
1+ ω
2Voltage peak; I is that angular frequency is 2 ω
1Voltage peak; J is that angular frequency is 2 ω
1The voltage peak of-Ω; K is that angular frequency is 2 ω
1The voltage peak of+Ω.
Found out U after detection by above
DeObtain a lot of frequencies of deriving, comprise the signal of various frequencies, through all kinds of radio-frequency components of the rearmounted low-pass filter elimination of detection, finally obtain U
Out
If the carrier frequency f of read write line A antenna
1Carrier frequency f with read write line B antenna
2Difference less than the cutoff frequency of low-pass filter, then obtain U at last
Out=A+Bcos Ω t+Ccos (ω
1-ω
2)
tThis f
1With f
2The frequency interferences signal Ccos (ω that derives that difference produces
1-ω
2)
tWill enter subordinate's input by low-pass filter, cause and disturb effectively, make subordinate's input can't obtain pure Bcos Ω t baseband signal.
If the carrier frequency f of read write line A antenna
1Carrier frequency f with read write line B antenna
2Difference greater than the cutoff frequency of low-pass filter, then obtain U at last
Out=A+Bcos Ω t.This f
1With f
2The frequency interferences signal Ccos (ω that derives that difference produces
1-ω
2)
tTo be low pass filtering device and stop, and can't enter subordinate's input, and make interference-nulls, subordinate's input can obtain pure Bcos Ω t baseband signal.
RFID electronic tag employing carrier frequency is the low-frequency electronic label of 125kHz-135kHz among the international standard ISO18000-2, so among the embodiment below the present invention, the carrier frequency that reading and writing device antenna provides is controlled between the 125-135kHz, to reach the best effects of read-write electronic tag.And selected read write line is for having the rearmounted low-pass filter of detection, and the cutoff frequency of its low-pass filter is greater than 7kHz.
Embodiment one: with the carrier frequency f of read write line A
1Be set to 125kHz, the carrier frequency f of read write line B
2Be set to 128kHz, so f
2-f
1=3kHz, the frequency spectrum before its envelope detection is as shown in Figure 3; Frequency spectrum after the detection behind all kinds of radio-frequency components of elimination as shown in Figure 4.F among Fig. 4
CutRepresent the cutoff frequency of read write line A and read write line B institute low-pass filter, f
mRepresent the baseband frequency of electronic tag modulation signal.
Because f
1With f
2Difference is that 3kHz is less than the cutoff frequency f of low-pass filter
Cut(7kHz), therefore the frequency interferences signal Ccos that derives that produces (2 π * 3kHz) t will enter subordinate's input by low-pass filter, finally obtain U
Out(t of 2 π * 3kHz) causes and disturbs effectively=A+Bcos Ω t+Ccos, makes subordinate's input can't obtain pure Bcos Ω t baseband signal.Will produce interference so, make read write line A and read write line B interfere with each other and correctly to read electronic tag.
Embodiment two: with the carrier frequency f of read write line A
1Be arranged to 125kHz, the carrier frequency f of read write line B
2Be arranged to 135kHz, so f
2-f
1=10kHz, before envelope detection, its frequency spectrum as shown in Figure 5, the frequency spectrum after the detection behind all kinds of radio-frequency components of elimination is as shown in Figure 6.F among Fig. 6
CutRepresent the cutoff frequency of read write line A and read write line B institute low-pass filter, f
mRepresent the tag modulates baseband frequency.
Because the difference of f1 and f2 is that 10kHz is greater than the cutoff frequency f of low-pass filter
Cut(7kHz), therefore the frequency interferences signal Ccos that derives that produces (t of 2 π * 10kHz) will be low pass filtering device to be stopped, can't enter subordinate's input, finally obtains U
Out=A+Bcos Ω t makes interference-nulls, and subordinate's input can obtain pure Bcos Ω t baseband signal, and read write line A and read write line B can normal, stable reading and writing label.
Rfid system anti-mutual interference method provided by the present invention and anti-mutual interference rfid system, when working, rfid system can produce undesired signal between the carrier frequency of each read write line and the adjacent reading and writing device antenna, differentiation arranges the carrier frequency of two adjacent reading and writing device antennas, when two adjacent reading and writing device antennas are worked simultaneously, the undesired signal frequency that the differentiation of two adjacent read write line carrier frequencies produces is greater than the rearmounted low pass filter cutoff frequency of detection in the read write line receiving circuit, namely remove undesired signal effectively, thereby demodulated the baseband signal that the RFID label of real needs sends.The invention solves a plurality of reading and writing device antennas when dense distribution is also worked at the same time, adjacent antenna is disturbed the frequency that causes deriving mutually and is produced, and causes the unstable or wrong problem of label read-write.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.
Claims (6)
1. anti-mutual interference rfid system, comprise: two or more rfid interrogators and corresponding to the electronic tag of each described rfid interrogator, it is characterized in that, described read write line has the rearmounted low-pass filter of detection, differentiation arranges the carrier frequency of two adjacent reading and writing device antennas, when two adjacent reading and writing device antennas were worked simultaneously, the undesired signal frequency that the differentiation of two adjacent read write line carrier frequencies produces was greater than the rearmounted low pass filter cutoff frequency of described detection.
2. anti-mutual interference rfid system as claimed in claim 1 is characterized in that, the carrier frequency of described electronic tag is 125kHz-135kHz, and the carrier frequency that described reading and writing device antenna provides is 125kHz-135kHz.
3. anti-mutual interference rfid system as claimed in claim 1 is characterized in that, the cutoff frequency of the rearmounted low-pass filter of described detection is greater than the fundamental frequency of electronic tag modulating baseband signal.
4. rfid system anti-mutual interference method may further comprise the steps:
Two or more rfid interrogators are provided, and described read write line has the rearmounted low-pass filter of detection;
Differentiation arranges the carrier frequency of two adjacent reading and writing device antennas, and when two adjacent reading and writing device antennas were worked simultaneously, the undesired signal frequency that the differentiation of two adjacent read write line carrier frequencies produces was greater than the rearmounted low pass filter cutoff frequency of described detection.
5. rfid system anti-mutual interference method as claimed in claim 1 is characterized in that, the carrier frequency of the electronic tag of described rfid system is 125kHz-135kHz, and the carrier frequency that described reading and writing device antenna provides is 125kHz-135kHz.
6. rfid system anti-mutual interference method as claimed in claim 1 is characterized in that, the cutoff frequency of the rearmounted low-pass filter of described detection is greater than the fundamental frequency of electronic tag modulating baseband signal.
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| CN102393536B (en) * | 2011-10-30 | 2014-10-22 | 北京无线电计量测试研究所 | Scanning method for human body security check system utilizing frequency division and space division |
| CN102393537B (en) * | 2011-10-30 | 2014-04-23 | 北京无线电计量测试研究所 | Scan method of human body security system utilizing frequency division technology |
| CN106409707B (en) * | 2015-07-28 | 2020-11-27 | 中芯国际集成电路制造(上海)有限公司 | Non-contact radio frequency chip wafer testing method and device |
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| CN201897803U (en) * | 2010-12-16 | 2011-07-13 | 上海华申泰格软件有限公司 | Difference frequency anti-intermodulation interference RFID (radio frequency identification device) system |
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| EP1630713A1 (en) * | 2004-08-24 | 2006-03-01 | Sony Deutschland GmbH | Backscatter interrogator reception method and interrogator for a modulated backscatter system |
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