CN102752075B - Radio frequency identifiable communication link rate adjusting method - Google Patents
Radio frequency identifiable communication link rate adjusting method Download PDFInfo
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- CN102752075B CN102752075B CN201210157179.2A CN201210157179A CN102752075B CN 102752075 B CN102752075 B CN 102752075B CN 201210157179 A CN201210157179 A CN 201210157179A CN 102752075 B CN102752075 B CN 102752075B
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Abstract
The invention relates to a radio frequency identifiable communication link rate adjusting method. A radio frequency device comprises a reader-writer, an antenna and a label, the reader-writer sends radio frequency signals to activate the label and sends a command to the label, the label returns the radio frequency signals carried with information to the reader-writer at a certain rate based on the command so as to achieve identification, through the adjustment of the modulation rates of the returning of the signals, the frequency of the returned signals can avoid a noise source, the signal to noise ratio is increased, the modulation rates of the returned signals are prime numbers mutually, and the modulation frequencies of the returned signals are N discrete points. According to the radio frequency identifiable communication link rate adjusting method, a low on-chip oscillator frequency can be used, so that the power consumption of a label chip can be decreased. The frequencies of the returned signals are adjusted, and the returned signals can avoid plenty of interference signals, so that the identification performance of a radio frequency identifying device is improved.
Description
Technical field
The present invention relates to REID, be specifically related to a kind of method of adjustment of communication link speed of radio frequency identification.
Background technology
Radio-frequency (RF) identification (RFID) technology is a kind of contactless automatic identification technology.In radio-frequency recognition system, read write line sends radiofrequency signal and activates radio-frequency (RF) tag, concurrent order of losing one's life carries out various operation to the label being in state of activation, and the order that label sends according to read write line returns the radiofrequency signal of carrying information to read write line with certain speed, thus reach the object of identification.
In passive ultrahigh frequency radio frequency identification, label self not charged, needing read write line transmitter to send powerful permanent envelope carrier wave is that tag circuit is powered.And label adopts the mode of backscattered modulation usually to the reverse signal link of read write line, the signal energy turning back to read write line is very faint.In prior art, there is following problem in radio-frequency recognition system usually:
One, in practical engineering application, reverse link is often subject to the interference of various noise source, when noise source frequency and reverse link rate frequency close to time, then can reduce reverse link signal to noise ratio, even reverse link signal be flooded.In actual environment, there is the noise source of a type, its feature is: (1) it fix relative to spectrum of carrier position, cannot be avoided by carrier jumping frequency.(2) it includes abundant harmonic components, and noise energy concentrates on the integer harmonics of some first-harmonics.Present within the scope of broad spectrum the spectrum structure with arrowband pectination feature.(3) its spectrum component is positioned at the frequency range of passive ultra-high frequency radio-frequency (RF) identification backscattered modulation.(4) such as: there is an interference source, its main noise concentration of energy is at Fc ± 80KHz, Fc ± 160KHz, Fc ± 240KHz ... (Fc is system carrier frequency) is if the He Ne laser of passive ultrahigh frequency radio frequency identification backscattered modulation is the integral multiple of 80KHz, then the normal back-modulation signal of above noise source meeting severe jamming, causes whole recognition distance to shorten.
Two, in order to evade possible in-band noise interference, a kind of effective method can control reverse link modulation rate by continuous print by forward communications parameter, thus when there is interference, can avoid interference flexibly.Such as: in forward communications, use the signal that a section special, and calibrate back-modulation speed with the length of this signal, above object can be reached.In forward communications, one section of distinctive signal can be added, and the reference frequency BLF=M/Tcal using the length Tcal of this signal as back-modulation speed, flexibility simultaneously in order to realize, arrange another coefficient M, the desirable some simple numerical value of M, as 1/2,3/8 etc., namely the modulation rate of label inverse signal is uniquely determined by M and Tcal.
Due to the continuous quantity that parameter Tcal is in certain limit, in order to ensure to calculate the accuracy returning rate calculations, usual label to be selected with under type to realize this reverse rate Adjusted Option: on the sheet of (1) label chip, oscillator operation is in a reference frequency f0 far above back-modulation velocity maximum, and with this frequency, Tcal is counted in forward communications, and determine the count value needed for the generation of back-modulation speed according to the value counted and another coefficient M, with this count value, frequency division is carried out to f0, thus be met the back-modulation speed BLF of error requirements.Because high-frequency clock is comparatively large for the power consumption impact of chip, therefore, although the program effectively can avoid the interference of noise, the disadvantage that when but causing circuit realiration, power consumption is larger.
Summary of the invention
For the deficiencies in the prior art, the invention provides a kind of method of adjustment of communication link speed of radio frequency identification, make label optional lower frequency values when selecting oscillator reference frequency, and evade the interference that may exist.
The method of adjustment of the communication link speed of a kind of radio frequency identification provided by the invention, radio-frequency unit comprises read write line, antenna and label; Read write line sends radiofrequency signal and activates label, and concurrent order of losing one's life is to the label being in state of activation, and the order that label sends according to read write line returns the radiofrequency signal of carrying information to read write line with certain speed, thus reach the object of identification; Its improvements are, the modulation rate returned by adjustment signal, makes the modulating frequency of inverse signal avoid noise source, improves signal to noise ratio; Prime number each other between the modulation rate of described inverse signal; The modulating frequency of described inverse signal is N number of discrete point.
Wherein, described method of adjustment comprises the steps:
(1), after described read write line activates label, send order to label, what comprise needs returns modulation rate field, and comprising a length in described modulation rate field is log
2n bit return modulation rate setup parameter Mk;
(2) label sends the reference frequency of modulation rate alignment oscillator when ordering according to described read write line;
(3) oscillator of label selects the frequency values of a Frequency point as the benchmark returning modulation rate from described N number of discrete point in frequency; The coefficient M of its frequency values of Frequency point corresponding to described modulation rate setup parameter Mk and the product of the reference frequency of calibrating of selection;
(4) label according to described in return time modulation rate modulation reverse signal, and be back to read write line by antenna.
Wherein, the frequency values of described N number of discrete Frequency point is uniformly distributed within the specific limits, and its frequency values prime number each other.
Wherein, when signal returns, meet the interference signal of spectrum structure, described read write line detects communication quality and obtains different returning modulation rate with the signal that avoids interference by the modulation rate parameter that returns changed in order.
Wherein, described certain limit is [60K, 640K].
Compared with the prior art, beneficial effect of the present invention is:
The present invention, when practical engineering application exists noise, by adjusting the modulation rate returned flexibly, improves the signal to noise ratio of reverse link.
The present invention can use oscillator frequency on lower sheet, thus reduces the power consumption of label chip.
The reference frequency of the modulation rate alignment oscillator that the present invention is sent by read write line, without the need to calibrating by two parameters in prior art simultaneously, improves calibration efficiency.
The present invention, by adjustment inverse signal modulating frequency, avoids a lot of interference signal, thus improves the recognition performance of rfid device.
The present invention is by selecting to return (64KHz ~ 640KHz) in speed range, distribution uniform at conventional, and the one group of discrete point in frequency having a minimum common divisor is as optionally returning speed.Be evenly distributed, have minimum common divisor and ensure that the interference the most effectively can avoided the uncertain noise with comb frequency spectrum structure and produce in limited discrete point in frequency.
The present invention selects discrete Frequency point, instead of continuously adjustable frequency is as returning rate reference, not only avoid use upper frequency sheet on oscillator, and when reality uses, choice for use of being more convenient for.
Accompanying drawing explanation
Fig. 1 is the schematic diagram of its device of REID provided by the invention.
Fig. 2 is the circuit structure diagram of the label of rfid device provided by the invention.
Fig. 3 is the structural representation of clock oscillator provided by the invention.
Fig. 4 is adjustment provided by the invention modulating frequency schematic diagram when returning, and in figure, f2 is the frequency of inverse signal, and f1 is noise.
Embodiment
Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.
As shown in Figure 1, be the RFID technique of prior art, comprise read write line, antenna and label; Read write line is by antenna to transmitting interrogation signals, and described label produces corresponding signal according to the radiofrequency signal of launching, and is back to the transceiver module of read write line by antenna.
The present embodiment, on above-mentioned basis, adjusts its speed of signal being back to read write line from label, makes the modulating frequency of inverse signal avoid noise source, improves signal to noise ratio; Prime number each other between the modulation rate of described inverse signal; The modulating frequency of described inverse signal is N number of discrete point.
Method of adjustment comprises the steps:
(1), after described read write line activates label, send order to label, comprise the modulation rate field returned of needs, comprising a length in described modulation rate field is log
2n bit return modulation rate setup parameter Mk, the different coding of Mk is corresponding corresponding modulation rate setting coefficient M;
(2) label sends the reference frequency of modulation rate alignment oscillator when ordering according to described read write line;
(3) oscillator of label selects the frequency values of a Frequency point as the benchmark returning modulation rate from described N number of discrete point in frequency; The coefficient M of its frequency values of Frequency point corresponding to described modulation rate setup parameter Mk and the product of the reference frequency of calibrating of selection;
(4) label according to described in return time modulation rate modulation direction signal, and be back to read write line by antenna.
Wherein, the frequency values of N number of discrete Frequency point is uniformly distributed within the specific limits, is [60K, 640K].And its frequency values prime number each other.
Practical communication process is, after read write line activates label, send the order comprising and select echo frequency field, label is according to this field, select a traffic rate as reverse link in the discrete point in frequency determined according to above method, and with the corresponding information of this speed transmission to read write line, if there is the interference signal of specific frequency spectrum structure in environment for use, read write line is by detection communication quality initiatively or evaded the spectrum structure interference determined in the communications by the different reverse link rate of order trial use.
In above-described embodiment, oscillator produces N number of discrete frequency, and it realizes by circuit, frequency divider and frequency multiplier.The present embodiment illustrates for the frequency that circuit realiration is discrete.
Inside tags circuit as shown in Figure 2, comprises energy recovering unit, modulating unit, demodulating unit, reset signal generation unit, protocol control circuitry, memory, clock oscillator, clock frequency calibration control unit and encrypting module; Described energy recovering unit receives the radiofrequency signal of described antenna, for described label provides power supply (can be equivalent to a DC power supply); The square wave that its digital signal is converted to simulation by the radiofrequency signal received by described demodulating unit passes to described protocol control circuitry; Signal is passed to described clock frequency calibration control unit by described protocol control circuitry successively and described clock oscillator produces discrete Frequency point, is given the transceiver module of described read write line by described modulating unit and described antenna transmission; The unique parameters that the selection of inverse signal modulating frequency is required by read write line sets; Described memory is for storing the data receiving and send; Described reset signal generation unit resets lower than during normal voltage at the voltage that described energy recovering unit provides.The protocol control circuitry of the present embodiment is made up of state machine and combinational logic circuit, completes following functions: (1) decodes: the serial digital signal according to receiving demodulates corresponding control command.(2) tag state controls: do the protocol integrated test system label transfer deferred to next state according to current label state and the control command that receives according to system.(3) access data: according to the data in the current state access storage unit of the order received.(4) return data generates: the content controlling return data according to the order received.(5) other: the work controlling enciphering/deciphering module, controls the work of clock frequency calibration circuit.
The frequency of the inverse signal of the present embodiment is the discrete point in frequency with decimal precision.Multiple proportion between its discrete point in frequency is determined by the multiple proportion between the parameter of inside tags circuit.Particularly set according to the current source of described clock oscillator by the multiple proportion between the discrete point in frequency that returns modulation rate setting coefficient M setting.The frequency values of discrete point in frequency is described reference frequency and returns the product that modulation rate sets coefficient M.
Clock oscillator as shown in Figure 3, comprises electric capacity, return difference comparator and the current source of at least one.Electric capacity one end is connected with the reverse input end of return difference comparator, other end ground connection.The input in the same way of return difference comparator connects an extra reference voltage source (its voltage exported as the reference voltage), and return difference comparator controls reset circuit for reset capacitance both end voltage simultaneously.The reference frequency of clock oscillator is determined by its device parameters.Each current source sets one and returns modulation rate; Described current source is made up of transistor; The grid of the transistor of at least one is connected with described protocol control circuitry, and its drain electrode is connected with the reverse input end of the comparator of described clock oscillator according to returning modulation rate setup parameter Mk accordingly.The present embodiment establishes transistor to have 8, can set 8 and return modulation rate.The grid of 8 transistors links together, and it becomes common port, is connected with described protocol control circuitry, and the source electrode of 8 transistors is connected to label general supply positive pole jointly.The drain electrode of 8 transistors exports different electric currents and is connected to electric capacity one end by MUX.According to the order request that read write line sends, one that meets in corresponding selection 8 transistors is connected with the reverse input end of the return difference comparator of clock oscillator.The output current relation between them is determined by physical size between the transistor that 8 current sources are corresponding.The 64KHz that the present embodiment requires for reader, as requested, is chosen suitable transistor, is connected by MUX with return difference comparator, and modulating unit launches the transceiver module of inverse signal to read write line that modulation rate is 64KHz.If there is interference signal in this back-modulation speed and integer harmonics frequency thereof, then can select another back-modulation speed, such as, 320 × 3/7KHz, in concrete enforcement, return (64KHz ~ 640KHz) in speed range at conventional, have selected distribution uniform, and the class frequency having a minimum common divisor preferred version of discrete frequency point selection in this enforcement the most.Modulating frequency as returned can select 320KHz × M, and wherein M gets 1/5, and 3/7,7/11,1,2/5,6/7,14/11,2.
Described clock frequency calibration control unit comprises frequency feedback calibration circuit, in the process of clock oscillator during fabrication, certain error is there is between the reference frequency determined by the actual parameter of device and the reference frequency of setting, so, while label receives radiofrequency signal, by receiving the specific modulation speed of read write line signal transmitted, the relatively relation of Received signal strength and clock oscillator output signal, the frequency of progressive fine setting oscillator, to make the synchronous and read write line of the reference frequency of the output of oscillator to the traffic rate of label.
As shown in Figure 4, this through the present invention adjustment after return time modulating frequency, as can be seen from figure we, the frequency values after adjustment avoids the interference of interference signal.
Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.
Claims (2)
1. a method of adjustment for the communication link speed of radio frequency identification, radio-frequency unit comprises read write line, antenna and label; Read write line sends radiofrequency signal and activates label, and concurrent order of losing one's life is to the label being in state of activation, and the order that label sends according to read write line returns the radiofrequency signal of carrying information to read write line with certain speed, thus reach the object of identification; It is characterized in that, the modulation rate returned by adjustment signal, makes the modulating frequency of inverse signal avoid noise source, improves signal to noise ratio;
Prime number each other between the modulation rate of described inverse signal;
The modulating frequency of described inverse signal is N number of discrete point;
The frequency values of described N number of discrete Frequency point is uniformly distributed within the specific limits, and its frequency values prime number each other;
Described certain limit is [60K, 640K];
Described method of adjustment comprises the steps:
(1), after described read write line activates label, send order to label, what comprise needs returns modulation rate field, and comprising a length in described modulation rate field is log
2n bit return modulation rate setup parameter Mk;
(2) label sends the reference frequency of modulation rate alignment oscillator when ordering according to described read write line;
(3) oscillator of label selects the frequency values of a Frequency point as the benchmark returning modulation rate from described N number of discrete point in frequency; The coefficient M of its frequency values of Frequency point corresponding to described modulation rate setup parameter Mk and the product of the reference frequency of calibrating of selection;
(4) label according to described in return time modulation rate modulation reverse signal, and be back to read write line by antenna.
2. method of adjustment as claimed in claim 1, it is characterized in that, when signal returns, meet the interference signal of spectrum structure, described read write line detects communication quality and obtains different returning modulation rate with the signal that avoids interference by the modulation rate parameter that returns changed in order.
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| CN103218653B (en) * | 2013-04-23 | 2016-03-30 | 复旦大学 | For label harmonic wave acquisition methods and the harmonic RF identification label of harmonic RF identification |
| CN113543350B (en) * | 2021-03-30 | 2022-09-13 | 太原理工大学 | Rate self-adaption method based on frequency mapping |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1701342A (en) * | 2003-08-29 | 2005-11-23 | 赛宝技术公司 | RFID system with selectable backscatter parameters |
| CN101207407A (en) * | 2006-12-21 | 2008-06-25 | 东芝泰格有限公司 | Interrogator |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1701342A (en) * | 2003-08-29 | 2005-11-23 | 赛宝技术公司 | RFID system with selectable backscatter parameters |
| CN101207407A (en) * | 2006-12-21 | 2008-06-25 | 东芝泰格有限公司 | Interrogator |
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