CN101089654B - RFID radio positioning method based on phase difference ranging - Google Patents
RFID radio positioning method based on phase difference ranging Download PDFInfo
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- CN101089654B CN101089654B CN2007100581620A CN200710058162A CN101089654B CN 101089654 B CN101089654 B CN 101089654B CN 2007100581620 A CN2007100581620 A CN 2007100581620A CN 200710058162 A CN200710058162 A CN 200710058162A CN 101089654 B CN101089654 B CN 101089654B
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Abstract
A RFID radio positioning method by utilizing phase-difference to measure out distance includes binding radio frequency countermark on object to be measured, setting at least two readers on positions within 1-10 meter surrounding said object, knowing position of each reader and distance between the two, emitting and receiving electromagnetic wave by each reader through its own antenna, measuring phase-difference of emission phase and reception phase to confirm distance between radio frequency countermark to each reader and calculating out position of said countermark according to geometric relation of said countermark to readers.
Description
Technical field
The invention belongs to wireless positioning field, particularly utilize RFID (RFID tag) to carry out pinpoint application.
Background technology
Wireless location technology is to measure by some parameters to the radiowave that receives, and based on this, according to specific algorithm to judge the position of testee.Measurement parameter generally comprises transmission time, amplitude, phase place and the angle of arrival etc. of test signal, and bearing accuracy then depends on the method for measurement.At present, the ripe and development of wireless communication technology has driven the appearance of emerging wireless traffic, and increasing application all needs automatic positioning service.Therefore, the kind of wireless location technology is more and more various, uses also more and more widely.Wireless location technology commonly used has:
(1) based on the GPS (GPS) of satellite communication: gps system is that 20,000 kilometers satellite is formed by 24 height, and they can provide three dimensional local information to global user with six different orbits operations.But gps system all shows sharp in indoor or its performance of buildings compact district and availability and descends, and its locating speed is also relatively slow, and carry out dispose also relatively more expensive.
(2) cellular localization technology: cellular networks such as GSM, CDMA are all supported location technology, but factors such as non line of sight (NLOS) propagation, multipath effect and multiple access interference have reduced its bearing accuracy, and relate to user's privacy concern, make its popularization be subjected to certain restriction.
(3) infrared technique: AT﹠amp; T Cambridge research department development can be used for the location of indoor object based on the active label of infrared technique, but it require object must and the infrared ray reader in alignment, and orientation distance is too near, thereby has limited it and continued development.
(4) based on the positioning system of WLAN (wireless local area network): an amount of wireless base station of installation in certain zone, the relevant information (time and intensity) of the object to be positioned that obtains according to these base stations, and the topological structure of forming in conjunction with the base station, analysis-by-synthesis, thus determine the particular location of object.This type systematic can utilize existing WLAN devices, only needs to increase corresponding information analysis server finishing the analysis of locating information, but measuring accuracy remains further to be improved.
(5) ultrasonic technology: Cricket Location Support System and Active Bat location system are two systems that success is at present used, and they have all utilized similar bat Positioning Principle, very hi-Fix.But the cost of this type systematic is too high, can't large tracts of land promote.
Except that above-mentioned technology, around little Radar Technology, WiFi and UWB Study on Technology are also underway, have only RFID but take into account the high and low targeting scheme of system price of bearing accuracy simultaneously.
REID RFID (Radio Frequency Identification) begins to rise a kind of of automatic identification technology the nineties in 20th century, promptly carries out the noncontact bidirectional data communication by wireless radio frequency mode target is discerned.The RFID technology need not direct contact, need not optical visible, need not manual intervention can finish the information input and handle, and it is convenient to operation, can work under the various rugged surroundings, can be widely used in producing, needs such as logistics, traffic, transportation, medical treatment, false proof, tracking, equipment and asset management are collected and the application of deal with data.
At present the RFID technology is in the period of rapid rising, and it is one of the most promising application technology in this century that this technology is known as by industry.Especially along with the REID theory enrich constantly and perfect, the recognition of single-chip electronic tag, multiple electronic label, wireless-readable can be write, the remote identification of passive electronic label, the REID that adapts to the high-speed mobile object is becoming a reality with product and move towards application.
The most basic rfid system is made up of three parts:
1. label (Tag, i.e. radio-frequency card):
Be made up of coupling element and chip, label contains built-in aerial, be used for and radio-frequency antenna between communicate.
On frequency of operation, be divided into low frequency, medium-high frequency, ultrahigh frequency and microwave.
From decipherment distance, be divided into close coupling close (0 ~ 1cm), distant coupling (0 ~ 1m) and long range systems (＞1m).
From the energy supply, radio-frequency (RF) tag is divided into active and passive two kinds.Passive RF label, himself does not have power supply.Therefore, all energy of using of passive RF label work must be obtained from the electromagnetic field that reader sends.In contrast, active radio-frequency (RF) tag comprises a battery, for the work of microchip provides all or part of energy.
On working method, be divided into RTF and TTF dual mode, RTF (Reader Talk First) mode is the reader-talks-first mode, has only when electronic tag receives special command just to send data.And TTF (Tag Talk First) mode is a label elder generation manner of speaking, promptly initiatively sends self ID number in case radio-frequency card enters the energy field of reader.
Be divided into a Card Reader (RO), read-write card (RW) and write-once according to packaged type and repeatedly read card (WORW).
2. reader:
Read the equipment of (in read-write card, can also write) label information.Some system also is connected with outer computer (host computer main system) by the RS232 or the RS485 interface of reader, carries out exchanges data.Used for reference the multiple advanced person's of mobile communication technology simultaneously, space division multiple access for example, frequency division multiple access and CDMA etc. have successfully realized many labels recognition technologies simultaneously, the system that solved reads the anti-collision problem of a plurality of electronic tags.
Antenna: between label and reader, transmit radiofrequency signal.
The groundwork flow process of system is: reader produces induction current by the radiofrequency signal of emitting antenna transmission certain frequency when radio-frequency card enters the emitting antenna perform region, radio-frequency card obtains energy and is activated; Radio-frequency card sends information such as self coding by the card built-in aerial; System's receiving antenna receives the carrier signal of sending from radio-frequency card, is sent to reader through the antenna adjustments device, and reader carries out the demodulation sign indicating number to the signal that receives and delivers to the backstage main system then and carry out relevant treatment; Main system is judged the legitimacy of this card according to logical operation, makes corresponding processing and control at different settings, sends the action of command signal control executing mechanism.
Above-mentioned location technology can be divided into two big classes: based on the method and the based on network method of mobile device.The former mainly be by mobile device according to reference base station information current and that communicated by letter in the past with it, calculate the position of self, its most typical application is in gps system; And the latter is the information of network based its reference base station and mobile device communication, calculates the position of mobile device in conjunction with topology of networks, realizes the location.In RFID uses, consideration for the power consumption aspect, electronic tag can not become the masters of location, so all adopt based on network method basically, both need be at the receiving trap of fixed position deploy radiofrequency signal, and gather the information of sending attached to electronic tag on people or the object by these devices, by cable network information is mail to control center then and further process.Existing three kinds of RFID targeting schemes are respectively:
1、SpotON
The SpotON system is typical case's representative of RFID targeting scheme.Similar to the ad-hoc location, the target of SpotON system is to locate the wireless device that is mutually related.This system has developed a kind of polymerization algorithm three dimensions has been positioned based on signal strength analysis.It is the hardware foundation structure that the SpotON system adopts network to distribute, and central control unit is not set in the system, with the strong and weak geometric distance that characterizes between the label of signal.But up to the present complete SpotON system does not also build up.
2.PinPoint
3D-iD pinpoint is a kind of business-like positioning system.Similar to SpotON, 3D-iD adopts wireless local area network technology to position.Pinpoint uses the radio frequency annular time to find range, and is similar to Active Bat, and this system also can come polygon measurement at known position subordinate's antenna array, and by radio frequency signal is sent to different antennae to follow the trail of the position of object.The controller that battery is housed is responsible for receiving data, and calculates radiofrequency signal, has determined the tram of object.System accuracy reaches as high as 1 to 3 meter, and adjustability is very strong, is mainly used in the indoor environments such as hospital and house.Weak point is that system's investment is bigger.
3.LANDMARC
Pass through to introduce the reference location label of stationkeeping based on the LANDMARC of radio frequency signal intensity, and, can improve bearing accuracy according to the residual error weighting algorithm between the different labels.Yet LANDMARC stablizes, is subjected to less this system at present of the influence of environmental change that the indoor positioning of two dimension can only be provided.
But these three kinds of methods promptly adopt the radio-frequency (RF) signal strength data as basis on location all based on the RSSI technology, are subjected to the influence of various interference easily, and measuring accuracy is not high, and all adopts active label, makes system have higher cost.
Summary of the invention
The present invention is directed to the above-mentioned deficiency of prior art, propose a kind of measuring accuracy height, passive RFID localization method that cost is low.
For this reason, the present invention adopts following technical scheme:
A kind of RFID wireless location method based on phase difference ranging, radio-frequency (RF) tag is tied up at target to be measured place, at least two readers are placed the position in 1 meter to 10 meters around it respectively, each reader position and distance each other separately is known, make the antenna launching electromagnetic wave of each reader by separately, the electromagnetic wave of each self-emission is received by separately reader respectively again after by the reflection of described radio-frequency (RF) tag, by measuring electromagnetic transmitter, phase that each reader launches and the phase differential between the receiving phase, determine that radio-frequency (RF) tag respectively and the distance between each reader, according to the geometric relationship between reader and the radio-frequency (RF) tag, obtain the position of radio-frequency (RF) tag again.
In the above-mentioned RFID wireless location method based on phase difference ranging, the number of reader can be two, according to according to the relation of the triangle geometry between reader and the radio-frequency (RF) tag, obtains the position of radio-frequency (RF) tag; The number of reader can be three, and three readers and radio-frequency (RF) tag constitute quadrilateral space, according to the quadrilateral space geometric relationship between three readers and the radio-frequency (RF) tag, obtain the locus of radio-frequency (RF) tag.
Can adopt full phase place fast fourier transform spectral analysis method to determine phase differential between electromagnetic transmitter, phase and the receiving phase.Adopt full phase place fast fourier transform spectral analysis method to determine that the method for the phase differential between electromagnetic transmitter, phase and the receiving phase can comprise the following steps:
(1) simultaneously with frequently electromagnetic wave of being launched and the electromagnetic wave that is received being sampled, obtains the emission sample sequence and receive sample sequence;
(2) utilize length the emission sample sequence to be carried out windowing for 2N-1 convolution window, to form N data apart from superposeing in twos again for the data of N sampling interval, at last this N data are carried out fast fourier transform, export N plural number, the amplitude of this N plural number forms N root spectral line, obtain the phase value of peak value spectral line wherein, be called the transmitter, phase value;
(3) utilize length pair to carry out windowing with the reception sample sequence of frequency simultaneously with the emission sample sequence for the convolution window of 2N-1, to form N data apart from superposeing in twos again for the data of N sampling interval, at last this N data are carried out fast fourier transform, export N plural number, the amplitude of this N plural number forms N root spectral line, obtain the phase value of peak value spectral line wherein, be called the receiving phase value;
(4) transmitter, phase value and the receiving phase value that is obtained according to step (2) and step (3) determined the phase differential between electromagnetic transmitter, phase and the receiving phase.
RFID wireless location method based on phase difference ranging of the present invention, measured receiving phase is preferably compensated according to following method: according to radio-frequency (RF) tag internal circuit configuration and parameter, ask for its transport function, utilize transport function its phase jump amount of deriving, and receiving phase is recompensed according to the phase jump amount of being derived.
Substantive distinguishing features of the present invention is: utilize passive RFID system, and adopt the novel phase measurement based on whole phase FFT to measure the phase differential that sends signal and reflected signal, thereby calculate the position of testee, reach the location purpose.
What the present invention adopted is that the phase type range measurement principle positions, and the scheme of dividing based on energy level with existing document is different.Existing energy level scheme need adopt and be provided with a plurality ofly with reference to Tag (label), and the locating effect that finally obtains only is which piece zone what can judge the target place be.This programme need not to adopt a plurality of with reference to Tag, and that adopt is passive Tag, adopts localization method of the present invention, and energy consumption is low and cost is lower, and the present invention adopts the distance-finding method based on phase differential to position calculating, and bearing accuracy is much higher compared to existing technology.
Description of drawings
Fig. 1 RFID wireless location of the present invention schematic diagram;
The waveform location drawing of Fig. 2 transmitter, phase and receiving phase;
Fig. 3 whole phase FFT analysis of spectrum process flow diagram (N=4);
The diagram of Fig. 4 location Calculation.
Embodiment
RFID wireless location principle of the present invention as shown in Figure 1.
Suppose that Tag is tied up on target object to be detected, for determining radio-frequency (RF) tag (Tag) position, with two readers (Reader1 and reader2 card reader) R
1, R
2Place its location about respectively, and R
1, R
2Apart from S
0For known,, need measure Reader1 and reader2 card reader R for determining the accurate position of target Tag
1, R
2With Tag apart from S
1, S
2
In rfid system, if make the signal transmission frequency of reader be in hyper band (
), then at this moment the coupling scheme between label and the reader are the electromagnetic backscatter coupling scheme, be to transmit each other with form of electromagnetic wave between Reader and the Tag, electromagnetic wave is with light velocity propagation, as long as thereby can record electromagnetic wave and travel to and fro between both transmission times, just can determine its distance exactly.
For measuring its distance (R as shown in Figure 1
1And between Tag apart from S
1), need measure the transmitter, phase of hyper band transmitted wave
, receiving phase
, calculate electromagnetic wave then and travel to and fro between between the two phase differential
, this just relates to following problem:
(1) can label Tag reflect the problem of its incident electromagnetic wave fully, and the phase jump problem.
(2) how accurately to measure its transmitter, phase
, receiving phase
Problem.
(3) know reader and label card the distance after the location Calculation problem.
(4) discern different Reader and the anti-collision problem of Tag.
With regard to above-mentioned several aspects problem technical scheme of the present invention and principle are elaborated below.
1. label Tag is to the reflection problems of incident electromagnetic wave
The interaction of reader and label is: when work, radio-frequency (RF) tag is positioned at the far-field region of reader antenna radiation field, and (corresponding radio-frequency recognition system reading distance is generally greater than 1 meter, maximum can reach about 10 meters), the reader antenna radiation field provides radio-frequency (RF) energy for passive label, and passive label is waken up.Reader antenna generally is directional antenna, and only the radio-frequency (RF) tag in reader antenna directional beam scope can be by read/write.
After label is activated, according to 0,1 recognition data (being low-rate bit stream) in the card, impedance with certain frequency (its bit rate is about about tens kHz) control label emitting antenna, make it be in " coupling " or " mismatch " state (as making the corresponding matching status of 1 bit, the corresponding mismatch Conditions of 0 bit).According to transmission line theory, when being in matching status, electromagnetic wave energy is absorbed by label, and when being in mismatch Conditions, electromagnetic wave energy is reflected back.
Obviously, for realizing phase ranging, label antenna need be worked in mismatch Conditions.This is not difficult to realize that this is because all be made as 0 as long as will block the last partial bit data of interior ID bit information, then antenna mismatch.In addition, consider that because the speed of bit stream is tens kHz, its cycle is much bigger more than transmitting of reader, with tag bits rate R from degree of having plenty of time
b=30kHz, reader transmission frequency fr=900MHz calculates, and then in a bit period, electromagnetic wave can reach 30000 times by the round number of times between reader and label, in a wide like this time period, there is grace time to carry out the data computation of transmitter, phase and receiving phase.
In addition, enter Tag at electromagnetic wave, reflect from Tag, the degree whether transition and phase jump can take place in this stage waveform phase also is the problem that needs consideration.Confirmablely be, this phase jump size is fixed, and is that internal circuit parameter by Tag is determined fully, thereby can be after accurately obtaining Tag internal circuit configuration and parameter, by asking for its transport function, shift onto to such an extent that its phase jump amount realizes.When actual phase is calculated, this phase jump amount need be recompensed.
2. how to measure transmitter, phase
, receiving phase
Problem.
2.1 phase differential and range finding relation, and the conversion of phase difference measurement
The waveform location drawing of transmitter, phase and receiving phase as shown in Figure 2.The initial phase of supposing transmitted wave is in the A as Fig. 2
1The place, and the phase place of received signal is in the B of Fig. 2
1The place, then this phase differential of 2 is transmission frequency f
rTo the integration of time and produce, promptly
Make that the light velocity is c, it is Δ t that electromagnetic wave comes and goes the used time, thus reader and label card apart from S
1For: (2)
Fig. 2 has demonstrated and A
1Put the A of N sampling interval (the supposing N=12 among Fig. 2) of being separated by
2Sampling point, and and B
1Put the B of N sampling interval (the supposing N=12 among Fig. 2) of being separated by
2Sampling point, because the waveform equal interval sampling, and the frequency of waveform is constant, and then following formula is set up:
Formula (3) illustrates, the problems of measurement of the phase place that transmits and phase of received signal difference can transfer to and the be separated by phase difference measurement problem of same sampling interval number of transmit phase point and phase of received signal point.
2.2 concrete phase measurement method
The present invention adopts whole phase FFT (fast fourier transform) method to carry out phase measurement:
Fig. 3 is whole phase FFT (all-phase FFT, abbreviation apFFT) signal processing flow of analysis of spectrum, method is as follows: with length is that the individual convolution window of 2N-1 is carried out windowing to sample sequence, to form N data apart from superposeing in twos again, at last this N data be carried out the result that FFT promptly gets apFFT for the data of N sampling interval.Obviously, FFT is output as N plural number, thereby comprises abundant phase information, and the amplitude of this N plural number just forms N root spectral line, and wherein the phase value on the peak value spectral line is the notional phase value of x in Fig. 3 input sample (0).Can find out that it is simpler that apFFT surveys the phase method, need not any additional phase correction measure, calculated amount is little, and experimental results show that its phase-measurement accuracy is very high.Thereby,, can measure its phase value exactly by apFFT as long as obtain to be total to 2N-1 data before and after certain sampling point.Can find in addition, only need 1 road sample sequence is carried out whole phase FFT, measured phase place promptly is the absolute phase of input sample x (0), that is to say, do not need one tunnel same frequency and the known waveform of phase place to compare and get, thereby adopt whole phase FFT to survey the generation circuit that the phase method can be saved the reference waveform of reader.
Can find out in conjunction with Fig. 2 and Fig. 3, if directly survey A with the apFFT method
1The phase place at place is impossible, because A
1Be the starting point of transmitted waveform, sampling point data before obtain less than, but from A
1The A of N the data in interval
2Phase place but can record by apFFT at an easy rate, in like manner, receive sampling point B
1Phase place also can be similarly by asking for B
2Phase place and get.Thereby moment of sampling point to be required during the apFFT phase differential be very loose.
Similarly, treat that waveform enters stable state after, A
2And B
2Phase differential also can stagger time interval number backward identical and get.But be noted that, must guarantee A
2And B
2Sampling be simultaneous.This not so difficult accomplishing because the sampling of transmitted waveform does not take place on different devices with the sampling process that receives waveform, but is carried out in the A/D of same reader device.
3 location Calculation and precision analysis thereof
(1) location Calculation
With same phase ranging method can measure between Reader2 and the Tag apart from S
2, and between Reader1 and the Reader2 apart from S
0Be known, and the position of three sides of a triangle is all known, can obtain the position of label Tag by finding the solution leg-of-mutton geometric relationship, sets up rectangular coordinate system as shown in Figure 4:
Knowing S
0, S
1, S
2Size after, obviously have:
So, label Tag coordinate (x
0, y
0) can be defined as:
x
0＝s
1·cosθ
2，y
0＝s
1·sinθ
2
In like manner, if will determine the three-dimensional position of Tag, then also need calculate a z
0At this moment coordinate only need increase by a reader Reader3 again, and the distance of measuring Reader3 and Tag with the whole phase FFT method gets final product.In addition, one of listed examples is to adopt two readers that the planimetric position of Tag is carried out here, and one is to adopt three readers that the three-dimensional position of Tag is positioned.In the practical application,, can also around Tag, place several readers more, utilize more information that measurement result is compensated in order to obtain more accurate data message.
(2) precision analysis
Obviously, the bearing accuracy of Fig. 4 depend on asked for apart from S
1With S
2Precision, and the S in this programme
1With S
2Survey by whole phase FFT again and obtain mutually.Thereby if ignore other factor affecting (as the phase jump of Tag to modulating wave, the moment deviation that reader is sampled simultaneously to transmission waveform and reception waveform etc.), the phase-measurement accuracy of whole phase FFT has determined the phase-measurement accuracy of whole positioning system.
And having the reason of very high phase-measurement accuracy, whole phase FFT (fast fourier transform) is:
(a) whole phase FFT have very good inhibition spectrum leaking performance, and spectrum leakage is to cause FFT to survey the main cause that occurs error mutually as a kind of novel spectral analysis method.Compare with traditional FFT, in the points N one of FFT regularly, but mathematical justification, the decibels of whole phase FFT spectrum leakage (take the logarithm computing and get) hangs down 1 times than traditional FFT.
(b) noise is the forming after treatment the process of N data from 2N-1 data of input of Fig. 3 whole phase FFT, and its noise variance can reduce about 1/3, thereby has suppressed the influence of noise to the survey phase, has improved phase-measurement accuracy.
Consider from the angle of parameter estimation that (c) provable, when signal to noise ratio (S/N ratio) during greater than 10dB, repeatedly the survey phase variance of whole phase FFT almost reaches theoretical limit (carat Mei-Luo limit), when signal to noise ratio (S/N ratio) during less than 10dB, the survey phase variance of whole phase FFT is approached a carat Mei-Luo limit.
Reader that 4 identifications are different and the anti-collision problem of Tag
Obviously,, also there is a sequence problem, promptly interacts between shilling Reader1 and the Tag, to record S if only there are two readers that a Tag is carried out electromagnetic wave when coming and going phase measurement
1Make again to interact between Reader2 and the Tag, to record S
2Just can be at an easy rate to carrying out the Tag location.
Consider to exist a plurality of Reader to carry out indoor positioning situation that just must identify different Reader, this patent adopts the method head it off of " frequency division multiplexing " to Tag.Promptly on the signal of card reader output, add a modulation signal, simultaneously, distribute the modulation signal of different frequency for different card reader.Thus, utilize the method for software radio to measure the wave frequency of reception, i.e. the numbering of distinguishable Reader.Each Reader receives only the reflection of electromagnetic wave signal of returning of oneself emission, and the signal that leaches other Reader is (because the modulation band of each Reader is determined, therefore can design the fixing digital filter of passband realizes), reach the purpose of anticollision.
And also exist a plurality of Tag to respond the problem of same Reader simultaneously simultaneously, at this moment the close echo that Reader received just may be the complex superposition of a plurality of Tag close echos.Can utilize existing anti-collision algorithms to be about to it and make a distinction, make it only the phase of echo of a Tag to be measured at synchronization.After determining the Tag position, further decode the ID identification code of Tag inside, thereby both realized the location positioning of Tag, realize the identification of Tag again.
Claims (5)
1. RFID wireless location method based on phase difference ranging, radio-frequency (RF) tag is tied up at target to be measured place, at least two readers are placed the position in 1 meter to 10 meters around it respectively, each reader position and distance each other separately is known, make the antenna launching electromagnetic wave of each reader by separately, the electromagnetic wave of each self-emission is received by separately reader respectively again after by the reflection of described radio-frequency (RF) tag, adopt electromagnetic transmitter, phase that full phase place fast fourier transform spectral analysis method determines that each reader is launched and the phase differential between the receiving phase, determine that radio-frequency (RF) tag respectively and the distance between each reader, according to the geometric relationship between reader and the radio-frequency (RF) tag, obtain the position of radio-frequency (RF) tag again.
2. the RFID wireless location method based on phase difference ranging according to claim 1 is characterized in that the number of described reader is two, according to the relation of the triangle geometry between reader and the radio-frequency (RF) tag, obtains the position of radio-frequency (RF) tag.
3. the RFID wireless location method based on phase difference ranging according to claim 1, it is characterized in that, the number of described reader is three, three readers and radio-frequency (RF) tag constitute quadrilateral space, according to the quadrilateral space geometric relationship between three readers and the radio-frequency (RF) tag, obtain the locus of described radio-frequency (RF) tag.
4. the RFID wireless location method based on phase difference ranging according to claim 1, it is characterized in that, adopt full phase place fast fourier transform spectral analysis method to determine that the method for the phase differential between electromagnetic transmitter, phase and the receiving phase comprises the following steps:
(1) simultaneously with frequently electromagnetic wave of being launched and the electromagnetic wave that is received being sampled, obtains the emission sample sequence and receive sample sequence;
(2) utilize length the emission sample sequence to be carried out windowing for 2N-1 convolution window, to form N data apart from superposeing in twos again for the data of N sampling interval, at last this N data are carried out fast fourier transform, export N plural number, the amplitude of this N plural number forms N root spectral line, obtain the phase value of peak value spectral line wherein, be called the transmitter, phase value;
(3) utilize length pair to carry out windowing with the reception sample sequence of frequency simultaneously with the emission sample sequence for the convolution window of 2N-1, to form N data apart from superposeing in twos again for the data of N sampling interval, at last this N data are carried out fast fourier transform, export N plural number, the amplitude of this N plural number forms N root spectral line, obtain the phase value of peak value spectral line wherein, be called the receiving phase value;
(4) transmitter, phase value and the receiving phase value that is obtained according to step (2) and step (3) determined the phase differential between electromagnetic transmitter, phase and the receiving phase.
5. according to any described RFID wireless location method of claim 1 to 3 based on phase difference ranging, it is characterized in that, measured receiving phase is compensated according to following method: according to radio-frequency (RF) tag internal circuit configuration and parameter, ask for its transport function, utilize transport function its phase jump amount of deriving, and receiving phase is recompensed according to the phase jump amount of being derived.
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