CN111060900B - Distance measuring device and method based on multi-band phase information of surface acoustic wave device - Google Patents
Distance measuring device and method based on multi-band phase information of surface acoustic wave device Download PDFInfo
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- CN111060900B CN111060900B CN201811208947.6A CN201811208947A CN111060900B CN 111060900 B CN111060900 B CN 111060900B CN 201811208947 A CN201811208947 A CN 201811208947A CN 111060900 B CN111060900 B CN 111060900B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/539—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
- G01S7/523—Details of pulse systems
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Abstract
The invention discloses a distance measuring device and method based on multi-band phase information of a surface acoustic wave device, which are used for measuring the distance between a reader and a sensor probe, wherein the sensor probe comprises three surface acoustic wave devices: SAW-RFID chip A, SAW-RFID chip B and surface acoustic wave resonator; the working frequency band of the SAW-RFID chip A is 2.4GHz to 2.44GHz, and the central frequency is 2.42 GHz; the working frequency band of the SAW-RFID chip B is 2.44GHz to 2.48GHz, and the central frequency is 2.46 GHz; the working frequency range of the surface acoustic wave resonator is 420MHz to 440MHz, and the central frequency is 433 MHz; the reader has an acquisition mode for acquiring phase information of 3 different center frequency devices. The method comprises the following steps: the characteristic that the central working frequencies of three surface acoustic wave devices forming the sensor probe are not coincident is utilized, the phase information of the surface acoustic wave sensing devices of three different frequency bands is integrated, and the phase information is processed by adopting a quadratic phase difference method, so that the distance between the reader and the sensor probe is measured. The method of the invention can realize high-precision distance measurement.
Description
Technical Field
The invention relates to the technical field of Surface Acoustic Wave sensors, in particular to a distance measuring device and method based on multi-band phase information of a Surface Acoustic Wave (SAW) device.
Background
The wireless passive SAW-RFID integrates the tag and the sensor, and has the following advantages: because the surface acoustic wave sensor is made of piezoelectric materials, does not contain a semiconductor device and is a coreless device, the surface acoustic wave sensor can work only by extremely low energy, and further realizes wireless passivity. The interior of the chip works by means of sound waves, the sound waves are transmitted on the surface of the chip to have ns-level accurate time delay, the time delay has an estimated and measurable change rule, and theoretically, the time delay can be distinguished from the time delay of electromagnetic waves in space transmission. In the process of transmitting and receiving sensor echoes by the system, the distance measurement can be realized by the sensing system based on the surface acoustic wave device through separating and accurately measuring the time delay of electromagnetic wave in space propagation.
At present, the distance estimation technology research based on the surface acoustic wave device sensing system starts, the NASA research in the United states is based on an OFC coded SAW-RFID system, and the distance measurement precision can reach dozens of cm (reference document [1 ]: Gallagher M W, Malocha D C. SAW multi-sensor system with temperature and range [ C ]// Ultrasonics symposium. IEEE,2013: 2106-). Arumugam combined with antenna directional gain characteristics achieves 2-dimensional positioning based on a single SAW-RFID tag system with an accuracy of about 3.17cm (reference [2 ]: Arumugam D1.2D localization using SAW-based RFID systems: a single antenna adaptation [ J ]. International Journal of Radio Frequency Identification technologies & Applications,2007,1(4): 417-. The above related researches are all carried out by analyzing echo time domain information of the SAW tag and measuring distance by estimating the time position of the maximum point of the return energy, and phase information of the return radio frequency signal is not used.
The phase information is determined by the distance between the interdigital transducer (IDT) and the reflection grating, the SAW sound velocity, the tag distance, and the like, and the relationships are as shown in (1) and (2):
p＝360*f*2*(L/c+D/v) (1)
Δp＝360*f*2*ΔD/v (2)
wherein: d is the distance between the IDT and the reflection grating, v is the SAW sound velocity, f is the frequency, L is the distance between the tag and the reader/writer, c is the electromagnetic wave velocity, p is the phase of the reflected pulse, Δ D is the distance between the reflection gratings, and Δ p is the phase difference between the reflection gratings.
In order to eliminate the influence of the distance between the IDT and the reflection grating and the SAW sound velocity in the phase of the reflected pulse, and considering the influence of the temperature environment quantity on the distance between the IDT and the reflection grating and the SAW sound velocity, the phase difference between the reflection gratings in the formula (2) is only related to the temperature and is not related to the distance, so that the temperature can be calculated, the distance between the IDT and the reflection grating and the SAW sound velocity can be further obtained, the influence of the two is eliminated, and the part pL related to the distance in the phase of the reflected pulse is obtained, wherein the formula (3):
pL＝360*f*2*L/c (3)
because the actual measurement phase is only in the range of 0-360 degrees and is integral multiples of the actual phase difference of 360 degrees, pL0 in formula (4) is the actual measurement phase, pL is the actual phase, and the difference between the pL and the actual phase is N integral multiples of 360 degrees. This problem is a 360 ° phase ambiguity problem.
pL＝pL0+360*N (4)
When the phase information of a single frequency point is used for ranging, the value of N in (4) cannot be determined because the obtained phase is always in the range of 0-360 degrees, and therefore the distance estimation technology based on the phase measurement is to be further improved and developed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a ranging method combining the phase information of a multi-frequency point SAW device, which is used for respectively measuring the phases of an SAW-RFID and a resonator which are positioned at the same position, carrying out addition and subtraction operation on the phases, calculating the non-fuzzy phase under new frequency, solving the problem of inaccurate ranging caused by 360-degree phase ambiguity and realizing high-precision distance measurement.
The technical scheme of the invention is as follows:
a distance measuring device based on multi-band phase information of a surface acoustic wave device is used for measuring the distance between a reader and a sensor probe, wherein the sensor probe comprises three surface acoustic wave devices: SAW-RFID chip A, SAW-RFID chip B and surface acoustic wave resonator; the working frequency band of the SAW-RFID chip A is 2.4GHz to 2.44GHz, and the central frequency is 2.42 GHz; the working frequency band of the SAW-RFID chip B is 2.44GHz to 2.48GHz, and the central frequency is 2.46 GHz; the working frequency range of the surface acoustic wave resonator is 420MHz to 440MHz, and the central frequency is 433 MHz; the reader has an acquisition mode for acquiring phase information of 3 different center frequency devices.
As an improvement of the device, the phase information acquisition mode is a frequency sweep or broadband high-power excitation mode.
Based on the device, the invention also provides a distance measuring method based on the multi-band phase information of the surface acoustic wave device, and the method comprises the following steps:
the characteristic that the central working frequencies of three surface acoustic wave devices forming the sensor probe are not coincident is utilized, the phase information of the surface acoustic wave sensing devices of three different frequency bands is integrated, and the phase information is processed by adopting a quadratic phase difference method, so that the distance between the reader and the sensor probe is measured.
As an improvement of the above method, the method specifically comprises:
step 1) acquiring frequency spectrum information of the SAW-RFID chip A and the AW-RFID chip B from 2.4GHz to 2.48GHz, and recording the frequency spectrum information as an S1 sequence which is a discrete complex sequence of a + B i;
step 2) intercepting frequency information from 2.4GHz to 2.44GHz in an S1 sequence, and calculating phase information p2 of a frequency point 2.42 GHz;
step 3) intercepting frequency information from 2.44GHz to 2.48GHz in the S1 sequence, and calculating phase information p3 of frequency point 2.46GHz with corresponding wavelength of lambda3；
Step 4) obtaining the frequency spectrum information of the resonator from 420MHz to 440MHz of the surface wave resonator, and recording the frequency spectrum information as an S2 sequence which is a discrete complex sequence of a + b i;
step 5), taking the absolute value of the S2 sequence into a sequence of real number sequences, and recording the sequence as S2R; finding the maximum value in the S2R sequence, calculating the phase information of the corresponding position in the S2 sequence according to the position of the maximum value, marking the phase value as p1, and marking the corresponding wavelength as lambda2；
Step 6), enabling the delta p to be p3-p 2; the distance result L1 ═ Δ p λ is calculated using Δ p12; wherein the frequency difference between 2.42GHz and the frequency point 2.46GHz is 40MHz, and the spatial wavelength corresponding to the 40MHz electromagnetic wave is lambda1C/40MHz, c is the speed of light;
step 7) calculating 2 × L1/λ1The integer part n1, and the distance result L2 ═ based on the surface wave resonator in 420MHz to 440MHz (n1 λ ═ k1+p1*λ2)/2；
Step 8) calculating 2 × L2/λ3N2, and determines the final distance L ═ (n2 ×) λ3+p3*λ3)/2。
The invention has the beneficial effects that:
1. the distance measuring device of the surface acoustic wave device combined with the phase information selects 3 surface acoustic wave devices with different working center frequencies, wherein the three different center frequencies meet the following requirements: f1< f2< f3, calculating phases p1, p2 and p3, and adopting a phase quadratic phase difference method; the problem of inaccurate distance measurement caused by 360-degree phase ambiguity is solved, and high-precision distance measurement is realized;
2. the distance measuring method provided by the invention can solve the problem of inaccurate distance measurement caused by phase ambiguity by integrating the phase information of the surface acoustic wave devices in multiple frequency bands and jointly performing phase ambiguity resolution.
Drawings
FIG. 1 is a graph of SAW device phase versus distance for 3 different frequencies;
fig. 2 is a schematic view of the distance measuring apparatus of the present invention.
Detailed Description
The ranging method of the present invention is further described in detail by the accompanying drawings and examples.
In order to solve the problem of 360-degree phase ambiguity, a phase quadratic phase difference method is adopted. Namely: 3 SAW devices (not limited to 3, but more) with different operating center frequencies are selected, wherein three different center frequencies satisfy: f1< f2< f3, and the phases p1, p2, p3 are calculated, and the relationship between 3 phases and the distance is shown in FIG. 1. The frequency f1 is small enough that the phase p1 has no 360 phase ambiguity, but its accuracy is low, as shown by the lowermost dotted box in fig. 1, which is its fluctuation range. The other 2 phases have a 360 ° phase ambiguity. For the phase p2, limited to the fluctuation range of the phase p1, the phase p2 has no 360 ° phase ambiguity, and the only N value in the formula (4) can be obtained, the precision of which is slightly improved, as shown by the middle dotted box in fig. 1. Similar to the phase p2, the phase p3 is limited to the fluctuation range of the phase p2, the phase p3 has no 360 ° phase ambiguity, and the only N value in the formula (4) can be obtained, and the precision is the highest, and the fluctuation range is shown as the uppermost dotted box in FIG. 1. Therefore, high-precision distance measurement can be realized by using the phase quadratic difference method.
The process of the present invention requires having: the probe consists of a plurality of SAW-RFID or resonators and sensor antennas. As shown in fig. 2, the SAW-RFID or resonator contained by the probe head can be divided into at least three devices having three center operating frequencies. The devices in the probe can be, but are not limited to: the SAW-RFID chip A has a chip working frequency band of 2.4GHz to 2.44GHz and a central frequency of 2.42 GHz; the SAW-RFID chip B has a chip working frequency band of 2.44GHz to 2.48GHz and a central frequency of 2.46 GHz; and the working center frequency of the surface acoustic wave resonator is 433 MHz.
The operating frequency range of the sensor antenna described in the probe above should cover, but is not limited to, the 420MHz to 440MHz frequency range, and the operating frequency range of the antenna should also cover, but is not limited to, 2.4GHz to 2.48 GHz.
The process of the present invention requires having: a reader and a reader antenna. As shown in fig. 2, the reader should have a phase information acquisition mode that acquires 3 different center frequency devices. The phase information acquisition mode adopts a frequency sweep or broadband high-power excitation mode.
The operating frequency range of the reader antenna described in the probe above should cover, but is not limited to, the 420MHz to 440MHz frequency range, and the operating frequency range of the antenna should also cover, but is not limited to, 2.4GHz to 2.48 GHz.
The method comprises the following specific steps:
step 1) acquiring spectrum information of the SAW-RFID chip A, SAW-RFID chip B from 2.4GHz to 2.48GHz, and marking the spectrum information as S1, wherein the spectrum information is a discrete complex sequence of a + B i;
step 2) intercepting frequency information from 2.4GHz to 2.44GHz in a section S1, and calculating phase information of a frequency point 2.42GHz, and marking the phase information as p 2;
step 3) intercepting 2.44GHz to 2.48GHz frequency in section S1Rate information, phase information of a calculated frequency point 2.46GHz, which is recorded as p3, and the wavelength of 2.46GHz is lambda3；
Step 4) calculating the frequency difference between the frequency point 2.42GHz and the frequency point 2.46GHz to be 40MHz, wherein the spatial wavelength corresponding to the 40MHz electromagnetic wave is lambda1C/40MHz, where c is the speed of light in air;
step 5) obtaining the spectrum information of the resonator in the 420MHz to 440MHz surface wave resonator, and marking as S2, wherein the spectrum information is also a discrete complex sequence of a + b i; (ii) a
Step 6) taking the absolute value of the sequence of S2 to form a sequence of real numbers, and recording the sequence as S2R. Finding the maximum value in the S2R sequence, calculating the phase information of the corresponding position in the S2 sequence according to the position of the maximum value, marking the phase value as p1, and marking the corresponding wavelength as lambda2；
Step 7), calculating the delta p as p3-p 2;
step 8) calculating a distance result L1 ═ Δ p λ using Δ p1/2；
Step 9) calculating 2 × L1/λ1The integer part n1, the determination being based on the distance result L2 ═ of the resonator in the range from 420MHz to 440MHz (n1 λ ═ of λ1+p1*λ2)/2；
Step 10) calculating 2 × L2/λ3The integer part n2, and determining the final distance L ═ (n2 ×) λ3+p3*λ3)/2。
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (2)
1. A distance measurement method based on multi-band phase information of a surface acoustic wave device is realized by a distance measurement device based on the multi-band phase information of the surface acoustic wave device, the distance measurement device is used for measuring the distance between a reader and a sensor probe, and the sensor probe comprises three surface acoustic wave devices: SAW-RFID chip A, SAW-RFID chip B and surface acoustic wave resonator; the working frequency band of the SAW-RFID chip A is 2.4GHz to 2.44GHz, and the central frequency is 2.42 GHz; the working frequency band of the SAW-RFID chip B is 2.44GHz to 2.48GHz, and the central frequency is 2.46 GHz; the working frequency range of the surface acoustic wave resonator is 420MHz to 440MHz, and the central frequency is 433 MHz; the reader has an acquisition mode for acquiring phase information of 3 different center frequency devices;
the method comprises the following steps:
the characteristic that the central working frequencies of three surface acoustic wave devices forming the sensor probe are not coincident is utilized, the phase information of the surface acoustic wave sensing devices of three different frequency bands is integrated, and a quadratic phase difference method is adopted to process the phase information, so that the distance between a reader and the sensor probe is measured;
the method specifically comprises the following steps:
step 1) acquiring frequency spectrum information of a SAW-RFID chip A and a SAW-RFID chip B from 2.4GHz to 2.48GHz, and recording the frequency spectrum information as an S1 sequence which is a discrete complex sequence of a + B i;
step 2) intercepting frequency information from 2.4GHz to 2.44GHz in an S1 sequence, and calculating phase information p2 of a frequency point 2.42 GHz;
step 3) intercepting frequency information from 2.44GHz to 2.48GHz in the S1 sequence, and calculating phase information p3 of frequency point 2.46GHz with corresponding wavelength of lambda3；
Step 4) obtaining the frequency spectrum information of the resonator from 420MHz to 440MHz of the surface wave resonator, and recording the frequency spectrum information as an S2 sequence which is a discrete complex sequence of a + b i;
step 5), taking the absolute value of the S2 sequence into a sequence of real number sequences, and recording the sequence as S2R; finding the maximum value in the S2R sequence, calculating the phase information of the corresponding position in the S2 sequence according to the position of the maximum value, marking the phase value as p1, and marking the corresponding wavelength as lambda2；
Step 6), enabling the delta p to be p3-p 2; the distance result L1 ═ Δ p λ is calculated using Δ p12; wherein the frequency difference between 2.42GHz and the frequency point 2.46GHz is 40MHz, and the spatial wavelength corresponding to the 40MHz electromagnetic wave is lambda1C/40MHz, c is the speed of light;
step 7) calculating 2 × L1/λ1N1, determiningDistance results based on surface wave resonators in 420MHz to 440MHz, L2 ═ (n1 λ ═ n1+p1*λ2)/2；
Step 8) calculating 2 × L2/λ3The integer part n2, and determining the final distance L ═ (n2 ×) λ3+p3*λ3)/2。
2. The method of claim 1, wherein the phase information is obtained by frequency sweeping or broadband high power excitation.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008204234A (en) * | 2007-02-21 | 2008-09-04 | Teruya:Kk | Rfid tag built-in saw (surface acoustic wave) sensor and measurement system |
| CN101388065A (en) * | 2008-10-30 | 2009-03-18 | 水永安 | Precision determining method for surface acoustic wave radio frequency label echo time delay |
| CN101807899A (en) * | 2010-04-22 | 2010-08-18 | 水永安 | Acoustic surface wave radio frequency tag with high coding capacity |
| CN206075315U (en) * | 2016-06-26 | 2017-04-05 | 睿芯联科（北京）电子科技有限公司 | RFID tag with SAW filter |
| CN107329142A (en) * | 2017-05-08 | 2017-11-07 | 上海交通大学 | SAW RFID tag distance-finding methods based on multifrequency phase difference |
-
2018
- 2018-10-17 CN CN201811208947.6A patent/CN111060900B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008204234A (en) * | 2007-02-21 | 2008-09-04 | Teruya:Kk | Rfid tag built-in saw (surface acoustic wave) sensor and measurement system |
| CN101388065A (en) * | 2008-10-30 | 2009-03-18 | 水永安 | Precision determining method for surface acoustic wave radio frequency label echo time delay |
| CN101807899A (en) * | 2010-04-22 | 2010-08-18 | 水永安 | Acoustic surface wave radio frequency tag with high coding capacity |
| CN206075315U (en) * | 2016-06-26 | 2017-04-05 | 睿芯联科（北京）电子科技有限公司 | RFID tag with SAW filter |
| CN107329142A (en) * | 2017-05-08 | 2017-11-07 | 上海交通大学 | SAW RFID tag distance-finding methods based on multifrequency phase difference |
Non-Patent Citations (4)
| Title |
|---|
| ULTRA WIDE BAND SURFACE ACOUSTIC WAVE (SAW) RF ID TAG AND SENSOR;D. Malocha et.al.;《MILCOM 2009 - 2009 IEEE Military Communications Conference》;20100115;第1—7页 * |
| 基于DSP的SAW_RFID***的设计及应用;吴福海等;《电子技术应用》;20141231;第40卷(第1期);第97—99、103页 * |
| 基于二次相差法的多频连续波测距雷达仿真与研究;柏业鑫;《电子科技》;20120415;第25卷(第4期);第88—91页 * |
| 多频连续波雷达两种测距算法研究;曹延伟等;《电子与信息学报》;20050531;第27卷(第5期);第789—792页 * |
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