CN113251961B - Microwave displacement sensor based on coupling microstrip line - Google Patents
Microwave displacement sensor based on coupling microstrip line Download PDFInfo
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- CN113251961B CN113251961B CN202110455636.5A CN202110455636A CN113251961B CN 113251961 B CN113251961 B CN 113251961B CN 202110455636 A CN202110455636 A CN 202110455636A CN 113251961 B CN113251961 B CN 113251961B
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- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
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Abstract
The invention discloses a microwave displacement sensor based on a coupling microstrip line, which comprises a stator and a rotor; the stator comprises three layers: the top layer consists of four rectangular coupling microstrip lines; the middle layer is a dielectric plate; the bottom layer is a metal sheet and is arranged on the lower surface of the middle layer; the four coupled microstrip lines are divided into two groups, the two groups of coupled microstrip lines are arranged on the upper surface of the middle layer in parallel and symmetrically, a gap exists between two microstrip lines in the same group of coupled microstrip lines, and a space is kept between the two groups of coupled microstrip lines; the active cell can move along the length direction of the stator, and comprises two layers: the upper layer is a dielectric plate, the lower layer is a square metal patch, the lower layer is arranged on the lower surface of the upper layer, and two ends of the square metal patch of the lower layer are respectively in electric contact with two coupling microstrip lines of which two groups are positioned at the inner side. By adopting the technical scheme of the invention, the result of measuring the displacement of the object to be measured from the original position is more accurate.
Description
Technical Field
The invention belongs to the technical field of microwave sensor manufacturing, and particularly relates to a microwave displacement sensor for realizing high sensitivity and high dynamic range.
Background
The sensor manufactured by applying the microwave technology has high sensitivity, stable performance in different environments and low manufacturing cost and measurement cost, and plays an increasingly important role in the fields of medical treatment, biomedicine, industry and the like. Many microwave sensors with similar functions of material identification, humidity sensing, material defect detection and the like have been successfully developed, and the sensors have different forms and different characteristics.
In the field of aerospace vehicles, for example, the measurement of an object is important in its task, and in recent years, many types of displacement and angle sensors based on various principles and having various shapes have appeared. The general strategy of the microwave displacement sensor is that an object to be measured is connected with a movable structure of a part of the sensor, or a resonant structure, or a part of a microwave circuit, and the movement of the object to be measured moves together with the movable part of the sensor, and the movement of the part changes the properties of the microwave circuit or a part of a resonant unit therein or causes different coupling effects, so that the information of the movement amount of the object to be measured can be extracted from an output signal obtained from a sensor port.
For a microwave angle/displacement sensor, there are several important indicators: the first is sensitivity, and especially higher sensitivity is needed for measuring a tiny displacement, and the higher sensitivity generally means a more accurate measurement result; secondly, the dynamic range is different for different applications, and meanwhile, a larger dynamic range and higher sensitivity are usually incompatible, that is, a choice needs to be made between the dynamic range and the sensitivity, and the larger dynamic range is usually at the cost of the sensitivity; thirdly, the size of the design is relative to the size of the dynamic range, and some designs use a large circuit area when measuring the displacement within a certain dynamic range, so that the size of the whole device is relatively overlarge; fourth is the operating frequency of the sensor, with lower operating frequencies being better from an application standpoint. Although various types of sensors, principles of which have been developed, existing sensors typically have either too small a dynamic range or insufficient sensitivity. For the sensors, the sensitivity of the sensors is very important, and one sensor has higher sensitivity, which indicates that the sensor can distinguish small changes of the position of an object to be detected more accurately and precisely. Another type of microwave sensor is limited in its application range because it is difficult to expand its scale due to the nature of its operating principle. Therefore, it is necessary to develop a microwave displacement sensor with high dynamic range, high sensitivity and expandability to solve the above problems in the prior art.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the high-dynamic-range extensible microwave displacement sensor which can measure the offset of an object to be measured on a larger scale, and the difference value of double resonance points is used for detecting the displacement so as to obtain higher sensitivity, so that higher accuracy can be achieved when the displacement of the object is measured.
In order to achieve the purpose, the invention is realized according to the following technical scheme:
the microwave displacement sensor based on the coupling microstrip line comprises a stator and a rotor; the stator comprises three layers: the top layer consists of four rectangular coupling microstrip lines; the middle layer is a dielectric plate; the bottom layer is a metal sheet and is arranged on the lower surface of the middle layer; the four coupled microstrip lines are divided into two groups, the two groups of coupled microstrip lines are arranged on the upper surface of the middle layer in parallel and symmetrically, a gap exists between two microstrip lines in the same group of coupled microstrip lines, and a space is kept between the two groups of coupled microstrip lines; the active cell can move along the length direction of the stator, and comprises two layers: the upper layer is a dielectric plate, the lower layer is a square metal patch, the lower layer is arranged on the lower surface of the upper layer, and two ends of the square metal patch of the lower layer are respectively in electric contact with two coupling microstrip lines of which two groups are positioned at the inner side.
Preferably, two microstrip lines close to the outer side of the four coupled microstrip lines are respectively connected with the input port and the output port to form a two-port network; the input port and the output port are respectively connected with the SMA head.
Preferably, of the four coupled microstrip lines, two microstrip lines close to the inner side are both provided with through holes.
Preferably, the middle layer of the stator is a square dielectric plate.
Preferably, the stator intermediate layer has a dielectric constant of 3.66 and a loss tangent of 0.004.
Preferably, the upper layer of the mover is a square dielectric plate.
Preferably, the material of the dielectric plate on the upper layer of the rotor is the same as that of the dielectric plate on the middle layer of the stator.
The microwave displacement sensor can be applied to the space on the dielectric plate to a greater extent, so that the space occupied by the microwave displacement sensor is smaller compared with a device with the structure of other structures when the dynamic range of the same extent is measured. In addition, the displacement is measured by the calculation mode of the frequency difference of the transmission zero points, so that the stability of the measurement result is improved, and under the condition that the environmental factors are changed, the result is given by two resonance points on two sides of the central frequency, so that the stable measurement can be still given when the environment is changed.
By adopting the technical scheme of the invention, the result of measuring the displacement of the object to be measured from the original position is more accurate.
Drawings
FIG. 1 is a schematic structural diagram of a preferred embodiment of the present invention;
FIG. 2 is a parameter labeling diagram of the preferred embodiment of the present invention;
FIG. 3 is a schematic representation of the variation of the two-port transmission coefficient with the amount of displacement of the follower according to the present invention;
fig. 4 is a graph of the shift in frequency of two resonance points around the center frequency after the displacement of the object to be measured.
Detailed Description
The present invention will be described in further detail below with reference to the accompanying drawings and preferred embodiments.
As shown in fig. 1, the microwave displacement sensor based on the coupled microstrip line in this embodiment includes a stator and a mover, where the mover is connected to an object to be measured to measure a displacement of the object relative to the stator.
The stator is divided into three layers: the top layer 1-1 comprises four rectangular metal patches; the middle layer 1-2 is a dielectric plate; the bottom layer 1-3 is a metal foil.
In this embodiment, the middle dielectric layer 1-2 of the stator is a rectangular dielectric plate of rocky 4350 series, and has a dielectric constant of 3.66, a loss tangent of 0.004, and a thickness of 0.762mm. The length of the whole stator dielectric plate is 30mm, and the width of the whole stator dielectric plate is 20mm.
The upper surface of the square dielectric plate 1-2 is provided with a stator top layer 1-1 which is composed of two groups of coupled microstrip lines. Two groups of coupled microstrip line structures which are arranged side by side and symmetrically relate to four parallel microstrip lines, a gap exists between two microstrip lines in the same group of coupled microstrip lines, and a longer transverse distance also exists between the two groups of coupled microstrip lines. In this embodiment, the gap between two microstrip lines in the same group of coupled microstrip lines is set to be 0.3mm, and the distance between two groups of coupled microstrip lines is set to be 17.85mm. One of the two groups of coupled microstrip lines close to the inner side is provided with through holes 1-6, and the two groups of coupled microstrip lines are grounded to obtain better measurement performance.
Of the four coupled microstrip lines, the two microstrip lines near the outer side are respectively connected with the input port 1-4 and the output port 1-5, so that a two-port network is formed. The input port and the output port are respectively connected with an SMA head, and the SMA head is connected with a vector network analyzer.
The lower surface of the square dielectric plate 1-2 is provided with a stator bottom layer 1-3 which is a complete metal sheet and is used as the bottom surface of the whole sensor so as to ensure that the integrity of signals is not influenced.
The active cell is divided into two layers: the first layer 2-1 is a lower layer, which is a square metal patch, at the lower surface of the second layer; the second layer 2-2 employs a slab 2-2 of a roegis 4350 series square dielectric. Two ends of the rotor are respectively contacted with two microstrip lines of which the two groups of coupled microstrip lines are positioned at the inner side. The object to be measured connected with the mover moves to cause relative motion between the mover and the stator.
The second layer of dielectric plate material of the rotor is the same as the middle dielectric of the stator, and the length of the second layer of dielectric plate material is 19mm, so that the second layer of dielectric plate material crosses one of the two groups of coupled microstrip lines close to the inner side, and meanwhile, point contact can be ensured; the width is set to be 5mm to satisfy the demand of technology processing, too narrow dielectric plate is difficult to process.
The widths of four micro-strip lines on the stator are all 1.69 so as to achieve 50-ohm impedance matching; while the width of the metal patch of the mover is also set to 1.69mm. Two groups of coupled microstrip lines on the stator are parallel and in the same direction, and the terminals are approximately open-circuit or can be regarded as being connected to the ground by a capacitor. In this embodiment, the microstrip structure parameters are all set according to a standard of 50 ohms to match with an external measurement circuit, so as to prevent loss. For the coupled line structure, the gap between two adjacent microstrip lines is set to be 0.3mm, the distance between two groups of microstrip lines is set to be 17.85mm, the microstrip structure of the rotor is in electric contact with the top layer microstrip line of the stator, the properties of the two coupled microstrip lines are changed through the relative displacement of the rotor moving along the stator, and the frequency point of the output transmission zero point is influenced. For process consideration, the dimension of the dielectric plate of the stator is larger than that of the metal patch on the stator, the parameter of the metal layer still maintains the setting of the 50 ohm microstrip line parameter, and the width of the dielectric plate is larger than that of the metal patch and is set to be 5mm.
The two resonance points are changed by the movement of the mover, and the difference of the frequencies of the two resonance points is used for calculation, wherein the calculation process is as follows: and d is the ratio of the displacement to 1mm, and Δ f is the ratio of the difference between the right resonance point and the left resonance point to 1GHz, then:
d＝7.5×Δf+0.875
the sensor has the advantages of high sensitivity, high precision, simple structure, wide measurement range and strong practicability.
Fig. 2 is a parameter labeling diagram of the structure. Wherein, L1 represents the length of the stator dielectric slab, and W1 represents the width of the stator dielectric slab; l2 represents the length of the mover dielectric plate, and W2 represents the width of the mover dielectric plate; ls represents the length of the microstrip structure above the stator, ws represents the width of the microstrip structure above the stator, and the four microstrip lines which are coupled in the first two groups all adopt the same length and width; g represents the size of the gap between two microstrip lines in one group of coupling lines, and the two groups of coupling lines adopt the same gap. Lm indicates the length of the metal layer on the mover, and Wm indicates the width of the metal layer on the mover; d represents the transverse distance between the internal microstrip structures on the two coupling lines on the stator; ts represents the thickness of the stator dielectric plate, and Tm represents the thickness of the mover dielectric plate. The values of the various parameters were obtained by optimization, as shown in table 1:
TABLE 1
| Parameter(s) | L1 | W1 | L2 | W2 | Ls | Ws |
| Numerical value (mm) | 30 | 20 | 19 | 5 | 16 | 1.69 |
| Parameter(s) | Lm | Wm | D | Ts | Tm | G |
| Numerical value (mm) | 19 | 1.69 | 17.85 | 0.762 | 0.762 | 0.3 |
FIG. 3 is a transmission coefficient diagram showing the variation of the stator displacement within a certain frequency range of the dual port of the present invention. It can be seen that there are two resonance points within the frequency band as shown in fig. 3, one on each of the left and right sides of the center frequency. As the rotor moves towards one direction relative to the stator, the positions of the two transmission zero points are monotonously changed respectively. The transmission zero point positioned on the right side of the central frequency continuously moves to the right along with the displacement of the object to be measured; and the transmission zero point positioned on the left side of the central frequency continuously moves to the left along with the displacement of the object to be measured. Therefore, as the object to be measured moves in a certain direction, the difference between the transmission zero points on the left side and the transmission zero points on the right side will gradually increase, and the displacement of the movement of the object to be measured in the certain direction can be more accurately reflected according to the difference between the frequencies of the two transmission zero points. And according to the position of the transmission zero point of the output model, the displacement condition of the object to be detected can be deduced. The measurement mode shows the significance of sensitivity, and in addition, the stability of the performance when the environment changes can also more accurately give the measurement result as the advantage of the invention.
Fig. 4 shows the moving diagram of two resonance points around the center frequency in frequency after the object to be measured is displaced. As can be seen more clearly from this figure, the distance between the left and right resonance points becomes larger as the amount of displacement of the transverse axis increases. Initially, both resonance points are located at positions near the center frequency; and when the displacement of the object is increased, the two resonance points are farther away from the central frequency.
The foregoing is considered as illustrative of the preferred embodiments of the invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention.
Claims (7)
1. The microwave displacement sensor based on the coupling microstrip line is characterized by comprising a stator and a rotor;
the stator comprises three layers: the top layer consists of four rectangular coupling microstrip lines; the middle layer is a dielectric plate; the bottom layer is a metal sheet and is arranged on the lower surface of the middle layer; the four coupled microstrip lines are divided into two groups, the two groups of coupled microstrip lines are arranged on the upper surface of the middle layer in parallel and symmetrically, a gap exists between two microstrip lines in the same group of coupled microstrip lines, and a space is kept between the two groups of coupled microstrip lines;
the active cell can move along the length direction of the stator, and comprises two layers: the upper layer is a dielectric plate, the lower layer is a square metal patch, the lower layer is arranged on the lower surface of the upper layer, and two ends of the square metal patch of the lower layer are respectively in electric contact with two coupling microstrip lines of which two groups are positioned at the inner side.
2. The microwave displacement sensor based on coupled microstrip line according to claim 1, wherein: among the four coupled microstrip lines, two microstrip lines close to the outer side are respectively connected with the input port and the output port to form a two-port network; the input port and the output port are respectively connected with the SMA head.
3. The microwave displacement sensor based on coupled microstrip line according to claim 1 or 2, wherein: and among the four coupled microstrip lines, two microstrip lines close to the inner side are provided with through holes.
4. The microwave displacement sensor based on coupled microstrip line as claimed in claim 1, wherein: the middle layer of the stator is a square dielectric plate.
5. The microwave displacement sensor based on coupled microstrip line according to claim 1 or 4, wherein: the dielectric constant of the stator intermediate layer was 3.66 and the loss tangent was 0.004.
6. The microwave displacement sensor based on coupled microstrip line as claimed in claim 1, wherein: the upper layer of the rotor is a square medium plate.
7. A microwave displacement sensor based on coupled microstrip lines according to claim 1, 4 or 6, wherein: the material of the medium plate on the upper layer of the rotor is the same as that of the medium plate in the middle layer of the stator.
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