A sensor and detection method for environmental gas quality monitoring

Abstract

The present invention relates to a sensor and detection method for monitoring environmental gas quality, and belongs to the technical field of environmental monitoring. The sensor for monitoring environmental gas quality includes: a shell, the top of which is provided with an opening; a dielectric substrate, the dielectric substrate is fixedly arranged in the shell; a planar microstrip dipole antenna, the planar microstrip dipole antenna is fixedly connected to the surface of the dielectric substrate; a parasitic resonant cavity, the parasitic resonant cavity is fixedly connected to the upper surface of the dielectric substrate, and the planar microstrip dipole antenna is located in the parasitic resonant cavity; a sensitive dielectric layer, the sensitive dielectric layer is laid on the upper surface of the dielectric substrate, the planar microstrip dipole antenna and the parasitic resonant cavity, and part of the sensitive dielectric layer is exposed to the outside through the opening. The sensor for monitoring environmental gas quality has the advantages of small size, low power consumption, high detection sensitivity, fast real-time performance and easy integration.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring, and in particular relates to a sensor for monitoring environmental gas quality and a detection method. Background Art

[0002] As the battle to protect blue skies continues to advance, people's requirements for environmental gas purification are increasing, but industries such as petroleum, chemical and construction often produce unorganized emissions of toxic and harmful gases, posing a threat to people's health. At present, the pollution monitoring facilities are simple and inefficient, and it is impossible to conduct real-time and rapid monitoring of unorganized emissions, which has become a shortcoming in atmospheric environmental governance. The market is increasingly urgent for various sensors for real-time, efficient and highly sensitive toxic and harmful gas monitoring. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a sensor for monitoring environmental gas quality and a detection method. The sensor for monitoring environmental gas quality has the advantages of small size, low power consumption, high detection sensitivity, fast real-time performance and easy integration.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: A sensor for monitoring environmental gas quality, comprising:

[0005] A shell, wherein the top end of the shell is provided with an opening;

[0006] A dielectric substrate, the dielectric substrate is fixedly arranged in the housing;

[0007] A planar microstrip dipole antenna, wherein the planar microstrip dipole antenna is fixedly connected to the surface of the dielectric substrate;

[0008] A parasitic resonant cavity, wherein the parasitic resonant cavity is fixedly connected to the upper surface of the dielectric substrate, and the planar microstrip dipole antenna is located in the parasitic resonant cavity;

[0009] A sensitive dielectric layer is laid on the upper surfaces of the dielectric substrate, the planar microstrip dipole antenna and the parasitic resonant cavity, and a portion of the sensitive dielectric layer is exposed to the outside through the opening.

[0010] The beneficial effects of the present invention are as follows: by detecting the emission coefficient and resonant frequency of the reflected wave of the set planar microstrip dipole antenna, the sensitive dielectric layer can absorb toxic and harmful gases in the environment. After the sensitive dielectric layer absorbs the toxic and harmful gases in the environment, its dielectric constant will change, so that the emission coefficient and resonant frequency of the planar microstrip dipole antenna will change accordingly, and the degree to which the planar microstrip dipole antenna changes with the change of the dielectric constant of the sensitive dielectric layer can be obtained, thereby realizing the detection of toxic and harmful gases. At the same time, by setting the planar microstrip dipole antenna in the parasitic resonant cavity, the reflected wave of the planar microstrip dipole antenna is increased, so that the change of the emission coefficient and the resonant frequency is increased, so that the monitoring sensitivity of the monitoring sensor is greatly improved. The planar circuit design of the monitoring sensor can also be integrated with other microwave circuits to realize the miniaturization of the sensor, so as to better adapt to the development of the current Internet of Things technology. In the monitoring sensor, the input impedance and reflection coefficient of the sensor can be optimized by optimizing the geometric dimensions of the parasitic resonant cavity, thereby optimizing its parameters such as linearity and sensitivity.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Furthermore, the parasitic resonant cavity includes an outer square metal microstrip ring, an inner square metal microstrip ring and a metal connecting microstrip, the inner square metal microstrip ring is placed on the inner side of the outer square metal microstrip ring, one end of the metal connecting microstrip is fixedly connected to the outer wall of the inner square metal microstrip ring, and the other end is fixedly connected to the inner wall of the outer square metal microstrip ring, the outer square metal microstrip ring, the inner square metal microstrip ring and the metal connecting microstrip are all fixedly connected to the surface of the dielectric substrate, the planar microstrip dipole antenna is arranged on the inner side of the outer square metal microstrip ring, a gap is provided between one side outer wall of the inner square metal microstrip ring and one side outer wall of the planar microstrip dipole antenna, and one side outer wall of the inner square metal microstrip ring is coupled with one side outer wall of the planar microstrip dipole antenna through the gap.

[0013] The beneficial effect of adopting the above further scheme is that the reflected wave generated by the planar microstrip dipole antenna can be transmitted back and forth multiple times in the outer square metal microstrip ring and the inner square metal microstrip ring, so that the reflected wave is more enhanced and the resonance of the reflected wave is enhanced, which is conducive to detecting the change of the resonant frequency.

[0014] Furthermore, two inner square metal microstrip rings and two metal connecting microstrips are provided, the two inner square metal microstrip rings correspond to the two metal connecting microstrips one by one, and the two inner square metal microstrip rings are relatively arranged at the corners of the outer square metal microstrip ring.

[0015] The beneficial effect of adopting the above further solution is: better effect of enhancing the reflected wave.

[0016] Furthermore, the side length of the inner square metal microstrip ring is 5-12 mm, and the width is 1-5 mm; the length of the metal connecting microstrip is 1-5 mm, and the width is 1.5-3 mm.

[0017] The beneficial effect of adopting the above further solution is to prevent the entire sensor from being too large in size.

[0018] Furthermore, the outer square metal microstrip ring has a side length of 15-25 mm and a width of 1-6 mm.

[0019] The beneficial effect of adopting the above further solution is to prevent the entire sensor from being too large in size.

[0020] Furthermore, the width of the gap is 0.1-3 mm.

[0021] The beneficial effect of adopting the above further solution is that the parasitic resonant cavity within this range has a better enhancement effect on the reflected wave generated by the planar microstrip dipole antenna.

[0022] Furthermore, the planar microstrip dipole antenna includes two microstrip dipoles, a feeding point is provided between the two microstrip dipoles, one end of the feeding point passes through the dielectric substrate and out of the bottom end of the shell, and the two microstrip dipoles receive microwaves through the feeding point.

[0023] The beneficial effect of adopting the above further solution is: setting two microstrip dipoles can increase the output of the reflected wave, so that the enhancement effect in the parasitic resonant cavity is better.

[0024] Furthermore, the two microstrip dipoles are bent in a square shape, and the length of the two microstrip dipoles is 30-50 mm and the width is 6-10 mm.

[0025] The beneficial effect of adopting the above further solution is that it can reduce the occupied area, reduce the overall size of the sensor, and facilitate integration.

[0026] Furthermore, the thickness of the sensitive medium layer is 0.5-2 mm.

[0027] The beneficial effect of adopting the above further solution is: it has a good adsorption effect on toxic and harmful gases in the environment without increasing the thickness of the sensor.

[0028] The present invention also provides a detection method using the above-mentioned environmental gas quality monitoring sensor, comprising the following steps:

[0029] S1, taking a microwave generator, and connecting the output end of the microwave generator to the planar microstrip dipole antenna;

[0030] S2, the microwave generator generates microwaves, and the microwaves are transmitted to the planar microstrip dipole antenna. After receiving the microwaves, the planar microstrip dipole antenna generates reflected waves and scatters outwards. The reflected waves resonate, and the resonance of the reflected waves increases in the parasitic resonant cavity;

[0031] S3, detecting the reflection coefficient and the resonant frequency of the reflected wave generated in step S2, obtaining a standard reflection coefficient and a standard resonant frequency, drawing a standard relationship curve between the standard resonant frequency and the standard reflection coefficient, and obtaining a standard resonant frequency point;

[0032] S4, placing the sensor for monitoring environmental gas quality in the environment to be monitored, detecting and obtaining a post-reflection coefficient and a post-resonance frequency, and drawing a post-reflection relationship curve according to the post-reflection coefficient and the post-resonance frequency to obtain a post-resonance frequency point;

[0033] S5. Compare the standard resonant frequency obtained in step S3 with the post-resonant frequency obtained in step S4, and observe whether the post-resonant frequency is shifted. If harmful gas emissions are monitored, the post-resonant frequency is shifted, otherwise no harmful gas emissions are detected.

[0034] The beneficial effects of this detection method are: it is more convenient to detect toxic and harmful gases through this detection method. Compared with existing monitoring methods, the monitoring of toxic and harmful gases in the environment is more sensitive and timely, and feedback can be obtained in a timely manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the three-dimensional structure of the monitoring sensor of the present invention;

[0036] Figure 2 A top cross-sectional view of the monitoring sensor of the present invention;

[0037] Figure 3 It is a front cross-sectional view of the monitoring sensor of the present invention;

[0038] Figure 4 A curve diagram showing the relationship between the reflection coefficient and the resonance frequency of the monitoring sensor sample of the present invention;

[0039] Figure 5 is a curve diagram showing the relationship between the reflection coefficient and the resonance frequency of the comparative sample of the present invention;

[0040] Figure 6 This is the electric field distribution diagram of the working state of the monitoring sensor sample of the present invention.

[0041] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0042] 1. Shell, 2. Opening, 3. Sensitive dielectric layer, 4. Outer square metal microstrip ring, 5. Dielectric substrate, 6. Microstrip dipole, 7. Inner square metal microstrip ring, 8. Metal connecting microstrip, 9. Feeding point, 10. Gap. DETAILED DESCRIPTION

[0043] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0044] Example

[0045] like Figure 1-Figure 3 As shown, this embodiment provides a sensor for monitoring environmental gas quality, including: a housing 1, a dielectric substrate 5, a planar microstrip dipole 6 antenna, a parasitic resonant cavity and a sensitive dielectric layer 3.

[0046] The top of the shell 1 is provided with an opening 2, wherein the shell 1 is square, and the opening 2 is also square, wherein the shell 1 is used to place the dielectric substrate 5, the planar microstrip dipole 6 antenna, the parasitic resonant cavity and the sensitive dielectric layer 3, and is used to protect the dielectric substrate 5, the planar microstrip dipole 6 antenna, the parasitic resonant cavity and the sensitive dielectric layer 3. The shell 1 can be a hard plastic. The dielectric substrate 5 is fixedly arranged in the shell 1, and the dielectric substrate 5 is bonded and fixed to the bottom of the inner wall of the shell 1. The planar microstrip dipole 6 antenna is bonded and fixedly connected to the surface of the dielectric substrate 5, wherein the planar microstrip dipole 6 antenna is mainly used to receive microwaves and form reflected waves. The parasitic resonant cavity is fixedly connected to the upper surface of the dielectric substrate 5, and the planar microstrip dipole 6 antenna is located in the parasitic resonant cavity. The reflected wave generated by the planar microstrip dipole 6 antenna is strengthened by the parasitic resonant cavity, so that the resonance of the reflected wave is enhanced, thereby facilitating the detection of changes in the resonant frequency. The sensitive dielectric layer 3 is laid on the upper surface of the dielectric substrate 5, the planar microstrip dipole 6 antenna and the parasitic resonant cavity, and a portion of the sensitive dielectric layer 3 is exposed to the outside through the opening 2, wherein the sensitive dielectric layer 3 is used to adsorb toxic and harmful gases in the environment, wherein the media on the sensitive dielectric layer 3 are different, and the adsorbed toxic and harmful gases are different. When the sensitive dielectric layer 3 adsorbs toxic and harmful gases, the dielectric constant on the dielectric substrate 5 changes, thereby changing the resonant frequency of the planar microstrip dipole 6 antenna, thereby realizing the monitoring of toxic and harmful gases.

[0047] Specifically, in this embodiment, the parasitic resonant cavity includes an outer square metal microstrip ring 4, an inner square metal microstrip ring 7 and a metal connecting microstrip 8. The inner square metal microstrip ring 7 is placed on the inner side of the outer square metal microstrip ring 4. One end of the metal connecting microstrip 8 is fixedly connected to the outer wall of the inner square metal microstrip ring 7, and the other end is fixedly connected to the inner wall of the outer square metal microstrip ring 4. The outer square metal microstrip ring 4, the inner square metal microstrip ring 7 and the metal connecting microstrip 8 are all fixedly connected to the surface of the dielectric substrate 5. The planar microstrip dipole 6 antenna is arranged on the inner side of the outer square metal microstrip ring 4. The inner square metal microstrip ring 7 is fixedly connected to the inner wall of the outer square metal microstrip ring 4. A gap 10 is provided between one side outer wall and one side outer wall of the planar microstrip dipole 6 antenna, and one side outer wall of the inner square metal microstrip ring 7 is coupled with one side outer wall of the planar microstrip dipole 6 antenna through the gap 10, so that the reflected wave of the planar microstrip dipole 6 antenna is transmitted to the outer wall of the inner square metal microstrip ring 7, and then returns to the planar microstrip dipole 6 antenna, so that the reflected wave is transmitted back and forth between the side wall of the planar microstrip dipole 6 antenna and the outer wall of the inner square metal microstrip ring 7 and the inner wall of the outer square metal microstrip ring 4, thereby increasing the intensity of the reflected wave and enhancing the resonance of the reflected wave. The outer square metal microstrip ring 4, the inner square metal microstrip ring 7 and the metal connecting microstrip 8 are made of the same metal material.

[0048] Specifically, in this embodiment, two inner square metal microstrip rings 7 and two metal connection microstrips 8 are provided, and the two inner square metal microstrip rings 7 correspond to the two metal connection microstrips 8 one by one, and the two inner square metal microstrip rings 7 are relatively arranged at the corners of the outer square metal microstrip ring 4, wherein one end of the metal connection microstrip 8 is fixedly connected to the inner wall of one vertex of the outer square metal microstrip ring 4, and the other end is fixedly connected to the outer wall of one vertex of the corresponding inner square metal microstrip ring 7. The two inner square metal microstrip rings 7 are located on both sides of the planar microstrip dipole 6 antenna.

[0049] Preferably, in the present embodiment, the side length of the inner square metal microstrip ring 7 is 5-12 mm, and the width is 1-5 mm; the length of the metal connecting microstrip 8 is 1-5 mm, and the width is 1.5-3 mm.

[0050] Preferably, in this embodiment, the side length of the outer square metal microstrip ring 4 is 15-25 mm, and the width is 1-6 mm.

[0051] Preferably, in this embodiment, the width of the gap 10 is 0.1-3 mm.

[0052] Specifically, the planar microstrip dipole 6 antenna in this embodiment includes two microstrip dipoles 6, a feeding point 9 is provided between the two microstrip dipoles 6, one end of the feeding point 9 passes through the dielectric substrate 5 and passes through the bottom end of the shell 1, and the feeding point 9 is used to connect to an external microwave generator, and the two microstrip dipoles 6 receive microwaves through the feeding point 9, so that the microstrip dipoles 6 receive microwaves. The two microstrip dipoles 6 and the feeding point 9 are prior art, and are well-known to those skilled in the art. The two microstrip dipoles 6 are arranged relative to each other, and one end of the two microstrip dipoles 6 is arranged close to each other, and the feeding point 9 is arranged between the two ends of the two microstrip dipoles 6.

[0053] Specifically, in the present embodiment, the two microstrip dipoles 6 are bent in a square shape, which can reduce the footprint and the overall size of the sensor. The length of the microstrip dipole 6 determines the resonant frequency of the microstrip dipole 6. In the present embodiment, the length L of the microstrip dipole 6 is 0.5λ, λ is the operating frequency of the dielectric substrate 5, and the width a of the microstrip dipole 6 is a≤L / 5. The length of the two microstrip dipoles 6 is 30-50 mm, and the width is 6-10 mm.

[0054] Specifically, in this embodiment, the thickness of the sensitive medium layer 3 is 0.5-2 mm, and the shape of the sensitive medium layer 3 is consistent with the shape of the medium substrate 5, wherein a portion of the sensitive medium layer 3 is exposed from the opening 2 to facilitate the adsorption of toxic and harmful gases. This makes the sensitive medium layer 3 more effective in adsorbing toxic and harmful gases, thereby improving the detection accuracy of the gas monitoring sensor. The medium on the sensitive medium layer 3 can be tin oxide, and of course the medium on the sensitive medium layer 3 can also be other materials, which can be selected according to the type of toxic and harmful gases to be detected. Tin oxide or other materials can be plated on the substrate by screen printing or magnetron sputtering for use.

[0055] This embodiment also provides a detection method using the above-mentioned environmental gas quality monitoring sensor, comprising the following steps:

[0056] S1. Take a microwave generator and connect the output end of the microwave generator to the feeding point 9.

[0057] S2. The microwave generator generates microwaves, which are transmitted to the microstrip dipole 6 via the feeding point 9. After receiving the microwaves, the microstrip dipole 6 generates reflected waves and scatters outward. The reflected waves resonate when scattered. Since the microstrip dipole 6 is inside the outer square metal microstrip ring 4 and coupled with the inner square metal microstrip ring 7, the reflected waves generated by the microstrip dipole 6 are transmitted back and forth inside the outer square metal microstrip ring 4, so that the reflected waves are enhanced and the resonance of the reflected waves is enhanced.

[0058] S3, detecting the reflection coefficient and the resonant frequency of the reflected wave generated in step S2. Since the dielectric constant of the dielectric substrate 52 is a stable value, a standard reflection coefficient and a standard resonant frequency are obtained. Based on the standard reflection coefficient and the standard resonant frequency, a standard relationship curve between the standard resonant frequency and the standard reflection coefficient is drawn, and the standard resonant frequency point is obtained based on the standard relationship curve.

[0059] S4. Place the sensor for environmental gas quality monitoring in the environment to be monitored, detect the reflection coefficient and resonant frequency of the reflected wave generated by the microstrip dipole 6 in real time, obtain the post-reflection coefficient and the post-resonant frequency, draw a post-reflection relationship curve based on the post-reflection coefficient and the post-resonant frequency, and obtain the post-resonant frequency point based on the post-reflection relationship curve.

[0060] S5. Compare the standard resonant frequency obtained in step S3 with the post-resonant frequency obtained in step S4 to observe whether the post-resonant frequency is offset. If harmful gas emissions are monitored, the post-resonant frequency is offset relative to the standard resonant frequency. Otherwise, no harmful gas emissions are detected.

[0061] The detection principle is as follows: when the environmental gas quality monitoring sensor is placed in the environment to be detected, when toxic and harmful gases are discharged, the sensitive medium layer 3 will absorb the toxic and harmful gases in the environment. After the sensitive medium layer 3 absorbs the toxic and harmful gases, the dielectric constant of the dielectric substrate 5 will change, thereby changing the dielectric constant of the entire sensor. When the microstrip dipole 6 receives microwaves, a reflected wave will be generated, and the reflected wave will resonate when scattered. Since the microstrip dipole 6 is in the outer square metal microstrip ring 4 and coupled with the inner square metal microstrip ring 7, the reflected wave generated by the microstrip dipole 6 is transmitted back and forth in the outer square metal microstrip ring 4, so that the reflected wave is enhanced, and the resonance of the reflected wave is enhanced, so that the change in the resonant frequency of the reflected wave is more obvious. When the dielectric constant of the entire sensor changes, the resonant frequency generated by the reflected wave follows the change, so that the post-resonant frequency can be measured, and then the post-reflection coefficient and the post-resonant frequency are plotted. The post-resonant relationship curve is obtained based on the post-reflection coefficient and the post-resonant frequency to obtain the post-resonant frequency point. The post-resonant frequency point is offset compared with the standard resonant frequency point.

[0062] The following is a specific measurement using the above embodiment.

[0063] A monitoring sensor sample is prepared according to the above embodiment, and the geometric parameters of its various parts are shown in Table 1.

[0064] Table 1

[0065] part value The length of the microstrip dipole 6 40mm Width of microstrip dipole 6 5mm The side length of the inner square metal microstrip ring 7 13.1mm Width of inner square metal microstrip ring 7 2.6mm The thickness of the inner square metal microstrip ring 7 0.018mm The side length of the outer square metal microstrip ring 4 45.7mm Width of outer square metal microstrip ring 4 3.4mm The thickness of the outer square metal microstrip ring 4 0.018mm Gap 10 spacing 2.7mm Width of the metal connecting microstrip 8 2.1mm The length of the metal connecting microstrip 8 1.7mm Thickness of sensitive medium layer 3 0.5mm Thickness of the metal connecting microstrip 8 0.018mm The thickness of the dielectric substrate 5 0.5mm The side length of the dielectric substrate 5 55mm

[0066] The dielectric constant εr of the dielectric substrate 5 of this sample is 3.02. The dielectric constant εr of the entire gas detection sensor is 3.0.

[0067] By placing the monitoring sensor in a preset environment to be tested, the reflection coefficient S 11 The sensitive medium layer 3 in the monitoring sensor continuously adsorbs toxic and harmful gases, thereby increasing the dielectric constant. Specifically, the inventor selected the dielectric constants εr of 6, 9, 12 and 15 and the dielectric constant εr of 3.0, and integrated them together. Figure 4 As shown, from Figure 4 It can be seen intuitively that the resonant frequency is constantly shifting with the change of the dielectric constant. This shows that the monitoring sensor can accurately detect toxic and harmful gases with very high detection accuracy. At the same time, the inventors also fit the change of the resonant frequency and the dielectric constant into a linear relationship, where the linearity is >0.96. It can be calculated that the detection sensitivity of the sensor is 261MHz / εr at this time, which is 3 times higher than the sensitivity of the microstrip sensor resonant unit reported in traditional literature, and 5 times higher than the sensitivity of the traditional microfluidic sensor of 57.3MHz / εr (Diao Lianbao, Master's thesis of Taiyuan University of Technology, Research on wide-band microstrip refractive index sensor based on metamaterials, June 2017).

[0068] In addition, the parasitic resonant cavity proposed in the present invention plays a vital role in improving the sensitivity of the sensor. In order to compare the effect, the inventor also made a microstrip dipole 6 antenna sample without a parasitic resonant cavity. When the other dimensions of the sample are the same, the resonant frequency and the reflection coefficient S 11 The relationship is as Figure 5 As shown, from Figure 5 It can be seen that the change of the resonant frequency is minimal, and it is very difficult to determine whether the resonant frequency is offset. Its sensitivity is only 89MHz / εr.

[0069] In addition, the inventors also tested the electric field distribution of the monitoring sensor in the working state when the dielectric constant εr is 3.0. Figure 6 As shown, from Figure 6 It can be seen that through the study of the electric field distribution, it is found that when the monitoring sensor is working, the electric field energy is mainly concentrated near the microstrip dipole 6 and the inner square metal microstrip ring 7, or it is precisely because of the existence of the parasitic resonant cavity that the current distribution on the microstrip dipole 6 is regulated, the radiation mode is changed, and the reflection coefficient of the microstrip dipole 6 is more sensitive to the change of the dielectric constant, thereby improving the detection sensitivity of the sensor.

[0070] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A sensor for monitoring environmental gas quality, characterized in that: include: A shell (1), wherein the top end of the shell (1) is provided with an opening (2); A dielectric substrate (5), the dielectric substrate (5) being fixedly arranged in the housing (1); A planar microstrip dipole (6) antenna, wherein the planar microstrip dipole (6) antenna is fixedly connected to the surface of the dielectric substrate (5); A parasitic resonant cavity, the parasitic resonant cavity being fixedly connected to the upper surface of the dielectric substrate (5), and the planar microstrip dipole (6) antenna being located in the parasitic resonant cavity; A sensitive dielectric layer (3), the sensitive dielectric layer (3) being laid on the upper surface of the dielectric substrate (5), the planar microstrip dipole (6) antenna and the parasitic resonant cavity, and a portion of the sensitive dielectric layer (3) being exposed to the outside through the opening (2); The parasitic resonant cavity comprises an outer square metal microstrip ring (4), an inner square metal microstrip ring (7) and a metal connecting microstrip (8); the inner square metal microstrip ring (7) is arranged on the inner side of the outer square metal microstrip ring (4); one end of the metal connecting microstrip (8) is fixedly connected to the outer wall of the inner square metal microstrip ring (7), and the other end is fixedly connected to the inner wall of the outer square metal microstrip ring (4); the outer square metal microstrip ring (4), the inner square metal microstrip ring (7) and the metal connecting microstrip (8) are all fixedly connected to the surface of the dielectric substrate (5); the planar microstrip dipole (6) antenna is arranged on the inner side of the outer square metal microstrip ring (4); a gap (10) is provided between one side outer wall of the inner square metal microstrip ring (7) and one side outer wall of the planar microstrip dipole (6) antenna; one side outer wall of the inner square metal microstrip ring (7) and one side outer wall of the planar microstrip dipole (6) antenna are coupled via the gap (10).

2. The sensor for monitoring environmental gas quality according to claim 1, characterized in that: Two of the inner square metal microstrip rings (7) and two of the metal connecting microstrips (8) are provided, the two inner square metal microstrip rings (7) correspond to the two metal connecting microstrips (8) in a one-to-one manner, and the two inner square metal microstrip rings (7) are arranged relatively at the corners of the outer square metal microstrip ring (4).

3. The sensor for monitoring environmental gas quality according to claim 1, characterized in that: The inner square metal microstrip ring (7) has a side length of 5-15 mm and a width of 1-5 mm; the metal connecting microstrip (8) has a length of 1-5 mm and a width of 1.5-3 mm.

4. The sensor for monitoring environmental gas quality according to claim 1, characterized in that: The outer square metal microstrip ring (4) has a side length of 25-50 mm and a width of 1-6 mm.

5. The sensor for monitoring environmental gas quality according to claim 1, characterized in that: The width of the gap (10) is 0.1-3 mm.

6. The sensor for monitoring environmental gas quality according to claim 1, characterized in that: The planar microstrip dipole (6) antenna comprises two microstrip dipoles (6), a feeding point (9) is provided between the two microstrip dipoles (6), one end of the feeding point (9) passes through the dielectric substrate (5) and passes out of the bottom end of the housing (1), and the two microstrip dipoles (6) receive microwaves through the feeding point (9).

7. The sensor for monitoring environmental gas quality according to claim 6, characterized in that: The two microstrip dipoles (6) are bent in a square shape, and the length of the two microstrip dipoles (6) is 30-50 mm, and the width is 6-10 mm.

8. The sensor for monitoring environmental gas quality according to any one of claims 1 to 7, characterized in that: The thickness of the sensitive medium layer (3) is 0.5-2 mm.

9. A detection method using the sensor for monitoring environmental gas quality according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, taking a microwave generator, and connecting the output end of the microwave generator to the planar microstrip dipole (6) antenna; S2, the microwave generator generates microwaves, and the microwaves are transmitted to the planar microstrip dipole (6) antenna. After receiving the microwaves, the planar microstrip dipole (6) antenna generates reflected waves and scatters outwards. The reflected waves resonate, and the resonance of the reflected waves increases in the parasitic resonant cavity; S3, detecting the reflection coefficient and the resonant frequency of the reflected wave generated in step S2, obtaining a standard reflection coefficient and a standard resonant frequency, drawing a standard relationship curve between the standard resonant frequency and the standard reflection coefficient, and obtaining a standard resonant frequency point; S4, placing the sensor for monitoring environmental gas quality in the environment to be monitored, detecting and obtaining a post-reflection coefficient and a post-resonance frequency, and drawing a post-reflection relationship curve according to the post-reflection coefficient and the post-resonance frequency to obtain a post-resonance frequency point; S5. Compare the standard resonant frequency obtained in step S3 with the post-resonant frequency obtained in step S4, and observe whether the post-resonant frequency is shifted. If harmful gas emissions are monitored, the post-resonant frequency is shifted, otherwise no harmful gas emissions are detected.

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