An RFID sensor for water pipe leakage detection

Abstract

The present invention discloses an RFID sensor for detecting water pipe leakage, comprising a first RF transceiver, a second RF transceiver, a coding module and a sensing module. When used for water pipe leakage detection, the sensing module detects the current state of the detected water pipe in real time and generates sensing information representing the current state of the water pipe. The first RF transceiver receives the RF signal and transmits it to the coding module. The coding module loads the coding information into the RF signal and sends it to the sensing module. The sensing module loads the sensing information into the RF signal and sends it to the second RF transceiver. The second RF transceiver transmits the RF signal with the coding information and the sensing information into free space. The advantage is that it is implemented using a chipless RFID tag, which can replace traditional semiconductor sensors and be arranged as a sensing node under the water pipe to detect the state of the water pipe. In addition, under large-scale deployment, the cost is low and no complex connection lines are required between the terminal processing system, which has great application prospects.

Description

Technical Field

[0001] The present invention relates to an RFID sensor, in particular to an RFID sensor for detecting water pipe leakage. Background Art

[0002] In modern buildings, water pipe layout is an essential part. However, after long-term use, water pipes are prone to aging, damage, or loose joints, which can lead to water leakage, affecting the home experience, building life, and factory and laboratory safety. Traditional water pipe leakage detection solutions usually use direct detection and positioning technology. Pipeline leakage detection is performed by placing humidity or other gas sensors around the pipes. The sensors can more sensitively sense water leakage around the pipes and generate corresponding signals to send to the back-end terminal processing system, which triggers an alarm. However, the sensors used in traditional direct detection and positioning technology are usually semiconductor components, which are easily damaged by water erosion, have poor robustness, and a short service life. In addition, in large-scale deployments, complex connection lines are required between the sensors and the terminal processing system, which is not conducive to processing and manufacturing. The cost of semiconductor components is also high, which greatly limits its commercial application.

[0003] Radio Frequency Identification (RFID) technology uses electromagnetic signals to detect specific targets and read related data without establishing mechanical or optical contact with the specific target. A typical RFID system consists of three parts: an application system, a reader, and an RFID tag, among which the RFID tag plays an important role. Traditional RFID tags are implemented using semiconductor components and are relatively expensive. Current chipless RFID tags eliminate semiconductor components, reducing the cost of RFID tags and enhancing the robustness of RFID tags. In addition, chipless RFID tags can combine encoding and sensing functions to use RFID to identify the address, locate, and track objects, and can also detect the physical characteristics of the attached objects, such as temperature, humidity, gas, displacement, etc.

[0004] In view of this, chipless RFID tags can replace traditional semiconductor sensors and be deployed as sensing nodes under water pipes to detect the status of the water pipes. In large-scale deployment, they are low-cost and do not require complex connection lines between them and the terminal processing system, so they have great application prospects. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an RFID sensor for detecting water pipe leakage. The RFID sensor is implemented using a chipless RFID tag, which can replace traditional semiconductor sensors and is arranged as a sensing node under the water pipe to detect the status of the water pipe. In addition, it has low cost when deployed on a large scale and does not require complex connection lines between the terminal processing system, so it has great application prospects.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: an RFID sensor for water pipe leakage detection, including a first radio frequency transceiver, a second radio frequency transceiver, an encoding module and a sensing module, the output end of the first radio frequency transceiver is connected to the input end of the encoding module, the output end of the encoding module is connected to the input end of the sensing module, the output end of the sensing module is connected to the input end of the second radio frequency transceiver, the input end of the first radio frequency transceiver is used to receive a radio frequency signal, and the radio frequency signal is a broadband radio frequency signal of a set frequency band, and the frequency band of the broadband radio frequency signal includes The coding frequency band and the sensing frequency band are configured such that the coding module can load the coding information representing the identity information of the RFID sensor into the coding frequency band of the radio frequency signal and send the radio frequency signal with the coding information to the sensing module. The sensing module can load the sensing information representing the current state of the water pipe obtained by the current detection into the sensing frequency band of the radio frequency signal with the numbering signal, obtain the radio frequency signal with the coding information and the sensing information and send it to the second radio frequency transceiver. The output end of the second radio frequency transceiver is used to transmit the radio frequency signal with the coding information and the sensing information to the free space to be processed by the terminal processing system. The system receives the signal; when used for water pipe leakage detection, the sensor module is arranged under the detected water pipe and in contact with the detected water pipe. The sensor module detects the current state of the detected water pipe in real time and generates sensor information representing the current state of the water pipe. When the first RF transceiver receives the RF signal, the first RF transceiver transmits the RF signal to the encoding module. The encoding module loads the encoding information representing the identity information of the RFID sensor within the encoding frequency band of the RF signal, obtains the RF signal with the encoding information and sends it to the sensor module. The sensor The sensing module loads the currently obtained sensing information within the sensing frequency band of the radio frequency signal with the coding information, obtains the radio frequency signal with the coding information and the sensing information and sends it to the second radio frequency transceiver, and the output end of the second radio frequency transceiver transmits the radio frequency signal with the coding information and the sensing information to free space. The terminal processing system can receive the radio frequency signal with the coding information and the sensing information, and determine the identity information of the RFID sensor according to the coding information in the radio frequency signal with the coding information and the sensing information. The sensing information determines whether the water pipe at the RFID sensor corresponding to the identity information is leaking, thereby realizing water pipe leakage detection.

[0007] The first RF transceiver includes a first dielectric substrate, a first radiating structure, a first feeding structure and a first rectangular metal ground. The first dielectric substrate is a rectangular plate. The first radiating structure includes a first triangular metal block, a second triangular metal block and a first rectangular metal block. The first triangular metal block, the second triangular metal block and the first rectangular metal block are all attached to the upper surface of the first dielectric substrate. The front end face of the first rectangular metal block is parallel to the front end face of the first dielectric substrate. The length of the first rectangular metal block in the left-right direction is less than the length of the first dielectric substrate in the left-right direction. The symmetry line of the first rectangular metal block in the front-back direction coincides with the symmetry line of the first dielectric substrate in the front-back direction. The first triangular metal block and the second triangular metal block are located in front of the first rectangular metal block, and the first triangular metal block is located on the left side of the second triangular metal block and the two are symmetrical. The end face where one right-angled side of the first triangular metal block is located and the end face where one right-angled side of the second triangular metal block is located are both in contact with the front end face of the first rectangular metal block, and the end face where the other right-angled side of the first triangular metal block is in contact with the left side of the first rectangular metal block. The end faces are located in the same plane, the end face where the other right-angled side of the second triangular metal block is located is located in the same plane as the right end face of the first rectangular metal block, the sum of the length of the end face where one right-angled side of the first triangular metal block is located in the left-right direction and the length of the end face where one right-angled side of the second triangular metal block is located in the left-right direction is equal to the length of the first rectangular metal block in the left-right direction, and the sum of the length of the end face where the other right-angled side of the first triangular metal block is located in the front-to-back direction and the length of the first rectangular metal block in the front-to-back direction is less than the length between the plane where the rear end face of the first rectangular metal block is located and the plane where the first inter the distance between the plane where the front end surface of the first rectangular metal block is located and the plane where the front end surface of the dielectric substrate is located, the first rectangular metal ground is attached to the lower surface of the first dielectric substrate, the rear end surface of the first rectangular metal ground is located in the same plane as the rear end surface of the first dielectric substrate, the left end surface of the first rectangular metal ground is located in the same plane as the left end surface of the first dielectric substrate, and the right end surface of the first rectangular metal ground is located in the same plane as the right end surface of the first dielectric substrate, and the distance from the front end surface of the first rectangular metal ground to its rear end surface is smaller than the distance from the plane where the rear end surface of the first rectangular metal block is located to the plane where the rear end surface of the first dielectric substrate is located;The first feeding structure includes a second rectangular metal block, a third rectangular metal block and a fourth rectangular metal block. The second rectangular metal block, the third rectangular metal block and the fourth rectangular metal block are all attached to the upper surface of the first dielectric substrate. The second rectangular metal block is located on the rear side of the first rectangular metal block. The front end face of the second rectangular metal block is in contact with the rear end face of the first rectangular metal block. The length of the second rectangular metal block in the left-right direction is less than the length of the first rectangular metal block in the left-right direction. The symmetry line of the second rectangular metal block in the front-back direction coincides with the symmetry line of the first rectangular metal block in the front-back direction. The three rectangular metal blocks are located on the rear side of the second rectangular metal block, the left end face of the third rectangular metal block is flush with the left end face of the second rectangular metal block, the front end face of the third rectangular metal block is in contact with the rear end face of the second rectangular metal block, the length of the third rectangular metal block in the left-right direction is greater than the length of the second rectangular metal block in the left-right direction, the fourth rectangular metal block is located on the right side of the third rectangular metal block, the left end face of the fourth rectangular metal block is in contact with the right end face of the third rectangular metal block, the length of the fourth rectangular metal block in the front-to-back direction is greater than the length of the third rectangular metal block in the front-to-back direction, and the fourth rectangular The right end face of the rectangular metal block is flush with the right end face of the first dielectric substrate, the symmetry line of the fourth rectangular metal block in the left-right direction coincides with the symmetry line of the third rectangular metal block in the left-right direction, the rear end face of the fourth rectangular metal block is located in front of the rear end face of the first dielectric substrate, and the plane where the front end face of the fourth rectangular metal block is located is located in the rear side of the plane where the front end face of the first rectangular metal ground is located; the second RF receiver includes a second dielectric substrate, a second radiating structure, a second feeding structure and a second rectangular metal ground, the second radiating structure includes a third triangular metal block, a fourth triangular metal block and a fifth rectangular metal block, the third triangular metal block The first and second triangular metal blocks are all attached to the upper surface of the second dielectric substrate. The front end surface of the fifth rectangular metal block is parallel to the front end surface of the second dielectric substrate. The length of the fifth rectangular metal block in the front-to-back direction is less than the length of the second dielectric substrate in the front-to-back direction. The symmetry line of the fifth rectangular metal block in the left-to-right direction coincides with the symmetry line of the second dielectric substrate in the left-to-right direction. The third and fourth triangular metal blocks are located to the right of the fifth rectangular metal block. The third triangular metal block is located in front of the fourth triangular metal block and the two are symmetrical in front-to-back direction.The end face where one right-angled side of the third triangular metal block is located and the end face where one right-angled side of the fourth triangular metal block is located are both in contact with the right end face of the fifth rectangular metal block, the end face where another right-angled side of the third triangular metal block is located and the front end face of the fifth rectangular metal block are located in the same plane, the end face where another right-angled side of the fourth triangular metal block is located and the rear end face of the fifth rectangular metal block are located in the same plane, the sum of the length of the end face where one right-angled side of the third triangular metal block along the front-to-back direction and the length of the end face where one right-angled side of the fourth triangular metal block along the front-to-back direction is equal to the length of the fifth rectangular metal block along the front-to-back direction; the third triangular metal block The sum of the length of the end face where the other right-angled side is located in the left-right direction and the length of the fifth rectangular metal block in the left-right direction is less than the distance between the plane where the left end face of the fifth rectangular metal block is located and the plane where the right end face of the second dielectric substrate is located. The second rectangular metal ground is attached to the lower surface of the second dielectric substrate. The left end face of the second rectangular metal ground and the left end face of the second dielectric substrate are located in the same plane. The front end face of the second rectangular metal ground and the front end face of the second dielectric substrate are located in the same plane. The rear end face of the second rectangular metal ground and the rear end face of the second dielectric substrate are located in the same plane. The distance from the left end face of the second rectangular metal ground to its right end face is less than The distance from the plane where the left end face of the fifth rectangular metal block is located to the plane where the left end face of the second dielectric substrate is located; the second feeding structure includes a sixth rectangular metal block and a seventh rectangular metal block, the sixth rectangular metal block and the seventh rectangular metal block are both attached to the upper surface of the second dielectric substrate, the sixth rectangular metal block is located on the left side of the fifth rectangular metal block, the right end face of the sixth rectangular metal block is in contact with the left end face of the fifth rectangular metal block, the length of the sixth rectangular metal block along the front-to-back direction is less than the length of the fifth rectangular metal block along the front-to-back direction, the seventh rectangular metal block is located on the left side of the sixth rectangular metal block, and the left end face of the seventh rectangular metal block is in contact with the The left end surface of the second dielectric substrate is flush with the right end surface of the seventh rectangular metal block and is in contact with the left end surface of the sixth rectangular metal block. The length of the seventh rectangular metal block in the front-to-back direction is greater than the length of the sixth rectangular metal block in the front-to-back direction and less than the length of the fifth rectangular metal block in the front-to-back direction. The symmetry line of the fifth rectangular metal block in the left-to-right direction, the symmetry line of the sixth rectangular metal block in the left-to-right direction, and the symmetry line of the seventh rectangular metal block in the left-to-right direction coincide with each other. The rear end surface of the seventh rectangular metal block is located in front of the rear end surface of the second dielectric substrate. The plane where the right end surface of the seventh rectangular metal block lies is located to the left of the plane where the right end surface of the second rectangular metal substrate lies.The coded information is binary coded data, and the coding module includes a third dielectric substrate, a first rectangular main transmission line, nm rectangular microstrip resonators, and a third rectangular metal ground, wherein n is the number of bits of the coded information, and m is the number of "0"s in the coded information. The coding frequency band is divided into nm frequency bands, and the nm rectangular microstrip resonators correspond one-to-one to the nm frequency bands. Each rectangular microstrip resonator can generate a resonance point within its corresponding frequency band. When the rectangular microstrip resonator generates a resonance point, the code is "1", otherwise the code is "0". The third dielectric plate is a rectangular plate, and the first rectangular main transmission line is a metal transmission line attached to the upper surface of the third dielectric substrate. The plane where the front end surface of the first rectangular main transmission line is located is parallel to the plane where the front end surface of the third dielectric substrate is located. The length of the first rectangular main transmission line in the front-to-back direction is less than the length of the third dielectric substrate in the front-to-back direction. The distance between the plane where the rear end face of the first rectangular main transmission line is located and the plane where the rear end face of the third dielectric substrate is located is equal to the distance between the plane where the rear end face of the fourth rectangular metal block is located and the plane where the rear end face of the first dielectric substrate is located. The distance between the plane where the front end face of the first rectangular main transmission line is located and the plane where the front end face of the third dielectric substrate is located is equal to the distance between the plane where the front end face of the fourth rectangular metal block is located and the plane where the front end face of the first dielectric substrate is located. The left end face of the first rectangular main transmission line and the left end face of the third dielectric substrate are located in the same plane, and the right end face of the first rectangular main transmission line and the right end face of the third dielectric substrate are located in the same plane.The nm rectangular microstrip resonators are realized by using nm rectangular metal blocks. The nm rectangular microstrip resonators are respectively attached to the upper surface of the third dielectric substrate. The nm rectangular resonators are located on the front side of the first rectangular main transmission line. The rear end faces of the nm rectangular resonators are all in contact with the front end face of the first rectangular main transmission line. The nm rectangular resonators are spaced apart from each other from left to right. The lengths of the nm rectangular resonators along the front-to-back direction increase from left to right. The lengths of the nm rectangular resonators along the front-to-back direction are all shorter than the distance from the plane where the front end face of the first rectangular main transmission line is located to the third dielectric substrate. The distance between the front end surface of the plate and the plane where the left end surface of the rectangular resonator is located is the distance between the front end surface of the plate and the plane where the left end surface of the rectangular resonator located on the far left is located on the right side of the left end surface of the third dielectric substrate, and the plane where the right end surface of the rectangular resonator located on the far right is located on the left side of the right end surface of the third dielectric substrate. The third rectangular metal ground is attached to the lower surface of the third dielectric substrate, the rear end surface of the third rectangular metal ground is in the same plane as the rear end surface of the third dielectric substrate, the front end surface of the third rectangular metal ground is in the same plane as the front end surface of the third dielectric substrate, and the left end surface of the third rectangular metal ground is in the same plane as the third dielectric substrate. The left end surface of the dielectric substrate is located in the same plane, and the right end surface of the third rectangular metal ground is located in the same plane as the right end surface of the third dielectric substrate; the sensing module includes a fourth dielectric substrate, a second rectangular main transmission line, a defect ground and a sensing layer, the fourth dielectric substrate is a rectangular plate, the second rectangular main transmission line is a metal transmission line attached to the upper surface of the fourth dielectric substrate, the front end surface of the second rectangular main transmission line is located in a plane parallel to the front end surface of the fourth dielectric substrate, the length of the second rectangular main transmission line in the front-to-back direction is less than the length of the fourth dielectric plate in the front-to-back direction, and the rear end of the second rectangular main transmission line is The distance from the plane where the front end face of the second rectangular main transmission line is located to the plane where the rear end face of the fourth dielectric substrate is located is equal to the distance from the plane where the rear end face of the first rectangular main transmission line is located to the plane where the rear end face of the third dielectric substrate is located; the distance from the plane where the front end face of the second rectangular main transmission line is located to the plane where the front end face of the fourth dielectric substrate is located is equal to the distance from the plane where the front end face of the first rectangular main transmission line is located to the plane where the front end face of the third dielectric substrate is located; the left end face of the second rectangular main transmission line and the left end face of the fourth dielectric substrate are located in the same plane; and the right end face of the second rectangular main transmission line and the right end face of the fourth dielectric substrate are located in the same plane;The defective ground is arranged on the lower surface of the fourth dielectric substrate, and the defective ground includes a ninth rectangular metal block, a first rectangular air slot, a second rectangular air slot, and a third rectangular air slot attached to the lower surface of the fourth dielectric substrate. The front end face of the ninth rectangular metal block and the front end face of the fourth dielectric substrate are located in the same plane, the rear end face of the ninth rectangular metal block and the rear end face of the fourth dielectric substrate are located in the same plane, the left end face of the ninth rectangular metal block and the left end face of the fourth dielectric substrate are located in the same plane, the right end face of the ninth rectangular metal block and the right end face of the fourth dielectric substrate are located in the same plane, the first rectangular air slot, the second rectangular air slot, and the The third rectangular air slots are respectively opened on the ninth rectangular metal block, the lower surface of the fourth dielectric substrate is exposed at the first rectangular air slot, the second rectangular air slot and the third rectangular air slot, the symmetry line of the first rectangular air slot along the left-right direction coincides with the symmetry line of the second rectangular main transmission line along the left-right direction, the second rectangular air slot and the third rectangular air slot are both located on the left side of the first rectangular air slot, the second rectangular air slot is located in front of the third rectangular air slot, the right end face of the second rectangular air slot is in contact with the left end face of the first rectangular air slot, and the front end face of the second rectangular air slot is in contact with the front end face of the first rectangular air slot. Located in the same plane, the right end face of the third rectangular air slot is aligned with the left end face of the first rectangular air slot, the rear end face of the third rectangular air slot is located in the same plane as the rear end face of the first rectangular air slot, the length of the first rectangular air slot in the front-to-back direction is less than the length of the fourth dielectric substrate in the front-to-back direction, the length of the second rectangular air slot in the left-to-right direction is equal to the length of the third rectangular air slot in the left-to-right direction, the sum of the length of the second rectangular air slot in the left-to-right direction and the length of the first rectangular air slot in the left-to-right direction is less than the length of the fourth dielectric substrate in the left-to-right direction, and the length of the second rectangular air slot in the front-to-back direction is less than the length of the first rectangular air slot in the front-to-back direction. the length of the third rectangular air slot in the front-to-back direction is less than half the length of the first rectangular air slot in the front-to-back direction; the sensing layer is formed by attaching a sensing material to all lower surfaces of the defective ground except the first rectangular air slot, the second rectangular air slot, and the third rectangular air slot; the front end surface of the sensing layer and the front end surface of the fourth dielectric substrate are located in the same plane, the rear end surface of the sensing layer and the rear end surface of the fourth dielectric substrate are located in the same plane, the left end surface of the sensing layer and the left end surface of the fourth dielectric substrate are located in the same plane, and the right end surface of the sensing layer and the right end surface of the fourth dielectric substrate are located in the same plane;The first rectangular air slot, the second rectangular air slot, and the third rectangular air slot form a U-shaped slot. The U-shaped slot can generate a resonance point within the sensing frequency band. When the sensing layer absorbs water, the electromagnetic properties will change, causing the resonance parameters of the resonance point generated by the U-shaped slot to change, thereby realizing the water pipe leakage detection function; the lengths of the first dielectric substrate, the third dielectric substrate, and the fourth dielectric substrate along the front-to-back direction are equal, the length of the second dielectric substrate along the front-to-back direction is less than the length of the first dielectric substrate along the front-to-back direction, and the first dielectric substrate, the third dielectric substrate, the fourth dielectric substrate, and the The second dielectric substrates are connected sequentially from left to right. The rear end surface of the first dielectric substrate, the rear end surface of the third dielectric substrate, the rear end surface of the fourth dielectric substrate, and the rear end surface of the second dielectric substrate are located in the same plane. The right end surface of the first dielectric substrate is aligned with the left end surface of the third dielectric substrate. The right end surface of the third dielectric substrate is aligned with the left end surface of the fourth dielectric substrate. The right end surface of the fourth dielectric substrate is aligned with the left end surface of the second dielectric substrate. The first, third, fourth, and second dielectric substrates can be spliced ​​or integrally formed. In this structure, the first and second RF transceivers are each implemented using a planar monopole antenna structure, which facilitates achieving a wide bandwidth and can be realized using only microstrip lines. This makes it suitable for printing processes and has low process costs. The encoding module is implemented using a λ / 4 open-circuit branch line. Microstrip theory allows for direct calculation of the required length of each rectangular microstrip resonator, facilitating circuit design for the encoding module. The sensing module is implemented using a defective ground structure, which is highly sensitive to sensing materials attached to the bottom surface. Furthermore, the U-shaped slot resonant structure (first, second, and third rectangular air slots) used to generate resonant points within the sensing frequency band can be implemented by etching a pattern on the ninth rectangular metal block. This ensures that when a water pipe leaks, it only affects the resonant points within the sensing frequency band, without affecting the resonant points within the encoding frequency band. This ensures the accuracy of the encoding and sensing information, further improving detection accuracy.

[0008] The length of the first dielectric substrate in the left-right direction is 30 mm, the length of the first dielectric substrate in the front-to-back direction is 40 mm, the length of the right angle side of the first triangular metal block in the left-right direction is 8 mm, and the length of the other right angle side of the first triangular metal block in the front-to-back direction is 10 mm; the length of the first rectangular metal block in the left-right direction is 16 mm, and the length of the first rectangular metal block in the front-to-back direction is 7 mm; the length of the second rectangular metal block in the left-right direction is 4 mm, and the length of the second rectangular metal block in the front-to-back direction is 5.5 mm; the length of the third rectangular metal block in the front-to-back direction is 4 mm, and the length of the third rectangular metal block in the front-to-back direction is 4 mm. The length of the metal block in the left-right direction is 6 mm; the length of the fourth rectangular metal block in the front-to-back direction is 9 mm, and the length of the fourth rectangular metal block in the left-to-right direction is 11 mm; the length of the first rectangular metal block in the front-to-back direction is 15 mm, and the length of the first rectangular metal block in the left-to-right direction is 30 mm; the distance between the rear end face of the third rectangular metal block and the rear end face of the first dielectric substrate is 6 mm; the length of the second dielectric substrate in the left-to-right direction is 35 mm, and the length of the second dielectric substrate in the front-to-back direction is 30 mm; the length of the other right-angled side of the third triangular metal block in the left-to-right direction is 10 mm, and the length of the third triangular metal block in the left-to-right direction is 10 mm. The length of the right angle side of the rectangular metal block in the front-to-back direction is 8mm; the length of the fifth rectangular metal block in the front-to-back direction is 16mm, and the length of the fifth rectangular metal block in the left-to-right direction is 7mm; the length of the sixth rectangular metal block in the front-to-back direction is 4mm, and the length in the left-to-right direction is 5.5mm; the length of the seventh rectangular metal block in the front-to-back direction is 6mm, and the length in the left-to-right direction is 9mm; the length of the second rectangular metal block in the left-to-right direction is 11mm, and the length in the front-to-back direction is 30mm; the length of the third dielectric substrate in the left-to-right direction is 35mm, and the length in the front-to-back direction is 40mm; the length of the fourth dielectric substrate is The length of the plate in the left-right direction is 35mm, and the length in the front-to-back direction is 40cm; the length of the first rectangular main transmission line in the left-right direction is 35mm, and the length in the front-to-back direction is 9mm; the length of the second rectangular main transmission line in the left-right direction is 35mm, and the length in the front-to-back direction is 9mm; the length of the first rectangular air slot in the front-to-back direction is 2.5mm, and the length in the left-right direction is 0.4mm; the length of the second rectangular air slot in the front-to-back direction is 0.4mm, and the length in the left-to-right direction is 13.6mm; the length of the third rectangular air slot in the front-to-back direction is 0.4mm, and the length in the left-to-right direction is 13.6mm.

[0009] The first dielectric substrate, the second dielectric substrate, the third dielectric substrate and the fourth dielectric substrate are all made of RF4, and the sensing material is a water-absorbing sponge.

[0010] Compared with the prior art, the advantage of the present invention is that an RFID sensor for water pipe leakage detection is formed by a first RF transceiver, a second RF transceiver, an encoding module and a sensing module. The output end of the first RF transceiver is connected to the input end of the encoding module, the output end of the encoding module is connected to the input end of the sensing module, and the output end of the sensing module is connected to the input end of the second RF transceiver. The input end of the first RF transceiver is used to access the RF signal. The RF signal is a broadband RF signal with a set frequency band. The frequency band of the broadband RF signal includes a coding frequency band and a sensing frequency band. The encoding module can load a data representing the RF signal within the coding frequency band of the RF signal. The ID sensor can receive the coded information of the identity information and send the radio frequency signal with the coded information to the sensor module. The sensor module can load the sensor information representing the current state of the water pipe obtained by the current detection within the sensing frequency band of the radio frequency signal with the number signal, and obtain the radio frequency signal with the coded information and the sensor information and send it to the second radio frequency transceiver. The output end of the second radio frequency transceiver is used to transmit the radio frequency signal with the coded information and the sensor information to the free space and be received by the terminal processing system. When used for water pipe leakage detection, the sensor module is arranged under the detected water pipe and in contact with the detected water pipe. The sensor module detects the detected water pipe in real time. The current state of the water pipe is detected and the sensing information representing the current state of the water pipe is generated. When the first RF transceiver receives the RF signal, the first RF transceiver transmits the RF signal to the encoding module. The encoding module loads the encoding information representing the identity information of the RFID sensor within the encoding frequency band of the RF signal, obtains the RF signal with the encoding information and sends it to the sensing module. The sensing module loads the currently obtained sensing information within the sensing frequency band of the RF signal with the encoding information, obtains the RF signal with the encoding information and the sensing information and sends it to the second RF transceiver. The output end of the second RF transceiver transmits the RF signal with the encoding information and the sensing information to the second RF transceiver. The signal is transmitted to free space, and the terminal processing system can receive the radio frequency signal with coding information and sensor information, and determine the identity information of the RFID sensor according to the coding information in the radio frequency signal with coding information and sensor information, and determine the sensor information of the RFID sensor corresponding to the identity information whether the water pipe is leaking, thereby realizing water pipe leakage detection. Therefore, the present invention adopts a chipless RFID tag to replace the traditional semiconductor sensor, and is arranged under the water pipe as a sensing node to detect the status of the water pipe. In addition, under large-scale deployment, the cost is low, and no complicated connection lines are required between the terminal processing system, which has great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a structural diagram of the first radio frequency transceiver of the RFID sensor for water pipe leakage detection of the present invention

[0012] Figure 2This is a structural diagram of a second radio frequency receiver of an RFID sensor for detecting water pipe leakage according to the present invention;

[0013] FIG3( a ) is a top view of the encoding module and the sensing module of the RFID sensor for water pipe leakage detection according to the present invention;

[0014] FIG3( b ) is a bottom view of the encoding module and the sensing module of the RFID sensor for water pipe leakage detection according to the present invention;

[0015] FIG3( c ) is a side view of the encoding module and the sensing module of the RFID sensor for water pipe leakage detection according to the present invention;

[0016] FIG4( a ) is a top view of an RFID sensor for detecting water pipe leakage according to the present invention;

[0017] FIG4( b ) is a side view of the RFID sensor for detecting water pipe leakage according to the present invention;

[0018] Figure 5 This is a block diagram of the working system of the RFID sensor for water pipe leakage detection of the present invention;

[0019] Figure 6 The first radio frequency transceiver and the second radio frequency receiver of the RFID sensor for water pipe leakage detection of the present invention are S 11 Simulation curve graph;

[0020] Figure 7 The measured S value of the "1 1 1" coded information of the RFID sensor for water pipe leakage detection of the present invention under the conditions of water pipe leakage and no leakage 21 Curve comparison chart;

[0021] Figure 8 The "1 0 0" coding tag, the "1 1 1" coding tag and the "1 0 1" coding tag of the RFID sensor for water pipe leakage detection of the present invention are S 21 Curve comparison chart. DETAILED DESCRIPTION

[0022] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0023] Example: Figure 1As shown in Figure 4, an RFID sensor for water pipe leakage detection includes a first RF transceiver 1, a second RF transceiver 2, a coding module 3 and a sensing module 4. The output end of the first RF transceiver 1 is connected to the input end of the coding module 3, the output end of the coding module 3 is connected to the input end of the sensing module 4, and the output end of the sensing module 4 is connected to the input end of the second RF transceiver 2. The input end of the first RF transceiver 1 is used to access the RF signal. The RF signal is a broadband RF signal with a set frequency band. The frequency band of the broadband RF signal includes the coding frequency band and the sensing frequency band. The coding module 3 can load the coding information representing the identity information of the RFID sensor within the coding frequency band of the radio frequency signal, and send the radio frequency signal with the coding information to the sensor module 4. The sensor module 4 can load the sensing information representing the current state of the water pipe obtained by the current detection within the sensing frequency band of the radio frequency signal with the number signal, obtain the radio frequency signal with the coding information and the sensing information and send it to the second radio frequency transceiver 2. The output end of the second radio frequency transceiver 2 is used to transmit the radio frequency signal with the coding information and the sensing information to the free space to be received by the terminal processing system; when using During water pipe leak detection, the sensor module 4 is placed below the water pipe being detected and in contact with it. The sensor module 4 detects the current state of the water pipe in real time and generates sensor information representing the current state of the water pipe. When the first RF transceiver 1 receives the RF signal, it transmits the RF signal to the encoding module 3. The encoding module 3 loads the encoding information representing the identity information of the RFID sensor within the encoding frequency band of the RF signal, obtains an RF signal with the encoding information, and sends it to the sensor module 4. The sensor module 4 loads the currently obtained sensor information within the sensing frequency band of the RF signal with the encoding information, obtains an RF signal with the encoding information and sensor information, and sends it to the second RF transceiver 2. The output end of the second RF transceiver 2 transmits the RF signal with the encoding information and sensor information into free space. The terminal processing system can receive the RF signal with the encoding information and sensor information, and determine the identity information of the RFID sensor based on the encoding information in the RF signal with the encoding information and sensor information. The sensor information determines whether the water pipe at the RFID sensor with the corresponding identity information is leaking, thereby achieving water pipe leak detection.

[0024] In this embodiment, the first RF transceiver 1 includes a first dielectric substrate 5, a first radiating structure, a first feeding structure, and a first rectangular metal ground 6. The first dielectric substrate 5 is a rectangular plate. The first radiating structure includes a first triangular metal block 7, a second triangular metal block 8, and a first rectangular metal block 9. The first triangular metal block 7, the second triangular metal block 8, and the first rectangular metal block 9 are all attached to the upper surface of the first dielectric substrate 5. The front end surface of the first rectangular metal block 9 is parallel to the front end surface of the first dielectric substrate 5. The length of the first rectangular metal block 9 in the left-right direction is less than the length of the first dielectric substrate 5 in the left-right direction. The symmetry line of the first rectangular metal block 9 in the front-to-back direction coincides with the symmetry line of the first dielectric substrate 5 in the front-to-back direction. The first triangular metal block 7 and the second triangular metal block 8 are located in front of the first rectangular metal block 9, and the first triangular metal block 7 is located to the left of the second triangular metal block 8. The two are symmetrical. The end surface of one right-angled side of the first triangular metal block 7 and the end surface of one right-angled side of the second triangular metal block 8 are both in contact with the front end surface of the first rectangular metal block 9, and the end surface of the other right-angled side of the first triangular metal block 7 is aligned with the end surface of the first rectangular metal block 9. The left end face of the second triangular metal block 8 is located in the same plane, the end face where the other right-angled side of the second triangular metal block 8 is located is located in the same plane as the right end face of the first rectangular metal block 9, the sum of the length of the end face where one right-angled side of the first triangular metal block 7 is located in the left-right direction and the length of the end face where one right-angled side of the second triangular metal block 8 is located in the left-right direction is equal to the length of the first rectangular metal block 9 in the left-right direction, and the sum of the length of the end face where the other right-angled side of the first triangular metal block 7 is located in the front-to-back direction and the length of the first rectangular metal block 9 in the front-to-back direction is less than the length of the plane where the rear end face of the first rectangular metal block 9 is located and the length of the The distance between the front end surface of the dielectric substrate 5 and the plane where the first rectangular metal ground plane is located is: the first rectangular metal ground plane 6 is attached to the lower surface of the first dielectric substrate 5; the rear end surface of the first rectangular metal ground plane 6 and the rear end surface of the first dielectric substrate 5 are located in the same plane; the left end surface of the first rectangular metal ground plane 6 and the left end surface of the first dielectric substrate 5 are located in the same plane; the right end surface of the first rectangular metal ground plane 6 and the right end surface of the first dielectric substrate 5 are located in the same plane; and the distance from the front end surface of the first rectangular metal ground plane 6 to its rear end surface is less than the distance from the plane where the rear end surface of the first rectangular metal block 9 is located to the plane where the rear end surface of the first dielectric substrate 5 is located.The first feeding structure includes a second rectangular metal block 10, a third rectangular metal block 11 and a fourth rectangular metal block 12. The second rectangular metal block 10, the third rectangular metal block 11 and the fourth rectangular metal block 12 are all attached to the upper surface of the first dielectric substrate 5. The second rectangular metal block 10 is located on the rear side of the first rectangular metal block 9. The front end face of the second rectangular metal block 10 is in contact with the rear end face of the first rectangular metal block 9. The length of the second rectangular metal block 10 in the left-right direction is less than the length of the first rectangular metal block 9 in the left-right direction. The symmetry line of the second rectangular metal block 10 in the front-to-back direction coincides with the symmetry line of the first rectangular metal block 9 in the front-to-back direction. The metal block 11 is located on the rear side of the second rectangular metal block 10, the left end face of the third rectangular metal block 11 is flush with the left end face of the second rectangular metal block 10, the front end face of the third rectangular metal block 11 is in contact with the rear end face of the second rectangular metal block 10, the length of the third rectangular metal block 11 in the left-right direction is greater than the length of the second rectangular metal block 10 in the left-right direction, the fourth rectangular metal block 12 is located on the right side of the third rectangular metal block 11, the left end face of the fourth rectangular metal block 12 is in contact with the right end face of the third rectangular metal block 11, the length of the fourth rectangular metal block 12 in the front-to-back direction is greater than the length of the third rectangular metal block 11 in the front-to-back direction, the fourth rectangular metal block 12 The right end surface of the fourth rectangular metal block 12 is flush with the right end surface of the first dielectric substrate 5, the symmetry line of the fourth rectangular metal block 12 along the left-right direction coincides with the symmetry line of the third rectangular metal block 11 along the left-right direction, the rear end surface of the fourth rectangular metal block 12 is located in front of the rear end surface of the first dielectric substrate 5, and the plane where the front end surface of the fourth rectangular metal block 12 is located is located on the rear side of the plane where the front end surface of the first rectangular metal ground 6 is located; the second RF receiver includes a second dielectric substrate 13, a second radiating structure, a second feeding structure and a second rectangular metal ground 14, the second radiating structure includes a third triangular metal block 15, a fourth triangular metal block 16 and a fifth rectangular metal block 17, the third triangular The metal block 15, the fourth triangular metal block 16, and the fifth rectangular metal block 17 are all attached to the upper surface of the second dielectric substrate 13. The front end of the fifth rectangular metal block 17 is parallel to the front end of the second dielectric substrate 13. The length of the fifth rectangular metal block 17 along the front-to-back direction is shorter than the length of the second dielectric substrate 13 along the front-to-back direction. The symmetry line of the fifth rectangular metal block 17 along the left-to-right direction coincides with the symmetry line of the second dielectric substrate 13 along the left-to-right direction. The third triangular metal block 15 and the fourth triangular metal block 16 are located to the right of the fifth rectangular metal block 17. The third triangular metal block 15 is located in front of the fourth triangular metal block 16, and the two are symmetrical in front-to-back direction.The end face where one right-angled side of the third triangular metal block 15 and the end face where one right-angled side of the fourth triangular metal block 16 are located are both in contact with the right end face of the fifth rectangular metal block 17. The end face where the other right-angled side of the third triangular metal block 15 and the front end face of the fifth rectangular metal block 17 are located in the same plane. The end face where the other right-angled side of the fourth triangular metal block 16 and the rear end face of the fifth rectangular metal block 17 are located in the same plane. The sum of the length of the end face where one right-angled side of the third triangular metal block 15 and the length of the end face where one right-angled side of the fourth triangular metal block 16 along the front-to-back direction is equal to the length of the fifth rectangular metal block 17 along the front-to-back direction. The sum of the length of the end face of the other right-angled side of the fifth rectangular metal block 15 in the left-right direction and the length of the fifth rectangular metal block 17 in the left-right direction is less than the distance between the plane where the left end face of the fifth rectangular metal block 17 is located and the plane where the right end face of the second dielectric substrate 13 is located. The second rectangular metal ground 14 is attached to the lower surface of the second dielectric substrate 13. The left end face of the second rectangular metal ground 14 and the left end face of the second dielectric substrate 13 are located in the same plane. The front end face of the second rectangular metal ground 14 and the front end face of the second dielectric substrate 13 are located in the same plane. The rear end face of the second rectangular metal ground 14 and the rear end face of the second dielectric substrate 13 are located in the same plane. The distance from the left end face of the second rectangular metal ground 14 to its right end face is less than the distance between the left end face of the fifth rectangular metal block 17 and the plane where the right end face of the second dielectric substrate 13 is located. The distance from the plane where the left end face of the fifth rectangular metal block 17 is located to the plane where the left end face of the second dielectric substrate 13 is located; the second feeding structure includes a sixth rectangular metal block 18 and a seventh rectangular metal block 19, the sixth rectangular metal block 18 and the seventh rectangular metal block 19 are both attached to the upper surface of the second dielectric substrate 13, the sixth rectangular metal block 18 is located on the left side of the fifth rectangular metal block 17, the right end face of the sixth rectangular metal block 18 is in contact with the left end face of the fifth rectangular metal block 17, the length of the sixth rectangular metal block 18 along the front-to-back direction is less than the length of the fifth rectangular metal block 17 along the front-to-back direction, the seventh rectangular metal block 19 is located on the left side of the sixth rectangular metal block 18, and the left end face of the seventh rectangular metal block 19 is in contact with the left end face of the sixth rectangular metal block 18. The left end surfaces of the second dielectric substrate 13 are flush, the right end surface of the seventh rectangular metal block 19 is aligned with the left end surface of the sixth rectangular metal block 18, the length of the seventh rectangular metal block 19 in the front-to-back direction is greater than the length of the sixth rectangular metal block 18 in the front-to-back direction and less than the length of the fifth rectangular metal block 17 in the front-to-back direction, the symmetry line of the fifth rectangular metal block 17 in the left-to-right direction, the symmetry line of the sixth rectangular metal block 18 in the left-to-right direction, and the symmetry line of the seventh rectangular metal block 19 in the left-to-right direction coincide with each other, the rear end surface of the seventh rectangular metal block 19 is located in front of the rear end surface of the second dielectric substrate 13, and the plane on which the right end surface of the seventh rectangular metal block 19 lies is located to the left of the plane on which the right end surface of the second rectangular metal ground 14 lies.The coded information is binary coded data. The coding module 3 includes a third dielectric substrate 20, a first rectangular main transmission line 21, nm rectangular microstrip resonators 22, and a third rectangular metal ground 23. n is the number of bits of the coded information, m is the number of "0"s in the coded information, the coding frequency band is divided into nm frequency bands, and the nm rectangular microstrip resonators 22 correspond one-to-one to the nm frequency bands. Each rectangular microstrip resonator 22 can generate a resonance point in its corresponding frequency band. When the rectangular microstrip resonator 22 generates a resonance point, the code is "1", otherwise the code is "0". The third dielectric plate is a rectangular plate. The first rectangular main transmission line 21 is a metal transmission line attached to the upper surface of the third dielectric substrate 20. The plane where the front end surface of the first rectangular main transmission line 21 is located is parallel to the plane where the front end surface of the third dielectric substrate 20 is located. In a plane, the length of the first rectangular main transmission line 21 along the front-to-back direction is shorter than the length of the third dielectric substrate 20 along the front-to-back direction. The distance from the plane where the rear end face of the first rectangular main transmission line 21 is located to the plane where the rear end face of the third dielectric substrate 20 is located is equal to the distance from the plane where the rear end face of the fourth rectangular metal block 12 is located to the plane where the rear end face of the first dielectric substrate 5 is located. The distance from the plane where the front end face of the first rectangular main transmission line 21 is located to the plane where the front end face of the third dielectric substrate 20 is located is equal to the distance from the plane where the front end face of the fourth rectangular metal block 12 is located to the plane where the front end face of the first dielectric substrate 5 is located. The left end face of the first rectangular main transmission line 21 and the left end face of the third dielectric substrate 20 are located in the same plane, and the right end face of the first rectangular main transmission line 21 and the right end face of the third dielectric substrate 20 are located in the same plane.The nm rectangular microstrip resonators 22 are implemented using nm rectangular metal blocks. The nm rectangular microstrip resonators 22 are respectively attached to the upper surface of the third dielectric substrate 20. The nm rectangular resonators are located on the front side of the first rectangular main transmission line 21. The rear end faces of the nm rectangular microstrip resonators 22 are all in contact with the front end face of the first rectangular main transmission line 21. The nm rectangular microstrip resonators 22 are spaced apart in order from left to right. The lengths of the nm rectangular microstrip resonators 22 along the front-to-back direction increase from left to right, and the lengths of the nm rectangular microstrip resonators 22 along the front-to-back direction are all shorter than the distance from the plane where the front end face of the first rectangular main transmission line 21 is located to the third dielectric substrate. 20, the distance between the front end surface of the third dielectric substrate 20 and the plane where the left end surface of the rectangular microstrip resonator 22 is located is located on the right side of the left end surface of the third dielectric substrate 20, and the plane where the right end surface of the rectangular microstrip resonator 22 is located is located on the left side of the right end surface of the third dielectric substrate 20. The third rectangular metal ground 23 is attached to the lower surface of the third dielectric substrate 20, the rear end surface of the third rectangular metal ground 23 is located in the same plane as the rear end surface of the third dielectric substrate 20, the front end surface of the third rectangular metal ground 23 is located in the same plane as the front end surface of the third dielectric substrate 20, and the left end of the third rectangular metal ground 23 is located on the right side of the left end surface of the third dielectric substrate 20. The left end surface of the third dielectric substrate 20 is located in the same plane, and the right end surface of the third rectangular metal ground 23 is located in the same plane as the right end surface of the third dielectric substrate 20; the sensing module 4 includes a fourth dielectric substrate 24, a second rectangular main transmission line 25, a defect ground and a sensing layer 26, the fourth dielectric substrate 24 is a rectangular plate, the second rectangular main transmission line 25 is a metal transmission line attached to the upper surface of the fourth dielectric substrate 24, the front end surface of the second rectangular main transmission line 25 is parallel to the plane of the front end surface of the fourth dielectric substrate 24, the length of the second rectangular main transmission line 25 along the front-to-back direction is less than the length of the fourth dielectric plate along the front-to-back direction, and the second rectangular main transmission line 25 is smaller than the length of the fourth dielectric plate along the front-to-back direction. 5 to the plane where the rear end face of the fourth dielectric substrate 24 is located is equal to the distance between the plane where the rear end face of the first rectangular main transmission line 21 is located and the plane where the rear end face of the third dielectric substrate 20 is located. The distance between the plane where the front end face of the second rectangular main transmission line 25 is located and the plane where the front end face of the fourth dielectric substrate 24 is located is equal to the distance between the plane where the front end face of the first rectangular main transmission line 21 is located and the plane where the front end face of the third dielectric substrate 20 is located. The left end face of the second rectangular main transmission line 25 and the left end face of the fourth dielectric substrate 24 are located in the same plane, and the right end face of the second rectangular main transmission line 25 and the right end face of the fourth dielectric substrate 24 are located in the same plane.The defective surface is provided on the lower surface of the fourth dielectric substrate 24, and the defective surface includes a ninth rectangular metal block 27, a first rectangular air slot 28, a second rectangular air slot 29, and a third rectangular air slot 30 attached to the lower surface of the fourth dielectric substrate 24. The front end surface of the ninth rectangular metal block 27 and the front end surface of the fourth dielectric substrate 24 are located in the same plane, the rear end surface of the ninth rectangular metal block 27 and the rear end surface of the fourth dielectric substrate 24 are located in the same plane, the left end surface of the ninth rectangular metal block 27 and the left end surface of the fourth dielectric substrate 24 are located in the same plane, the right end surface of the ninth rectangular metal block 27 and the right end surface of the fourth dielectric substrate 24 are located in the same plane, the first rectangular air slot 28, the second rectangular air slot 29 The first and third rectangular air slots 28, 29, and 30 are respectively provided on the ninth rectangular metal block 27. The lower surface of the fourth dielectric substrate 24 is exposed at the first rectangular air slot 28, the second rectangular air slot 29, and the third rectangular air slot 30. The symmetry line of the first rectangular air slot 28 along the left-right direction coincides with the symmetry line of the second rectangular main transmission line 25 along the left-right direction. The second rectangular air slot 29 and the third rectangular air slot 30 are both located on the left side of the first rectangular air slot 28. The second rectangular air slot 29 is located in front of the third rectangular air slot 30. The right end face of the second rectangular air slot 29 is aligned with the left end face of the first rectangular air slot 28. The front end face of the second rectangular air slot 29 is aligned with the front end face of the first rectangular air slot 28. The surfaces of the third rectangular air slot 30 are located in the same plane, the right end surface of the third rectangular air slot 30 is aligned with the left end surface of the first rectangular air slot 28, the rear end surface of the third rectangular air slot 30 is located in the same plane as the rear end surface of the first rectangular air slot 28, the length of the first rectangular air slot 28 in the front-to-back direction is less than the length of the fourth dielectric substrate 24 in the front-to-back direction, the length of the second rectangular air slot 29 in the left-to-right direction is equal to the length of the third rectangular air slot 30 in the left-to-right direction, the sum of the length of the second rectangular air slot 29 in the left-to-right direction and the length of the first rectangular air slot 28 in the left-to-right direction is less than the length of the fourth dielectric substrate 24 in the left-to-right direction, and the length of the second rectangular air slot 29 in the front-to-back direction is less than the length of the first rectangular air slot 28 The third rectangular air slot 30 is half the length of the defect in the front-to-back direction, and the length of the third rectangular air slot 30 in the front-to-back direction is less than half the length of the first rectangular air slot 28 in the front-to-back direction. The sensing layer 26 is formed by attaching a sensing material to all lower surfaces of the defect except the first rectangular air slot 28, the second rectangular air slot 29, and the third rectangular air slot 30. The front end surface of the sensing layer 26 and the front end surface of the fourth dielectric substrate 24 are located in the same plane, the rear end surface of the sensing layer 26 and the rear end surface of the fourth dielectric substrate 24 are located in the same plane, the left end surface of the sensing layer 26 and the left end surface of the fourth dielectric substrate 24 are located in the same plane, and the right end surface of the sensing layer 26 and the right end surface of the fourth dielectric substrate 24 are located in the same plane.The first rectangular air slot 28, the second rectangular air slot 29, and the third rectangular air slot 30 form a U-shaped slot. The U-shaped slot can generate a resonance point within the sensing frequency band. When the sensing layer 26 absorbs water, the electromagnetic properties will change, causing the resonance parameters of the resonance point generated by the U-shaped slot to change, thereby realizing the water pipe leakage detection function; the lengths of the first dielectric substrate 5, the third dielectric substrate 20, and the fourth dielectric substrate 24 along the front-to-back direction are equal, the length of the second dielectric substrate 13 along the front-to-back direction is less than the length of the first dielectric substrate 5 along the front-to-back direction, and the first dielectric substrate 5, the third dielectric substrate 20, the fourth dielectric substrate 24 and the second dielectric substrate 24 are equal. The dielectric substrates 13 are connected sequentially from left to right. The rear end faces of the first dielectric substrate 5, the third dielectric substrate 20, the fourth dielectric substrate 24, and the second dielectric substrate 13 are located in the same plane. The right end face of the first dielectric substrate 5 is aligned with the left end face of the third dielectric substrate 20, the right end face of the third dielectric substrate 20 is aligned with the left end face of the fourth dielectric substrate 24, and the right end face of the fourth dielectric substrate 24 is aligned with the left end face of the second dielectric substrate 13. The first dielectric substrate 5, the third dielectric substrate 20, the fourth dielectric substrate 24, and the second dielectric substrate 13 can be spliced ​​or integrally formed.

[0025] In this embodiment, the length of the first dielectric substrate 5 in the left-right direction is 30 mm, and the length of the first dielectric substrate 5 in the front-to-back direction is 40 mm. The length of one right angle side of the first triangular metal block 7 in the left-right direction is 8 mm, and the length of the other right angle side of the first triangular metal block 7 in the front-to-back direction is 10 mm. The length of the first rectangular metal block 9 in the left-right direction is 16 mm, and the length of the first rectangular metal block 9 in the front-to-back direction is 7 mm. The length of the second rectangular metal block 10 in the left-right direction is 4 mm, and the length of the second rectangular metal block 10 in the front-to-back direction is 5.5 mm. The length of the third rectangular metal block 11 in the front-to-back direction is 4 mm, and the length of the third rectangular metal block 11 in the front-to-back direction is 4 mm. The length in the left-right direction is 6 mm; the length in the front-to-back direction of the fourth rectangular metal block 12 is 9 mm, and the length in the left-to-right direction of the fourth rectangular metal block 12 is 11 mm; the length in the front-to-back direction of the first rectangular metal ground 6 is 15 mm, and the length in the left-to-right direction of the first rectangular metal ground 6 is 30 mm; the distance between the rear end face of the third rectangular metal block 11 and the rear end face of the first dielectric substrate 5 is 6 mm; the length in the left-to-right direction of the second dielectric substrate 13 is 35 mm, and the length in the front-to-back direction of the second dielectric substrate 13 is 30 mm; the length in the left-to-right direction of the other right-angled side of the third triangular metal block 15 is 10 mm, and one side of the third triangular metal block 15 is 10 mm. The length of the right-angled side in the front-to-back direction is 8 mm; the length of the fifth rectangular metal block 17 in the front-to-back direction is 16 mm, and the length of the fifth rectangular metal block 17 in the left-to-right direction is 7 mm; the length of the sixth rectangular metal block 18 in the front-to-back direction is 4 mm, and the length in the left-to-right direction is 5.5 mm; the length of the seventh rectangular metal block 19 in the front-to-back direction is 6 mm, and the length in the left-to-right direction is 9 mm; the length of the second rectangular metal ground 14 in the left-to-right direction is 11 mm, and the length in the front-to-back direction is 30 mm; the length of the third dielectric substrate 20 in the left-to-right direction is 35 mm, and the length in the front-to-back direction is 40 mm; the length of the fourth dielectric substrate 24 in the left-to-right direction is The length along the front-to-back direction is 35 mm, and the length along the front-to-back direction is 40 cm; the length of the first rectangular main transmission line 21 along the left-to-right direction is 35 mm, and the length along the front-to-back direction is 9 mm; the length of the second rectangular main transmission line 25 along the left-to-right direction is 35 mm, and the length along the front-to-back direction is 9 mm; the length of the first rectangular air slot 28 along the front-to-back direction is 2.5 mm, and the length along the left-to-right direction is 0.4 mm; the length of the second rectangular air slot 29 along the front-to-back direction is 0.4 mm, and the length along the left-to-right direction is 13.6 mm; the length of the third rectangular air slot 30 along the front-to-back direction is 0.4 mm, and the length along the left-to-right direction is 13.6 mm.

[0026] In this embodiment, the materials of the first dielectric substrate 5 , the second dielectric substrate 13 , the third dielectric substrate 20 and the fourth dielectric substrate 24 are all RF4, and the sensing material is a water-absorbing sponge.

[0027] The working system block diagram of the RFID sensor for water pipe leakage detection of the present invention is as follows Figure 5 As shown. The specific working method of the RFID sensor for water pipe leakage detection of the present invention is as follows: the sensing layer of the RFID sensor for water pipe leakage detection of the present invention is arranged below the water pipe to be detected, and the sensing layer is attached to the water pipe to be detected. The first RF transceiver communicates with the transmitting antenna, continuously receives the RF signal transmitted by the transmitting antenna, and transmits the RF signal to the encoding module. The rectangular microstrip resonator at the encoding module generates a plurality of independent stop bands (resonance points) within the encoding frequency band of the RF signal to load the encoding information representing the identity information of the RFID sensor. Thereafter, the RF signal is transmitted to the sensing module to load the sensing information. The defective ground at the sensing module generates a stop band (i.e., a resonance point) within the sensing frequency band of the RF signal. If the water pipe is not broken, the sensing layer is not corroded by water molecules at this time, the electromagnetic properties remain unchanged, and the stop band still exists within the sensing frequency band. If the water pipe is broken at this time, the sensing layer is affected by water molecules, the electromagnetic properties change, and the stop band generated by the sensing module in the sensing frequency band disappears. Afterwards, the RF signal is transmitted to the second RF transceiver, and then sent to free space via the second RF transceiver. The receiving antenna receives and extracts the identity information and sensing information of the RFID sensor and sends it to the reader. The reader determines whether the detected water pipe is leaking, thereby realizing water leakage detection.

[0028] In this embodiment, the coding frequency band is set between 3.9 GHz and 6 GHz and is divided into three frequency bands: a first frequency band of 3.9 GHz to 4.6 GHz, a second frequency band of 4.6 GHz to 5.3 GHz, and a third frequency band of 5.3 GHz to 6 GHz. Three rectangular microstrip resonators are used, with left-to-right lengths of 0.3 mm, 0.46 mm, and 0.67 mm, respectively, and front-to-back lengths of 6.53 mm, 7.83 mm, and 9.11 mm, respectively. These resonators are capable of generating resonant frequencies near 5.65 GHz, 4.95 GHz, and 4.25 GHz, respectively. If a resonant frequency occurs within each of the first, second, and third frequency bands, the coded information is "111." If a resonant frequency occurs within each of the first and third frequency bands, and no resonant frequency occurs within the second frequency band, the coded information is "101." The sensing frequency band is set between 3GHz and 3.5GHz, with the resonance point generated by the defective ground near 3.25GHz. When the sensing layer absorbs water, its electromagnetic properties change, causing the resonance parameters of the resonance point generated by the defective ground structure to change, thus enabling water pipe leakage detection.

[0029] The first radio frequency transceiver and the second radio frequency receiver of the RFID sensor for water pipe leakage detection of the present invention are S 11 The simulation curve is as follows Figure 6 As shown, analysis Figure 6 It can be seen that the -10dB bandwidth range of the first RF transceiver and the second RF transceiver both covers 3GHz-6GHz. Therefore, for a 3GHz-6GHz broadband RF signal, the first RF transceiver can receive it and transmit it to the encoding module, and the second RF transceiver can send the broadband RF signal with coding information and sensing information into free space.

[0030] The measured S of the "1 1 1" coded information of the RFID sensor for water pipe leakage detection of the present invention under the conditions of water pipe leakage and no leakage 21 Curve comparison chart Figure 7 As shown, analysis Figure 7 It can be seen that: when the water pipe is not leaking, the sensing module generates a resonance point, there is a resonance point in the sensing frequency band, and there are three resonance points in the coding frequency band. When the water pipe is leaking, the resonance point in the sensing frequency band disappears, while the three resonance points in the coding frequency band do not change. This verifies that the RFID sensor of the present invention will not affect the coding function while realizing the sensing function.

[0031] The "1 0 0" coding label, "1 1 1" coding label and "1 0 1" coding label of the RFID sensor for water pipe leakage detection of the present invention are 21 Curve comparison chart Figure 8 As shown, analysis Figure 8 It can be seen that the "1 0 0" coding information generates a resonance point in the first frequency band, and no resonance point in the second and third frequency bands, realizing the "1 0 0" coding function; the "11 1" coding information generates a resonance point in the first frequency band, the second frequency band, and the third frequency band, realizing the "1 1 1" coding function; the "1 0 1" coding information generates a resonance point in the first frequency band and the third frequency band, and no resonance point in the second frequency band, realizing the "1 0 1" coding function, verifying that the RFID sensor of the present invention can meet different ID information storage requirements.

Claims

1. An RFID sensor for water pipe leakage detection, characterized in that The system comprises a first RF transceiver, a second RF transceiver, an encoding module and a sensing module, wherein the output end of the first RF transceiver is connected to the input end of the encoding module, the output end of the encoding module is connected to the input end of the sensing module, and the output end of the sensing module is connected to the input end of the second RF transceiver. The input end of the first RF transceiver is used to receive a RF signal, wherein the RF signal is a broadband RF signal of a set frequency band, and the frequency band of the broadband RF signal includes a coding frequency band and a sensing frequency band. The encoding module can load coding information representing the identity information of the RFID sensor within the coding frequency band of the RF signal and send the RF signal with coding information to the sensing module. The sensing module can load sensing information representing the current state of the water pipe obtained by current detection within the sensing frequency band of the RF signal with the numbering signal, obtain a RF signal with coding information and sensing information and send it to the second RF transceiver. The output end of the second RF transceiver is used to transmit the RF signal with coding information and sensing information to free space to be received by the terminal processing system. When used for water pipe leakage detection, the sensing module is arranged below the detected water pipe and in contact with the detected water pipe. The sensing module detects the current state of the detected water pipe in real time and generates sensing information representing the current state of the water pipe. When the first RF transceiver receives the RF signal, the first RF transceiver transmits the RF signal to the encoding module. The encoding module loads the encoding information representing the identity information of the RFID sensor within the encoding frequency band of the RF signal, obtains a RF signal with the encoding information, and sends it to the sensing module. The sensing module loads the currently obtained sensing information within the sensing frequency band of the RF signal with the encoding information, obtains a RF signal with the encoding information and sensing information, and sends it to the second RF transceiver. The output end of the second RF transceiver transmits the RF signal with the encoding information and sensing information into free space. The terminal processing system can receive the RF signal with the encoding information and sensing information, and determine the identity information of the RFID sensor based on the encoding information in the RF signal with the encoding information and sensing information. The sensing information determines whether the water pipe at the RFID sensor corresponding to the identity information is leaking, thereby realizing water pipe leakage detection. The sensing module includes a fourth dielectric substrate, a second rectangular main transmission line, a defective ground, and a sensing layer. The fourth dielectric substrate is a rectangular plate. The second rectangular main transmission line is a metal transmission line attached to the upper surface of the fourth dielectric substrate. The plane on which the front end surface of the second rectangular main transmission line lies is parallel to the plane on which the front end surface of the fourth dielectric substrate lies. The length of the second rectangular main transmission line in the front-to-back direction is less than the length of the fourth dielectric substrate in the front-to-back direction. The left end surface of the second rectangular main transmission line and the left end surface of the fourth dielectric substrate are located in the same plane. The right end surface of the second rectangular main transmission line and the right end surface of the fourth dielectric substrate are located in the same plane.The defective ground is arranged on the lower surface of the fourth dielectric substrate, and the defective ground includes a ninth rectangular metal block, a first rectangular air slot, a second rectangular air slot, and a third rectangular air slot attached to the lower surface of the fourth dielectric substrate. The front end surface of the ninth rectangular metal block and the front end surface of the fourth dielectric substrate are located in the same plane, the rear end surface of the ninth rectangular metal block and the rear end surface of the fourth dielectric substrate are located in the same plane, the left end surface of the ninth rectangular metal block and the left end surface of the fourth dielectric substrate are located in the same plane, the right end surface of the ninth rectangular metal block and the right end surface of the fourth dielectric substrate are located in the same plane, the first rectangular air slot, the second rectangular air slot, and the The third rectangular air slot is respectively opened on the ninth rectangular metal block, the lower surface of the fourth dielectric substrate is exposed at the first rectangular air slot, the second rectangular air slot and the third rectangular air slot, the symmetry line of the first rectangular air slot along the left-right direction coincides with the symmetry line of the second rectangular main transmission line along the left-right direction, the second rectangular air slot and the third rectangular air slot are both located on the left side of the first rectangular air slot, the second rectangular air slot is located in front of the third rectangular air slot, the right end face of the second rectangular air slot is in contact with the left end face of the first rectangular air slot, and the front end face of the second rectangular air slot is in contact with the front end face of the first rectangular air slot. Located in the same plane, the right end face of the third rectangular air slot is aligned with the left end face of the first rectangular air slot, the rear end face of the third rectangular air slot is located in the same plane as the rear end face of the first rectangular air slot, the length of the first rectangular air slot along the front-to-back direction is less than the length of the fourth dielectric substrate along the front-to-back direction, the length of the second rectangular air slot along the left-to-right direction is equal to the length of the third rectangular air slot along the left-to-right direction, the sum of the length of the second rectangular air slot along the left-to-right direction and the length of the first rectangular air slot along the left-to-right direction is less than the length of the fourth dielectric substrate along the left-to-right direction, and the length of the second rectangular air slot along the front-to-back direction is less than the length of the first rectangular air slot along the front-to-back direction half of the length in the front-to-back direction of the third rectangular air slot, the length of the third rectangular air slot in the front-to-back direction is less than half of the length of the first rectangular air slot in the front-to-back direction; the sensing layer is formed by attaching a sensing material to all lower surfaces of the defective ground except the first rectangular air slot, the second rectangular air slot, and the third rectangular air slot; the front end surface of the sensing layer and the front end surface of the fourth dielectric substrate are located in the same plane, the rear end surface of the sensing layer and the rear end surface of the fourth dielectric substrate are located in the same plane, the left end surface of the sensing layer and the left end surface of the fourth dielectric substrate are located in the same plane, and the right end surface of the sensing layer and the right end surface of the fourth dielectric substrate are located in the same plane;The first, second, and third rectangular air slots form a U-shaped slot. The U-shaped slot can generate a resonance point within the sensing frequency band. When the sensing layer absorbs water, its electromagnetic properties change, causing the resonance parameters of the resonance point generated by the U-shaped slot to change, thereby realizing the water pipe leakage detection function.

2. The RFID sensor for water pipe leakage detection according to claim 1 is characterized in that The first RF transceiver includes a first dielectric substrate, a first radiating structure, a first feeding structure and a first rectangular metal ground. The first dielectric substrate is a rectangular plate. The first radiating structure includes a first triangular metal block, a second triangular metal block and a first rectangular metal block. The first triangular metal block, the second triangular metal block and the first rectangular metal block are all attached to the upper surface of the first dielectric substrate. The front end face of the first rectangular metal block is parallel to the front end face of the first dielectric substrate. The length of the first rectangular metal block in the left-right direction is less than the length of the first dielectric substrate in the left-right direction. The symmetry line of the first rectangular metal block in the front-back direction coincides with the symmetry line of the first dielectric substrate in the front-back direction. The first triangular metal block and the second triangular metal block are located in front of the first rectangular metal block, and the first triangular metal block is located on the left side of the second triangular metal block and the two are symmetrical. The end face where one right-angled side of the first triangular metal block is located and the end face where one right-angled side of the second triangular metal block is located are both in contact with the front end face of the first rectangular metal block, and the end face where the other right-angled side of the first triangular metal block is in contact with the left side of the first rectangular metal block. The end faces are located in the same plane, the end face where the other right-angled side of the second triangular metal block is located is located in the same plane as the right end face of the first rectangular metal block, the sum of the length of the end face where one right-angled side of the first triangular metal block is located in the left-right direction and the length of the end face where one right-angled side of the second triangular metal block is located in the left-right direction is equal to the length of the first rectangular metal block in the left-right direction, and the sum of the length of the end face where the other right-angled side of the first triangular metal block is located in the front-to-back direction and the length of the first rectangular metal block in the front-to-back direction is less than the length between the plane where the rear end face of the first rectangular metal block is located and the plane where the first inter the distance between the plane where the front end surface of the first rectangular metal block is located and the plane where the front end surface of the dielectric substrate is located, the first rectangular metal ground is attached to the lower surface of the first dielectric substrate, the rear end surface of the first rectangular metal ground is located in the same plane as the rear end surface of the first dielectric substrate, the left end surface of the first rectangular metal ground is located in the same plane as the left end surface of the first dielectric substrate, and the right end surface of the first rectangular metal ground is located in the same plane as the right end surface of the first dielectric substrate, and the distance from the front end surface of the first rectangular metal ground to its rear end surface is smaller than the distance from the plane where the rear end surface of the first rectangular metal block is located to the plane where the rear end surface of the first dielectric substrate is located;The first feeding structure includes a second rectangular metal block, a third rectangular metal block and a fourth rectangular metal block. The second rectangular metal block, the third rectangular metal block and the fourth rectangular metal block are all attached to the upper surface of the first dielectric substrate. The second rectangular metal block is located at the rear side of the first rectangular metal block. The front end face of the second rectangular metal block is in contact with the rear end face of the first rectangular metal block. The length of the second rectangular metal block in the left-right direction is less than the length of the first rectangular metal block in the left-right direction. The symmetry line of the second rectangular metal block in the front-back direction coincides with the symmetry line of the first rectangular metal block in the front-back direction. The third rectangular metal block is located at the rear side of the second rectangular metal block. The left end face of the third rectangular metal block is flush with the left end face of the second rectangular metal block. The front end face of the third rectangular metal block is in contact with the the rear end face of the second rectangular metal block is in contact with the rear end face of the second rectangular metal block, the length of the third rectangular metal block in the left-right direction is greater than the length of the second rectangular metal block in the left-right direction, the fourth rectangular metal block is located on the right side of the third rectangular metal block, the left end face of the fourth rectangular metal block is in contact with the right end face of the third rectangular metal block, the length of the fourth rectangular metal block in the front-back direction is greater than the length of the third rectangular metal block in the front-back direction, the right end face of the fourth rectangular metal block is flush with the right end face of the first dielectric substrate, the symmetry line of the fourth rectangular metal block in the left-right direction coincides with the symmetry line of the third rectangular metal block in the left-right direction, the rear end face of the fourth rectangular metal block is located in front of the rear end face of the first dielectric substrate, and the plane where the front end face of the fourth rectangular metal block is located is located behind the plane where the front end face of the first rectangular metal substrate is located; The second RF transceiver includes a second dielectric substrate, a second radiating structure, a second feeding structure, and a second rectangular metal ground. The second radiating structure includes a third triangular metal block, a fourth triangular metal block, and a fifth rectangular metal block. The third triangular metal block, the fourth triangular metal block, and the fifth rectangular metal block are all attached to the upper surface of the second dielectric substrate. The front end face of the fifth rectangular metal block is parallel to the front end face of the second dielectric substrate. The length of the fifth rectangular metal block in the front-to-back direction is less than the length of the second dielectric substrate in the front-to-back direction. The symmetry line of the fifth rectangular metal block in the left-to-right direction coincides with the symmetry line of the second dielectric substrate in the left-to-right direction. The third triangular metal block and the fourth triangular metal block are located on the right side of the fifth rectangular metal block. The third triangular metal block is located in front of the fourth triangular metal block and the two are symmetrical in front and back. The end face of one right-angled side of the third triangular metal block and the end face of one right-angled side of the fourth triangular metal block are both in contact with the right end face of the fifth rectangular metal block. The end face of the other right-angled side of the third triangular metal block is located on the same plane as the front end face of the fifth rectangular metal block. The end face where the other right-angled side of the fourth triangular metal block is located is located in the same plane as the rear end face of the fifth rectangular metal block. The sum of the length of the end face where one right-angled side of the third triangular metal block is located in the front-to-back direction and the length of the end face where one right-angled side of the fourth triangular metal block is located in the front-to-back direction is equal to the length of the fifth rectangular metal block in the front-to-back direction. The sum of the length of the end face where the other right-angled side of the third triangular metal block is located in the left-to-right direction and the length of the fifth rectangular metal block in the left-to-right direction is less than the length between the plane where the left end face of the fifth rectangular metal block is located and the second dielectric substrate. the distance between the plane where the right end face of the second rectangular metal ground is located, the second rectangular metal ground is attached to the lower surface of the second dielectric substrate, the left end face of the second rectangular metal ground is in the same plane as the left end face of the second dielectric substrate, the front end face of the second rectangular metal ground is in the same plane as the front end face of the second dielectric substrate, the rear end face of the second rectangular metal ground is in the same plane as the rear end face of the second dielectric substrate, and the distance from the left end face of the second rectangular metal ground to its right end face is less than the distance from the plane where the left end face of the fifth rectangular metal block is located to the plane where the left end face of the second dielectric substrate is located;The second feeding structure includes a sixth rectangular metal block and a seventh rectangular metal block, wherein the sixth rectangular metal block and the seventh rectangular metal block are both attached to the upper surface of the second dielectric substrate, the sixth rectangular metal block is located on the left side of the fifth rectangular metal block, the right end face of the sixth rectangular metal block is aligned with the left end face of the fifth rectangular metal block, the length of the sixth rectangular metal block in the front-to-back direction is less than the length of the fifth rectangular metal block in the front-to-back direction, the seventh rectangular metal block is located on the left side of the sixth rectangular metal block, the left end face of the seventh rectangular metal block is flush with the left end face of the second dielectric substrate, and the sixth rectangular metal block is located on the left side of the sixth rectangular metal block. The right end face of the seventh rectangular metal block is aligned with the left end face of the sixth rectangular metal block. The length of the seventh rectangular metal block in the front-to-back direction is greater than the length of the sixth rectangular metal block in the front-to-back direction and less than the length of the fifth rectangular metal block in the front-to-back direction. The symmetry lines of the fifth rectangular metal block in the left-to-right direction, the symmetry lines of the sixth rectangular metal block in the left-to-right direction, and the symmetry lines of the seventh rectangular metal block in the left-to-right direction coincide with each other. The rear end face of the seventh rectangular metal block is located in front of the rear end face of the second dielectric substrate. The plane on which the right end face of the seventh rectangular metal block lies is located to the left of the plane on which the right end face of the second rectangular metal substrate lies. The coding information is binary coded data, and the coding module includes a third dielectric substrate, a first rectangular main transmission line, nm A rectangular microstrip resonator and a third rectangular metal ground, where n is the number of bits of the coded information, m is the number of "0" in the coded information, and the coded frequency band is divided into nm frequency bands, nm A rectangular microstrip resonator and nm frequency bands, each rectangular microstrip resonator can generate a resonance point in its corresponding frequency band; when the rectangular microstrip resonator generates a resonance point, it is coded as "1", otherwise it is coded as "0"; the third dielectric substrate is a rectangular plate; the first rectangular main transmission line is a metal transmission line attached to the upper surface of the third dielectric substrate; the plane where the front end face of the first rectangular main transmission line is located is parallel to the plane where the front end face of the third dielectric substrate is located; the length of the first rectangular main transmission line in the front-to-back direction is less than the length of the third dielectric substrate in the front-to-back direction; the plane where the rear end face of the first rectangular main transmission line is located is parallel to the plane where the front end face of the third dielectric substrate is located; The distance between the plane where the rear end face of the third dielectric substrate is located is equal to the distance between the plane where the rear end face of the fourth rectangular metal block is located and the plane where the rear end face of the first dielectric substrate is located. The distance between the plane where the front end face of the first rectangular main transmission line is located and the plane where the front end face of the third dielectric substrate is located is equal to the distance between the plane where the front end face of the fourth rectangular metal block is located and the plane where the front end face of the first dielectric substrate is located. The left end face of the first rectangular main transmission line and the left end face of the third dielectric substrate are located in the same plane. The right end face of the first rectangular main transmission line and the right end face of the third dielectric substrate are located in the same plane. nm A rectangular microstrip resonator is used nm A rectangular metal block is implemented, nm The rectangular microstrip resonators are respectively attached to the upper surface of the third dielectric substrate. nm A rectangular resonator is located on the front side of the first rectangular main transmission line, nm The rear end faces of the rectangular resonators are all in contact with the front end face of the first rectangular main transmission line. nm The rectangular resonators are spaced from left to right. nm The length of the rectangular resonator along the front-to-back direction increases from left to right, and the nm The length of each rectangular resonator along the front-to-back direction is smaller than the distance from the plane where the front end surface of the first rectangular main transmission line is located to the plane where the front end surface of the third dielectric substrate is located. nm Among the rectangular resonators, the plane where the left end face of the leftmost rectangular resonator lies is located to the right of the left end face of the third dielectric substrate, and the plane where the right end face of the rightmost rectangular resonator lies is located to the left of the right end face of the third dielectric substrate. The third rectangular metal ground is attached to the lower surface of the third dielectric substrate. The rear end face of the third rectangular metal ground is located in the same plane as the rear end face of the third dielectric substrate. The front end face of the third rectangular metal ground is located in the same plane as the front end face of the third dielectric substrate. The left end face of the third rectangular metal ground is located in the same plane as the left end face of the third dielectric substrate. The right end face of the third rectangular metal ground is located in the same plane as the right end face of the third dielectric substrate. The distance between the plane where the rear end face of the second rectangular main transmission line is located and the plane where the rear end face of the fourth dielectric substrate is located is equal to the distance between the plane where the rear end face of the first rectangular main transmission line is located and the plane where the rear end face of the third dielectric substrate is located. The distance between the plane where the front end face of the second rectangular main transmission line is located and the plane where the front end face of the fourth dielectric substrate is located is equal to the distance between the plane where the front end face of the first rectangular main transmission line is located and the plane where the front end face of the third dielectric substrate is located. The first, third, and fourth dielectric substrates have equal lengths in the front-to-back direction, and the second dielectric substrate has a shorter length in the front-to-back direction than the first dielectric substrate. The first, third, fourth, and second dielectric substrates are connected sequentially from left to right. The rear end faces of the first, third, and fourth dielectric substrates are located in the same plane as the rear end face of the second dielectric substrate. The right end face of the first dielectric substrate is aligned with the left end face of the third dielectric substrate, the right end face of the third dielectric substrate is aligned with the left end face of the fourth dielectric substrate, and the right end face of the fourth dielectric substrate is aligned with the left end face of the second dielectric substrate. The first, third, fourth, and second dielectric substrates can be spliced ​​or integrally formed.

3. The RFID sensor for water pipe leakage detection according to claim 2, characterized in that The first dielectric substrate has a length of 30 mm in the left-right direction and a length of 40 mm in the front-to-back direction. The right angle of the first triangular metal block has a length of 8 mm in the left-right direction, and the other right angle of the first triangular metal block has a length of 10 mm in the front-to-back direction. The first rectangular metal block has a length of 16 mm in the left-right direction and a length of 7 mm in the front-to-back direction. The second rectangular metal block has a length of 4 mm in the left-right direction and a length of 5.5 mm in the front-to-back direction. The third rectangular metal block has a length of 4 mm in the front-to-back direction and a length of 6 mm in the left-to-right direction. The fourth rectangular metal block has a length of 9 mm in the front-to-back direction and a length of 11 mm in the left-to-right direction. The first rectangular metal floor has a length of 15 mm in the front-to-back direction and a length of 30 mm in the left-to-right direction. The distance between the rear end face of the third rectangular metal block and the rear end face of the first dielectric substrate is 6 mm; the length of the second dielectric substrate in the left-right direction is 35 mm, the length of the second dielectric substrate in the front-to-back direction is 30 mm, the length of the other right-angled side of the third triangular metal block in the left-to-right direction is 10 mm, and the length of the right-angled side of the third triangular metal block in the front-to-back direction is 8 mm; the length of the fifth rectangular metal block in the front-to-back direction is 16 mm, and the length of the fifth rectangular metal block in the left-to-right direction is 7 mm; the length of the sixth rectangular metal block in the front-to-back direction is 4 mm, and the length in the left-to-right direction is 5.5 mm; the length of the seventh rectangular metal block in the front-to-back direction is 6 mm, and the length in the left-to-right direction is 9 mm; the length of the second rectangular metal block in the left-to-right direction is 11 mm m, and its length along the front-to-back direction is 30mm; the length of the third dielectric substrate along the left-right direction is 35mm, and its length along the front-to-back direction is 40mm; the length of the fourth dielectric substrate along the left-right direction is 35mm, and its length along the front-to-back direction is 40cm; the length of the first rectangular main transmission line along the left-right direction is 35mm, and its length along the front-to-back direction is 9mm; the length of the second rectangular main transmission line along the left-right direction is 35mm, and its length along the front-to-back direction is 9mm; the length of the first rectangular air slot along the front-to-back direction is 2.5mm, and its length along the left-to-right direction is 0.4mm; the length of the second rectangular air slot along the front-to-back direction is 0.4mm, and its length along the left-to-right direction is 13.6mm; the length of the third rectangular air slot along the front-to-back direction is 0.4mm, and its length along the left-to-right direction is 13.6mm.

4. The RFID sensor for water pipe leakage detection according to claim 2, characterized in that The first dielectric substrate, the second dielectric substrate, the third dielectric substrate and the fourth dielectric substrate are all made of RF4, and the sensing material is a water-absorbing sponge.

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