Passive temperature alarm device and antenna design method

Abstract

The invention discloses a passive temperature alarm device and an antenna design method.The passive temperature alarm device comprises a receiving antenna, a conductive material, a temperature bidirectional memory material and a shell, the receiving antenna is arranged on one side of the shell, an antenna chip is arranged in the receiving antenna, and the temperature bidirectional memory material is arranged in the shell; the impedance of the antenna chip is designed to be matched with the impedance generated in the working process of the receiving antenna; the temperature bidirectional memory material is arranged on the other side of the shell, a conductive material is attached to the deformation end of the temperature bidirectional memory material, and the temperature bidirectional memory material is made of a shape memory material. According to the passive temperature alarm device provided by the invention, the optimal working frequency of the receiving antenna is changed by using the thermal mechanical characteristics of the temperature bidirectional memory material and the influence of the conductive material on the receiving antenna, and the passive temperature alarm capable of being repeatedly detected is realized.

Description

Technical Field

[0001] This application relates to the fields of antenna design and passive wireless sensing technology, and in particular, to a passive temperature alarm device and an antenna design method. Background Art

[0002] There are many electrical devices in the power system, and the normal operation of these electrical devices ensures the stable operation of the power system. However, these electrical devices often experience failures caused by overheating, resulting in their inability to work properly, and even causing fires in severe cases. Therefore, temperature monitoring of equipment can timely detect equipment failures, prevent the further expansion of failures, improve the service life of equipment, and ensure the stability and reliability of equipment operation.

[0003] In the existing sensor device temperature measurement systems, only single irreversible alarm can be achieved, and they cannot be reused. Take some sensor device temperature measurement systems using shape memory alloy as an example. The shape memory alloy will change its shape when the temperature reaches a specific threshold, thereby triggering the alarm mechanism. However, this shape change is often irreversible. Once the alloy deforms and triggers the alarm, it cannot return to its initial state and cannot be used again to detect temperature changes and send alarm signals.

[0004] Therefore, it has become an urgent technical problem for those skilled in the art to improve the existing temperature alarm system to improve the reusability of temperature detection. Summary of the Invention

[0005] This application provides a passive temperature alarm system to solve the technical problem of how to improve the existing temperature alarm system, so as to achieve passive temperature alarm with repeatable detection.

[0006] To solve the above technical problem, an embodiment of this application provides a passive temperature alarm device, including: a receiving antenna, a conductive material, a temperature bi-directional memory material, and a housing. Among them, The receiving antenna is arranged on one side of the housing, and an antenna chip is built in the receiving antenna. The impedance of the antenna chip is designed to match the impedance generated by the receiving antenna during operation; The temperature bi-directional memory material is arranged on the other side of the housing, and a conductive material is attached to the deformation end of the temperature bi-directional memory material. The temperature bi-directional memory material is composed of a shape memory material.

[0007] As one of the preferred solutions, the receiving antenna includes an embedded T-shaped matching antenna.

[0008] As one of the preferred solutions, the temperature bi-directional memory material includes, but is not limited to, crosslinked cyclooctene and polyurethane.

[0009] As one of the preferred solutions, the passive temperature alarm device further includes a signal transceiver, which is communicatively connected to the receiving antenna. The signal transceiver is configured to transmit energy to activate the receiving antenna, then receive the reflected signal of the receiving antenna, and sense the temperature change in the reflected signal.

[0010] Another embodiment of the present application provides an antenna design method, which is applied to the passive temperature alarm device as described above, and includes: Input the pre-constructed set of structural dimension parameters of the receiving antenna and the first distance between the receiving antenna and the conductive material obtained into an electromagnetic simulation model for calculation to obtain the first set of impedance parameters of the receiving antenna; Calculate the splitting factor according to the obtained chip impedance parameters of the antenna chip and the first set of impedance parameters, where the splitting factor is used to quantify the impedance matching degree between the receiving antenna and the antenna chip; Construct a function graph of the splitting factor varying with the structural dimension parameters according to the first set of impedance parameters and the splitting factor, and screen the first set of structural dimension parameters of the receiving antenna that meet the feasibility constraints according to the function graph; Input the second distance between the receiving antenna and the conductive material after the temperature bidirectional memory material is deformed at high temperature and the set of structural dimension parameters obtained into the electromagnetic simulation model for calculation to obtain the second set of impedance parameters of the receiving antenna; Screen the first set of structural dimension parameters according to the first set of impedance parameters and the second set of impedance parameters to obtain the target structural dimension parameters of the receiving antenna.

[0011] As one of the preferred solutions, the splitting factor is expressed as: Or Wherein, is the splitting factor, is the receiving antenna resistance, is the receiving antenna reactance, is the antenna chip resistance, is the antenna chip reactance, is the slot width of the receiving antenna, is the slot height of the receiving antenna, is the slot thickness of the receiving antenna, is the width of the receiving antenna.

[0012] As one of the preferred solutions, constructing a function graph of the splitting factor varying with the structural size parameters according to the first impedance parameter set and the splitting factor, and screening the first set of structural size parameters of the receiving antenna that meet the feasibility constraints according to the function graph, includes: Taking the structural size parameters as the independent variable and the splitting factor as the dependent variable, and constructing a function graph of the splitting factor varying with the structural size parameters by using the curve fitting method; Determining the feasibility constraints of the receiving antenna, where the feasibility constraints include the processing accuracy limitations of the structural size parameters, the availability and cost limitations of the materials, and the space limitations of the overall size of the receiving antenna; Marking the area that meets the feasibility constraints on the function graph, and screening out the structural size parameters located in the area from the set of structural size parameters to generate the first set of structural size parameters of the receiving antenna.

[0013] As one of the preferred solutions, the first distance includes the distance between the receiving antenna and the conductive material when the temperature bistable memory material is at room temperature; the second distance includes the distance between the receiving antenna and the conductive material when the temperature bistable memory material deforms at high temperature; Before inputting the second distance between the receiving antenna and the conductive material after the high-temperature deformation of the obtained temperature bistable memory material and the set of structural size parameters into the electromagnetic simulation model for calculation, it further includes: Testing the high-temperature deformation characteristics of the temperature bistable memory material, and determining the second distance according to the test results; Inputting the second distance and the set of structural size parameters into the electromagnetic simulation model, and resetting the boundary conditions and calculation parameters of the simulation model.

[0014] As one of the preferred solutions, screening the set of structural size parameters according to the first impedance parameter and the second impedance parameter to obtain the target structural size parameters of the receiving antenna, includes: According to the first impedance parameter set and the second impedance parameter set, respectively calculating the power transfer efficiency of each structural size parameter in the first set of structural size parameters at the first distance and the second distance; Preliminarily screening the first set of structural size parameters according to the power transfer efficiency to obtain a first screening result; Respectively calculating the frequency response characteristics of each structural size parameter in the first screening result at the first distance and the second distance; Perform secondary screening on the first screening result according to the frequency response characteristic to obtain the target structural dimension parameter of the receiving antenna.

[0015] As one of the preferred solutions, the power transfer efficiency is expressed as: Wherein, is the power transfer efficiency in the matching state, is the resistance of the receiving antenna, is the reactance of the receiving antenna, is the resistance of the antenna chip, is the reactance of the antenna chip.

[0016] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following: (1) The temperature bidirectional memory material designed in the present application enables the receiving antenna to assist in memorizing and storing events beyond the threshold temperature. At the same time, it can maintain different forms above and below the threshold temperature and can change its own shape in real time according to the temperature. Moreover, this change is not a one-time occurrence and can be changed repeatedly. The change in the receiving antenna signal caused thereby can help the staff quickly detect faults.

[0017] (2) The present application adopts a frequency modulation strategy to implement a passive temperature alarm system. This method can change the optimal operating frequency of the receiving antenna when a temperature change is detected, thereby realizing the temperature alarm function. Applying this method, compared with other passive temperature sensors using amplitude modulation strategies, etc., it is not necessary to set up multiple receiving antennas and measure them. Therefore, the sensor volume can be further reduced, and the cost can be lowered at the same time. Moreover, since the change in the threshold transmission power provided to the chip due to the change in the reading distance is very slight and is hardly affected by the channel fading caused by the multipath effect, the reading range of the passive temperature alarm system can be larger, making the application range wider and the application more convenient and effective.

[0018] (3) The impedance matching method for the T-shaped antenna design proposed in the present application can serve a passive temperature alarm system based on frequency modulation and ensure the effective operation of the system. Using a compliant antenna is the basic guarantee for the effective implementation of the frequency modulation method. Description of the Drawings

[0019] Figure 1 is a schematic structural diagram of a passive temperature alarm device in one of the embodiments of the present application; Figure 2 is a stable state diagram of a passive temperature alarm system in one of the embodiments of the present application when the temperature is lower than T; Figure 3It is the transient diagram of the passive temperature alarm system in one embodiment of the present application when the temperature is higher than T; Figure 4 It is the steady-state diagram of the passive temperature alarm system in one embodiment of the present application when the temperature is higher than T; Figure 5 It is the transient diagram of the passive temperature alarm system in one embodiment of the present application when the temperature is lower than T; Figure 6 It is the schematic flowchart of the antenna design method in one embodiment of the present application; Figure 7 It is the parameter schematic diagram of the receiving antenna design in one embodiment of the present application; Figure 8 It is the function diagram of the splitting factor varying with the antenna length and width in the antenna design in one embodiment of the present application; Figure 9 It is in the antenna design in one embodiment of the present application where the distance is the function diagram of the power transfer efficiency varying with the frequency; Figure 10 It is in the antenna design in one embodiment of the present application where the distance is the function diagram of the power transfer efficiency varying with the frequency.

[0020] Reference numerals: Among them, 1. Outer shell; 2. Temperature bistable memory material; 3. Receiving antenna; 4. Conductive material. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The purpose of providing these embodiments is to make the disclosure content of the present application more thorough and comprehensive. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0022] In the description of the present application, the terms "first", "second", "third", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", etc. may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0023] In the description of the present application, it should be noted that, unless otherwise clearly defined and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. The terms "vertical", "horizontal", "left", "right", "upper", "lower" and similar expressions used herein are only for the purpose of illustration, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0024] In the description of the present application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present application have the same meanings as those commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0025] An embodiment of the present application provides a passive temperature alarm device. Specifically, please refer to Figure 1 , Figure 1 which shows a schematic structural diagram of the passive temperature alarm device in one of the embodiments of the present application, and it includes: a receiving antenna 3, a conductive material 4, a temperature bistable memory material 2, and a housing 1. Among them, The receiving antenna is arranged on one side of the housing, and an antenna chip is built in the receiving antenna. The impedance of the antenna chip is designed to match the impedance generated by the receiving antenna during operation; The temperature bistable memory material is arranged on the other side of the housing, and a conductive material is attached to the deformation end of the temperature bistable memory material. The temperature bistable memory material is composed of a shape memory material.

[0026] In an embodiment of the present application, a signal transceiver is placed within the wireless signal transmission range of the receiving antenna, used to transmit energy to activate the receiving antenna, then receive the reflected signal of the receiving antenna, and finally sense the temperature change in the reflected signal, so as to establish a communication interaction with the receiving antenna.

[0027] In one embodiment of the present application, a conductive material is attached to the surface of a temperature bistable memory material, which is used to change the boundary conditions of the receiving antenna, thereby changing the impedance matching degree of the receiving antenna, and ultimately affecting the reflection signal of the receiving antenna to the signal transceiver.

[0028] In one embodiment of the present application, considering the influence of the conductive material on the performance of the receiving antenna, when the receiving antenna is close to the conductive material, it will weaken the radio frequency energy field and also cause the receiving antenna to be detuned. This detuning effect will change with the distance between the conductive material and the receiving antenna.

[0029] The temperature bistable memory material is installed on the inner side of the bottom layer of the housing, and changes its own shape by sensing the ambient temperature change, so as to adjust the distance between the conductive material and the receiving antenna.

[0030] The initial state of the temperature bistable memory material is in a contracted state. When the temperature bistable memory material senses that the ambient temperature is lower than the deformation temperature threshold, the temperature bistable memory material remains in the contracted state. At this time, the distance between the conductive material and the receiving antenna remains relatively large. When the contracted state remains stable, the passive temperature alarm system tends to be stable. In this stable state, the optimal operating frequency of the receiving antenna is between 920 - 925 MHz; when the temperature bistable memory material senses that the ambient temperature is higher than the deformation temperature threshold, the temperature bistable memory material begins to expand and recover its deformation, thereby reducing the distance between the conductive material and the receiving antenna. When the expansion and recovery of deformation tend to be stable, the passive temperature alarm system tends to be stable. In this stable state, the optimal operating frequency of the receiving antenna is between 905 - 912 MHz; the temperature bistable memory material can change its shape multiple times. When the ambient temperature drops below the deformation temperature threshold again, the temperature bistable memory material can return to the contracted state again, and again increase the distance between the receiving antenna and the conductive material. After this state remains stable, the passive temperature alarm system can still tend to be stable. At this time, the optimal operating frequency of the receiving antenna returns to between 920 - 925 MHz again; due to the memory characteristics of the temperature bistable memory material, the ambient temperature can be repeatedly detected whether it exceeds the threshold temperature.

[0031] In one embodiment of the present application, the conductive material is fixedly connected to the temperature bistable memory material. When the ambient temperature is below the deformation temperature threshold T, the temperature bistable memory material remains deformed and in a stable state, as Figure 2 shown, Figure 2 which shows the stable state diagram of the passive temperature alarm device in one embodiment of the present application when the temperature is lower than T. The conductive material stays at the distance from the receiving antenna, which makes the distance between the receiving antenna and the conductive material relatively far, and the performance of the receiving antenna remains relatively normal, manifested in the optimal operating frequency of the receiving antenna, and the optimal operating frequency remains between 920 - 925 MHz.

[0032] When the ambient temperature starts to be higher than the deformation temperature threshold T and is in a transient state, as Figure 3 shown, Figure 3 shows a transient diagram of the passive temperature alarm device in one embodiment of the present application when the temperature is higher than T. The temperature bistable memory material begins to recover its deformation, causing the conductive material to gradually approach the receiving antenna. This shortens the distance between the receiving antenna and the conductive material, causing the receiving antenna to detune and its performance to start degrading, manifested in the optimal operating frequency of the receiving antenna, and the optimal operating frequency begins to shift. When the temperature is higher than the deformation temperature threshold T and is in a steady state, as Figure 4 shown, Figure 4 shows a steady-state diagram of the passive temperature alarm device in one embodiment of the present application when the temperature is higher than T. The temperature bistable memory material fully recovers its deformation, causing the conductive material to be located at a distance from the receiving antenna. This makes the distance between the receiving antenna and the conductive material relatively close, causing the receiving antenna to detune and its performance to degrade, manifested in the optimal operating frequency of the receiving antenna, and the optimal operating frequency remains between 905 - 912 MHz.

[0033] When the temperature starts to be lower than the deformation temperature threshold T again and is in a transient state, as Figure 5 shown, Figure 5 shows a transient diagram of the passive temperature alarm device in one embodiment of the present application when the temperature is lower than T. The temperature bistable memory material begins to deform again, once again increasing the distance between the conductive material and the receiving antenna, affecting the degree of detuning of the receiving antenna and causing the optimal operating frequency to shift.

[0034] Therefore, the temperature bistable memory material can well act as a temperature-driven switch. In combination with the presence of the conductive material, it can change its shape above and below the deformation temperature threshold, and the optimal operating frequency of the receiving antenna will also change significantly. Moreover, this change in the temperature bistable memory material is not one-time and can repeatedly deform above and below the deformation threshold temperature, allowing for repeated detections.

[0035] Preferably, in one embodiment of the present application, the temperature bistable memory component includes, but is not limited to, crosslinked cyclooctene and polyurethane.

[0036] Specifically, the common raw material of the temperature bistable memory material is a crosslinked semi-crystalline polymer, which is based on crystallization-induced extension and melt-induced contraction, such as crosslinked cyclooctene and polyurethane.

[0037] Preferably, in an embodiment of the present application, the passive temperature alarm device further includes a signal transceiver, which is communicatively connected to the receiving antenna. The signal transceiver is configured to transmit energy to activate the receiving antenna, receive the reflected signal of the receiving antenna, and sense the temperature change in the reflected signal.

[0038] The housing is used to encapsulate the receiving antenna, the conductive material, and the temperature bistable memory material, and is used to shield external electromagnetic interference.

[0039] Preferably, in an embodiment of the present application, the receiving antenna includes an embedded T-shaped matching antenna.

[0040] In this embodiment, in order for the passive temperature alarm system using the frequency modulation method to be effectively implemented, an antenna that meets impedance matching must be used, and this antenna shows an appropriate shift in the optimal operating frequency when the temperature threshold of interest is violated. Therefore, the design requirements for such an antenna are as follows: 1) Narrow bandwidth: Design the antenna so that the optimal operating frequency is between in state 1 and between in state 2, and all other frequencies in all other frequency ranges drop sharply.

[0041] 2) When at the optimal matching frequency (power transfer efficiency) is close to 1: For a given signal transceiver transmission power, the readable range is directly related to . For the two states of the passive temperature alarm system, at the optimal operating frequency, should be as close to 1 as possible, which will ensure a long reading distance for the system.

[0042] Another embodiment of the present application provides an antenna design method, which is applied to the passive temperature alarm device as described above. Specifically, please refer to Figure 6 , Figure 6 which shows a schematic flowchart of the antenna design method in one embodiment of the present application, and it includes steps S1 - S5: S1: Input the set of structural dimension parameters of the pre-constructed receiving antenna and the first distance between the receiving antenna and the conductive sheet into the electromagnetic simulation model for calculation to obtain the first impedance parameter set of the receiving antenna; Specifically, this embodiment proposes a design of an embedded T-shaped matching antenna, and its advantage is that the number of design parameters is limited. These parameters include: length L, width W, slot width s, slot height and slot thickness t. Another parameter is assumed, where . As shown in Figure 7 , Figure 7 is a schematic diagram of the parameters of the receiving antenna design in this embodiment.

[0043] The goal of this embodiment regarding antenna design is: to determine a set of antenna parameter dimensions to meet the impedance matching of the antenna. Specifically, determine a set of parameters (L, W, , s), when the distance between the conductive material and the receiving antenna is , its optimal operating frequency band is between , and when the distance is , its optimal operating frequency band is between . To limit the design space, fix t = 1 mm in the design.

[0044] Set reasonable value ranges and value precisions for each key dimension parameter. The value range should be determined based on the antenna design goal and the actual application scenario, and the value precision should consider the efficiency of simulation calculation and the accuracy of the results. For example, the value range of the antenna length L can be set as [100 mm, 200 mm], and the value precision is 1 mm.

[0045] Generate a set of structural dimension parameters of the receiving antenna by means of parameter combination. For example, by traversing the value ranges of each key dimension parameter, generate all possible parameter combinations to form a set containing multiple parameter combinations.

[0046] According to the type and design requirements of the antenna, select a suitable electromagnetic simulation software. Common electromagnetic simulation software includes ANSYS HFSS, CST Microwave Studio, etc. Establish a three-dimensional model of the receiving antenna and the conductive sheet in the simulation software. According to the pre-constructed set of structural dimension parameters, accurately set the geometric shape and size of the antenna; at the same time, determine the relative position of the conductive sheet and the receiving antenna according to the obtained first distance. Input the pre-constructed set of structural dimension parameters of the receiving antenna and the obtained first distance into the electromagnetic simulation model. In the simulation software, different parameter combinations can be input into the model for calculation in turn through parametric settings.

[0047] Extract the first impedance parameter set of the receiving antenna from the calculation results. The impedance parameters usually include resistance R and reactance X, and these parameters can be directly extracted through the post-processing function provided by the software. Organize the impedance parameters corresponding to each parameter combination into a set, which is the first impedance parameter set of the receiving antenna.

[0048] S2: Calculate the splitting factor according to the obtained chip impedance parameters of the antenna chip and the first impedance parameter set, where the splitting factor is used to quantify the impedance matching degree between the receiving antenna and the antenna chip; In antenna design, it is crucial to achieve good impedance matching between the receiving antenna and the antenna chip. Good impedance matching can maximize the power transfer efficiency between the antenna and the chip, reduce signal reflection, and improve the performance of the entire system. As a quantization index, the splitting factor can help us measure the impedance matching degree between the receiving antenna and the antenna chip. By calculating the splitting factor, we can screen out more optimal antenna structure size parameters to achieve better impedance matching effects.

[0049] The impedance parameters of the antenna chip are usually provided by the chip manufacturer or measured by professional test equipment (such as a vector network analyzer). The chip impedance parameters include the chip resistance and the chip reactance, and these two parameters are the basic data for subsequent calculation of the splitting factor.

[0050] The first set of impedance parameters is calculated by inputting the set of structural size parameters of the pre-built receiving antenna and the first distance between the receiving antenna and the conductive sheet into the electromagnetic simulation model. This set contains the impedance parameters of the receiving antenna under different structural size parameters, that is, the receiving antenna resistance and the receiving antenna reactance.

[0051] Preferably, in an embodiment of the present application, the splitting factor is expressed as: or Wherein, is the splitting factor, is the receiving antenna resistance, is the receiving antenna reactance, is the antenna chip resistance, is the antenna chip reactance, is the slot width of the receiving antenna, is the slot height of the receiving antenna, is the slot thickness of the receiving antenna, is the width of the receiving antenna.

[0052] Organize the splitting factor values corresponding to each combination of calculated structural size parameters into a set, and this set reflects the impedance matching degree between the receiving antenna and the antenna chip under different structural sizes.

[0053] According to the calculation results of the splitting factor, screen the set of structural dimension parameters of the pre-constructed receiving antenna. Retain the combinations of structural dimension parameters with splitting factors close to the ideal value, and eliminate those combinations with splitting factors deviating significantly from the ideal value, thereby narrowing the scope of subsequent design and optimization and improving the design efficiency.

[0054] S3: Construct a function graph of the splitting factor varying with the structural dimension parameters based on the first impedance parameter set and the splitting factor, and screen the first set of structural dimension parameters of the receiving antenna that meet the feasibility constraints according to the function graph; Preferably, in an embodiment of the present application, constructing a function graph of the splitting factor varying with the structural dimension parameters based on the first impedance parameter set and the splitting factor, and screening the first set of structural dimension parameters of the receiving antenna that meet the feasibility constraints according to the function graph includes: Taking the structural dimension parameters as the independent variable and the splitting factor as the dependent variable, use the curve fitting method to construct a function graph of the splitting factor varying with the structural dimension parameters; Determine the feasibility constraints of the receiving antenna. The feasibility constraints include the machining accuracy limitations of the structural dimension parameters, the availability and cost limitations of the materials, and the space limitations of the overall size of the receiving antenna; Mark the area that meets the feasibility constraints on the function graph, and screen out the structural dimension parameters located within the area from the set of structural dimension parameters to generate the first set of structural dimension parameters of the receiving antenna.

[0055] Among them, common fitting methods include: linear fitting, polynomial fitting, and non-linear fitting. Use professional drawing software (such as MATLAB, Origin, etc.), according to the selected curve fitting method, fit the data of the structural dimension parameters and the splitting factor, and draw a function graph of the splitting factor varying with the structural dimension parameters. If studying the influence of multiple structural dimension parameters on the splitting factor, it may be necessary to draw three-dimensional or multi-dimensional function graphs. Figure 8 This is the function graph of the splitting factor varying with the antenna length and width in the antenna design of this embodiment, where Figure 8 the ordinate represents the splitting factor, as Figure 8 shown, it can be concluded that for each (L, W), there is a unique match.

[0056] In the actual manufacturing process, the structural dimension parameters of the antenna need to meet certain machining accuracy requirements. For example, the dimensions such as the length and width of the antenna may need to be controlled within a certain tolerance range. If the machining accuracy cannot meet the requirements, it may lead to a decline in the performance of the antenna. For example, the slot width s of the antenna requires a machining accuracy of ( ), then when screening the structural dimension parameters, it is necessary to ensure that the selected s value can be machined within this accuracy range.

[0057] The manufacturing of an antenna requires the use of specific materials, and the availability and cost of these materials are also important considerations. Some high-performance materials may be difficult to obtain or too costly, which limits the selection of the antenna structure size parameters. For example, a certain special conductive material is expensive, and to control costs, some combinations of structure size parameters with less usage of this material may need to be selected.

[0058] In practical applications, the receiving antenna needs to be installed in a specific space, so its overall size is restricted by the space. For example, in some small devices, the length and width of the antenna cannot exceed certain values. This requires screening out combinations of structure size parameters that can meet the space requirements of the overall size.

[0059] In an embodiment of the present application, when the distance between the receiving antenna and the conductive material is determined to be the antenna can match the given chip impedance within the frequency range. Applying the constraint / W≈0.7, for the given (L,W) values and for each family of W, select a slot width s to make the antenna match the given chip impedance within the frequency range.

[0060] According to the determined feasibility constraint conditions, mark the areas that meet these constraints on the function graph of the splitting factor varying with the structure size parameters. From the pre-built set of structure size parameters, screen out those structure size parameters whose corresponding points are located within the marked feasible areas. These parameters not only meet the requirements of the splitting factor (reflected by the function graph) but also conform to the feasibility constraint conditions. Organize the screened-out structure size parameters into a set, which is the first set of structure size parameters of the receiving antenna.

[0061] S4: Input the second distance between the receiving antenna and the conductive sheet after the high-temperature deformation of the obtained temperature two-way memory component and the set of structure size parameters into the electromagnetic simulation model for calculation to obtain the second set of impedance parameters of the receiving antenna; Preferably, in an embodiment of the present application, the first distance includes the spacing between the receiving antenna and the conductive sheet when the temperature two-way memory component is at room temperature; the second distance includes the spacing between the receiving antenna and the conductive sheet when the temperature two-way memory component undergoes high-temperature deformation; Before inputting the second distance between the receiving antenna and the conductive sheet after the high-temperature deformation of the obtained temperature two-way memory component and the set of structure size parameters into the electromagnetic simulation model for calculation, it further includes: Test the high-temperature deformation characteristics of the temperature two-way memory component and determine the second distance according to the test results; Input the second distance and the set of structural dimension parameters into the electromagnetic simulation model, and reset the boundary conditions and calculation parameters of the simulation model.

[0062] Specifically, input the determined second distance and the set of structural dimension parameters obtained by previous screening into the electromagnetic simulation model. According to the characteristics of the influence of temperature change on antenna performance, reset the calculation parameters. After the simulation calculation is completed, extract the impedance parameters of the receiving antenna from the simulation results. Since multiple combinations of structural dimension parameters are input, a series of impedance parameter values will be obtained, and these values are sorted into the second impedance parameter set.

[0063] S5: Screen the first set of structural dimension parameters according to the first impedance parameter set and the second impedance parameter set to obtain the target structural dimension parameters of the receiving antenna.

[0064] In antenna design, it is necessary to determine appropriate antenna dimension parameters (such as length L, width W, slot height, slot width s, etc.) to achieve good impedance matching between the antenna and the chip and enable the antenna to have better performance at different operating distances.

[0065] In an embodiment of the present application, when the given dimension parameters and the antenna length L are relatively long, the antenna can well match the chip impedance at a distance (h = 10 mm). When the distance is changed to (h = 3 mm), the antenna is severely detuned from the conjugate matching position. The present application performs antenna impedance analysis through the Smith chart. Among them, the Smith chart is a tool for analyzing and representing the impedance characteristics of transmission lines and antennas. On the chart, the conjugate matching position usually represents the best matching state of the impedance between the antenna and the load (chip). Severe detuning means that the impedance of the antenna no longer matches the chip impedance, which will cause a large amount of signal reflection, resulting in a significant reduction in the power transmission efficiency of the antenna.

[0066] Since the power transmission efficiency of the antenna is poor at (h = 3 mm), the reading range of the sensor will be severely limited. The reading range of the sensor depends on the energy transmission efficiency between the antenna and the external signal source. When it decreases, the effective signal strength received by the antenna weakens, resulting in a smaller distance range within which the sensor can accurately read the signal. Therefore, a long L is not a good parameter choice for the design of this antenna.

[0067] Similarly, when given the dimensional parameters and with a short antenna length L, the antenna can also well match the chip impedance at a distance (h = 10 mm), which indicates that at this initial state, the antenna with short L can also achieve good power transfer with the chip. When the distance changes from (h = 10 mm) to (h = 3 mm), it can be seen from the Smith chart that the detuning of the antenna is very slight. This means that even when the operating distance changes, the impedance of the short-L antenna can still relatively well maintain the matching relationship with the chip impedance, and the signal reflection is relatively small.

[0068] Due to the slight antenna detuning, when the sensor changes its state (i.e., the distance changes from (h = 10 mm) to (h = 3 mm)), a slight change in the optimal operating frequency can be observed. At the same time, because the detuning is not as severe as that of the long-L antenna, it can be expected that the power transfer efficiency values of the antenna are quite high in both sensor states ((h = 10 mm) and (h = 3 mm)). The higher power transfer efficiency helps to increase the reading range of the sensor. At different operating distances, the short-L antenna can maintain good energy transfer performance, enabling the sensor to accurately read signals within a wider distance range, thus improving the performance of the entire sensor system.

[0069] Through the analysis of the bandwidth characteristics and impedance changes of the T-shaped matching antenna at different distances in both the long-L and short-L cases, it can be concluded that the short-L antenna is a better choice in this antenna design. In the subsequent antenna design process, other dimensional parameters (such as W, s, etc.) can be further optimized based on the characteristics of the short-L antenna to maximize the antenna performance.

[0070] In an embodiment of the present application, when there are multiple groups of parameters that meet the requirements, draw a graph of the simulated values of the power transfer efficiency as a function of frequency at different W and h.

[0071] The power transfer efficiency represents the energy that the chip can obtain from the antenna. The closer it is to 1, the better the impedance matching degree between the chip and the antenna. Figure 9 is the function graph of the power transfer efficiency varying with frequency at a distance of in the antenna design of this embodiment, where the ordinate of the function graph represents , and it can be seen that the optimal operating frequency of the antenna with W = 20 mm is 922 MHz; Figure 10 is the function graph of the power transfer efficiency varying with frequency at a distance of in the antenna design of this embodiment, where the ordinate of the function graph represents , and it can be seen that the optimal operating frequency of the antenna with W = 20 mm is 907 MHz.

[0072] At and The greater the difference in the frequencies at which the peaks of are located, the better the antenna's state separation in the frequency domain, which will facilitate the implementation of temperature detection using the frequency modulation method. However, the prerequisite is that the peaks of τ remain at a high level at both distances, otherwise the impedance matching of the antenna is not satisfied and it cannot work properly.

[0073] From Figure 9 and Figure 10 it can be seen that the antennas corresponding to W = 10mm and W = 20mm meet the requirements. Their optimal operating frequencies change with the position of the conductive material. The antenna with W = 10mm has a high power transfer coefficient when the antenna-conductive material spacing is 3mm, while the antenna with W = 20mm has a high power transfer coefficient when the antenna-conductive material spacing is 10mm.

[0074] Another difference is that W = 20mm provides a 15MHz shift in the peak operating frequency compared to the case of W = 10mm, from 922MHz at h = 10mm to 907MHz at h = 3mm, thus having better state separation in the frequency domain. Therefore, W = 20mm is a better parameter choice.

[0075] Summarizing the above steps, the core lies in: for , find a set S = ([[]] , ) where impedance matching between the antenna and the given chip is possible; for all i in S, find the corresponding values of ( , s) whose optimal operating frequency band is between 920 - 925MHz. Let this set be denoted as M; for all i in M, determine whether there exists such an i that when , the optimal operating frequency shifts to between 905 - 912MHz without significantly affecting .

[0076] Preferably, in an embodiment of the present application, the structural dimension parameter set is screened according to the first impedance parameter and the second impedance parameter to obtain the target structural dimension parameters of the receiving antenna, including: According to the first impedance parameter set and the second impedance parameter set, calculate the power transfer efficiency of each structural dimension parameter in the first structural dimension parameter set at the first distance and the second distance respectively; Perform a preliminary screening on the first structural dimension parameter set according to the power transfer efficiency to obtain the first screening result; Calculate the frequency response characteristics of each structural dimension parameter in the first screening result at the first distance and the second distance respectively; Perform secondary screening on the first screening result according to the frequency response characteristics to obtain the target structural size parameters of the receiving antenna.

[0077] Preferably, in an embodiment of the present application, the power transfer efficiency is expressed as: Wherein, is the power transfer efficiency in the matching state, is the resistance of the receiving antenna, is the reactance of the receiving antenna, is the resistance of the antenna chip, is the reactance of the antenna chip.

[0078] Specifically, according to the specific requirements and performance indicators of the antenna design, set the screening criteria for the power transfer efficiency. For example, it is required that the power transfer efficiency of the antenna at the first distance and the second distance is not lower than a certain threshold to ensure that the antenna can achieve a high energy transfer efficiency in different working states.

[0079] Traverse the power transfer efficiency values corresponding to each structural size parameter in the first set of structural size parameters, and retain those structural size parameters whose power transfer efficiency meets the screening criteria at the first distance and the second distance to form the first screening result. The structural size parameters that do not meet the screening criteria are excluded because the corresponding antennas cannot meet the design requirements in terms of power transfer performance.

[0080] The frequency response characteristics describe the performance of the antenna at different frequencies, including the changes in the antenna's gain, radiation pattern, input impedance, etc. with frequency. In this step, focus on the frequency response characteristics of the antenna at the first distance and the second distance, especially parameters such as the resonant frequency and bandwidth of the antenna.

[0081] For each structural size parameter in the first screening result, use electromagnetic simulation software or theoretical calculation methods to calculate its frequency response characteristics at the first distance and the second distance respectively. Specifically, by performing frequency-domain analysis on the electromagnetic model of the antenna, the scattering parameters of the antenna at different frequencies can be obtained, so as to determine the frequency response characteristic parameters such as the resonant frequency and bandwidth of the antenna.

[0082] According to the operating frequency band and design requirements of the antenna, screening criteria for the frequency response characteristics are set. For example, it is required that the resonant frequencies of the antenna at the first distance and the second distance both fall within the specified operating frequency band and have sufficient bandwidth to meet the signal transmission requirements. At the same time, factors such as the gain stability of the antenna at different frequencies can also be considered. Traverse the frequency response characteristic parameters corresponding to each structural dimension parameter in the first screening result, and retain those structural dimension parameters whose frequency response characteristics meet the screening criteria at the first distance and the second distance. Finally, the target structural dimension parameters of the receiving antenna are obtained. The antennas corresponding to these target structural dimension parameters can meet the design requirements in terms of power transmission efficiency and frequency response characteristics and can achieve good performance at different operating distances.

[0083] Compared with the prior art, the beneficial effects of the embodiments of the present application are at least one of the following: (1) The temperature bistable memory material designed in the present application enables the receiving antenna to assist in memorizing and storing events beyond the threshold temperature. At the same time, it can maintain different forms above and below the threshold temperature and can change its own shape in real time according to the temperature. Moreover, this change is not a one-time occurrence and can be changed repeatedly. The resulting change in the receiving antenna signal can help the staff quickly detect faults.

[0084] (2) The present application adopts a frequency modulation strategy to implement a passive temperature alarm system. This method can change the optimal operating frequency of the receiving antenna when a temperature change is detected, thereby realizing the temperature alarm function. Applying this method, compared with other passive temperature sensors using amplitude modulation strategies, etc., there is no need to set multiple receiving antennas and measure them. Therefore, the sensor volume can be further reduced, and the cost can be lowered at the same time. Moreover, since the change in the threshold transmission power provided to the chip due to the change in the reading distance is very slight and is little affected by the channel fading caused by the multipath effect, the reading range of the passive temperature alarm system can be larger, making the application range wider and the application more convenient and effective.

[0085] (3) The impedance matching method for the T-shaped antenna design proposed in the present application can serve the passive temperature alarm system based on frequency modulation and ensure the effective operation of the system. Using a compliant antenna is the basic guarantee for the effective implementation of the frequency modulation method.

[0086] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A passive temperature alarm device, characterized in that: include: Receiving antenna, conductive material, temperature bidirectional memory material and casing, wherein: The receiving antenna is arranged on one side of the housing, and the receiving antenna has an antenna chip built therein, and the impedance of the antenna chip is designed to match the impedance generated by the receiving antenna during operation; The temperature bidirectional memory material is arranged on the other side of the shell, and the conductive material is attached to the deformation end of the temperature bidirectional memory material. The temperature bidirectional memory material is composed of shape memory material.

2. The passive temperature alarm device according to claim 1, characterized in that: The receiving antenna includes an embedded T-type matching antenna.

3. The passive temperature alarm device according to claim 1, characterized in that: The temperature bidirectional memory material includes but is not limited to cross-linked cyclooctene and polyurethane.

4. The passive temperature alarm device according to claim 1, characterized in that: The passive temperature alarm device also includes a signal transceiver, which is communicatively connected to the receiving antenna. The signal transceiver is used to transmit energy to activate the receiving antenna, then receive the reflected signal of the receiving antenna, and sense the temperature change in the reflected signal.

5. An antenna design method, applied to the passive temperature alarm device according to any one of claims 1 to 4, characterized in that: include: Inputting the pre-constructed structural dimension parameter set of the receiving antenna and the acquired first distance between the receiving antenna and the conductive material into an electromagnetic simulation model for calculation to obtain a first impedance parameter set of the receiving antenna; Calculating a splitting factor according to the acquired chip impedance parameter of the antenna chip and the first impedance parameter set, wherein the splitting factor is used to quantify the impedance matching degree between the receiving antenna and the antenna chip; Constructing a function graph of the splitting factor as the structure size parameter changes according to the first impedance parameter set and the splitting factor, and screening a first structure size parameter set of the receiving antenna that meets the feasibility constraint according to the function graph; Inputting the obtained second distance between the receiving antenna and the conductive material after the temperature bidirectional memory material is deformed at high temperature and the set of structural dimension parameters into the electromagnetic simulation model for calculation to obtain a second impedance parameter set of the receiving antenna; The first structure size parameter set is screened according to the first impedance parameter set and the second impedance parameter set to obtain target structure size parameters of the receiving antenna.

6. The antenna design method according to claim 5, characterized in that: The split factor is expressed as: or in, is the splitting factor, is the receiving antenna resistance, is the receiving antenna reactance, is the antenna chip resistance, is the antenna chip reactance, is the slot width of the receiving antenna, is the slot height of the receiving antenna, is the slot thickness of the receiving antenna, is the width of the receiving antenna.

7. The antenna design method according to claim 5, characterized in that: The step of constructing a function graph of the splitting factor as the structure size parameter changes according to the first impedance parameter set and the splitting factor, and screening a first structure size parameter set of the receiving antenna that satisfies a feasibility constraint according to the function graph includes: With the structural size parameter as the independent variable and the splitting factor as the dependent variable, the curve fitting method is used to construct the function graph of the splitting factor changing with the structural size parameter. Determining feasibility constraints of the receiving antenna, wherein the feasibility constraints include processing accuracy constraints of structural size parameters, availability and cost constraints of materials, and space constraints of the overall size of the receiving antenna; An area satisfying the feasibility constraint is marked on the function graph, and structural dimension parameters located in the area are screened out from the structural dimension parameter set to generate a first structural dimension parameter set for the receiving antenna.

8. The antenna design method according to claim 5, characterized in that: The first distance includes the distance between the receiving antenna and the conductive material when the temperature bidirectional memory material is at room temperature; the second distance includes the distance between the receiving antenna and the conductive material when the temperature bidirectional memory material is deformed at high temperature; Before inputting the obtained second distance between the receiving antenna and the conductive material after the temperature bidirectional memory material is deformed at high temperature and the set of structural dimension parameters into the electromagnetic simulation model for calculation, the method further includes: Testing the high temperature deformation characteristics of the temperature bidirectional memory material, and determining the second distance according to the test result; The second distance and the set of structural dimension parameters are input into the electromagnetic simulation model, and the boundary conditions and calculation parameters of the simulation model are reset.

9. The antenna design method according to claim 5, characterized in that: The step of screening the set of structural dimension parameters according to the first impedance parameter and the second impedance parameter to obtain the target structural dimension parameters of the receiving antenna includes: According to the first impedance parameter set and the second impedance parameter set, respectively calculating the power transmission efficiency of each structural size parameter in the first structural size parameter set at the first distance and the second distance; Preliminarily screening the first set of structural dimension parameters according to the power transmission efficiency to obtain a first screening result; respectively calculating the frequency response characteristics of each structural size parameter in the first screening result at the first distance and the second distance; The first screening result is screened a second time according to the frequency response characteristic to obtain target structural size parameters of the receiving antenna.

10. The antenna design method according to claim 9, characterized in that: The power transfer efficiency is expressed as: in, is the power transfer efficiency in the matching state, is the receiving antenna resistance, is the receiving antenna reactance, is the antenna chip resistance, is the antenna chip reactance.

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