A wireless temperature sensor based on log-periodic dipole antenna and cavity filter

Abstract

The present invention discloses a wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter. The sensor realizes wireless isolated transmission and reception of microwave signals by loading a logarithmic periodic dipole antenna with linearly polarized radiation characteristics into the input and output ports of the filter in an orthogonal state through a coaxial line. To achieve tuning control of the filter, one of the coupling posts is loaded in a manner that allows for good contact and up and down sliding, and is connected to a metal thermal sensing branch wrapped in a high-temperature resistant ceramic shell via a flange. Thereafter, thermal linear expansion information of the metal thermal sensing branch wrapped in the ceramic shell is converted into state control information for the coupling post, completing the conversion and output of the temperature information to the filter tuning, and wirelessly extracting the temperature information through a vector network analyzer. Since the thermal sensing area and the temperature information conversion area of ​​the sensor are isolated from each other, the sensor can achieve high-temperature wireless measurement capabilities exceeding 1400°C (with an average accuracy of 0.356 MHz / °C).

Description

Technical Field

[0001] The present invention relates to the technical field of strain detection sensors, and in particular to a microwave wireless temperature sensor. Background Art

[0002] Real-time and effective temperature measurement of industrial devices has always been a crucial component of activities such as pipeline transportation, chemical production, steelmaking, and energy transportation. With the development of industrial civilization, these activities, such as steelmaking, chemical production, energy transportation, and aerospace, are rapidly moving toward higher temperature limits, more complex and tightly packed systems, and higher-value industrial equipment. Consequently, new requirements have emerged for the development of temperature sensors with excellent environmental adaptability, a simple system architecture, and superior measurement performance to enable operational temperature measurement, process monitoring, process control, safety warnings, and related scientific research in high-temperature and high-pressure chemical reactors, high-temperature and high-pressure steelmaking furnaces, and high-temperature and high-pressure heat flow pipelines.

[0003] Therefore, to meet the high-temperature measurement needs of industrial high-temperature and high-pressure reactors, smelting furnaces, and high-temperature and high-pressure heat flow piping systems and devices, many traditional temperature measurement methods have been proposed, such as thermal infrared temperature measurement, thermocouple temperature measurement, fiber optic temperature measurement, and microwave induction resonance temperature measurement. As one of these traditional temperature measurement methods, thermal infrared radiation temperature measurement uses an infrared camera to capture the thermal infrared radiation characteristics of the system / environment under test and extract the corresponding temperature information based on this thermal infrared radiation characteristic information. Because thermal infrared radiation temperature measurement can capture radiation information from a large area in a single pass, it is often used in scenarios where rapid flat-surface temperature distribution information is required. However, while this method offers rapid flat-surface temperature measurement capabilities, it is generally only suitable for measuring temperatures in open spaces. For enclosed systems under test, this temperature measurement method can only measure surface temperatures, obtaining internal temperature information through temperature compensation. Therefore, it is often inadequate for measuring the temperature of enclosed spaces, systems, or components. Furthermore, thermocouple-based industrial temperature measurement, as the most common industrial temperature measurement method, is currently widely used in various industrial activities, such as high-temperature synthesis of chemical materials and aircraft engine fuel gas temperature measurement. This temperature measurement method relies on the fact that a temperature probe, exposed to temperature in the test environment, generates a different electric potential due to temperature excitation of internal dopants within the probe. This creates an internal potential difference, which is then read to measure temperature. This method offers advantages such as a simple test system, high temperature measurement accuracy, and a high temperature limit (thermocouples can reach up to approximately 3000K). However, it should be noted that despite its many advantages, the probe must remain wired during use. Therefore, when measuring in extremely high-temperature environments, complex cooling systems are often required, further negating its inherent convenience. Finally, fiber-optic temperature measurement, a less common method, measures temperature by exploiting changes in the optical properties of the light signal, such as intensity, wavelength, frequency, phase, and polarization state, caused by tiny structural changes in the probe under temperature excitation. This method is characterized by low signal energy and sensitive temperature measurement. However, it should be noted that fiber-optic temperature measurement has limitations, such as a limited temperature limit and relatively complex test equipment. As a research hotspot in recent years, with the rapid development of microwave technology, research on temperature measurement using microwave sensors has gained traction. As a relatively new temperature measurement method, microwave temperature measurement mainly converts temperature excitation into the structure of the temperature probe components.

[0004] This is achieved by real-time reading of changes in the probe's microwave characteristics, such as resonant frequency, amplitude, phase, and time delay, caused by changes in the probe's structural characteristics, such as deformation, displacement, and stretching. Furthermore, microwave sensors can isolate the temperature sensing area from the temperature information conversion area, enabling them to measure extremely high temperatures. Furthermore, microwaves possess excellent spatial transmission properties, allowing for wireless signal transmission, further enhancing the sensor's simplicity and adaptability to complex environments.

[0005] To this end, a number of microwave wireless temperature sensors have been proposed. These primarily utilize the capacitive-inductive coupling effect of equivalent capacitive sensing plates at close range. Using near-field inductive coupling, they extract the resonant characteristic changes caused by temperature-induced structural changes in the temperature probe, thereby wirelessly measuring the ambient temperature. However, it should be noted that while this method overcomes the wired connection bottleneck of traditional thermocouple temperature measurement, its wireless temperature measurement range is very limited, often only within a few centimeters. Furthermore, because it relies on direct temperature sensing, it is difficult to use for temperature measurement in equipment with confined spaces, such as those involving high-temperature and high-pressure environments. Furthermore, its temperature measurement limit is also limited (reported temperatures have not exceeded 1300°C). Another approach to microwave wireless temperature measurement is to integrate a transponder antenna (dual antenna) with a traditional temperature probe, achieving microwave wireless information transmission while maintaining temperature measurement capabilities. Obviously, compared to near-field coupled induction, this method achieves the ability to measure temperature wirelessly over long distances. However, due to the integration of traditional devices such as thermal resistors, the welding parts of this method have a very limited ability to withstand high temperatures. Therefore, the temperature measurement limit is not high enough, and it still faces the problem of being difficult to use in metal confined spaces. Therefore, for the above-mentioned current microwave temperature measurement technology, although they have solved the problems of wireless connection and high environmental adaptability of traditional temperature sensors, it is still difficult to effectively measure the ambient temperature inside high-temperature and high-pressure closed cavities and the temperature measurement limit is not high enough. Therefore, in order to further improve the universality and temperature measurement limit of microwave wireless temperature sensors, further research on microwave sensors is needed. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter.

[0007] The technical solution adopted in the present invention is:

[0008] A wireless temperature sensor based on a broadband logarithmic periodic dipole antenna and a cavity filter, wherein the sensor realizes the isolation of microwave signal reception and transmission of the cavity filter by loading a logarithmic periodic dipole antenna with linear polarization radiation characteristics to the microwave signal input and output ports of the cavity filter in an orthogonal arrangement; at the bottom of the cavity filter, one of the coupling metal pillars is loaded in a manner that is in good contact and can slide freely up and down, and is extended to a certain outer cavity dimension, thereby realizing the tuning of the working frequency band of the cavity filter by adjusting the loading state of the slidable metal coupling pillar; at the bottom surface of the coupling pillar that is in good electrical contact and can slide freely, a flange is used to connect a metal thermal sensing branch wrapped in a high-temperature ceramic shell to it, thereby converting the thermal excitation of the metal thermal sensing branch wrapped in the high-temperature ceramic shell into the coupling pillar.

[0009] Slide up and down to control the conversion of temperature information into the operating frequency band characteristics of the cavity filter. On this basis, using a vector network analyzer, by loading the input and output ports with a logarithmic periodic antenna identical to the two ports of the cavity filter and arranged in the same manner, the cavity filter is wirelessly queried in real time. By reading the frequency band offset information of the feedback signal, the measured temperature information can be obtained, thereby wirelessly measuring the temperature of the measured object. It can be found that the present invention uses the basic physical phenomenon of metal thermal expansion to tune the operating characteristics of the cavity filter, so that the thermal sensing area and the temperature information conversion response area of ​​the sensor are isolated from each other during operation, thereby giving the sensor a wireless temperature measurement capability exceeding 1400°C and an average temperature frequency deviation of 0.356MHz / °C, relying solely on the thermal sensing branches of the metal and the thermal response limit of the high-temperature ceramic. At the same time, the broadband logarithmic periodic dipole antenna with an orthogonal arrangement and an available bandwidth of 6.08GHz ensures the isolation of the input and output signals while its broadband characteristics ensure the broadband signal output of the cavity filter and the frequency band tuning response output performance under temperature excitation. At the same time, due to its simple structure and easy disassembly, the present invention can flexibly adjust the temperature measurement method by adjusting or replacing the type and size of the metal thermal sensing branches according to actual temperature measurement needs, thereby further improving the wireless temperature measurement performance.

[0010] The proposed wireless temperature sensor uses a log-periodic dipole antenna to achieve broadband linearly polarized microwave signal reception. For the log-periodic dipole antenna, a double-layer radiating dipole array is used to provide high-gain electromagnetic radiation. The substrate is made of conventional F4B board (dielectric constant 2.65, loss tangent 0.001), which is processed by printed copper plating. The feeding method is a coaxial cable, and the coaxial cable uses a standard SMA adapter (working bandwidth not less than 18 GHz) to connect to the input and output ports of the vector network analyzer and the input and output ports of the cavity filter.

[0011] Furthermore, the cavity filter cavity is processed and prepared using high-precision machining methods, with stainless steel as the material. After the cavity is processed with high precision, the surface of the cavity is gold-plated. Standard SMA adapters (with an operating bandwidth of not less than 18GHz) are used for microwave signal input and output at the input and output ports of the filter, and flanges are used for fixation. For the metal coupling columns of the filter, one is extended in the direction outside the cavity and wrapped with a metal tube while maintaining good electrical contact. At the bottom of the adjustable metal coupling column, a metal flange is used to connect to the metal thermal sensing branch wrapped in the ceramic shell. At the signal input port of the filter, the logarithmic periodic dipole antenna is loaded vertically, and the filter receives microwave signals with vertical polarization.

[0012] Furthermore, at the bottom of the filter's sliding adjustable metal coupling column, the ceramic shell uses a low thermal expansion coefficient and high-temperature resistant ceramic (not less than 2300°C) to wrap the metal thermal sensing branch; between the sliding adjustable metal coupling column and the metal thermal sensing branch, a ceramic flange structure is used for connection (the ceramic flange and the ceramic shell are processed in an integrated molding manner, and the middle is perforated to arrange the metal thermal sensing branch), and a T-shaped ceramic column is used for thermal isolation, and the fixing method is ceramic bolt connection (for closed high-temperature and high-pressure temperature measurement objects, it can be integrated with the system / device to be measured for bolting and fixing); for the metal thermal sensing branch, a flexible selection is made based on the temperature measurement limit (for example, to achieve a limit temperature of more than 1400°C, metal iron (α≈1.25E-5 / °C) and platinum (α≈9.5E-6 / °C) can be selected). This invention aims to achieve temperature measurement exceeding 1400°C, and the one used is

[0013] The material of the metal thermal induction branch is iron, and the selected specifications are 170mm in length and 0.25mm in radius;

[0014] Furthermore, after the microwave signal is tuned and frequency-selected by the filter, the logarithmic periodic dipole antenna is loaded at the microwave signal output port of the filter in a horizontal arrangement so that the tuned signal is radiated outward in a horizontally polarized manner. The two are connected using a standard SMA adapter (working bandwidth is not less than 18 GHz).

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention uses eight pairs of dipoles to form a log-periodic antenna with an operating bandwidth of 6.08 GHz and an average gain of more than 9.15 dBi within the operating frequency band. By adopting an orthogonal loading method, excellent polarization separation of microwave signal transmission and reception can be achieved, enabling wireless high-temperature measurement;

[0017] (2) The present invention adopts a rotational tilt layout design for the logarithmic periodic dipole antenna element, which reduces the radial dimension characteristics of the antenna element by about 3.5%;

[0018] (3) The present invention uses a cavity filter for microwave tuning perception, which has the characteristics of simple structure and rich narrowband;

[0019] (4) The present invention uses a metal thermal sensing branch as a temperature sensing probe and a high-temperature resistant ceramic as a shell. The temperature sensing area and the temperature feedback area are separated from each other. The wireless temperature sensor of the present invention can easily achieve high-temperature measurements exceeding 1400°C. Compared with traditional microwave temperature sensors, the temperature measurement limit is increased by more than 10%;

[0020] (5) The wireless temperature sensor of the present invention has a simple overall structure, is easily disassembled, and has strong environmental adaptability. The material and structural dimensions of the metal thermal sensing branch can be flexibly selected according to the approximate temperature range of the target to be measured, and has the characteristic of flexible adjustable temperature measurement range. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the device of the present invention.

[0022] Figure 2 Schematic diagram of the structure of the logarithmic periodic dipole broadband patch antenna in the present invention.

[0023] Figure 3 Schematic diagram of the reflection coefficient and standing wave coefficient curve of the logarithmic periodic dipole broadband patch antenna in the present invention.

[0024] Figure 4 Schematic diagram of the far-field gain of the logarithmic periodic dipole broadband patch antenna in the present invention in the operating frequency bands of 5.5 GHz, 6.0 GHz, 6.5 GHz and 7.0 GHz.

[0025] Figure 5 This is a schematic diagram of the structure of the integrated logarithmic periodic dipole broadband patch antenna and cavity filter wireless temperature sensor in the present invention.

[0026] Figure 6 Schematic diagram of the reflection coefficient and transmission coefficient curve of the cavity filter in the present invention.

[0027] Figure 7 Schematic diagram of the reflection coefficient results of the cavity filter in the present invention under different sliding adjustable metal coupling column loading states.

[0028] Figure 8 This is a schematic diagram of the thermal expansion and stretching results of the ferrous metal thermal induction branch used in the present invention under different temperature difference excitations when the initial temperature is 25°C.

[0029] Figure: 1 - vector network analyzer, 2 - log-periodic dipole transmitting antenna for vertically polarized microwave signals, 201 - dielectric substrate for log-periodic dipole antenna, 202 - top radiating element array, 203 - coaxial feed line for log-periodic dipole antenna, 204 - bottom radiating element array, 3 - log-periodic dipole receiving antenna for vertically polarized microwave signals, 4 - cavity filter, 401 - coaxial fixing flange for log-periodic dipole receiving antenna for vertically polarized microwave signals, 402 - inner conductor extension feed line for input and output coaxial lines of cavity filter, 403 - sliding adjustable metal coupling post for cavity filter , 404-cavity filter fixed metal coupling column, 405-cavity filter metal outer cavity, 406-cavity filter fixed metal coupling partition, 407-cavity filter sliding adjustable metal coupling column bottom fixing flange, 501-ceramic shell fixing flange, 502-cavity filter and ceramic shell flange ceramic fixing bolts, 503-cavity filter sliding adjustable metal coupling column and metal thermal sensing branch T-shaped ceramic isolation column, 504-metal thermal sensing branch, 6-horizontally polarized microwave signal logarithmic periodic dipole transmitting antenna, 7-horizontally polarized microwave signal logarithmic periodic dipole receiving antenna. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, a wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter includes a vector network analyzer 1 and a logarithmic periodic dipole microwave signal transmitting antenna 2 connected thereto; the logarithmic periodic dipole transmitting antenna 2 is arranged in a vertical state to radiate vertically polarized microwave signals; at the signal input end of the cavity filter is a vertically polarized microwave signal logarithmic periodic dipole receiving antenna 3, which is also loaded in a vertical state to receive vertically polarized microwave signals, completing the cavity filter feeding of the received signal; for the microwave signal from the vertically polarized microwave signal logarithmic periodic dipole receiving antenna 3, the cavity filter 4 can slide to Different loading states of the metal coupling column are adjusted to produce different tuning responses; the tuning of the cavity filter is completed through the thermal expansion of the metal thermal induction branches wrapped by the high-temperature resistant ceramic shell fixing flange 501; after the cavity filter completes the tuning of the microwave signal, the tuned microwave signal is output through the horizontally polarized microwave signal logarithmic periodic dipole transmitting antenna 6 loaded in a horizontal state; the horizontally polarized microwave signal radiated by the horizontally polarized microwave signal logarithmic periodic dipole transmitting antenna 6 will be wirelessly received by the logarithmic periodic dipole antenna 7 which is also connected to the input port of the vector network analyzer in a horizontal state, and finally the signal analysis is completed through the vector network analyzer 1 to invert and obtain the temperature information of the monitored target.

[0032] like Figure 2 As shown, the logarithmic periodic antenna 2 proposed in the present invention uses eight pairs of dipole elements as a radiating array, the length of the first element L1 = 14 mm, the element width W = 2.5 mm, the feed line width 2.0 mm, the proportional factor τ = 0.85, and the element adopts a rotation angle Ψ = 25° for structural miniaturization design; the substrate 201 uses F4B plate (dielectric constant 2.65, loss tangent 0.001) with a thickness of 1.0 mm; the top radiating element array 202 distributed along the positive direction of the y-axis is the top radiating element array, and the bottom radiating element array 204 distributed along the negative direction of the y-axis is the bottom radiating element array; the antenna transmits signals through a coaxial cable 203, wherein the top radiating element array 202 is connected to the inner conductor of the coaxial line at the first element, and the bottom radiating element array 204 is connected to the outer conductor of the coaxial line at the first element.

[0033] like Figure 3 As shown, the reflection coefficient result S11 of the logarithmic periodic dipole antenna of the present invention reflects that it has good impedance matching characteristics in the range of 3.99 GHz to 10.09 GHz, the absolute bandwidth is close to 6.1 GHz, and the relative bandwidth is about 85%, showing excellent broadband characteristics; at the same time, within the above-mentioned frequency band, the standing wave coefficient result VSWR is basically less than 2, reflecting that the logarithmic periodic dipole antenna of the present invention has low standing wave characteristics.

[0034] like Figure 4 As shown, the results are the far-field gain results of the invented logarithmic dipole antenna at frequencies of 5.5 GHz, 6.0 GHz, 6.5 GHz and 7.0 GHz. The results show that the antenna has a gain performance of 9.49 dBi at 5.5 GHz, a gain of 9.92 dBi at 6.0 GHz, a gain of 9.83 dBi at 6.5 GHz, and a gain of 9.06 dBi at 7.0 GHz. The results show the wide-band and high-gain characteristics of the logarithmic periodic dipole antenna of the present invention.

[0035] like Figure 5As shown, it is a schematic diagram of the structure of the integrated wireless temperature sensor of the present invention, wherein the vertically polarized microwave signal logarithmic periodic dipole receiving antenna 3 is a logarithmic periodic dipole antenna in a vertically loaded state, which realizes broadband reception of vertically polarized electromagnetic signals, and the received microwave signal is integrated with the cavity filter through the coaxial cable 203 and the coaxial fixed flange 401 of the vertically polarized microwave signal logarithmic periodic dipole receiving antenna, and the microwave signal is fed into the cavity filter through the coaxial inner conductor 402; the cavity filter cavity 405 adopts a rectangular cavity, and the interior of the cavity adopts a sliding adjustable metal coupling column 403 and a fixed metal coupling column 404 to provide microwave tuning, and the sliding adjustable coupling column extends outward, and the cavity filter sliding adjustable metal coupling column supports the bottom fixed flange 407, the ceramic The porcelain shell fixing flange 501, T-shaped ceramic isolation column 503 and ceramic fixing bolt 502 finally establish a sliding adjustable connection of the metal coupling column controlled by the metal thermal induction branch 504 with the metal thermal induction branch; in the initial state, the internal length of the cavity 405 of the cavity filter is 40.0 mm, the cavity width is 18.0 mm, the cavity height is 35.0 mm, the metal coupling columns 403 and 404 have a radius of 2.5 mm and a height of 28.7 mm, the feeding inner conductor 402 extends 7.0 mm in length and 0.6 mm in radius, the metal coupling columns 403 and 404 are 10 mm away from the center of the cavity in the x direction and maintain the center position in the y direction, the sliding adjustable metal branch 403 extends outward by 8.0 mm, and the tuning partition 406 is 15.0 mm in height.

[0036] Figure 6 As shown in the figure, the initial state resonant working characteristic curve of the cavity filter of the present invention is shown. According to the reflection coefficient result S11 and the transmission coefficient result S21 curve, it can be found that the cavity filter maintains four narrowband filtering results in the frequency band of 4.9GHz~6.75GHz, of which the first narrowband filtering occurs at 4.95GHz~4.96GHz and the second narrowband filtering occurs at

[0037] 5.51GHz~5.60GHz, the third narrowband filter occurs at 6.13GHz~6.16GHz, and the fourth narrowband filter occurs at

[0038] 6.49GHz~6.53GHz; According to the results, it can be seen that the cavity filter of the present invention maintains rich narrowband filtering characteristics in a wider frequency range, which provides an important basis for utilizing its rich narrowband filtering characteristics for temperature measurement.

[0039] Figure 7The following are the operating frequency responses of the cavity filter of the present invention when the height of the sliding adjustable metal coupling post 403 is increased from 26.7 mm to 30.7 mm in a sliding step size del_l = 0.4 mm. It can be seen that as the loading height of the metal sliding adjustable coupling post increases, the cavity filter experiences frequency shifts within all four filter bands. Specifically, as the height of the metal sliding adjustable coupling post increases, the filter's filter band shifts toward lower frequencies. Further analysis reveals that within the state change range del_l = 4.0 mm of the metal sliding adjustable coupling post, the first filter band experiences a frequency shift of 0.064 GHz, the second filter band experiences a frequency shift of 0.0289 GHz, the third filter band experiences a frequency shift of 0.1613 GHz, and the fourth filter band experiences a frequency shift of 0.394 GHz. The total frequency shift across the four filter bands is approximately 0.648 GHz. Obviously, the frequency tuning result of the sliding adjustable metal coupling column 4043 of the filter will eventually be presented by the vector network analyzer 1 after being output radiated via the horizontally arranged logarithmic periodic dipole antenna 6 .

[0040] Figure 8 The results of the thermal expansion and stretching of the ferrous metal thermal sensing branch 504, selected for the present invention to achieve wireless temperature measurement exceeding 1400°C, at different excitation temperature differences at an ambient temperature of 25°C, are shown. According to the theory of linear thermal expansion of metals, the thermal expansion and stretching of the metal thermal sensing branch are positively correlated with the initial length, linear expansion coefficient, and excitation temperature difference of the sensing branch. The results show that for a ferrous metal thermal sensing branch with a length of 170mm and a radius of 0.25mm, when the excitation temperature reaches 1400°C, the resulting linear expansion and stretching is close to 3.0mm (after deducting the thermal expansion effect of the ceramic housing). This result significantly regulates the state of the metal sliding adjustable coupling column 403, resulting in a frequency shift of approximately 0.499GHz in the filter.

[0041] It can be found that the present invention uses the basic physical phenomenon of metal thermal expansion to tune the working characteristics of the cavity filter, isolating the thermal sensing area and the temperature information conversion response area during operation. This gives the sensor a wireless temperature measurement capability exceeding 1400°C and an average temperature frequency deviation of 0.356MHz / °C, relying solely on the thermal response limit of the metal thermal sensing branches and high-temperature ceramics. At the same time, the logarithmic periodic antenna proposed in the present invention provides a usable bandwidth of up to 6.08GHz and an average gain of more than 9.15dBi within the working band. At the same time, the orthogonal arrangement feature ensures that the polarization separation of the wireless signal is completed during input and output. At the same time, the logarithmic periodic dipole antenna adopts a rotational tilt design, which reduces the radial dimension of the antenna element by about 3.5%. At the same time, its broadband characteristics ensure the broadband signal output of the cavity filter and the band-tuned response output performance under temperature excitation. At the same time, due to its simple structure and easy disassembly, the present invention can flexibly adjust the temperature measurement method according to actual temperature measurement needs by adjusting or replacing the type and size of the metal thermal sensing branches, thereby further improving the wireless temperature measurement performance.

Claims

1. A wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter, characterized in that: The invention comprises a vector network analyzer (1) and a vertically placed logarithmic periodic dipole microwave signal transmitting antenna (2) connected thereto; a cavity filter (4) loaded with a vertically arranged vertically polarized microwave signal logarithmic periodic dipole receiving antenna (3) and a horizontally arranged horizontally polarized microwave signal logarithmic periodic dipole transmitting antenna (6); a metal coupling column (403) is arranged inside the cavity filter (4), one of the metal coupling columns (403) being slidably adjustable, the bottom of the cavity filter (4) being connected via a metal flange, a ceramic flange and a metal thermal induction branch wrapped by a ceramic housing fixing flange (501), and a T-shaped ceramic column conduction control and thermal isolation are adopted between the slidably adjustable metal coupling column and the thermal induction branch.

2. The wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter according to claim 1, characterized in that: The logarithmic periodic antenna (2) uses dipole oscillators as a radiation array, and the antenna oscillator array uses a double-layer oscillator array. The logarithmic periodic antenna (2) includes a top-layer radiating oscillator array (202) and a bottom-layer radiating oscillator array (204). The antenna transmits signals via a coaxial cable (203), wherein the top-layer radiating oscillator array (202) is connected to the inner conductor of the coaxial line at the first oscillator, and the bottom-layer radiating oscillator array (204) is connected to the outer conductor of the coaxial line at the first oscillator.

3. The wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter according to claim 1, characterized in that: The wireless temperature sensor adopts a vertically arranged vertically polarized microwave signal logarithmic periodic dipole receiving antenna (3) and a horizontally arranged horizontally polarized microwave signal logarithmic periodic dipole transmitting antenna (6) to load the logarithmic periodic dipole antenna to realize broadband polarization separation and reception of microwave signals of the cavity filter (4), wherein the vertically polarized microwave signal logarithmic periodic dipole receiving antenna (3) is a logarithmic periodic dipole antenna in a vertically loaded state, realizing broadband reception of vertically polarized electromagnetic signals, and the received microwave signal is transmitted through a coaxial cable (203), The coaxial fixed flange (401) of the vertically polarized microwave signal logarithmic periodic dipole receiving antenna is integrally connected to the cavity filter, and the microwave signal is fed into the cavity filter through the coaxial inner conductor (402); the cavity filter cavity (405) adopts a rectangular cavity, and a sliding adjustable metal coupling column (403) and a fixed metal coupling column (404) are used inside the cavity to provide signal tuning, the sliding adjustable coupling column extends outward, and the cavity filter (4) is connected to an external temperature sensor probe through the sliding adjustable metal coupling column bottom fixed flange (407).

4. The wireless temperature sensor based on a logarithmic periodic dipole antenna and a cavity filter according to claim 3, characterized in that: The temperature sensing probe is composed of a metal thermal sensing branch (504) wrapped by a ceramic shell fixing flange (501). The temperature sensing probe establishes thermal expansion conduction control and thermal isolation with the filter sliding adjustable metal coupling column (403) through the ceramic shell fixing flange (501), the T-shaped ceramic isolation column (503) and the ceramic fixing bolt (502), and the thermal expansion conduction control and thermal isolation are controlled by the metal thermal sensing branch (504).

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