Ultra-small diameter food thermometer based on antenna and charging integration and its manufacturing method

Abstract

This application discloses an ultra-small diameter food thermometer based on antenna and charging integration and its manufacturing method, relating to the field of wireless thermometer technology. The ultra-small diameter food thermometer includes a metal needle tube, a ceramic connecting shaft, a metal tube, a metal handle, and an ambient temperature sensor. A PCBA board is built into the metal needle tube, and the PCBA board has a charging positive electrode spring, a grounding spring, and an antenna feed spring. The ceramic connecting shaft is fixed to one end of the PCBA board. The metal tube is connected to the metal handle, and the antenna feed spring, grounding spring, metal tube, and metal handle form an impedance matching feed structure based on the inverted-F antenna principle. The metal tube and metal handle simultaneously serve as the ground for the antenna and charging circuit. The ambient temperature sensor is located at the end of the metal tube, and its wiring is only connected to the temperature measurement circuit of the PCBA board and does not participate in the radio frequency functional structure. This application provides an ultra-small diameter food thermometer with high detection accuracy and a high degree of matching in its slender structure.

Description

Technical Field

[0001] This application relates to the field of wireless thermometer technology, and in particular to an ultra-small diameter food thermometer based on antenna and charging integration and its manufacturing method. Background Technology

[0002] In the food processing industry, food thermometers are crucial devices for temperature measurement. With technological advancements and continuous progress in wireless communication and portable electronic devices, people's functional demands for food thermometers are becoming increasingly diverse. Users not only expect accurate temperature measurement but also wireless transmission of temperature data, along with excellent portability and battery life. This makes integrating antenna structures and charging functions into food thermometers an inevitable development trend, greatly facilitating real-time monitoring and control of food temperature during cooking.

[0003] Currently, existing food thermometers primarily employ an antenna design principle of "inner shell + outer shell metal segment forming a coaxial transmission waveguide" to integrate the antenna and charging. On one hand, the inner shell, sensor wiring, or ambient thermal sensor are incorporated as components of the antenna to transmit radio frequency signals. Through the synergistic effect of these components, temperature data is converted into radio frequency signals for wireless transmission. On the other hand, in integrating the charging function with the antenna, charging signals are transmitted via electrical connections between charging contacts and the antenna / inner shell. This requires additional filtering components to separate the charging signal from the radio frequency signal, thus preventing interference between the two types of signals. Furthermore, some existing technologies also incorporate ambient thermal sensors or their wiring into the antenna structure, or indirectly detect ambient temperature through antenna heat conduction.

[0004] However, existing technologies have significant drawbacks. This design, relying on a "coaxial waveguide," requires multiple components, including an inner shell, outer metal segments, and sensor wiring, to form the antenna structure. This results in extremely low space utilization within the slender body of a miniaturized food thermometer and significantly increases assembly difficulty. Furthermore, the transmission of charging and radio frequency signals requires separation using filtering components. These additional filtering elements not only increase hardware costs and circuit design complexity but also easily cause signal loss during the filtering process, thus affecting radio frequency transmission efficiency and charging stability. Additionally, using an ambient thermal sensor or its wiring as part of the antenna, or indirectly measuring temperature through antenna heat conduction, can interfere with the sensor's detection accuracy, leading to discrepancies between the food temperature and ambient temperature readings, and failing to provide users with accurate temperature information. Simultaneously, the existing antenna carrier is not well-suited to the slender structure of the food thermometer, making it difficult to balance portability and the practicality of temperature measurement while ensuring radio frequency performance. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art and provide a food thermometer with high detection accuracy and high matching degree of slender structure, this application provides an ultra-small diameter food thermometer based on antenna and charging integration and a manufacturing method thereof.

[0006] Firstly, the objective of this invention is achieved through the following technical solution: An ultra-small diameter food thermometer based on antenna and charging integration includes: a metal needle tube, a ceramic connecting shaft, a metal tube, a metal handle, and an ambient temperature sensor. The metal needle tube has a built-in PCBA board, which is equipped with a temperature sensor, a charging positive electrode spring, a grounding spring and an antenna feed point spring. The ceramic connecting shaft is fixedly connected to the end of the PCBA board away from the metal needle tube; The metal tube is connected to the metal handle, and the antenna feed point spring, the grounding spring, the metal tube, and the metal handle together constitute an impedance matching feed structure based on the inverted F antenna principle. The metal tube and the metal handle simultaneously serve as the antenna and the ground for the charging circuit. The ambient temperature sensor is located at the end of the metal handle, and the wiring is only connected to the temperature measurement circuit of the PCBA board and does not participate in the radio frequency functional structure. It also includes a ceramic isolation tube, the ceramic connecting shaft being used to isolate the electrical conduction between the PCBA board and the metal needle tube, and between the metal tube and the metal handle; the ambient temperature sensor is built into the ceramic isolation tube, the ceramic isolation tube being fixed to the end of the metal tube and maintaining a preset distance from the metal tube and the metal handle.

[0007] By adopting the above technical solution, this invention uses the inverted-F antenna principle, with a metal tube and metal handle as the core radiators, simplifying the antenna design structure, reducing design and assembly complexity, improving internal space utilization, and adapting to miniaturized body designs. The extended section of the metal tube and the metal handle simultaneously serve as the ground electrode of the charging circuit and form an electrical connection with the grounding spring. The electrical structure of the inverted-F antenna naturally enables the transmission of charging and radio frequency signals. The radio frequency module is turned off and inactive during charging, avoiding signal interference in terms of timing. It eliminates the need for dedicated filtering components to separate charging and radio frequency signals, reducing hardware costs and signal loss, and improving radio frequency transmission efficiency and charging stability. The ambient temperature sensor is located at the end of the metal tube, and its wiring is only connected to the temperature measurement circuit on the PCBA board and does not participate in the radio frequency functional structure of the metal tube and metal handle. Simultaneously, this application sets an RC low-pass filter circuit (such as an RC low-pass filter) at the signal input end of the temperature measurement circuit. The RC low-pass filter circuit can effectively attenuate high-frequency radio frequency energy coupled into the temperature measurement circuit from the surrounding space, ensuring the purity of the ambient temperature detection signal and achieving electrical isolation between the temperature measurement function and the radio frequency function at the hardware level. This avoids interference from radio frequency signals to the sensor and improves the accuracy of temperature detection.

[0008] This application utilizes a ceramic connecting collar to isolate the electrical conduction between the metal needle tube and the metal handle, thereby avoiding electrical interference and ensuring the stability of the device's electrical performance. By embedding the ambient temperature sensor inside the ceramic isolation tube and maintaining a preset distance between it and the metal tube and the metal handle, the radio frequency structure of the ambient temperature sensor and the metal tube can be completely separated, avoiding interference from radio frequency signals on the sensor's detection accuracy and improving the accuracy of food temperature and ambient temperature detection data.

[0009] In a preferred embodiment of this application: the ambient temperature sensor abuts against the inner wall of the metal handle; the metal tube and the metal handle are detachably connected by threads or formed as an integral structure by welding.

[0010] By adopting the above technical solution, the metal tube and the metal handle can be detachably connected by threads or formed into an integral structure by welding, which facilitates the assembly and disassembly of the equipment and makes it convenient to maintain and replace parts.

[0011] In a preferred embodiment of this application, the impedance matching characteristics of the inverted-F antenna are adapted to cover the target radio frequency band by adjusting the position of the antenna feed spring on the PCBA board and / or the physical length of the metal tube and the metal handle.

[0012] By adopting the above technical solution, in practical applications, the impedance matching characteristics of the inverted F antenna can be adapted by adjusting the position of the antenna feed point spring on the PCBA board and / or the physical length of the metal tube and metal handle according to the requirements of the target radio frequency band, so as to realize the radio frequency signal transmission of the target frequency band and improve the flexibility and applicability of the radio frequency function of the food thermometer.

[0013] In a preferred embodiment of this application: the outer surface of the metal tube extends axially and forms a continuous conductive path with the metal handle; the inner diameter of the metal handle is adapted to the diameter of the ambient temperature sensor probe, and the end of the pin of the ambient temperature sensor is in close contact with the inner wall of the metal handle to sense the temperature.

[0014] By adopting the above technical solution and using the inverted-F antenna principle, with a metal tube and metal handle as the core radiator, the antenna structure is formed without relying on components such as inner shell, outer shell metal segments, and sensor wiring. This significantly reduces the design and assembly complexity of the antenna, improves the utilization rate of the internal space of the food thermometer, and is suitable for miniaturized body design. The metal tube and metal handle simultaneously serve as the radiator of the inverted-F antenna and the ground electrode of the charging circuit. The electrical structure of the inverted-F antenna naturally enables the transmission of charging signals and radio frequency signals. This application achieves mutual exclusion of the working timing of the radio frequency communication module and the charging management module: when the device is in charging state, the radio frequency communication function is forcibly disabled; conversely, when the device is performing wireless data communication, the charging function is inactive. Since the charging signal and the radio frequency (RF) signal will not coexist on the shared metal tube and metal handle conductor in the time dimension, mutual interference between the two is fundamentally avoided. Electromagnetic compatibility of the system can be guaranteed without the introduction of additional filtering components, reducing hardware costs and signal loss, and improving RF transmission efficiency and charging stability. The ambient temperature sensor serves only as a temperature measuring element and is completely separated from the RF structure of the metal tube, avoiding RF signal interference to the sensor and ensuring the accuracy of food temperature and ambient temperature detection data. Using the extension of the metal tube and the metal handle as antenna carriers is highly compatible with the slender body of the food thermometer, ensuring RF performance without affecting the portability and normal temperature measurement function, thus balancing practicality and RF transmission effect. The metal tube and metal handle form a continuous conductive path, optimizing the electrical performance of the inverted-F antenna and improving RF signal transmission efficiency. The ambient temperature sensor pins are in close contact with the inner wall of the metal handle to sense temperature, enabling more accurate detection of ambient temperature.

[0015] In a preferred embodiment of this application: the charging positive electrode spring is disposed on the inner side wall of the metal needle tube, and the grounding spring forms a circuit with the metal handle through the metal tube to ground.

[0016] By adopting the above technical solution, the positive charging electrode spring is set on the inner wall of the metal needle tube, and the negative charging circuit is grounded through the metal tube and the metal handle, so that the entire charging path is distributed along the axial direction of the device and the structure is compact. At the same time, the metal shell is used as the charging ground electrode, which simplifies the internal wiring, reduces the PCBA area, and helps to realize the ultra-small diameter design of the overall food thermometer with an outer diameter ≤6 mm.

[0017] In a preferred embodiment of this application, the metal tube extension and the metal handle together constitute the radiating arm of the inverted-F antenna and are connected to the ground electrode of the PCBA board.

[0018] By adopting the above technical solution, the structural design of the inverted F antenna is optimized. The ground pole is constructed by using a metal tube and a metal handle, and the extension of the metal tube and the metal handle serve as the radiating arms of the inverted F antenna. This improves the antenna's radiation performance and stability, ensures efficient transmission of radio frequency signals, and thus enhances the wireless communication capability of the food thermometer.

[0019] In a preferred embodiment of this application: the antenna feed spring is electrically connected to the radio frequency module of the PCBA board via a conductive trace; the reduced diameter section at the end of the PCBA board is inserted into the metal tube, such that the grounding spring and the antenna feed spring abut against the inner wall of the metal tube; the grounding spring is connected to the grounding terminal of the PCBA board.

[0020] By adopting the above technical solution, an electrical connection is established between the antenna feed spring and the RF module of the PCBA board, ensuring that the RF signal can be transmitted from the RF module to the antenna. The reduced diameter section at the end of the PCBA board is inserted into the metal tube, allowing the grounding spring and the antenna feed spring to abut against the inner wall of the metal tube, ensuring stable transmission of charging and RF signals. The grounding spring is connected to the ground terminal of the PCBA board, improving the circuit connection. Combined with the impedance matching feed structure based on the inverted F antenna principle and the design of the metal tube as the ground electrode of the charging circuit, the antenna design structure is further simplified, achieving efficient integration of charging and antenna, and ensuring the stability of RF and charging signal transmission.

[0021] In a preferred embodiment of this application, the outer diameter of the metal needle tube is no greater than 6 mm, and the overall structure is a slender cylindrical shape.

[0022] By adopting the above technical solution, an ultra-small diameter food thermometer is provided, allowing it to be easily inserted into various foods such as steaks, poultry, and baked goods to measure their core temperature, meeting food safety and cooking accuracy requirements. Furthermore, this invention optimizes the adaptability of structure and function, ensuring the antenna structure perfectly matches the slender body of the food thermometer, guaranteeing radio frequency performance without compromising portability or the normal operation of the temperature measurement function.

[0023] Secondly, the objective of this invention is achieved through the following technical solution: A method for manufacturing an ultra-small diameter food thermometer includes the following steps: Insert the PCBA board into the inner cavity of the metal needle tube, so that the detection end of the food temperature sensor is positioned at the tip of the metal needle tube, and the antenna feed point spring, the charging positive electrode spring and the grounding spring are in the preset electrical contact position. One end of the ceramic connecting shaft is pressed tightly into the tail end of the metal needle tube, and the other end is connected to the front end of the metal tube, and then cured to form an insulating and sealed structure. Insert the reduced diameter section of the PCBA board into the inner hole of the metal tube, so that the grounding spring contact elastically abuts against the inner wall of the metal tube to form a conductive path, and align the antenna feed spring contact with the feed interface area of ​​the metal tube. The metal handle is threaded or welded to the rear end of the metal tube, and the metal tube is fixed to the end of the metal handle, so that the metal tube and the metal handle together constitute the radiator of the inverted F antenna. The antenna feed point spring, the ground spring, the metal tube and the metal handle form an impedance-matched radio frequency feed path. The ambient temperature sensor is embedded in the end cavity of the metal handle by using a ceramic isolation tube, so that the lead of the ambient temperature sensor is only connected to the temperature measurement circuit on the PCBA board, and is completely isolated from the metal tube in terms of structure and electricity.

[0024] By adopting the above technical solution, an ultra-small diameter food thermometer with an integrated antenna and charging circuit design based on the inverted-F antenna principle is manufactured, improving the utilization rate of the internal space of the food thermometer and adapting to the miniaturized body design; it achieves efficient integration of charging and antenna, and naturally realizes the transmission of charging signals and radio frequency signals through the electrical structure of the inverted-F antenna. This application realizes the mutual exclusion of the working timing of the radio frequency communication module and the charging management module through control logic: when the device is in charging state, the radio frequency communication function is forcibly disabled; conversely, when the device is conducting wireless data communication, the charging function is inactive. Since the charging signal and the radio frequency signal will not exist simultaneously on the shared metal tube and metal handle conductor in the time dimension, the mutual interference between the two is fundamentally avoided. Electromagnetic compatibility of the system can be guaranteed without the introduction of additional filtering components, reducing hardware costs and signal loss, improving radio frequency transmission efficiency and charging stability; it also improves temperature detection accuracy, and the ambient temperature sensor is structurally and electrically isolated from the metal tube.

[0025] In summary, this application has the following three beneficial technical effects: 1. The antenna design structure is simplified by adopting the inverted F antenna principle. The metal tube and metal handle are used as the core radiators. There is no need to rely on the inner shell, outer shell metal section and sensor wiring to form the antenna structure. This reduces the complexity of antenna design and assembly, improves the utilization rate of the internal space of the food thermometer, and is suitable for miniaturized body design. 2. Achieve efficient integration of charging and antenna. The metal tube and metal handle simultaneously serve as the radiator of the inverted F antenna and the ground electrode of the charging circuit. The electrical structure of the inverted F antenna naturally enables the transmission of charging signals and radio frequency signals. The radio frequency module is turned off and does not work during the charging state, avoiding signal interference from the working timing. There is no need to set up a dedicated filtering component to separate the charging signal and radio frequency signal, reducing hardware costs and signal loss, and improving radio frequency transmission efficiency and charging stability. 3. Improve temperature detection accuracy. The ambient temperature sensor is used only as a temperature measuring element and is completely separated from the radio frequency structure of the metal tube and metal handle. Radio frequency interference is completely isolated from the wiring and hardware circuit. An RC filter is added to the signal input end of the temperature measuring circuit to suppress high frequency coupling and ensure the accuracy of food temperature and ambient temperature detection data. Attached Figure Description

[0026] Figure 1 This is an overall structural diagram of an ultra-small diameter food thermometer based on antenna and charging integration in one embodiment of this application; Figure 2 This is an overall cross-sectional view of an ultra-small diameter food thermometer based on antenna and charging integration in one embodiment of this application; Figure 3 This is an exploded view of the structure of an ultra-small diameter food thermometer based on antenna and charging integration in one embodiment of this application; Figure 4 This is a schematic diagram of an inverted-F antenna for an ultra-small diameter food thermometer based on antenna and charging integration in one embodiment of this application.

[0027] Explanation of reference numerals in the attached figures: 1. Metal needle tube; 2. Ceramic connecting shaft; 3. Metal tube; 4. Metal handle; 5. Ceramic isolation tube; 6. Ambient temperature sensor; 7. PCBA board; 71. Charging positive electrode spring; 72. Grounding spring; 73. Antenna feed spring; 74. Battery. Detailed Implementation

[0028] The following is in conjunction with the appendix Figures 1-4 This application will be described in further detail.

[0029] In one embodiment, such as Figures 1 to 3As shown, this application discloses an ultra-small diameter food thermometer based on antenna and charging integration, including a metal needle tube 1, a ceramic connecting shaft 2, a metal tube 3, a metal handle 4, a ceramic isolation tube 5, and an ambient temperature sensor 6. The metal needle tube 1 has a built-in PCBA board 7. The PCBA board 7 is equipped with a battery 74, a temperature sensor, a charging positive electrode spring 71, a grounding spring 72, and an antenna feed spring 73. The charging positive electrode spring 71, the grounding spring 72, and the antenna feed spring 73 are respectively arranged in symmetrical metal spring structures at intervals at both ends of the PCBA board 7. The ceramic connecting shaft 2 is fixedly connected to the end of the PCBA board 7 away from the metal needle tube 1.

[0030] Metal tube 3 is connected to metal handle 4; antenna feed spring 73, ground spring 72, metal tube 3, metal handle 4, and the ground of PCBA board 7 together constitute an impedance matching feed structure based on the inverted-F antenna principle. Metal tube 3 and metal handle 4 simultaneously serve as the ground electrode of the charging circuit and are electrically connected to ground spring 72. Ambient temperature sensor 6 is located at the end of metal handle 4, and its wiring is only connected to the temperature measurement circuit of PCBA board 7 and does not participate in the radio frequency functional structure of metal tube 3 and metal handle 4. At the same time, this application sets an RC low-pass filter circuit on the signal input terminal of the temperature measurement circuit to filter the high-frequency signal coupled to the circuit board by spatial radiation, further eliminating the influence of high-frequency coupling on ambient temperature detection, and realizing electrical isolation between the temperature measurement circuit and radio frequency interference from a hardware perspective. This achieves the beneficial effects of simplifying antenna design, improving charging and antenna integration effect, improving temperature detection accuracy, and adapting to product structure. This invention abandons the traditional complex antenna design, adopts the inverted-F antenna principle, and uses simple structures such as metal tube 3 and metal handle 4 to realize radio frequency signal transmission and charging functions. Moreover, the ambient temperature sensor 6 is independent of the antenna structure, avoiding interference.

[0031] This embodiment naturally achieves the transmission of charging and radio frequency (RF) signals using the electrical structure of the inverted-F antenna. The RF module is off and inactive during charging, avoiding signal interference in terms of timing and eliminating the need for dedicated filtering components to separate the charging and RF signals. This is because the charging signal is DC or low-frequency pulsation (typically <100 kHz), while the RF communication signal frequency is higher than 400 MHz, resulting in a frequency gap of several orders of magnitude. During charging, both the entire device and the RF module are off, ensuring that charging and RF functions do not operate simultaneously, thus completely avoiding signal conflicts in terms of timing. During normal operation (not charging), based on the impedance matching structure of the inverted-F antenna, the connection between the radiator and ground is only used for impedance adjustment. RF energy is confined to the antenna radiation path by the matching network and will not be conducted to the charging circuit or temperature measurement system. Simultaneously, the antenna structure extends into the metal needle tube 1. To prevent the metal needle tube 1 from forming a closed resonant cavity, a capacitor is placed at the charging positive electrode spring 71 to discharge the high-frequency resonant current coupled to the metal needle tube 1 to ground, eliminating resonance interference. Therefore, even though the metal tube 3 and the metal handle 4 are used as conductors, natural isolation can be achieved in three aspects: timing, structural matching, and resonance suppression, without the need to set up a dedicated filtering component for separating the charging signal and the radio frequency signal.

[0032] Specifically, the metal needle tube 1 is a slender cylindrical structure made of metal, possessing a certain strength and corrosion resistance. The function of the metal needle tube 1 is to protect the internal PCBA board 7 and components such as the battery 74 on the PCBA board 7, and it can also serve as part of the charging circuit. In some special applications, the metal needle tube 1 can also be made of other materials such as alloys to meet different requirements. The PCBA board 7 is housed inside the metal needle tube 1. The temperature sensor is used to detect the temperature of the food and can employ common temperature detection elements such as thermocouple sensors and thermistor sensors. The charging positive electrode spring 71 and the grounding spring 72 are electrically connected to the positive and negative terminals of the battery 74, respectively, for transmitting charging signals. The antenna feed spring 73 forms an impedance-matched feed structure with the metal tube 3 and the metal handle 4 to achieve radio frequency signal transmission. The PCBA board 7 is fixed together with these components by welding or other methods to ensure stable electrical connections between them.

[0033] The ceramic connecting shaft 2 is an insulating component that is fixedly connected to the end of the PCBA board 7 away from the metal needle tube 1. Made of ceramic material, the ceramic connecting shaft 2 possesses excellent insulation and high-temperature resistance properties, achieving electrical isolation between the PCBA board 7 and the metal needle tube 1 to prevent current leakage and interference. In practical applications, the ceramic connecting shaft 2 can be fixedly connected to the PCBA board 7 and the metal needle tube 1 by means of adhesive bonding or mechanical clamping.

[0034] Metal tube 3 and metal handle 4 are connected and together form the radiator of the inverted-F antenna. Metal tube 3 is made of metal tubing and has good conductivity. Metal handle 4 is also made of conductive metal and is tightly connected to metal tube 3. The antenna feed point spring 73, together with metal tube 3 and metal handle 4, forms an impedance matching feed structure. By adjusting the position of the antenna feed point on PCBA board 7 and the length of metal tube 3, the impedance matching parameters of the inverted-F antenna can be adapted to achieve efficient RF signal transmission. The connection between metal tube 3 and metal handle 4 can be achieved by threaded connection or by welding to form an integral structure, improving the stability and integrity of the structure.

[0035] like Figure 2 and Figure 4 As shown, the inverted-F antenna structure includes: a feed point (provided by the antenna feed point spring 73 or a solder joint), a short-circuit point (formed by the connection interface between the metal tube 3 and the metal handle 4), and a radiating arm (composed of the free extension section of the metal tube 3 and the metal handle 4). The short-circuit point connects the near end of the metal tube 3 to the ground plane (composed of the grounding electrode of the PCBA board 7) with low impedance. The feed point is located between the short-circuit point and the end of the radiating arm, and impedance matching, such as 50Ω, is achieved by adjusting its distance from the short-circuit point. Preferably, the grounding spring 72 and the antenna feed point spring 73 can be fabricated using either springs or solder joints. That is, the fabrication method of the grounding spring 72 and the antenna feed point spring 73 can be freely and as needed selected.

[0036] The outer surface of the metal tube 3 extends axially and forms a continuous conductive path with the conductive material of the metal handle 4 to ensure stable transmission of radio frequency signals and charging signals. The inner diameter of the metal handle 4 is adapted to the probe diameter of the ambient temperature sensor 6, and the pin ends of the ambient temperature sensor 6 are in close contact with the inner wall of the metal handle 4 to sense the temperature, thereby improving the sensitivity of temperature detection.

[0037] The ceramic connecting shaft 2 is used to isolate the electrical conduction between the metal tube 3 and the metal handle 4. The ceramic isolation tube 5 improves the installation stability of the ambient temperature sensor 6 and ensures electrical isolation between the ambient temperature sensor 6 and the metal components.

[0038] An ambient temperature sensor 6 is located at the end of the metal handle 4. In this embodiment, a common negative temperature coefficient thermistor is used. The ambient temperature sensor 6 is built into a ceramic isolation tube 5, which is fixed to the end of the metal tube 3 and maintains a preset distance from the metal tube 3 and the metal handle 4. This isolates and fixes the ambient temperature sensor 6 from the metal tube and the metal handle 4, preventing interference from radio frequency signals. The wiring of the ambient temperature sensor 6 is only connected to the temperature measurement circuit on the PCBA board 7 and does not participate in the radio frequency functional structure. It is only used to detect the ambient temperature. At the same time, this application sets an RC low-pass filter circuit at the signal input terminal of the temperature measurement circuit to filter the high-frequency signals coupled to the circuit board by spatial radiation, further eliminating the influence of high-frequency coupling on the ambient temperature detection. This achieves complete isolation between the temperature measurement circuit and radio frequency interference in hardware, ensuring the accuracy of temperature detection.

[0039] There are several options for connecting the metal tube 3 and the metal handle 4. These include threaded detachable connections and welding. In another embodiment, the metal tube 3 and the metal handle 4 can be connected using a common snap-fit ​​connection. Snap-fit ​​connections include snap-fit ​​protrusions on the metal tube 3 and snap-fit ​​grooves on the metal handle 4; these will not be elaborated upon further here.

[0040] The positive charging contact 71 is located on the inner wall of the metal needle tube 1, and the grounding contact 72 forms a grounding loop with the metal tube 3 and the metal handle 4. Furthermore, the antenna structure extends into the metal needle tube 1. To prevent the metal needle tube 1 from forming a closed resonant cavity and causing high-frequency resonance interference, a capacitor is connected in parallel at the positive charging contact 71. This discharges the high-frequency resonant current coupled from the antenna to the metal needle tube 1 to the ground terminal, cutting off the resonant current path within the metal needle tube 1. Structurally, this eliminates the problem of the metal needle tube 1 forming a closed resonant cavity, ensuring that the radio frequency radiation is only controlled by the inverted-F antenna body, improving the antenna's operational stability, and making the charging circuit simpler without the need for additional complex wiring. In the inverted-F antenna structure, the extended section of the metal tube 3 and the metal handle 4 serve as the radiating arms of the inverted-F antenna and are connected to the ground electrode of the PCBA board 7, further optimizing the antenna's performance.

[0041] The antenna feed spring 73 is electrically connected to the RF module of the PCBA board 7 via conductive traces, ensuring accurate transmission of RF signals. In actual design, the antenna feed spring 73 and the ground spring 72 are spaced apart at one end of the PCBA board 7 near the ceramic connecting shaft 2. The antenna feed spring 73 can be positioned between the charging positive spring 71 and the ground spring 72, or the ground spring 72 can be positioned between the charging positive spring 71 and the antenna feed spring 73. The tapered section at the end of the PCBA board 7 is inserted into the metal tube 3, causing the ground spring 72 and the antenna feed spring 73 to abut against the inner wall of the metal tube 3. The ground spring 72 is connected to the ground terminal of the PCBA board 7, ensuring the stability of the electrical connection.

[0042] The outer diameter of the metal needle tube 1 is no more than 6 mm, and the overall structure is a slender cylinder, which makes the food thermometer adaptable to more application scenarios, such as inserting it into small food items for temperature detection, and also improves the portability of the device; in another embodiment, those skilled in the art can set the outer diameter of the metal needle tube 1 to be larger according to actual needs.

[0043] In a preferred embodiment, the metal needle tube 1 has an outer diameter of 5 mm or less and an inner diameter of 4.5 mm; it is made of SUS304 stainless steel; the food thermometer operates in the 2.40–2.48 GHz ISM band, at which point the length of the metal tube 3 and the metal handle 4 is approximately 0.9 times the quarter wavelength of the ISM band to compensate for end effects. The ceramic connecting shaft 2 is made of alumina ceramic to ensure structural stability and no high-frequency loss under high-temperature cooking conditions.

[0044] The implementation principle of this embodiment of an ultra-small diameter food thermometer based on integrated antenna and charging is as follows: This food thermometer adopts the inverted-F antenna principle, using the metal tube 3 and metal handle 4 as the core radiators, significantly reducing the design and assembly complexity of the antenna and making it more suitable for miniaturized designs. The metal tube 3 and metal handle 4 simultaneously serve as the radiators of the inverted-F antenna and the ground electrode of the charging circuit. The electrical structure of the inverted-F antenna naturally enables the transmission of charging and radio frequency signals. In this application, the radio frequency module is turned off during charging, avoiding signal interference in terms of timing. There is no need to set up a dedicated filtering component to separate the charging and radio frequency signals, reducing hardware costs and signal loss, and improving radio frequency transmission efficiency and charging stability. The ambient temperature sensor 6 serves only as an independent temperature measuring element, completely separated from the radio frequency structure of the metal tube 3. Using the extension of the metal tube 3 and the metal handle 4 as the antenna carrier ensures radio frequency performance without affecting the portability and normal temperature measurement function of the device, balancing practicality and radio frequency transmission effect.

[0045] In another embodiment, this application also discloses a method for manufacturing an ultra-small diameter food thermometer, comprising the following steps: S1: Insert PCBA board 7 into the inner cavity of metal needle tube 1, so that the detection end of food temperature sensor is positioned at the tip of metal needle tube 1, and the antenna feed point spring 73, charging positive electrode spring 71 and grounding spring 72 are in the preset electrical contact position.

[0046] Specifically, the PCBA board 7, after component mounting and reflow soldering, is inserted axially into the inner cavity of a stainless steel metal needle tube 1 with an outer diameter of approximately 5.0 mm. The detection end of the food temperature sensor (such as an NTC thermistor) is precisely positioned against the tip of the metal needle tube 1, with the axial positioning error controlled within ±0.15 mm. The PCBA board 7 has a charging positive electrode spring 71, a grounding spring 72, and an antenna feed point spring 73 on both sides, all of which are made of phosphor bronze and pre-bent into an elastic arch structure. After insertion, the charging positive electrode spring 71 forms a surface contact with the inner wall of the metal needle tube 1, forming a charging positive electrode path. The grounding spring 72 and the antenna feed point spring 73 do not contact the metal needle tube 1 temporarily, and are reserved for subsequent docking with the metal tube 3. To enhance heat conduction efficiency, a thermally conductive silicone pad with a thickness of approximately 0.3 mm is wrapped around the outer periphery of the PCBA board 7, and its axial position within the metal needle tube 1 can also be fixed by dispensing adhesive.

[0047] S2: Press one end of the ceramic connecting shaft 2 tightly into the tail end of the metal needle tube 1, and connect the other end to the front end of the metal tube 3, and solidify to form an insulating and sealed structure.

[0048] Specifically, high-temperature resistant epoxy adhesive is uniformly coated on the mating surfaces of the ceramic connecting shaft 2 and the metal needle tube 1. One end of the ceramic connecting shaft 2 is pressed into the tail end of the metal needle tube 1 by a servo press with a constant pressure of 50 N, and the interference is controlled at 0.03–0.05 mm. This effectively blocks the DC and RF paths between the ground terminal of the PCBA board 7 and the tail end of the metal needle tube 1, avoiding the formation of parasitic loops.

[0049] S3: Insert the reduced diameter section of PCBA board 7 into the inner hole of metal tube 3, so that the grounding spring 72 elastically abuts against the inner wall of metal tube 3 to form a conductive path, and align the antenna feed point spring 73 with the feed interface area of ​​metal tube 3.

[0050] Specifically, the PCBA board 7 has a reduced diameter section at its end, with a length of 8 mm and an outer diameter reduction of 0.4 mm. The reduced diameter section is inserted into the central through hole of the metal tube 3. During the insertion process, the grounding spring 72 is elastically deformed and tightly adheres to the inner wall of the metal tube 3, forming a low-impedance conductive path, which serves as the ground electrode of the charging circuit. At the same time, the antenna feed spring 73 is precisely aligned with the preset feed interface area on the metal tube 3 (i.e., near the short-circuit point of the inverted F antenna), and the distance between the two is controlled at 1.5 ± 0.2 mm to meet the impedance matching requirements in the 2.4 GHz band.

[0051] S4: Thread or weld the metal handle 4 to the rear end of the metal tube 3, and fix the metal tube 3 to the end of the metal handle 4, so that the metal tube 3 and the metal handle 4 together form the radiator of the inverted F antenna, wherein the antenna feed point spring 73, the ground spring 72, the metal tube 3 and the metal handle 4 form an impedance-matched radio frequency feed path.

[0052] Specifically, the metal handle 4 is made of brass or stainless steel and is screwed into the external thread at the rear end of the metal tube 3; the metal tube 3 is fixed to the inner hole at the far end of the metal handle 4 by press-fitting or laser welding; after assembly, the metal tube 3 and the metal handle 4 serve as radiating arms, and the grounding electrode of the PCBA board 7 forms the grounding plate, forming a complete inverted F antenna structure; the radio frequency signal is fed from the radio frequency module of the PCBA board 7 through the antenna feed point spring 73, and conducted through the metal tube 3 to the near end of the metal handle 4 to achieve efficient radiation.

[0053] S5: The ambient temperature sensor 6 is embedded in the end cavity of the metal handle 4 through the ceramic isolation tube 5, so that the lead of the ambient temperature sensor 6 is only connected to the temperature measuring circuit on the PCBA board 7, and is completely isolated from the metal tube 3 in terms of structure and electricity.

[0054] Specifically, the ambient temperature sensor 6 uses a negative temperature coefficient thermistor, such as a 0402 package, which is pre-soldered to a flexible lead. The ambient temperature sensor 6 is installed in a ceramic isolation tube 5 with an outer diameter of 3.8 mm and an inner diameter of 1.2 mm, and the tube opening is filled with thermally conductive insulating glue. Then, the ceramic isolation tube 5 is pressed into the inner cavity of the end of the metal handle 4 to a depth of 5 mm, so that it does not directly contact the inner wall of the metal handle 4. The lead of the ambient temperature sensor 6 passes through the central channel of the metal tube 3 and is finally soldered to a dedicated temperature measuring pad on the PCBA board 7. The entire wiring path avoids the radio frequency trace area.

[0055] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0056] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. An ultra-small diameter food thermometer based on antenna and charging integration, characterized in that, include: Metal needle (1), ceramic connecting shaft (2), metal tube (3), metal handle (4) and ambient temperature sensor (6); The metal needle tube (1) has a built-in PCBA board (7), and the PCBA board (7) is equipped with a temperature sensor, a charging positive electrode spring (71), a grounding spring (72) and an antenna feed point spring (73); The ceramic connecting shaft (2) is fixedly connected to one end of the PCBA board (7) away from the metal needle tube (1); The metal tube (3) is connected to the metal handle (4). The antenna feed point spring (73), the grounding spring (72), the metal tube (3), and the metal handle (4) together constitute an impedance matching feed structure based on the inverted F antenna principle. The metal tube (3) and the metal handle (4) simultaneously serve as the antenna and the ground for the charging circuit; The ambient temperature sensor (6) is located at the end of the metal handle (4), and the wiring is only connected to the temperature measurement circuit of the PCBA board (7) and does not participate in the radio frequency function structure. It also includes a ceramic isolation tube (5), the ceramic connecting shaft (2) is used to isolate the electrical conduction between the PCBA board (7) and the metal needle tube (1), the metal tube (3) and the metal handle (4); the ambient temperature sensor (6) is built into the ceramic isolation tube (5), the ceramic isolation tube (5) is fixed to the end of the metal tube (3) and maintains a preset distance from the metal tube (3) and the metal handle (4).

2. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 1, characterized in that, The ambient temperature sensor (6) abuts against the inner wall of the metal handle (4); the metal tube (3) and the metal handle (4) are detachably connected by threads or formed as an integral structure by welding.

3. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 1, characterized in that, The impedance matching characteristics of the inverted F antenna are adapted by adjusting the position of the antenna feed point spring (73) on the PCBA board (7) and / or the physical length of the metal tube (3) and the metal handle (4) to cover the target radio frequency band.

4. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 2, characterized in that, The outer surface of the metal tube (3) extends axially and forms a continuous conductive path with the metal handle (4); the inner diameter of the metal handle (4) is adapted to the probe diameter of the ambient temperature sensor (6), and the pin end of the ambient temperature sensor (6) is in close contact with the inner wall of the metal handle (4) to sense the temperature.

5. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 2, characterized in that, The charging positive electrode spring (71) is disposed on the inner side wall of the metal needle tube (1), and the grounding spring (72) forms a circuit with the metal handle (4) through the metal tube (3) to ground.

6. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 5, characterized in that, The extension of the metal tube (3) and the metal handle (4) together constitute the radiating arm of the inverted F antenna and are connected to the ground electrode of the PCBA board (7).

7. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 1, characterized in that, The antenna feed spring (73) is electrically connected to the radio frequency module of the PCBA board (7) through a conductive trace; the reduced diameter section at the end of the PCBA board (7) is inserted into the metal tube (3), so that the grounding spring (72) and the antenna feed spring (73) abut against the inner wall of the metal tube (3); the grounding spring (72) is connected to the grounding terminal of the PCBA board (7).

8. The ultra-small diameter food thermometer based on antenna and charging integration according to claim 1, characterized in that, The outer diameter of the metal needle tube (1) is no more than 6 mm, and the overall structure is a slender cylindrical shape.

9. A method for manufacturing an ultra-small diameter food thermometer, characterized in that, Includes the following steps: Insert the PCBA board (7) into the inner cavity of the metal needle tube (1), so that the detection end of the food temperature sensor is positioned at the tip of the metal needle tube (1), and the antenna feed point spring (73), the charging positive electrode spring (71) and the grounding spring (72) are in the preset electrical contact position. One end of the ceramic connecting shaft (2) is pressed tightly into the tail end of the metal needle tube (1), and the other end is connected to the front end of the metal tube (3) to form an insulating and sealed structure. Insert the reduced diameter section of the PCBA board (7) into the inner hole of the metal tube (3), so that the grounding spring (72) and the inner wall of the metal tube (3) can be elastically contacted to form a conductive path, and the antenna feed spring (73) can be aligned with the feed interface area of ​​the metal tube (3). The metal handle (4) is threaded or welded to the rear end of the metal tube (3), and the metal tube (3) is fixed to the end of the metal handle (4), so that the metal tube (3) and the metal handle (4) together constitute the radiator of the inverted F antenna, wherein the antenna feed point spring (73), the ground spring (72), the metal tube (3) and the metal handle (4) form an impedance-matched radio frequency feed path. The ambient temperature sensor (6) is embedded in the end cavity of the metal handle (4) through the ceramic isolation tube (5), so that the lead of the ambient temperature sensor (6) is only connected to the temperature measuring circuit on the PCBA board (7), and is structurally and electrically isolated from the metal tube (3).

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