Radio frequency device

Abstract

The radio frequency device is characterized in that the radio frequency device is provided with a spiral antenna and a radio frequency module, and the first end of the spiral antenna is electrically connected with a radio frequency interface of the radio frequency module; the spiral antenna structurally comprises a core material and a spiral conductor wound and fixed on the periphery of the core material. The spiral conductor is made of a single or a plurality of bundled metallized fibers, metal wires or carbon fiber wires, and the radius of each metallized fiber, metal wire or carbon fiber wire is 1t; the frequency of the radio-frequency signal is five times of the skin depth when the radio-frequency signal is transmitted on the metallized fiber, the metal wire or the carbon fiber wire; the helical antenna has an extremely high quality factor, so that a communication distance which is several times of that of a traditional helical antenna is obtained under the same power.

Description

Technical Field

[0001] The present invention relates to a radio frequency device using a helical antenna, and in particular to a method for realizing a helical antenna. The improved helical antenna disclosed in the present invention has a communication efficiency and a communication distance that are many times higher than those of a traditional helical antenna under the same power conditions, and the production efficiency is greatly improved and the cost is lower. Background Art

[0002] Spring-shaped helical antennas are generally used in the communications field because of their wide bandwidth, circular polarization, high gain, and compact structure. RF devices using such helical antennas are, for example, walkie-talkies, electronic tags enclosed in tires, and vehicle-mounted communicators. In particular, when D / λ<0.18 (D is the outer diameter of the helical antenna and λ is the wavelength of the communication baseband), the helical antenna has a significant gain increase in the normal plane (the direction perpendicular to the helical axis), which can significantly increase the communication distance.

[0003] Traditional helical antennas generally use a copper-plated steel with a diameter of 0.15 to 1.5 mm, which is produced by winding it on demand and cutting it into sections using a spring-producing machine. The communication frequencies for civilian, police, and military use are between 300 MHz and 6 GHz. The corresponding skin depth for a pure copper antenna is 0.0045 to 0.0015 mm (4.5 to 1.5 μm), while the corresponding skin depth for an iron-based antenna is 0.0004 to 0.00012 mm (0.4 to 0.12 μm). Therefore, the Q value (quality factor, the larger the value, the higher the antenna efficiency) of a traditional helical antenna is only 3 to 6 (related to the communication frequency), and its ability to radiate or receive electromagnetic waves is relatively weak.

[0004] On the other hand, traditional spiral antennas are very rigid and difficult to use in scenes that may deform, such as clothing and soft furniture. They are also difficult to use in scenes that require twisting and fixation, such as vehicle frames. On the other hand, traditional spiral antennas are prone to plastic deformation, causing significant changes in Q value, center frequency, bandwidth, and lobe pattern, resulting in failure.

[0005] Therefore, society needs an improved helical antenna that can significantly increase the Q value and significantly increase flexibility while keeping the size and other electrical characteristics basically unchanged. Summary of the Invention

[0006] The present invention discloses a radio frequency device, characterized in that it has a helical antenna and a radio frequency module, wherein the first end of the helical antenna is electrically connected to the radio frequency interface of the radio frequency module; the radio frequency module has the function of outputting radio frequency electrical signals, receiving radio frequency electrical signals, or both; the structure of the helical antenna includes a core material, a helical conductor wound around and fixed to the periphery of the core material, the material of the helical conductor is a single or multiple bundled metalized fibers, metal wires, or carbon fiber wires, and in order to improve the Q value, the radius of a single metalized fiber, the metal wire, or the carbon fiber wire is less than the frequency of the radio frequency signal on the metalized fiber. The skin depth of the metal fiber, the metal wire or the carbon fiber line is 5 times greater than that of the metal fiber, the metal wire or the carbon fiber line during transmission. For example, for the 868-915 MHz frequency range, the skin depth of copper is about 3 μm, so the radius of the metalized fiber, the metal wire or the carbon fiber line should be less than 15 μm. Considering that ferromagnetic materials, such as manganese, iron, nickel or related alloys, will seriously reduce the skin depth, for example, for the 868-915 MHz frequency range, the skin depth of iron is only 0.1 μm, which makes it impossible to mass produce. Therefore, the relative permeability of the metal of the metalized fiber or the metal wire is less than 5, and the resistivity is less than 5×10 -8 Ω·m, generally using one of copper, aluminum, silver, gold or an alloy thereof; when a metallized fiber is used as a spiral conductor, the resistivity of a single metallized fiber is less than 100Ω / cm, and the structural feature of the cross section is that at least two materials are coaxially distributed, the two materials being material A and material B, wherein material B is wrapped around material A; the key point is that the axial thermal expansion coefficient of material A within the range of -40°C to +150°C is less than 25x10 -6 / ℃, material A can be one of aramid, carbon fiber, basalt fiber, modified glass fiber, etc., and material B can be one of metals such as copper, silver, aluminum, gold, etc. or an alloy.

[0007] Because the resistance of a single metallized fiber, the metal wire or the carbon fiber wire is large, resulting in a small Q value, a better design is to use multiple metallized fibers, the metal wire or the carbon fiber wire, and the outer diameter of each metallized fiber, the metal wire or the carbon fiber wire is ≤ 2 times the skin depth. For example, for the 868-915 MHz frequency range, the skin depth of copper is approximately 3 um, so the radius of the metallized fiber, the metal wire or the carbon fiber wire must be ≤ 6 um.

[0008] In order to avoid the close contact between multiple metallized fibers, metal wires or carbon fiber wires to form a single thicker conductor, resulting in a more obvious skin impedance effect, each of the multiple bundled metallized fibers, metal wires or carbon fiber wires used to make the spiral conductor has an insulating layer on the outer surface, and the resistivity of the insulating layer is greater than 0.01Ω·m; when the spiral conductor uses metallized fibers or metal wires, the insulating layer material includes oxides or reduced products generated on the surface of the metallized fibers or metal wires through oxidation reactions or reduction reactions, or organic compounds with a molecular weight of less than 1 million; when the spiral conductor uses carbon fiber wires, the insulating layer material includes one or a combination of diamond, silicon carbide, carbon nitride, and organic compounds with a molecular weight of less than 1 million.

[0009] Because carbon fiber has a resistivity at least 60 times higher than copper, it significantly affects the antenna's Q and power. Furthermore, the resistivity of high-modulus carbon fiber, suitable for winding, is 3 million times higher than copper, making it even more difficult to use in antenna manufacturing. Therefore, the spiral conductor is preferably made of metalized fiber or metal wire.

[0010] To produce metal conductors with a radius less than 3µm, only gold is suitable, which is cost-prohibitive. Meanwhile, a 1-meter-long single-crystal copper wire with a diameter of 10µm costs approximately 2 RMB in bulk. For example, in the 868-915MHz frequency range, to transmit 10mW of high-efficiency RF power (typically used in electronic toll collection tags for vehicles), approximately 500 8.5cm-long 10µm single-crystal copper wires would be required to create a quarter-wavelength antenna, costing 75 RMB. This clearly makes it unattainable. Metallized fiber with the same electrical specifications, on the other hand, costs only 0.3-0.5 RMB (compared to 1-3 RMB for traditional helical antennas with the same electrical performance), clearly offering potential for widespread adoption.

[0011] Therefore, the best choice is to use metallized fiber wire as the material of the spiral conductor. The outer diameter of a single metallized fiber is less than 30 μm and the resistivity is less than 100 Ω / cm. The structural feature is that it has at least two materials, namely material A and material B, wherein at least material A has a longitudinal thermal expansion coefficient of less than 25x10 in the range of -40°C to +150°C. -6 / ℃ (not greater than the thermal expansion coefficient of conventional conductive metals such as copper, aluminum, silver, and gold), material A can be one of aramid, carbon fiber, basalt fiber, modified glass fiber, etc.; at least material B has a resistivity of less than 5×10 -8 The conductor of Ω·m, material B can be one of the metals such as copper, silver, aluminum, gold, or an alloy.

[0012] Preferably, the metallized fibers are produced using a cross-linking chelation method or single crystal growth method, tightly bonding a continuous material B to the surface of material A. This material A provides high strength along the fiber's axis, preventing material B from breaking under tension. For example, using 5µm diameter aramid as material A and 2.5µm thick copper as material B can increase axial strength by 3-10 times compared to 10µm diameter single crystal copper, making it more suitable for various environments.

[0013] There are three methods for winding the spiral conductor on the core material. The first method is to weave the material of the spiral conductor and multiple insulating wires with an outer diameter close to that of the spiral conductor material into a mesh and tightly wrap them around the periphery of the core material. The second method is to spirally wind the material of the spiral conductor and multiple insulating wires with an outer diameter close to that of the spiral conductor material side by side around the periphery of the core material, and then tightly wrap them with a first insulating outer layer, wherein the first insulating outer layer is one or a combination of a braided mesh, a hot melt colloid, and glue. The third method is to first wrap the material of the spiral conductor in a mesh. The outer periphery of the core material is covered with a second insulating outer layer, and the second insulating outer layer has one of the characteristics of hot melting into glue, solution softening into glue or non-glue, and then the spiral conductor is wound around the outer periphery of the core material. Finally, the second insulating outer layer is melted by heating and bonded to the outer periphery of the core material, the second insulating outer layer is bonded to the outer periphery of the core material after being immersed in a solution, or the spiral conductor and the core material are tightly wrapped by the first insulating outer layer. The first insulating outer layer is one or a combination of a woven mesh, a hot melt colloid, and glue.

[0014] Because the spiral conductor is made of very thin material, it is difficult to shape once it is out of the winding state, making it difficult to automatically weld, crimp, or fix it to the RF interface by other means to achieve electrical connection. In order to achieve large-scale automated production, the spiral antenna must first be wound and fixed on a very long core material, and then cut as needed. In this case, the spiral conductor may be out of the winding state at the end of the cut spiral antenna. Therefore, the first end of the spiral antenna has a fixed terminal, which has the characteristics of mechanically clamping the spiral conductor and the core material while electrically connecting to the spiral conductor. The fixed terminal and the RF interface of the RF module are electrically connected by one or more of welding, riveting, and crimping.

[0015] For applications where the flexibility of a helical antenna is a concern, the core material is a flexible material, selected from one or a combination of materials with a dielectric constant change rate of less than 25% upon moisture exposure, such as rubber, silicone, polyester, aramid, resin-coated glass fiber, or resin-coated carbon fiber. This helical antenna RF device can be sewn onto clothing for next-to-the-skin wear; it can also be attached to the surface of a vehicle frame along its curves for use; it can also be fixed into a specific shape to create a complex super-helical antenna structure and achieve a specific lobe pattern; and it can be fixed to a special elastomer, where its electrical properties change due to the elastomer's deformation, thereby becoming an RF sensor device capable of both external communication and detecting the elastomer's deformation.

[0016] According to actual tests, for ultra-high frequency tire-enclosed electronic tags in the 868-915 MHz frequency band, a sample was made of 500 spiral antennas with a radius of 10 μm, where material A is aramid and material B is copper as the spiral conductor. The communication distance was increased by 400% (from 0.5 meters to 2.5 meters) compared to traditional electrical products with the same mechanical structure sold on the market and made of copper-plated steel springs as spiral antennas. The production efficiency is expected to increase by 30% (the annual output of a production line increased from 5 million to 6.5 million pieces), the defective rate was reduced from 0.8% to 0.1%, and the cost was reduced by approximately 15% (from 2 yuan to 1.71 yuan).

[0017] According to actual tests, for the ultra-high frequency clothing electronic tag in the frequency band of 868-915Mhz, a sample was made of 400 spiral antennas with a radius of 10um, with A material being aramid and B material being copper as the spiral conductor wound around the periphery of the aramid core material. The communication distance was increased by 500% (from 0.3 meters to 1.8 meters) compared with traditional products sold on the market, which are larger and difficult to bend. This solves the problem of inaccurate clothing management during large-scale washing, and can be used as an armband for users to identify and track people in areas such as mines, factories, and military camps where it is inconvenient to set up cameras and fingerprint recognition.

[0018] Therefore, the beneficial effect of the present invention is that, under the premise of keeping the size basically unchanged, keeping other electrical characteristics basically unchanged and having more advantageous costs, the improved helical antenna greatly improves the Q value to obtain multiple times the communication distance, and can greatly increase the flexibility, thereby expanding the application range and application experience of the helical antenna radio frequency device.

[0019] Figures in the specification

[0020] Figure 1 This is the first embodiment of the present invention.

[0021] Figure 2 This is the second embodiment of the present invention.

[0022] Figure 3 This is the first embodiment of the spiral conductor described in the present invention.

[0023] Figure 4 This is the first embodiment of the helical antenna of the present invention.

[0024] Figure 5 This is the second embodiment of the helical antenna of the present invention.

[0025] Figure 6 This is the third embodiment of the helical antenna described in the present invention.

[0026] Figure 7 It is a schematic diagram of the process of automated production of the present invention. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention and do not limit the scope of application of the present invention. For ordinary technicians in this field, the present invention can be applied to other similar scenarios based on these drawings without inventive work; as shown in this specification and claims, unless the context clearly indicates an exception, the words "one", "a", "an" and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "including" or "comprising" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements. The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment".

[0028] Figure 1 use Figure 4 The first embodiment of the radio frequency device disclosed in the present invention is made by electrically connecting the helical antenna 1 to the radio frequency module 2, which is a monopole antenna type radio frequency device, such as a walkie-talkie; Figure 2 use Figure 4 The second embodiment of the radio frequency device disclosed in the present invention is made by electrically connecting the helical antenna 1 to the radio frequency module 2, which is a dipole antenna type radio frequency device, such as an electronic tag packaged in a tire.

[0029] exist Figure 1 and Figure 2 In the embodiment, the helical antenna 1 has a fixed terminal 15, which is made of a metal flat strip with multiple rows of needles. When the helical antenna 1 is produced, the fixed terminal 15 is buckled on one end of the helical antenna 1, and the multiple rows of needles pierce the fixed terminal 15. Figure 4The first insulating outer layer 14 in the spiral conductor 12 is in close electrical contact, or punctured Figure 6 The second insulating outer layer 16 in the spiral conductor 12 is in close electrical contact, or directly in close electrical contact with the spiral conductor 12. Figure 5 Then the fixed terminal 15 is electrically connected to the RF interface 21 of the RF module 2 by welding, crimping, riveting or other methods.

[0030] Figure 4 、 Figure 5 、 Figure 6 There are three different ways to realize the helical antenna 1. Figure 4 In the process, the spiral conductor 12 and a plurality of insulating wires 13 having an outer diameter close to that of the spiral conductor 12 are spirally wound side by side on the outer periphery of the core material 12, and then tightly wrapped with a first insulating outer layer 14. The first insulating outer layer 14 is made of TPEE material. Figure 5 In the embodiment, the spiral conductor 12 and a plurality of insulating wires 13 having an outer diameter close to that of the spiral conductor 12 are woven into a mesh and tightly wrapped around the outer periphery of the core material 11. Figure 6 In the process, first, the second insulating outer layer 16 is covered on the outer periphery of the spiral conductor 12. The second insulating outer layer 16 is made of hot-melt PU material. Then, the spiral conductor 12 is wound around the outer periphery of the core material 11 and the second insulating outer layer 16 is heated and melted so that adjacent second insulating outer layers 16 are fused to each other. At the same time, the melted second insulating outer layer 16 will also adhere to the core material 11. When the temperature drops below the melting temperature of the second insulating outer layer 16, each circle of the spiral conductor 12 is firmly wrapped and fixed to the outside of the core material 11 to make the spiral antenna 1.

[0031] Figure 3 The figure shows a cross-section of a metallized fiber. Material A is aramid, and material B is copper or aluminum. The outer diameter of the metallized fiber is about 10 μm, and the diameter of material A is about 5 μm.

[0032] exist Figure 7 In the embodiment, the intermediate form of the helical antenna 1 is a coiled form. Figure 4 The structure comprises a helical conductor 12, an insulating wire 13, and a first insulating outer layer 14 wound and fixed around a flexible core material 11. Here, the flexible conductor 11 is made of aramid. The steps for producing the RF device are as follows: Step 1 31: attaching fixed terminals 15 to the unwound intermediate portion of the helical antenna 1 at predetermined intervals; Step 2 32: cutting the intermediate portion of the helical antenna 1 according to predetermined intervals to form the helical antenna 1; and Step 33: electrically connecting the helical antenna 1 to the RF module 2 to complete the RF device.

Claims

1. A radio frequency device, characterized in that: A helical antenna and a radio frequency module are provided, wherein a first end of the helical antenna is electrically connected to a radio frequency interface of the radio frequency module; The radio frequency module has the function of outputting radio frequency electrical signals, receiving radio frequency electrical signals, or both; The structure of the helical antenna includes a core material and a helical conductor wound around and fixed on the periphery of the core material. The material of the spiral conductor is a single or multiple bundled metalized fibers, metal wires, or carbon fiber wires, and the radius of each of the metalized fibers, metal wires, or carbon fiber wires is less than 5 times the skin depth of the radio frequency signal when it is transmitted through the metalized fibers, metal wires, or carbon fiber wires. The relative magnetic permeability of the metal of the metalized fiber or the metal wire is less than 5, and the resistivity is less than 5×10 -8 Ω·m, generally made of copper, aluminum, silver, gold or alloy; The resistivity of a single metallized fiber is less than 100Ω / cm, and the structural feature of the cross section is that at least two materials are coaxially distributed, the two materials being material A and material B, wherein material B is wrapped around the periphery of material A; The axial thermal expansion coefficient of material A in the range of -40℃ to +150℃ is less than 25x10 -6 / ℃, material A can be one of aramid, carbon fiber, basalt fiber, modified glass fiber, etc.; material B can be one of metals such as copper, silver, aluminum, gold, etc. or an alloy.

2. A radio frequency device according to claim 1, characterized in that: The spiral conductor is made of a plurality of bundled metalized fibers, metal wires, or carbon fiber wires, each of which has an insulating layer on its outer surface, and the resistivity of the insulating layer is greater than 0.01Ω·m; When the spiral conductor is made of metallized fiber or metal wire, the insulating layer material includes oxides generated on the surface of the metallized fiber or the metal wire by oxidation reaction or organic compounds with a molecular weight of less than 1 million. When the spiral conductor is made of carbon fiber wire, the insulating layer material includes one or a combination of diamond, silicon carbide, carbon nitride, and an organic compound with a molecular weight less than 1 million.

3. The radio frequency device according to claim 1, wherein: The spiral conductor is wound around and fixed to the outer periphery of the core material by weaving the spiral conductor material and a plurality of insulating wires having an outer diameter close to that of the spiral conductor material into a mesh and tightly wrapping the mesh around the outer periphery of the core material.

4. The radio frequency device according to claim 1, wherein: The spiral conductor is wound and fixed on the periphery of the core material in a manner that the material of the spiral conductor and a plurality of insulating wires having an outer diameter close to that of the material of the spiral conductor are spirally wound side by side on the periphery of the core material, and then tightly wrapped with a first insulating outer layer, wherein the first insulating outer layer is one or a combination of a woven mesh, a hot melt colloid, and glue.

5. The radio frequency device according to claim 1, wherein: The spiral conductor is wound and fixed around the periphery of the core material in the following manner: first, a second insulating outer layer is covered on the periphery of the material of the spiral conductor, and the second insulating outer layer has one of the properties of hot-melting into glue, solution-softening into glue, or non-glueing; then the spiral conductor is wound around the periphery of the core material, and finally the second insulating outer layer is melted by heating and bonded to the periphery of the core material, the second insulating outer layer is bonded to the periphery of the core material after being soaked in a solution, or the spiral conductor and the core material are tightly wrapped by the first insulating outer layer to complete the fixation; the first insulating outer layer is one of a woven mesh, a hot-melt colloid, and glue, or a combination thereof.

6. The radio frequency device according to claim 1, wherein: The first end of the helical antenna has a fixed terminal, which has the characteristics of mechanically clamping the spiral conductor and the core material while electrically connecting to the spiral conductor. The fixed terminal and the RF interface of the RF module are electrically connected by one or more of welding, riveting, and crimping.

7. The radio frequency device according to claim 1, wherein: The core material is a flexible material, and the material of the core material is one or a combination of materials whose dielectric constant change rate after being wet is less than 25%, such as rubber, silicone, polyester, aramid, resin-coated glass fiber, resin-coated carbon fiber, etc.

8. The radio frequency device according to claim 1, wherein: It also has an outer shell, which wraps the helical antenna and the radio frequency module. The outer shell is wrapped by spraying liquid colloid on the outer surface of the helical antenna and the radio frequency module and then solidifying them. Alternatively, the helical antenna and the radio frequency module are immersed in liquid colloid and then solidified into a shape. Alternatively, the helical antenna and the radio frequency module are placed in a mold for injection molding. Alternatively, the helical antenna and the radio frequency module are mechanically placed into a molded outer shell and fixed. Alternatively, a flexible sheet-shaped outer shell is wrapped or covered with the helical antenna and the radio frequency module.

9. The radio frequency device according to claim 1, wherein: The spring antenna has an intermediate form during automated production. The intermediate form is a long strip with the spiral conductor continuously and fixedly wound around the periphery of a single core material, and the length of the strip far exceeds the length of a single spring antenna. The spring antenna is obtained by cutting the intermediate form according to the required length.

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