Miniaturized ultra-wideband planar helical antenna based on magnetic medium

Abstract

The invention relates to the technical field of microwaves and antennas, particularly discloses a miniature ultra-wideband planar helical antenna based on a magnetic medium, and aims to solve the problem that indexes such as miniaturization, ultra-wideband, high gain and circular polarization are difficult to consider in the design of an existing helical antenna. The helical antenna structure comprises an antenna radiation unit, a metal stepped shielding inner cavity, a Balun feed structure, a feed connector, a circular metal reflection back cavity and a magnetic dielectric material. According to the invention, the magnetic dielectric material is arranged below the radiation circuit so as to regulate and control the surface current distribution at the tail end of the circuit and centrally regulate and control the size and direction of an electromagnetic field vector in a cavity, so that the reduction of the transverse and longitudinal dimensions of the antenna is effectively realized; the impedance matching bandwidth and the axial ratio bandwidth of the miniaturized antenna can be improved while the high gain of the antenna is kept, the extremely high impedance matching bandwidth can be realized, and the excellent circular polarization characteristic is kept in the bandwidth range.

Description

Technical Field

[0001] The invention relates to the technical field of microwaves and antennas, and in particular to a miniaturized ultra-wideband planar helical antenna based on magnetic media. Background Art

[0002] With the application of ultra-wideband systems in the fields of mobile communications and national defense, antennas play an important role in military and civilian fields. Today's wireless devices have the characteristics of high integration and miniaturization, and their requirements for antennas are also developing in the direction of wider frequency bands, smaller sizes, and better radiation capabilities. Existing ultra-wideband antennas often use structures such as helical antennas, slot antennas, Vivaldi antennas, and magneto-electric dipole antennas. Among them, the helical antenna has the unique advantage of generating circularly polarized waves. Compared with linear polarization, the advantage of circular polarization is that it can reduce the Faraday rotation effect in the ionosphere, does not need to strictly limit the direction between the transmitter and receiver antennas, and exhibits stable impedance characteristics and good directional pattern characteristics in an extremely wide frequency band, which makes it of great significance and use value in many specific occasions. In actual application scenarios, in order to meet the unidirectional radiation and anti-interference capabilities of the helical antenna, people often load a metal reflective cavity on the back of the antenna, but because the electromagnetic reflection in the reflective cavity and its size are positively correlated with the operating frequency of the antenna, miniaturization will inevitably lead to a sharp deterioration in antenna performance.

[0003] Therefore, due to the uniqueness in characteristics and applications, the design of planar helical antennas faces various challenges, such as circular polarization characteristics, impedance, gain, and radiation patterns must have good characteristics within an extremely wide bandwidth and the antenna size must be small. The miniaturization of helical antennas should include two parts: one is to reduce the aperture of the antenna, and the other is to reduce the height of the antenna. In terms of aperture reduction: currently, aperture reduction is often achieved by loading inductors and capacitors, or by using end loading resistors and absorbing materials to improve low-frequency performance, but this method increases the heat loss of radiation energy and reduces radiation efficiency; in terms of height reduction: EBG electromagnetic bandgap structure is often used to achieve miniaturization design, and this method is complex to design. In addition, the existing technology often does not consider the impact of the length of the feeding structure on the height of the antenna, and a longer feeding structure will also increase the longitudinal size of the antenna. In summary, there is no effective solution to the problem of balancing high performance in the research and design of miniaturization of helical antennas. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, which can improve the impedance matching bandwidth and circular polarization bandwidth of the antenna, improve the distortion of the ultra-wideband antenna pattern, suppress the interference of metal coupling on the antenna, better solve the balance between miniaturization and high radiation performance, and solve the problems mentioned in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a miniaturized ultra-wideband planar helical antenna based on magnetic medium, comprising:

[0006] Antenna radiating element;

[0007] Magnetic dielectric materials used to control the surface current distribution at the end of the circuit and to centrally control the magnitude and direction of the electric field vector of electromagnetic reflection in the cavity;

[0008] A circular metal reflective back cavity is arranged below the antenna radiation unit to reflect electromagnetic waves for backward radiation;

[0009] A metal stepped shielding inner cavity arranged inside the circular metal reflective back cavity;

[0010] and a balun feeding structure for providing excitation to the antenna radiating element and a feeding connector for connecting an external coaxial feed line;

[0011] A circular reflective step structure cavity and a feeding balun perforation structure are arranged at the bottom of the metal step-shaped shielding cavity.

[0012] Preferably, the antenna radiation unit includes a dielectric substrate, and a spiral arm 1 and a spiral arm 2 printed on the dielectric substrate, the spiral arm 1 and the spiral arm 2 are 180° rotationally symmetrical with the feed balun via connection as the center, the line width and spacing of the spiral arm 1 and the spiral arm 2 remain consistent, and the areas of the metal and non-metal parts thereof are complementary; there is no direct connection between the spiral arm 1, the spiral arm 2 and the circular metal reflective back cavity.

[0013] Preferably, the dielectric substrate is arranged on the circuit support step of the circular metal reflective back cavity to fix the circular metal reflective back cavity; the spiral arm 1 and the spiral arm 2 are composite spiral lines composed of one or more of Archimedean functions, equiangular spiral functions, sin functions or equiangular functions.

[0014] The helical antenna is fed by an external balun. Since the characteristic impedance of the planar helical structure radiator is stable at 120-188Ω, in order to ensure the impedance matching between the radiator and the feeding structure and realize the balun balance characteristics of the feeding structure, the balun feeding structure generally uses microstrip balun, coaxial balun and transformer balun. The structural length of the microstrip balun and coaxial balun should be 1 / 2 of the wavelength corresponding to the lower limit frequency of the antenna operation, which will greatly increase the longitudinal size of the antenna and requires the length of the feed line to be reduced.

[0015] If the feeding balun adopts a microstrip gradient balun feeding structure for feeding, then in order to reduce its size, the balun needs to be designed into an L shape to extend the current path;

[0016] The balun feeding structure and the spiral arms 1 and 2 of the antenna radiation unit are smoothly connected to the fan-shaped transition structure through a feeding balun via connection (104) arranged on a dielectric substrate.

[0017] Preferably, the shape structure of the magnetic medium material is filled between the metal stepped shielding inner cavity and the circular metal reflective back cavity;

[0018] The magnetic medium material is arranged below the radiation unit, or above the circular metal reflective back cavity, or in a partial area between the antenna radiation unit and the circular metal reflective back cavity;

[0019] The material type of the magnetic medium material is one or more of inorganic magnetic material, organic magnetic material and composite magnetic material.

[0020] The electromagnetic properties of the magnetic dielectric material are a magnetic permeability greater than 1 and a dielectric constant greater than 1.

[0021] The unbalanced feeding end in the balun feeding structure is connected to the dielectric substrate through the feeding balun perforated structure;

[0022] The balanced feeding end in the balun feeding structure is connected to the coaxial feed line through a feeding connector arranged on the side of the circular metal reflective back cavity.

[0023] Preferably, a fixed feeding connection is provided between the antenna radiation unit and the circular metal reflective back cavity.

[0024] Preferably, the distance between the antenna radiation unit and the circular metal reflective back cavity is not greater than 0.1λ, where λ is the wavelength of the lowest operating frequency of the antenna in free space.

[0025] Preferably, the circular metal reflective back cavity and the metal stepped shielding inner cavity may adopt a variety of structures, including a truncated cone structure, a frustum structure or a spherical structure.

[0026] Preferably, the circular metal reflective back cavity is made of conductive metal materials such as copper, iron, steel, alloy, aluminum or tin.

[0027] The beneficial effects of the present invention are:

[0028] 1) The present invention regulates the surface current distribution at the end of the circuit by placing a magnetic dielectric material under the radiation unit. Since the magnetic dielectric material has high magnetic permeability and dielectric constant, it can effectively bind the current on the metal surface and reduce its propagation speed on the spiral arm. This method of regulating the surface current distribution effectively extends the equivalent path of the current;

[0029] It can also increase the equivalent reactance value of the circuit and improve the Q value, thereby reducing the low-frequency working bandwidth of the antenna and achieving a reduction in the lateral size of the antenna.

[0030] 2) Due to the high magnetic permeability of the magnetic dielectric material of the present invention, the distribution of the electromagnetic field can be guided to make it more concentrated inside the material. This electromagnetic concentration effect can effectively control the propagation direction of the electromagnetic wave in the cavity, and because the imaginary part of the magnetic permeability of the material is equivalent to resistance, the electromagnetic energy concentrated inside can be uniformly attenuated, thereby achieving the effect of reducing the height of the antenna; the magnetic dielectric material can improve the impedance matching bandwidth and circular polarization performance of the miniaturized antenna, and combined with the L-shaped bending structure design of the balun, the height of the spiral antenna is further reduced, achieving a reduction in the longitudinal size of the antenna.

[0031] 3) The present invention can effectively suppress the influence of magnetic medium materials on the electromagnetic loss of the high-frequency radiation area of ​​the antenna by setting a metal stepped shielding cavity inside the circular metal reflective back cavity, thereby ensuring the radiation performance of the antenna in the high-frequency part. The present invention sets a circular reflective stepped structure cavity at the bottom of the inner side of the shielding cavity, which can effectively regulate the electromagnetic reflection characteristics of the metal cavity to the high-frequency area, so that the reflected clutter in the specific area cancels each other, thereby effectively improving the axial ratio performance of the antenna and making the antenna have good circular polarization characteristics; and because the antenna has the same height in the broadband range, compared with the low-frequency part, the high frequency of the antenna is prone to the situation where the reflective back cavity and the radiation unit are separated by 1 / 2λ, which will cause the reflected electromagnetic wave and the forward radiated electromagnetic wave to cancel each other, resulting in the problem of reduced gain efficiency and concave radiation pattern. Therefore, the reflective stepped structure can make the reflected electromagnetic wave and the radiated electromagnetic wave in the specific area superimposed positively by regulating the reflection phase of the electromagnetic wave in the specific area, which solves the problem well. The present invention uses a metal conductor as a reflective back cavity, so that the antenna can be actually applied to various installation platforms, expanding the application range of the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is an overall schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a compact Archimedean spiral structure;

[0033] Figure 2 The circuit structure diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a compact Archimedean spiral structure;

[0034] Figure 3 The antenna radiation unit is a compact Archimedean spiral structure, and the structure of the miniaturized ultra-wideband planar spiral antenna reflection cavity based on magnetic medium is shown;

[0035] Figure 4 It is an overall schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a Sin function bent spiral structure;

[0036] Figure 5It is a circuit structure diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a Sin function bent spiral structure;

[0037] Figure 6 It is an overall schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is an equiangular + bent spiral structure;

[0038] Figure 7 It is a circuit structure diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is an equiangular + bent spiral structure;

[0039] Figure 8 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium, in which the magnetic medium material is a ring structure;

[0040] Fig. 9 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium loading, in which the magnetic medium material is a honeycomb structure;

[0041] Fig.10 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium, in which the magnetic medium material is a periodically distributed structure;

[0042] Fig.11 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium, in which the magnetic medium material is above the internal space of the reflective back cavity;

[0043] Fig.12 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium, in which the magnetic medium material is in the middle of the internal space of the reflective back cavity;

[0044] Fig.13 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium, in which the magnetic medium material is located below the internal space of the reflective back cavity;

[0045] Fig.14 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium with a truncated cone structure as the reflective back cavity;

[0046] Fig.15 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium with a reflective back cavity of a frustum structure;

[0047] Fig.16 It is a schematic diagram of the structure of a miniaturized ultra-wideband planar helical antenna based on magnetic medium with a spherical reflective back cavity;

[0048] Fig.17 This is the front circuit structure diagram of the L-type feeding balun of the miniaturized ultra-wideband planar helical antenna based on magnetic medium;

[0049] Fig.18 This is the back circuit structure diagram of the L-type feeding balun of the miniaturized ultra-wideband planar helical antenna based on magnetic medium;

[0050] Fig.19 It is a reflection coefficient diagram of the port of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a compact Archimedean spiral structure;

[0051] Fig. 20 The axial ratio diagram of the miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a compact Archimedean spiral structure;

[0052] Fig.21 It is a radiation efficiency diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, in which the antenna radiation unit is a compact Archimedean spiral structure;

[0053] Fig. 22 The antenna radiating unit is a compact Archimedean spiral structure, and the radiation gain diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium is shown;

[0054] Fig.23 The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the miniaturized ultra-wideband planar spiral antenna at 0.5GHz;

[0055] Fig.24 The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the miniaturized ultra-wideband planar spiral antenna is 1GHz;

[0056] Fig.25 The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the miniaturized ultra-wideband planar spiral antenna is 2GHz;

[0057] Fig.26 The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the miniaturized ultra-wideband planar spiral antenna at 3GHz;

[0058] Fig. 27 The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the miniaturized ultra-wideband planar spiral antenna at 4GHz;

[0059] Fig.28 The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the ultra-wideband planar spiral antenna is 7GHz;

[0060] Fig.29The antenna radiation unit is a compact Archimedean spiral structure based on magnetic medium, and the xoz plane radiation pattern of the miniaturized ultra-wideband planar spiral antenna at 10GHz;

[0061] In the figure, 1-antenna radiation unit; 2-magnetic dielectric material; 3-circular metal reflective back cavity; 4-metal stepped shielding inner cavity; 5-balun feeding structure; 6-feeding connector; 101-spiral arm 1; 102-spiral arm 2; 103-fan-shaped transition structure; 104-feeding balun via connection; 105-dielectric substrate, 301-circuit support step; 401-circular reflective stepped structure inner cavity; 402-feeding balun perforated structure; 501-unbalanced feeding end; 502-gradient index microstrip line; 503-balanced feeding end. DETAILED DESCRIPTION

[0062] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0063] It should be noted that the embodiments and features of the embodiments of the present invention can be combined with each other without conflict. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0064] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use, or the positions or positional relationships commonly understood by those skilled in the art, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0065] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] The present invention provides a technical solution: a miniaturized ultra-wideband planar helical antenna based on magnetic medium, such as Figure 1 As shown, it includes: an antenna radiating unit 1; a magnetic dielectric material 2 used to regulate the surface current distribution at the end of the circuit and to centrally regulate the magnitude and direction of the electromagnetic field vector in the cavity; a circular metal reflective back cavity 3 arranged below the antenna radiating unit 1 for shielding the interference of the installation environment and reflecting the electromagnetic wave for backward radiation (unidirectional radiation); a metal stepped shielding inner cavity 4 arranged inside the circular metal reflective back cavity 3 for suppressing the electromagnetic interference effect between the magnetic dielectric material 2 and the antenna radiating unit 1; and a balun feeding structure 5 for providing excitation for the radiating unit 1 and a feeding connector 6 for connecting an external coaxial feed line.

[0067] A circular reflective step structure cavity 401 and a feeding balun through-hole structure 402 are arranged at the bottom of the metal step-shaped shielding cavity 4 .

[0068] Furthermore, in the present technical solution, a magnetic dielectric material is arranged between the antenna radiation unit and the reflective back cavity to centrally control the magnitude and direction of the electromagnetic field vector in the cavity; the feed balun adopts an L-shaped bending design to achieve the effect of reducing the height of the antenna; the magnetic dielectric material is arranged to control the surface current distribution at the end of the circuit, and then combined with the composite circuit structure design of the antenna, the lateral size of the antenna is reduced; and the design of a shielded inner cavity is combined in some specific areas to achieve the purpose of improving the antenna performance.

[0069] Further, such as Figure 2 As shown, the antenna radiation unit 1 includes a dielectric substrate 105, and a spiral arm 1101 and a spiral arm 2102 printed on the dielectric substrate 105, the spiral arm 1101 and the spiral arm 2102 are 180° rotationally symmetrical with the feed balun via connection 104 as the center, the line width and spacing of the spiral arm 1101 and the spiral arm 2102 are consistent, and the areas of the metal and non-metal parts thereof are complementary; there is no direct connection between the spiral arm 1101, the spiral arm 2102 and the circular metal reflective back cavity 3.

[0070] like Figure 3As shown, the dielectric substrate 105 is arranged on the circuit supporting step 301 of the circular metal reflective back cavity 3 to fix the circular metal reflective back cavity 3 and form the overall structure of the antenna.

[0071] The spiral arms 1101 and 2102 may adopt various types of geometric shapes, including one or more of an Archimedean function, an equiangular spiral function, a sinusoidal function or a composite spiral composed of equiangular functions, such as a compact composite Archimedean spiral structure, a sinusoidal function bent spiral arm structure, an equiangular + bent spiral structure, etc., respectively. Figure 1 , Figure 4 , Figure 6 shown.

[0072] like Figure 2 As shown, spiral arm 1101 and spiral arm 2102 both adopt a compact composite Archimedean spiral structure to form a circuit structure of a spiral antenna. The two spiral arms are 180° rotationally symmetrical with the feed balun via connection 104 as the center.

[0073] like Figure 5 As shown, both spiral arm 1101 and spiral arm 2102 adopt a Sin function folded spiral arm circuit structure to form a circuit structure of a spiral antenna. The two spiral arms are 180° rotationally symmetrical with the feed balun via connection 104 as the center.

[0074] like Figure 7 As shown, both spiral arm 1101 and spiral arm 2102 adopt an equiangular + bent spiral line circuit structure to form a circuit structure of a spiral antenna. The two spiral arms are 180° rotationally symmetrical with the feed balun via connection 104 as the center.

[0075] The spiral arm 1101 and the spiral arm 2102 form an antenna radiation unit in a centrally symmetrical manner. The present invention uses a compact spiral coil to significantly reduce the size of the antenna in a lower frequency band.

[0076] A fan-shaped transition structure 103 connecting the feeding balun and the spiral arms 1101 and 2102 is also provided in the center of the dielectric substrate.

[0077] The balun feeding structure and the spiral arm 1101 and spiral arm 2102 of the antenna radiation unit 1 are smoothly connected to the fan-shaped transition structure 103 through the feeding balun via connection 104 arranged on the dielectric substrate 105. Further excitation is provided for the spiral arm 1 and the spiral arm 2. By designing the fan-shaped transition structure 103, it is more convenient to achieve the matching of the broadband impedance of the antenna and achieve a wider working bandwidth.

[0078] The balun feeding structure 5 is a microstrip balun, a coaxial line balun and a transformer balun. The microstrip balun is composed of a substrate and gradient index microstrip lines 502 on both sides thereof, and is L-shaped as a whole.

[0079] The balun feeding structure 5 is an L-type balun with a gradient index microstrip line circuit structure. The front and back structure diagrams are shown in FIG. Fig.17 , Fig.18 As shown. A feeding balun perforated structure 402 is arranged at the center position of the bottom of the metal stepped shielding inner cavity 4. One end of the gradient index microstrip line 502 is an unbalanced feeding end 501 of 120-188 ohms, and the other end is a 50 ohm balanced feeding end 503. The line width of the unbalanced feeding end of the gradient index microstrip line is inconsistent with the line width of the balanced feeding end, and the difference between the line widths is about 5 times; the unbalanced feeding end 501 of the gradient index microstrip line 502 in the balun feeding structure 5 is connected to the dielectric substrate 105 through the feeding balun perforated structure 402; the balanced feeding end 503 of the gradient index microstrip line 502 in the microstrip balun feeding structure is connected to the coaxial feed line through the feeding connector 6 arranged on the side of the circular metal reflective back cavity 3.

[0080] The gradient index microstrip line 502 can be designed into different shapes, such as a step cascade shape, an exponential change shape, a hyperbolic function change shape, etc., to achieve a broadband matching effect from different impedances to 50 ohm impedance.

[0081] The distance between the antenna radiation unit 1 and the circular metal reflective back cavity 3 is not greater than 0.1λ, where λ is the wavelength of the lowest operating frequency of the antenna in free space.

[0082] The magnetic medium material 2 in the circular metal reflective back cavity 3 can be set to different shape structures, such as a ring structure, a honeycomb structure, a periodic distribution structure, etc., respectively. Figure 8 , Fig. 9 , Fig.10 As shown; and the magnetic medium material 2 can have different installation positions in the circular metal reflective back cavity 3, such as above, in the middle, below, etc. in the cavity, as shown Fig.11 , Fig.12 , Fig.13 As shown, the mutual influence between the radiation unit 1 and the circular metal reflective back cavity 3 is reduced.

[0083] The material type of the magnetic dielectric material 2 is one or more of inorganic magnetic materials, organic magnetic materials, and composite magnetic materials. Such as metal magnetic materials, ferrites, organic polymer magnetic materials, and organic / inorganic composite magnetic materials. Since the magnetic dielectric material 2 has high magnetic permeability and dielectric constant (magnetic permeability is greater than 1 and dielectric constant is greater than 1), it can regulate the surface current distribution at the end of the circuit, extend the equivalent current path, and centrally regulate the size and direction of the electromagnetic vector between the antenna radiation unit 1 and the circular metal reflective back cavity 3, thereby reducing the size of the antenna while maintaining the antenna performance.

[0084] The circular metal reflective back cavity 3 can adopt a variety of structures, including a truncated cone reflective cavity, a frustum reflective cavity, a spherical reflective cavity, etc. Fig.14 , Fig.15 , Fig.16 Different reflective cavity structures will have different effects on the impedance matching characteristics and radiation characteristics of the antenna.

[0085] Furthermore, the circular metal reflective back cavity 3 is specifically made of a conductive metal material, which may be a conductor such as copper, iron, steel, alloy, aluminum, tin, etc., so that the antenna can be actually applied to various installation platforms, thereby expanding the application range of the antenna.

[0086] The present invention provides a miniaturized ultra-wideband planar helical antenna based on magnetic medium. Under the premise of maintaining miniaturization (not greater than 0.1λ), the relative bandwidth of the antenna exceeds 181%, covering the 500MHz-10GHz frequency band. In the working frequency band, the average gain of the antenna is about 6.5dBi, the radiation efficiency of the antenna is about 80%, the axial ratio is kept within 2, and it has a stable radiation pattern in the working frequency band.

[0087] Taking a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as an example, Fig.19 As shown in the figure, it is a port reflection coefficient diagram of a compact Archimedean spiral structure antenna with a radiating unit. The antenna has good impedance matching performance, an impedance bandwidth of 500MHz-10 GHz, and a relative bandwidth of 181%, which is an ultra-wideband antenna. According to the antenna's lowest frequency of 500MHz, the height of the antenna is only 0.05λ, which is much smaller than the height of 0.25λ of a traditional antenna. Compared with the case where magnetic dielectric materials are not used, the application of magnetic dielectric materials has significantly expanded the bandwidth of the antenna in the low frequency band. Fig. 20 The figure shows the axial ratio diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, whose radiation circuit is a compact Archimedean spiral structure. Under the effect of magnetic medium materials, the axial ratio of the antenna is within 3 in the entire frequency band, and it has good circular polarization characteristics.

[0088] like Fig.21 and Fig. 22The figure shows the radiation efficiency diagram and antenna radiation gain diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium, whose radiation circuit is a compact composite Archimedean spiral structure antenna. It can be seen from the figure that the efficiency of the antenna reaches 80% and is stable after 3GHz, and the gain of the antenna in the working frequency band is -15dBi to 10dBi, which is high and stable.

[0089] like Fig.23 As shown in the figure, it is a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the radiation circuit. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches -15dBi. Fig.24 As shown, a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the radiation circuit is a 1GHz xoz plane radiation pattern. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches 0dBi.

[0090] like Fig.25 As shown in the figure, it is a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the radiation circuit. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches 5dBi. Fig.26 As shown, the radiation pattern of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium at 3GHz is a compact Archimedean spiral structure. The radiation circuit is a compact Archimedean spiral structure. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches 10dBi.

[0091] like Fig. 27 As shown in the figure, it is a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the radiation circuit. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches 7dBi. Fig.28 As shown, the radiation circuit is a compact Archimedean spiral structure based on magnetic medium, which is a miniaturized ultra-wideband planar spiral antenna with a radiation pattern on the xoz plane at 7GHz. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches 7dBi.

[0092] like Fig.29 As shown, the radiation pattern of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the radiation circuit is the xoz plane at 10GHz. The radiation direction of the antenna is perpendicular to the ground and upward. The antenna is directional radiation. The radiation pattern has good symmetry and unidirectional radiation capability, and the radiation gain reaches 8dBi.

[0093] The present invention can improve the antenna impedance matching bandwidth, circular polarization bandwidth and radiation characteristics by loading magnetic dielectric materials. Combined with the L-type balun structure, the structural design of the miniaturized antenna is realized, and the purpose of loading magnetic dielectric materials in some specific areas to improve the antenna performance is achieved.

[0094] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A miniaturized ultra-wideband planar helical antenna based on magnetic medium, characterized in that: include: Antenna radiating element (1); Magnetic dielectric material (2) for regulating the surface current distribution at the end of the circuit and for centrally regulating the magnitude and direction of the electromagnetic field vector in the cavity; A circular metal reflective back cavity (3) disposed below the antenna radiation unit (1) for reflecting electromagnetic waves for backward radiation; A metal stepped shielding inner cavity (4) arranged inside the circular metal reflective back cavity (3); and a balun feeding structure (5) for providing excitation for the antenna radiation unit (1) and a feeding connector (6) for connecting an external coaxial feed line; A circular reflective step structure cavity (401) and a feeding balun perforated structure (402) are arranged at the bottom of the metal step-shaped shielding cavity (4).

2. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 1, characterized in that: The antenna radiation unit (1) comprises a dielectric substrate (105), and a spiral arm 1 (101) and a spiral arm 2 (102) printed on the dielectric substrate (105); the spiral arm 1 (101) and the spiral arm 2 (102) are 180° rotationally symmetrical with the feed balun via connection (104) as the center; the line width and spacing of the spiral arm 1 (101) and the spiral arm 2 (102) are consistent; the areas of the metal and non-metal parts thereof are complementary; and there is no direct connection between the spiral arm 1 (101) and the spiral arm 2 (102) and the circular metal reflective back cavity (3).

3. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 2, characterized in that: The dielectric substrate (105) is arranged on a circuit support step (301) of a circular metal reflective back cavity (3) to fix the circular metal reflective back cavity (3); the spiral arm 1 (101) and the spiral arm 2 (102) are composite spiral lines composed of one or more of an Archimedean function, an equiangular spiral function, a sin function or an equiangular function.

4. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 1, characterized in that: The balun feeding structure (5) is any one of a microstrip balun, a coaxial line balun, and a transformer balun, wherein the microstrip balun is composed of a substrate and gradient index microstrip lines (502) on both sides thereof; the balun feeding structure and the spiral arm 1 (101) and the spiral arm 2 (102) of the antenna radiation unit (1) are smoothly connected to the fan-shaped transition structure (103) through a feed balun via connection (104) arranged on a dielectric substrate (105).

5. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 1, characterized in that: The magnetic medium material (2) is filled between the metal stepped shielding inner cavity (4) and the circular metal reflective back cavity (3); The magnetic medium material (2) is arranged below the radiation unit (1), or above the circular metal reflective back cavity (3), or in a partial area between the antenna radiation unit (1) and the circular metal reflective back cavity (3); The material type of the magnetic medium material (2) is one or more of inorganic magnetic material, organic magnetic material and composite magnetic material; The electromagnetic properties of the magnetic medium material (2) are a magnetic permeability greater than 1 and a dielectric constant greater than 1.

6. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 4, characterized in that: One end of the balun feeding structure (5) is an unbalanced feeding end (501), and the other end is a balanced feeding end (503); The unbalanced feeding end (501) in the balun feeding structure (5) is connected to the dielectric substrate (105) via the feeding balun perforated structure (402); The balanced feeding end (503) in the balun feeding structure (5) is connected to the coaxial feed line via a feeding connector (6) arranged on the side of the circular metal reflective back cavity (3).

7. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 1, characterized in that: The distance between the antenna radiation unit (1) and the circular metal reflective back cavity (3) is no greater than 0.1λ, where λ is the wavelength of the lowest operating frequency of the antenna in free space.

8. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 1, characterized in that: The structures of the circular metal reflective back cavity (3) and the metal stepped shielding inner cavity (4) are rectangular structures, truncated cone structures, frustum structures or spherical structures.

9. The miniaturized ultra-wideband planar helical antenna based on magnetic medium according to claim 1, characterized in that: The circular metal reflective back cavity (3) is made of a conductive metal material such as copper, iron, steel, alloy, aluminum or tin.

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