A Miniaturized Ultra-Wideband Planar Spiral Antenna Based on Magnetic Medium

Abstract

The present invention relates to the technical field of microwaves and antennas, and specifically discloses a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium, aiming to overcome the problem that it is difficult to balance the indicators of miniaturization, ultra-wideband, high gain, circular polarization, etc. in the existing spiral antenna design. The spiral antenna structure includes an antenna radiation unit, a metal stepped shielding inner cavity, a balun feeding structure and a feeding connector, a circular metal reflection back cavity, and a magnetic medium material. By arranging the magnetic medium material below the radiation circuit in the present invention to regulate the surface current distribution at the end of the circuit and centrally regulate the magnitude and direction of the electromagnetic field vector in the cavity, the reduction of the lateral and longitudinal dimensions of the antenna is effectively achieved. Through the integrated design of the magnetic medium material and the antenna structure, the impedance matching bandwidth and axial ratio bandwidth of the miniaturized antenna can be improved while maintaining the high gain of the antenna, enabling an extremely high impedance matching bandwidth and maintaining excellent circular polarization characteristics within the bandwidth.

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 spiral antenna based on a magnetic medium, comprising:

[0006] An antenna radiation unit;

[0007] A magnetic medium material for regulating the surface current distribution at the end of the circuit and centrally regulating the magnitude and direction of the electric field vector of the electromagnetic reflection in the cavity;

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

[0009] A metal stepped shielding inner cavity disposed inside the circular metal reflection back cavity;

[0010] And a balun feeding structure for providing excitation to the antenna radiation unit and a feeding connector for connecting an external coaxial feeder;

[0011] A circular reflection stepped structure inner cavity and a feeding balun perforation structure are provided at the bottom of the metal stepped shielding inner cavity.

[0012] Preferably, the antenna radiation unit includes a dielectric substrate, and spiral arm 1 and spiral arm 2 printed above the dielectric substrate. Spiral arm 1 and spiral arm 2 are rotationally symmetric at 180° with the connection of the feeding balun via hole as the center. The line widths and intervals of spiral arm 1 and spiral arm 2 are kept consistent, and the areas of their metal and non-metal parts show a complementary relationship; there is no direct connection between spiral arm 1, spiral arm 2 and the circular metal reflection back cavity.

[0013] Preferably, the dielectric substrate is disposed on the circuit support step of the circular metal reflection back cavity to fix the circular metal reflection back cavity; spiral arm 1 and spiral arm 2 are a composite spiral line composed of one or more of an Archimedes function, an equiangular spiral function, a sin function or an equiangular function.

[0014] The spiral antenna is fed through an external balun. Since the characteristic impedance of the planar spiral structure radiator is stably in the range of 120 - 188 Ω, therefore, in order to ensure both the impedance matching of the radiator and the feeding structure and achieve the balun balance characteristic of the feeding structure. The balun feeding structure generally selects a microstrip balun, a coaxial balun and a transformer balun. Among them, the structural lengths of the microstrip balun and the 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 the length of the feeder needs to be reduced.

[0015] If the feeding balun uses a microstrip tapered balun feeding structure for feeding, then in order to reduce its size, the balun needs to be designed as 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 the feeding balun via connection points (104) provided on the dielectric substrate.

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

[0018] The position of the magnetic dielectric material is set below the radiation unit, or above the circular metal reflection back cavity, or in a partial area between the antenna radiation unit and the circular metal reflection back cavity;

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

[0020] The electromagnetic characteristics of the magnetic dielectric material are that the magnetic permeability is greater than 1 and the dielectric constant is greater than 1.

[0021] In the balun feeding structure, the unbalanced feeding end is connected to the dielectric substrate through the feeding balun perforation structure;

[0022] In the balun feeding structure, the balanced feeding end is connected to the coaxial feeder through the feeding joint provided on the side of the circular metal reflection back cavity.

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

[0024] Preferably, the distance between the antenna radiation unit and the circular metal reflection 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 reflection back cavity and the metal stepped shielding inner cavity can adopt various structures, including frustum structures, pyramid structures, or spherical structures, etc.

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

[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 setting a magnetic dielectric material below the radiation unit. Since the magnetic dielectric material has high magnetic permeability and dielectric constant, it can effectively confine the current on the metal surface, reduce its propagation speed on the spiral arms, and this method of regulating the surface current distribution effectively extends the equivalent path of the current;

[0029] And it can increase the equivalent reactance value of the circuit, improve the Q value, thereby reducing the low-frequency operating bandwidth of the antenna and realizing the reduction of the lateral size of the antenna.

[0030] 2) Due to the relatively high magnetic permeability of the magnetic medium material in the present invention, it can guide the distribution of the electromagnetic field and 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 material's magnetic permeability can be equivalent to resistance, the electromagnetic energy concentrated inside can be uniformly attenuated, thus achieving the effect of reducing the antenna height. Through the magnetic medium material, the impedance matching bandwidth and circular polarization performance of the miniaturized antenna can be improved. Combined with the L-shaped bending structure design of the balun, the height of the spiral antenna is further reduced, realizing the reduction of the longitudinal size of the antenna.

[0031] 3) By arranging a metal stepped shielding inner cavity inside the circular metal reflection back cavity in the present invention, the influence of the magnetic medium material on the electromagnetic loss in the high-frequency radiation area of the antenna can be effectively suppressed, thereby ensuring the radiation performance of the antenna in the high-frequency part. A circular reflection stepped structure inner cavity is arranged at the inner bottom of the shielding inner cavity in the present invention, which can effectively regulate the electromagnetic reflection characteristics of the metal inner cavity in the high-frequency region, making the reflection clutter in specific regions cancel each other out, thus effectively improving the axial ratio performance of the antenna and enabling the antenna to have good circular polarization characteristics. And because the antenna has the same height in the broadband range, compared with the low-frequency part, in the high-frequency part of the antenna, it is easy to have a situation where the distance between the reflection back cavity and the radiation unit is 1 / 2λ, which will cause the reflected electromagnetic wave and the forward radiation electromagnetic wave to cancel each other out, resulting in problems such as reduced gain efficiency and pattern depression. Therefore, through the regulation of the reflection phase of the electromagnetic wave in specific regions by the reflection stepped structure, the reflected electromagnetic wave in specific regions can be superposed positively with the radiation electromagnetic wave, well solving this problem. The present invention uses a metal conductor as the reflection back cavity, enabling the antenna to be actually applied to various installation platforms and expanding the application range of the antenna. 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 with a compact Archimedean spiral structure as the antenna radiation unit;

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

[0034] Figure 3 It is a reflection cavity structure diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the antenna radiation unit;

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

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

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

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

[0039] Figure 8 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the magnetic medium material being a circular ring structure;

[0040] Figure 9 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium loading with the magnetic medium material being a honeycomb structure;

[0041] Figure 10 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the magnetic medium material being a periodic distribution structure;

[0042] Figure 11 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the magnetic medium material above the internal space of the reflection back cavity;

[0043] Figure 12 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the magnetic medium material in the middle of the internal space of the reflection back cavity;

[0044] Figure 13 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the magnetic medium material below the internal space of the reflection back cavity;

[0045] Figure 14 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the reflection back cavity being a frustum of a cone structure;

[0046] Figure 15 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the reflection back cavity being a frustum of a pyramid structure;

[0047] Figure 16 It is the schematic diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with the reflection back cavity being a spherical structure;

[0048] Figure 17 It is the front circuit structure diagram of the L-shaped feed balun of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium;

[0049] Figure 18 It is the back circuit structure diagram of the L-shaped feed balun of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium;

[0050] Figure 19 It is the port reflection coefficient diagram of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element;

[0051] Figure 20 It is the axial ratio diagram of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element;

[0052] Figure 21 It is the radiation efficiency diagram of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element;

[0053] Figure 22 It is the radiation gain diagram of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element;

[0054] Figure 23 It is the radiation pattern in the xoz plane of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element at 0.5 GHz;

[0055] Figure 24 It is the radiation pattern in the xoz plane of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element at 1 GHz;

[0056] Figure 25 It is the radiation pattern in the xoz plane of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element at 2 GHz;

[0057] Figure 26 It is the radiation pattern in the xoz plane of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element at 3 GHz;

[0058] Figure 27 It is the radiation pattern in the xoz plane of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element at 4 GHz;

[0059] Figure 28 It is the radiation pattern in the xoz plane of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure as the antenna radiation element at 7 GHz;

[0060] Figure 29It is the radiation pattern in the xoz plane at 10 GHz of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure for the antenna radiation element;

[0061] In the figure, 1 - antenna radiation element; 2 - magnetic medium material; 3 - circular metal reflection 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 - connection point of the feeding balun via hole; 105 - dielectric substrate, 301 - circuit support step; 401 - inner cavity of the circular reflection stepped structure; 402 - feeding balun perforation structure; 501 - unbalanced feeding end; 502 - tapered exponential microstrip line; 503 - balanced feeding end. Detailed implementation manners

[0062] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

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

[0064] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship when the product of the invention is normally placed, or the orientation or positional relationship commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0065] In the description of the present invention, it should also be noted that, unless otherwise clearly specified and defined, the terms "set", "installed", "connected", and "coupled" 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 directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0066] The present invention provides a technical solution: a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium, as Figure 1 shown, comprising: an antenna radiation unit 1; a magnetic medium material 2 for regulating the surface current distribution at the end of the regulating circuit and concentrating the regulation of the magnitude and direction of the electromagnetic field vectors in the cavity; a circular metal reflection back cavity 3 disposed below the antenna radiation unit 1 for shielding the interference of the installation environment and reflecting electromagnetic waves for backward radiation (unidirectional radiation); a metal stepped shielding inner cavity 4 disposed inside the circular metal reflection back cavity 3 for suppressing the electromagnetic interference effect between the magnetic medium material 2 and the antenna radiation unit 1; and a balun feeding structure 5 for providing excitation for the radiation unit 1 and a feeding connector 6 for connecting an external coaxial feeder.

[0067] The bottom of the metal stepped shielding inner cavity 4 is provided with a circular reflection stepped structure inner cavity 401 and a feeding balun perforation structure 402.

[0068] Furthermore, in this technical solution, a magnetic medium material is disposed between the antenna radiation unit and the reflection back cavity for concentrating the regulation of the magnitude and direction of the electromagnetic field vectors in the cavity; the feeding balun adopts an L-shaped bending design, thereby achieving the effect of reducing the antenna height; by disposing the magnetic medium material to regulate the surface current distribution at the end of the circuit, and then combining with the composite circuit structure design of the antenna, the reduction of the lateral size of the antenna is achieved; and by combining the design of the shielding inner cavity in some specific areas, the purpose of improving the antenna performance is achieved.

[0069] Furthermore, as Figure 2 shown, the antenna radiation unit 1 includes a dielectric substrate 105, and spiral arms 1101 and 2102 printed above the dielectric substrate 105. The spiral arms 1101 and 2102 are rotationally symmetric at 180° with the feeding balun via connection point 104 as the center. The line widths and intervals of the spiral arms 1101 and 2102 are kept consistent, and the areas of their metal and non-metal parts show a complementary relationship; there is no direct connection between the spiral arms 1101, 2102 and the circular metal reflection back cavity 3.

[0070] As Figure 3As shown, the dielectric substrate 105 is disposed on the circuit support step 301 of the circular metal reflection cavity 3 to fix the circular metal reflection cavity 3, forming the overall structure of the antenna.

[0071] The spiral arms 1101 and 2102 can adopt various types of geometric shapes, including one or several of the Archimedean function, equiangular spiral function, sin function, or equiangular function, such as a compact composite Archimedean spiral structure, a Sin function bent spiral arm structure, an equiangular + bent spiral structure, etc., as shown respectively in Figure 1 , Figure 4 , Figure 6 .

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

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

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

[0075] The spiral arms 1101 and 2102 form the antenna radiation unit in a centrosymmetric manner. By adopting a compactly designed spiral coil in the present invention, the size of the antenna is significantly reduced at a lower frequency band.

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

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

[0078] The balun feeding structure 5 is a microstrip balun, a coaxial balun, and a transformer balun. The microstrip balun is composed of a substrate and tapered exponential microstrip lines 502 on both sides thereof, and is integrally L-shaped.

[0079] The balun feeding structure 5 is an L-shaped balun of a tapered exponential microstrip line circuit structure. The front view and the back view are as Figure 17 、 Figure 18 shown. A feeding balun perforation structure 402 is provided at the central position of the bottom of the metal stepped shielding inner cavity 4. One end of the tapered exponential 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 widths of the unbalanced feeding end and the balanced feeding end of the tapered exponential microstrip line are inconsistent, and the difference between the two line widths is about 5 times; the unbalanced feeding end 501 of the tapered exponential microstrip line 502 in the balun feeding structure 5 is connected to the dielectric substrate 105 through the feeding balun perforation structure 402; the balanced feeding end 503 of the tapered exponential microstrip line 502 in the microstrip balun feeding structure is connected to a coaxial feeder through a feeding joint 6 provided on the side surface of the circular metal reflection back cavity 3.

[0080] The tapered exponential microstrip line 502 can be designed into different shapes, such as stepped cascade shape, exponential change shape, hyperbolic function change shape, etc., to achieve broadband matching effects from different impedances to 50-ohm impedance.

[0081] The distance between the antenna radiation unit 1 and the circular metal reflection 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 dielectric material 2 in the circular metal reflection back cavity 3 can be set into different shape structures, such as ring structure, honeycomb structure, periodic distribution structure, etc., as shown in Figure 8 、 Figure 9 、 Figure 10 shown respectively; and the magnetic dielectric material 2 can have different installation positions in the circular metal reflection back cavity 3, such as above, in the middle, below in the cavity, etc., as shown in Figure 11 、 Figure 12 、 Figure 13 shown respectively, to reduce the mutual influence between the radiation unit 1 and the circular metal reflection back cavity 3.

[0083] The material type of the magnetic medium 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 medium material 2 has high magnetic permeability and dielectric constant (magnetic permeability greater than 1 and dielectric constant greater than 1), it can regulate the surface current distribution at the end of the circuit, extend the equivalent current path, and can centrally regulate the magnitude and direction of the electromagnetic vector between the antenna radiation unit 1 and the circular metal reflection back cavity 3, thereby reducing the antenna size while maintaining the antenna performance.

[0084] The circular metal reflection back cavity 3 can adopt various structures, including frustum reflection cavities, pyramid frustum reflection cavities, spherical reflection cavities, etc., such as Figure 14 , Figure 15 , Figure 16 shown. Different reflection cavity structures will have different effects on the impedance matching characteristics and radiation characteristics of the antenna.

[0085] Furthermore, the circular metal reflection back cavity 3 is specifically a conductive metal material, which can be conductors such as copper, iron, steel, alloy, aluminum, tin, etc., enabling the antenna to be actually applied to various installation platforms and expanding the application range of the antenna.

[0086] A miniaturized ultra-wideband planar spiral antenna based on magnetic medium provided by the present invention, on the premise of maintaining miniaturization (not greater than 0.1λ), the relative bandwidth of the antenna exceeds 181%, covering the frequency band of 500 MHz - 10 GHz. Within the working frequency band, the average gain of the antenna is about 6.5 dBi, the radiation efficiency of the antenna is about 80%, the axial ratio is maintained within 2, and a stable radiation pattern is obtained within the working frequency band.

[0087] Taking a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the antenna radiation circuit as an example, as Figure 19 shown, it is the port reflection coefficient diagram of an antenna with a compact Archimedean spiral structure as the radiation unit. The impedance matching performance of the antenna is good, the impedance bandwidth is 500 MHz - 10 GHz, and the relative bandwidth is 181%, belonging to an ultra-wideband antenna. Calculated according to the lowest frequency of 500 MHz of the antenna, the height of the antenna is only 0.05λ, far less than the height of 0.25λ of the traditional antenna. Compared with the case where the magnetic medium material is not applied, the application of the magnetic medium material significantly expands the bandwidth of the antenna in the low-frequency band. As Figure 20 shown, it is the axial ratio diagram of a miniaturized ultra-wideband planar spiral antenna based on magnetic medium with a compact Archimedean spiral structure as the radiation circuit. Under the action of the magnetic medium material, the axial ratio of the antenna is within 3 in the entire frequency band, having good circular polarization characteristics.

[0088] Such as Figure 21 and Figure 22As shown, they are respectively the radiation efficiency diagram and the antenna radiation gain diagram of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact composite Archimedean spiral structure as the radiation circuit. It can be seen from the figure that the efficiency of the antenna reaches 80% and is stable after 3 GHz, and the gain within the operating frequency band of the antenna is from -15 dBi to 10 dBi, with a relatively high and stable gain.

[0089] As Figure 23 shown, it is the xoz-plane radiation pattern of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact Archimedean spiral structure as the radiation circuit at 500 MHz. The radiation direction of the antenna is perpendicular to the ground upwards. The antenna is a directional radiator, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching -15 dBi. As Figure 24 shown, it is the xoz-plane radiation pattern of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact Archimedean spiral structure as the radiation circuit at 1 GHz. The radiation direction of the antenna is perpendicular to the ground upwards. The antenna is a directional radiator, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching 0 dBi.

[0090] As Figure 25 shown, it is the xoz-plane radiation pattern of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact Archimedean spiral structure as the radiation circuit at 2 GHz. The radiation direction of the antenna is perpendicular to the ground upwards. The antenna is a directional radiator, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching 5 dBi. As Figure 26 shown, it is the xoz-plane radiation pattern of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact Archimedean spiral structure as the radiation circuit at 3 GHz. The radiation direction of the antenna is perpendicular to the ground upwards. The antenna is a directional radiator, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching 10 dBi.

[0091] As Figure 27 shown, it is the xoz-plane radiation pattern of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact Archimedean spiral structure as the radiation circuit at 4 GHz. The radiation direction of the antenna is perpendicular to the ground upwards. The antenna is a directional radiator, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching 7 dBi. As Figure 28 shown, it is the xoz-plane radiation pattern of a magneto-dielectric-based miniaturized ultra-wideband planar spiral antenna with a compact Archimedean spiral structure as the radiation circuit at 7 GHz. The radiation direction of the antenna is perpendicular to the ground upwards. The antenna is a directional radiator, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching 7 dBi.

[0092] As Figure 29 shown, it is the radiation pattern in the xoz plane at 10 GHz of a miniaturized ultra-wideband planar spiral antenna based on a magnetic medium with a compact Archimedean spiral structure for the radiation circuit. The radiation direction of the antenna is vertically upward perpendicular to the ground. The antenna is directionally radiating, and the radiation pattern has good symmetry and unidirectional radiation ability, with a radiation gain reaching 8 dBi.

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

[0094] Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A miniaturized ultra-wideband planar spiral antenna based on magnetic medium, characterized in that Comprising: Antenna radiation unit (1); Magnetic dielectric material (2) for regulating the surface current distribution at the end of the circuit and centrally regulating the magnitude and direction of the electromagnetic field vector in the cavity; Circular metal reflection back cavity (3) disposed below the antenna radiation unit (1) to reflect electromagnetic waves for backward radiation; Metal stepped shielding inner cavity (4) disposed inside the circular metal reflection back cavity (3); And a balun feeding structure (5) for providing excitation to the antenna radiation unit (1) and a feeding joint (6) for connecting an external coaxial feeder; The bottom of the metal stepped shielding inner cavity (4) is provided with a circular reflection stepped structure inner cavity (401) and a feeding balun perforation structure (402); The magnetic dielectric material (2) is filled between the metal stepped shielding inner cavity (4) and the circular metal reflection back cavity (3); The position of the magnetic dielectric material (2) is set below the radiation unit (1), or above the circular metal reflection back cavity (3), or in a partial area between the antenna radiation unit (1) and the circular metal reflection back cavity (3); The material type of the magnetic dielectric material (2) is one or more of inorganic magnetic materials, organic magnetic materials, and composite magnetic materials; The electromagnetic characteristics of the magnetic dielectric material (2) are that the magnetic permeability is greater than 1 and the dielectric constant is greater than 1; The distance between the antenna radiation unit (1) and the circular metal reflection 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.

2. The miniaturized ultra-wideband planar spiral antenna based on magnetic medium according to claim 1, wherein: The antenna radiation unit (1) includes a dielectric substrate (105), and a spiral arm 1 (101) and a spiral arm 2 (102) printed above the dielectric substrate (105). The spiral arm 1 (101) and the spiral arm 2 (102) are rotationally symmetric by 180° with the feeding balun via connection point (104) as the center. The line widths and intervals of the spiral arm 1 (101) and the spiral arm 2 (102) are kept consistent, and the areas of their metal and non-metal parts show a complementary relationship. There is no direct connection between the spiral arm 1 (101), the spiral arm 2 (102) and the circular metal reflection back cavity (3).

3. The miniaturized ultra-wideband planar spiral antenna based on a magnetic medium according to claim 2, wherein: The dielectric substrate (105) is disposed on the circuit support step (301) of the circular metal reflection back cavity (3) to realize the fixation of the circular metal reflection back cavity (3). The spiral arm 1 (101) and the spiral arm 2 (102) are composite spiral lines composed of one or several of the Archimedes function, equiangular spiral function, sin function or equiangular function.

4. The miniaturized ultra-wideband planar spiral antenna based on magnetic medium according to claim 1, wherein: The balun feeding structure (5) is any one of a microstrip balun, a coaxial balun, and a transformer balun. The microstrip balun is composed of a substrate and tapered exponential 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 through the feeding balun via connection point (104) and the fan-shaped transition structure (103) disposed on the dielectric substrate (105).

5. The miniaturized ultra-wideband planar spiral antenna based on magnetic medium according to claim 4, wherein: One end of the balun feeding structure (5) is an unbalanced feeding end (501), and the other end is a balanced feeding end (503); In the balun feeding structure (5), the unbalanced feeding end (501) is connected to the dielectric substrate (105) through the feeding balun perforation structure (402); In the balun feeding structure (5), the balanced feeding end (503) is connected to the coaxial feeder through the feeding joint (6) arranged on the side surface of the circular metal reflection back cavity (3).

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

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

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