All-metal evanescent wave miniaturized broadband filtering antenna based on rectangular waveguide

Abstract

The invention discloses an all-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide, and belongs to the technical field of waveguide antennas. Comprising a first metal cavity, a second metal cavity, a first evanescent wave coupling structure, a second evanescent wave coupling structure and a feed probe which are assembled through screws to form a compact rectangular waveguide structure. The first coupling structure and the second coupling structure are aluminum gap metal columns, through cooperation of equivalent LC resonance and double resonance points, double-pole broadband work is achieved below the cut-off frequency, two radiation zero points are generated at the high frequency band above the cut-off frequency, and broadband suppression is achieved. The antenna adopts an all-metal integrated design, has the characteristics of miniaturization, high temperature resistance, vibration resistance and electromagnetic interference resistance, and is suitable for a high-power compact scene of an industrial automation platform. Through evanescent wave-radiation wave conversion, dual-resonance bandwidth expansion and a self-filtering mechanism, the technical contradictions that a traditional metal antenna is large in size, narrow in bandwidth and free of a filtering function are solved, and the antenna has remarkable engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of waveguide antennas, and more particularly to a fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide, which is applicable to the antenna design of industrial automation platforms. Background Art

[0002] Currently, with the rapid development of wireless terminals, wireless charging, and communication technologies, the demand for antenna miniaturization and multifunctionality in compact platforms such as vehicle-mounted communication, industrial automation scenarios, and airborne communication is becoming increasingly urgent. In industrial automation platforms, antennas are usually required to have mechanical stability and adaptability to high and low temperature environments, and also need to have miniaturization characteristics to meet the installation on devices with limited space such as robotic arms and AGVs (Automated Guided Vehicles). In addition, excellent out-of-band rejection capabilities can effectively resist interference sources such as motors, frequency converters, and wireless devices in industrial environments, ensuring communication stability. Therefore, researching miniaturized fully metallic broadband filtering antennas that meet the above application requirements has great industrial appeal.

[0003] Traditional fully metallic cavity antennas (such as horn antennas and cavity slot antennas) have characteristics such as low loss, strong mechanical stability, and high temperature resistance. However, due to relying on the transverse resonance of the fundamental mode or higher-order modes, they are bulky and difficult to adapt to modern communication platforms with limited dimensions. The challenge faced by the technology is to achieve the miniaturization and multifunctionality of waveguide antennas. Existing methods include substrate integrated waveguide technology, near-field resonance parasitic technology, and evanescent wave coupling technology. Substrate integrated waveguide technology integrates cavity antennas on a dielectric substrate and uses the dielectric constant to reduce the physical size, having characteristics such as low loss and high efficiency. However, due to the filling of the dielectric substrate, it is not conducive to the design of high temperature and high power resistance; near-field resonance parasitic technology (through compact structures such as metal strips, rings, and slots) can achieve electrically small, circularly polarized, and high-efficiency antenna designs. However, the antennas designed by this technology usually have a narrow bandwidth and no filtering effect itself, and additional capacitors need to be loaded to introduce a filtering response; evanescent wave coupling technology couples waves below the cut-off frequency by loading specific boundary conditions in the waveguide, having natural miniaturization advantages. However, there are still challenges in expanding the bandwidth and introducing radiation zeros.

[0004] In response to the above problems, existing evanescent wave antenna research has proposed methods such as loading capacitive metasurfaces, using Smith charts, loading capacitive coupling posts, and loading dielectric resonators to expand the evanescent wave frequency band bandwidth or improve out-of-band rejection. However, most of the work does not have a fully metallic integrated design and is difficult to apply in high-power and high-temperature platforms. In addition, although there are also evanescent wave antennas that achieve a filtering response, the frequency selectivity and out-of-band rejection range are not ideal. Therefore, it is very necessary to develop a fully metallic waveguide antenna technology with a simple structure, miniaturization, broadband, and excellent out-of-band filtering capabilities. Summary of the Invention

[0005] The object of the present invention is to provide a fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide for use in an industrial automation compact platform. The overall design is compact, and miniaturization, broadband and filtering performance are achieved through the loaded evanescent wave coupling structure, meeting the requirements for miniaturization, environmental reliability and filtering of antennas in industrial automation systems.

[0006] To achieve the above object, the present invention provides a fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide, comprising a first metal cavity, a second metal cavity, a first evanescent wave coupling structure, a second evanescent wave coupling structure and a feeding probe; the first metal cavity and the second metal cavity are assembled by screws to form a rectangular waveguide structure; the first evanescent wave coupling structure and the second evanescent wave coupling structure are respectively located in the first metal cavity and the second metal cavity; the feeding probe is vertically arranged in the first metal cavity.

[0007] Preferably, the aperture heights of the first metal cavity and the second metal cavity are both H2, and the widths are both W2;

[0008] The height of the first metal cavity is H1, and the width is W1;

[0009] The height and width of the second metal cavity are the same as those of the first metal cavity.

[0010] Preferably, the first evanescent wave coupling structure is a slotted metal post, made of aluminum, with a diameter of d1, a slot height of h2, a distance of h1 from the upper wall of the first metal cavity, and a slot width of 1 mm;

[0011] The first evanescent wave coupling structure is located behind the feeding probe, with distances of w1 and w2 from the side walls of the first metal cavity respectively, and distances of l1 and l2 from the front and rear walls of the first metal cavity respectively;

[0012] Preferably, the second evanescent wave coupling structure is a slotted metal post, made of aluminum, with a diameter of d2, a slot height of h4, a distance of h3 from the upper wall of the second metal cavity, and a slot width of 1 mm;

[0013] The geometric parameters of the first evanescent wave coupling structure and the second evanescent wave coupling structure are optimized to generate two resonance points in the evanescent wave frequency band, thereby achieving broadband operation.

[0014] The second evanescent wave coupling structure is located at the aperture of the second metal cavity, with distances of w3 and w4 from the side walls of the second metal cavity respectively, and distances of l3 and l4 from the front and rear walls of the second metal cavity respectively.

[0015] Preferably, the feeding probe is located within the first metal cavity, and the position where the probe is arranged is close to the cavity sidewall, which is used to improve the out-of-band suppression depth of the antenna. The distance between the probe and the sidewall of the first metal cavity is p1, and the distance between the probe and the aperture of the first metal cavity is p2.

[0016] Preferably, the first evanescent wave coupling structure and the second evanescent wave coupling structure are respectively located on the front and rear sides of the feeding probe, which are used to regulate the bandwidth expansion in the evanescent wave frequency band.

[0017] Preferably, the first evanescent wave coupling structure and the second evanescent wave coupling structure generate out-of-band radiation nulls through an equivalent inductance-capacitance series loop to achieve the high-frequency suppression function, and the suppression range is 3.8 - 7.8 GHz.

[0018] Preferably, the all-metal evanescent wave broadband filtering antenna based on a rectangular waveguide meets the impedance matching requirement of |S11| ≤ -10 dB in the frequency range of 2.96 - 3.44 GHz.

[0019] Preferably, the overall size of the all-metal evanescent wave broadband filtering antenna based on a rectangular waveguide is 0.43×0.22×0.25λ3, the radiation efficiency within the working frequency band is greater than 80%, and the peak gain is 4.2 dBi.

[0020] Preferably, the all-metal evanescent wave broadband filtering antenna based on a rectangular waveguide adopts an all-metal integrated design, and the material is aluminum.

[0021] Preferably, the filtering performance is achieved through the equivalent short-circuit resonance loop of the first evanescent wave coupling structure and the second evanescent wave coupling structure. By controlling the geometric parameters of the first evanescent wave coupling structure and the second evanescent wave coupling structure and their arrangement positions within the cavity, radiation nulls are formed in the out-of-band frequency band, thereby improving the filtering performance.

[0022] Therefore, the all-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide with the above structure in the present invention has the following beneficial effects:

[0023] (1) Broadband performance: The present invention realizes broadband operation without increasing the extra size of the antenna by coupling evanescent waves. The working frequency band is 2.96 - 3.44 GHz, and the relative bandwidth is 15%.

[0024] (2) Filtering performance: The present invention takes a 10 dB gain drop within the antenna working frequency band as the suppression benchmark, and the out-of-band suppression frequency range covers 3.8 - 7.8 GHz. The depths of the two radiation nulls are -34.6 dB and -31.3 dB respectively.

[0025] (3) Miniaturized design: The structure of the present invention is compact, with an overall electrical size of 0.43×0.22×0.25λ3, and at the same time, a flat gain greater than 3.8 dBi within the bandwidth is achieved, and the peak gain is 4.2 dBi.

[0026] (4) Environmental reliability: The present invention adopts an all-metal integrated design, with high mechanical strength and high temperature resistance characteristics.

[0027] (5) Simple and efficient: By loading slotted metal posts in the cavity, the present invention avoids filling a cutoff substrate, effectively reducing the design complexity, while ensuring high performance and low loss.

[0028] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0030] Figure 2 It is a front view of the first metal cavity in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0031] Figure 3 It is a side view of the first metal cavity in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0032] Figure 4 It is a front view of the second metal cavity in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0033] Figure 5 It is a side view of the second metal cavity in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0034] Figure 6 It is a reflection coefficient curve graph of simulation and test in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0035] Figure 7 It is an achievable gain graph of simulation and test in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0036] Figure 8 It is an efficiency graph of simulation and test in a full-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0037] Figure 9This is the radiation pattern measured at 3 GHz for a fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0038] Figure 10 This is the radiation pattern measured at 3.3 GHz for a fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to the present invention;

[0039] Reference Signs

[0040] 1 - First metal cavity; 2 - First evanescent wave coupling structure; 3 - Second metal cavity; 4 - Second evanescent wave coupling structure; 5 - Feeding post. Detailed Embodiment

[0041] The technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0042] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those of ordinary skill in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" mean that the elements or items appearing before this term cover the elements or items listed after this term and their equivalents, without excluding other elements or items. The terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms such as "upper", "lower", "left" and "right" are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0043] Embodiment

[0044] As Figures 1-5 shown, the present invention provides a fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide, including a first metal cavity 1, a first evanescent wave coupling structure 2, a second metal cavity 3, a second evanescent wave coupling structure 4, and a feeding probe 5. The rectangular waveguide cavity in the present invention is composed of the first metal cavity 1 and the second metal cavity 3.

[0045] The first metal cavity 1 has a height of H1, a width of W1, a cavity aperture height of H2, an aperture width of W2, a total length of L1, and a cavity length of L2.

[0046] The second metal cavity 3 has the same height, width, aperture height and aperture width as the first metal cavity 1, and a total length of L3.

[0047] The first evanescent wave coupling structure 2 is located inside the first metal cavity 1, with distances of w1 and w2 respectively from the side walls of the first metal cavity 1, and distances of l1 and l2 respectively from the front and back of the first metal cavity 1. The diameter of this evanescent wave coupling structure is d1.

[0048] The second evanescent wave coupling structure 4 is located inside the second metal cavity 3, with distances of w3 and w4 respectively from the side walls of the second metal cavity, and distances of l3 and l4 respectively from the front and back of the first metal cavity 1. The diameter of this evanescent wave coupling structure is d2.

[0049] The feeding probe 5 is located inside the first metal cavity 1, with a distance of p1 from the side wall of the first metal cavity 1 and a distance of p2 from the aperture of the first metal cavity 1.

[0050] Table 1 Optimal size table of each parameter of the present invention

[0051]

[0052]

[0053] According to the above structure and parameters, the performance of the designed antenna is simulated using HFSS software, the reflection coefficient is measured using a vector network analyzer, and the far field is measured in an anechoic chamber environment. The simulation and measurement results are as follows:

[0054] Reflection coefficient: As Figure 6 shown, the antenna simulation / measurement meets the matching performance of |S11| ≤ -10 dB in the frequency range of 2.92 - 3.41 GHz / 2.96 - 3.44 GHz.

[0055] Filtering performance: As Figure 7 shown, in the normal direction (Phi = 90°, Theta = 90°), the peak gain within the simulated / measured bandwidth is 4.38 dBi / 4.19 dBi, the zero depths are -34.8 dB / -30.4 dB and -22.6 dB / -28.5 dB respectively, and the frequency suppression range is 3.82 - 7.5 GHz / 3.8 - 7.8 GHz.

[0056] Radiation efficiency: As Figure 8 shown, the radiation measurement efficiency of the antenna within the operating frequency band of 2.96 - 3.44 GHz is > 80%.

[0057] Pattern performance: As Figures 9-10 shown, the antenna effectively radiates in the maximum radiation direction at the resonance points of 3 GHz and 3.3 GHz.

[0058] The core working mechanism of the present invention lies in evanescent wave - radiation wave conversion, dual - resonance bandwidth expansion, and self - filtering radiation zero generation, specifically as follows:

[0059] Evanescent wave - radiation wave conversion

[0060] By designing the cross - sectional dimensions of the rectangular waveguide (aperture width W2 = 40.4 mm, height H2 = 20.2 mm), the cut - off frequency is set to 3.71 GHz, so that the operating frequency band of 2.96 - 3.44 GHz is in the evanescent wave region of the waveguide.

[0061] The aluminum slotted metal posts (diameter d1 = 3.6 mm / d2 = 1 mm, slot width 1 mm) perturb the electromagnetic field through geometric discontinuities, and efficiently convert the evanescent wave energy below the cut - off frequency into the radiation mode.

[0062] Dual - resonance bandwidth expansion

[0063] Dual - resonance point design: The front - coupling structure (distance from the feeding probe l1 = 7.6 mm) excites the low - frequency resonance (2.96 GHz), and the rear - coupling structure (distance from the aperture l3 = 0.7 mm) generates the high - frequency resonance (3.44 GHz). By optimizing the spacing (l2 = 16 mm, l4 = 3.8 mm), the impedance - matching frequency bands of the two resonance points overlap, achieving a relative bandwidth of 15% (2.96 - 3.44 GHz).

[0064] Hybrid - mode excitation: The lateral offsets of the metal posts (w1 = 5.2 mm, w3 = 14.58 mm) break the waveguide symmetry, exciting the quasi - TE101 and TE102 hybrid modes, and broadening the impedance - matching range.

[0065] Self - filtering radiation null generation

[0066] Equivalent LC resonance: The slotted metal posts are equivalent to a series LC circuit in the high - frequency band (3.8 - 7.8 GHz) (d1 / d2 controls the inductance, and the slot size determines the capacitance), forming radiation nulls with depths of - 34.6 dB / -31.3 dB at 4.5 GHz and 6.5 GHz.

[0067] Cancellation interference suppression: The second coupling structure excites a reverse current, which generates cancellation interference with the main radiation field, achieving a wide stop - band characteristic with a sharp 10 - dB gain drop in the range of 3.8 - 7.8 GHz.

[0068] Meanwhile, the physical size of the present invention is 66.4×35.2×20.2 mm 3 (0.43×0.22×0.25λ3), with a 68% reduction in volume compared to traditional waveguide antennas. The coupling structure simultaneously undertakes the functions of impedance matching, resonance excitation, and filtering, avoiding the volume increase introduced by additional circuits.

[0069] It is seamlessly assembled by screws in an aluminum cavity (thermal conductivity 237 W / m·K), with high temperature resistance (efficiency > 80%), vibration resistance (wall thickness 5 mm), and electromagnetic interference resistance. And there is no medium filling, the radiation efficiency > 80%, the peak gain reaches 4.2 dBi, and the gain flatness is excellent.

[0070] Through the optimized cavity design and evanescent wave coupling structure, the present invention realizes miniaturization, broadband, and filtering performance, and is applicable to high-temperature and high-power compact platforms in industrial environments.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide, characterized in that: It includes a first metal cavity, a second metal cavity, a first evanescent wave coupling structure, a second evanescent wave coupling structure and a feeding probe; the first metal cavity and the second metal cavity are assembled by screws to form a rectangular waveguide structure; the first evanescent wave coupling structure and the second evanescent wave coupling structure are respectively located in the first metal cavity and the second metal cavity; the feeding probe is vertically arranged in the first metal cavity.

2. The all-metal evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to claim 1, characterized in that: The aperture heights of the first metal cavity and the second metal cavity are both H2, and the widths are both W2; The height of the first metal cavity is H1, and the width is W1; The height and width of the second metal cavity are the same as those of the first metal cavity.

3. A miniaturized broadband filtering antenna based on a rectangular waveguide and evanescent wave according to claim 1, characterized in that: The first evanescent wave coupling structure is a slotted metal post, its material is aluminum, its diameter is d1, the slot height is h2, and the distance from the slot to the upper wall of the first metal cavity is h1; The first evanescent wave coupling structure is located behind the feeding probe, and the distances from the side walls of the first metal cavity are w1 and w2 respectively, and the distances from the front and rear walls of the first metal cavity are l1 and l2 respectively.

4. A miniaturized broadband filtering antenna based on a rectangular waveguide with evanescent waves as claimed in claim 1, characterized in that: The second evanescent wave coupling structure is a slotted metal post, the material is aluminum, its diameter is d2, the slot height is h4, and the distance from the slot to the upper wall of the second metal cavity is h3; The second evanescent wave coupling structure is located at the aperture of the second metal cavity, and the distances from the side walls of the second metal cavity are w3 and w4 respectively, and the distances from the front and rear walls of the second metal cavity are l3 and l4 respectively.

5. A miniaturized broadband filtering antenna based on a rectangular waveguide with evanescent waves according to claim 1, characterized in that: The feeding probe is located in the first metal cavity, the distance from the side wall of the first metal cavity is p1, and the distance from the aperture of the first metal cavity is p2.

6. A fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to claim 1, characterized in that: The first evanescent wave coupling structure and the second evanescent wave coupling structure are respectively located on the front and rear sides of the feeding probe, and are used to regulate the bandwidth expansion in the evanescent wave frequency band.

7. A fully metallic evanescent wave miniaturized broadband filtering antenna based on a rectangular waveguide according to claim 1, characterized in that: The first evanescent wave coupling structure and the second evanescent wave coupling structure generate out-of-band radiation nulls through an equivalent inductance-capacitance series circuit.

8. A miniaturized broadband filtering antenna based on a rectangular waveguide using evanescent waves according to claim 1, characterized in that: The all-metal evanescent wave broadband filtering antenna based on a rectangular waveguide meets the impedance matching requirement of |S11| ≤ -10 dB in the frequency range of 2.96 - 3.44 GHz.

9. A miniaturized broadband filtering antenna based on a rectangular waveguide and evanescent wave according to claim 1, characterized in that: The radiation efficiency within the operating frequency band of the all-metal evanescent wave broadband filtering antenna based on a rectangular waveguide is greater than 80%.

10. A miniaturized broadband filtering antenna based on a rectangular waveguide with evanescent waves according to claim 1, characterized in that: The all-metal evanescent wave broadband filtering antenna based on a rectangular waveguide adopts an all-metal integrated design, and the material is aluminum.

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