A triple-band conformal omnidirectional antenna

Abstract

The present invention discloses a three-frequency conformal omnidirectional antenna, belonging to the field of antenna technology. It includes a dielectric substrate, a microstrip feeder and a radiation unit located on the upper surface of the dielectric substrate; it is characterized in that the radiation unit includes a T-shaped branch arranged in sequence from top to bottom, a first rectangular patch etched with a first U-shaped gap and a U-shaped branch etched with a second U-shaped gap; the top of the rectangular patch is connected to the vertical section of the T-shaped branch; a feeding port is provided at the bottom of the dielectric substrate; one end of the microstrip feeder is connected to the bottom of the rectangle, and the other end is connected to the feeding port; the opening of the U-shaped branch is upward; the lower surface of the dielectric substrate is provided with a second rectangular patch, an electric field coupling resonator and a metal floor arranged in sequence from top to bottom. The present invention is suitable for unmanned aerial vehicle platforms, and has good horizontal plane omnidirectional radiation characteristics and low cross-polarization characteristics.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a triple-band conformal omnidirectional antenna. Background Art

[0002] Usually, multi-rotor UAVs communicate with ground control equipment through a monopole antenna working in a single frequency band placed in the landing gear of the UAV. However, the electromagnetic environment is complex nowadays, and multi-rotor UAVs are susceptible to electromagnetic interference. Once the communication signal is interfered with, it may block the communication between the ground control station and the UAV, endangering its flight safety. The three-band conformal omnidirectional antenna working in the three-band UAV communication has multi-frequency and omnidirectional characteristics, which can reduce the risk of unsafe flight caused by interference from the communication link and ensure the communication quality of the UAV. It can be conformal to the landing gear of the UAV to save the carrying space on the UAV, so it is of great significance to study it.

[0003] Cui Yuehui and Luo Peng published "A Compact Tri-Band Horizontally Polarized Omnidirectional Antenna for UAV Applications" in 2019, which disclosed a knife-shaped horizontally polarized omnidirectional antenna operating in the three-band UAV communication. A folded patch is loaded in a metal box with a vertical slot, and the first-order and second-order resonant modes of the folded patch are used to operate in the low and high frequency bands of UAV communication. The slot mode excited by the folded patch generates the UAV communication mid-band, which can specifically cover the three frequency bands of 840MHz-847MHz, 1422MHz-1467MHz and 2270MHz-2531MHz. It has low cross-polarization in the three frequency bands, and the gain changes in the horizontal plane are less than 2dB, 3dB, and 5dB, respectively. The omnidirectionality is poor, and the overall size is 0.32λ 0 ×0.16λ 0 ×0.08λ 0 (where λ 0 is the free space wavelength corresponding to the central resonant frequency of the antenna in the low frequency band), and the size is relatively large. Therefore, from a technical point of view, the horizontal omnidirectional radiation characteristics and miniaturization degree of the antenna can be improved. Summary of the invention

[0004] In view of this, the present invention provides a triple-frequency conformal omnidirectional antenna. The present invention has a multi-frequency conformal communication antenna with good horizontal plane omnidirectional radiation characteristics and a smaller antenna size. The antenna is conformal to the UAV platform, saving the carrying space on the UAV.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A triple-band conformal omnidirectional antenna, comprising a dielectric substrate, a microstrip feeder and a radiating unit located on the upper surface of the dielectric substrate; the radiating unit comprises a T-shaped branch, a first rectangular patch etched with a first U-shaped slot and a U-shaped branch etched with a second U-shaped slot, which are arranged in sequence from top to bottom; the top of the rectangular patch is connected to the vertical section of the T-shaped branch; a feeding port is provided at the bottom of the dielectric substrate; one end of the microstrip feeder is connected to the bottom of the rectangle, and the other end is connected to the feeding port; the opening of the U-shaped branch faces upward;

[0007] The lower surface of the dielectric substrate is provided with a second rectangular patch, an electric field coupling resonator and a metal floor in order from top to bottom; the electric field coupler is located on the back of the first rectangular patch; a rectangular gap perpendicular to the microstrip feeder is provided on the metal floor, and the projection of the metal floor on the upper surface is close to the U-shaped branch.

[0008] Furthermore, the opening of the first U-shaped gap is upward, the horizontal section of the first U-shaped gap is in close contact with the bottom edge of the first rectangular patch, and the vertical section of the first U-shaped gap is in close contact with the side edge of the corresponding first rectangular patch.

[0009] Furthermore, the horizontal section of the second U-shaped slot is located on the horizontal section of the U-shaped branch, and the vertical section of the second U-shaped slot is located on the vertical section of the corresponding U-shaped branch; the overlapping part of the microstrip feed line and the U-shaped branch has a hollow portion constituting the second U-shaped slot.

[0010] Furthermore, the horizontal section of the T-shaped branch is bent downward and has no contact with the first rectangular patch.

[0011] Furthermore, the electric field coupler includes a rectangular ring and a T-shaped metal strip located inside the rectangular ring; the vertical sections of the two T-shaped metal strips are respectively connected to the top and bottom edges of the rectangular ring, the horizontal sections of the two T-shaped metal strips are parallel to the top edge of the rectangular ring, and the two horizontal sections are opposite.

[0012] The beneficial effects of the above technical solution of the present invention are:

[0013] The present invention realizes multi-frequency characteristics through the multi-branch method and the multi-slot method, can work in the three-band of UAV communication, and realizes the miniaturization of the antenna through branch bending, etching slots and adding electric field coupling resonator structure. It is suitable for UAV platforms and has good horizontal plane omnidirectional radiation characteristics and low cross-polarization characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0015] Figure 2 It is a bottom view structural schematic diagram of the present invention;

[0016] Figure 3It is a front view structural schematic diagram of the present invention;

[0017] Figure 4 It is a rear view structural schematic diagram of the present invention;

[0018] Figure 5 1 is a diagram of the reflection coefficient simulation result of Example 1 of the present invention;

[0019] Figure 6 This is the xoy plane radiation pattern at the low frequency center resonant frequency of 842 MHz of Example 1 of the present invention.

[0020] Figure 7 This is the xoy plane radiation pattern at the mid-frequency center resonant frequency of 1437 MHz of Example 1 of the present invention.

[0021] Figure 8 This is the xoy plane radiation pattern at the high frequency band center resonant frequency of 2425 MHz of Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] The present invention proposes a triple-band conformal omnidirectional antenna, the purpose of which is to realize a multi-band conformal communication antenna that works in three frequency bands of UAV communication and has good horizontal plane omnidirectional radiation characteristics and a smaller antenna size. The antenna is conformal to the UAV platform, saving space on the UAV.

[0025] The technical solution adopted by the present invention includes a dielectric substrate 1, a microstrip feed line 2, a feeding port 3, a radiating unit 4, an electric field coupling resonator 5 located on the back of the dielectric substrate, a metal floor 6 located on the back of the dielectric substrate, and a rectangular patch 7:

[0026] The microstrip feed line 2 is located on the upper surface of the dielectric substrate and has an overall length of L 2 , width W 2 , one end is connected to the feeding port 3.

[0027] The feeding port 3 is located at the front end of the dielectric substrate and feeds the radiation unit through the microstrip feed line 2 .

[0028] The radiation unit 4 includes a rectangular patch 41 etched with a U-shaped gap 44, a U-shaped branch 42 with a U-shaped gap 45 located on the feeder, and a bent T-shaped branch 43. The rectangular patch 41 is connected to the other end of the feeder, and the T-shaped branch 43 is connected to the top part of the rectangular patch 41.

[0029] The electric field coupling resonator 5 is located directly below the rectangular patch 41 and includes a rectangular ring 51 and two T-shaped metal strips 52 located in the middle of the rectangular ring and facing each other. The vertical part of the T-shaped metal strip is connected to the inner part of the rectangular ring.

[0030] The metal floor 6 is etched with rectangular gaps 61 .

[0031] The rectangular patch 7 is located on the top of the lower surface of the dielectric substrate.

[0032] The dielectric substrate 1 has an overall length of L, a width of W, and a height of h.

[0033] The length of the radiating unit 4, the rectangular patch 41 is L 3 , width W 3 , connected to the feeding port 3 through the microstrip feed line 2 to generate resonance. There is a vertical segment with a length of L etched on it. s1 , the length of the horizontal section is L s2 , width W s1 The U-shaped gap 44 increases the effective path of the current on the antenna surface, and the resonant frequency generated by the rectangular patch 41 moves to a low frequency. At the same time, a new current loop is introduced, and the U-shaped gap 44 also introduces a new resonant point. The vertical section length of the U-shaped branch 42 is L 4 , the length of the horizontal section is L e , width W 4 , the vertical length of the U-shaped slot 45 etched thereon is L 5 , the length of the horizontal section is L e , width W 5 The branch is located on the microstrip feeder, which extends the current path. The resonant frequency generated by the rectangular patch 41 is further reduced. Due to the introduction of additional branches, the U-shaped branch 42 will also generate a new resonant frequency. The length of the part of the added bent T-shaped branch 43 connected to the top of the rectangular patch 41 is L t1 , width W t1 , the length of the horizontal section of the bend is L t2 , the length of the vertical segment is L t3 , width W tThe introduction of the T-shaped branch 43 extends the current path, reduces the low-frequency resonance frequency, and provides a new degree of freedom for tuning the low-frequency resonance frequency, so that the frequency point can be adjusted separately. In order not to increase the overall size of the antenna, a bending process is performed, thereby changing the current loop on the antenna surface and generating additional frequency points.

[0034] The electric field coupling resonator 5 has a symmetrical structure. The maximum size of the rectangular ring 51 is L_1×W_1, and its internal size is L_2×W_2. Two T-shaped metal strips 52 are placed in the middle of the rectangular ring 51 and are spaced apart by a certain distance. The horizontal length of the T-shaped metal strip 52 is l g , with a width of g1, the resonator can be equivalent to a parallel LC resonant circuit, the strips on both sides can be equivalent to inductors, and the opposite T-shaped strip 52 structure is equivalent to capacitors. This structure is placed on the lower surface of the dielectric substrate, which is equivalent to connecting the interlayer capacitors in parallel to the entire antenna structure, so that all resonant frequencies are shifted to the left, further realizing the miniaturization of the antenna, while affecting the matching of the resonant frequencies generated by the bending of the branches, reducing its resonant depth, and reducing the impact on the antenna's operating frequency band. Through coupling with the upper rectangular patch 41, the electric field coupled resonator 5 also generates a resonant frequency, which is close to the resonant frequency generated by the U-shaped gap 44 etched on the rectangular patch 41, and can be merged into one frequency band.

[0035] The metal floor 6 is a rectangular structure with a length of L g1 , with a width of W, and a rectangular slot 61 etched thereon, located at a distance L from the feed port 3 on the floor d The length is L S , width W S , used to improve antenna matching.

[0036] The rectangular patch 7 is placed at the uppermost end of the lower surface of the dielectric substrate, and its length along the width direction of the dielectric substrate is W. r , the length along the length direction of the dielectric substrate is L r , used to improve the impedance matching of the antenna, especially in the low frequency band.

[0037] The following is a more specific embodiment 1:

[0038] refer to Figure 1 and Figure 2 A triple-band conformal omnidirectional antenna for unmanned aerial vehicle communication includes a dielectric substrate 1, a microstrip feed line 2, a feeding port 3, a radiation unit 4, an electric field coupling resonator 5 located on the back of the dielectric substrate, a metal floor 6 and a rectangular patch 7.

[0039] The dielectric substrate 1 is a F4B cuboid with a relative dielectric constant of 2.65 and a loss tangent of 0.003, and has a length of 76 mm, a width of 19 mm, a thickness of 0.5 mm, and an overall size of 0.21λ. 0 ×0.05λ 0 ×0.001λ 0 (where λ 0 is the free space wavelength corresponding to the center resonant frequency of the antenna in the low frequency band).

[0040] The length of the microstrip feed line 2 is 33.2 mm and the width is 2 mm.

[0041] refer to Figure 3 The radiating unit 4 has a rectangular patch 41 with a length of 36 mm and a width of 13 mm, and is connected to the feeding port 3 for feeding via a microstrip feeder line 2. The vertical section length of the U-shaped slot 44 etched thereon is 32 mm, the horizontal section length is 11.5 mm, and the width is 1 mm, and its total length is slightly less than half of the waveguide wavelength corresponding to the center resonant frequency of the mid-frequency band of UAV communication. The vertical section length of the U-shaped branch 42 is 17.5 mm, the horizontal section length is 17.6 mm, and the width is 1.25 mm. The vertical section length of the U-shaped slot 45 etched thereon is 14 mm, the horizontal section length is 17.6 mm, and the width is 0.37 mm, and its length is approximately the physical length of half a wavelength at the high-frequency resonant frequency point. The added bent T-shaped branch 43 has a length of 4 mm and a width of 3 mm at the part connected to the top of the rectangular patch 41. The length of the bent horizontal section is 17.5 mm, and the length of the vertical section is 42 mm and the width is 1 mm. The T-shaped branch 43 is used to provide a new degree of freedom for tuning the low-frequency resonant frequency, and to move the low-frequency resonant frequency point without changing other frequency points, so that the low-frequency resonant frequency point falls at 840 MHz.

[0042] refer to Figure 4 The electric field coupling resonator 5 has a rectangular ring 51 with an outer edge length of 25 mm and a width of 17 mm, and an inner edge length of 20.1 mm and a width of 11.8 mm. Two T-shaped metal strips 52 are placed opposite to each other in the middle of the rectangular ring 51 structure, and the horizontal section length is 9 mm and the width is 1 mm.

[0043] refer to Figure 4 The metal floor 6 is a rectangular structure with a length of 10.2 mm and a width of 19 mm. The rectangular gap 61 etched thereon is located on the floor at a distance of 4.3 mm from the feeding port 3, with a length of 9.2 mm and a width of 1.2 mm.

[0044] refer to Figure 4The rectangular patch 7 is placed at the uppermost end of the lower surface of the dielectric substrate, and its length along the width direction of the dielectric substrate is 15.2 mm, and its length along the length direction of the dielectric substrate is 7 mm.

[0045] Through simulation experiments, the technical effects of the present invention are further explained:

[0046] Simulation conditions and contents: The simulation uses the commercial simulation software HFSS_19.0;

[0047] Simulation 1, the reflection coefficient curve of embodiment 1 of the present invention is simulated, and the result is as follows Figure 5 As shown;

[0048] Simulation 2, the xoy surface radiation pattern at the low frequency center resonant frequency of embodiment 1 of the present invention is simulated, and the result is as follows Figure 6 As shown;

[0049] Simulation 3 simulates the xoy radiation pattern at the center resonant frequency of the mid-frequency band of Example 1 of the present invention, and the results are as follows: Figure 7 As shown;

[0050] Simulation 4 simulates the xoy radiation pattern at the high frequency center resonant frequency of Example 1 of the present invention, and the result is as follows: Figure 8 As shown;

[0051] Simulation results analysis:

[0052] Reference Figure 5 In Example 1, the present invention realizes triple-frequency operation, covering three frequency bands of UAV communication, specifically, the frequency band ranges are: 827MHz-852MHz, 1385MHz-1466MHz and 2383MHz-2741MHz, and the impedance matching characteristics are good.

[0053] Reference Figure 6 In Example 1, the xoy plane omnidirectional radiation characteristics of the present invention at the low-frequency center resonant frequency of 842 MHz are good, the non-circularity is 0.01 dB, and the cross-polarization level is below -40 dB.

[0054] Reference Figure 7 In Example 1, the xoy plane omnidirectional radiation characteristics of the present invention at the center resonant frequency of 1437 MHz in the mid-frequency band are good, the non-circularity is 0.08 dB, and the cross-polarization level is below -25 dB.

[0055] Reference Figure 8 In Example 1, the present invention has good xoy plane omnidirectional radiation characteristics at the high frequency center resonant frequency of 2425MHz, the non-circularity is 0.8dB, and the cross-polarization level is below -25dB.

[0056] The above simulation results show that the present invention realizes triple-frequency operation, covers the three frequency bands of UAV communication, and has good horizontal plane omnidirectional radiation characteristics within the working frequency band. The gain change of the horizontal plane pattern is less than 1dB, and has a low cross-polarization characteristic.

Claims

1. A triple-band conformal omnidirectional antenna, comprising a dielectric substrate, a microstrip feeder, and a radiating unit located on the upper surface of the dielectric substrate; characterized in that: The radiation unit comprises a T-shaped branch, a first rectangular patch etched with a first U-shaped slot, and a U-shaped branch etched with a second U-shaped slot, which are arranged in sequence from top to bottom; the top of the rectangular patch is connected to the vertical section of the T-shaped branch; a feeding port is provided at the bottom of the dielectric substrate; one end of the microstrip feed line is connected to the bottom of the rectangle, and the other end is connected to the feeding port; The opening of the U-shaped branch is upward; The lower surface of the dielectric substrate is provided with a second rectangular patch, an electric field coupling resonator and a metal floor in order from top to bottom; The electric field coupling resonator is located at the back of the first rectangular patch; The metal floor is provided with a rectangular gap perpendicular to the microstrip feeder, and the projection of the metal floor on the upper surface is close to the U-shaped branch; The opening of the first U-shaped gap is upward, the horizontal section of the first U-shaped gap is in close contact with the bottom edge of the first rectangular patch, and the vertical section of the first U-shaped gap is in close contact with the side edge of the corresponding first rectangular patch; The horizontal section of the second U-shaped slot is located on the horizontal section of the U-shaped branch, and the vertical section of the second U-shaped slot is located on the vertical section of the corresponding U-shaped branch; the overlapping part of the microstrip feed line and the U-shaped branch has a hollow forming the second U-shaped slot.

2. The triple-band conformal omnidirectional antenna according to claim 1, characterized in that: The horizontal section of the T-shaped branch is bent downward and has no contact with the first rectangular patch.

3. A triple-band conformal omnidirectional antenna according to claim 1, characterized in that: The electric field coupling resonator comprises a rectangular ring and a T-shaped metal strip located inside the rectangular ring; the vertical sections of the two T-shaped metal strips are respectively connected to the top edge and the bottom edge of the rectangular ring, the horizontal sections of the two T-shaped metal strips are parallel to the top edge of the rectangular ring, and the two horizontal sections are opposite to each other.

Images