A miniaturized UAV-mounted ultra-short wave ionospheric scattering communication antenna

Abstract

The present invention discloses a miniaturized UAV-mounted ultrashort wave ionospheric scattering communication antenna. The antenna is attached to the wings and outer surface of the UAV and conforms to the UAV. It includes a polygonal coupled radiation outer ring and a trapezoidal feed inner ring. The polygonal coupled radiation outer ring includes an upper square ring short-circuit loading line and a lower ring radiator. The ring radiator has a slot in the middle and a slit in the bottom. The trapezoidal feed inner ring is arranged in the middle slot of the ring radiator. It is a hollow trapezoidal ring with a feed point located in the middle of the upper bottom. The antenna disclosed in the present invention is a low-profile planar structure. The antenna is printed on the outer surface of the UAV using conductive metal paint to achieve an integrated conformal design with the UAV and meet the aerodynamic requirements of the UAV flight. The inner and outer double electric small ring structure achieves low-frequency near-field resonance through spatial coupling feeding of the inner and outer rings, realizing a miniaturized design of the antenna.

Description

Technical Field

[0001] The present invention belongs to the field of antenna design, and in particular relates to a miniaturized unmanned aerial vehicle (UAV)-borne ultra-short wave ionospheric scattering communication antenna in this field. Background Art

[0002] Currently, long-range beyond-line-of-sight (BLOS) communication for drones primarily involves shortwave and satellite communications. Shortwave communication relies on ionospheric reflection, but its transmission rate is low and is affected by factors such as daytime, seasonality, and climate. The transmission channel is unstable, sometimes preventing communication from being established at all. Furthermore, its multi-hop propagation mode results in poor confidentiality, making it difficult to meet the data exchange requirements of practical applications. Satellite communication offers wide coverage, long distances, high capacity, and is unrestricted by geographical and climatic conditions. However, it suffers from weak signal strength, high maneuverability, and poor anti-interference capabilities. It is also vulnerable to enemy surveillance and attack, resulting in relatively low security. There is an urgent need to develop a new long-range UAV communication method.

[0003] In the atmosphere approximately 60 to 1000 km above the Earth's surface, the neutral atmosphere is partially ionized by the radiation of solar ultraviolet rays, X-rays, and high-energy particles, forming the ionosphere. This ionosphere scatters, reflects, absorbs, and rotates radio waves propagating through it, creating a crucial component of the Sun-Earth space environment. Influenced by ionospheric disturbances, atmospheric turbulence, high-altitude nuclear explosions, and meteor impacts, the ionosphere can produce an inhomogeneous distribution of charged ion density, forming a turbulent-like inhomogeneous volume with a scattering cross-section of up to 10 for ultrashortwave signals. 8 m 2 , can form an ultra-short wave beyond-horizon information transmission channel to realize directional radiation of signals, which is much higher than the natural ionosphere, and has the characteristics of good confidentiality and strong anti-interference ability.

[0004] Antennas are key components for effectively transmitting or receiving signals in ionospheric scatter communications. Research results show that the typical frequency range for ionospheric scatter communications is 40-50 MHz, with horizontal polarization and air-to-air communication. Considering UAV-mounted applications, antennas require a low-profile conformal design to meet the aerodynamic requirements of the UAV. Furthermore, to account for the UAV's changing mid-air attitude, the antenna must be omnidirectional in the horizontal plane. Conventional UAV-mounted ultra-short wave (VHF) antennas are primarily used for line-of-sight (LOS)-to-ground communications, operate at frequencies above 100 MHz, and utilize vertical polarization, making them unsuitable for ionospheric scatter communication systems. Furthermore, the physical size of VHF antennas is large, and their installation layout must adapt to the operating environment of the carrier aircraft. They must neither affect the aircraft's various performance capabilities nor be affected by the aircraft's flight state, requiring the antenna to exhibit strong environmental adaptability. A miniaturized UAV-mounted ionospheric scatter communication antenna that can address these challenges is urgently needed. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a miniaturized UAV-borne ultra-short wave ionospheric scattering communication antenna.

[0006] The present invention adopts the following technical solutions:

[0007] A miniaturized UAV-mounted ultrashort wave ionospheric scattering communication antenna, the improvement of which lies in: the antenna is attached to the wings and outer surface of the UAV, conforming to the UAV, and comprising a polygonal coupled radiation outer ring and a trapezoidal feed inner ring. The polygonal coupled radiation outer ring comprises an upper square ring short-circuit loading line and a lower annular radiator, with a slot in the middle and a slit in the bottom edge of the annular radiator. The trapezoidal feed inner ring is arranged in the middle slot of the annular radiator, forming a hollow trapezoidal ring with a feeding point located in the middle of the upper bottom.

[0008] Furthermore, the antenna is printed on the outer surface of the drone using conductive metal paint.

[0009] Furthermore, the annular radiator is obtained by cutting a rectangular and trapezoidal groove in the middle of a trapezoidal metal surface and cutting a slit groove at the bottom.

[0010] Furthermore, the trapezoidal feeding inner ring is fed by a transmission line, and the coupling excitation polygonal coupling radiation outer ring is formed.

[0011] The beneficial effects of the present invention are:

[0012] The antenna disclosed in the present invention is a low-profile planar structure. The antenna is printed on the outer surface of the drone using conductive metal paint to achieve an integrated conformal design with the drone, meeting the aerodynamic requirements of the drone flight; the inner and outer double electric small ring structure achieves low-frequency near-field resonance through spatial coupling feeding of the inner and outer rings, realizing the miniaturization design of the antenna; the outer ring square ring short-circuit loading line structure and the slot slot structure are equivalent to inductive and capacitive loading, respectively, and are used to adjust the port input impedance of the antenna to achieve resonance at the operating frequency; the outer ring structure uses the current flow method to adjust the cross-section to compensate for the non-circularity of the horizontal plane of the directional pattern, realizing a horizontal plane omnidirectional design, and meeting the ionospheric scattering communication needs of the drone. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the conformal integration of the antenna disclosed in the present invention and the UAV;

[0014] Figure 2 is a structural diagram of the antenna disclosed in the present invention;

[0015] Figure 3 It is a structural diagram of the polygonal coupled radiation outer ring in the antenna disclosed in the present invention;

[0016] Figure 4It is a structural diagram of the trapezoidal feeding inner loop in the antenna disclosed in the present invention;

[0017] Figure 5 This is an equivalent circuit diagram of the inner and outer loop coupled feeding of the antenna disclosed in the present invention;

[0018] FIG6( a ) is a diagram showing the scanning simulation results of the antenna D1 parameters disclosed in the present invention;

[0019] FIG6( b ) is a diagram showing the scanning simulation results of the antenna D2 parameters disclosed in the present invention;

[0020] FIG6( c ) is a diagram showing the scanning simulation results of the antenna L0 parameters disclosed in the present invention;

[0021] FIG6( d ) is a diagram showing the scanning simulation results of the antenna H0 parameters disclosed in the present invention;

[0022] Figure 7 This is a comparison diagram of the simulated and measured standing wave ratio curves of the antenna disclosed in the present invention;

[0023] FIG8( a ) is a horizontal plane radiation pattern of the antenna disclosed in the present invention at a typical frequency point and an elevation angle of 0°;

[0024] FIG8( b ) is a horizontal plane pattern of the antenna disclosed in the present invention at an elevation angle of 5° at a typical frequency;

[0025] FIG8( c ) is a horizontal plane pattern of the antenna disclosed in the present invention at a typical frequency point and an elevation angle of 15°;

[0026] FIG8( d ) is a horizontal plane radiation pattern of the antenna disclosed in the present invention at an elevation angle of 25° at a typical frequency.

[0027] Reference numerals: 1—polygonal coupling radiation outer ring, 11—square ring short-circuit loading line, 12—ring radiator, 13—slot, 14—slot, 2—trapezoidal feeding inner ring, 21—feeding point. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] The operating frequency of the ionospheric scattering communication antenna is low, and its physical size is relatively large. However, the available physical space of the UAV is small. At the same time, to meet the aerodynamic requirements, the antenna is designed with a low profile. Therefore, the design ideas of the antenna of the present invention are as follows: miniaturization, lightweight, low-profile conformal design; the antenna is installed above the UAV fuselage to avoid the UAV body blocking the air communication link; the antenna and platform are integrated into the design, taking into account the impact of the platform on the antenna performance; the antenna horizontal plane radiation pattern is omnidirectional to ensure communication continuity when the UAV posture changes.

[0030] The present invention discloses a miniaturized UAV-mounted ultra-short wave ionospheric scattering communication antenna, such as Figure 1 As shown, the antenna is attached to the wings and outer surface of the drone, and is conformally integrated with the drone. The antenna is printed on the outer surface of the drone using conductive metal paint, and is formed into one piece with the fuselage, which facilitates engineering implementation and eliminates the impact on the aerodynamic performance of the drone in high-speed flight conditions.

[0031] like Figure 2 As shown in FIG4 , the antenna comprises a polygonal coupled radiating outer ring 1 and a trapezoidal feed inner ring 2. The polygonal coupled radiating outer ring comprises an upper square ring short-circuit loading line 11 and a lower ring radiator 12. The square ring short-circuit loading line is used to provide equivalent inductive loading for the polygonal coupled radiating outer ring. A slot 13 is provided in the middle of the ring radiator, and a slot 14 is provided at the bottom edge. The slot is used to provide equivalent capacitive loading for the polygonal coupled radiating outer ring. The structural dimensions of the two parts are used to adjust the port input impedance of the antenna. The trapezoidal feed inner ring is arranged within the central slot of the ring radiator. It is a hollow trapezoidal ring with a feed point 21 located in the middle of the upper base.

[0032] The ring radiator is constructed from a trapezoidal metal surface with a rectangular and trapezoidal slot in the center and a slot at the bottom. By controlling the dimensions of the rectangular and trapezoidal slots, the antenna's cross-section in the direction of current flow is increased, compensating for the amplitude attenuation caused by radiation during current flow. This creates a current distribution similar to that of a small electric loop antenna, compensating for horizontal non-circularity in the pattern and achieving omnidirectional horizontal radiation, meeting the requirements of drones for omnidirectional horizontal communication.

[0033] The inner and outer rings of the antenna are placed close to each other, and the input impedance of the antenna is adjusted by the inductive coupling of the inner and outer rings (the equivalent circuit diagram is as follows Figure 5 As shown, where M is the mutual coupling inductance of the inner and outer rings, L 外 , L 内 is the equivalent inductance of the outer and inner rings themselves, Rr is the equivalent radiation resistance of the outer ring, and C is the equivalent capacitance of the slot of the outer ring), realizing low-frequency near-field resonance, thereby improving radiation efficiency. Through this spatial electromagnetic coupling feeding method, the miniaturization design of the antenna is realized.

[0034] When the antenna operates at its resonant frequency, the inner trapezoidal feed loop is fed by the transmission line, coupling and exciting the outer polygonal coupled radiating loop. The antenna's current distribution is primarily concentrated in the outer polygonal coupled radiating loop, while the current in the inner trapezoidal feed loop is weaker, receiving energy from the outer polygonal coupled radiating loop.

[0035] The distance D1 between the inner and outer rings of the antenna, the width D2 of the antenna slot, the width L0 of the outer ring of the antenna, and the height H0 of the outer ring of the antenna are analyzed. D1 and D2 mainly affect the resonant frequency and bandwidth of the antenna, while L0 and H0 mainly affect the resonant frequency and horizontal plane non-circularity of the antenna.

[0036] As the distance D1 between the inner and outer rings of the antenna decreases, as shown in Figure 6(a), the coupling between the inner and outer rings is enhanced, the resonant frequency of the antenna moves toward high frequency, and the bandwidth is also widened. At the same time, the reflection of the resonant frequency is reduced, and the depth of the voltage standing wave ratio is also optimized. As the slot width D2 decreases, as shown in Figure 6(b), the resonant frequency of the antenna moves toward high frequency, and the bandwidth is also widened to a certain extent.

[0037] The width and height of the antenna's outer ring are also crucial parameters, affecting the antenna's resonant frequency, VSWR depth, and out-of-roundness. As the outer ring width L0 increases, as shown in Figure 6(c), the resonant frequency gradually shifts toward lower frequencies, and the antenna's out-of-roundness worsens. As the outer ring height H0 increases, as shown in Figure 6(d), the resonant frequency also gradually shifts toward lower frequencies, and the horizontal out-of-roundness worsens. Therefore, an optimization algorithm is necessary to select appropriate parameters.

[0038] In Example 1, the physical dimensions of the antenna are 1902 mm × 945 mm. Specific parameters are shown in the table below:

[0039] Antenna structural parameter values ​​(mm)

[0040] parameter H0 H1 H2 H3 L0 L1 L2 L3 L4 L5 L6 D1 D2 Numerical 945 345 378 354 1902 153 214 627 423 237 954 7.4 10.6

[0041] The cross-section height is about 1mm, and the operating frequency band is 41.8MHz~43.8MHz. It is a typical electrically small antenna with a size of about 0.27×0.13 wavelengths (relative to the center frequency of 42MHz). Compared with the conventional size of 0.5 wavelength, it has achieved a miniaturized design. Simulations were performed and the installed antenna was tested using the Agilent Vector Network Analyzer 5061A. The measured and simulated antenna standing wave ratio are compared. Figure 7 As shown in the figure, the antenna has a VSWR of ≤2.5 in the frequency band of 40.3MHz to 42.7MHz, and an absolute bandwidth of 2.4MHz. The measured and simulated results are in good agreement, with the measured results slightly shifting toward higher frequencies. This is due to the influence of the actual test ground and test environment, as well as test errors.

[0042] Figures 8(a)-8(d) show the simulation results of the horizontal plane radiation pattern at the typical frequency point 41.8MHz at 0°, 5°, 15°, and 25° elevation angles. The gain in the horizontal plane is -1dBi~1dBi, which has good horizontal omnidirectional characteristics and can meet the elevation angle requirements of communications at different distances.

Claims

1. A miniaturized UAV-mounted ultra-short wave ionospheric scattering communication antenna, characterized by: The antenna is attached to the wings and outer surface of the drone, conforming to the drone. It includes a polygonal coupled radiation outer ring and a hexagonal feeding inner ring. The polygonal coupled radiation outer ring includes a square ring short-circuit loading line at the top and a ring radiator at the bottom. The ring radiator has a slot in the middle and a slit at the bottom. The hexagonal feeding inner ring is arranged in the middle slot of the above-mentioned ring radiator. It is a hollow hexagonal ring with the feeding point placed in the middle of the upper bottom. The annular radiator is obtained by opening a rectangular and trapezoidal groove in the middle of a trapezoidal metal surface and a slit groove at the bottom.

2. The miniaturized UAV-mounted ultra-short wave ionospheric scattering communication antenna according to claim 1, characterized in that: The antenna is printed on the outer surface of the drone using conductive metallic paint.

3. The miniaturized UAV-mounted ultra-short wave ionospheric scattering communication antenna according to claim 1, characterized in that: The hexagonal feeding inner ring is fed by the transmission line, and the coupling excitation polygonal coupling radiation outer ring.

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