A scanning leaky-wave antenna

Abstract

The application discloses a scanning leaky-wave antenna, which comprises a curved waveguide, a waveguide slot and a horn structure arranged in layers, and constitutes a plurality of array units. One end of the curved waveguide is provided with a feeding port. The curved waveguide is composed of a straight waveguide and a slow wave line structure. Matching structures are arranged on both sides of the straight waveguide in a staggered mode. The scanning leaky-wave antenna is composed of a plurality of array units. Because the reflection of the array units is superimposed at the center frequency, the application adds matching structures to each array unit to reduce the reflection of each array unit. In this way, the reflected waves of each array unit are no longer added in phase, and the transmission phase remains unchanged. The impedance matching at the center frequency can be realized without affecting the scanning radiation characteristics. The scanning leaky-wave antenna has the characteristics of center frequency impedance matching, high gain, symmetric large scanning range of ±45°, universality, low cost, simple design structure, low device complexity and suitability for large-scale manufacturing.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, and particularly relates to a scanning leaky-wave antenna. BACKGROUND

[0002] At present, with the requirements of air or ground surveillance systems, radar systems need beam scanning antennas. Commercial ground surveillance radars need a low-cost beam scanning antenna. Although it is the most commonly used beam scanning antenna, the cost of this traditional phased array beam scanning system is very high. In addition to phase scanning, leaky-wave frequency scanning antennas are also commonly used for beam scanning. The true time delay is realized by the transmission line between the two radiating elements, which causes different phase shifts corresponding to different frequencies, thus leading to different beam directions. Since there are no phase shifters and power dividers in the TR module, this beam scanning antenna has a significant cost advantage compared with phased arrays. In recent years, many scholars have conducted a lot of research on leaky-wave scanning antennas, and the main research direction is focused on the slow-wave transmission line that realizes the phase shift between the radiating elements, including composite left / right transmission lines, continuous transverse stubs (CTS), spoof surface plasmon polaritons (SSPPs) lines and other types of slow-wave transmission lines. The above research mainly focuses on how to improve the scanning rate, reduce the size of the transmission line and improve the scanning angle range. No matter which kind of transmission line is used, whether it is a traditional microstrip transmission line or a waveguide transmission line, or a slow-wave transmission line, the frequency scanning antenna still faces a problem, i.e. the impedance matching problem at the center frequency. This problem is common in frequency scanning antennas.

[0003] In view of the above problems, the frequency characteristics and impedance mismatch points are used to realize impedance matching, and the frequency range near these points is selected for work in the design. Specifically, if the impedance mismatch of a certain circuit element at a certain frequency point is very serious, it can be selected to work in the frequency range near the point, which can reduce the reflection loss or ensure better circuit performance. However, the prior art has the following disadvantages:

[0004] (1) The cost of the traditional phased array beam scanning system is high, and it is not suitable for wide range of use.

[0005] (2) The impedance matching problem of the leaky-wave antenna at the center frequency will cause problems such as signal reflection, attenuation, power transmission efficiency reduction, and thus affect the performance of the antenna.

[0006] (3) Using certain mismatch frequency points to realize impedance matching will cause the impedance of the antenna to change unevenly at different frequencies. The gain, radiation characteristics or the accuracy of beam forming may be reduced.

[0007] (4) Using mismatched frequency points as the basis for impedance matching limits the frequency range in which the antenna can effectively operate. This conflicts with the design goal of a frequency scanning antenna that generally needs to cover a wide frequency range.

[0008] (5) The design and optimization of many existing technologies (such as adaptive matching networks, wideband impedance converters, multi-band matching technology) are often complex, requiring in-depth circuit design and analysis. This increases the development cycle and cost. SUMMARY

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present application is to provide a scanning leaky-wave antenna, which is optimized by bending waveguide, waveguide slot, and horn structure, and has a matching structure added to the bending waveguide part, has high gain, center frequency impedance matching, and symmetric large scanning range ±45°, and has the characteristics of simple design structure, low device complexity, suitable for large-scale manufacturing, and low cost.

[0010] In order to achieve the above-mentioned purpose, the technical solution adopted by the present application is:

[0011] A scanning leaky-wave antenna, comprising a bending waveguide 1, a waveguide slot 2, and a horn structure 3 arranged in layers, forming N array units (N>0), the waveguide slot 2 is arranged in layers on the bending waveguide 1 and is mutually adapted with the bending waveguide 1, the horn structure 3 is arranged in layers on the waveguide slot 2 and is mutually adapted with the bending waveguide 1 and the waveguide slot 2.

[0012] One end of the bending waveguide 1 is provided with a feed port 4.

[0013] The bending waveguide 1 comprises N+1 straight waveguides 101 arranged transversely, the far end of the two adjacent transversely arranged straight waveguides 101 is provided with a slow wave line structure 102 with a 180° waveguide bend, each slow wave line structure 102 connects the two straight waveguides 101 adjacent to it on the same side to form an S-shaped groove, and the feed port 4 is in communication with the straight waveguide 101 adjacent to it.

[0014] The opposite sides of the straight waveguides 101 at both ends are respectively staggered with one matching structure 1011, the remaining straight waveguides 101 are staggered with matching structures 1011 on both sides, and the matching structures 1011 on the adjacent sides between adjacent straight waveguides 101 are arranged at the same position, that is, the width of the straight waveguide 101 at the position of the matching structure 1011 is increased.

[0015] The other end of the bending waveguide 1 is provided with a load 5, and the load 5 is in communication with the straight waveguide 101 adjacent to it.

[0016] The waveguide groove 2 between the adjacent straight waveguides 101 is provided with the same number of inclined grooves 201 as the array elements, and the inclined angles of each inclined groove 201 are different, when the inclined angle of the inclined groove 201 is > 40°, the length of the matching structure 1011 is 0.5-2.5mm, when the inclined angle of the inclined groove 201 is ≤ 40°, the length of the matching structure 1011 is 5-7mm, and the inclined angle of each inclined groove 201 makes the voltage comply with the Taylor distribution V s = taylor (sidelobe, nbar, N), wherein, V s is the voltage, sidelobe is the sidelobe level, nbar is the number of equal sidelobes, and N is the number of array elements.

[0017] Further, the length of the matching structure (1011) is selected as the preferred length of the matching structure (1011) with the maximum reflection coefficient phase and the minimum amplitude compared with the reference value when the length of the matching structure (1011) is 0.

[0018] The horn structure 3 includes two symmetrical inclined plates 301 to form a horn shape, and N+1 partitions 302 are arranged between the two inclined plates 301, and the bottom plate 305 is arranged at the narrow end of the two inclined plates 301, and the bottom plate 305 is in the same horizontal plane.

[0019] A plurality of triangular pedestals 303 are arranged between the inclined plate 301 and the bottom plate 305.

[0020] A plurality of first threaded holes 103 are arranged on the side of the curved waveguide 1 adjacent to the waveguide groove 2.

[0021] A plurality of first threaded through holes 202 are arranged on the waveguide groove 2.

[0022] Second threaded holes 304 are arranged on the triangular pedestal 303.

[0023] A plurality of second threaded through holes 306 are arranged on the bottom plate 305.

[0024] The first threaded hole 103, the first threaded through hole 202, the second threaded hole 304 and the second threaded through hole 306 are matched with each other and fixed by screws.

[0025] The curved waveguide 1, the waveguide groove 2 and the horn structure 3 are all made of metal, preferably aluminum.

[0026] Compared with the prior art, the beneficial effects of the present application are:

[0027] 1. The present application generates a small amount of reflection by setting a matching structure 1011 in each array unit. In this way, the amplitude and phase of the reflected wave of each array unit are changed, the reflected wave is no longer added in phase, and the transmission phase between the array units will not change. Impedance matching at the center frequency is achieved without affecting the swept radiation characteristics. That is, high gain, center frequency impedance matching and symmetric large scanning range ± 45° are achieved at the same time.

[0028] 2. The present application realizes modular design by stacking the curved waveguide 1, the waveguide slot 2 and the horn structure 3, and realizes the fixation of the curved waveguide 1, the waveguide slot 2 and the horn structure 3 by screwing the first threaded hole 103, the first threaded through hole 202, the second threaded hole 304 and the second threaded through hole 306, which has the advantages of simple design structure, low device complexity and wide range of manufacturing.

[0029] 3. The curved waveguide 1 of the present application adopts a 180-degree slow wave line structure, which can reduce the loss of the signal in the transmission process and maintain the stability of the signal.

[0030] 4. The horn structure 3 of the present application adopts a horn-shaped structure design, which can realize wideband signal coverage and has the advantages and innovations of high gain and low sidelobe.

[0031] 5. The present application has the advantages and innovations of high efficiency and low cost by opening the same number of inclined grooves 201 on the surface of the waveguide slot 2 between the adjacent straight waveguides 101 and adopting different inclined angles to realize efficient energy coupling between the waveguides.

[0032] 6. The present application has the advantages of increased structural strength, improved processing technology, improved product quality and performance by setting multiple triangular pedestals 303 between the inclined plate 301 and the bottom plate 305.

[0033] 7. The present application has the advantages of high cost-effectiveness and easy processing by using aluminum to make the entire antenna, which further reduces the manufacturing cost.

[0034] In summary, the present application has the characteristics of center frequency impedance matching, high gain, symmetric large scanning range ± 45°, universality, low cost, simple design structure, high strength, low device complexity and wide range of manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the antenna of the present application.

[0036] Figure 2 It is a sectional view of the antenna of the present application.

[0037] Figure 3 It is a schematic diagram of the curved waveguide structure of the present application.

[0038] Figure 4 This is a schematic diagram of the waveguide groove structure of the present invention.

[0039] Figure 5 This is a schematic diagram of the speaker structure of the present invention.

[0040] Figure 6 This is a diagram showing the length distribution of the matching structure in this invention.

[0041] Figure 7 This shows the relationship between the phase of Lm and the reflection coefficient and different slot angles in the simulation experiment of this invention.

[0042] Figure 8 This shows the relationship between the amplitude of Lm and the reflection coefficient and different slot angles in the simulation experiment of this invention.

[0043] Figure 9 This is a comparison of the S-parameters of two antennas with and without matching structures in the simulation experiment of this invention.

[0044] In the figure, 1 is a curved waveguide; 101 is a straight waveguide; 102 is a slow waveline structure; 1011 is a matching structure; 103 is the first threaded hole; 2 is a waveguide groove; 201 is an inclined groove; 202 is the first threaded through hole; 3 is a horn structure; 301 is an inclined plate; 302 is a partition plate; 303 is a triangular base; 304 is the second threaded hole; 305 is the base plate; 306 is the second threaded through hole; 4 is the feed port; and 5 is the load. Detailed Implementation

[0045] The present invention will now be described in detail with reference to the accompanying drawings.

[0046] See Figure 1 , Figure 2 A scanning leaky wave antenna includes a curved waveguide 1, a waveguide groove 2, and a horn structure 3 made of aluminum metal stacked together, forming 48 array elements. The waveguide groove 2 is stacked on the curved waveguide 1 and is adapted to the curved waveguide 1. The horn structure 3 is stacked on the waveguide groove 2 and is adapted to both the curved waveguide 1 and the waveguide groove 2.

[0047] See Figure 1 The curved waveguide 1 has a feed port 4 at one end.

[0048] See Figure 3 The curved waveguide 1 includes 49 transversely staggered straight waveguides 101. At the ends of two adjacent staggered straight waveguides 101 that are far apart, a slow waveline structure 102 with a 180° waveguide bend is provided. Each slow waveline structure 102 connects two adjacent straight waveguides 101 on the same side to form an S-shaped trench. The feed port 4 is connected to its adjacent straight waveguide 101, realizing the frequency sweep and phase shift function.

[0049] Referring to Figure 3 , the two end linear waveguides 101 are staggered with a matching structure 1011 on the opposite side, and the rest of the linear waveguides 101 are staggered with a matching structure 1011 on both sides. The matching structures 1011 on the adjacent sides of the linear waveguides 101 are arranged in the same position, that is, the width of the linear waveguide 101 at the position of the matching structure 1011 is increased, and the size of each matching structure 1011 is different, realizing impedance matching at the center frequency.

[0050] Referring to Figure 3 , the other end of the curved waveguide 1 is provided with a load 5, and the load 5 is in communication with the adjacent linear waveguide 101.

[0051] Referring to Figure 4 , 48 inclined grooves 201 are provided on the surface of the waveguide groove 2 between the adjacent linear waveguides 101 as leaky-wave antenna elements, and the inclination angles of each inclined groove 201 are different, as shown in Table 1. The inclination angle of each inclined groove 201 makes the voltage conform to the Taylor distribution V s =taylor(sidelobe,nbar,N), where V s is the voltage, sidelobe is the sidelobe level, nbar is the number of equal sidelobes, N=48 is the number of array elements, and the relationship between the amplitude and phase of the reflection coefficient and the inclination groove angle is simulated by using matching structures 1011 of different lengths (Lm). The setting of the length of the matching structure 1011 is achieved by repeatedly trying different values through trial and error, observing the simulation results, and gradually approaching the best value range. Finally, the parameter research results are shown in Figure 7 and Figure 8 . When Lm=0, no matching structure 1011 is added. When the length of the matching structure 1011 is small (Lm=0.5-2.5mm) and the inclination angle of the inclined groove 201 is >40 degrees, the influence on the phase and amplitude is large. With the increase of the length of the matching structure 1011 (Lm=5-7mm), the matching structure 1011 has a greater influence on the phase and amplitude of the inclined groove 201 when the inclination angle is ≤40 degrees. According to Figure 7 and Figure 8 , appropriate matching structure 1011 lengths (Lm) are selected for different inclination angles of the inclined groove 201 to realize the radiation of horizontally polarized electromagnetic waves.

[0052] Table 1 Inclination angle of the inclined groove of the antenna

[0053] No. θ No. θ No. θ No. θ 1 57.9 13 47.7 25 33.1 37 19.1 2 57.6 14 46.6 26 31.5 38 21 3 57.2 15 45.5 27 29.7 39 23.2 4 56.5 16 44.4 28 27.8 40 25.5 5 55.9 17 43.3 29 25.8 41 28 6 55 18 42.2 30 23.9 42 30.2 7 54 19 41 31 22 43 32.2 8 52.9 20 39.8 32 20.2 44 33.8 9 51.8 21 38.6 33 18.7 45 34.9 10 50.5 22 37.4 34 17.7 46 35.6 11 49.7 23 36.1 35 17.4 47 35.7 12 48.7 24 34.7 36 17.8 48 35.1

[0054] Referring to Figure 2 , Figure 5The horn structure 3 comprises two symmetrical inclined plates 301 forming a horn shape, N+1 partitions 302 are arranged between the two inclined plates 301, and the two inclined plates 301 are provided with bottom plates 305 at a narrow end, and the bottom plates 305 are in the same horizontal plane. The horn is placed outside the waveguide groove, the isolation of the array unit is improved, the beam width in the elevation plane (h plane) is reduced, and the gain of the antenna array is increased.

[0055] Referring to Figure 2 、 Figure 5 The inclined plate 301 and the bottom plate 305 are provided with 14 triangular pedestals 303, which improve the structural strength; the curved waveguide 1 is provided with 328 first threaded holes 103 on one side adjacent to the waveguide groove 2, the waveguide groove 2 is provided with 328 first threaded through holes 202, the triangular pedestal 303 is provided with second threaded holes 304, and the bottom plate 305 is provided with 328 second threaded through holes 306.

[0056] The first threaded hole 103, the first threaded through hole 202, the second threaded hole 304 and the second threaded through hole 306 are matched with each other and are fixed by screws.

[0057] The first threaded hole 103, the first threaded through hole 202, the second threaded hole 304 and the second threaded through hole 306 on the curved waveguide 1, the waveguide groove 2 and the horn structure 3 are slightly larger in diameter, but their functions are to place screws and connect the three structures.

[0058] Principle: The scanning leaky-wave antenna of the application is composed of 48 radiation units. Electromagnetic waves continuously leak energy through the waveguide groove 2 during propagation along the curved waveguide 1 to form an antenna, and then effectively radiate energy to the free space through the horn structure 3. Because the reflections of the array units will be superimposed at the center frequency, when the number of array units increases, the scanning plane requires high gain and narrow beam width, and the deterioration of the return loss will be more obvious. The application proposes a matching structure 1011. By arranging the matching structure 1011 at each array unit, a small amount of reflection is intentionally created for each array unit. In this way, the phase of the reflected wave of each array unit changes, and the reflected wave no longer adds phase, while the transmission phase between the array units remains unchanged. However, by increasing the matching structure 1011, the transmission phase between the array units will not change. Without affecting the frequency scanning radiation characteristics, impedance matching at the center frequency can be realized.

[0059] Simulation experiment

[0060] To check how the matching structure 1011 affects the amplitude and phase of the reflection coefficient of the array unit, a detailed parametric study is carried out. First, the length (Lm) of the matching structure 1011 is crucial to the phase and amplitude of the reflection coefficient. The width (Wm) of the matching structure 1011 is set to 0.4 mm. Second, the phase and amplitude of the reflection coefficient are also related to the angle of the tilted groove 201. Therefore, the design uses matching structures 1011 with different lengths (Lm) to simulate the relationship between the amplitude and phase of the reflection coefficient and the angle of the tilted groove 201. Since the main purpose of this design is to reduce the return loss at the center frequency, the parametric study is carried out at the center frequency point (16.5 GHz).

[0061] According to Figure 7 and Figure 8 , the appropriate matching length (Lm) can be selected for different angles of the tilted groove 201. The preferred principle is summarized as follows: when Lm = 0, the phase difference of the reflection coefficient is significant, and the amplitude of the reflection coefficient is relatively low. According to this principle, the final selection result is as shown in Figure 6 , from left to right, slots 1-48, for slots 1-10, the corresponding matching structure 1011, Lm = 0.5 mm; for slots 11-20, the corresponding matching structure 1011, Lm = 2.5 mm; for slots 21-29, the corresponding matching structure 1011, Lm = 5 mm; for slots 30-39, the corresponding matching structure 1011, Lm = 7 mm; for slots 40-48, the corresponding matching structure 1011, Lm = 5 mm.

[0062] Referring to Figure 9 , in the figure, prototype antenna 1 is an antenna without a matching structure, and improved anlenna 2 is the antenna of the present embodiment. The comparison of the return loss of prototype antenna 1 and improved anlenna 2 is as shown in Figure 8 . It can be seen that the S(1,1) of improved anlenna 2 is below -13 dB throughout the entire operating frequency band, and is improved by more than 10 dB at the center frequency.

Claims

1. A scanning leaky-wave antenna, characterized by, The curved waveguide (1), the waveguide groove (2) and the horn structure (3) are arranged in layers, and constitute N array units (N>0), the waveguide groove (2) is arranged in layers on the curved waveguide (1) and is matched with the curved waveguide (1), and the horn structure (3) is arranged in layers on the waveguide groove (2) and is matched with the curved waveguide (1) and the waveguide groove (2). One end of the curved waveguide (1) is provided with a feeding port (4). The curved waveguide (1) comprises N+1 straight waveguides (101) arranged transversely staggered, the far ends of two adjacent staggered straight waveguides (101) are provided with slow wave line structures (102) with 180° waveguide bends, each slow wave line structure (102) connects two straight waveguides (101) on the same side to form an S-shaped groove, the feed port (4) is in communication with the adjacent straight waveguide (101), the two end straight waveguides (101) are staggered on the opposite sides respectively with a matching structure (1011), the remaining straight waveguides (101) are staggered on both sides with matching structures (1011), and the matching structures (1011) on the adjacent sides of the adjacent straight waveguides (101) are arranged at the same position, that is, the width of the straight waveguide (101) at the position of the matching structure (1011) is increased, the waveguide groove (2) surface between the adjacent straight waveguides (101) is provided with the same number of inclined grooves (201) as the array elements, the inclined angles of each inclined groove (201) are different, when the inclined angle of the inclined groove (201) is >40°, the length of the matching structure (1011) is 0.5-2.5mm, when the inclined angle of the inclined groove (201) is ≤40°, the length of the matching structure (1011) is 5-7mm, and the inclined angle of each inclined groove (201) makes the voltage comply with Taylor distribution V s =taylor(sidelobe,nbar,N), wherein, V s is the voltage, sidelobe is the sidelobe level, nbar is the number of equal sidelobes, and N is the number of array elements.

2. A scanning leaky-wave antenna according to claim 1, wherein, The other end of the curved waveguide (1) is provided with a load (5) which is communicated with the linear waveguide (101) adjacent to the curved waveguide (1).

3. A scanning leaky-wave antenna according to claim 1, wherein, The length of the matching structure (1011) is selected as the reference length of the reflection coefficient phase and amplitude, and the length of the matching structure (1011) is selected as the reference length of the reflection coefficient phase and amplitude.

4. A scanning leaky-wave antenna according to claim 1, wherein, The horn structure (3) includes two symmetrical inclined plates (301) forming a horn shape, and N+1 partitions (302) are arranged between the two inclined plates (301), and the bottom plate (305) is arranged at the narrow end of the two inclined plates (301), and the bottom plate (305) is arranged on the same horizontal plane.

5. A scanning leaky-wave antenna according to claim 4, wherein, A plurality of triangular pedestals (303) are arranged between the inclined plate (301) and the bottom plate (305).

6. A scanning leaky-wave antenna according to claim 5, wherein, A plurality of first threaded holes (103) are arranged on the side of the curved waveguide (1) adjacent to the waveguide groove (2). A plurality of first threaded holes (202) are arranged on the waveguide groove (2). Second threaded holes (304) are arranged on the triangular pedestal (303). A plurality of second threaded holes (306) are arranged on the bottom plate (305). The first threaded hole (103), the first threaded hole (202), the second threaded hole (304) and the second threaded hole (306) are matched with each other and are fixed by screws.

7. A scanning leaky-wave antenna according to claim 1, wherein The curved waveguide (1), the waveguide groove (2) and the horn structure (3) are all made of metal.

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