Scanning leaky-wave antenna

Abstract

The invention discloses a scanning leaky-wave antenna, which comprises a bent waveguide, a waveguide slot and a horn structure which are stacked to form a plurality of array units, one end of the bent waveguide is provided with a feed port, the bent waveguide is composed of a linear waveguide and a slow wave line structure, and matching structures are arranged on two sides of the linear waveguide in a staggered manner; the scanning leaky-wave antenna is composed of a plurality of array units, and reflection of the array units can be superposed at the center frequency, so that a matching structure is added to each array unit, reflection of each array unit is reduced, reflected waves of each array unit are not subjected to phase adding any more, the transmission phase is kept unchanged, and the scanning leaky-wave antenna has the advantages of being simple in structure and convenient to use. Impedance matching at the center frequency can be realized under the condition that the sweep frequency radiation characteristic is not influenced. The antenna has the characteristics of center frequency impedance matching, high gain, symmetrical large scanning range of + / -45 degrees, universality, low cost, simple design structure, low device complexity and suitability for large-range manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas, and in particular to a scanning leaky-wave antenna. Background Art

[0002] At present, with the requirements of air or ground surveillance systems, radar systems require beam scanning antennas. Commercial ground surveillance radars require 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 real time delay is achieved through the transmission line between the two radiating elements, which causes different phase shifts, corresponding to different frequencies, resulting in different beam directions. Since there is no phase shifter and power divider in the TR module, this beam scanning antenna has a significant cost advantage over the phased array. In recent years, many scholars have conducted a lot of research on leaky wave scanning antennas, and the main research direction is focused on slow-wave transmission lines that realize phase shifts between radiating elements, including composite left / right transmission lines, continuous transverse short lines (CTS), spoof surface plasmon polaritons (SSPPs) lines, and other types of slow-wave transmission lines. The above research mainly focuses on how to increase the scanning rate, reduce the size of the transmission line, and increase the scanning angle range. No matter which transmission line is used, whether it is a traditional microstrip transmission line, a waveguide transmission line, or a slow-wave transmission line, the frequency scanning antenna still faces a problem, that is, the impedance matching problem at the center frequency. This problem is very common in frequency scanning antennas.

[0003] To solve the above problems, impedance matching is achieved by using frequency characteristics and impedance mismatch points, and working in the frequency range near these points is selected in the design. Specifically, if the impedance mismatch of a circuit element at a specific frequency point is very serious, it can be selected to work in the frequency range near this point, which can reduce reflection loss or ensure better circuit performance. However, the existing technology has the following disadvantages:

[0004] (1) Traditional phased array beam scanning systems are expensive and not suitable for large-scale promotion and use.

[0005] (2) The impedance matching problem of the leaky wave antenna at the center frequency will lead to problems such as signal reflection, attenuation, and reduced power transmission efficiency, which will in turn affect the performance of the antenna.

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

[0007] (4) Using the mismatch frequency point as the basis for impedance matching limits the frequency range in which the antenna can work effectively. This conflicts with the design goal of frequency scanning antennas, which usually need to cover a wide frequency range.

[0008] (5) The design and optimization of many existing technologies (such as adaptive matching networks, broadband impedance converters, and multi-band matching technologies) are often complex and require in-depth circuit design and analysis, which increases development cycles and costs. Summary of the invention

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

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A scanning leaky-wave antenna comprises a stacked curved waveguide 1, a waveguide slot 2 and a horn structure 3, forming N array units (N>0), wherein the waveguide slot 2 is stacked on the curved waveguide 1 and is adapted to the curved waveguide 1, and the horn structure 3 is stacked on the waveguide slot 2 and is adapted to both the curved waveguide 1 and the waveguide slot 2.

[0012] A feeding port 4 is provided at one end of the curved waveguide 1 .

[0013] The curved waveguide 1 includes N+1 laterally staggered straight waveguides 101, and a slow-waveline structure 102 with a 180° waveguide elbow is provided at one end of two adjacent staggered straight waveguides 101 that are farther apart. Each slow-waveline structure 102 connects two adjacent straight waveguides 101 on the same side to form an S-shaped groove, and the feeding port 4 is connected to the adjacent straight waveguide 101.

[0014] The opposite sides of the linear waveguides 101 at the two ends are respectively staggered with a matching structure 1011, and the matching structures 1011 are staggered on both sides of the remaining linear waveguides 101, and the positions of the matching structures 1011 adjacent to the sides of adjacent linear waveguides 101 are the same, that is, the width of the linear waveguide 101 at the position where the matching structure 1011 is located is increased.

[0015] A load 5 is disposed at the other end of the curved waveguide 1 , and the load 5 is connected to the adjacent straight waveguide 101 .

[0016] The same number of inclined grooves 201 as the array unit is provided on the surface of the waveguide groove 2 between the adjacent linear waveguides 101, and the inclination angle of each inclined groove 201 is different. When the inclination angle of the inclined groove 201 is greater than 40°, the length of the matching structure 1011 is 0.5 to 2.5 mm, and when the inclination angle of the inclined groove 201 is less than or equal to 40°, the length of the matching structure 1011 is 5 to 7 mm. 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, and N is the number of array elements.

[0017] Furthermore, taking the reflection coefficient phase and amplitude when the length of the matching structure (1011) is 0 as a reference, the length with the largest reflection coefficient phase and the lowest amplitude compared to the reference value is selected as the preferred length of the matching structure (1011).

[0018] The speaker structure 3 includes two symmetrically arranged inclined plates 301 to form a speaker shape, N+1 partitions 302 are arranged between the two inclined plates 301, and bottom plates 305 are arranged at the narrower ends of the two inclined plates 301, and the bottom plates 305 are in the same horizontal plane.

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

[0020] A plurality of first threaded holes 103 are disposed on a surface of the curved waveguide 1 adjacent to the waveguide slot 2 .

[0021] The waveguide slot 2 is provided with a plurality of first threaded through holes 202 .

[0022] The triangular base 303 is provided with a second threaded hole 304 .

[0023] The bottom plate 305 is provided with a plurality of second threaded through holes 306 .

[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 adapted to each other and fixed by screws.

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

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

[0027] 1. The present invention 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 phase-added, and the transmission phase between array units does not change. Impedance matching at the center frequency is achieved without affecting the swept frequency radiation characteristics. That is, high gain, center frequency impedance matching and symmetrical large scanning range of ±45° are achieved at the same time.

[0028] 2. The present invention realizes modular design by stacking a curved waveguide 1, a waveguide slot 2 and a speaker structure 3 to form N array units, and threadingly connects the first threaded hole 103, the first threaded through hole 202, the second threaded hole 304 and the second threaded through hole 306 by screws to fix the curved waveguide 1, the waveguide slot 2 and the speaker structure 3. The design structure is simple, the device complexity is low, and it is suitable for large-scale manufacturing.

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

[0030] 4. The speaker structure 3 of the present invention adopts a speaker-shaped structure design, which can achieve wide-band signal coverage and has the advantages and innovations of high gain and low side lobes.

[0031] 5. The present invention provides inclined grooves 201 with the same number as the array units on the surface of the waveguide groove 2 between the adjacent straight waveguides 101, and adopts different inclination angles to achieve efficient energy coupling between waveguides, which has the advantages and innovations of high efficiency and low cost.

[0032] 6. The present invention provides a plurality of triangular bases 303 between the inclined plate 301 and the bottom plate 305, which can increase the structural strength, improve the processing technology, and enhance the product quality and performance.

[0033] 7. The present invention uses metal aluminum to make the entire antenna, which is cost-effective and easy to process, further reducing the manufacturing cost.

[0034] In summary, the present invention has the characteristics of center frequency impedance matching, high gain, symmetrical large scanning range of ±45°, universality, low cost, simple design structure, high strength, low device complexity, and suitability for large-scale manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0036] Figure 2 It is a cross-sectional view of the antenna of the present invention.

[0037] Figure 3 Schematic diagram of the curved waveguide structure of the present invention.

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

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

[0040] Figure 6 It is the matching structure length distribution diagram of the present invention.

[0041] Figure 7 Graph 1 is the relationship between the phase of Lm and the reflection coefficient with different slot angles in the simulation experiment of the present invention.

[0042] Figure 8 Graph 1 is the relationship between Lm and the amplitude of the reflection coefficient with different slot angles in the simulation experiment of the present invention.

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

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

[0045] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0046] See also Figure 1 , Figure 2 A scanning leaky wave antenna comprises a stacked curved waveguide 1, a waveguide slot 2 and a horn structure 3 made of metal aluminum, forming 48 array units. The waveguide slot 2 is stacked on the curved waveguide 1 and matched with the curved waveguide 1. The horn structure 3 is stacked on the waveguide slot 2 and matched with both the curved waveguide 1 and the waveguide slot 2.

[0047] See also Figure 1 A feeding port 4 is provided at one end of the curved waveguide 1.

[0048] See also Figure 3 The curved waveguide 1 includes 49 laterally staggered linear waveguides 101, and a slow-wave line structure 102 with a 180° waveguide elbow is arranged at the far end of two adjacent staggered linear waveguides 101. Each slow-wave line structure 102 connects two adjacent linear waveguides 101 on the same side to form an S-shaped groove. The feeding port 4 is connected to the adjacent linear waveguide 101 to realize the swept frequency phase shift function.

[0049] See also Figure 3 The opposite sides of the linear waveguides 101 at the two ends are respectively staggered with a matching structure 1011, and the matching structures 1011 are staggered on both sides of the remaining linear waveguides 101, and the positions of the matching structures 1011 adjacent to the sides of adjacent linear waveguides 101 are the same, that is, the width of the linear waveguide 101 at the position where the matching structure 1011 is located is increased, and the size of each matching structure 1011 is different, so as to achieve impedance matching at the center frequency.

[0050] See also Figure 3 A load 5 is provided at the other end of the curved waveguide 1, and the load 5 is connected to the adjacent straight waveguide 101.

[0051] See also Figure 4 , 48 inclined slots 201 are provided on the surface of the waveguide slot 2 between the adjacent straight waveguides 101 as leaky wave antenna elements, and the inclination angle of each inclined slot 201 is different, as shown in Table 1, and the inclination angle of each inclined slot 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 tilted slot angle is simulated by using matching structures 1011 (Lm) of different lengths. Among them, the length of the matching structure 1011 is set by repeatedly trying different values ​​through trial and error, observing the simulation results, and gradually approaching the optimal value range. Finally, the parameter study results are shown in Figure 7 and Figure 8 As shown. When Lm = 0, no matching structure 1011 is added. When the length of the matching structure 1011 is small (Lm = 0.5-2.5 mm) and the inclination angle of the inclined groove 201 is greater than 40 degrees, the influence on the phase and amplitude is greater. As the length of the matching structure 1011 (Lm = 5-7 mm) increases, the matching structure 1011 has a greater influence on the phase and amplitude when the inclination angle of the inclined groove 201 is ≤ 40 degrees. According to Figure 7 and Figure 8 According to different inclination angles of the inclined slots 201, a suitable length (Lm) of the matching structure 1011 is selected to achieve the radiation of horizontally polarized electromagnetic waves.

[0052] Table 1 Slot angles of antennas

[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] See also Figure 2 , Figure 5The horn structure 3 includes two symmetrically arranged inclined plates 301 to form a horn shape, N+1 partitions 302 are arranged between the two inclined plates 301, and a bottom plate 305 is arranged at the narrower end of the two inclined plates 301, and the bottom plates 305 are on the same horizontal plane. Placing the horn outside the waveguide slot improves the isolation of the array unit, reduces the beam width on the elevation plane (h plane), and increases the gain of the antenna array.

[0055] See also Figure 2 , Figure 5 , 14 triangular bases 303 are arranged between the inclined plate 301 and the bottom plate 305 to improve the structural strength; 328 first threaded holes 103 are arranged on the adjacent side of the curved waveguide 1 and the waveguide groove 2, 328 first threaded through holes 202 are arranged on the waveguide groove 2, second threaded holes 304 are opened on the triangular base 303, and 328 second threaded through holes 306 are opened on the bottom plate 305.

[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 adapted to each other and fixed by screws.

[0057] The outermost threaded holes of the first threaded hole 103, the first threaded through hole 202 and the second threaded hole 304 provided on the curved waveguide 1, the waveguide slot 2 and the speaker structure 3 have slightly larger diameters, but they all function to place screws to connect the three structures.

[0058] Principle description: The scanning leaky wave antenna of the present invention is composed of 48 radiating units. The electromagnetic wave continuously leaks energy through the waveguide slot 2 during propagation along the curved waveguide 1 to form an antenna, and then effectively radiates the energy into 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 and the scanning plane requires high gain and narrow beam width, the deterioration of the return loss will be more obvious. The present invention proposes a matching structure 1011. By setting a matching structure 1011 in 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, the reflected wave is no longer added, and the transmission phase between the array units remains unchanged. However, by adding the matching structure 1011, the transmission phase between the array units will not change. Impedance matching at the center frequency can be achieved without affecting the swept frequency radiation characteristics.

[0059] Simulation experiment

[0060] In order to examine how the matching structure 1011 affects the amplitude and phase of the reflection coefficient of the array unit, a detailed parameter study was conducted. First, the length (Lm) of the matching structure 1011 has a crucial effect on the phase and amplitude of the reflection coefficient. The width (Wm) of the matching structure 1011 is set to 0.4mm. Secondly, the phase and amplitude of the reflection coefficient are also related to the inclination angle of the inclined groove 201. Therefore, this 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 inclined groove 201. Since the main purpose of this design is to reduce the return loss of the center frequency, a parameter study is conducted at the center frequency point (16.5GHz).

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

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

Claims

1. A scanning leaky wave antenna, characterized in that: The invention comprises a stacked curved waveguide (1), a waveguide slot (2) and a speaker structure (3), which form N array units (N>0), wherein the waveguide slot (2) is stacked on the curved waveguide (1) and is mutually compatible with the curved waveguide (1), and the speaker structure (3) is stacked on the waveguide slot (2) and is mutually compatible with both the curved waveguide (1) and the waveguide slot (2); A feeding port (4) is provided at one end of the curved waveguide (1).

2. A scanning leaky wave antenna according to claim 1, characterized in that: The curved waveguide (1) comprises N+1 linear waveguides (101) arranged in a transverse staggered manner, a slow waveline structure (102) having a 180° waveguide elbow is arranged at one end of two adjacent linear waveguides (101) arranged in a staggered manner and which is farther away from each other, each slow waveline structure (102) connects two adjacent linear waveguides (101) on the same side to form an S-shaped groove, and the feeding port (4) is connected to the adjacent linear waveguide (101).

3. A scanning leaky wave antenna according to claim 2, characterized in that: The opposite sides of the linear waveguides (101) at the two ends are respectively staggered with a matching structure (1011), and the two sides of the remaining linear waveguides (101) are staggered with matching structures (1011), and the matching structures (1011) on the adjacent sides between adjacent linear waveguides (101) are arranged at the same position, that is, the width of the linear waveguide (101) at the position where the matching structure (1011) is located is increased.

4. A scanning leaky wave antenna according to claim 2, characterized in that: A load (5) is provided at the other end of the curved waveguide (1), and the load (5) is connected to the adjacent straight waveguide (101).

5. A scanning leaky wave antenna according to claim 3, characterized in that: The surface of the waveguide groove (2) between the adjacent straight waveguides (101) is provided with inclined grooves (201) of the same number as the array unit, each inclined groove (201) has a different inclination angle, when the inclination angle of the inclined groove (201) is greater than 40°, the length of the matching structure (1011) is 0.5 to 2.5 mm, when the inclination angle of the inclined groove (201) is less than 40°, the length of the matching structure (1011) is 5 to 7 mm, and 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, and N is the number of array elements.

6. A scanning leaky wave antenna according to claim 5, characterized in that: Taking the reflection coefficient phase and amplitude when the length of the matching structure (1011) is 0 as a reference, the length with the largest reflection coefficient phase and the lowest amplitude compared to the reference value is selected as the preferred length of the matching structure (1011).

7. A scanning leaky wave antenna according to claim 1, characterized in that: The horn structure (3) comprises two symmetrically arranged inclined plates (301) forming a horn shape, N+1 partitions (302) are arranged between the two inclined plates (301), and bottom plates (305) are arranged at the narrower ends of the two inclined plates (301), and the bottom plates (305) are on the same horizontal plane.

8. A scanning leaky wave antenna according to claim 7, characterized in that: A plurality of triangular bases (303) are arranged between the inclined plate (301) and the bottom plate (305).

9. A scanning leaky wave antenna according to claim 8, characterized in that: A plurality of first threaded holes (103) are provided on a surface of the curved waveguide (1) adjacent to the waveguide slot (2); The waveguide groove (2) is provided with a plurality of first threaded through holes (202); The triangular base (303) is provided with a second threaded hole (304); The bottom plate (305) is provided with a plurality of second threaded through holes (306); The first threaded hole (103), the first threaded through hole (202), the second threaded hole (304) and the second threaded through hole (306) are adapted to each other and fixed by screws.

10. The scanning leaky wave antenna according to claim 1, characterized in that: The curved waveguide (1), waveguide slot (2) and horn structure (3) are all made of metal, preferably aluminum.

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