A variable beam width wide beam planar lens antenna

Abstract

The present invention discloses a variable beam width wide beam planar lens antenna, comprising a horn feed antenna and a planar lens, wherein the planar lens realizes the refraction of electromagnetic waves by setting a gradient phase, wherein an additional gradient phase delta is added to the antenna H plane on the basis of compensating for the spatial phase caused by the optical path difference n The plane lens is composed of 51×51 phase shift units. The phase shift unit adopts two layers of dielectric and is copper-clad on the upper, middle and lower surfaces. The thickness is very thin. In order to simplify the design and reduce the processing cost, the present invention selects 8 types of phase shift units to cover the 0-360° phase shift range. By introducing the beam broadening phase, the focusing performance of the lens on the two main planes is different to control the beam width. The required phase shift at each position is obtained according to the calculation formula of each point of the plane lens, and the phase shift units are arranged according to the specified phase distribution diagram to obtain a plane lens antenna with a specified beam width.

Description

Technical Field

[0001] The invention relates to the technical field of antennas in passive devices, in particular to a variable beam width wide beam planar lens antenna. Background Art

[0002] In recent years, intelligent driving modes such as assisted driving and autonomous driving have brought opportunities for the booming development of millimeter-wave automotive radar. Compared with traditional sensors, ultrasonic radars and infrared sensors, 77Ghz millimeter-wave automotive radar systems perform well in complex weather conditions such as night, heavy rain and fog. Considering the limitations of vehicle space, automotive radar antennas are required to be light in weight, low in profile and low in cost. However, millimeter-wave radars face problems such as large size, small size and poor performance. Planar lens arrays composed of a series of periodic subwavelength units have attracted great attention from researchers due to their high flexibility in beamforming and low cost. Compared with traditional phased arrays and dielectric lenses, planar lens antennas have many advantages such as low profile, low cost, light weight and simple manufacturing process, and have been widely used in many fields such as automotive radar and 5G communications.

[0003] Planar lens units are usually made by etching metal conductors on multi-layer dielectrics. In order to achieve a larger phase shift range, the number of dielectric layers is usually relatively large and the thickness is thicker, but compared with cylindrical or spherical dielectric lenses, their planar structure is often small in size and light in weight. Compared with phased array antennas, lens antennas avoid the design of complex feeding networks, are easier to process, and are often less expensive. Planar lens antennas are flexible in design and have strong scalability. The design focus is mainly on designing phase shift units with high transmission performance and efficient phase distribution methods. By arranging a series of high-performance units according to a given phase distribution method, different beam shapes can be obtained to achieve given design indicators.

[0004] At present, the design of variable width wide beam antennas mainly has the following difficulties: if the phased array method is used, it is inevitable to design a complex feeding network. At 77GHz, the antenna size is often very small, and the feeding network design and processing is particularly difficult and costly; if the dielectric lens method is used, the dielectric lens is usually a three-dimensional structure, which occupies a large space and is difficult to integrate. The use of a planar lens antenna can solve the above problems well. The phase shift range of the phase shift unit based on metamaterials is usually narrow. In order to increase the phase shift range, it is often necessary to increase its profile height, which will make the lens bulky. Therefore, how to design a set of low-profile, small-size high-performance phase shift units to cover a 360° phase shift range, and design a set of unit arrangements to achieve high gain and wide beam characteristics of the antenna, has become a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a planar lens antenna with simple structure, controllable beam width, high antenna gain and small array size.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0007] The present invention discloses a variable beam width wide beam planar lens antenna, comprising a horn feed antenna and a planar lens composed of a plurality of phase shift units. The planar lens realizes the refraction of electromagnetic waves by setting a gradient phase, wherein an additional gradient phase delta is added to the antenna H plane on the basis of compensating for the spatial phase caused by the optical path difference. n , gradient phase δ n As shown below:

[0008]

[0009] Where: n is the number of the current unit from left to right on the H plane, N is the total number of units in this direction, α is the gradient coefficient, and the beam width is controlled by changing the gradient coefficient α. When α increases, the beam width is widened accordingly.

[0010] The gain will decrease.

[0011] A further improvement of the present invention is that the phase shift unit is composed of a three-layer metal resonance structure with double resonance characteristics and a double-layer medium, and the three-layer metal resonance structure is etched at intervals on the surface of the double-layer medium.

[0012] A further improvement of the present invention is that the double-layer medium comprises an upper-layer medium and a lower-layer medium made of metamaterials.

[0013] A further improvement of the present invention is that the three-layer metal resonant structure is respectively an upper patch arranged on the outer surface of the upper medium, a middle patch arranged between the lower medium and the lower medium, and a lower patch arranged on the outer surface of the lower medium.

[0014] A further improvement of the present invention is that the upper patch, the middle patch and the lower patch are all made of copper, the upper patch and the lower patch are cross-shaped with the same size, and the middle patch adopts a circular ring nested circular structure.

[0015] A further improvement of the present invention is that the sizes of the upper patch, the middle patch and the lower patch of the phase shift unit are adjusted to obtain 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° phase shift units.

[0016] A further improvement of the present invention is that the number of phase shift units of the entire array of the plane lens is 51×51, the thickness is 0.5 mm, and the length and width of each phase shift unit are both 2 mm.

[0017] The beneficial effects of the present invention are: compared with the prior art, the present invention has the following obvious characteristics and advantages:

[0018] 1. The antenna structure is simple. Compared with other wide beam antennas, the planar lens antenna in the present invention has a simple manufacturing process, does not require a feeding network, and uses a horn antenna feed source to feed the array. Only 8 phase shift units are used to cover a 360° phase shift range, and the array is thin and light, making it easy to integrate and manufacture.

[0019] 2. The beam width is controllable. By changing the α value in the beam broadening phase, the beam width can be controlled on the H plane, while the beam width on the E plane remains basically unchanged, thus achieving a wide beam effect.

[0020] 3. The antenna gain is high. The maximum gain of the planar lens antenna in the present invention can reach 30.5dB, which is 15dB higher than that of the feed antenna. Although the gain decreases as the beam width widens, there is still a significant gain improvement for the feed antenna.

[0021] 4. The array size is small and thin. The overall front size is 102×102×0.5mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the planar lens antenna of the present invention.

[0023] Figure 2 This is a diagram of the distribution structure of the plane lens unit.

[0024] Figure 3 Schematic diagram of the structure of the plane lens phase shift unit.

[0025] Figure 4 It is the front view of the planar lens phase shift unit.

[0026] Figure 5 It is a side view of the planar lens phase shift unit.

[0027] Figure 6 Graph showing the relationship between the transmission coefficient and phase shift capability of eight different planar lens phase shift units.

[0028] Figure 7 Return loss results for the feed horn antenna before and after the lens is loaded.

[0029] Figure 8 The E-plane and H-plane radiation patterns of the feed horn antenna before loading the lens.

[0030] Fig. 9 The E-plane and H-plane radiation patterns of the feed horn antenna after loading the lens.

[0031] Fig.10is the radiation pattern of the antenna on the E plane when α is different.

[0032] Among them, A-feed horn antenna, B-lens unit array, 1-upper patch, 2-upper medium, 3-middle patch, 4-lower medium, 5-lower patch. DETAILED DESCRIPTION

[0033] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the protection scope of the present invention. However, these embodiments are illustrative and are only used to specifically describe the present invention, and should not be understood as limiting the present invention.

[0034] like Figure 1-10 As shown, the variable beam width wide beam planar lens antenna of the present invention is a planar lens antenna based on metamaterials, which has the characteristics of small size, light weight, easy integration and simple manufacturing. It includes a horn feed antenna and a planar lens composed of several phase shift units, and the planar lens refracts electromagnetic waves by setting a gradient phase, thereby realizing the change of beam width and peak gain.

[0035] Metamaterials are artificial synthetic materials with abnormal electromagnetic properties that natural materials do not have. Planar lens units made of metamaterials can achieve changes in the phase of electromagnetic waves, thereby changing the shape of the beam. Metamaterials are manufactured by etching metal structures on the surface of the medium. The ability to change the phase can be changed by changing parameters such as the shape and size of the metal conductor. In order to reduce the difficulty of manufacturing, the 360° phase shift range is often quantified to varying degrees, while still maintaining the good radiation performance of the planar lens. The metamaterial can be Rogers RT6002, that is, both the upper medium and the lower medium are Rogers RT6002 medium.

[0036] The feed source adopts the form of ordinary horn antenna. Through simulation, its peak gain is 15.5dB, H-plane beam width is 34.4°, and E-plane beam width is 29.3°. The plane lens phase shift unit adopts the form of double-layer Rogers RT6002 medium surface covered with copper. Its structure is as follows Figure 3As shown, for all phase shift unit dielectric materials and dimensions, the length and width are both w=2mm, and the thickness is 0.254mm. The double-layer Rogers RT6002 dielectric is the upper dielectric and the lower dielectric respectively, and the three-layer metal resonant structure is etched on the surface of the upper dielectric and the lower dielectric at intervals, that is, the upper patch is etched on the outer surface of the upper dielectric, the middle patch is etched between the dielectric and the lower dielectric, and the lower patch is etched on the outer surface of the lower dielectric. This structure makes up for the problem of insufficient phase shift range caused by the small dielectric thickness, and finally achieves a large range of 360° phase shift. Among them, the upper patch, the middle patch and the lower patch are all copper conductors, the upper patch and the lower patch have the same size and shape, and their shape is a cross, and the middle patch adopts a circular ring nested circular structure. Through simulation in CST Microwave Studio, it is proved that the S11 (reflection coefficient) of the phase shift unit is very small, while the S21 (transmission coefficient) is very large. The results show that most of the electromagnetic waves radiated from the feed horn antenna can pass through the phase shift unit, which is a prerequisite for designing a high-performance transmission unit. By changing the size of the three-layer copper conductor, a phase shift structure covering a 360° phase range and having good transmission performance is achieved. The specific parameters of each phase shift unit in this example are given below:

[0037] 1. 0° phase shift unit: w1=0.6mm, l1=1.05mm, r=1.1mm, r1=1.2mm, r2=1.3;

[0038] 2. 45° phase shift unit: w1=0.5mm, l1=1mm, r=1mm, r1=1.1mm, r2=1.2;

[0039] 3. 90° phase shift unit: w1=0.2mm, l1=0.95mm, r=0.6mm, r1=0.7mm, r2=1;

[0040] 4. 135° phase shift unit: w1=0.1mm, l1=0.1mm, r=0.4mm, r1=1.1mm, r2=1.36;

[0041] 5. 180° phase shift unit: w1=0.1mm, l1=0.48mm, r=0.06mm, r1=0.16mm, r2=0.22;

[0042] 6. 225° phase shift unit: w1=1.09mm, l1=0.9mm, r=1.16mm, r1=1.86mm, r2=1.96;

[0043] 7. 270° phase shift unit: w1=1mm, l1=1mm, r=1.22mm, r1=1.72mm, r2=1.92;

[0044] 8. 315° phase shift unit: w1=0.86mm, l1=1mm, r=1.14mm, r1=1.24mm, r2=1.34;

[0045] The biggest difference between the wide beam plane lens in the present invention and the high gain plane lens antenna is the distribution mode of the lens array phase. For high gain plane lens antennas, since the feed source is far away from the array and the focal length is much larger than the antenna size, the feed antenna is usually abstracted as a point source. The feed source radiates spherical waves. In order to achieve high gain characteristics, the high gain plane lens needs to convert the spherical waves into plane waves. This conversion is achieved by spreading from the center of the lens to the surrounding areas with a specific phase gradient. According to the analysis of the principles of geometric optics, there is an optical path difference between the electromagnetic wave to the center of the lens and the edge of the lens, so the phase difference of the phase shift unit at the two points is:

[0046]

[0047] Where m and n represent the number of phase shift units on the H and E planes from any unit of the lens to the center of the lens, respectively. p is the length and width of the unit, i.e. 2 mm. Then m*p and n*p can represent the distance from any unit of the array surface to the center of the lens. Since the phase has a periodicity with a period of 2π, K is any integer greater than or equal to 0.

[0048] In order to achieve the wide beam characteristic, the present invention adds an additional beam widening phase based on the phase distribution of the high-gain planar lens antenna. n The H-plane beam width is significantly widened while the E-plane beam width remains basically unchanged. The additional phase gradient obeys the following formula:

[0049]

[0050] In formula (2), n is the number of the current unit from left to right on the H plane, and N is the total number of units in this direction. The beam width can be controlled by changing the gradient coefficient α. When α increases, the beam width will be widened and the gain will decrease. Therefore, this design method can be applied to many different types of application scenarios.

[0051] According to formula (1), different α values ​​are selected, the focal length F = 60 mm, the phase shift required for each position is calculated, and the designed phase shift units are arranged in sequence to form a 51*51 array with a total size of 102 mm*102 mm. The performance of the lens antenna is simulated by aligning the phase center of the feed antenna with the focus of the plane lens.

[0052] When α = 0, the overall gain of the lens antenna is 30.5 dB, the H-plane beam width is 3.6°, and the E-plane beam width is 3°;

[0053] When α = 0.5, the overall gain of the lens antenna is 28.6 dB, the H-plane beam width is 6.1°, and the E-plane beam width is 3°;

[0054] When α = 1, the overall gain of the lens antenna is 26.4 dB, the H-plane beam width is 10.3°, and the E-plane beam width is 3°;

[0055] When α=2, the overall gain of the lens antenna is 23.5 dB, the H-plane beam width is 14.8°, and the E-plane beam width is 3°.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A variable beam width wide beam planar lens antenna, comprising a horn feed antenna and a planar lens composed of a plurality of phase shift units, characterized in that: The plane lens realizes the refraction of electromagnetic waves by setting a gradient phase, wherein an additional gradient phase is added to the antenna H plane on the basis of compensating the spatial phase caused by the optical path difference. , gradient phase As shown below: ， Where: n is the number of the current unit from left to right on the H surface, N is the total number of units from left to right on the H surface, is the gradient coefficient. By changing the gradient coefficient Control beam width when As it increases, the beam width widens and the gain decreases.

2. According to claim 1, a variable beam width wide beam planar lens antenna is characterized in that: The phase shift unit is composed of a three-layer metal resonance structure with double resonance characteristics and a double-layer medium, and the three-layer metal resonance structure is etched at intervals on the surface of the double-layer medium.

3. The variable beam width wide beam planar lens antenna according to claim 2, characterized in that: The double-layer medium includes an upper medium and a lower medium made of metamaterials.

4. The variable beam width wide beam planar lens antenna according to claim 3, characterized in that: The three-layer metal resonant structure comprises an upper patch arranged on the outer surface of the upper medium, a middle patch arranged between the upper medium and the lower medium, and a lower patch arranged on the outer surface of the lower medium.

5. The variable beam width wide beam planar lens antenna according to claim 4, characterized in that: The upper patch, the middle patch and the lower patch are all made of copper. The upper patch and the lower patch are cross-shaped with the same size, and the middle patch adopts a circular structure with a circular ring nested in a circular shape.

6. The variable beam width wide beam planar lens antenna according to claim 5, characterized in that: The sizes of the upper patch, the middle patch and the lower patch of the phase shift unit are adjusted to obtain 0°, 45°, 90°, 135°, 180°, 225°, 270° and 315° phase shift units.

7. The variable beam width wide beam planar lens antenna according to claim 1, characterized in that: The entire array surface of the plane lens has 51×51 phase shift units with a thickness of 0.5 mm. The length and width of each phase shift unit are both 2 mm.

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