A low-sidelobe ridge gap waveguide slot antenna array applied to millimeter wave radar

Abstract

The application discloses a low-sidelobe ridge gap waveguide slot antenna array applied to a millimeter wave radar, which comprises a first metal plate, metal columns, a metal ridge and a second metal plate; wherein a plurality of metal columns are periodically arranged around the metal ridge, the first metal plate comprises a metal bottom plate and a rectangular waveguide; a slot antenna array is arranged on the second metal plate and constitutes a radiation antenna layer; the metal ridge comprises a multi-stage T-shaped power divider, adopts a discontinuous metal ridge structure, realizes a same-phase unequal power division feeding network through T-shaped sections with different power division ratios; the antenna array adopts a ridge gap waveguide structure, reduces the difficulty of antenna processing and assembly, has the advantages of small loss, high efficiency, large power capacity and the like, and shows high-gain and low-sidelobe radiation characteristics in a two-dimensional direction.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to a low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar. Background Technology

[0002] With the development of autonomous driving and driverless vehicles, millimeter-wave automotive radar has attracted much attention due to its wide range of applications. As a key component in millimeter-wave radar systems for receiving and transmitting signals, the performance of the antenna directly affects the overall performance of the system. In the 77GHz millimeter-wave band, antennas are typically small in size and high in precision, posing greater challenges to antenna design. Furthermore, to achieve high resolution and long-range detection in automotive radar, millimeter-wave antenna arrays need to possess high-gain, low-sidelobe radiation characteristics.

[0003] Microstrip patch antennas and substrate-integrated waveguide antennas have advantages such as small size and ease of manufacturing, and are widely used in automotive radar. However, in the millimeter-wave band, microstrip planar antennas are prone to high dielectric loss and parasitic radiation, affecting the antenna's radiation efficiency. Waveguide slot antenna arrays have advantages such as easy control of aperture distribution, compact structure, and ease of integration, which can solve the problems of low efficiency and high loss, and can effectively suppress sidelobe levels in the high-frequency band. Traditional rectangular waveguide structures are a common form of metal waveguides. Because rectangular waveguides are fully enclosed structures, they place high demands on antenna processing and welding, requiring strict electrical contact between layers, which increases the difficulty of antenna assembly. Gap waveguide slot array antennas can effectively overcome the shortcomings of traditional rectangular waveguide slot array antennas, avoiding various problems in the manufacturing process. Using a gap waveguide structure to design waveguide slot antenna arrays has significant advantages.

[0004] In low-sidelobe antenna array design, the feed network consists of multiple cascaded unequal power dividers. Existing waveguide T-type power dividers are difficult to control individually in terms of phase and cross-sectional area. For unequal power dividers with large cross-sectional areas, significant phase differences exist between the output ports, failing to meet antenna requirements. Currently, most design methods use phase shifters to adjust the output port phase difference, but this feed structure increases antenna size and complexity, hindering fabrication. Therefore, designing a phase-consistent unequal power divider feed network to realize a ridge-gap waveguide slot antenna array with low sidelobes shows great promise for applications in millimeter-wave automotive radar. Summary of the Invention

[0005] The purpose of this invention is to address the application requirements of current millimeter-wave automotive radar systems and the shortcomings of existing technologies by proposing a ridge-gap waveguide slot antenna array with high gain and low sidelobe characteristics. By employing a stepped slot structure, the antenna's operating bandwidth is extended; by utilizing the weak coupling of discontinuous ridges, the output port of the feed network achieves a high power ratio and a small phase difference, enabling the two-dimensional low sidelobe radiation characteristics of the waveguide slot antenna array. This antenna, employing a ridge-gap waveguide structure, effectively solves the defects of traditional rectangular waveguides, such as high fabrication difficulty and phase imbalance, providing a feasible solution for practical engineering applications.

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

[0007] A low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar includes a first metal plate, an air gap layer, and a second metal plate arranged sequentially from bottom to top.

[0008] The first metal plate includes a metal base plate and a rectangular waveguide; the upper surface of the metal base plate is provided with a plurality of periodic metal pillars and metal ridges.

[0009] A slotted antenna array is provided on the second metal plate; an air gap layer is formed between the metal pillars and metal ridges and the second metal plate.

[0010] in:

[0011] The first metal plate, the metal pillar, the metal ridge, the air gap layer, and the second metal plate together constitute a ridge gap waveguide, which includes a ridge gap waveguide feed network and a ridge gap waveguide slot antenna array.

[0012] The ridge gap waveguide feed network includes a rectangular waveguide-ridge gap waveguide transition structure and a multi-stage parallel-fed ridge gap waveguide power divider. The rectangular waveguide-ridge gap waveguide transition structure is used to convert the TE10 mode of the input rectangular waveguide into a quasi-TEM mode and output it to the multi-stage parallel-fed ridge gap waveguide power divider. The multi-stage parallel-fed ridge gap waveguide power divider includes one input terminal and k output terminals (k≥2).

[0013] The ridge gap waveguide slot antenna array comprises k waveguide slot antenna arrays (k≥2); the waveguide slot antenna array is a series-fed slot antenna array, and each waveguide slot antenna array consists of n slot elements (n≥1). The k output terminals of the multi-stage parallel-fed ridge gap waveguide power divider are respectively connected to the signal input terminals of the k waveguide slot antenna arrays.

[0014] Preferably, the metal ridge end of the rectangular waveguide-ridge gap waveguide transition structure is arranged in a stepped manner.

[0015] Preferably, the multi-stage parallel-fed ridge gap waveguide power divider is composed of multiple in-phase unequal ratio T-type power dividers cascaded together.

[0016] Preferably, the metal ridge of the in-phase unequal ratio T-type power divider is a discontinuous ridge, broken at the T-junction, with metal pillars distributed on both the inner and outer sides of the metal ridge. The discontinuous ridge configuration of the metal ridge of the in-phase unequal ratio T-type power divider adjusts the amplitude and phase differences between the output ports. A groove is provided at the T-junction of the in-phase unequal ratio T-type power divider, and chamfers are provided at the right-angle turns on both sides. By providing the groove and chamfers, the in-phase unequal ratio T-type power divider achieves wideband characteristics. The in-phase unequal ratio T-type power divider includes a T-junction equal-division power divider, a second-order unequal-division power divider, a T-junction unequal-division power divider, and a discontinuous ridge type unequal-division power divider.

[0017] Preferably, the multi-stage parallel-feed ridge gap waveguide power divider is arranged in an axisymmetric manner.

[0018] Preferably, two rows of periodically arranged metal pillars are arranged between the waveguide slot antenna arrays.

[0019] Preferably, in each waveguide slot antenna array, the slot elements are alternately distributed on both sides of the center line of the waveguide slot antenna array, and the length and offset of the slot elements increase sequentially from both ends of the waveguide slot antenna array toward the middle slot element; the slot elements are spaced equally apart.

[0020] Preferably, the waveguide slot antenna array is arranged in a centrally symmetrical manner.

[0021] Preferably, the gap unit adopts a stepped gap structure.

[0022] The present invention has the following advantages:

[0023] (1) The antenna adopts a ridge gap waveguide structure, which solves the problem of high processing requirements of traditional rectangular waveguides and reduces the difficulty of antenna assembly.

[0024] (2) By adjusting the amplitude ratio and phase difference of the output port of the feed network through the metal structure of the discontinuous ridge, the waveguide slot antenna array has a lower sidelobe level in the two-dimensional direction.

[0025] (3) The array has a simple structure, is easy to design, has low loss and high efficiency. Attached Figure Description

[0026] Figure 1 This is a three-dimensional structural schematic diagram of the present invention;

[0027] Figure 2 This is a side view of the present invention;

[0028] Figure 3 This is a top view of the present invention;

[0029] Figure 4 This is a schematic diagram of the ridge gap waveguide slot antenna array of the present invention;

[0030] Figure 5 This is a schematic diagram of the ridge gap waveguide feed network of the present invention;

[0031] Figure 6 This is a simulation diagram of the reflection coefficient and gain of the waveguide slot antenna array of the present invention;

[0032] Figure 7 This is a simulation diagram of the reflection coefficient and output port amplitude difference of the ridge gap waveguide feed network of the present invention;

[0033] Figure 8 This is a simulation diagram of the output port phase difference of the ridge gap waveguide feed network of the present invention;

[0034] Figure 9 This is a simulation diagram of the reflection coefficient and gain of the low sidelobe ridge gap waveguide slot antenna array of the present invention;

[0035] Figure 10 This is the normalized E-plane and H-plane radiation pattern of the present invention at 77 GHz;

[0036] Figure 11 This is the normalized E-plane and H-plane radiation pattern of the present invention at 78 GHz;

[0037] Figure 12 This is the normalized E-plane and H-plane radiation pattern of the present invention at 79 GHz;

[0038] The diagram is labeled as follows: First metal plate M1, Second metal plate M2, Metal column B1, Metal ridge B2, Feed network 1, Waveguide slot antenna array 2, Rectangular waveguide-ridge gap waveguide transition structure 3, T-section equal power divider 4, Second-order unequal power divider 5, T-section unequal power divider 6, Discontinuous ridge unequal power divider 7, Slot element 8. Detailed Implementation

[0039] The present invention will be further analyzed below with reference to specific embodiments.

[0040] like Figure 1 As shown, a low sidelobe ridge gap waveguide slot antenna array structure for millimeter-wave radar includes a first metal plate M1, metal pillars B1, a metal ridge B2, and a second metal plate M2; wherein a plurality of metal pillars B1 are periodically arranged around the metal ridge B2, the first metal plate M1 includes a metal base plate and a rectangular waveguide; the metal base plate, metal pillars B1, metal ridge B2, and second metal plate M2 constitute a ridge gap waveguide feed network layer, and a stepped slot antenna array is disposed on the second metal plate M2 to form a radiating antenna layer.

[0041] like Figure 2 As shown, several metal pillars B1 and metal ridges B2 are located on the upper surface of the first metal plate M1, and the thickness of the first metal plate M1 is 2mm; a gap layer is left between the second metal plate M2 and the metal pillars B1, and the height of the air gap is less than one-quarter of the working wavelength.

[0042] like Figure 3 As shown, the low sidelobe ridge gap waveguide slot antenna array includes a feed network 1 and a radiating antenna array; wherein the radiating antenna array is composed of eight waveguide slot array antennas 2 arranged at equal intervals. In the ridge gap waveguide structure, at least two rows of metal pillars are distributed on one side of the metal ridge; the height of the metal pillars is d = 1 mm, and the cross-section is a square with a side length a = 0.4 mm; the height of the metal ridge is r = 0.8 mm, and the center-to-center spacing between the metal pillars on both sides of the metal ridge is g = 2 mm.

[0043] like Figure 4 As shown, the feed network 1 includes a rectangular waveguide-ridge gap waveguide transition structure 3 and a T-type power divider, forming a third-order 1-to-8 parallel feed network structure. The eight output ports of this feed network are directly connected to the radiating antenna array, providing the corresponding excitation amplitude for the antenna array to achieve low sidelobe radiation characteristics. In this embodiment, the required sidelobe level excitation amplitude is obtained using Taylor synthesis, and the amplitude ratio between the output ports is converted into dB values. Based on the required dB difference, a corresponding T-type power divider is designed.

[0044] The rectangular waveguide-ridge gap waveguide transition structure 3 converts the TE10 mode input from the rectangular waveguide into a quasi-TEM mode transmitted through the ridge gap waveguide. The metal ridge front end adopts a metal probe transition structure. The T-junction power divider needs to have a large amplitude ratio and a small phase difference. The amplitude difference and phase difference between the output ports of the power divider are adjusted by the coupling between discontinuous ridges. For a 1.8dB power divider, the corresponding amplitude difference between the output ports is achieved by adjusting the position of the T-junction groove.

[0045] like Figure 5 As shown, the radiating antenna array includes eight waveguide slot antenna arrays 2. Each waveguide slot antenna array is composed of eight radiating slot elements 8 fed in series. The series-fed waveguide slot antenna arrays are placed at equal intervals along the x-direction axial direction. Between the metal ridges of adjacent waveguide slot antenna arrays are two rows of periodic metal pillars.

[0046] The radial slot unit 8 adopts a stepped slot structure, which is placed alternately on both sides of the center line along the y-direction axial direction, with the length of the slot unit increasing by 0.02 mm in each step. The upper and lower slots have the same length, the upper slot has a width of 1.3 mm, and the lower slot has a width of 0.5 mm.

[0047] The series-fed waveguide slot antenna array is centrally symmetrically arranged, with the length and offset of the radiating slot elements decreasing sequentially from the middle to both sides. All slots are placed at equal intervals, and the center-to-center distance between adjacent slot elements is 2.4 mm.

[0048] Figure 6 The simulation diagram shows the reflection coefficient and gain of the waveguide slot antenna array of the present invention. The -10dB band is in the range of 76.7-79.5GHz, and the maximum gain within the band is 13.7dBi. Figure 7 The simulation diagram of the reflection coefficient and output port amplitude difference of the power supply network of the present invention shows that the reflection coefficient is less than -10dB in the frequency range of 75GHz to 81GHz, the amplitude difference between output port 2 and output port 3 at the center frequency (79.3GHz) is 5.3dB, and the amplitude difference between output port 4 and output port 5 is 1.8dB. Figure 8 The output port phase difference of the power supply network of the present invention is shown in the simulation diagram. The phase difference between each port is less than 10 degrees in the frequency range of 75 GHz to 80 GHz.

[0049] Figure 9 The simulation diagrams of the reflection coefficient and gain of the array designed for this invention show that the -10dB band is in the range of 77-79.4GHz, and the gain within the band is above 22dBi. Figure 10 , Figure 11 , Figure 12 The simulated normalized radiation patterns of the array designed in this invention at the center frequency (78GHz), low frequency (77GHz), and high frequency (79GHz) are shown in the E-plane and H-plane. It can be seen that the sidelobe electrical average of the array designed in this invention is less than -28dB in both the E-plane and H-plane patterns, indicating good low sidelobe characteristics.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the implementation of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and all such improvements and modifications should be included within the scope of protection of the claims of the present invention.

Claims

1. A low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar, characterized in that, It includes a first metal plate, an air gap layer, and a second metal plate arranged sequentially from bottom to top; The first metal plate includes a metal base plate and a rectangular waveguide disposed in the metal base plate; the upper surface of the metal base plate is provided with a plurality of periodic metal pillars and metal ridges; A slotted antenna array is disposed on the second metal plate; an air gap layer is formed between the metal pillars and metal ridges and the second metal plate; in: The first metal plate, the metal pillar, the metal ridge, the air gap layer, and the second metal plate together constitute a ridge gap waveguide. The ridge gap waveguide includes a ridge gap waveguide feed network and a ridge gap waveguide slot antenna array. The ridge gap waveguide feed network includes a rectangular waveguide-ridge gap waveguide transition structure and a multi-stage parallel-fed ridge gap waveguide power divider. The rectangular waveguide-ridge gap waveguide transition structure is used to convert the TE10 mode of the input rectangular waveguide into a quasi-TEM mode and output it to the multi-stage parallel-fed ridge gap waveguide power divider. The multi-stage parallel-fed ridge gap waveguide power divider includes one input terminal and k output terminals, where k≥2. The multi-stage parallel-fed ridge gap waveguide power divider is composed of multiple in-phase unequal-ratio T-type power dividers cascaded together. The metal ridge of the in-phase unequal ratio T-type power divider is a discontinuous ridge, broken at the T-junction, and the metal pillars are distributed on the inner and outer sides of the metal ridge; the in-phase unequal ratio T-type power divider uses the discontinuous ridge to adjust the amplitude difference and phase difference between the output ports; the T-junction of the in-phase unequal ratio T-type power divider is provided with a groove, and the right-angle turns on both sides are provided with chamfers.

2. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 1, characterized in that, The ridge gap waveguide slot antenna array includes k waveguide slot antenna arrays; the waveguide slot antenna array is a series-fed slot antenna array, and each waveguide slot antenna array consists of n slot elements, where k≥2 and n≥1.

3. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 2, characterized in that, The k output terminals of the multi-stage parallel-fed ridge gap waveguide power divider are respectively connected to the signal input terminals of the k waveguide slot antenna arrays.

4. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 1, characterized in that, The metal ridge end of the rectangular waveguide-ridge gap waveguide transition structure is arranged in a stepped manner.

5. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 2, characterized in that, The multi-stage parallel-feed ridge gap waveguide power divider is arranged in an axisymmetric manner.

6. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 2, characterized in that, Two rows of periodically arranged metal pillars are arranged between the waveguide slot antenna arrays.

7. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 2, characterized in that, In each waveguide slot antenna array, slot elements are alternately distributed on both sides of the center line of the waveguide slot antenna array, and the length and offset of the slot elements increase sequentially from both ends of the waveguide slot antenna array toward the middle slot element; the slot elements are spaced equally apart.

8. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 7, characterized in that, The waveguide slot antenna array is arranged in a centrally symmetrical manner.

9. The low sidelobe ridge gap waveguide slot antenna array for millimeter-wave radar according to claim 7, characterized in that, The slot unit adopts a stepped slot structure.

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