A waveguide millimeter-wave radar antenna

Abstract

The present invention discloses a waveguide millimeter-wave radar antenna, which comprises a PCB board structure and a metal ridge waveguide structure. The PCB structure includes a dielectric board, and the dielectric board is provided with a microstrip line transition structure; the metal ridge waveguide structure is longitudinally collinearly slotted, the metal ridge waveguide structure is provided with a ridge waveguide transition structure, the metal ridge waveguide structure is arranged on the dielectric board, and the ridge waveguide transition structure is connected to the microstrip line transition structure. The present invention has the advantages of high efficiency, wide half-power beam width, low side lobes, and integration with the PCB board.

Description

Technical Field

[0001] The present invention relates to the field of electronic communications, and particularly to a waveguide millimeter-wave radar antenna. Background Art

[0002] Millimeter-wave antennas have become the mainstream in the research field of antenna design due to their advantages such as small component volume, high spatial resolution, and strong anti-interference ability. Compared with common patch array antennas, waveguide slot array antennas have the advantages of high antenna efficiency, stable performance, compact structure, easy realization of narrow beam high gain, and easy control of aperture field distribution, and have become the preferred form in millimeter-wave radar applications such as vehicle-mounted, airborne, and imaging technologies. Traditional rectangular cavity waveguide slot array antennas have always been a research hotspot in waveguide slot array antennas. From the position of the slot opening, they can be divided into two forms: wide-side slot opening and narrow-side slot opening. Subsequently, ridge waveguide slot array antennas and substrate integrated waveguide (SIW) slot array antennas have been derived. Ridge waveguide slot array antennas utilize the characteristic that ridge waveguides have a relatively low and stable phase shift constant. When the antenna is designed in a series-feed structure, the pointing of the highest gain beam with respect to frequency only brings a relatively low deflection angle, and the pattern stability is strong. SIW slot array antennas overcome some of the disadvantages of waveguide slot array antennas and have the advantages of microstrip patch antennas such as low profile, easy manufacturing, easy conformal shaping, and easy integration with chips.

[0003] The slot opening form of waveguide slot array antennas is usually a left-right staggered slot opening type. By controlling the offset distance of each slot from the longitudinal central axis of the waveguide, the amplitude of the radiation intensity of each slot is controlled, thereby adjusting the size of the sidelobe level in the main plane (H-plane). The disadvantage of this slot opening form is that when the vertical distance of the slot from the central axis is relatively large, the antenna will generate other higher grating lobes outside the main plane during operation, and at this time, it is difficult to locate and control the highest sidelobe level. Therefore, some scholars have developed waveguide collinear slot array antennas. The slots of such antennas are opened on the longitudinal central axis of the antenna structure, and the waveguide unit is a ridge waveguide, and the slot opening surface and the ridged surface are opposite. Compared with the slot array antenna with staggered slot openings, the pattern of the waveguide collinear slot array antenna is more symmetrical, and the maximum sidelobe level can be located and evaluated in the main plane. Generally, the amplitude of the slot radiation intensity can be controlled by three methods: controlling the depth of the metal grooves on both sides of the ridge, controlling the distance of the ridge from the waveguide central axis, and controlling the thickness of the waveguide sidewall. When the amplitudes of the slot radiation intensities show a certain ratio, the purpose of suppressing the sidelobe level can be achieved. However, when the above collinear slot scheme is applied to the millimeter-wave frequency band design, it is relatively difficult to ensure the processing accuracy of the metal waveguide of such collinear slot array antennas.

[0004] The disadvantages existing in the prior art are as follows:

[0005] (1) Traditional cavity waveguide slot array antenna: It is difficult to be integrated on the PCB board for interconnection with the chip. The feeding method directly through the waveguide requires the design of multi-layer metal waveguides, which leads to high processing difficulty, complex antenna structure, high manufacturing cost, and limited application scope. When slits are opened on the narrow side, higher cross-polarization will be generated;

[0006] (2) Ridge waveguide slot array antenna: The defects are still similar to those of the traditional cavity slot array antenna;

[0007] (3) SIW slot array antenna: It is fully filled with dielectric, with relatively large dielectric loss and low radiation efficiency. In addition, due to the limitation of its two-dimensional structure, it is difficult to control the transverse field distribution of its radiation aperture.

[0008] The slotting methods of the above three slot array antennas are generally staggered slotting, with poor pattern symmetry, secondary high sidelobes generated outside the main plane, and it is difficult to accurately locate and control the highest spatial sidelobe.

[0009] Therefore, in order to achieve the form of waveguide collinear slotting and overcome the problems that waveguide slot array antennas are difficult to be integrated with the PCB in millimeter-wave applications, complex waveguide processing, and high processing accuracy requirements, a new type of waveguide millimeter-wave slot array radar antenna is invented. Summary of the Invention

[0010] In order to overcome the shortcomings and deficiencies of the existing technology, the present invention provides a waveguide millimeter-wave radar antenna, which is easy to be integrated with the PCB and has the characteristics of low cost, low sidelobes, and stable pattern.

[0011] The present invention adopts the following technical solutions:

[0012] A waveguide millimeter-wave radar antenna, comprising,

[0013] A PCB board structure, including a dielectric board, and the dielectric board is provided with a microstrip line transition structure;

[0014] A metal ridge waveguide structure, the metal ridge waveguide structure has longitudinal collinear slots, the metal ridge waveguide structure is provided with a ridge waveguide transition structure, the metal ridge waveguide structure is arranged on the dielectric board, and the ridge waveguide transition structure is connected to the microstrip line transition structure.

[0015] The microstrip line transition structure is composed of a 50-ohm matching microstrip line, a quarter-wavelength microstrip line impedance transformation section, and a microstrip line with the same width as the upper ridge of the ridge waveguide connected in sequence.

[0016] The ridge waveguide transition structure is specifically a stepped structure, divided into three steps. The first step is connected to the microstrip line, the second step is a transition conversion structure to reduce the structural mutation, and the third step is connected to the upper ridge of the ridge waveguide.

[0017] A lower ridge of a ridged waveguide is arranged on the dielectric plate in a curve distribution, and the lower ridge of the ridged waveguide is formed by using metal through-holes to form ridges.

[0018] The energy of the slot radiation is controlled by the twist deformation of the lower ridge of the ridged waveguide to satisfy the Chebyshev distribution or the Taylor distribution.

[0019] Specifically, the longitudinal collinear slots of the metal ridged waveguide structure are that ten slots are opened along the longitudinal central axis direction of the ridge part.

[0020] Parallel lines formed by metal through-holes are arranged on both sides of the lower ridge of the ridged waveguide for fixing the PCB board structure and the metal ridged waveguide structure.

[0021] The diameter of the metal through-hole is 0.36 mm, and the hole pitch is approximately equal to twice the hole diameter.

[0022] The length of the slot is 1.89 mm and the width is 0.3 mm.

[0023] The length of the microstrip line transition structure is 10.84 mm, and the length of the metal waveguide is 14.27 mm.

[0024] Advantages of the present invention:

[0025] (1) The present invention provides a microstrip line transition structure, and the double ridged waveguide is series-fed through this transition structure to achieve low insertion loss and low return loss, reduce the design complexity of traditional waveguide antennas, improve the integration of antenna and PCB board design, and realize the direct interconnection and integration of PCB and waveguide;

[0026] (2) The antenna of the present invention adopts a series-fed feeding method. Since the waveguide structure is a partially dielectric-filled double ridged waveguide, the double ridged waveguide has a low single-mode cut-off frequency, a wide main-mode working area, and a stable phase constant. Therefore, compared with the cavity waveguide slot array and the single ridged waveguide slot array of the series-fed structure, the antenna beam directivity of the present invention is more stable;

[0027] (3) The amplitude of the slot radiation intensity of the present invention is controlled by the position of the through-holes on the PCB. Compared with the method of realizing collinear adjustment of the slot amplitude by a full-metal waveguide, the PCB processing accuracy is higher and its manufacturing is easier. In addition, the method of forming ridges by adding through-holes to the PCB board makes most of the energy of the electromagnetic wave concentrate in the air part of the waveguide. Compared with the traditional SIW antenna array, the dielectric loss generated during the transmission of the electromagnetic wave is reduced, thereby improving the antenna radiation efficiency;

[0028] (4) The radiation slots of the present invention are arranged in a collinear form, and the antenna pattern is highly symmetric, and the sidelobe level can be positioned and evaluated in the main plane (H plane). Description of the Drawings

[0029] Figure 1is a top view of the metal ridge waveguide structure of the present invention;

[0030] Figure 2 is a bottom view of the metal ridge waveguide structure of the present invention;

[0031] Figure 3 is a transverse cross-sectional view of the metal ridge waveguide decoupling strand of the present invention;

[0032] Figure 4 is a top view of the PCB board of the present invention;

[0033] Figure 5 is a bottom view of the PCB board of the present invention;

[0034] Figure 6 is an exploded view of the antenna of the present invention;

[0035] Figure 7 It is a schematic diagram of the overall structure of the antenna of the present invention;

[0036] Figure 8 It is a schematic diagram of the connection between the microstrip transition structure and the metal ridge waveguide of the present invention;

[0037] Figure 9 It is a graph of return loss S11 and insertion loss S21 of the microstrip-to-waveguide structure of the present invention;

[0038] Figure 10 is a schematic diagram of the reflection coefficient of the antenna of the present invention;

[0039] Figure 11 , Figure 12 and Figure 13 They are respectively the normalized gain diagrams of the antenna according to the embodiment of the present invention working at 76 GHz, 78 GHz and 80 GHz;

[0040] Figure 14 This is the gain diagram of the antenna of the embodiment of the present invention working at 76 GHz, 78 GHz, and 80 GHz in the H-plane direction (φ=0°), the maximum beam pointing angle range is -1.3° to 0.1°, and the beam pointing is relatively stable;

[0041] Figure 15 It is a simulation diagram of the antenna gain changing with frequency according to an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0043] Example

[0044] like Figures 1 - 8As shown in the figure, a waveguide millimeter-wave radar antenna, in the form of a partially dielectric-filled double-ridge waveguide collinear slot antenna, is used for vehicles. The specific structure includes a PCB board structure and a metal ridge waveguide structure 7. The two parts are fixed by welding or screws to form a partially dielectric-filled double-ridge waveguide, and the structure of the entire antenna can be obtained. The entire antenna is provided with a wave port 5 and a wave port 8.

[0045] The PCB board structure includes a dielectric board. The dielectric board is provided with a microstrip line transition structure 2. The microstrip line transition structure is composed of a 50-ohm matching microstrip line, a quarter-wavelength microstrip line impedance transformation section, and a microstrip line 6 with the same width as the upper ridge of the ridge waveguide connected in sequence. The microstrip line transition structure performs series feeding on the metal ridge waveguide structure (waveguide radiation unit).

[0046] The dielectric board is copper-clad ground.

[0047] The lower ridge of the ridge waveguide is arranged on the dielectric board in a curve distribution. The lower ridge 4 of the ridge waveguide is formed by metal through-holes to form ridges. By changing the position of the metal through-hole ridges on the PCB board, the amplitude of the radiation intensity of each slot is adjusted and has a certain distribution, and this distribution satisfies the Chebyshev or Taylor distribution, so as to obtain a lower sidelobe level. The size of the radiation energy of each slot is determined by the degree of distortion of the lower ridge. The PCB board and the metal single-ridge waveguide are combined to form a partially dielectric-filled double-ridge waveguide, which has a lower single-mode cut-off frequency and a dispersion curve that changes slowly with frequency.

[0048] Parallel lines composed of metal through-holes 3 are arranged on both sides of the lower ridge of the ridge waveguide for fixing the PCB board structure and the metal ridge waveguide structure.

[0049] The diameter of the metal through-holes on the dielectric board is 0.36 mm, and the hole pitch is approximately equal to twice the hole diameter.

[0050] The metal ridge waveguide structure. The metal ridge waveguide structure has longitudinal collinear slots. The metal ridge waveguide structure is provided with a ridge waveguide transition structure. The metal ridge waveguide structure is arranged on the dielectric board. The ridge waveguide transition structure is connected to the microstrip line transition structure. The metal ridge waveguide structure is a double-ridge structure, including an upper ridge of the ridge waveguide and a lower ridge of the ridge waveguide.

[0051] The ridge waveguide transition structure is designed as a stepped structure at the contact port between the metal ridge waveguide and the microstrip line to achieve lower insertion loss and lower return loss. The stepped structure is located on the longitudinal center line of the metal ridge waveguide structure and at the front end of the waveguide structure. It is divided into three steps. The first step is connected to the microstrip line and has the same width as the connected microstrip line. The second step is a transition conversion structure to reduce the structural mutation. The third step is connected to the upper ridge in the double-ridge waveguide.

[0052] The metal ridge waveguide structure has longitudinal collinear slits. Specifically, there are ten slits 1 along the longitudinal central axis direction on the ridge. The ten slits are spaced at a certain distance and arranged in a straight line. The length of each slit is 1.89 mm and the width is 0.3 mm. The entire slotted metal waveguide is made of copper.

[0053] The dielectric plate is Rogers 3003, with a relative dielectric constant of 3, a tangent of the electric loss angle of 0.0013, and a thickness of 0.254 mm.

[0054] In this embodiment, the length of the microstrip transition structure is 10.84 mm, and the length of the metal waveguide is 14.27 mm.

[0055] In this embodiment, the 50-ohm matching microstrip line is connected to one side of the dielectric plate. A part of the microstrip line with the same width as the upper ridge of the ridge waveguide is arranged between two parallel lines. The microstrip line transition structure and the lower ridge of the ridge waveguide are both located on the longitudinal center line of the dielectric plate.

[0056] In this embodiment, the radiation unit is realized by partially filling a double-ridge waveguide with collinear slits. The "double ridges" ensure that the electromagnetic wave has a lower single-mode cut-off frequency during propagation in the waveguide and a stable phase shift constant in the band, so that the deviation angle of the maximum beam direction of the antenna with respect to frequency change is smaller, and it has relatively stable directivity.

[0057] The following is a detailed description of the results of the embodiments of the present invention.

[0058] In the embodiments of the present invention, simulation software is used to simulate the echo loss, insertion loss, efficiency, radiation pattern, and gain of the waveguide millimeter-wave radar slot array antenna.

[0059] Figure 9 The curves of the echo loss S11 and the insertion loss S21 of the transition structure provided in the example are shown. As can be seen from the figure, in the frequency band of 70 GHz to 85 GHz, the echo loss S11 < -10 dB, and the insertion loss S21 < 0.63 dB.

[0060] Figure 10 The schematic diagram of the reflection coefficient of the antenna provided in the embodiments of the present invention is shown. As can be seen from the figure, the impedance bandwidth of the antenna is 76 GHz to 80.25 GHz, and its relative bandwidth is 5.45%.

[0061] Figures 11 - 13 The normalized gain diagrams of the antenna provided in the embodiments of the present invention working at 76 GHz, 78 GHz, and 80 GHz respectively are shown. As can be seen from the figure, in the H-plane direction (φ = 0°), the sidelobe level is lower than -20 dB, achieving a good sidelobe suppression effect; in the E-plane direction (φ = 90°), its half-power beam width is greater than 120°.

[0062] Figure 14These are the gain diagrams of the antenna operating at 76 GHz, 78 GHz, and 80 GHz respectively in the H-plane direction (φ = 0°). The maximum beam pointing deviation range is from -1.3° to 0.1°, and the beam pointing is relatively stable.

[0063] Figure 15 This is the simulation diagram of the antenna gain varying with frequency in the embodiment of the present invention. As can be seen from the figure, the in-band gain range of the antenna is from 13.5 dBi to 13.9 dBi in the frequency band of 76 GHz to 80.25 GHz.

[0064] It can be seen from the simulation results that the waveguide collinear slot array millimeter-wave radar antenna of the present invention has significant advantages such as being easy to integrate with the PCB, low side lobes, and wide beams.

[0065] The above embodiments are the preferred embodiments of the present invention, but the implementation modes of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement modes and are all included in the protection scope of the present invention.

Claims

1. A waveguide millimeter-wave radar antenna, characterized in that, it includes, a PCB board structure including a dielectric board, and a microstrip line transition structure is provided on the dielectric board; a metal ridge waveguide structure, the metal ridge waveguide structure has longitudinally collinear slits, a ridge waveguide transition structure is provided on the metal ridge waveguide structure, the metal ridge waveguide structure is provided on the dielectric board, and the ridge waveguide transition structure is connected to the microstrip line transition structure; a ridge waveguide lower ridge distributed in a curve is provided on the dielectric board, and the ridge waveguide lower ridge is formed by metal vias to form a ridge; parallel lines formed by metal vias are provided on both sides of the ridge waveguide lower ridge for fixing the PCB board structure and the metal ridge waveguide structure; the microstrip line transition structure is composed of a 50-ohm matching microstrip line, a quarter-wavelength microstrip line impedance transformation section, and a microstrip line with the same width as the ridge waveguide upper ridge connected in sequence.

2. The waveguide millimeter-wave radar antenna according to claim 1, characterized in that, the ridge waveguide transition structure is specifically a stepped structure, divided into three steps. The first step is connected to the microstrip line, the second step is a transition conversion structure to reduce structural mutations, and the third step is connected to the ridge waveguide upper ridge.

3. The waveguide millimeter-wave radar antenna according to claim 1, characterized in that, the energy of the gap radiation is controlled by the twisting and deformation of the ridge waveguide lower ridge to satisfy the Chebyshev distribution or the Taylor distribution.

4. The waveguide millimeter-wave radar antenna according to claim 1, characterized in that, the longitudinal collinear slits of the metal ridge waveguide structure are specifically that ten slits are opened along the longitudinal central axis direction on the ridge part.

5. The waveguide millimeter-wave radar antenna according to claim 1, characterized in that, the diameter of the metal via is 0.36 mm, and the hole pitch is equal to twice the hole diameter.

6. The waveguide millimeter-wave radar antenna according to claim 4, characterized in that, the length of the slit is 1.89 mm and the width is 0.3 mm.

7. The waveguide millimeter-wave radar antenna according to claim 1, characterized in that, the length of the microstrip line transition structure is 10.84 mm, and the length of the metal waveguide is 14.27 mm.

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