CN116231338B

CN116231338B - Low sidelobe millimeter wave gap waveguide slot array antenna

Info

Publication number: CN116231338B
Application number: CN202211695033.3A
Authority: CN
Inventors: 李毅响; 王秉中
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2022-12-28
Filing date: 2022-12-28
Publication date: 2023-10-13
Anticipated expiration: 2042-12-28
Also published as: CN116231338A

Abstract

The invention discloses a low sidelobe millimeter wave gap waveguide slot array antenna, and belongs to the technical field of antennas. The array antenna comprises a metal plate M1, an air gap layer A1, a metal plate M2, an air gap layer A2 and a metal plate M3 which are sequentially arranged from bottom to top; wherein the metal plate M1 and the lower metal column, the metal ridge, the air gap layer A1 and the metal plate M2 above the metal plate M form a gap waveguide feed network together; the metal plate M2, the upper metal column above, the air gap layer A2 and the metal plate M3 together form a gap waveguide back cavity coupling network; the metal plate M2 is provided with a 90 ° twisted waveguide unit, and the metal plate M3 is provided with a radiation unit. According to the invention, the tangential planes of the E-plane and H-plane directional diagrams of the antenna are changed through the radiation unit, so that extremely low side lobes are obtained; by reasonably designing the structures of all parts, S11 is less than or equal to-15 dB, XPD is more than 30.3dB in the whole working frequency Band V-Band, caliber efficiency is higher than 79.2%, and main polarization patterns of E face and H face meet the highest envelope level of EN 302 standard of European telecommunication standards institute of the frequency Band.

Description

Low sidelobe millimeter wave gap waveguide slot array antenna

Technical Field

The invention belongs to the technical field of antennas, and particularly relates to a low sidelobe millimeter wave gap waveguide slot array antenna.

Background

At present, mobile communication is in the 5G enhanced evolution stage, and a higher transmission rate requirement is put forward for microwave backhaul, so that the industry aims at millimeter waves with abundant spectrum resources. The V-Band (57 GHz-66 GHz) has a relatively wide bandwidth, and the frequency spectrum cost is low or free, so the V-Band has been paid attention to and researched.

In addition, with the acceleration of 5G base station construction, the backhaul network in many areas becomes very crowded, and the microwave antennas in the same site face the same-frequency interference pain points caused by dense deployment. Thus, the industry proposes a higher low sidelobe requirement for the antenna for 5G microwave backhaul.

Furthermore, people attach higher and higher importance to vision and electromagnetic pollution, and in urban areas with high vision requirements, the traditional mainstream microwave antenna, namely the parabolic reflecting surface antenna, is not preferred because of difficult integration and beautification, and people prefer a waveguide slot array antenna with the advantages of low profile, compact structure, high radiation efficiency, large power capacity, easy integration and the like. However, the disadvantages of waveguide slot array antennas in terms of performance and cost have always limited their large-scale commercial use.

For performance, the conventional waveguide slot array antenna mostly adopts a series feed or a series parallel feed mode, and has limited bandwidth and antenna efficiency. In view of the above problems, parallel feed is generally adopted in the industry to solve, but the side lobe level of the parallel feed waveguide slot array antenna is high, and even the minimum envelope requirement Class 1 of ETSI is not satisfied. For the problem of high side lobe level of the parallel fed waveguide slot array antenna, two common solutions exist at present: firstly, array synthesis, secondly, the whole antenna port surface is inclined along a certain angle. The former is influenced by weight loss, certain caliber efficiency is sacrificed, bandwidth is required to be considered, and the design is complex; the latter would then cause a new performance problem-degradation of the cross-polarization discrimination, affecting the system communication capacity.

For cost, the traditional waveguide slot array antenna processing scheme mainly adopts CNC (computer numerical control) machining, is long in time consumption and high in cost, and is not suitable for mass production. In recent years, the state of the art has evolved rapidly, emerging new processes such as laser etching, vacuum diffusion welding, 3D printing, etc. In order to reduce the cost, a few attempts are made in the combination of the waveguide slot array antenna and the new technology, and the cost is still high despite a few achievements. One technique, known as gap waveguide, then provides a new direction for cost reduction. The gap waveguide technology is combined with the plastic metallization technology, so that the processing cost can be reduced, the assembly requirement can be reduced, the product qualification rate can be improved, and better performance (low loss and wide standing wave bandwidth) can be obtained. However, in the prior report, the pattern of the gap waveguide slot array antenna for microwave return is at most only the Class 2 Class which meets the ETSI standard in a critical way, and the cross polarization discrimination rate is not high.

In summary, the development of a millimeter wave waveguide slot array antenna with low cost and high performance is urgent from the viewpoints of market, technology or cost.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a low sidelobe millimeter wave gap waveguide slot array antenna.

The technical scheme adopted by the invention is as follows:

the low sidelobe millimeter wave gap waveguide slot array antenna is characterized by comprising a metal plate M1, an air gap layer A1, a metal plate M2, an air gap layer A2 and a metal plate M3 which are sequentially arranged from bottom to top.

The upper surface of the metal plate M1 is provided with a lower layer metal column and a metal ridge; the upper surface of the metal plate M2 is provided with an upper layer metal column.

The metal plate M1, the lower metal column, the metal ridge, the air gap layer A1 and the metal plate M2 together form a ridge gap waveguide feed network; the ridge gap waveguide feed network is used for TE to be fed in ₁₀ The mode is converted into quasi-TEM mode, and then is equally divided into 2-K paths, and then is converted into TE ₁₀ The mode is output from output ports arranged in a2 (K/2) x 2 (K/2) array, and TE is output from odd and even rows ₁₀ The direction of the polarization of the mold is reversed; wherein K is an even number of 2 or more, and K is an even number of 6 or more if the ETSI Class3 envelope is to be satisfied.

The metal plate M2 is provided with 2-K90 DEG twisted waveguide units which are arranged in a 2-K/2-x-2-K/2 array, and the 90 DEG twisted waveguide units in the odd-numbered rows and the 90 DEG twisted waveguide units in the even-numbered rows are reversely arranged for enabling TE fed by a ridge gap waveguide feed network ₁₀ And after the polarization directions of the modes are in phase, the modes are fed into the gap waveguide back cavity coupling network.

The metal plate M2, the upper metal column, the air gap layer A2 and the metal plate M3 together form a gap waveguide backA cavity coupling network; the gap waveguide back cavity coupling network comprises 2-K gap waveguide resonant cavities which are arranged in a2 (K/2) x 2 (K/2) array; TE to be fed into the gap waveguide resonant cavity ₁₀ The mode is split into 4 paths in phase with equal amplitude and then fed into the 4 radiating elements respectively.

The metal plate M3 is provided with 2 (K+2) radiating units which are arranged in a2 (K/2+1) x 2 (K/2+1) array and are used for radiating the fed electromagnetic signals into a free space.

The radiation unit is of a slit structure penetrating through the metal plate M3 and consists of an excitation slit, a matching slit and a radiation slit which are sequentially arranged from bottom to top; the excitation slit, the matching slit and the radiation slit are rectangular slits with short edges rounded off; the long sides of the excitation slits are parallel to the long sides of the gap waveguide resonant cavity, the long sides of the matching slits and the radiation slits are arranged at an included angle theta with the long sides of the excitation slits, and the value range of theta is-37 degrees to-33 degrees or 33 degrees to 37 degrees. According to the invention, the tangential planes of the E-plane and H-plane directional patterns of the antenna are changed by rotating the matching slit and the radiation slit by the angle theta, so that extremely low side lobes are obtained.

Further, the size of the matching slit is smaller than the size of the radiation slit.

Further, the ridge gap waveguide feed network comprises a rectangular waveguide-ridge gap waveguide power divider, a multistage parallel feed ridge gap waveguide T-shaped power divider and 2-K ridge gap waveguide-rectangular waveguide transition structures.

Wherein the rectangular waveguide-ridge clearance waveguide power divider divides the input TE ₁₀ The mode is converted into a quasi-TEM mode, and two paths of signals with equal amplitude and opposite phase are output to the air gap layer A1 for transmission; the multistage parallel feed ridge gap waveguide T-shaped power divider is used for equally dividing quasi-TEM modes propagating in the air gap layer A1 into 2-way and then converting the quasi-TEM modes into TE through a ridge gap waveguide-rectangular waveguide transition structure respectively ₁₀ And (5) die-casting and outputting.

Further, the rectangular waveguide-ridge gap waveguide power divider comprises an input rectangular waveguide arranged in the center of the metal plate M1, a lower-layer metal column arranged on the upper surface of the metal plate M1 and a metal ridge; the metal ridge comprises two metal ridge lines which are symmetrically arranged on the outer side of the long side of the input rectangular waveguide; the ends of the two metal ridge lines are respectively provided with a metal probe, and the metal probes extend into the projection area of the input rectangular waveguide; the outer sides of the input rectangular waveguide and the metal ridge are surrounded by lower metal columns which are periodically arranged. The rectangular waveguide-ridge gap waveguide power divider not only has the electromagnetic signal mode conversion function, but also has the one-to-two power dividing function.

Further, the multistage parallel feed ridge gap waveguide T-shaped power divider is formed by cascading a plurality of ridge gap waveguide T-shaped power dividers; the ridge clearance waveguide T-shaped power divider comprises a special-shaped T-shaped metal ridge and a lower metal column which is arranged in a periodic manner and surrounds the outer side; the special-shaped T-shaped metal ridge is provided with an inverted trapezoid groove at the T-shaped junction, and the input end of the special-shaped T-shaped metal ridge is provided with a metal ridge matching section; by arranging the inverted trapezoid groove and the metal ridge matching section, the ridge gap waveguide T-shaped power divider obtains broadband characteristics.

Further, the cavity structure of the 90 DEG twist waveguide unit comprises an input rectangular waveguide cavity, a 90 DEG polarization conversion cavity and an output rectangular waveguide cavity.

The narrow side dimension of the input rectangular waveguide cavity is b1, and the wide side dimension of the input rectangular waveguide cavity is a1; the 90-degree polarization conversion cavity is obtained by cutting off small cuboids with the same size at one diagonal position of the square wave guide cavity with the side length of a1 and cutting off large cuboids with the same size at the other diagonal position; any cross section of the small cuboid perpendicular to the square wave guide axis is a square with a side length of c2, any cross section of the large cuboid perpendicular to the square wave guide axis is a square with a side length of c1, and c1 is smaller than c2, a1=b1+2×c2.

The invention can obtain excellent performance by adopting the comprehensive means. S11 is less than or equal to-15 dB in the whole working frequency Band V-Band (57 GHz-66 GHz), XPD is more than 30.3dB, caliber efficiency is higher than 79.2%, E-plane and H-plane main polarization patterns meet the highest envelope level of European Telecommunication Standards Institute (ETSI) EN 302 standard of the frequency Band-Class 3B, and the first side lobe suppression ratio minimum value of the E-plane and H-plane main polarization patterns is higher than 30.2dB. In conclusion, the antenna disclosed by the invention has the advantages of excellent performance, low cost, low profile and easiness in integration and beautification, and is very suitable for short-distance 5G microwave small station return.

Drawings

Fig. 1 is a three-dimensional top view and bottom view assembly diagram of an extremely low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention;

FIG. 2 is a schematic diagram of the structural relationship of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention;

FIG. 3 provides a top view of a feed network layer of the present invention;

FIG. 4 is a three-dimensional assembly, side and top view of a rectangular waveguide-ridge interstitial waveguide power divider provided by the present invention;

FIG. 5 is a three-dimensional assembly, side and top view of a ridge interstitial waveguide T-shaped power divider provided by the present invention;

FIG. 6 provides a three-dimensional assembly, side and top view of a ridge interstitial waveguide-rectangular waveguide transition provided by the present invention;

FIG. 7 is a top view of a back cavity layer, a top view of a gap waveguide cavity and a three-dimensional assembly view provided by the present invention;

FIG. 8 is a three-dimensional view and a cross-sectional view of a simulation model for integrally processing a 90 DEG twisted waveguide provided by the invention;

FIG. 9 is a top view of a radiation layer provided by the present invention;

FIG. 10 is a schematic diagram of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna according to the present invention when used as a vertical polarization antenna and a horizontal polarization antenna, respectively;

FIG. 11 is a top view of a 3D pattern of a 2X 2 subarray at 61.5 GHz;

FIG. 12 shows values before and after optimizing amplitude differences and phase differences of electromagnetic signals of each path in a V-Band of the 2X 2 subarray provided by the invention;

FIG. 13 is a graph comparing XPD before and after optimizing critical dimensions of a 2X 2 subarray provided by the present invention;

FIG. 14 shows main polarization patterns of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention on E-plane and H-plane of 57 GHz;

FIG. 15 shows main polarization patterns of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention on E-plane and H-plane of 61.5 GHz;

FIG. 16 is a main polarization pattern of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention on the E-plane and the H-plane of 66 GHz;

FIG. 17 shows a cross polarization pattern of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention on the E face and the H face of 57 GHz;

FIG. 18 shows a cross polarization pattern of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention on E face and H face of 61.5 GHz;

FIG. 19 shows a cross polarization pattern of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention on the E face and the H face of 66 GHz;

FIG. 20 is an XPD-frequency plot of an extremely low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention;

FIG. 21 is a diagram of S11 simulation results of an extremely low side lobe millimeter wave gap waveguide slot array antenna;

fig. 22 is a graph of gain-frequency and antenna efficiency-frequency for an ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the present invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the embodiments of the present invention and the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

As shown in fig. 1, the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided in the present embodiment is composed of a ridge gap waveguide feeding network 101, a 90 ° twisted waveguide unit 102, a gap waveguide back cavity coupling network 103 and a radiation unit 104.

As shown in fig. 1 and 2, the ridge gap waveguide feed network 101 includes: metal plate M1, lower metal column, metal ridge, air gap layer A1, metal plate M2; the gap waveguide back cavity coupling network 103 includes: metal plate M2, upper metal column, air gap layer A2, metal plate M3; the heights of the air gap A1 and the air gap layer A2 are lower than one quarter of the mid-frequency air wavelength; the 90 ° twisted waveguide unit 102 is disposed on the metal plate M2, and the radiation unit 104 is disposed on the metal plate M3.

The following describes the structure of each part in detail:

1. ridge gap waveguide feed network

As shown in fig. 3, the gap waveguide feeding network 101 is composed of a rectangular waveguide-ridge gap waveguide power divider 1011, a multi-stage parallel feed ridge gap waveguide T-shaped power divider, and a ridge gap waveguide-rectangular waveguide transition 1013, wherein the multi-stage parallel feed ridge gap waveguide T-shaped power divider 1012 includes ridge gap waveguide T-shaped power dividers arranged in a 5-stage cascade.

As shown in fig. 4, the rectangular waveguide-ridge gap waveguide power divider 1011 includes: the metal rectangular waveguide 1011a, the metal probe 1011b, the metal ridge line 1011c and a plurality of rectangular metal pins 1011d which are arranged around the circumference in a periodic manner. The two metal ridge lines 1011c are symmetrically arranged at the outer side of the long side of the input rectangular waveguide, the end parts of the two metal ridge lines are respectively provided with a metal probe 1011b, and the metal probes 1011b extend into the projection area of the input rectangular waveguide. The rectangular waveguide-ridge gap waveguide power divider 1012 has a two-in-one power distribution function and a two-in-one power synthesis function, wherein the power distribution working principle is as follows: an electromagnetic signal (TE 10 mode) is input from the metal rectangular waveguide 1011a, converted into a quasi-TEM mode by the metal probe 1011b, and then distributed in equal-amplitude and opposite-phase to the air gap A1 between the two metal ridge lines 1011c and the metal plate M2, and output. While power combining can be regarded as the inverse of power allocation, i.e. the signal propagation direction is reversed. The plurality of periodically arranged rectangular metal pins 1011d can form a PMC structure, provide a high impedance surface, and generate a stop band, thereby suppressing leakage of electromagnetic waves, which is equivalent to confining the main energy of electromagnetic waves to propagate in an air gap between the metal ridge line surrounded by the metal pins and the back cavity layer metal plate.

As shown in fig. 5, the ridge gap waveguide T-shaped power divider 1012 includes a shaped T-shaped metal ridge 1012a and an outer surrounding periodically arranged rectangular metal pin 1012e; the special-shaped T-shaped metal ridge 1012a is provided with an inverted trapezoid groove at the T-shaped junction, and the input end of the special-shaped T-shaped metal ridge 1012a is provided with a metal ridge matching section 1012b; the metal ridge matching section 1012b is composed of a trapezoid metal ridge 1012b1 and a rectangular metal ridge 1012b 2; the ridge gap waveguide T-shaped power divider 1012 has a broadband characteristic. The ridge gap waveguide T-type power divider 1012 has a one-to-two power distribution function and a two-to-one power synthesis function, wherein the power distribution working principle is as follows: electromagnetic waves (quasi TEM mode) are input from the air gap A1 between the input metal ridge line 1012c and the metal plate M2, pass through the metal ridge matching section 1012b and the irregular T-shaped metal ridge 1012a in order, and are distributed to the air gap A1 between the two output metal ridge lines 1012d and the metal plate M2 in the same phase with the same amplitude, and are output. While power combining can be considered the inverse of power allocation.

As shown in fig. 6, the ridge gap waveguide-rectangular waveguide transition 1013 includes a T-probe 1013a, a metal ridge line 1013b, a coupling slit 1013c (i.e., a lower rectangular waveguide 1021 of a 90 ° twisted waveguide), and a plurality of rectangular metal pins 1013d arranged periodically around the circumference. The ridge gap waveguide-rectangular waveguide transition 1013 has a function of interconversion of TE10 mode, which propagates in the coupling slit 1013c, with quasi-TEM mode, which propagates in the air gap A1 between the metal ridge line 1013b and the metal plate M2.

The principle of operation of the gap waveguide feed network 101 as a power splitter is as follows: an electromagnetic signal (TE 10 mode) is input from the metal rectangular waveguide 1011a, passes through the metal probe 1011b, is converted into a quasi-TEM mode, and is distributed in equal-amplitude and opposite-phase to the air gap A1 between the two metal ridge lines 1011c and the metal plate M2, and propagates. Then, after passing through the 5-stage ridge space waveguide T-type power divider 1012, the power is equally divided into 64 paths of 8 rows by 8 columns, and the power is output to 64 ridge space waveguide-rectangular waveguide transitions 1013, respectively. After passing through the ridge gap waveguide-rectangular waveguide transition 1013, the electromagnetic signals transmitted to the coupling slot 1013c are again converted back into TE10 mode, but the electromagnetic signals of the odd columns and the even columns are in equal-amplitude inverse relationship.

2.90 DEG twist waveguide unit

As shown in fig. 8, the 90 ° twisted waveguide unit 102 is composed of a lower rectangular waveguide 1021, a polarization converter 1022, and an upper rectangular waveguideRectangular waveguide 1023. The lower rectangular waveguide 1021 is the coupling slot 1013c, which is orthogonal to the upper rectangular waveguide 1023 from the top view. The polarization converter 1022 is shaped like an oblique bow tie, and can realize 90-degree polarization conversion of electromagnetic waves (TE 10 mode) of two orthogonal rectangular waveguides which are connected without changing the propagation direction of the electromagnetic waves. The 90 DEG twisted waveguide units 102 are 2-K in total, and are arranged in a 2-K/2-x-2-K/2 array, and polarization converters 1022 in odd-numbered rows and even-numbered rows are reversely arranged to output TE ₁₀ The polarization directions of the modes are in phase with each other with equal amplitude. The 90 ° twisted waveguide unit is integrally formed by CNC, and as shown in fig. 8 b, the cross section (solid line) of the polarization converter 1022 has an external dimension not exceeding the region where the cross sections of the lower rectangular waveguide 1021 and the upper rectangular waveguide 1023 merge (broken line). The advantage of adopting the integrated processing 90 DEG twist waveguide is that: (1) the problem of difficult layout of the ridge feed network layer is greatly reduced, at least two rectangular metal pins are arranged between the metal ridges, and signal coupling between transmission lines is reduced; (2) the metal layer can be integrally processed by CNC, so that the processing and assembling requirements are reduced while the metal layer is not required to be added.

3. Gap waveguide back cavity coupling network

As shown in FIG. 7, the gap waveguide back cavity coupling network 103 is comprised of 2K gap waveguide resonators 1031 arranged in a2 (K/2) x 2 (K/2) array. The gap waveguide resonant cavity 1031 includes a rectangular air cavity 1031a, a shielded rectangular metal pin 1031b, and an accommodating rectangular metal pin 1031c. The shielding rectangular metal pins 1031b are arranged at equal intervals around the four sides of the rectangular air cavity and enclose two circles in total to form a shape like a Chinese character 'Hui'; wherein, in the horizontal direction, adjacent gap waveguide resonators share 2 columns of shielded rectangular metal pins 1031b; in the vertical direction, each gap waveguide cavity has 2 shielded rectangular metal pins 1031b on either side. For each gap waveguide resonant cavity 1031, there are 2 adjusting rectangular metal pins 1031c symmetrically arranged on both sides of the short side of the rectangular air cavity. The shielding rectangular metal pin 1031b can form a PMC structure, provide a high impedance surface, generate a stop band, and thereby inhibit leakage of electromagnetic waves, which is equivalent to confining main energy of electromagnetic waves to the rectangular air chamber 1031a and the air gap A2 between the metal plate M2 and the metal plate M3 surrounded by the shielding rectangular metal pin 1031b for propagation, while other areas cannot propagate electromagnetic waves.

4. Radiation unit

As shown in fig. 9, the radiation unit 104 is a slit structure penetrating through the metal plate M3, and is sequentially configured from bottom to top into an excitation slit 1041, a matching slit 1042, and a radiation slit 1043, where the size of the matching slit 1042 is smaller than that of the radiation slit 1043. The excitation slit 1041 and the gap waveguide resonant cavity 1031 form a one-to-four power divider or a four-in-one power combiner. In this embodiment, 2 (K+2) radiating elements 104 are arranged in a2 (K/2+1) x 2 (K/2+1) array along the x-axis and y-axis directions, and the row spacing and the column spacing of adjacent radiating elements 104 are equal and are both 0.86 times the medium-frequency air wavelength. The long side of the excitation slit 1041 is parallel to the long side of the rectangular air chamber 1031a (i.e., parallel to the x-axis), while the long sides of the matching slit 1042 and the radiation slit 1043 are at an angle θ ° to the x-axis. By rotating the matching slit 1042 and the radiation slit 1043 by θ °, the cut surfaces of the antenna E-plane and H-plane patterns can be changed, thereby obtaining low side lobes. In the embodiment of the invention, theta is-35, which is equivalent to that the included angle between the E-plane directional diagram and the x-axis is-35 degrees, and the included angle between the H-plane directional diagram and the x-axis is 55 degrees. As shown in fig. 10, the antenna of the present invention can be used as a vertically polarized antenna when it is rotated by plus 35 ° around the z-axis; and when rotated by-55 degrees, the antenna can be used as a horizontally polarized antenna.

Fig. 11 is a top view of a three-dimensional directional diagram of a2×2 subarray at 61.5GHz, and as can be seen from fig. 11, the advantage of selecting a tilt of plus 35 ° or minus 35 ° is that: the tangential planes of the E-plane and the H-plane directional diagrams are changed, and high sidelobes of 0 degrees or 90 degrees and high grating lobes of +/-45 degrees are avoided, so that low sidelobes are obtained. The low sidelobe technical scheme can bring a certain negative influence to standing waves and cross polarization discrimination (XPD), but can be optimized by comprehensively adjusting the structural dimensions of the radiation unit 104 and the gap waveguide back cavity coupling network 103, and the XPD which is superior to the industrial-level requirement (more than or equal to 27 dB) is obtained. The XPD optimization principle is as follows: the electromagnetic signals inputted from the 90 ° twisted waveguide unit are outputted to the corresponding 4 radiation slits 1043 after passing through the quarter power divider formed by the excitation slit 1041 and the gap waveguide resonant cavity 1031 in order, and the matching slits 1042, and the amplitudes and phases of the 4 electromagnetic signals are as equal as possible. For further explanation, let the upper rectangular waveguide in the 90 ° twisted waveguide unit be Port 1, and the upper left, upper right, lower left, and lower right radiation slits be Port 2, port 3, port 4, and Port 5 in order, as shown in fig. 7 (b). When the matching slit and the radiation slit rotate by θ°, in order to obtain a better XPD, the amplitude difference and the phase difference of the 4 paths of electromagnetic signals from Port 1 to Port 2, port 3, port 4 and Port 5 are required to be as small as possible within the working frequency range. In the embodiment provided by the invention, in order to meet the XPD value (more than or equal to 27 dB) of industrial requirements, the amplitude difference and the phase difference between 4 paths of electromagnetic signals are required to be less than or equal to 0.35dB and 4.5 degrees respectively. Fig. 12 (a) and 12 (b) show the amplitude difference of the 4 electromagnetic signals before and after the optimization, the maximum value of the amplitude difference before the optimization is 0.47dB, and the maximum value of the amplitude difference after the optimization is 0.34dB. Fig. 12 (c) and 12 (d) show the phase difference of the 4 electromagnetic signals before and after the optimization, the maximum value of the phase difference before the optimization is 6.26 °, and the maximum value of the phase difference after the optimization is 4.39 °. By optimizing the amplitude and phase differences of the 4-way electromagnetic signals, the XPD of the 2×2 subarrays is greatly improved, as shown in FIG. 13.

The radiation working principle of the ultra-low sidelobe millimeter wave gap waveguide slot array antenna provided by the invention is as follows: an electromagnetic signal (TE 10 mode) is input from the metal rectangular waveguide 1011a, passes through the metal probe 1011b, is converted into a quasi-TEM mode, and is distributed in equal-amplitude and opposite-phase to the air gap A1 between the two metal ridge lines 1011c and the metal plate M2, and propagates. Then after passing through the 5-stage ridge gap waveguide T-shaped power divider 1012, the power is equally divided into 2 (K/2) rows and 2 (K/2) columns which are 2K paths, and the 2K ridge gap waveguide T-shaped power divider is output to 2K ridge gap waveguide-rectangular waveguide transitions 1013 respectively. After passing through the ridge gap waveguide-rectangular waveguide transition 1013, the electromagnetic signals transmitted to the coupling slot 1013c (i.e., the lower rectangular waveguide 1021) are converted back into TE10 mode, but the electromagnetic signals in the odd columns and the even columns are in equal-amplitude inverse relationship. As shown in fig. 6, since the polarization converters 1022 in the odd-numbered columns and the even-numbered columns are in mirror image relationship, the electromagnetic signals in the odd-numbered columns and the even-numbered columns have a constant amplitude and phase relationship when they reach the upper rectangular waveguide 1023 after passing through the polarization converters 1022. Then, the electromagnetic signal is divided into 2 (K/2+1) lines by 2 (k+2) lines in phase after passing through the gap waveguide resonant cavity 1031 with a divide-by-four power distribution function, and is output to 2 (k+2) excitation slits 1041. Subsequently, each of the electromagnetic signals is polarized by the matching slit 1042 and the radiation slit 1043 and radiated into the free space. As can be seen from the array synthesis theory, since the row spacing and the column spacing of the adjacent radiation units 104 are equal and are all 0.86 times of the medium frequency air wavelength, and the electromagnetic signals of the 2 (K/2+1) row and the 2 (K/2+1) column are in the same phase with each other in the same amplitude at the radiation port surface, the 2 (K+2) electromagnetic signals can synthesize a pen beam in the far field. And (3) injection: the antenna also has a receiving function, which is the inverse of the radiation.

In the embodiment provided by the invention, through the adoption of the comprehensive means, XPD with extremely low side lobe, high antenna efficiency, low standing wave and better industrial-grade requirement (more than or equal to 27 dB) can be obtained in the working frequency Band V-Band (57 GHz-66 GHz), and the specific performance is as follows:

as shown in fig. 14, 15 and 16, the E-plane and H-plane main polarization patterns of the embodiments of the present invention at low, medium and high frequency points (i.e., 57GHz, 61.5GHz, 66 GHz) respectively satisfy the Class3B horizontal and vertical main polarization envelope levels of the European Telecommunications Standards Institute (ETSI) EN 302 standard, with a trivial margin, and the first side lobe suppression ratio minimum of the E-plane and H-plane main polarization patterns is higher than 30.2dB.

As shown in fig. 17, 18 and 19, the E-plane and H-plane cross polarization patterns of the embodiments of the present invention at low, medium and high frequency points (i.e., 57GHz, 61.5GHz, 66 GHz) each satisfy the Class3B horizontal and vertical cross polarization envelope levels of the European Telecommunications Standards Institute (ETSI) EN 302 standard, with a trivial margin.

As shown in FIG. 20, after the extremely low side lobe technology provided by the invention is adopted, the axial cross polarization discrimination rate is greater than 30.3dB by optimizing the sizes of the radiation unit 104 and the key structure in the gap waveguide back cavity coupling network 103, and is superior to the industrial-level requirement, namely XPD is more than or equal to 27dB.

As shown in fig. 21, the embodiment of the invention has a wider standing wave bandwidth: s11 < -15.2dB in the working frequency Band V-Band (57 GHz-66 GHz), and the standing wave bandwidth of S11 < -10dB is 23.48% (53.38 GHz-67.58 GHz).

As shown in fig. 22, the embodiment of the present invention has higher gain and antenna efficiency: the antenna efficiency in the working frequency Band V-Band (57 GHz-66 GHz) is higher than 79.2%.

The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope of the present invention.

Claims

1. The low sidelobe millimeter wave gap waveguide slot array antenna is characterized by comprising a metal plate M1, an air gap layer A1, a metal plate M2, an air gap layer A2 and a metal plate M3 which are sequentially arranged from bottom to top;

the upper surface of the metal plate M1 is provided with a lower layer metal column and a metal ridge; the upper surface of the metal plate M2 is provided with an upper layer metal column;

the metal plate M1, the lower metal column, the metal ridge, the air gap layer A1 and the metal plate M2 together form a ridge gap waveguide feed network; the ridge gap waveguide feed network is used for TE to be fed in ₁₀ The mode is converted into quasi-TEM mode, and then is equally divided into 2-K paths, and then is converted into TE ₁₀ The mode is output from output ports arranged in a2 (K/2) x 2 (K/2) array, and TE is output from odd and even rows ₁₀ The direction of the mode polarization is reversed, wherein K is an even number greater than or equal to 2;

the metal plate M2 is provided with 2-K90 DEG twisted waveguide units which are arranged in a 2-K/2-x-2-K/2 array, and the 90 DEG twisted waveguide units in the odd-numbered rows and the 90 DEG twisted waveguide units in the even-numbered rows are reversely arranged for enabling TE fed by a ridge gap waveguide feed network ₁₀ After the polarization directions of the modes are in phase, the modes are fed into a gap waveguide back cavity coupling network;

the metal plate M2, the upper metal column, the air gap layer A2 and the metal plate M3 jointly form a gap waveguide back cavity coupling network; the gap waveguide back cavity coupling network comprises 2-K gap waveguide resonant cavities which are arranged in a2 (K/2) x 2 (K/2) array; TE to be fed into the gap waveguide resonant cavity ₁₀ Mode constant amplitude in-phaseDividing into 4 paths, and then feeding into 4 radiating units respectively;

the metal plate M3 is provided with 2 (K+2) radiating units which are arranged in a2 (K/2+1) x 2 (K/2+1) array and are used for radiating the fed electromagnetic signals into a free space;

the radiation unit is of a slit structure penetrating through the metal plate M3 and consists of an excitation slit, a matching slit and a radiation slit which are sequentially arranged from bottom to top; the excitation slit, the matching slit and the radiation slit are rectangular slits with short edges rounded off; the long sides of the excitation slits are parallel to the long sides of the gap waveguide resonant cavity, the long sides of the matching slits and the radiation slits are arranged at an included angle theta with the long sides of the excitation slits, and the value range of theta is-37 degrees to-33 degrees or 33 degrees to 37 degrees.

2. The low sidelobe millimeter wave gap waveguide slot array antenna of claim 1, wherein the size of the matching slot is smaller than the size of the radiating slot.

3. The low sidelobe millimeter wave gap waveguide slot array antenna of claim 2, wherein the ridge gap waveguide feed network comprises a rectangular waveguide-ridge gap waveguide power divider, a multistage parallel feed ridge gap waveguide T-shaped power divider, and 2 x k ridge gap waveguide-rectangular waveguide transition structures;

4. The low sidelobe millimeter wave gap waveguide slot array antenna of claim 3, wherein the rectangular waveguide-ridge gap waveguide power divider comprises an input rectangular waveguide arranged in the center of the metal plate M1, a lower metal column arranged on the upper surface of the metal plate M1 and a metal ridge; the metal ridge comprises two metal ridge lines which are symmetrically arranged on the outer side of the long side of the input rectangular waveguide; the ends of the two metal ridge lines are respectively provided with a metal probe, and the metal probes extend into the projection area of the input rectangular waveguide; the outer sides of the input rectangular waveguide and the metal ridge are surrounded by lower metal columns which are periodically arranged.

5. The low sidelobe millimeter wave gap waveguide slot array antenna of claim 4, wherein the multistage parallel feed ridge gap waveguide T-shaped power divider is formed by cascading a plurality of ridge gap waveguide T-shaped power dividers; the ridge clearance waveguide T-shaped power divider comprises a special-shaped T-shaped metal ridge and a lower metal column which is arranged in a periodic manner and surrounds the outer side; the special-shaped T-shaped metal ridge is provided with an inverted trapezoid groove at the T-shaped junction, and the input end of the special-shaped T-shaped metal ridge is provided with a metal ridge matching section; by arranging the inverted trapezoid groove and the metal ridge matching section, the ridge gap waveguide T-shaped power divider obtains broadband characteristics.

6. The low sidelobe millimeter wave gap waveguide slot array antenna of claim 5, wherein the cavity structure in the 90 ° twisted waveguide unit comprises an input rectangular waveguide cavity, a 90 ° polarization conversion cavity and an output rectangular waveguide cavity;