Coplanar waveguide-rectangular waveguide horizontal conversion feed structure and waveguide slot antenna

Abstract

The invention discloses a coplanar waveguide-rectangular waveguide horizontal conversion feed structure and a waveguide slot antenna, and belongs to the technical field of radar antennas. The structure mainly comprises a rectangular waveguide conversion section of which one end is connected with a rectangular waveguide and the other end is connected with a coplanar waveguide conversion section, and the rectangular waveguide conversion section is used for converting a dominant mode signal transmitted by the coplanar waveguide into a dominant mode signal transmitted by the rectangular waveguide; and one end of the coplanar waveguide conversion section is connected with the rectangular waveguide conversion section, the other end of the coplanar waveguide conversion section is connected with the coplanar waveguide feeder line, and the coplanar waveguide conversion section is used for performing impedance conversion on the input impedance of the rectangular waveguide conversion section and matching the impedance with the characteristic impedance of the coplanar waveguide feeder line. According to the invention, effective conversion of microwave or millimeter wave signals between the coplanar waveguide and the rectangular waveguide can be realized without vertical transition, and the antenna has the characteristics of simple structure, low profile, simple process and low loss.

Description

Technical Field

[0001] The present application relates to the technical field of radar antennas, and particularly to a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure and a waveguide slot antenna. Background Art

[0002] In recent years, millimeter - wave radars have been increasingly widely and deeply applied in industries such as automobiles, IOT, drones, security, and sports. People have also put forward more and higher requirements for the functions and performances of radars. The antenna is the only device for the radar to communicate in the air interface, and its design quality has a great impact on the overall performance of the millimeter - wave radar.

[0003] A microstrip antenna can be directly connected to the chip pin ends in the radar through a coplanar waveguide (CPW) feeding structure. Although the CPW feeding structure is a commonly used connection method in the design of millimeter - wave radar antennas, it has certain deficiencies.

[0004] Figure 1 is a schematic diagram of a 4Tx / 4Rx millimeter - wave radar microstrip antenna array and a CPW feeder structure in the prior art. As Figure 1 shown, in the 4T x / 4R x millimeter - wave radar microstrip antenna array operating in the frequency band of 76.5 - 81.0 GHz, the R x1 -R x4 and T x1 -T x4 eight antenna elements adopt the form of microstrip comb antennas, which are placed on a substrate with a predetermined thickness at predetermined positions according to the system design requirements. The feeding ends of each microstrip antenna element are connected to the corresponding chip pin ends through eight CPW 1 -CPW 8 feeders with a characteristic impedance of 50Ω. Although the microstrip antenna is well integrated with the radar chip, the loss of the CPW feeder in the working frequency band of this array is relatively large. Figure 2 is the transmission loss diagram of the CPW feeder in a 4Tx / 4Rx millimeter - wave radar with a CPW feeding structure. As Figure 2 shown, the maximum loss of the transmission loss of the eight CPW feeders in the frequency band of 76.5 - 81.0 GHz reaches 1.5 dB, which will greatly reduce the radiation or reception efficiency of the antenna. At the same time, the difference in transmission loss caused by the length difference of each feeder also reaches 1 dB, which will have a greater impact on the amplitude consistency between different transmission channels of the millimeter - wave radar. Summary of the Invention

[0005] Aiming at the problems of large transmission loss of coplanar waveguide and large difference in transmission loss between different transmission channels in the existing technology, this application mainly provides a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure and a waveguide slot antenna.

[0006] To achieve the above object, the first technical solution adopted in this application is: a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure, which includes: a rectangular waveguide transformation section, one end of which is connected to a rectangular waveguide and the other end is connected to a coplanar waveguide transformation section, for converting the main mode signal transmitted by the coplanar waveguide into the main mode signal transmitted by the rectangular waveguide; a coplanar waveguide transformation section, one end of which is connected to the rectangular waveguide transformation section and the other end is connected to a coplanar waveguide feeder, for impedance - transforming the input impedance of the rectangular waveguide transformation section and matching it with the characteristic impedance of the coplanar waveguide feeder.

[0007] Optionally, the rectangular waveguide transformation section is composed of a stepped structure, its first step is connected to the coplanar waveguide transformation section, its second step is a transition conversion part, and its third step is connected to the upper surface of the rectangular waveguide.

[0008] Optionally, the coplanar waveguide transformation section is composed of a single - stub impedance transformer.

[0009] Optionally, the coplanar waveguide feeder is etched on the upper surface of the printed circuit, and metallized vias are arranged within a predetermined range of the coplanar waveguide feeder to connect the upper and lower surfaces of the printed circuit board.

[0010] Optionally, the copper - clad upper surface of the printed circuit board within a predetermined range is used as the bottom surface of the rectangular waveguide.

[0011] Optionally, the pin end of the chip is connected through the coplanar waveguide feeder, and the waveguide slot antenna end is connected through the rectangular waveguide.

[0012] The second technical solution adopted in this application is: a waveguide slot antenna, which includes: a rectangular waveguide slot antenna structure, the rectangular waveguide slot antenna structure is fed by a wave port, and a predetermined number of radiation slots are symmetrically alternated on both sides of the waveguide center line; a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure, which includes a rectangular waveguide transformation section and a coplanar waveguide transformation section, wherein, the rectangular waveguide transformation section, one end of which is connected to a rectangular waveguide and the other end is connected to the coplanar waveguide transformation section, for converting the main mode signal transmitted by the coplanar waveguide into the main mode signal transmitted by the rectangular waveguide; a coplanar waveguide transformation section, one end of which is connected to the rectangular waveguide transformation section and the other end is connected to a coplanar waveguide feeder, for impedance - transforming the input impedance of the rectangular waveguide transformation section and matching it with the characteristic impedance of the coplanar waveguide feeder.

[0013] Optionally, the rectangular waveguide transformation section is composed of a stepped structure, its first step is connected to the coplanar waveguide transformation section, its second step is a transition conversion part, and its third step is connected to the upper surface of the rectangular waveguide.

[0014] Optionally, the coplanar waveguide transformation section is composed of a single stub impedance transformer.

[0015] Optionally, the coplanar waveguide feeder is etched on the upper surface of the printed circuit, and metallized vias are arranged within a predetermined range of the coplanar waveguide feeder to connect the upper and lower surfaces of the printed circuit board.

[0016] Optionally, the copper-clad upper surface of the printed circuit board within a predetermined range is used as the bottom surface of the rectangular waveguide.

[0017] Optionally, the pin ends of the chip are connected through the coplanar waveguide feeder, and the waveguide slot antenna end is connected through the rectangular waveguide.

[0018] The beneficial effects that can be achieved by the technical solution of this application are as follows: The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure of this application can effectively convert microwave or millimeter-wave signals between the coplanar waveguide and the rectangular waveguide without vertical transition, and has the characteristics of simple structure, low profile, simple process, and low loss; the waveguide slot antenna of this application can be directly connected to the pin ends of the radar chip, and has a simple structure, wide bandwidth, and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 is a schematic diagram of a 4Tx / 4Rx millimeter-wave radar microstrip antenna array and a CPW feeder structure in the prior art;

[0021] Figure 2 is a schematic diagram of the transmission loss of the CPW feeder in a 4Tx / 4Rx millimeter-wave radar in the prior art;

[0022] Figure 3 is a schematic diagram of the structure of a coplanar waveguide-rectangular waveguide conversion feeding structure in the prior art;

[0023] Figure 4 is a schematic diagram of the structure of a coplanar waveguide-ridge waveguide conversion feeding structure in the prior art;

[0024] Figure 5 is a schematic diagram of the structure of the coplanar waveguide-rectangular waveguide horizontal conversion feeding structure of this application;

[0025] Figure 6It is a schematic diagram of the electric field distribution of the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure of the present application;

[0026] Figure 7 It is an experimental result diagram of the S-parameters from the chip pin to the waveguide slot antenna end of the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure of the present application;

[0027] Figure 8 It is a schematic diagram of the structure of the waveguide slot antenna of the present application;

[0028] Figure 9 It is a schematic diagram of the structure of the coplanar waveguide - rectangular waveguide horizontal conversion feeding slot antenna unit of the present application;

[0029] Figure 10 It is a schematic diagram of the structure of the rectangular waveguide slot antenna unit fed by a wave port of the present application;

[0030] Figure 11 It is a curve of the standing wave ratio and gain of the rectangular waveguide slot antenna unit fed by a wave port of the present application varying with frequency;

[0031] Figure 12 It is the gain direction diagram of each frequency point of the rectangular waveguide slot antenna unit fed by a wave port of the present application;

[0032] Figure 13 It is a curve of the standing wave ratio and gain of the rectangular waveguide slot antenna unit fed by the coplanar waveguide - rectangular waveguide horizontal conversion feeding varying with frequency transformation of the present application;

[0033] Figure 14 It is the gain direction diagram of each frequency point of the rectangular waveguide slot antenna unit fed by the coplanar waveguide - rectangular waveguide horizontal conversion feeding of the present application;

[0034] Figure 15 It is the transmission loss of each CPW - RTW feeding of the 4Tx / 4Rx millimeter - wave radar of the present application;

[0035] Figure 16 It is a diagram of the standing wave ratio of each CPW - RTW feeding waveguide slot antenna element of the 4Tx / 4Rx millimeter - wave radar of the present application varying with frequency;

[0036] Figure 17 It is a diagram of the gain of each CPW - RTW feeding waveguide slot antenna element of the 4Tx / 4Rx millimeter - wave radar of the present application varying with frequency;

[0037] Figure 18 It is the R of the CPW - RTW feeding waveguide slot antenna of the present application x1 ~R x4 gain direction diagram of the element;

[0038] Figure 19is the T of the CPW-RTW fed waveguide slot antenna of this application x1 ~T x4 gain pattern of the array element.

[0039] Through the above-mentioned drawings, specific embodiments of this application have been shown, and there will be more detailed descriptions hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of this application in any way, but to illustrate the concept of this application to those skilled in the art by referring to specific embodiments. Specific Embodiments

[0040] The following elaborates on the preferred embodiments of this application in conjunction with the drawings, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of this application.

[0041] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, the elements defined by the statement "comprising..." do not exclude the existence of additional identical elements in the process, method, article or device comprising the said elements.

[0042] To solve the technical problems mentioned in the background art, in the prior art, a waveguide antenna form is adopted to replace the microstrip antenna array element in the millimeter-wave radar, and the main feed transmission line between the antenna and the chip is replaced with an air waveguide. By adopting this method, the transmission loss can be reduced and the antenna efficiency can be effectively improved. For example, in the invention patent with the publication number CN115566400A, the antenna efficiency can be effectively improved by using a 3D metallized vehicle-mounted millimeter-wave radar antenna in this application. However, its feeding adopts a rectangular waveguide wave port feeding, which limits its inability to be directly connected and integrated with the current mainstream millimeter-wave radar chips. Therefore, it is impossible to better reduce costs and achieve downward compatibility.

[0043] To balance the advantages of antenna efficiency and easy integration, the solution in the prior art is to introduce a microstrip or coplanar waveguide - metal waveguide conversion feeding structure between the waveguide antenna and the radar chip pin. For example, in the invention patent with the publication number CN111786097A, a microstrip - ridge waveguide conversion feeding structure is designed, which connects the ridge waveguide antenna and the chip pin. However, the processing accuracy requirement of the ridge waveguide is higher than that of the rectangular waveguide, and the loss of the microstrip feeder is greater than that of the CPW feeder. Another example is that the invention patents with the publication numbers CN114039183B and CN114639954B respectively disclose the conversion feeding structures of coplanar waveguide - rectangular waveguide and coplanar waveguide - ridge waveguide, and their structures are as Figure 3 and Figure 4 shown. However, the disclosed conversion feeding structures are all vertical structures. Therefore, they have a high profile and a complex conversion structure, and thus cannot be directly transplanted into the mature radar products such as Figure 1 shown.

[0044] Therefore, in the prior art, if a microstrip antenna is used as an array element, there are problems of large loss and low efficiency. Moreover, the disclosed coplanar waveguide - rectangular or ridge waveguide conversion feeding structures for connecting the metal waveguide antenna and the radar chip are all vertical transition conversions. Such conversion structures are complex and have a high profile, and cannot be directly transplanted into the mature millimeter - wave radar system. In addition, the ridge waveguide of the disclosed microstrip - ridge waveguide horizontal conversion feeding structure has high processing accuracy requirements, which is not conducive to low - cost mass production. And there are problems of large radiation effect and large insertion loss when the microstrip line transmits signals in the millimeter - wave band.

[0045] To solve the above problems, the present application designs a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure. This structure can effectively convert microwave / millimeter - wave signals between the coplanar waveguide and the rectangular waveguide without using vertical transition, and has the characteristics of simple structure, low profile, wide bandwidth and low loss. At the same time, by using the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure to connect the waveguide slot antenna and the radar chip pin, it has the advantages of wide frequency band and high efficiency of the antenna. And by replacing the microstrip antenna with a coplanar waveguide - rectangular waveguide horizontal conversion feeding waveguide slot antenna, it can be directly compatible with the existing millimeter - wave radar, and enhance the performance of the radar on the premise of avoiding re - designing the radar system.

[0046] Next, specific embodiments will be used to elaborate in detail on the technical solution of the present application and how the technical solution of the present application solves the above - mentioned technical problems. The specific embodiments described below can be combined with each other to form new embodiments. For the same or similar ideas or processes described in one embodiment, they may not be repeated in some other embodiments. The embodiments of the present application will be described below with reference to the accompanying drawings.

[0047] Figure 5An embodiment of a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure of the present application is shown.

[0048] Figure 5 The shown coplanar waveguide - rectangular waveguide horizontal conversion feeding structure includes: a rectangular waveguide transformation section 101, one end of which is connected to a rectangular waveguide and the other end is connected to a coplanar waveguide transformation section, and is used for converting the main mode signal transmitted by the coplanar waveguide into the main mode signal transmitted by the rectangular waveguide;

[0049] A coplanar waveguide transformation section 102, one end of which is connected to the rectangular waveguide transformation section and the other end is connected to a coplanar waveguide feeder, and is used for impedance - transforming the input impedance of the rectangular waveguide transformation section and matching it with the characteristic impedance of the coplanar waveguide feeder.

[0050] This specific embodiment can effectively convert microwave or millimeter - wave signals between a coplanar waveguide and a rectangular waveguide without vertical transition, and has the characteristics of simple structure, low profile, simple process and low loss. Moreover, this structure can connect a metal waveguide slot antenna and a chip pin through simple transformation.

[0051] Specifically, as Figure 5 shown, a CPW (coplanar waveguide) feeder is etched on the upper surface of a PCB dielectric board with copper - covered upper and lower surfaces, and metallized vias are regularly arranged within a predetermined range on the left and right of the CPW feeder. At a predetermined position at one end of the waveguide feeder far from the chip connection pin, the copper - covered upper surface of the printed circuit board within the predetermined range is used as the bottom surface of the rectangular waveguide, and a rectangular waveguide tube is arranged thereon. And a coplanar waveguide - rectangular waveguide horizontal conversion feeding structure is arranged between the coplanar waveguide and the rectangular waveguide. In practical applications, the chip pin is connected through the coplanar waveguide feeder, and the waveguide slot antenna is connected through the feeder of the rectangular waveguide, thereby realizing signal transmission and conversion more efficiently.

[0052] For example, Rogers RO3003 with a thickness of 0.127 mm is used as the PCB dielectric board. Copper is plated on both the upper and lower surfaces of the PCB dielectric board, and a CPW feeder is etched on the upper surface of the PCB. Metallized vias are arranged in a uniformly distributed manner within a predetermined range of the coplanar waveguide feeder to connect the upper and lower surfaces of the PCB, thereby improving the CPW transmission performance. The inner cross-sectional dimensions of the rectangular waveguide adopt the internationally standard WR-10 waveguide, with the widths of its broad side and narrow side being 2.54 mm and 1.27 mm respectively. Therefore, the copper plating on the upper surface at a predetermined position on the PCB dielectric board with a length of 2.54 mm and a width of 1.27 mm is used as the bottom surface of the broad side of the rectangular waveguide. Together with the bottom surface of the broad side of a predetermined size and position, the top surface of the broad side of the rectangular waveguide of a predetermined size, and the two narrow side surfaces, a rectangular waveguide is formed. Since the copper plating on the upper surface of the PCB dielectric board is used as the bottom surface of the broad side of the rectangular waveguide, in actual processing, the metal RTW (rectangular waveguide) is actually an open structure without a bottom surface of the broad side, which is easier to fabricate than a conventional closed rectangular waveguide.

[0053] The coplanar waveguide - rectangular waveguide horizontal conversion feeding structure consists of a rectangular waveguide transformation section 101 and a coplanar waveguide transformation section 102. Among them, for the rectangular waveguide transformation section 101, one end is connected to the rectangular waveguide, and the other end is connected to the coplanar waveguide transformation section, which is used to convert the main mode signal transmitted by the coplanar waveguide into the main mode signal transmitted by the rectangular waveguide; for the coplanar waveguide transformation section 102, one end is connected to the rectangular waveguide transformation section, and the other end is connected to the coplanar waveguide feeder, which is used to match the characteristic impedance of the coplanar waveguide feeder after impedance transformation of the input impedance of the rectangular waveguide transformation section. And the rectangular waveguide transformation section is composed of a stepped structure, its first step is connected to the coplanar waveguide transformation section, its second step is the transition conversion part, its third step is connected to the upper surface of the rectangular waveguide, while the coplanar waveguide transformation section is composed of a single stub impedance transformer.

[0054] For example, the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure connects the CPW feeder and the rectangular waveguide, which is divided into a CPW transformation section and an RTW transformation section. Among them, the RTW transformation section is composed of three stepped structures. The RTW transformation section can effectively convert the main mode (TEM mode) transmitted by the CPW and the main mode (TE 10 mode) transmitted by the RTW; the CPW transformation section is composed of a single stub impedance transformer, which can match the characteristic impedance of the CPW feeder after impedance transformation of the input impedance of the RTW transformation section, and this conversion can reduce the loss of the conversion feeding structure. Preferably, the length of the CPW feeder is set to 6 mm, the length of the rectangular waveguide is 8 mm, the lengths of the RTW transformation sections are all 3.5 mm, and the length of the CPW transformation section is 0.9 mm.

[0055] The performance parameters of the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure of the present application will be specifically described below:

[0056] Figure 6 6 shows the electric field distribution of the coplanar waveguide-rectangular waveguide horizontal conversion feeding structure of the present application. From FIG. 6, it can be seen that the signal fed into the chip pin is transmitted to the right in the TEM mode on the CPW feeder. After passing through the coplanar waveguide-rectangular waveguide horizontal conversion feeding structure of the present application, its electromagnetic wave transmission mode quickly changes to TE 10 Therefore, the coplanar waveguide-rectangular waveguide horizontal conversion feeding structure of the present application is a practical structure that can realize the effective conversion of microwave or millimeter wave signals between the coplanar waveguide and the rectangular waveguide without vertical transition.

[0057] The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure with the above specific parameters was tested and the following results were obtained: Figure 7 The experimental results of S parameters between the chip pin and the waveguide slot antenna end of the coplanar waveguide-rectangular waveguide horizontal transition feeding structure are shown. Figure 7 According to the S parameters between the CPW feeding port 1 connected to the chip pin and the RTW feeding port 2 connected to the waveguide slot antenna, the reflection coefficient S of the above two ports in the frequency band of 76.5 to 81 GHz can be obtained. 11 and S 22 The above parameters show that the coplanar waveguide-rectangular waveguide horizontal conversion feeding structure of the present application has the advantages of broadband and low loss, and the cross-section of the entire conversion structure of the present application is the narrow side width of the rectangular waveguide, that is, it has the advantage of low cross-section.

[0058] Figure 8 A specific implementation of a waveguide slot antenna of the present application is shown.

[0059] The waveguide slot antenna mainly comprises: a rectangular waveguide slot antenna unit structure 201, in which a predetermined number of radiation slots in the antenna unit are symmetrically alternately arranged on both sides of the waveguide centerline;

[0060] Coplanar waveguide - rectangular waveguide horizontal conversion feeding structure 202, which includes a rectangular waveguide transformation section 101 and a coplanar waveguide transformation section 102. Among them, for the rectangular waveguide transformation section, one end is connected to the rectangular waveguide, and the other end is connected to the coplanar waveguide transformation section, which is used to convert the main mode signal transmitted by the coplanar waveguide into the main mode signal transmitted by the rectangular waveguide; for the coplanar waveguide transformation section, one end is connected to the rectangular waveguide transformation section, and the other end is connected to the coplanar waveguide feeder, which is used to match the characteristic impedance of the coplanar waveguide feeder after impedance transformation of the input impedance of the rectangular waveguide transformation section. In this specific embodiment, the coplanar waveguide - rectangular waveguide horizontal conversion feeding waveguide slot antenna is directly connected to the radar chip pin, with a simple structure, wide bandwidth, high efficiency, and can be directly compatible with the existing millimeter - wave radar by directly replacing the currently used microstrip antenna with the coplanar waveguide - rectangular waveguide horizontal conversion feeding waveguide slot antenna, without the need to modify the topology of the radar system and redesign the system.

[0061] Specifically, Figure 8 shows a specific implementation manner of a waveguide slot antenna of the present application. In Figure 8 shows the connection method of connecting the antenna element and the radar chip through the connection method of the present application. Figure 9 is Figure 8 the specific structural schematic diagram of CPW - RTW1 to CPW - RTW8 in Figure 9 As shown, the rectangular waveguide slot antenna structure 201 and the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure 202. Figure 10 is the structural schematic diagram of the rectangular waveguide slot antenna unit of the present application, which corresponds to Figure 9 the rectangular waveguide slot antenna structure 201 in

[0062] As Figure 10 shown, the waveguide slot antenna structure 201 is designed based on the standard rectangular waveguide WR - 10. The antenna feeding of the waveguide slot antenna structure 201 uses wave - port excitation, and the five radiation slots of this structure are symmetrically and alternately distributed on both sides of the waveguide center line. For Figure 10 the waveguide slot antenna structure 201 shown, the test results of Figure 11 and Figure 12 are obtained. Among them, Figure 11 is the standing - wave ratio and gain versus frequency curve of the wave - port - fed rectangular waveguide slot antenna unit of the present application, Figure 12 is the gain direction pattern of each frequency point of the wave - port - fed rectangular waveguide slot antenna unit of the present application. As Figure 11 shown, the in - band standing - wave ratio of the rectangular waveguide slot antenna unit of the present application is less than 1.5 and the gain is greater than 13.5 dBi at 76.5 - 81 GHz, Figure 12is the gain pattern of the rectangular waveguide slot antenna unit of the present application at typical frequency points within the frequency band of 76.5 - 81 GHz. It can be obtained from Figure 12 that the half-power beamwidth of the rectangular waveguide slot antenna unit of the present application in the azimuth plane is ±40°, and the sidelobe in the elevation plane is less than -16.4 dB. Therefore, the rectangular waveguide slot antenna structure of the present application has good signal transmission performance.

[0063] Figure 9 is the schematic structural diagram of the coplanar waveguide - rectangular waveguide horizontal conversion feed slot antenna unit of the present application. As Figure 9 shown, the rectangular waveguide slot antenna unit is connected to the radar chip pin by using the coplanar waveguide - rectangular waveguide horizontal conversion feed structure 202, and the connection between the two can be realized in a convenient and fast way. In Figure 9 , both the coplanar waveguide - rectangular waveguide horizontal conversion feed structure and the rectangular waveguide antenna unit adopt the international standard WR-10 rectangular waveguide. Therefore, when producing and designing, only the PCB board of the coplanar waveguide - rectangular waveguide horizontal conversion feed structure needs to be extended along the direction of the waveguide slot antenna by a sufficient length as the lower bottom surface of the wide side of the rectangular waveguide to meet the design requirements of the present application. Therefore, the present application can be realized in a simple and easy-to-produce way. For Figure 9 the structure shown in the test results of Figure 13 and Figure 14 are obtained. Among them, Figure 13 is the curve of the standing wave ratio and gain of the coplanar waveguide - rectangular waveguide horizontal conversion feed rectangular waveguide slot antenna unit of the present application varying with frequency, Figure 14 is the gain pattern of the coplanar waveguide - rectangular waveguide horizontal conversion feed rectangular waveguide slot antenna unit of the present application at each frequency point. According to Figure 13 and Figure 14 , it can be seen that the gain of the coplanar waveguide - rectangular waveguide fed antenna is greater than 13.3 dBi. This value only drops by 0.2 dB compared with the gain of the wave port fed antenna unit, its azimuth half-power beamwidth is still ±40°, and the elevation sidelobe is less than -16.1 dB. Therefore, it can be seen that the working performance of the coplanar waveguide - rectangular waveguide fed waveguide slot antenna unit has very little difference from that when fed by the wave port, which is attributed to the characteristics of broadband width and low transmission loss of the coplanar waveguide - rectangular waveguide horizontal conversion feed structure of the present application. The above results show that by using the coplanar waveguide - rectangular waveguide horizontal conversion feed structure of the present application, the waveguide slot antenna can be very simply connected to the chip pin with almost no impact on the performance of the antenna itself.

[0064] As Figure 8 shown is Figure 1The CPW-fed 4Tx / 4Rx millimeter-wave radar microstrip antenna array shown is replaced with the model of the coplanar waveguide-rectangular waveguide-fed waveguide slot antenna array designed in this application. In Figure 8 the antenna model shown, only the antenna is replaced, and the array layout and the position of the chip remain unchanged. Figure 8 According to R x1 ~R x4 and T x1 ~T x4 The actual positions of the eight antenna elements extend the length of the rectangular waveguide, but the coplanar waveguide-rectangular waveguide feeding structure and the structure of the rectangular waveguide slot antenna element itself remain unchanged. According to Figure 8 the model of the coplanar waveguide-rectangular waveguide-fed waveguide slot antenna array shown for performance testing, the test results shown in Figure 15 , Figure 16 , Figure 17 , Figure 18 and Figure 19 are obtained.

[0065] As shown in Figure 15 is the curve of the transmission loss of the eight transmission channels of CPW-RTW 1 ~CPW-RTW 8 changing with frequency. According to Figure 15 it is obtained that in the frequency band of 76.5 - 81.0 GHz, the maximum transmission loss of the above eight CPW-RTW transmission channels is only 0.9 dB. Compared with the CPW feeder of the prior art, its transmission loss is reduced by 0.6 dB, and the transmission loss difference between the eight CPW-RTW transmission channels is only 0.3 dB. Therefore, the coplanar waveguide-rectangular waveguide-fed waveguide slot antenna of this application can greatly improve the amplitude consistency of the transmission signals of each channel, and thus can improve the performance of the radar system. Figure 16 is the curve of the standing wave ratio of each CPW-RTW-fed waveguide slot antenna element of the 4Tx / 4Rx millimeter-wave radar changing with frequency. According to Figure 16 it can be obtained that in the frequency band of 76.5 - 81 GHz, the standing wave ratio of each CPW-RTW-fed waveguide slot antenna element is less than 2. Figure 17 is the curve of the gain of each CPW-RTW-fed waveguide slot antenna element of the 4Tx / 4Rx millimeter-wave radar changing with frequency. Figure 18 and Figure 19 are the gain patterns of the 4Tx / 4Rx antenna elements at typical frequency points.

[0066] From Figure 17 it can be seen that the gain of the radar antenna array of this application is greater than 11.5 dBi. Compared with Figure 12Compared with the single CPW-RTW fed waveguide slot antenna element shown, its gain is reduced by 1.8 dB. Combining Figure 15 the transmission loss of the CPW-RTW antenna array of Figure 18 is not greater than 0.9 dB for analysis, it is obtained that the gain of the radar array antenna is 0.9 dB lower than the expected value. Observing Figure 19 and x1 ~ x4 and x1 ~ x4 it is obtained that the azimuth half-power beamwidth of these eight antenna array elements reaches ±60°. This is because the layout of the antenna array surface affects the gain pattern of the antenna array elements, expanding the azimuth beamwidth and sacrificing the peak gain of the main beam, but this is in line with antenna theory. In addition, through Figure 17 it can be obtained that the gain difference of each antenna array element within the frequency band of 76.5 - 81 GHz is ≤0.5 dB, and there is a very good channel consistency characteristic between its channels.

[0067] In a specific embodiment of the present application, the rectangular waveguide transformation section is composed of a stepped structure. Its first step is connected to the coplanar waveguide transformation section, its second step is the transition conversion part, and its third step is connected to the upper surface of the rectangular waveguide.

[0068] In a specific embodiment of the present application, the coplanar waveguide transformation section is composed of a single stub impedance transformer.

[0069] In a specific embodiment of the present application, the coplanar waveguide feeder is etched on the upper surface of the printed circuit, and metallized vias are arranged within a predetermined range of the coplanar waveguide feeder to connect the upper and lower surfaces of the printed circuit board.

[0070] In a specific embodiment of the present application, the copper-clad upper surface of the printed circuit board within a predetermined range is used as the bottom surface of the rectangular waveguide.

[0071] In a specific embodiment of the present application, the pin end of the chip is connected through the coplanar waveguide feeder, and the waveguide slot antenna end is connected through the rectangular waveguide.

[0072] The waveguide slot antenna provided by the present application can be used to implement the coplanar waveguide - rectangular waveguide horizontal conversion feeding structure described in any of the above embodiments. Its implementation principle and technical effects are similar and will not be elaborated here.

[0073] The above are only the embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structural transformation made using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present application by the same token.

Claims

1. A coplanar waveguide-rectangular waveguide horizontal conversion feeding structure, characterized in that: include: A rectangular waveguide conversion section, one end of which is connected to the rectangular waveguide and the other end of which is connected to the coplanar waveguide conversion section, for converting a main mode signal transmitted by the coplanar waveguide into a main mode signal transmitted by the rectangular waveguide; A coplanar waveguide transformation segment, one end of which is connected to the rectangular waveguide transformation segment, and the other end of which is connected to the coplanar waveguide feeder, is used to match the input impedance of the rectangular waveguide transformation segment with the characteristic impedance of the coplanar waveguide feeder after impedance transformation.

2. The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure according to claim 1, characterized in that: The rectangular waveguide transformation section is composed of a stepped structure, wherein the first step is connected to the coplanar waveguide transformation section, the second step is a transition conversion portion, and the third step is connected to the upper surface of the rectangular waveguide.

3. The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure according to claim 1, characterized in that: The coplanar waveguide transformation section is composed of a single-branch impedance transformer.

4. The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure according to claim 1, characterized in that: The coplanar waveguide feed line is etched on the upper surface of the printed circuit, and metallized through holes are arranged within a predetermined range of the coplanar waveguide feed line to connect the upper and lower surfaces of the printed circuit board.

5. The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure according to claim 1, characterized in that: The copper-clad upper surface of the printed circuit board within a predetermined range is used as the bottom surface of the rectangular waveguide.

6. The coplanar waveguide-rectangular waveguide horizontal conversion feeding structure according to claim 1, characterized in that: The pin end of the chip is connected through a coplanar waveguide feeder, and the waveguide slot antenna end is connected through a rectangular waveguide.

7. A waveguide slot antenna, characterized in that: include: A rectangular waveguide slot antenna structure, wherein the rectangular waveguide slot antenna structure is fed by a wave port, and a predetermined number of radiation slots are symmetrically alternated on both sides of the waveguide centerline; A coplanar waveguide-rectangular waveguide horizontal conversion feeding structure comprises a rectangular waveguide transformation section and a coplanar waveguide transformation section, wherein: The rectangular waveguide conversion section has one end connected to the rectangular waveguide and the other end connected to the coplanar waveguide conversion section, and is used to convert the main mode signal transmitted by the coplanar waveguide into the main mode signal transmitted by the rectangular waveguide; The coplanar waveguide transformation section has one end connected to the rectangular waveguide transformation section and the other end connected to the coplanar waveguide feeder, and is used to match the input impedance of the rectangular waveguide transformation section with the characteristic impedance of the coplanar waveguide feeder after impedance transformation.

8. The waveguide slot antenna according to claim 7, characterized in that: The rectangular waveguide transformation section is composed of a stepped structure, wherein the first step is connected to the coplanar waveguide transformation section, the second step is a transition conversion portion, and the third step is connected to the upper surface of the rectangular waveguide.

9. The waveguide slot antenna according to claim 7, characterized in that: The coplanar waveguide transformation section is composed of a single-branch impedance transformer.

10. The waveguide slot antenna according to claim 7, characterized in that: The pin end of the chip is connected through a coplanar waveguide feeder, and the waveguide slot antenna end is connected through a rectangular waveguide.

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