Transition structure from rectangular waveguide to strip line waveguide

Abstract

The invention relates to the field of communication radars, and discloses a transition structure from a rectangular waveguide to a strip line waveguide, which comprises a vertical rectangular waveguide working in a TE mode and a horizontal strip line waveguide working in a TEM mode, and realizes the conversion of the two modes through a specific electromagnetic coupling mode. The horizontal strip line waveguide is of a three-layer metal sheet structure and is fixed to the vertical rectangular waveguide through screws or in a hot melting mode. The transition structure is divided into a direct type and a fan-out type, the electromagnetic coupling structure comprises wide-side coupling and narrow-side coupling, and the narrow-side coupling has a single-feeder flag type and a double-feeder differential type. According to the invention, the blank of switching from the rectangular waveguide to the strip line waveguide in the prior art is filled, the design of the vehicle-mounted radar antenna is simplified, the cost is reduced, and the consistency of mass production is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication radars, in particular to a transition structure from a rectangular waveguide to a stripline waveguide. BACKGROUND

[0002] In the field of modern communication and radar technology, especially in the vehicle-mounted millimeter wave radar system, the antenna is the core component of electromagnetic wave transceiver, and its performance directly determines the detection accuracy, range resolution and anti-interference ability of the radar. With the rapid development of automatic driving technology, the vehicle-mounted millimeter wave radar puts forward more and more strict requirements for the miniaturization, low profile, high performance and low cost mass production of the antenna. The waveguide antenna gradually shows the trend of replacing the traditional microstrip antenna in the vehicle-mounted radar field due to its low loss, high power capacity and good directivity, and becomes one of the mainstream antenna technologies in the future. However, in the signal transmission link of the radar system, the signal switching between the chip and the antenna is a key link, and the mode matching and efficient transition between different types of waveguides directly affect the signal transmission efficiency of the whole system.

[0003] In the existing vehicle-mounted radar system, the waveguide antenna mostly adopts a single rectangular waveguide structure, and its working mode is transverse electric wave (TE mode). Although the rectangular waveguide has the characteristics of stable structure and low transmission loss, it is limited by the inherent characteristics of the TE mode, and there is a lower limit of the main mode cutoff frequency, which leads to the difficulty of further reducing the waveguide cross-sectional size, and cannot meet the urgent needs of low profile and miniaturization of vehicle-mounted radar. At the same time, the processing technology of rectangular waveguide is complex, especially in a multi-channel radar system, the densely arranged rectangular waveguides are prone to structural interference, and the manufacturing cost is high, and the consistency of mass production is difficult to guarantee.

[0004] The stripline waveguide, as a transmission structure working in transverse electromagnetic wave (TEM mode), does not have the limitation of cutoff frequency, can realize efficient signal transmission in a small cross-sectional size, and can significantly compress the channel volume to meet the design requirements of miniaturization of radar system. In addition, the stripline waveguide adopts a layered metal structure, and the processing technology is relatively simple, which is conducive to reducing production cost and improving mass production consistency. However, in the existing technology, there is a technical gap in the efficient transition structure between the rectangular waveguide (TE mode) and the stripline waveguide (TEM mode): there is no coupling mechanism that can realize stable conversion between two different modes (TE mode and TEM mode), which cannot guarantee low loss and good matching of the signal in the switching process; no compact transition structure design scheme is formed for the vehicle-mounted radar scene, which is difficult to adapt to the limited installation space inside the radar system.

[0005] There is no feasible technical scheme for the mechanical fixing method of the transition structure, the processing technology and the specific implementation form of the stripline waveguide, which leads to obstacles in the practical engineering application of the rectangular waveguide and the stripline waveguide.

[0006] Therefore, aiming at the demand of communication radar field such as vehicle-mounted millimeter wave radar, a structure capable of realizing efficient transition from rectangular waveguide to strip line waveguide is developed, which fills the gap of the prior art and becomes a technical problem to be solved in the field. SUMMARY

[0007] In view of the deficiencies of the prior art, the present application provides a transition structure from rectangular waveguide to strip line waveguide, which solves the above problems.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a transition structure from rectangular waveguide to strip line waveguide, including a vertical rectangular waveguide working in TE mode and a horizontal strip line waveguide working in TEM mode, the strip line is used to design the TEM mode waveguide channel, the main mode of operation is TEM mode, there is no lower limit of the main mode cutoff frequency of rectangular waveguide, which can greatly compress the channel size without affecting normal electromagnetic wave transmission, wherein the horizontal strip line waveguide is composed of three metal sheets, and the strip line waveguide is realized by sheet metal;

[0009] The transition structure is used to realize the transition from chip rectangular waveguide port to sheet metal strip line waveguide, including direct transition structure and fan-out transition structure;

[0010] The electromagnetic coupling structure is arranged in the horizontal strip line waveguide, and the vertical rectangular waveguide and the horizontal strip line waveguide realize the conversion from TE mode to TEM mode through electromagnetic coupling.

[0011] Preferably, the cross-sectional size of the horizontal strip line waveguide is less than 1mm*1mm, and the cross-sectional size of the signal layer of the strip line is less than 0.5mm(W)*0.3mm(H);

[0012] When applied to 77G radar, a preferred size combination is that the cross-sectional size of the strip line waveguide is 1mm(W)*0.65mm(H), and the cross-sectional size of the signal layer is 0.37mm(W)*0.15mm(H), which is a better transmission matching state.

[0013] Preferably, the first layer of the horizontal strip line waveguide is an air layer above the metal signal layer and an outer metal ground layer, referred to as the top layer;

[0014] The second layer is the signal layer itself, referred to as the middle layer;

[0015] The third layer is the air below the signal layer and the outer metal ground layer, referred to as the bottom layer;

[0016] The thickness of the three metal sheets ranges from 0.1mm to 0.5mm;

[0017] The three layers are fastened together with screws, and glue can be applied between each layer before the screws are tightened.

[0018] Preferably, the direct transition structure is a vertical transition electromagnetic coupling method between the rectangular waveguide port of the chip output and the stripline waveguide transition structure. The rectangular waveguide port of the chip and the port of the stripline waveguide are vertically aligned, and the electromagnetic coupling is achieved through the middle layer of the stripline, i.e., the metal signal layer.

[0019] The fan-out transition structure is based on the direct transition structure, with the vertical rectangular waveguide channel continuing to fan outward. After a certain distance, it is vertically switched and aligned with the port of the stripline waveguide. Electromagnetic coupling is achieved through the middle layer of the stripline, i.e., the metal signal layer.

[0020] Preferably, the electromagnetic coupling structure is divided into two types: wide-side coupling and narrow-side coupling;

[0021] The wide-side coupling refers to the metal signal layer of the stripline waveguide extending into the wide side of the rectangular waveguide to achieve electromagnetic coupling.

[0022] The narrow-side coupling refers to the electromagnetic coupling achieved by extending the metallic signal layer of the stripline waveguide along the narrow side of the rectangular waveguide.

[0023] Preferably, the narrow-side coupled electromagnetic coupling structure includes a single-feed flag type, wherein the end electromagnetic coupling structure of the single-feed flag type is square, and a signal feed line is connected at the corner of the patch.

[0024] Preferably, the narrow-side coupled electromagnetic coupling structure further includes a dual-feed differential type, wherein the dual-feed differential type uses dual feeders to feed a square metal block with its end inserted into a rectangular waveguide. One feeder is a straight line, and the other is a meandering line to achieve a 180-degree phase difference.

[0025] Preferably, the vertical rectangular waveguide and the horizontal stripline waveguide are fixed by screw fastening, with corresponding screw holes provided on the vertical rectangular waveguide, and the horizontal stripline waveguide and the vertical rectangular waveguide are fixed by screws.

[0026] Preferably, the fixing method of the vertical rectangular waveguide and the horizontal stripline waveguide includes a thermoforming method. The vertical rectangular waveguide is disposed on one side of the horizontal stripline waveguide, and several thermoforming pillars are disposed on the end face of the vertical rectangular waveguide. After the horizontal stripline waveguide and the vertical rectangular waveguide are assembled, the thermoforming pillars are melted by thermoforming to form a mushroom head, thereby fixing the two together.

[0027] Preferably, the vertical rectangular waveguide is processed in two ways: plastic injection molding followed by surface metallization and CNC machining of metal blocks.

[0028] Compared with the prior art, the present invention provides a transition structure from a rectangular waveguide to a stripline waveguide, which has the following advantages:

[0029] 1. The transition structure from rectangular waveguide to stripline waveguide addresses the common problem that existing solutions for vehicle waveguide antennas use plastic-metallized rectangular waveguide antennas, with both the vertical and horizontal waveguides operating in TE mode, thus eliminating the need for transitions. In contrast, the horizontal waveguide of this invention uses a stripline waveguide operating in TEM mode, providing a transition structure from the TE mode of a rectangular waveguide to the TEM mode of a stripline waveguide, filling a technological gap.

[0030] 2. The transition structure from rectangular waveguide to stripline waveguide adopts a transition structure from the TE mode of rectangular waveguide to the TEM mode of stripline waveguide, realizing the stripline waveguide channel, simplifying the design of vehicle radar antenna, and achieving high performance of waveguide antenna. It solves the low profile problem of existing waveguide technology solutions, significantly reduces design and manufacturing costs, reduces processes, and improves mass production consistency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram showing the cavity and physical object of the 0-degree transition structure on the wide side of the present invention;

[0032] Figure 2 This is a schematic diagram showing the cavity and physical object of the 90-degree transition structure on the wide side of the present invention;

[0033] Figure 3 This is a schematic diagram of the electric field of the wide-side 0-degree transition structure of the present invention;

[0034] Figure 4 This is a schematic diagram showing the cavity and physical object of the single-feeder flag-shaped narrow-side transition structure of the present invention;

[0035] Figure 5 This is a schematic diagram showing the cavity and physical object of the dual-feed differential narrow-side transition structure of the present invention;

[0036] Figure 6 This is a top view schematic diagram of the cavity of the dual-feed differential narrow-side transition structure of the present invention;

[0037] Figure 7 This is a schematic diagram showing the cavity and physical object of the fan-out transition structure of the present invention;

[0038] Figure 8 This is a schematic diagram of the metal stripline waveguide structure of the present invention;

[0039] Figure 9 This is a schematic diagram of the S-parameters of the wide-side 0-degree waveguide transition structure of the present invention;

[0040] Figure 10This is a schematic diagram of the S-parameters of the narrow-side waveguide transition structure 1 of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figures 1-10 The transition structure from rectangular waveguide to stripline waveguide includes a vertical rectangular waveguide operating in TE mode and a horizontal stripline waveguide operating in TEM mode. A stripline waveguide is used to design the TEM mode waveguide channel, and its primary operating mode is TEM mode. It avoids the drawback of the lower cutoff frequency of the dominant mode in rectangular waveguides, allowing for significant reduction in channel size without affecting normal electromagnetic wave transmission. The horizontal stripline waveguide consists of three layers of metal sheets, utilizing sheet metal to realize the stripline waveguide. The transition structure is used to connect the chip's rectangular waveguide port to the metal sheet stripline waveguide, including a direct transition structure and a fan-out transition structure. An electromagnetic coupling structure is installed within the horizontal stripline waveguide, and the vertical rectangular waveguide and horizontal stripline waveguide achieve the conversion from TE mode to TEM mode through electromagnetic coupling.

[0043] like Figure 8 As shown, the horizontal strip waveguide of the present invention adopts a three-layer sheet metal sheet structure, and the thickness of the three-layer sheet metal sheet ranges from 0.1mm to 0.5mm. The specific thickness is determined according to the performance requirements of the actual product.

[0044] The first layer is the top layer, consisting of an air layer above the metal signal layer and an outer metal ground layer;

[0045] The second layer is the intermediate layer, namely the signal layer itself;

[0046] The third layer is the bottom layer, consisting of an air layer below the signal layer and an outer metal ground layer.

[0047] The three metal sheets are fastened together with screws. After assembly, there will be air gaps between the three metal layers. These gaps are not specifically required and do not affect product performance. In some relatively large-sized applications, to ensure a tight fit, adhesive can be applied between each layer before tightening the screws to ensure good adhesion between the layers.

[0048] The cross-sectional dimensions of the horizontal stripline waveguide are less than 1mm*1mm, with the signal layer cross-sectional dimensions of the stripline being less than 0.5mm(W)*0.3mm(H). When applied to the 77G radar, a preferred size combination is a stripline waveguide cross-sectional dimension of 1mm(W)*0.65mm(H), in which case the signal layer cross-sectional dimensions are 0.37mm(W)*0.15mm(H), which represents a better transmission matching state.

[0049] There are two methods for fabricating vertical rectangular waveguides:

[0050] In lightweight design, plastic injection molding is used followed by surface metallization treatment;

[0051] In general design, this is achieved through CNC machining of metal blocks.

[0052] The direct transition structure is an electromagnetic coupling method in which the rectangular waveguide port of the chip output and the stripline waveguide transition structure adopt a vertical transition. The rectangular waveguide port of the chip and the port of the stripline waveguide are vertically aligned, and the electromagnetic coupling is achieved through the intermediate layer (metal signal layer) of the stripline. Specifically, it includes two forms: wide-side coupling and narrow-side coupling.

[0053] Wide-side coupling refers to the electromagnetic coupling achieved by extending the metallic signal layer of a stripline waveguide along the wide side of a rectangular waveguide.

[0054] like Figure 1 As shown, it is a 0-degree transition structure with a wide side. The internal cavity diagram shows the air cavity area in the actual object. In the actual object diagram, the strip waveguide is divided into three thin metal layers. The bottom rectangular waveguide can be made by surface metallization of plastic parts or CNC machining of metal blocks.

[0055] like Figure 2 As shown, the structure has a 90-degree transition on the wide side, which is a variation of the 0-degree transition on the wide side. It is suitable for occasions that require a 90-degree transition. The internal cavity diagram and the actual object diagram show the structural features.

[0056] like Figure 3 The electric field diagram of the 0-degree transition structure shows that the transition structure can convert the TE mode of the vertical rectangular waveguide into the TEM mode of the horizontal stripline waveguide. This is because a metal signal line is added in the middle of the rectangular waveguide air cavity, and an electromagnetic coupling structure is added at the end of the signal line, which enhances the mode conversion effect.

[0057] Narrow-side coupling refers to the electromagnetic coupling structure in which the metallic signal layer of a stripline waveguide extends along the narrow side of a rectangular waveguide. It is suitable for miniaturized designs with size constraints and includes two electromagnetic coupling structures: single-feed flag type and dual-feed differential type.

[0058] Narrow-edge transition structure 1 (single feeder flag type)

[0059] like Figure 4 As shown, a stripline waveguide is connected to the narrow side of the rectangular waveguide. The signal line of the stripline waveguide extends into the rectangular waveguide cavity, and a square electromagnetic coupling structure resembling a flag is set at the end of the signal line. The signal feed line is connected to the corner of the patch. This structure enables a good conversion from TE mode to TEM mode.

[0060] Narrow-edge transition structure 2 (dual-feed differential type)

[0061] like Figure 5 As shown, a square metal block inserted into a rectangular waveguide at the end is fed by a dual-feeder system. One feeder is a straight line and the other is a meandering line to achieve a 180-degree phase difference (differential effect) between the two feeders.

[0062] like Figure 6 As shown, in its top view, the metal from left to right includes a square metal patch, a doubly fed differential line, and a signal line of a strip waveguide. A matching section (the width of which is slightly different from that of the square patch) is set at the connection between the square metal patch and the doubly fed differential line. The specific size is determined according to the electrical performance requirements of the actual design, which is a conventional matching operation in microwave theory.

[0063] The fan-out transition structure is based on the direct transition structure, allowing the vertical rectangular waveguide channel to continue fanning outwards. After a certain distance, it is vertically connected and aligned with the port of the stripline waveguide. Electromagnetic coupling is achieved through the intermediate layer (metallic signal layer) of the stripline.

[0064] like Figure 7 The diagram shows the cavity and physical object of the fan-out transition structure. In this example, the terminal adopts a wide-side 0-degree transition structure, but a 90-degree transition or a narrow-side transition can also be adopted according to the specific design.

[0065] There are two ways to fix vertical rectangular waveguides and horizontal stripline waveguides:

[0066] Screw fastening method: Corresponding screw holes are set on the vertical rectangular waveguide, and the two are fixed by screws;

[0067] Thermal fusion method: A vertical rectangular waveguide is placed on one side of the horizontal stripline waveguide, and several thermal fusion pillars are set on the end face of the vertical rectangular waveguide. After assembly, the thermal fusion pillars are melted by thermal fusion to form a mushroom head, thus fixing the two together. The actual fixing method used in the product depends on the specific design.

[0068] like Figure 9 and Figure 10As shown, the simulation results indicate that the wide-side 0-degree waveguide transition structure exhibits S11<-16dB and S21>-0.1dB in the 76-81GHz frequency band; the narrow-side waveguide transition structure 1 exhibits S11<-19dB and S21>-0.05dB in the same frequency band. Both demonstrate good broadband S-parameter characteristics, indicating that the transition structure of the present invention can achieve good mode conversion and signal transmission.

[0069] The above specific implementation methods, through combinations of different structural forms, processing and fixing methods, achieve an effective transition from rectangular waveguides to stripline waveguides, which can meet the application needs of vehicle-mounted millimeter-wave radar and other related fields.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A transition structure from a rectangular waveguide to a stripline waveguide, characterized in that, It includes a vertical rectangular waveguide operating in TE mode and a horizontal stripline waveguide operating in TEM mode, wherein the horizontal stripline waveguide is composed of three layers of metal sheets; The transition structure is used to connect the rectangular waveguide port of the chip to the stripline waveguide of the metal sheet, including a direct transition structure and a fan-out transition structure. An electromagnetic coupling structure is provided within the horizontal stripline waveguide, and the vertical rectangular waveguide and the horizontal stripline waveguide achieve the conversion from TE mode to TEM mode through electromagnetic coupling.

2. The transition structure from rectangular waveguide to stripline waveguide according to claim 1, characterized in that, The cross-sectional dimensions of the horizontal stripline waveguide are less than 1mm*1mm, wherein the cross-sectional dimensions of the signal layer of the stripline are less than 0.5mm(W)*0.3mm(H); When applied to the 77G radar, the horizontal strip waveguide has a cross-sectional size of 1mm(W)*0.65mm(H) and the signal layer has a cross-sectional size of 0.37mm(W)*0.15mm(H).

3. The transition structure from rectangular waveguide to stripline waveguide according to claim 1, characterized in that, The first layer of the horizontal stripline waveguide consists of an air layer above the metal signal layer and an outer metal ground layer, referred to as the top layer; The second layer is the signal layer itself, also known as the intermediate layer; The third layer consists of the air layer below the signal layer and the outer metal ground layer, which is called the bottom layer. The thickness of the three-layer metal sheet ranges from 0.1mm to 0.5mm; The three layers are fastened together with screws, and glue can be applied between each layer before the screws are tightened.

4. The transition structure from rectangular waveguide to stripline waveguide according to claim 1, characterized in that, The direct transition structure is an electromagnetic coupling method in which the rectangular waveguide port of the chip output and the stripline waveguide transition structure adopt a vertical transition. The rectangular waveguide port of the chip and the port of the stripline waveguide are vertically aligned, and the electromagnetic coupling is achieved through the middle layer of the stripline, namely the metal signal layer. The fan-out transition structure is based on the direct transition structure, with the vertical rectangular waveguide channel continuing to fan outward. After a certain distance, it is vertically switched and aligned with the port of the stripline waveguide. Electromagnetic coupling is achieved through the middle layer of the stripline, i.e., the metal signal layer.

5. The transition structure from rectangular waveguide to stripline waveguide according to claim 1, characterized in that, The electromagnetic coupling structure is divided into two types: wide-side coupling and narrow-side coupling. The wide-side coupling refers to the metal signal layer of the stripline waveguide extending into the wide side of the rectangular waveguide to achieve electromagnetic coupling. The narrow-side coupling refers to the electromagnetic coupling achieved by extending the metallic signal layer of the stripline waveguide along the narrow side of the rectangular waveguide.

6. The transition structure from rectangular waveguide to stripline waveguide according to claim 5, characterized in that, The narrow-side coupled electromagnetic coupling structure includes a single-feed flag type, wherein the end electromagnetic coupling structure of the single-feed flag type is square, and the signal feed line is connected to the corner of the patch.

7. The transition structure from rectangular waveguide to stripline waveguide according to claim 5, characterized in that, The narrow-side coupled electromagnetic coupling structure also includes a dual-feed differential type, which uses two feeders to feed a square metal block with its end inserted into a rectangular waveguide. One feeder is a straight line, and the other is a meandering line to achieve a 180-degree phase difference.

8. The transition structure from rectangular waveguide to stripline waveguide according to claim 1, characterized in that, The vertical rectangular waveguide and the horizontal stripline waveguide are fixed by screw fastening. The vertical rectangular waveguide is provided with corresponding screw holes, and the horizontal stripline waveguide and the vertical rectangular waveguide are fixed by screws.

9. The transition structure from rectangular waveguide to stripline waveguide according to claim 1, characterized in that, The vertical rectangular waveguide and the horizontal stripline waveguide are fixed by thermal fusion. The vertical rectangular waveguide is set on one side of the horizontal stripline waveguide, and several thermal fusion pillars are set on the end face of the vertical rectangular waveguide. After the horizontal stripline waveguide and the vertical rectangular waveguide are assembled, the thermal fusion pillars are melted by thermal fusion to form a mushroom head, thereby fixing the two together.

10. The transition structure from a rectangular waveguide to a stripline waveguide according to claim 1, characterized in that, The vertical rectangular waveguide is processed in two ways: plastic injection molding followed by surface metallization and CNC machining of metal blocks.

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