A highly directive ultra-wideband coupler

Abstract

The present application discloses a highly directional ultra-wideband coupler, comprising a mutually coupled main microstrip line and a secondary microstrip line, wherein a sawtooth structure is provided on the coupling side between the main microstrip line and the secondary microstrip line to increase the coupling spacing between the main microstrip line and the secondary microstrip line, thereby adjusting the impedance of the main microstrip line and the secondary microstrip line; an isolation port is connected to a matching load with a zigzag structure and then grounded, and the energy flow direction of the matching load is opposite to the energy flow direction of the main microstrip line. By providing a sawtooth structure on the coupling side between the main microstrip line and the secondary microstrip line, combined with the matching load with a zigzag structure connected to the isolation port, the present application can utilize the parasitic parameters introduced by the matching load to positively improve the performance of the highly directional ultra-wideband coupler, achieve joint optimization between the internal main microstrip line and the secondary microstrip line, effectively optimize the odd and even mode impedance consistency, and achieve an improvement in the directionality of the coupler, while having a small overall size, a simple structure, and convenient processing.

Description

Technical Field

[0001] The present application relates to the technical field of directional couplers, and in particular to a highly directional ultra-wideband coupler. Background Art

[0002] Directional couplers are four-port passive components used for power distribution and are widely used in RF and microwave systems. They play an indispensable role in electronic countermeasures, communications, radar systems, and test and measurement instruments. Their primary uses include combining and distributing power, expanding power range, and monitoring power and spectrum. In key microwave measurement instruments such as vector network analyzers and reflectometers, directional couplers are crucial components in circuits, determining their performance.

[0003] The current requirements for directional couplers are large bandwidth, miniaturization, and integration. However, the increase in bandwidth and the reduction in volume will cause a deterioration in their directivity, seriously affecting the performance of the coupler. Therefore, how to maximize the directivity while achieving miniaturization and ultra-wideband is the focus and difficulty of research.

[0004] Faced with the ultra-wideband requirements of directional couplers, researchers have generally adopted transmission line structures, the most common of which are microstrip and stripline. Microstrip structures are easy to process and manufacture, so they have the widest range of applications. For example, by adding branches to the coupler, the directivity reaches 25dB within the 45-85GHz bandwidth. For another example, by adding interdigital capacitors to the coupler, the directivity reaches 25dB within the 1.5-3.5GHz bandwidth. Most of the ultra-wideband directional couplers with high directivity reported so far operate in lower frequency bands, with directivity mostly concentrated between 20-25dB. Therefore, how to achieve higher directivity of more than 25dB within the ultra-wide operating band exceeding 100GHz is a problem that needs to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a highly directional ultra-wideband coupler to solve the technical problem of low directivity of ultra-wideband couplers in the prior art. The various technical effects that can be produced by the preferred technical solution among the many technical solutions provided in this application are described in detail below.

[0006] To achieve the above objectives, this application provides the following technical solutions:

[0007] The present application provides a highly directional ultra-wideband coupler, comprising a main microstrip line and a secondary microstrip line coupled to each other, wherein one end of the main microstrip line is configured as an input port of the coupler for receiving electromagnetic wave signals, and the other end is configured as a through output port for outputting signals; one end of the secondary microstrip line is configured as a coupled output port of the coupler, and the other end is configured as an isolation port;

[0008] A sawtooth structure is provided on the coupling side between the main microstrip line and the auxiliary microstrip line, so as to increase the coupling distance between the main microstrip line and the auxiliary microstrip line, thereby adjusting the impedance of the main microstrip line and the auxiliary microstrip line;

[0009] The isolation port is connected to a matching load of a zigzag structure and then grounded, and the energy flow direction of the matching load is opposite to the energy flow direction of the main microstrip line.

[0010] In some embodiments, a first platform-shaped sawtooth structure is provided on the coupling side between the main microstrip line and the auxiliary microstrip line, and a second platform-shaped sawtooth structure is provided on the coupling side between the auxiliary microstrip line and the main microstrip line. The height of the first platform-shaped sawtooth structure is higher than that of the second platform-shaped sawtooth structure.

[0011] In some embodiments, the first platform-shaped serrated structure includes a plurality of alternating first recesses and first protrusions, and the second platform-shaped serrated structure includes a plurality of alternating second recesses and second protrusions, the first recesses are aligned with the second protrusions, the first protrusions are aligned with the second recesses, and the height of the first protrusions is higher than the height of the second protrusions.

[0012] In some embodiments, the shapes of the first concave portion, the first protrusion, the second concave portion, and the second protrusion are all trapezoidal.

[0013] In some embodiments, the top ends of the first protrusion and the second protrusion are both platforms, and the platform of the first protrusion and the platform of the second protrusion are on the same straight line.

[0014] In some embodiments, the matching load is a thin film resistor with a meander structure, one end of the thin film resistor is connected to the isolation port, and several positions of the thin film resistor are grounded.

[0015] In some embodiments, symmetrical conductive strips are distributed on both sides of the thin film resistor, and the conductive strips are provided with symmetrical circular vias. The thin film resistor is connected to the circular vias through the conductive strips and then grounded.

[0016] In some embodiments, the zigzag structure includes curved portions and straight portions, the curved portions and the straight portions are alternately connected end to end, and energy flow directions of two adjacent straight portions are opposite.

[0017] In some embodiments, the isolation port is connected to the first of the straight portions, and an end surface of the last of the straight portions is connected to the guide strip.

[0018] In some embodiments, each of the curved portions is connected to the conductive strip.

[0019] Implementing one of the above-mentioned technical solutions of the present application has the following advantages or beneficial effects: the high-directivity ultra-wideband coupler of the present application, by setting a sawtooth structure on the coupling side between the main microstrip line and the auxiliary microstrip line, combined with a matching load with a zigzag structure connected to the isolation port, can utilize the parasitic parameters introduced by the matching load to positively improve the performance of the high-directivity ultra-wideband coupler, breaking the conventional thinking of the role of traditional matching loads, realizing the joint optimization between the main microstrip line and the auxiliary microstrip line inside the high-directivity ultra-wideband coupler, effectively optimizing the odd and even mode impedance consistency of the high-directivity ultra-wideband coupler, realizing the improvement of the directionality of the high-directivity ultra-wideband coupler, and having a small overall size, a simple structure, and convenient processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive work. In the drawings:

[0021] Figure 1 is a schematic block diagram of a highly directional ultra-wideband coupler according to an embodiment of the present application;

[0022] Figure 2 1 is a schematic structural diagram of a highly directional ultra-wideband coupler according to an embodiment of the present application;

[0023] Figure 3 This is a schematic structural diagram of a sawtooth structure according to an embodiment of the present application;

[0024] Figure 4 is a schematic structural diagram of a matching load according to an embodiment of the present application;

[0025] Figure 5 is an energy flow diagram of a matching load according to an embodiment of the present application;

[0026] Figure 6 Schematic diagram of simulation results of a highly directional ultra-wideband coupler according to an embodiment of the present application.

[0027] In the figure: 1. Main microstrip line; 2. Sub-microstrip line; 3. Conducting strip; 4. Matching load; 5. Dielectric layer; 6. Circular via; 10. Input port; 20. Through output port; 30. Isolation port; 40. Coupled output port; 11. Sawtooth structure; 12. First platform-like sawtooth structure; 21. Second platform-like sawtooth structure; 41. Straight portion; 42. Curved portion; 121. First protrusion; 122. First recess; 211. Second protrusion; 212. Second recess. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present application clearer, the various exemplary embodiments to be described below will refer to the corresponding drawings, which constitute a part of the exemplary embodiments, in which various exemplary embodiments that may be used to implement the present application are described. Unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation methods described in the following exemplary embodiments do not represent all implementation methods consistent with the present disclosure. It should be understood that they are only examples of processes, methods and devices that are consistent with some aspects disclosed in the present application as detailed in the attached claims, and other embodiments may also be used, or structural and functional modifications may be made to the embodiments listed herein without departing from the scope and essence of the present application.

[0029] In the description of this application, it should be understood that the terms "center", "longitudinal", "transverse" and the like indicate the orientation or positional relationship based on the figures, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the elements referred to must have a specific orientation, be constructed and operated in a specific orientation. The terms "first", "second" and the like are only used for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. The term "multiple" means two or more. The terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, an integral connection, a mechanical connection, an electrical connection, a communication connection, a direct connection, an indirect connection through an intermediate medium, and can be the internal connection of two elements or the interaction relationship between two elements. The term "and / or" includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0030] In order to illustrate the technical solution described in this application, a specific embodiment is provided below, and only the parts related to the embodiment of this application are shown.

[0031] like Figures 1 to 2 As shown, the present application provides a highly directive ultra-wideband coupler, comprising a main microstrip line 1 and a secondary microstrip line 2 coupled to each other, wherein one end of the main microstrip line 1 is configured as an input port 10 of the coupler for receiving electromagnetic wave signals, and the other end is configured as a through output port 20 for outputting signals; one end of the secondary microstrip line 2 is configured as a coupled output port 40 of the coupler, and the other end is configured as an isolation port 30;

[0032] A sawtooth structure 11 is provided on the coupling side between the main microstrip line 1 and the auxiliary microstrip line 2 to increase the coupling distance between the main microstrip line 1 and the auxiliary microstrip line 2, thereby adjusting the impedance of the main microstrip line 1 and the auxiliary microstrip line 2;

[0033] The isolation port 30 is connected to the matching load 4 and then grounded. The energy flow direction of the matching load 4 is opposite to the energy flow direction of the main microstrip line 1 .

[0034] Specifically, the highly directive ultra-wideband coupler of the present invention employs a single-layer coupled microstrip line structure, comprising a main microstrip line 1, a secondary microstrip line 2, and a conductive strip 3. The conductive strip 3 is a metal conductive strip layer. The main microstrip line 1, the secondary microstrip line 2, and the conductive strip 3 are all disposed on a dielectric layer 5. A through-output port 20 and a coupled output port 40 have a 90° phase difference, and an isolated port 30 is connected to a matching load 4 and then grounded. The highly directive ultra-wideband coupler has an overall size of 2.2 mm by 1.8 mm by 0.13 mm, an operating bandwidth of 50-120 GHz, and a directivity of 26-30 dB in the 50-60 GHz range and greater than 30 dB in the 60-120 GHz range.

[0035] By adding a sawtooth structure 11 to the coupling side between the main microstrip line 1 and the auxiliary microstrip line 2, the coupling spacing between the coupled main microstrip line 1 and the auxiliary microstrip line 2 can be increased, the coupling between the main structures of the coupled microstrip lines (the coupled main microstrip line 1 and the auxiliary microstrip line 2) can be weakened, and more energy can be guided to be coupled through the sawtooth structure 11. The sawtooth structure 11 more effectively adjusts the impedance of the main microstrip line 1 and the auxiliary microstrip line 2.

[0036] Furthermore, by controlling the height of the sawtooth structure 11, the impedance of the main microstrip line 1 and the auxiliary microstrip line 2 is effectively regulated, so that the parasitic parameters of the matching load 4 connected to the isolation port 30 form a favorable resonance, which can improve the directivity of the high-directivity ultra-wideband coupler.

[0037] The operating principle of this highly directive ultra-wideband coupler is as follows: an electromagnetic wave signal is input to input port 10, and the majority of the electromagnetic wave signal is output from the through-port 20. That is, the energy flow direction of the main microstrip line 1 is from the input port 10 to the through-port 20. A small portion of the electromagnetic wave signal is coupled to the secondary microstrip line 2 through the coupling between the main microstrip line 1 and the secondary microstrip line 2. At this time, the energy flow direction of the secondary microstrip line 2 is opposite to that of the main microstrip line 1. A portion of the energy coupled to the secondary microstrip line 2 is output from the coupling output port 40, while the remaining energy is reflected due to impedance mismatch and output through the isolation port 30.

[0038] In some embodiments, as Figure 3 As shown, a first platform-shaped sawtooth structure 12 is provided on the coupling side of the main microstrip line 1 and the auxiliary microstrip line 2, and a second platform-shaped sawtooth structure 21 is provided on the coupling side of the auxiliary microstrip line 2 and the main microstrip line 1. The height of the first platform-shaped sawtooth structure 12 is higher than the height of the second platform-shaped sawtooth structure 21.

[0039] Specifically, the sawtooth structure 11 includes a first platform-shaped sawtooth structure 12 located on the main microstrip line 1 and a second platform-shaped sawtooth structure 21 located on the auxiliary microstrip line 2. The height of the first platform-shaped sawtooth structure 12 is higher than the height of the second platform-shaped sawtooth structure 21, indicating that the height change of the first platform-shaped sawtooth structure 12 of the main microstrip line 1 is greater than the height change of the second platform-shaped sawtooth structure 21 of the auxiliary microstrip line 2. This makes the first platform-shaped sawtooth structure 12 and the second platform-shaped sawtooth structure 21 asymmetrical in the upper and lower parts. Such a sawtooth design can increase the coupling spacing between the coupled microstrip lines, weaken the coupling between the main structures of the coupled microstrip lines, and more effectively adjust the impedance of the main microstrip line 1 and the auxiliary microstrip line 2.

[0040] In some embodiments, the first platform-shaped serrated structure 12 includes a plurality of alternating first recesses 122 and first protrusions 121, and the second platform-shaped serrated structure 21 includes a plurality of alternating second recesses 212 and second protrusions 211, the first recesses 122 are aligned with the second protrusions 211, the first protrusions 121 are aligned with the second recesses 212, and the height of the first protrusions 121 is higher than the height of the second protrusions 211.

[0041] Specifically, the first recess 122 and the first protrusion 121 constitute a first platform-shaped sawtooth structure 12, and correspondingly, the second recess 212 and the second protrusion 211 constitute a second platform-shaped sawtooth structure 21. The height of the first protrusion 121 is higher than the height of the second protrusion 211, so that the first protrusion 121 and the second protrusion 211 are asymmetric, and the height of the first platform-shaped sawtooth structure 12 is higher than the height of the second platform-shaped sawtooth structure 21, thereby realizing that the first platform-shaped sawtooth and the second platform-shaped sawtooth structure 21 are asymmetric structures in an upper and lower direction, which is beneficial to regulating the impedance of the coupled main microstrip line 1 and the auxiliary microstrip line 2, so that the parasitic parameters of the matching load 4 connected to the isolation port 30 form a favorable resonance, thereby improving the directivity of the high-directivity ultra-wideband coupler.

[0042] The sawtooth structure 11 formed by the first recess 122, the first protrusion 121, the second recess 212 and the second protrusion 211 increases the distance between the main microstrip line 1 and the auxiliary microstrip line 2, and can guide the energy flow through the sawtooth structure 11. The height of the first protrusion 121 and the second protrusion 211 is mainly responsible for ensuring the coupling strength. The height of the first recess 122 and the second recess 212 can adjust the impedance of the main microstrip line 1 and the auxiliary microstrip line 2 without significantly affecting the coupling strength.

[0043] In some embodiments, the first concave portion 122, the first protrusion 121, the second concave portion 212, and the second protrusion 211 are all trapezoidal in shape. The trapezoidal first concave portion 122 and the first protrusion 121 form a first platform-shaped sawtooth structure 12; correspondingly, the trapezoidal second concave portion 212 and the second protrusion 211 form a second platform-shaped sawtooth structure 21.

[0044] In some embodiments, the tops of the first protrusion 121 and the second protrusion 211 are both platforms, and the platform 1211 of the first protrusion 121 and the platform 2111 of the second protrusion 211 are on the same straight line. This allows the main microstrip line 1 and the auxiliary microstrip line 2 to couple, and the first recess 122 and the second recess 212 provide a coupling gap between the main microstrip line 1 and the auxiliary microstrip line 2.

[0045] Compared with the case where the top end is pointed, the pointed end is more likely to cause resonance at high frequencies, causing performance degradation. Compared with the case where the first protrusion 121 and the second protrusion 211 are rectangular in shape, the rectangle has right angles and is also more likely to cause interference at high frequencies.

[0046] Therefore, the trapezoidal first concave portion 122 , the first protrusion 121 , the second concave portion 212 and the second protrusion 211 can transition at oblique edges, thereby eliminating resonance and interference between sharp points and right angles at high frequencies.

[0047] In some embodiments, as Figure 2 ,4, the matching load 4 is a thin film resistor with a zigzag structure, one end of the thin film resistor is connected to the isolation port 30, and several positions of the thin film resistor are grounded.

[0048] The zigzag structure of the thin-film resistor forces the current within the thin-film resistor to flow in an interlaced manner, thereby reducing the influence of parasitic parameters and enabling the matching load 4 to maintain a low reflection coefficient below -29dB across the ultra-wide operating frequency band of 50GHz-120GHz. By adjusting the height difference between the sawtooth structure 11 on the main microstrip line 1 and the auxiliary microstrip line 2, the parasitic parameters introduced by the matching load 4 can produce a forward resonance, further compensating for the difference in odd- and even-mode impedance of the highly directional ultra-wideband coupler, thereby further improving the directivity of the highly directional ultra-wideband coupler.

[0049] In some embodiments, symmetrical conductive strips 3 are distributed on both sides of the thin film resistor. The conductive strips 3 are provided with symmetrical circular vias 6. The thin film resistor is connected to the circular vias 6 through the conductive strips 3 and then grounded.

[0050] Specifically, there is a conductive strip 3 on the left side of the thin film resistor, and the same conductive strip 3 on the right side. Each conductive strip 3 has a circular via 6. The circular vias 6 on the left and right sides of the thin film resistor are symmetrically distributed with respect to the thin film resistor. Then, multiple positions where the thin film resistor contacts the conductive strip 3 are grounded through these circular vias 6 respectively.

[0051] In some embodiments, the zigzag structure includes curved portions 42 and straight portions 41 , the curved portions 42 and the straight portions 41 are alternately connected end to end, and the energy flow directions of two adjacent straight portions 41 are opposite.

[0052] Specifically, the head end of the first straight portion 41 is connected to the guide strip 3 on the right, the tail end of the first straight portion 41 is connected to the head end of the first curved portion 42, the tail end of the first curved portion 42 is connected to the head end of the second straight portion 41, the tail end of the second straight portion 41 is connected to the head end of the second curved portion 42, the tail end of the second curved portion 42 is connected to the head end of the third straight portion 41, the tail end of the third straight portion 41 is connected to the head end of the third curved portion 42, the tail end of the third curved portion 42 is connected to the head end of the fourth straight portion 41, and so on, until the tail end of the last straight portion 41 is connected to the guide strip 3 next to it. Figure 4 Take five straight portions 41 and four curved portions 42 as an example to form a thin film resistor.

[0053] Too few straight portions 41 will result in too short an energy flow length, and the energy cannot be fully absorbed by the matching load 4 ; too many straight portions 41 will also result in too many curved portions 42 , resulting in excessive parasitic parameters and weakening the absorption efficiency of the matching load 4 .

[0054] like Figure 5 As shown, Figure 5 The energy flow direction of the thin film resistor is shown in Figure 4. Obviously, the energy flow direction of the first straight portion 41 is opposite to that of the second straight portion 41, and the energy flow direction of the second straight portion 41 is opposite to that of the third straight portion 41. By alternately connecting the curved portions 42 to the straight portions 41, the currents in adjacent straight portions 41 are forced to be in phase reversal, thereby reducing the influence of parasitic parameters.

[0055] In some embodiments, the isolation port 30 is connected to the first straight portion 41 , and the end surface of the last straight portion 41 is connected to the conductive strip 3 .

[0056] Since the isolation port 30 is not used in practice, the matching load 4 is connected, specifically the first straight portion 41 of the thin film resistor is connected. Then, the last straight portion 41 is actually the end surface of the tail end connected to the conductive strip 3.

[0057] In some embodiments, each curved portion 42 is connected to the conductive strip 3. In contrast, only the leading and trailing ends of the straight portion 41 are connected to the conductive strip 3, while the curved portion 42 is entirely connected to the conductive strip 3. Furthermore, the conductive strip 3 is provided with a plurality of circular vias 6, which facilitate grounding of the curved portion 42 through the circular vias 6.

[0058] The high-directivity ultra-wideband coupler of the present application, by providing a sawtooth structure 11 on the coupling side between the main microstrip line 1 and the auxiliary microstrip line 2, combined with a matching load 4 with a zigzag structure connected to the isolation port 30, can utilize the parasitic parameters introduced by the matching load 4 to positively improve the performance of the high-directivity ultra-wideband coupler, breaking the conventional thinking about the role of the traditional matching load 4, achieving joint optimization between the main microstrip line 1 and the auxiliary microstrip line 2 inside the high-directivity ultra-wideband coupler, effectively optimizing the odd-mode and even-mode impedance consistency of the high-directivity ultra-wideband coupler, and achieving an improvement in the directionality of the high-directivity ultra-wideband coupler, while having a small overall size, a simple structure, and convenient processing.

[0059] At the same time, the highly directional ultra-wideband coupler of the present application propagates quasi-TEM waves. Compared with the TEM waves of the rectangular waveguide structure, the structure of the highly directional ultra-wideband coupler supports multi-mode transmission, thereby covering a larger frequency range and achieving an ultra-wide operating frequency band of 50-120 GHz.

[0060] like Figure 6 As shown, the horizontal axis represents the frequency, and the vertical axis represents the scattering parameter. The scattering parameter is the S parameter, which is an important parameter in microwave transmission. The directivity within the bandwidth is equal to Obviously, the directivity of the high-directivity ultra-wideband coupler reaches more than 26dB in the range of 50GHz-60GHz, and further reaches more than 30dB in the range of 60-120GHz, successfully achieving high directivity at high frequency and large bandwidth. Compared with similar couplers, the high-directivity ultra-wideband coupler designed by the present invention has higher frequency, larger bandwidth and better directivity.

[0061] The above are merely preferred embodiments of the present application. Those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present application. Furthermore, under the guidance of this application, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by this application.

Claims

1. A highly directive ultra-wideband coupler, characterized in that: It includes a main microstrip line and an auxiliary microstrip line coupled to each other, wherein one end of the main microstrip line is configured as an input port of the coupler for receiving electromagnetic wave signals, and the other end is configured as a through output port for outputting signals; One end of the secondary microstrip line is configured as a coupled output port of the coupler, and the other end is configured as an isolation port; A sawtooth structure is provided on the coupling side between the main microstrip line and the auxiliary microstrip line, so as to increase the coupling distance between the main microstrip line and the auxiliary microstrip line, thereby adjusting the impedance of the main microstrip line and the auxiliary microstrip line; The isolation port is connected to a matching load of a zigzag structure and then grounded, and the energy flow direction of the matching load is opposite to the energy flow direction of the main microstrip line; The sawtooth structure is an asymmetric trapezoidal sawtooth structure; a first platform-shaped sawtooth structure is provided on the coupling side between the main microstrip line and the auxiliary microstrip line, and a second platform-shaped sawtooth structure is provided on the coupling side between the auxiliary microstrip line and the main microstrip line, wherein the height of the first platform-shaped sawtooth structure is higher than that of the second platform-shaped sawtooth structure; The matching load is a thin film resistor with a zigzag structure, one end of the thin film resistor is connected to the isolation port, and several positions of the thin film resistor are grounded; symmetrical conduction strips are distributed on both sides of the thin film resistor, and the conduction strips are provided with symmetrical circular vias, and the thin film resistor is connected to the circular vias through the conduction strips and then grounded.

2. The high directivity ultra-wideband coupler according to claim 1, characterized in that: The first platform-shaped serrated structure includes a plurality of alternately arranged first recesses and first protrusions, and the second platform-shaped serrated structure includes a plurality of alternately arranged second recesses and second protrusions, the first recesses are aligned with the second protrusions, the first protrusions are aligned with the second recesses, and the height of the first protrusions is higher than the height of the second protrusions.

3. The high directivity ultra-wideband coupler according to claim 2, wherein: The shapes of the first concave portion, the first protrusion, the second concave portion and the second protrusion are all trapezoidal.

4. The high directivity ultra-wideband coupler according to claim 2, wherein: The top ends of the first protrusion and the second protrusion are both platforms, and the platform of the first protrusion and the platform of the second protrusion are on the same straight line.

5. The high directivity ultra-wideband coupler according to claim 1, wherein: The zigzag structure includes a curved portion and a straight portion, wherein the curved portion and the straight portion are alternately connected end to end, and energy flow directions of two adjacent straight portions are opposite.

6. The high directivity ultra-wideband coupler according to claim 5, characterized in that: The isolation port is connected to the first straight portion, and the end surface of the last straight portion is connected to the guide strip.

7. The high directivity ultra-wideband coupler according to claim 5, characterized in that: Each of the bent portions is connected to the conductive strip.

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