Millimeter wave ultra-wideband high-performance waveguide directional coupler

Abstract

The invention discloses a millimeter wave ultra-wideband high-performance waveguide directional coupler, which comprises a first base block and a second base block, a main ridge waveguide is arranged on the first base block, an auxiliary ridge waveguide is arranged on the second base block, the first base block is connected with the second base block, a substrate is arranged between the main ridge waveguide and the auxiliary ridge waveguide, and a coupling hole is formed in the substrate. The millimeter wave ultra-wideband high-performance waveguide directional coupler provided by the invention is suitable for instrument measurement in the fields of microwaves and millimeter waves, and has the advantages of flat coupling degree, ultra-wide working bandwidth, low return loss, excellent directivity and the like.

Description

Technical Field

[0001] The invention relates to a millimeter wave ultra-wideband high-performance waveguide directional coupler, belonging to the technical field of millimeter wave couplers. Background Art

[0002] Millimeter wave transceiver front-ends are widely used in many millimeter wave and terahertz fields such as communications, radar, detection imaging, and high-speed data transmission, and are the core components of the next generation of high-performance millimeter wave systems. Among them, directional couplers are important functional components of the transceiver front-end, mainly used for signal power monitoring, sampling measurement, and distribution synthesis. The quality of its performance largely determines the reliability and measurement accuracy of the entire millimeter wave system.

[0003] As the development trend of millimeter wave technology towards higher frequencies and wider bandwidths becomes more and more obvious, the millimeter wave frequency band has broad application prospects in high data rate wireless communications, vehicle-mounted radar, security imaging, and precision measurement. However, it is not easy to achieve high-performance directional couplers in this frequency band: on the one hand, the waveguide size becomes smaller and smaller with the increase of operating frequency, and the processing accuracy of traditional machine tools cannot meet the strict dimensional tolerance requirements of coupling holes and waveguide structures of high-frequency band couplers; on the other hand, it is necessary to ensure flat coupling and low insertion loss within such a wide bandwidth, while taking into account high directivity and good impedance matching, which poses extremely high challenges to both structural design and manufacturing processes.

[0004] Compared with conventional rectangular waveguide directional couplers, ridge waveguide directional couplers have a wider fundamental mode bandwidth and are gradually becoming an important form of realization of millimeter-wave high-frequency band directional couplers. By setting a ridge structure in the narrow wall of the waveguide, the transmission characteristics can be effectively controlled and the working bandwidth can be widened. However, the millimeter-wave wide-band ridge waveguide directional coupler still has the problem of how to reduce the waveguide size and ridge spacing while ensuring that the coupling is as flat as possible and has good directivity over the entire bandwidth. In addition, under the strict processing tolerance restrictions, a small deviation in the coupling hole size may cause a sharp increase in insertion loss or unstable coupling, seriously affecting system performance. Small errors that are difficult to completely avoid in traditional machine tool processing, especially deviations in the size or positioning of the coupling hole, often lead to a significant decrease in isolation, which in turn makes the actual prepared directional coupler perform poorly in terms of directivity. The directivity of directional couplers is crucial for applications such as signal isolation, reflection measurement, and power monitoring. Highly directional couplers can effectively reduce the energy of reverse coupling and ensure the accuracy and stability of the measured or monitored signal. This deterioration of directivity will not only have an adverse effect on the measurement or monitoring accuracy in the signal link, but may even affect the reliability and performance of the entire millimeter wave system. Therefore, in the research and development and design of ridge waveguide directional couplers, how to ensure high directivity through more precise manufacturing methods and more reliable structural design has become a key technical issue in the current millimeter wave field.

[0005] With the rapid evolution of millimeter wave systems in the direction of miniaturization, more and more functional modules need to be implemented on a single chip or modular platform, which requires the directional coupler to be as simple as possible in structure and integrated with other millimeter wave devices on the same substrate or package. Traditional machined ridge waveguide directional couplers often have large errors in machining accuracy, especially in the machining accuracy of the coupling holes, which makes it difficult to fully meet the needs of the new generation of millimeter wave systems.

[0006] At present, some professionals have proposed some solutions. The invention patent - Ridge waveguide directional coupler invented a method of opening 1 or 2 holes in the common wall of the waveguide to connect the main waveguide and the sub-waveguide, achieving the characteristics of wide working bandwidth and low insertion loss, but the coupling flatness of this type of ridge waveguide coupler is poor. The invention patent - Millimeter wave ridge waveguide dual directional coupler with high coupling flatness invented a method of using double ridges for the main waveguide and a single ridge for the sub-waveguide. The connection is achieved by using coupling holes in the gap between parallel waveguides, and the signal coupling sampling is achieved through two sub-waveguides. It has the advantages of high coupling output flatness, wide working frequency band, low return loss, good directivity, etc., but it does not achieve bandwidth across multiple bands, but only achieves E-band bandwidth coupler. Invention patent - a porous ridge waveguide directional coupler with staggered coupling holes has been invented. Three or more semi-cylindrical or triangular coupling holes are opened on both sides of the hollow coupling tube of the main ridge waveguide side wall and the sub-ridge waveguide side wall to achieve the connection between the main and sub-waveguides and the coupling effect. It has a wide bandwidth and low insertion loss, but the coupling flatness of this directional coupler is poor.

[0007] Therefore, how to improve or innovatively design the structure of the ridge waveguide directional coupler in this frequency band to achieve miniaturization while taking into account broadband, low insertion loss and high directivity has become a core technical problem that technical personnel in this field need to solve urgently. Summary of the invention

[0008] Purpose: In order to overcome the shortcomings of the ridge waveguide directional coupler in the prior art, such as insufficient bandwidth and large coupling hole processing errors, the present invention provides a millimeter-wave ultra-wideband high-performance waveguide directional coupler, so as to meet the requirements of ultra-wideband ridge waveguide directional couplers in engineering applications. The ridge structure for impedance matching and two rows of symmetrical coupling holes formed by etching a gold layer on the surface of a quartz substrate achieve the advantages of high coupling output flatness, wide operating frequency band, low return loss, good directivity, etc. Its band covers three bands, E, W, and D, and realizes a millimeter-wave broadband directional coupler with multi-band coverage for the first time. Under the premise of multi-band coverage, it achieves excellent performance of less than 0.5dB insertion loss and greater than 27dB directivity.

[0009] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is:

[0010] A millimeter-wave ultra-wideband high-performance waveguide directional coupler comprises: a first base block and a second base block; a main ridge waveguide is arranged on the first base block, a sub-ridge waveguide is arranged on the second base block, the first base block is connected to the second base block, a substrate is arranged between the main ridge waveguide and the sub-ridge waveguide, and a coupling hole is arranged on the substrate.

[0011] As a preferred solution, the main ridge waveguide comprises: a first groove, in which a first ridge structure is arranged.

[0012] As a preferred solution, a clamping groove is provided at the top of the first groove.

[0013] As a preferred solution, the width and height of the first portions at both ends of the first ridge structure not covered by the substrate are not equal to the width and height of the second portion of the first ridge structure covered by the substrate.

[0014] As a preferred solution, the sub-ridge waveguide comprises: a second groove, in which a second ridge structure is arranged.

[0015] As a preferred solution, the second groove includes: a middle portion, both ends of the middle portion are respectively connected to the bending portions, each bending portion is connected to one end of the end portion, and there is an angle between the middle portion and the end portion.

[0016] As a preferred solution, the width and height of the third portion of the middle of the second ridge structure covered by the substrate are consistent with the width and height of the second portion of the first ridge structure.

[0017] As a preferred solution, two rows of coupling holes are arranged on the substrate, the number of coupling holes in each row is the same, and the total number of coupling holes in the two rows matches the bandwidth of the coupler.

[0018] As a preferred solution, the spacing between two adjacent coupling holes in each row of coupling holes is the same.

[0019] As a preferred solution, each row of coupling holes is symmetrically distributed about the center position, and the diameter distribution from the center coupling hole to the coupling holes at both ends meets the requirements of the Chebyshev array.

[0020] Beneficial effects: The present invention provides a millimeter-wave ultra-wideband high-performance waveguide directional coupler, which specifically includes a main ridge waveguide for microwave signal transmission, a sub-ridge waveguide for signal sampling, a ridge structure for impedance matching, and two rows of symmetrical coupling holes formed by etching a gold layer on the surface of a quartz substrate; the main ridge waveguide and the sub-ridge waveguide are both single-ridge waveguides, wherein the main ridge waveguide adopts a stepped ridge structure to achieve impedance matching to reduce signal reflection and transmission loss, and the sub-ridge waveguide is a standard single-ridge waveguide; the two sides of the main ridge waveguide are connected to the sub-ridge waveguide through coupling holes, respectively, and the coupling holes serve as coupling channels to transmit part of the signal energy. The coupling holes are prepared by etching a gold layer on the quartz surface, which significantly improves the processing accuracy of the coupling hole size and overcomes the problem of errors in the traditional machine tool when processing copper sheets to form coupling holes, thereby causing the coupling degree to deteriorate.

[0021] The millimeter-wave ultra-wideband high-performance waveguide directional coupler of the present invention has two ridge structures on both sides of the main ridge waveguide from the input end to the two ends of the quartz substrate and the ridge structure located below the quartz substrate together forming a stepped ridge structure to achieve excellent impedance matching, wherein the ridge structure below the quartz substrate and the ridge structure of the secondary ridge waveguide are consistent in width and height. The millimeter-wave ultra-wideband high-performance waveguide directional coupler of the present invention is suitable for instrument measurement in the microwave and millimeter-wave fields, and has the advantages of flat coupling, ultra-wide working bandwidth, low return loss and excellent directivity. Compared with the prior art, the advantages of the present invention are:

[0022] 1. The millimeter-wave ultra-wideband high-performance waveguide directional coupler provided by the present invention has a simple structure and ultra-wide bandwidth. The directional couplers with larger bandwidths that have been proposed so far, for example, a directional coupler with a bandwidth of 66 GHz is proposed in the latest paper, and its directivity reaches 15 dB. The directional coupler proposed by the present invention has a bandwidth of 100 GHz, a directivity of 27 dB, and the advantages of good coupling flatness and excellent directivity, and can be used in millimeter-wave communication and measurement systems.

[0023] 2. The millimeter-wave ultra-wideband high-performance waveguide directional coupler of the present invention proposes for the first time to use a gold layer etched on the surface of a quartz substrate to realize a coupling hole, which can greatly reduce the coupling degree of traditional waveguides. The use of machine tools to process copper sheets to form coupling holes leads to processing errors, making the performance of the coupler more stable, which plays an important role in fields such as millimeter-wave communications and measurements with strict requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the assembly structure of the millimeter-wave ultra-wideband high-performance waveguide directional coupler of the present invention.

[0025] Figure 2 It is a schematic structural diagram of the first base block of the millimeter-wave ultra-wideband high-performance waveguide directional coupler of the present invention.

[0026] Figure 3 The figure is a schematic diagram of the assembly structure of the main ridge waveguide and substrate of the millimeter wave ultra-wideband high-performance waveguide directional coupler of the present invention.

[0027] Figure 4 It is a schematic structural diagram of the second base block of the millimeter wave ultra-wideband high-performance waveguide directional coupler of the present invention.

[0028] Figure 5 This is a schematic diagram of the substrate structure of the millimeter-wave ultra-wideband high-performance waveguide directional coupler of the present invention.

[0029] Figure 6 This is a diagram of the directivity simulation results of the millimeter-wave ultra-wideband high-performance waveguide directional coupler in a specific embodiment.

[0030] Figure 7 This is a diagram showing the return loss simulation results of a millimeter-wave ultra-wideband high-performance waveguide directional coupler in a specific embodiment.

[0031] Figure 8 1 is a diagram showing the coupling degree simulation results of a millimeter-wave ultra-wideband high-performance waveguide directional coupler in a specific embodiment.

[0032] Fig. 9 This is a diagram showing the insertion loss simulation results of a millimeter-wave ultra-wideband high-performance waveguide directional coupler in a specific embodiment.

[0033] Fig.10 This is a diagram showing the isolation simulation results of a millimeter-wave ultra-wideband high-performance waveguide directional coupler in a specific embodiment. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the examples of the present invention in conjunction with the accompanying drawings in the examples of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention.

[0035] The present invention will be further described below in conjunction with specific embodiments.

[0036] Embodiment 1:

[0037] This embodiment introduces a millimeter wave ultra-wideband high-performance waveguide directional coupler, such as Figure 1 The method comprises: a first base block 1 and a second base block 2; a main ridge waveguide 3 is arranged on the first base block 1, a sub-ridge waveguide 4 is arranged on the second base block 2, the first base block 1 is connected to the second base block 2, a substrate 5 is arranged between the main ridge waveguide 3 and the sub-ridge waveguide 4, and a coupling hole 6 is arranged on the substrate 5.

[0038] The directional coupler can realize the miniaturization of the structure by etching the main ridge waveguide and the sub-ridge waveguide on the first base block and the second base block and etching the coupling hole on the substrate, wherein the main ridge waveguide is used to transmit the millimeter wave signal, and the sub-ridge waveguide is used to output the sampled millimeter wave signal. The main ridge waveguide and the sub-ridge waveguide are connected through the coupling hole on the substrate to realize the coupling effect. Through the ridge structure design of the main ridge waveguide and the sub-ridge waveguide, the cutoff frequency of the TE10 mode of the waveguide is reduced, and the cutoff frequency of the high-order mode is increased, thereby realizing the ultra-wideband characteristics. The ridge structure is used for impedance matching, thereby realizing the characteristics of low insertion loss.

[0039] Further, an embodiment, such as Figure 2 As shown, the main ridge waveguide 3 includes: a first groove 301 , in which a first ridge structure 302 is arranged.

[0040] Furthermore, in one embodiment, the first groove 301 and the first ridge structure 302 have the same height, so as to facilitate the bonding of the substrate and the main ridge waveguide.

[0041] Furthermore, in one embodiment, the first ridge structure 302 is arranged along the central axis of the first groove 301 to divide the first groove 301 into two parts.

[0042] Further, such as Figure 3 As shown, in one embodiment, a clamping groove 7 is provided at the top of the first groove 301 to facilitate the substrate to fit with the main ridge waveguide by clamping.

[0043] Furthermore, in one embodiment, the width and height of the first portion 3021 of the first ridge structure 302 not covered by the substrate at both ends are not equal to the width and height of the second portion 3022 of the first ridge structure 302 covered by the substrate, so as to achieve impedance matching of the ridge waveguide port.

[0044] Furthermore, in one embodiment, a mounting hole 8 is provided on the first base block 1 to facilitate the connection of the first base block with the second base block by screws.

[0045] Further, an embodiment, such as Figure 4 As shown, the sub-ridge waveguide 4 includes: a second groove 401 , in which a second ridge structure 402 is arranged.

[0046] Furthermore, in one embodiment, the second groove 401 and the second ridge structure 402 have the same height, so as to facilitate the bonding of the substrate and the sub-ridge waveguide.

[0047] Furthermore, in one embodiment, the second ridge structure 402 is disposed along the central axis of the second groove 401 to divide the second groove 401 into two equal parts.

[0048] Further, in one embodiment, the second groove 401 comprises: a middle portion 4011, both ends of the middle portion 4011 are respectively connected to the turning portions 4012, each turning portion 4012 is connected to one end of the end portion 4013, and there is an angle between the middle portion 4011 and the end portion 4013. This is used to stagger the port position of the sub-ridge waveguide with the port position of the main ridge waveguide, so as to facilitate connection with the rear interface.

[0049] Furthermore, in one embodiment, the angle between the middle portion 4011 and the end portion 4013 is set to 90 degrees.

[0050] Furthermore, in one embodiment, a mounting hole 8 is provided on the second base block 2 to facilitate the connection of the second base block with the first base block by screws.

[0051] Furthermore, in one embodiment, the width and height of the third portion 4021 in the middle of the second ridge structure 402 covered by the substrate are consistent with the width and height of the second portion 3022 of the first ridge structure 302 to facilitate impedance matching.

[0052] Further, an embodiment, such as Figure 5 As shown, the substrate 5 is provided with two rows of coupling holes 6, and the number of coupling holes 6 in each row is the same, so as to increase the flatness of the coupler. The position of each row of coupling holes matches with the grooves of the first groove and the second groove respectively.

[0053] Furthermore, in one embodiment, the spacing between two adjacent coupling holes in each row of coupling holes 6 is the same, such as Figure 4 The center distance a is the distance between the centers of two adjacent coupling holes. It is used for phase superposition and phase elimination during signal transmission to achieve a balanced effect of isolation and coupling.

[0054] Furthermore, in one embodiment, the total number of coupling holes 6 in the two rows matches the bandwidth of the coupler, and a greater number of coupling holes is required as the bandwidth increases.

[0055] Furthermore, in one embodiment, the spacing between two adjacent coupling holes is set to a quarter of the waveguide wavelength, so as to achieve isolation when the signal transmission phases are superimposed and destructed, thereby improving the isolation degree.

[0056] Furthermore, in one embodiment, each row of coupling holes 6 is symmetrically distributed about the center position, and the diameter distribution of the coupling holes at the center and the coupling holes at the two ends meets the requirements of the Chebyshev array, so as to achieve good coupling degree and high directivity for the signal.

[0057] Embodiment 2:

[0058] This embodiment uses a millimeter-wave ultra-wideband high-performance waveguide directional coupler with a working frequency band of 60GHz-160GHz as an embodiment to introduce the working principle of the present invention. In this embodiment, the length of the quartz substrate is 18mm, the thickness of the quartz substrate is 50um, and the width and height dimensions of the ports at both ends of the main ridge waveguide are 2mm×0.5mm, where the width and height dimensions of the first ridge structure used for impedance matching are 0.3mm×0.42mm. The width and depth dimensions of the top of the first groove of the main ridge waveguide including the card groove are 2.14mm×0.07mm, and the width and height dimensions of the second groove of the sub-ridge waveguide are 2mm×0.5mm, where the width and height dimensions of the second ridge structure of the port are 0.44mm×0.38mm. The number of coupling holes is 16 in a row, and the size of the coupling holes meets the Chebyshev array size arrangement under the bandwidth of this frequency band.

[0059] There are 4 ports at both ends of the main ridge waveguide and the sub-ridge waveguide of the directional coupler. Energy coupling is performed between the main ridge waveguide and the sub-ridge waveguide through a series of coupling holes. Within the working frequency band, microwave signals can be input from either the first port or the second port of the main ridge waveguide, and while being transmitted in the main ridge waveguide, part of the signal is coupled out to the sub-ridge waveguide through the coupling holes to achieve signal distribution and sampling.

[0060] In a wireless communication system, the directional coupler of the present invention can couple two different signal sources to each other, so that the two signal sources exist in the same circuit at the same time and can be flexibly transmitted in two directions. This embodiment adopts a ridge waveguide structure design. The ridge waveguide has a lower cutoff frequency and can increase the cutoff frequency of the waveguide high-order mode, thereby increasing the bandwidth of the coupler. Figure 6 As shown, the directivity can be guaranteed to be greater than 27dB within the working bandwidth of 60GHz-160GHz, indicating that there is significant energy isolation between the forward and reverse transmission of the signal, which can significantly reduce the impact of reverse interference on the system, and achieve the characteristics of ultra-wideband and high directivity. Compared with a directional coupler with a bandwidth of 66GHz proposed in the latest paper, its directivity reaches 15dB. The directivity of the directional coupler proposed in this embodiment is improved by 12dB and the bandwidth is increased by 34GHz.

[0061] In this embodiment, a ridge structure with impedance matching function is used at the main ridge waveguide so that the port impedance can be well matched. Figure 7 As shown, the return loss of the directional coupler in the range of 60GHz-160GHz is less than -25dB, indicating that it can maintain excellent impedance matching performance in a broadband range and significantly reduce the reflection loss caused by port mismatch, thereby ensuring the stability of signal transmission between the main ridge waveguide and the sub-ridge waveguide.

[0062] The coupling holes in this embodiment adopt the Chebyshev array size that meets the frequency band, and two rows of multiple coupling holes are used to improve the coupling flatness of the coupler. At the same time, the coupling holes are formed by etching the gold layer on the surface of the quartz substrate. This semiconductor processing technology effectively ensures the dimensional accuracy of the coupling holes. Figure 8 As shown, this embodiment can maintain the coupling degree at about 10dB within the entire operating frequency band with an error of ±1dB, which reflects the coupling flatness and consistency within the ultra-wideband range, so that the coupling signal strength obtained by the subsequent circuit or measurement equipment fluctuates very little within the entire frequency band, thereby improving the accuracy of measurement and control.

[0063] This embodiment uses a quartz substrate 5 with good ridge matching and low dielectric constant to reduce signal loss. Fig. 9 As shown, in the entire 60GHz-160GHz frequency band, the insertion loss of this embodiment is always less than 1dB, indicating that the attenuation of the signal transmitted through the directional coupler is extremely low, and the main signal energy can be effectively retained, which is suitable for millimeter wave systems with high transmission efficiency requirements. Fig.10 It is further shown that the isolation of this embodiment at the isolated port can reach greater than 37dB, which can significantly reduce signal interference between adjacent ports and provide high reliability and high isolation device support for complex multi-port millimeter wave systems.

[0064] Based on the above simulation results, it can be seen that this embodiment has excellent directivity, low return loss, flat coupling and low insertion loss in the wide frequency band of 60GHz-160GHz, which can effectively meet the needs of high-speed communications, radar detection and other fields for broadband and high-performance directional couplers, and provide reliable key component support for future highly integrated millimeter-wave systems.

[0065] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A millimeter-wave ultra-wideband high-performance waveguide directional coupler, characterized in that: include: A first base block and a second base block; a main ridge waveguide is arranged on the first base block, a sub-ridge waveguide is arranged on the second base block, the first base block is connected to the second base block, a substrate is arranged between the main ridge waveguide and the sub-ridge waveguide, and a coupling hole is arranged on the substrate.

2. A millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 1, characterized in that: The main ridge waveguide includes a first groove, in which a first ridge structure is arranged.

3. A millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 2, characterized in that: A clamping groove is arranged at the top of the first groove.

4. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 2, characterized in that: The width and height of the first portions at both ends of the first ridge structure not covered by the substrate are not equal to the width and height of the second portion of the first ridge structure covered by the substrate.

5. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 1, characterized in that: The sub-ridge waveguide includes: a second groove, in which a second ridge structure is arranged.

6. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 5, characterized in that: The second groove includes a middle portion, both ends of the middle portion are respectively connected to the bending portions, each bending portion is connected to one end of the end portion, and an angle is formed between the middle portion and the end portion.

7. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 5, characterized in that: The width and height of the third portion of the middle of the second ridge structure covered by the substrate are consistent with the width and height of the second portion of the first ridge structure.

8. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 1, characterized in that: Two rows of coupling holes are arranged on the substrate, the number of coupling holes in each row is the same, and the total number of coupling holes in the two rows matches the bandwidth of the coupler.

9. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 8, characterized in that: The distances between two adjacent coupling holes in each row of coupling holes are the same.

10. The millimeter-wave ultra-wideband high-performance waveguide directional coupler according to claim 8, characterized in that: Each row of coupling holes is symmetrically distributed about the center position, and the diameter distribution of the coupling holes from the center to the two end coupling holes meets the requirements of the Chebyshev array.

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