High-frequency millimeter wave power combiner based on diaphragm structure and mode conversion method

Abstract

The invention discloses a high-frequency millimeter wave power combiner based on a diaphragm structure and a mode conversion method. The power combiner comprises N (N is greater than or equal to 4) paths of power combining cavities, a diaphragm type mode converter and a circular truncated cone coaxial integrated module, wherein each power combining cavity consists of a rectangular input waveguide layer, a radial step waveguide layer and a circular waveguide layer; the diaphragm type mode converter is composed of a mode conversion diaphragm and a circular-rectangular transition waveguide. And the circular truncated cone coaxial integrated module comprises a second-stage fixed circular truncated cone, a third-stage matched circular truncated cone and a coaxial inner conductor. Multiple paths of TE10 mode signals are input from the rectangular input waveguide, are synthesized into a TEM mode through the radial stepped waveguide, are converted into a TE10 mode through the diaphragm type mode converter, and are finally output from the circular-rectangular transition waveguide. The broadband and low-loss power synthesis is realized through the three-stage matching circular truncated cone and the mode conversion diaphragm, and the broadband and low-loss power synthesizer has the characteristics of simple structure, miniaturization and high integration level, and is suitable for a high-frequency millimeter wave system.

Description

Technical Field

[0001] The present invention relates to the technical field of high-frequency millimeter-wave power combining, and particularly relates to a high-frequency millimeter-wave power combiner based on a diaphragm structure and a mode conversion method. Background Art

[0002] In a high-frequency millimeter-wave band communication system, a power amplifier plays a crucial role and is a key component to ensure that signals can cover long distances and penetrate obstacles. The main function of a power amplifier is to increase the power of the transmitted signal so that it can maintain sufficient strength during long-distance transmission to overcome path loss and interference and ensure the reliability and stability of the signal. Since high-frequency millimeter-wave signals encounter various losses during transmission, including atmospheric absorption, rain fade, and obstruction by physical obstacles such as buildings, a high-performance power amplifier is crucial for maintaining the integrity of the communication link.

[0003] Current high-frequency millimeter-wave power combining technologies mainly include hierarchical power combining technology, in-waveguide spatial combining technology, and free-space combining technology. The hierarchical power combiner has a simple design structure. However, with the increase in the number of combining stages and the extension of the transmission line length, there are problems such as large losses, low combining efficiency, large volume, and low integration. The free-space combining technology, based on the interference synthesis of array radiation waves in free space, has the advantages of high power, multiple channels, and direct emission. However, since its implementation architecture is similar to that of array antenna technology, it is mainly applicable to directional emission scenarios and is difficult to simultaneously meet the requirements of broadband, high combining efficiency, and high power. In contrast, the in-waveguide spatial combining technology utilizes the symmetric electromagnetic field modes in a multimode waveguide to directly combine signals from multiple symmetric branches, demonstrating high-efficient power combining ability, low loss, and strong anti-interference performance.

[0004] One of the core components of power combining technology is the mode converter. The design of the mode converter is crucial for achieving the conversion between different modes. For example, a 16-way power combiner operating in the Ku band designed by José R. Montejo-Garai et al. ["High-performance 16-way Ku-band radial power combiner based on the TE01 circular waveguide mode", authors: José R. Montejo-Garai, Irene O. Saracho-Pantoja, Jorge A. Ruiz-Cruz, and Jesús M. Rebollar; Review of Scientific Instruments, [s.l.], v. 89, n. 3, p. 1, 2018.], the core of this combiner is the TE01-TE10 petal-shaped mode converter. This design first inputs 16 in-phase signals with equal amplitude, synthesizes the TE01 mode through the radial waveguide and the matching frustum, the TE01 mode is transmitted in the circular waveguide, and the petal-shaped mode converter is used to convert the TE01 mode to the TE10 mode and output through the rectangular waveguide. However, the TE01-TE10 petal-shaped mode converter contains a circular waveguide and three E-plane waveguide power dividers, making the radial size of the overall structure very large. In the application of the high-frequency millimeter-wave band, such a complex structure does not meet the current development trend of device miniaturization and high integration. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a high-frequency millimeter-wave power combiner and mode conversion method based on a diaphragm structure, so as to improve the synthesis efficiency of high-frequency millimeter-wave power, reduce losses, and at the same time improve the integration degree to adapt to the miniaturized structure on the premise of having a wide frequency band.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] The high-frequency millimeter-wave power combiner based on the diaphragm structure includes an N-way power combining cavity, a frustum coaxial integrated module, and a diaphragm type mode converter;

[0008] The N-way power combining cavity includes a rectangular input waveguide layer, a radial stepped waveguide layer, and a circular waveguide arranged in sequence; the frustum coaxial integrated module includes a matching frustum and a coaxial inner conductor, and one end of the coaxial inner conductor is connected to the matching frustum; the diaphragm type mode converter includes a mode conversion diaphragm and a circular-rectangular transition waveguide;

[0009] The frustum coaxial integrated module is installed in the N-way power combining cavity. The coaxial inner conductor and the circular waveguide form a coaxial waveguide, and pass through the circular waveguide to access the mode conversion diaphragm. The mode conversion diaphragm can convert both the main mode TEM and the higher-order mode TE11 in the coaxial waveguide into the TE10 mode.

[0010] The N-way power combining cavity is connected to N input ports, and the diaphragm type mode converter is connected to one output port.

[0011] In one embodiment, according to the number of ladder levels, the radial ladder waveguide layer is divided into M layers along the radial direction, that is, each layer corresponds to a ladder, and the layers are stacked together to form a "ladder structure", and vias are provided in each layer. The matching frustum has K levels to improve the impedance matching in the radial waveguide and improve the power combining efficiency. The frustum coaxial integrated module passes through the radial ladder waveguide layer. One end of the coaxial inner conductor is connected to the matching frustum, and the other end accesses the mode conversion diaphragm. For example, M = 3 and K = 3, that is, a three-stage matching frustum and a three-layer radial ladder waveguide layer.

[0012] In one embodiment, the frustum coaxial integrated module further includes: an L-level fixed frustum; there are L-level fixed threaded grooves in the rectangular input waveguide layer; the L-level fixed frustum is installed and fixed in the L-level fixed threaded grooves. For example, L = 2, that is, two-level fixed frustums and two-level fixed threaded grooves. The two-level fixed frustums match the two-level fixed threaded grooves to fix the bottom of the frustum coaxial integrated module in the N-way power combining cavity, ensuring the stability of the bottom end of the frustum coaxial integrated module and improving the structural stability.

[0013] In one embodiment, there is a smooth round hole in the mode conversion diaphragm that matches the outer diameter of the coaxial inner conductor. The coaxial inner conductor is inserted into the smooth round hole and fixed, fixing the frustum coaxial integrated module in the diaphragm type mode converter.

[0014] In one embodiment, the N-way power combining cavity and the diaphragm type mode converter are connected in sequence and fixed by screw assembly; the two-level fixed frustums match the two-level fixed threaded grooves in the N-way power combining cavity to fix the bottom of the frustum coaxial integrated module in the N-way power combining cavity; the coaxial inner conductor matches the smooth round hole in the diaphragm type mode converter to fix the top of the frustum coaxial integrated module in the diaphragm type mode converter.

[0015] For example, the N-way power combining cavity is processed by a layered structure, including a rectangular input waveguide layer, a radial ladder waveguide layer, and a circular waveguide. The frustum coaxial integrated module integrates a two-level fixed frustum structure, a three-level frustum matching structure, and a coaxial inner conductor, and is processed by an integrated structure.

[0016] In one embodiment, N≥4.

[0017] In one embodiment, the circular-rectangular transition waveguide includes a first circular-rectangular transition waveguide and a second circular-rectangular transition waveguide symmetrically arranged on both sides of the mode conversion diaphragm.

[0018] In one embodiment, the signal modes of the input port and the output port are TE10. The mode conversion diaphragm can convert the TEM mode of the coaxial waveguide into the TE10 mode, while improving the loss caused by the discontinuity between the coaxial waveguide and the diaphragm-type mode converter.

[0019] In one embodiment, the axial length of the coaxial waveguide is about 1.5λg - 2λg, where λg is the waveguide wavelength.

[0020] The mode conversion method of the high-frequency millimeter-wave power combiner based on the diaphragm structure of the present invention is as follows:

[0021] In an ideal situation, the rectangular input waveguide layer receives N paths of TE10 mode signals with equal amplitude and the same phase. The electromagnetic field passes through the radial stepped waveguide layer, and the transmission direction changes from vertical to radial. In the radial stepped waveguide, combined with the matching frustum in the frustum coaxial integrated module, the N paths of signals are combined from the TE10 mode into the TEM mode, and are transmitted to the mode conversion diaphragm through the coaxial waveguide. The signal mode is first converted into the TE11 mode and then into the TE10 mode, and finally the combined signal of the TE10 mode is output.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) The TE01-TE10 petal-type mode converter requires four paths of TE10 signals with a phase difference of 90° input, and at least includes a circular waveguide and two E-plane waveguide power dividers, making the radial size of the overall structure large. The present invention uses a diaphragm-type mode converter to replace the traditional TE01-TE10 petal-type mode converter, directly converting the signal from the TE10 mode to the TEM mode in the vertical direction, with a simple structure and a reduced radial volume of the device. For example, for a circular waveguide, the radius R1 of the circular waveguide satisfying the TE01 transmission condition is R1≥0.61λ0, and for an E-plane power divider, the radial length L1 satisfying the phase matching requirement of the power divider is L1≥0.5λ0, and the overall radial size is about D1 = 2*R1 + 2*L1 = 2.22λ0; while for a coaxial waveguide, the mode conversion diaphragm can effectively convert the TEM and TE11 modes in the coaxial waveguide. Under the condition of suppressing the transmission of the high-order mode TM01 mode, the outer conductor radius of the coaxial waveguide is 0.383λ0≥R2≥0.293λ0, and the maximum overall radial size is about D2 = 2*R2≈0.77λ0, and the radial size can be reduced by about 65%, where λ0 is the free space wavelength.

[0024] 2) The present invention inputs signals vertically through a rectangular input waveguide layer, so that both the input and output ports are in the axial direction, improving the integration of the device.

[0025] 3) The M-level matching frustum and mode conversion diaphragm in the present invention reduce the loss problem caused by mode conversion discontinuity. Specifically: in the radial waveguide, N TE10 signals are synthesized into a TEM signal, resulting in a mode conversion. The electric field distribution of the TE10 mode is mainly concentrated on the wide side of the waveguide, while in the radial waveguide, this distribution will gradually change to the uniform electric field distribution of the TEM mode. Therefore, a matching frustum is needed to reduce the reflection and loss of electromagnetic waves; in the mode converter, the TEM mode signal needs to be converted into a TE10 signal. The mode conversion diaphragm adopts a stepped gradient structure. By gradually changing the size of the diaphragm, the transition from the coaxial line to the rectangular waveguide becomes smoother, reducing the reflection and loss caused by impedance mismatch, making the overall power combiner have the performance of broadband, low loss and high synthesis efficiency.

[0026] 4) The present invention adopts a structural design that combines module layering and module integration, reducing the processing difficulty of the inner conductor of the coaxial line in the high-frequency band, and the overall device has good stability. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the power combiner of the present invention.

[0028] Figure 2 is a schematic structural diagram of the frustum coaxial integrated module in the power combiner of the present invention.

[0029] Figure 3 is an assembled sectional view of the N-way power synthesis cavity and the diaphragm type mode converter in the power combiner of the present invention.

[0030] Figure 4 is a graph of the return loss of ports P1 - P8 and the combined power of port P0 of the power combiner embodiment (N = 8) of the present invention.

[0031] Figure 5 is a phase diagram of ports P1 - P8 of the power combiner embodiment (N = 8) of the present invention. Detailed Embodiments

[0032] The present invention will be further described below in conjunction with the drawings through specific power synthesis embodiments.

[0033] As described above, the existing high-frequency millimeter-wave mode conversion structures are relatively large and have low integration. Therefore, it is necessary to propose a power combining architecture with a wide frequency band, high synthesis efficiency, low loss, compact volume, and high integration, and to explore a mode conversion method suitable for miniaturized structures. The present invention realizes broadband and low-loss power combining through an M-stage matching frustum and a mode conversion diaphragm, and has the characteristics of simple structure, miniaturization, and high integration, and is applicable to high-frequency millimeter-wave systems.

[0034] As Figure 1 shown, the high-frequency millimeter-wave power combiner based on the diaphragm structure mainly consists of an N-way power combining cavity, a diaphragm-type mode converter, and a frustum coaxial integrated module 105. The number of input paths N of the power combiner is 8, and P1, P2,..., P8 are defined as input ports, and P0 is the output port.

[0035] As Figure 1 、 Figure 3 shown, the 8-way power combining cavity includes a rectangular input waveguide layer 101, a first radial stepped waveguide layer 102, a second radial stepped waveguide layer 103, a third radial stepped waveguide layer 104, and a circular waveguide 106, that is, the number of layers of the radial stepped waveguide layer in this embodiment is M = 3. Among them, the rectangular input waveguide layer 101 is connected to 8 input ports and has L-level fixed thread grooves 301 to ensure the stability of the bottom end of the frustum coaxial integrated module. Considering processing convenience and stable reliability, L = 2 is taken in this embodiment, and the value of L can be adjusted according to requirements. The radial stepped waveguide layer is divided into 3 layers along the radial direction according to the number of steps. The rectangular input waveguide layer 101, the first radial stepped waveguide layer 102, the second radial stepped waveguide layer 103, the third radial stepped waveguide layer 104, and the circular waveguide 106 are sequentially fixed by screws.

[0036] As Figure 1 、 Figure 3 shown, the diaphragm-type mode converter includes: a mode conversion diaphragm 107 and a circular-rectangular transition waveguide. Among them, the mode conversion diaphragm 107 has a smooth round hole 302 to fix the top of the frustum coaxial integrated module 105; the circular-rectangular transition waveguide is divided into upper and lower parts with the mode conversion diaphragm 107 as the boundary, namely the first circular-rectangular transition waveguide 108 and the second circular-rectangular transition waveguide 109, and is assembled and fixed to the mode conversion diaphragm 107 by screws, and finally connected to 1 output port P0.

[0037] As Figure 2As shown, the frustum coaxial integrated module 105 includes two - stage fixed frustums, three - stage matching frustums, and a coaxial inner conductor 206. That is, in this embodiment, the number of stages of the matching frustums is K = 3. Among them, the two - stage fixed frustums are the first - stage fixed frustum 201 and the second - stage fixed frustum 202, which match the two - stage fixed thread grooves 301 in the 8 - way power combining cavity, fix the bottom of the frustum coaxial integrated module 105 in the cavity, and improve the stability of the structure; the three - stage matching frustums are the first - stage matching frustum 203, the second - stage matching frustum 204, and the third - stage matching frustum 205, which improve the impedance matching in the radial waveguide and increase the power combining efficiency.

[0038] The coaxial inner conductor 206 in the frustum coaxial integrated module 105 and the circular waveguide 106 in the 8 - way power combining cavity together form a coaxial waveguide; the mode - conversion diaphragm 107 in the diaphragm - type mode converter converts the TEM mode of the signal transmitted in the coaxial waveguide into the TE10 mode, and improves the loss caused by the discontinuity between the coaxial waveguide and the diaphragm - type mode converter.

[0039] In the above - mentioned implementation method, the high - frequency millimeter - wave power combiner based on the diaphragm structure can be processed by a layered structure, including a rectangular input waveguide layer 101, a first radial stepped waveguide layer 102, a second radial stepped waveguide layer 103, a third radial stepped waveguide layer 104, and a circular waveguide 106; the frustum coaxial integrated module 105 is processed by an integrated structure, including a two - stage fixed frustum structure, a three - stage frustum matching structure, and a coaxial inner conductor 206. The 8 - way power combining cavity is connected to the diaphragm - type mode converter and fixed by screw assembly; the two - stage fixed frustums match the two - stage fixed thread grooves 301 in the 8 - way power combining cavity, and fix the bottom of the frustum coaxial integrated module 105 in the power combining cavity; the coaxial inner conductor 206 matches the smooth round hole 302 in the diaphragm - type mode converter, and fixes the top of the frustum coaxial integrated module 105 in the diaphragm - type mode converter.

[0040] The mode - conversion method of the power combiner of the present invention is as follows: The rectangular input waveguide layer 101 receives 8 TE10 - mode signals with equal amplitude and the same phase under ideal conditions. The electromagnetic field passes through the radial stepped waveguides 102 - 104, and the transmission direction changes from vertical to radial; in the radial stepped waveguides 102 - 104, combined with the three - stage matching frustums 203 - 205 in the frustum coaxial integrated module 105, the 8 signals are combined from the TE10 mode into the TEM mode; the TEM mode is transmitted in the coaxial waveguide with an axial length of about 1.5λg - 2λg formed by the coaxial inner conductor 206 and the circular waveguide 106. Through the diaphragm - type mode converter 107 - 109, the signal mode is first converted into the TE11 mode and then into the TE10 mode, and finally the combined signal of the TE10 mode is output.

[0041] In addition, by docking the 8 input ports of a pair of broadband radial power combiners, the distribution and synthesis of signal energy can be achieved, which can be widely applied to high-frequency millimeter-wave power synthesis amplifiers.

[0042] In this embodiment, as Figure 1 shown in the structure, the power combiner operates in the D band, with a working frequency of 121 - 165 GHz. The input ports are P1 - 8, and the output port is P0. The input and output ports are all standard rectangular waveguides of BJ1400, with an inner cross-sectional size of 1.651 mm × 0.8255 mm. The diameter of the coaxial inner conductor 206 is 0.36 mm, and the diameter of the circular waveguide 106 is 1.74 mm. Eight signals with equal amplitude and in-phase are input from ports P1 - 8, and are combined into TEM mode in the radial stepped waveguides 102 - 104, and are transmitted through a coaxial waveguide with an axial length of about 1.5λg - 2λg formed by the coaxial inner conductor 206 and the circular waveguide 106, and are converted into TE10 mode output through the diaphragm-type mode converters 107 - 109. In this example, the input ports are centrosymmetric about the center of the coaxial inner conductor 206, with good amplitude-phase balance. The S parameters of each port are as Figure 4 shown. In the range of 122 - 162 GHz, when the input power of ports P1 - 8 is 0 dBm, the return loss of each input port is better than 13 dB, the amplitude consistency is good, and the synthesis efficiency reaches 96%. The phases of ports P1 - 8 are as Figure 5 shown. In the range of 110 - 162 GHz, there is good phase consistency.

[0043] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art can understand that: without departing from the spirit and scope of the present invention and the appended claims, various substitutions and modifications are possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection claimed by the present invention shall be defined by the scope defined in the claims.

Claims

1. A high-frequency millimeter-wave power synthesizer based on a diaphragm structure, characterized in that: It comprises an N-way power synthesis cavity, a truncated cone coaxial integrated module (105) and a diaphragm type mode converter; The N-channel power synthesis cavity comprises a rectangular input waveguide layer (101), a radial step waveguide layer and a circular waveguide (106) arranged in sequence; the truncated cone coaxial integrated module (105) comprises a matching truncated cone and a coaxial inner conductor (206), one end of the coaxial inner conductor (206) being connected to the matching truncated cone; the diaphragm-type mode converter comprises a mode conversion diaphragm (107) and a circular-rectangular transition waveguide; The truncated cone coaxial integrated module (105) is installed in the N-way power synthesis cavity, wherein the coaxial inner conductor (206) and the circular waveguide (106) form a coaxial waveguide and pass through the circular waveguide (106) to access the mode conversion diaphragm (107); The N-way power synthesis cavity is connected to N input ports, and the diaphragm type mode converter is connected to one output port.

2. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 1, characterized in that: According to the number of steps, the radial step waveguide layer is divided into M layers along the radial direction, the matching truncated cone has K levels, the truncated cone coaxial integrated module (105) passes through the radial step waveguide layer, one end of the coaxial inner conductor (206) is connected to the matching truncated cone, and the other end is connected to the mode conversion diaphragm (107).

3. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 2, characterized in that: The radial step waveguide layer is divided into three layers along the radial direction, and the matching frustum has three levels.

4. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 1, 2 or 3, characterized in that: The truncated cone coaxial integrated module (105) further comprises: an L-level fixed truncated cone; an L-level fixed thread groove (301) is provided in the rectangular input waveguide layer (101); and the L-level fixed truncated cone is installed and fixed in the L-level fixed thread groove (301).

5. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 1, characterized in that: The mode conversion diaphragm (107) has a smooth circular hole (302) matching the outer diameter of the coaxial inner conductor (206), and the coaxial inner conductor (206) is inserted into the smooth circular hole (302) and fixed.

6. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 1, characterized in that: N≥4。 7. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 1, characterized in that: The circular-rectangular transition waveguide comprises a first circular-rectangular transition waveguide (108) and a second circular-rectangular transition waveguide (109) which are symmetrically arranged on both sides of the mode conversion membrane (107).

8. The high-frequency millimeter-wave power synthesizer based on a diaphragm structure according to claim 1, characterized in that: The axial length of the coaxial waveguide is about 1.5λg to 2λg, where λg is the waveguide wavelength.

9. A mode conversion method using a high frequency millimeter wave power synthesizer based on a diaphragm structure according to any one of claims 1 to 8, characterized in that: The rectangular input waveguide layer (101) receives N TE10 mode signals of equal amplitude and same phase. The electromagnetic field passes through the radial step waveguide layer, and the transmission direction is changed from vertical to radial. In combination with the matching frustum, the N signals are combined from the TE10 mode to the TEM mode, and transmitted to the mode conversion diaphragm (107) via the coaxial waveguide. The signal mode is first converted into the TE11 mode and then into the TE10 mode, and finally a synthetic signal of the TE10 mode is output.

10. The mode conversion method according to claim 9, characterized in that: The mode conversion diaphragm (7) is used to convert both the main mode TEM and the high-order mode TE11 in the coaxial waveguide into the TE10 mode.

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