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

Abstract

This invention discloses a high-frequency millimeter-wave power combiner and mode conversion method based on a diaphragm structure. The invention includes an N (N≥4)-channel power combining cavity, a diaphragm-type mode converter, and a coaxial integrated frustum module. The power combining cavity consists of a rectangular input waveguide layer, a radial stepped waveguide layer, and a circular waveguide layer. The diaphragm-type mode converter consists of a mode conversion diaphragm and a circular-rectangular transition waveguide. The coaxial integrated frustum module includes a two-stage fixed frustum, a three-stage matching frustum, and a coaxial inner conductor. Multiple TE10 mode signals are input from the rectangular input waveguide, combined into TEM modes via the radial stepped waveguide, converted back to TE10 modes by the diaphragm-type mode converter, and finally output from the circular-rectangular transition waveguide. This invention achieves broadband, low-loss power combining through a three-stage matching frustum and a mode conversion diaphragm, featuring simple structure, miniaturization, and high integration, making it suitable for high-frequency millimeter-wave systems.

Description

Technical Field

[0001] This invention relates to the field of high-frequency millimeter-wave power combining technology, and in particular to a high-frequency millimeter-wave power combiner and mode conversion method based on a diaphragm structure. Background Technology

[0002] In high-frequency millimeter-wave communication systems, power amplifiers play a crucial role, serving as key components to ensure signal coverage over long distances and through obstacles. The primary function of a power amplifier is to increase the power of the transmitted signal, enabling it to maintain sufficient strength over long distances to overcome path loss and interference, thus ensuring signal reliability and stability. Because high-frequency millimeter-wave signals encounter various losses during transmission, including atmospheric absorption, rain attenuation, and obstruction from physical obstacles such as buildings, a high-performance power amplifier is essential for maintaining the integrity of the communication link.

[0003] Current high-frequency millimeter-wave power combining technologies mainly include hierarchical power combining, waveguide-based spatial combining, and free-space combining. Hierarchical power combiners have a simple design structure, but as the number of combining stages increases and the transmission line length length increases, they suffer from problems such as high loss, low combining efficiency, large size, and low integration. Free-space combining technology, based on the interferometric combining of array radiated waves in free space, has the advantages of high power, multiple paths, and direct transmission. However, because its implementation architecture is similar to array antenna technology, it is mainly suitable for directional transmission scenarios and cannot simultaneously meet the requirements of broadband, high combining efficiency, and high power. In contrast, waveguide-based spatial combining technology utilizes symmetrical electromagnetic field modes in multimode waveguides to directly combine signals from multiple symmetrical paths, exhibiting efficient power combining capabilities, 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 conversion between different modes. For example, a 16-way power combiner operating in the Ku band was 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, [sl], v.89, n.3, p.1, 2018.]. The core of this combiner is the TE01-TE10 petal-shaped mode converter. The design first inputs 16 equal-amplitude and in-phase signals, which are then synthesized into the TE01 mode via a radial waveguide and a matching frustum. The TE01 mode is transmitted in the circular waveguide, and the petal-shaped mode converter converts the TE01 mode into the TE10 mode, which is then output from a rectangular waveguide. However, the TE01-TE10 petal-shaped mode converter includes a circular waveguide and three E-plane waveguide power dividers, resulting in a very large radial dimension of the overall structure. In high-frequency millimeter-wave applications, this complex structure does not meet the current trend towards miniaturization and high integration of devices. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-frequency millimeter-wave power synthesizer and mode conversion method based on a diaphragm structure, so as to improve the synthesis efficiency of high-frequency millimeter-wave power and reduce loss while improving integration to adapt to miniaturized structures, under the premise of having a wide bandwidth.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

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

[0008] The N-channel power combining cavity includes a rectangular input waveguide layer, a radial stepped waveguide layer, and a circular waveguide arranged sequentially; the frustum-coaxial integrated module includes a matching frustum and a coaxial inner conductor, with one end of the coaxial inner conductor 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-channel power combining cavity, wherein the coaxial inner conductor and the circular waveguide form a coaxial waveguide, and the coaxial inner conductor passes through the circular waveguide and connects to the mode conversion diaphragm; the mode conversion diaphragm can convert the dominant mode TEM and the higher-order mode TE11 in the coaxial waveguide into the TE10 mode;

[0010] The N-channel 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, the radially stepped waveguide layer is divided into M layers along the radial direction, according to the number of steps. Each layer corresponds to one step, and the layers are stacked together to form a "stepped structure," with vias provided in each layer. The matching frustum has K levels to improve impedance matching in the radial waveguide and increase power combining efficiency. The coaxial integrated module of the frustum passes through the radially stepped waveguide layer. One end of the coaxial inner conductor is connected to the matching frustum, and the other end is connected to the mode conversion diaphragm. For example, M=3, K=3, i.e., three matching frustums and three radially stepped waveguide layers.

[0012] In one embodiment, the frustum-shaped coaxial integrated module further includes: an L-stage fixed frustum; an L-stage fixed threaded groove in the rectangular input waveguide layer; and the L-stage fixed frustum is installed and fixed in the L-stage fixed threaded groove. For example, L=2, i.e., two stages of fixed frustums and two stages of fixed threaded grooves. The two stages of fixed frustums match the two stages of fixed threaded grooves, fixing the bottom of the frustum-shaped coaxial integrated module in the N-channel power combining cavity, ensuring the stability of the bottom of the frustum-shaped coaxial integrated module and improving the stability of the structure.

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

[0014] In one embodiment, the N-channel power combining cavity is sequentially connected to the diaphragm-type mode converter and fixed by screw assembly; the two-stage fixed frustum matches the two-stage fixed threaded groove in the N-channel power combining cavity to fix the bottom of the frustum coaxial integrated module in the N-channel power combining cavity; the coaxial inner conductor matches the smooth circular 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-channel power combining cavity is fabricated using a layered structure, including a rectangular input waveguide layer, a radial stepped waveguide layer, and a circular waveguide. The frustum-coaxial integrated module integrates a two-stage fixed frustum structure, a three-stage frustum matching structure, and a coaxial inner conductor, and is fabricated using 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 mode of the input and output ports is TE10. The mode conversion diaphragm can convert the coaxial waveguide TEM mode to the TE10 mode, while improving the losses 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 approximately 1.5λg to 2λg, where λg is the waveguide wavelength.

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

[0021] Ideally, the rectangular input waveguide layer receives N equal-amplitude and in-phase TE10 mode signals. 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 signals are combined from TE10 mode to TEM mode. The signal is then transmitted to the mode conversion diaphragm via the coaxial waveguide. The signal mode is first converted to TE11 mode and then to TE10 mode, and finally the synthesized signal of TE10 mode is output.

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

[0023] 1) The TE01-TE10 petal-shaped mode converter requires four TE10 signal inputs with a phase difference of 90°, and includes at least one circular waveguide and two E-plane waveguide power dividers, resulting in a large radial dimension of the overall structure. This invention replaces the traditional TE01-TE10 petal-shaped mode converter with a diaphragm-type mode converter, which directly converts the signal from TE10 to TEM mode in the vertical direction, resulting in a simpler structure and a smaller radial volume of the device. For example, for a circular waveguide, the radius R1 ≥ 0.61λ0 satisfies the TE01 transmission condition. For an E-plane power divider, the radial length L1 ≥ 0.5λ0 satisfies the phase matching requirement of the power divider, and the overall radial dimension is approximately D1 = 2*R1 + 2*L1 = 2.22λ0. 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 higher-order mode TM01, the outer conductor radius of the coaxial waveguide is 0.383λ0 ≥ R2 ≥ 0.293λ0, and the maximum overall radial dimension is approximately D2 = 2*R2 ≈ 0.77λ0. The radial dimension can be reduced by about 65%, where λ0 is the free space wavelength.

[0024] 2) This invention uses a rectangular input waveguide layer to vertically input signals, so that both the input and output ports are in the axial direction, thus improving the integration of the device.

[0025] 3) The M-level matching frustum and mode conversion diaphragm in this 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 transition. The electric field distribution of the TE10 mode is mainly concentrated on the wide side of the waveguide. However, in the radial waveguide, this distribution gradually transforms into a uniform electric field distribution of the TEM mode. Therefore, a matching frustum is needed to reduce electromagnetic wave reflection and loss. 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 is smoother, reducing reflection and loss caused by impedance mismatch. This gives the overall power combiner broadband, low loss, and high combining efficiency.

[0026] 4) The present invention adopts a structural design that combines modular layering and modular integration, which reduces the difficulty of processing the inner conductor of the coaxial line in the high-frequency band and the device as a whole has good stability. Attached Figure Description

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

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

[0029] Figure 3 This is a cross-sectional view of the N-channel power combining cavity and diaphragm-type mode converter assembled in the power combiner of the present invention.

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

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

[0032] The present invention will be further illustrated below with reference to the accompanying drawings and specific power combining embodiments.

[0033] As mentioned earlier, existing high-frequency millimeter-wave mode conversion structures are large and have low integration. Therefore, it is necessary to propose a power combining architecture with wide bandwidth, high combining efficiency, low loss, compact size, and high integration, and to explore a mode conversion method suitable for miniaturized structures. This invention achieves broadband, low-loss power combining through an M-class matching frustum and a mode conversion diaphragm, featuring simple structure, miniaturization, and high integration, making it suitable for high-frequency millimeter-wave systems.

[0034] like Figure 1 As shown, this high-frequency millimeter-wave power combiner based on a diaphragm structure mainly consists of N power combining cavities, a diaphragm-type mode converter, and a frustum-type coaxial integrated module 105. The power combiner has N=8 input channels, with P1, P2, ..., P8 defined as input ports and P0 as an output port.

[0035] like Figure 1 , Figure 3 As shown, the 8-channel 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. In this embodiment, the number of radial stepped waveguide layers is M=3. The rectangular input waveguide layer 101 connects to the 8 input ports and has an L-level fixing threaded groove 301 to ensure the stability of the bottom of the coaxial integrated frustum module. Considering processing convenience and stability, this embodiment uses L=2, but the value of L can be adjusted according to requirements. The radial stepped waveguide layer is divided into 3 layers radially 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 with screws.

[0036] like Figure 1 , Figure 3 As shown, the diaphragm-type mode converter includes a mode conversion diaphragm 107 and a circular-rectangular transition waveguide. The mode conversion diaphragm 107 has a smooth circular hole 302 to secure the top of the frustum-shaped coaxial integrated module 105. The circular-rectangular transition waveguide is divided into upper and lower parts by the mode conversion diaphragm 107, namely a first circular-rectangular transition waveguide 108 and a second circular-rectangular transition waveguide 109, which are assembled and fixed to the mode conversion diaphragm 107 by screws and ultimately connected to an output port P0.

[0037] like Figure 2As shown, the frustum-coaxial integrated module 105 includes two-stage fixed frustums, three-stage matching frustums, and a coaxial inner conductor 206. In this embodiment, the number of matching frustum stages is K = 3. The two-stage fixed frustums, namely the first-stage fixed frustum 201 and the second-stage fixed frustum 202, match the two-stage fixed threaded grooves 301 in the 8-channel power combining cavity, fixing the bottom of the frustum-coaxial integrated module 105 in the cavity and improving structural stability. The three-stage matching frustums, namely the first-stage matching frustum 203, the second-stage matching frustum 204, and the third-stage matching frustum 205, improve impedance matching in the radial waveguide and increase power combining efficiency.

[0038] The coaxial inner conductor 206 in the frustum coaxial integrated module 105 and the circular waveguide 106 in the 8-channel power combining cavity together constitute 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, improving the loss caused by the discontinuity between the coaxial waveguide and the diaphragm-type mode converter.

[0039] In the above implementation method, the high-frequency millimeter-wave power combiner based on the diaphragm structure can be fabricated in 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 fabricated in an integrated structure, including a two-stage fixed frustum structure, a three-stage frustum matching structure, and a coaxial inner conductor 206. The 8-channel power combining cavity is connected to the diaphragm-type mode converter and fixed by screw assembly; the two-stage fixed frustum matches the two-stage fixed threaded grooves 301 in the 8-channel power combining cavity, fixing the bottom of the frustum coaxial integrated module 105 in the power combining cavity; the coaxial inner conductor 206 matches the smooth circular hole 302 in the diaphragm-type mode converter, fixing 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: Under ideal conditions, the rectangular input waveguide layer 101 receives 8 TE10 mode signals with equal amplitude and phase. The electromagnetic field passes through the radial stepped waveguide 102-104, and the transmission direction changes from vertical to radial. In the radial stepped waveguide 102-104, combined with the three-stage matching frustum 203-205 in the frustum coaxial integrated module 105, the 8 signals are combined from TE10 mode to TEM mode. The TEM mode is transmitted in the coaxial waveguide with an axial length of about 1.5λg to 2λg, which is composed of the coaxial inner conductor 206 and the circular waveguide 106. Through the diaphragm-type mode converter 107-109, the signal mode is first converted to TE11 mode and then to TE10 mode, and finally the synthesized signal of TE10 mode is output.

[0041] In addition, by connecting the eight input ports of a pair of broadband radial power combiners, signal energy distribution and synthesis can be achieved, which can be widely used in high-frequency millimeter-wave power combining amplifiers.

[0042] In this embodiment, as Figure 1 The structure shown illustrates a power combiner operating in the D-band at frequencies of 121–165 GHz. It has input ports P1–8 and an output port P0. Both input and output ports utilize BJ1400 standard rectangular waveguides with an inner cross-sectional dimension of 1.651 mm × 0.8255 mm. The coaxial inner conductor 206 has a diameter of 0.36 mm, and the circular waveguide 106 has a diameter of 1.74 mm. Eight equal-amplitude, in-phase signals are input through ports P1–8 and combined into TEM modes in radial stepped waveguides 102–104. These TEM modes are then transmitted through a coaxial waveguide with an axial length of approximately 1.5λg–2λg, formed by the coaxial inner conductor 206 and the circular waveguide 106, and converted into TE10 mode outputs via diaphragm-type mode converters 107–109. In this example, each input port is centrally symmetrical about the coaxial inner conductor 206, exhibiting good amplitude and phase balance. The S-parameters of each port are as follows: Figure 4 As shown, within the 122-162 GHz range, 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 phase of ports P1-8 is as follows: Figure 5 As shown, it exhibits good phase consistency within the 110-162 GHz range.

[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 will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. A high frequency millimeter wave power combiner based on a diaphragm structure, characterized in that, It includes an N-channel power combining cavity, a frustum coaxial integrated module (105), and a diaphragm-type mode converter; The N-channel power combining cavity includes a rectangular input waveguide layer (101), a radial stepped waveguide layer, and a circular waveguide (106) arranged sequentially; the frustum coaxial integrated module (105) includes a matching frustum and a coaxial inner conductor (206), one end of which is connected to the matching frustum; the diaphragm-type mode converter includes a mode conversion diaphragm (107) and a circular-rectangular transition waveguide; 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 and fixed in the smooth circular hole (302); the circular-rectangular transition waveguide includes a first circular-rectangular transition waveguide (108) and a second circular-rectangular transition waveguide (109) symmetrically arranged on both sides of the mode conversion diaphragm (107). The frustum coaxial integrated module (105) is installed in the N-channel power combining cavity, wherein the coaxial inner conductor (206) and the circular waveguide (106) form a coaxial waveguide and pass through the circular waveguide (106) to connect to the mode conversion diaphragm (107). The N-channel power combining cavity is connected to N input ports, and the diaphragm-type mode converter is connected to one output port.

2. The membrane-based high-frequency millimeter-wave power combiner of claim 1, wherein, According to the number of steps, the radial stepped waveguide layer is divided into M layers along the radial direction, the matching frustum has K levels, the frustum coaxial integrated module (105) passes through the radial stepped waveguide layer, one end of the coaxial inner conductor (206) is connected to the matching frustum, and the other end is connected to the mode conversion diaphragm (107).

3. The membrane-based high-frequency millimeter-wave power combiner of claim 2, wherein, The radial stepped waveguide layer is divided into three radial layers, and the matching frustum has three levels.

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

5. The diaphragm structure based high frequency millimeter wave power combiner of claim 1, wherein, N≥4。 6. The membrane-based high-frequency millimeter-wave power combiner of claim 1, wherein, The axial length of the coaxial waveguide is 1.5λg~2λg, where λg is the waveguide wavelength.

7. A mode conversion method using a high-frequency millimeter-wave power combiner based on a diaphragm structure as described in any one of claims 1 to 6, characterized in that: The rectangular input waveguide layer (101) receives N equal-amplitude and in-phase TE10 mode signals. The electromagnetic field passes through the radial stepped waveguide layer, and the transmission direction changes from vertical to radial. Combined with the matching frustum, the N signals are combined from TE10 mode to TEM mode. The signal is then transmitted to the mode conversion diaphragm (107) via a coaxial waveguide. The signal mode is first converted to TE11 mode and then to TE10 mode, and finally the synthesized signal of TE10 mode is output.

8. The mode conversion method of claim 7, wherein: The mode conversion diaphragm (107) is used to convert both the primary mode TEM and the higher-order mode TE11 in the coaxial waveguide into the TE10 mode.

Images