Waveguide coaxial filter, design method thereof and low-temperature receiver

Abstract

The invention discloses a waveguide coaxial filter, a design method thereof and a low-temperature receiver. The waveguide coaxial filter comprises a waveguide input port used for inputting an electromagnetic wave signal; the waveguide filtering structure is used for transmitting the electromagnetic wave signal in a waveguide transmission line mode and filtering a frequency spectrum signal with a set frequency in the electromagnetic wave signal; the waveguide coaxial conversion structure is arranged in the output port surface cavity of the waveguide filtering structure and is used for realizing mode conversion and impedance matching of the waveguide transmission line and the coaxial transmission line so as to convert a waveguide transmission line mode signal into a coaxial transmission line mode signal; and the coaxial output port is used for being connected with a coaxial transmission line so as to output a coaxial transmission line mode signal. A waveguide filtering structure and a waveguide coaxial conversion structure are integrally designed, so that the insertion loss performance is optimized on the whole, the size and weight of the device are greatly reduced, interconnection of systems and stability of the system structure are facilitated, and the low-temperature receiving device can be applied to low-temperature receivers in the aerospace field.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave power devices, and in particular to an integrated waveguide coaxial filter having both waveguide filtering function and waveguide coaxial conversion function, a design method thereof, and a cryogenic receiver containing the waveguide coaxial filter. Background Art

[0002] Microwave filter devices are important devices in communication links, and their performance can directly affect the performance of communication transmission. Radio cryogenic receivers are used to receive weak electromagnetic wave signals in space and perform low-noise amplification. Commercial amplifiers generally cannot perfectly match the receiving frequency of the developed receivers, and are generally slightly larger than the receiving frequency range of the receivers. In order to deal with the interference of unnecessary spectrum signals to useful signals caused by amplification, microwave filters have been widely used in communication systems.

[0003] According to the type of transmission line, microwave filters are divided into coaxial transmission lines, microstrip lines, metal waveguides, substrate integration and other forms. Microstrip lines and substrate integration are based on dielectric substrates, and metal waveguides are based on hollow metal tubes of fixed size. Waveguide transmission lines have the advantages of low insertion loss and high stability, and are widely used in high-frequency systems. Coaxial transmission lines are usually used for signal transmission in low-frequency bands.

[0004] As the name implies, waveguide filters achieve filtering functions through waveguide transmission lines. Waveguide transmission lines are metal hollow tube structures. Compared with microstrip transmission lines and coaxial transmission lines, waveguide transmission lines have better environmental adaptability and structural stability. At the same time, waveguide transmission lines have better transmission performance for the transmission of electromagnetic wave signals.

[0005] There are generally two ways to implement waveguide filters:

[0006] (1) Using the cutoff characteristics of the waveguide transmission line to achieve filtering function, such as Figure 1 As shown. This is the simplest way to achieve filtering function. The cutoff characteristic of the waveguide means that the waveguide can effectively transmit electromagnetic waves above a specific frequency, and below this specific frequency, the electromagnetic waves cannot effectively propagate in the waveguide. This specific frequency is called the cutoff frequency. When the frequency of the electromagnetic wave is lower than the cutoff frequency, the waveguide exhibits a strong attenuation characteristic, which can be used to realize a high-pass filter.

[0007] (2) The cutoff characteristics are realized by introducing a transmission zero point by loading a resonant diaphragm, such as Figure 2 Introducing discontinuities in the waveguide, such as metal columns and diaphragms, realizes transmission zero points, thereby achieving cutoff characteristics.

[0008] Of the two implementations described above, the second implementation can achieve better out-of-band suppression and a smaller structural size than the first implementation, but the insertion loss is higher than the first implementation.

[0009] In the actual application of X-band cryogenic receiver systems, front-end passive devices generally use waveguide transmission lines with low transmission loss for signal transmission. When electromagnetic wave signals are transmitted to cryogenic low-noise amplifiers, signals before 7.2GHz need to be filtered out. The transmission line used by cryogenic low-noise amplifiers is coaxial transmission line, so it is necessary to use an independent waveguide coaxial converter to connect the rectangular waveguide transmission line (TE10 mode) and the coaxial transmission line (TEM mode) to achieve mode conversion and impedance matching, so as to transmit the signal to the subsequent system.

[0010] There are two ways to implement waveguide to coaxial converters:

[0011] (1) End-launch structure, that is, the waveguide input port and the coaxial output port are in the same direction. The end-launch structure is conducive to the interconnection of the system. The coaxial probe is fed into the back wall of the rectangular waveguide to generate excitation, and then the waveguide impedance value is adjusted by loading a multi-section step impedance in the waveguide cavity to eliminate the bad reflection in the band, achieve the matching of the waveguide transmission line and the coaxial transmission line, and obtain excellent signal transmission performance.

[0012] Figure 3 It is a waveguide coaxial converter with a contactless feeding end-launch structure, wherein the waveguide input port 1 and the coaxial output port 2 are in the same direction, and the coaxial output port 2 is not in contact with the multi-section ladder impedance 3 in the waveguide cavity. Figure 3 As shown in A in the figure. This feeding form can achieve a wider working bandwidth and a smaller insertion loss, but this structure requires higher processing accuracy.

[0013] Figure 4 A waveguide-coaxial converter with contact-feed end-launch structure is given, in which the waveguide input port 1 and the coaxial output port 2 are in the same direction, and the coaxial output port 2 is in contact with the multi-section stepped impedance 3 in the waveguide cavity, as shown in FIG. Figure 4 As shown in B. This form of feeding method can bring a bandwidth of 3:1. At the same time, due to the contact method, the structure is relatively stable, but the insertion loss is large.

[0014] (2) 90°angle structure, that is, the waveguide input port and the coaxial output port are in a 90° cross structure. This form of waveguide coaxial converter has a compact structure and low insertion loss, but the input and output ports are not in the same direction, which is not conducive to system cascading and the stability of the system structure.

[0015] Figure 5A waveguide coaxial converter with a 90° angle structure is provided, wherein a coaxial probe 4 is inserted into the wide wall of a rectangular waveguide, an outer conductor 5 of a coaxial transmission line is connected to the wide wall of the rectangular waveguide, and a waveguide input port 1 is at 90° to the coaxial probe 4. The coaxial probe 4 inserted into the waveguide can form a radiating antenna, which can excite electromagnetic waves of the TE10 mode in the waveguide. By adjusting the position and insertion depth of the coaxial probe 4, the conversion between the waveguide transmission line and the coaxial transmission line can be achieved.

[0016] In the current cryogenic receiver system, two discrete components, waveguide filter and waveguide coaxial converter, are used to achieve the signal filtering and transmission line conversion functions. The two components are connected through the screw holes on the flange. This method has the following problems:

[0017] (1) High insertion loss. The performance of the two devices can only be designed separately, and the final insertion loss is the superposition of the insertion losses of the two devices. In addition, the unevenness of the connection surface of the two devices and the deviation during connection will bring additional insertion loss, affecting the performance of the system.

[0018] (2) Large size. The discrete device connection volume is large, occupying the limited system space and weight, and is not conducive to the overall mechanical design of the system. Summary of the invention

[0019] The embodiment of the present application provides a waveguide coaxial filter, which integrates the waveguide filtering structure and the waveguide coaxial conversion structure into an integrated design, thereby solving the problems of large insertion loss and large volume caused by the cascade connection of two discrete components, the waveguide filter and the waveguide coaxial converter, in the prior art.

[0020] In order to solve the above technical problems, in a first aspect, an embodiment of the present application provides a waveguide coaxial filter, comprising:

[0021] A waveguide input port, used for inputting electromagnetic wave signals;

[0022] A waveguide filter structure, used to transmit the electromagnetic wave signal in the form of a waveguide transmission line, and filter the spectrum signal of a set frequency in the electromagnetic wave signal;

[0023] A waveguide-coaxial conversion structure is disposed in the output port cavity of the waveguide filter structure, and is used to realize mode conversion and impedance matching between the waveguide transmission line and the coaxial transmission line, thereby converting the waveguide transmission line mode signal output by the waveguide filter structure into a coaxial transmission line mode signal;

[0024] The coaxial output port is used to connect to the coaxial transmission line to output the coaxial transmission line mode signal.

[0025] Preferably, the waveguide input port, the waveguide filter structure and the waveguide coaxial conversion structure adopt an integrated all-metal tube.

[0026] Preferably, the waveguide filtering structure comprises:

[0027] The first waveguide transition section and the second waveguide transition section are used to achieve filtering effect;

[0028] Waveguide transmission section, used to achieve out-of-band signal suppression;

[0029] The output port cavity is used as the output port of the filtered signal and also as a waveguide cavity for realizing waveguide coaxial conversion;

[0030] The first waveguide transition section, the waveguide transmission section, the second waveguide transition section and the output port cavity are sequentially connected and integrated.

[0031] More preferably, the waveguide transmission section is a curved waveguide structure.

[0032] Preferably, the waveguide coaxial conversion structure comprises a T-shaped impedance matching column, the T-shaped impedance matching column is arranged on the bottom wide wall of the output port surface cavity, and the coaxial output port is arranged on the output end surface of the output port surface cavity;

[0033] The height of the coaxial output port is greater than the height of the T-shaped impedance matching column, so as to satisfy the following requirement: after the coaxial probe of the coaxial transmission line is inserted into the coaxial output port, the coaxial probe is suspended above the T-shaped impedance matching column, and the coaxial probe does not contact the T-shaped impedance matching column.

[0034] Furthermore, the T-shaped impedance matching column includes a first column and a second column, both of which are rectangular columns, and the length and width of the first column are smaller than those of the second column, and the wide side of the first column is connected to the middle of the wide side of the second column and is integrally formed.

[0035] Furthermore, the gap between the coaxial probe and the T-shaped impedance matching column is capacitive, and the coaxial probe, the T-shaped impedance matching column and the bottom wide wall of the output port cavity form a magnetic coupling ring, which completes the conversion of the signal between the waveguide transmission line mode and the coaxial transmission line mode by magnetic coupling.

[0036] Preferably, the first waveguide transition section and the second waveguide transition section are centrally symmetrical structures.

[0037] Preferably, the T-shaped impedance matching column is located in the center of the bottom wide wall width of the output port cavity; the coaxial output port is located in the center of the output end face width of the output port cavity, and the coaxial output port and the waveguide input port are in the same direction.

[0038] In a second aspect, an embodiment of the present application further provides a method for designing a waveguide coaxial filter, comprising the following steps:

[0039] The waveguide filter structure is simulated and optimized using electromagnetic simulation software. In the first simulation, a straight waveguide is used in the waveguide transmission section to determine the dimensions of the first waveguide transition section, the second waveguide transition section, and the straight waveguide. After the simulation optimization is completed, the straight waveguide is replaced with a curved waveguide with the same waveguide dimensions, and the effects of different bending radii on the performance are simulated to determine the optimal bending radius of the curved waveguide.

[0040] After completing the simulation design of the waveguide filter structure, the simulation design of the waveguide coaxial conversion structure was added. The size of the T-type impedance matching column and the height and depth of the coaxial probe were simulated and optimized through electromagnetic simulation software, and the specific size of the waveguide coaxial conversion structure was finally determined.

[0041] The dimensions of the waveguide input port and the coaxial output port are based on the standard waveguide dimensions of the matching mode.

[0042] In a third aspect, the embodiment of the present application further provides a cryogenic receiver, including:

[0043] Antenna, used to collect electromagnetic wave signals in space;

[0044] The waveguide coaxial filter is used to filter the spectrum signal of the set frequency in the electromagnetic wave signal, transmit the electromagnetic wave signal in the form of a waveguide transmission line, and then convert the waveguide transmission line mode signal into a coaxial transmission line mode signal;

[0045] A low-temperature low-noise amplifier, used for receiving the coaxial transmission line mode signal and performing low-noise amplification;

[0046] The waveguide input port of the waveguide coaxial filter is connected to the antenna, and the coaxial output port of the waveguide coaxial filter is connected to the low-temperature low-noise amplifier; the antenna has a waveguide output port, and the low-temperature low-noise amplifier has a coaxial input port, the waveguide input port of the waveguide coaxial filter is connected to the waveguide output port of the antenna, and the coaxial output port of the waveguide coaxial filter is connected to the coaxial input port of the low-temperature low-noise amplifier.

[0047] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0048] 1. The waveguide filter structure and the waveguide coaxial conversion structure are designed in an integrated manner, which optimizes the insertion loss performance as a whole. The insertion loss performance is equivalent to the contribution of only one traditional device, and avoids the additional insertion loss contribution caused by the cascade of two devices.

[0049] 2. The waveguide filter structure and the waveguide coaxial conversion structure are designed in an integrated manner. The rear space of the waveguide filter structure is used to complete the design of the waveguide coaxial conversion structure, which greatly reduces the size and weight of the device, saves limited system space, and avoids the additional space and weight requirements caused by the cascade of two devices. While meeting the performance requirements, it has the advantages of miniaturization and lightweight.

[0050] 3. The waveguide filter structure of the waveguide coaxial filter provided by the present invention integrates the advantages of the two implementation methods of the traditional waveguide filter using the waveguide cutoff characteristics and loading the resonant diaphragm. The present invention uses the cutoff characteristics of the waveguide transmission line itself to achieve the filtering function, and has the advantages of simple structure, high mechanical strength, and low insertion loss. On this basis, the form of curved waveguide is innovatively added to further reduce the size, thereby better realizing the miniaturization of the device.

[0051] 4. The waveguide coaxial conversion structure of the waveguide coaxial filter provided by the present invention integrates the advantages of the two implementation methods of the traditional waveguide coaxial converter end-launch structure and the 90°angle structure. The present invention chooses to use the last section of the waveguide cavity of the waveguide filter structure to realize the waveguide coaxial conversion function, and innovatively adopts a non-contact T-type impedance matching column, a coaxial probe excitation and a wide wall of the bottom surface of the waveguide to form a magnetic coupling ring, and completes the mode conversion and impedance matching of the waveguide transmission line and the coaxial transmission line by magnetic coupling. The waveguide input port and the coaxial output port are in the same direction, which is conducive to the interconnection of the system and the stability of the system structure. At the same time, the structure is compact and the insertion loss is small.

[0052] 5. The waveguide coaxial filter provided by the present invention integrates the waveguide filtering structure and the waveguide coaxial conversion structure into an integrated design, and adopts an integrated all-metal tube, which meets the requirements of small insertion loss, strong structural stability, miniaturization and lightweight in aerospace environment applications, and can be applied to cryogenic receivers in the aerospace field. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0054] Figure 1 A schematic diagram of the structure for realizing filtering by utilizing the cutoff characteristics of the waveguide transmission line itself;

[0055] Figure 2 A schematic diagram of the structure for loading a resonant diaphragm to achieve filtering;

[0056] Figure 3 A schematic diagram of the structure of a waveguide coaxial converter with a contactless feeding end-launch structure;

[0057] Figure 4 A schematic diagram of the structure of a waveguide coaxial converter with a contact-feed end-launch structure;

[0058] Figure 5 It is a schematic diagram of the structure of a waveguide coaxial converter with a 90° angle structure;

[0059] Figure 6 This is a schematic diagram of the overall structure of the waveguide coaxial filter provided in an embodiment of the present application;

[0060] Figure 7 An exploded view of a waveguide coaxial filter provided in an embodiment of the present application;

[0061] Figure 8 A schematic diagram of the main structure of the waveguide coaxial filter provided in an embodiment of the present application;

[0062] Fig. 9 A schematic diagram of the upper cover structure of the waveguide coaxial filter provided in an embodiment of the present application;

[0063] Fig.10 A schematic diagram of a waveguide coaxial filter provided in an embodiment of the present application;

[0064] Fig.11 This is a schematic diagram of the structure of a T-shaped impedance matching column in an embodiment of the present application;

[0065] Fig.12 This is a schematic diagram of the position relationship between the T-shaped impedance matching column and the coaxial probe in the embodiment of the present application;

[0066] Fig.13 This is a schematic diagram of the size design of the waveguide input port in the embodiment of the present application;

[0067] Fig.14 This is a schematic diagram of the replacement of a straight waveguide and a curved waveguide in an embodiment of the present application;

[0068] Fig.15 Schematic diagram of the waveguide coaxial conversion structure design in the embodiment of the present application; (a) front view, (b) top view;

[0069] Fig.16 The simulation and measured results of the reflection coefficient and out-of-band suppression of the waveguide input port of the waveguide coaxial filter in the embodiment of the present application;

[0070] Fig.17 The simulation and measured results of the reflection coefficient and out-of-band suppression of the coaxial output port of the waveguide coaxial filter in the embodiment of the present application;

[0071] Fig.18These are the simulation and measured results of the insertion loss between the waveguide input port and the coaxial output port of the waveguide coaxial filter in the embodiment of the present application.

[0072] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0073] The embodiment of the present application provides a waveguide coaxial filter, which integrates the waveguide filtering structure and the waveguide coaxial conversion structure into an integrated design, thereby solving the problems of large insertion loss and large volume caused by the cascade connection of two discrete components, the waveguide filter and the waveguide coaxial converter, in the prior art.

[0074] In order to better understand the above technical solution, exemplary embodiments will be described in detail here, and examples thereof are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are only examples of devices consistent with some aspects of the present application as detailed in the attached claims.

[0075] Figures 6 to 10 The structure and principle diagram of the waveguide coaxial filter provided in the embodiment of the present application is as follows. The waveguide coaxial filter comprises:

[0076] Waveguide input port 1, used for inputting electromagnetic wave signals;

[0077] The waveguide filter structure is used to transmit the electromagnetic wave signal input from the waveguide input port 1 in the form of a waveguide transmission line, and filter the spectrum signal of a set frequency in the electromagnetic wave signal;

[0078] A waveguide-coaxial conversion structure is disposed in the output port cavity of the last section of the waveguide filter structure, and is used to realize mode conversion and impedance matching between the waveguide transmission line and the coaxial transmission line, thereby converting the waveguide transmission line mode signal output by the waveguide filter structure into the coaxial transmission line mode signal;

[0079] The coaxial output port 2 is used to output the coaxial transmission line mode signal.

[0080] Among them, the waveguide input port 1, the waveguide filtering structure and the waveguide coaxial conversion structure adopt an integrated all-metal tube.

[0081] The waveguide filter structure uses the cutoff characteristics of the waveguide transmission line itself to achieve the filtering function. Specifically, the waveguide transmission line itself has a specific cutoff frequency. When the signal frequency is lower than the cutoff frequency, the waveguide cannot effectively transmit the signal, thereby achieving the suppression of out-of-band signals. This embodiment uses this characteristic to design a filter structure to achieve the suppression of out-of-band signals.

[0082] In a preferred embodiment, the waveguide filter structure includes a first waveguide transition section 6, a waveguide transmission section 7, a second waveguide transition section 8 and an output port cavity 9 which are connected in sequence. The first waveguide transition section 6 and the second waveguide transition section 8 are centrally symmetrical structures and play a filtering role. The waveguide transmission section 7 is used to suppress out-of-band signals. The output port cavity 9 serves as the output port of the filtered signal and is also used as a waveguide cavity for realizing waveguide coaxial conversion.

[0083] The length of the waveguide transmission section 7 determines the out-of-band suppression. The longer the length, the better the out-of-band suppression. In order to meet the out-of-band suppression and realize the miniaturization of the device, this section of the waveguide used to achieve out-of-band suppression is designed as a curved waveguide structure, and the first waveguide transition section 6 and the second waveguide transition section 8 are connected by the curved waveguide structure.

[0084] The waveguide filter structure integrates the advantages of the two traditional waveguide filter implementation methods of using the waveguide cutoff characteristics and loading the resonant diaphragm. The filter function is realized by using the cutoff characteristics of the waveguide transmission line itself, which has the advantages of simple structure, high mechanical strength and low insertion loss. On this basis, the curved waveguide is innovatively added to further reduce the size, thereby realizing the miniaturization of the device in a better way.

[0085] The waveguide input port 1 is connected and integrated with the first waveguide transition section 6. The size of the output port surface of the output port surface cavity 9 is consistent with that of the waveguide input port 1, so as to achieve impedance matching.

[0086] In a preferred embodiment, the waveguide input port 1 is a BJ84 standard waveguide input port, using the TE10 mode. The size of the waveguide port surface of the output port surface cavity 9 is consistent with that of the waveguide input port 1, and is also the standard BJ84 waveguide size.

[0087] In a preferred embodiment, the coaxial output port 2 is a SMA standard coaxial connector and adopts TEM mode.

[0088] The waveguide input port 1 and the coaxial output port 2 are in the same direction.

[0089] The waveguide coaxial conversion structure includes a T-shaped impedance matching column 10, which is fixed on the bottom wide wall of the output port cavity 9, preferably located in the center of the width of the bottom wide wall; the coaxial output port 2 is horizontally arranged on the output end face of the output port cavity 9, preferably located in the center of the output end face width and in the same direction as the waveguide input port 1.

[0090] The coaxial output port 2 is arranged in parallel with the bottom wide wall of the output port surface cavity 9, and the height of the coaxial output port 2 is greater than the height of the T-shaped impedance matching column 5, so as to meet the following conditions: after the coaxial probe 4 of the coaxial transmission line is inserted into the coaxial output port 2, the coaxial probe 4 and the T-shaped impedance matching column 10 are not in contact, and the gap in the middle is capacitive. The coaxial probe 4, the T-shaped impedance matching column 10 and the bottom wide wall of the output port surface cavity 9 form a magnetic coupling loop, and the signal is converted between the TEM mode of the coaxial line and the TE10 mode of the rectangular waveguide by magnetic coupling.

[0091] Combination Fig.11 The T-shaped impedance matching column 10 includes a first column 11 and a second column 12, both of which are rectangular columns, and the length and width of the first column 11 are smaller than those of the second column 12, the wide side of the first column 11 is connected to the middle of the wide side of the second column 12, and the first column 11 and the second column 12 are integrally formed, and the impedance matching column thus formed is a T-shaped structure as a whole. The impedance matching column with a T-shaped structure can achieve impedance matching through two-stage matching dimensions.

[0092] In a preferred embodiment, a first arc-shaped skirt 13 is formed at the bottom of the first column 11, and a second arc-shaped skirt 14 is formed at the bottom of the second column 12. The arc-shaped skirt is connected and fixed to the bottom wide wall of the output port cavity 9, which can enhance the firmness and stability of the connection.

[0093] Combination Fig.12 , the T-shaped impedance matching column 10 is installed on the bottom wide wall of the output port surface cavity 9, and the first column 11 is located on the inner side and the second column 12 is located on the outer side, that is, the second column 12 is located on the side close to the coaxial output port 2. After the coaxial probe 4 is inserted into the coaxial output port 2, the head end of the coaxial probe 4 is suspended above the T-shaped impedance matching column 10 and does not contact the T-shaped impedance matching column 10. The positions of the T-shaped impedance matching column 10 and the coaxial probe 4 are both symmetrical about the bottom wide wall of the output port surface cavity 9.

[0094] In this embodiment, the T-shaped impedance matching column 10 adopts a two-stage matching method, and realizes impedance matching within a broadband through the size of the two-stage matching and the gap adjustment between the impedance matching column and the coaxial probe. At the same time, a non-contact method is adopted to realize impedance matching and mode conversion. The non-contact method can effectively reduce the problem of large electromagnetic wave emission at the connection point and inability to quickly convert due to the difference between the two structures of the coaxial line and the waveguide, thereby increasing the conversion bandwidth.

[0095] The waveguide impedance and the coaxial impedance are matched by the cooperation of the T-shaped impedance matching column, the coaxial probe and the wide wall of the bottom surface of the waveguide. This structure is original to the present invention. It integrates the advantages of the traditional waveguide coaxial converter end-launch structure and the 90°angle structure. The waveguide input port and the coaxial output port are in the same direction, which is conducive to the interconnection of the system and the stability of the system structure. At the same time, the structure is compact and the insertion loss is small.

[0096] In a preferred embodiment, the waveguide input port 1, the waveguide filter structure and the waveguide coaxial conversion structure are integrated on the main body 100, and the main body 100 adopts an integrated full metal tube. That is to say, the main body 100 includes the waveguide input port 1, the first waveguide transition section 6, the waveguide transmission section 7, the second waveguide transition section 8, the output port surface cavity 9, and the T-shaped impedance matching column 10, and adopts an integrated molding processing method to ensure that the device performance meets the application requirements of the aerospace environment.

[0097] The coaxial output port 2 is provided on the rear cover 300, and the rear cover 300 matches the output end face of the main body 100. The rear cover 300 and the main body 100 are fastened and positioned by screws and positioning pins to ensure the accuracy of assembly. The upper part of the rear cover 300 and the main body 100 is provided with an upper cover 200, and the upper cover 200 is connected and fixed to the rear cover 300 and the main body 100 by screws. The distribution of the screws is based on the direction of the waveguide to ensure that there is no electromagnetic leakage after assembly.

[0098] In a preferred embodiment, the main body 100, the upper cover 200, and the back cover 300 are all made of aluminum alloy. The main body 100, the upper cover 200, and the back cover 300 enclose a waveguide filter and a waveguide coaxial conversion cavity, and the separation position of the main body 100 and the upper cover 200 is selected at the edge of the E surface where the electromagnetic wave energy is smaller.

[0099] The waveguide coaxial filter provided in this embodiment integrates the waveguide filtering structure and the waveguide coaxial conversion structure into an integrated design, thereby optimizing the insertion loss performance as a whole. The insertion loss performance is equivalent to the contribution of only one traditional device, and the additional insertion loss contribution caused by the cascade of two devices is avoided.

[0100] At the same time, the design of the waveguide coaxial conversion structure is completed by using the rear space of the waveguide filter structure, which greatly reduces the size and weight of the device, saves the limited system space, and avoids the additional space and weight requirements caused by the cascade of two devices. While meeting the performance requirements, it has the advantages of miniaturization and lightweight.

[0101] In addition, the present invention adopts an integrally formed all-metal tube, which meets the requirements of small insertion loss, strong structural stability, miniaturization and light weight in aerospace environment applications, and can be applied to aerospace systems.

[0102] The design method and application effect of the present invention are described below with a specific embodiment.

[0103] In recent years, China's space industry has flourished. The fourth phase of my country's lunar exploration project proposed to equip the "Queqiao-2" relay satellite with lunar orbit VLBI equipment, establish a lunar orbit VLBI station, and conduct joint observations with ground-based VLBI stations to conduct the first Earth-Moon ultra-long baseline VLBI scientific experiment. Based on this, the development of the first domestic satellite-borne ultra-high sensitivity X-band cryogenic receiver was proposed.

[0104] The waveguide coaxial filter provided in this embodiment is dedicated to serving the X-band cryogenic receiver, and is installed inside the X-band cryogenic receiver dewar, and is cooled to the 100K temperature zone together with the cryogenic devices inside the dewar, and the operating frequency is 8GHz to 9GHz. The waveguide input port of the waveguide coaxial filter is connected to the waveguide output port of the antenna, and the coaxial output port of the waveguide coaxial filter is connected to the coaxial input port of the cryogenic low noise amplifier.

[0105] The antenna collects weak electromagnetic wave signals in space, and then filters out signals before 7.2 GHz through the waveguide coaxial filter provided in this embodiment, transmits them through the waveguide, and then converts them into coaxial transmission line mode signals and transmits them to the low-temperature low-noise amplifier for low-noise amplification.

[0106] When designing, first determine the size of the X-band BJ84 standard waveguide, and then determine the size of the waveguide input port 1, such as Fig.13 As shown, the waveguide input port 1 is a rectangular cavity, the wide side length c of the waveguide input port 1 is 28.5 mm, and the narrow side length d of the waveguide input port 1 is 12.62 mm. The shape and size of the output port face cavity 9 are consistent with those of the waveguide input port 1.

[0107] Then, electromagnetic simulation software is used to simulate and optimize the waveguide filter structure. Fig.14As shown, in the first simulation, the waveguide transmission section 7 does not adopt a curved waveguide structure, but is replaced by a rectangular straight waveguide 7', and the lengths and dimensions of the first waveguide transition section 6, the second waveguide transition section 8 and the replaced straight waveguide are determined. After the simulation optimization is completed, the straight waveguide is replaced by a curved waveguide with the same waveguide size and length, and the effect of different bending radii R on the performance is simulated.

[0108] The contribution of passive components to the system noise temperature comes from their insertion loss, which is equal to their noise factor. The conversion formula between noise factor and noise temperature is NF=T / T0+1, where NF is the noise factor, T is the noise temperature, and T0 is the ambient temperature (usually 290K). Therefore, at room temperature, an insertion loss of 0.1dB will bring a noise temperature contribution of 6.7K, which is the normal noise temperature contribution caused by conductor loss in a straight waveguide. In the simulation of the bending radius selection of the curved waveguide, it was found that a too small bending radius could not achieve the miniaturization of the device well, and a too large bending radius would lead to an insertion loss of more than 0.1dB and deterioration of the out-of-band suppression. The balance of the test selection is based on the maximum bending radius at which the insertion loss of the curved waveguide does not exceed 0.1dB, and the bending radius was finally determined to be R=14.8mm.

[0109] After completing the simulation design of the waveguide filter structure, the design of the waveguide coaxial conversion structure is added, and the size of the T-type impedance matching column 10 and the height and depth of the coaxial probe 4 are simulated and optimized by electromagnetic simulation software, such as Fig.15 As shown, the specific dimensions of the waveguide coaxial conversion structure are finally determined as shown in Table 1 below.

[0110] Table 1 Waveguide coaxial conversion structure size design

[0111] parameter Dimensions (mm) parameter Dimensions (mm) a 28.5 b 12.62 a1 4.83 b1 5.22 a2 5.34 b2 6.11 a3 7.4 b3 1 a4 5.1 b4 2.1 a5 0.51 a6 2.57

[0112] In Table 1, a represents the length of the wide side of the output port cavity 9, a1 is the distance from the T-type impedance matching column 10 to the back wall of the output port cavity 9 (i.e., the wall opposite to the output port end face, hereinafter referred to as the waveguide back wall), a2 is the distance from the inner side of the second column 12 (i.e., the side away from the waveguide back wall) to the waveguide back wall, a3 is the distance from the inner side of the first column 11 to the waveguide back wall, a4 is the coaxial probe insertion distance, a5 is the length of the second column 12, and a6 is the length of the T-type matching column 10; b represents the length of the narrow side of the output port cavity 9, b1 is the height of the T-type matching column 5, b2 is the distance from the center of the coaxial probe to the bottom of the waveguide, b3 is the width of the second column 12, and b4 is the width of the first column 11.

[0113] In this embodiment, the mechanical design of the waveguide coaxial filter adopts all-aluminum alloy (2A12-H112) material, which is divided into three parts: main body 100, upper cover 200, and back cover 300, and then fastened and assembled by screws. The main body 100 includes a waveguide input port 1, a first waveguide transition section 6, a waveguide transmission section 7, a second waveguide transition section 8, an output port surface cavity 9, and a T-shaped impedance matching column 10. It adopts an integrated molding processing method, and the processing accuracy is controlled to ±0.02mm to ensure the performance of the device. The distribution of screws is based on the waveguide direction to ensure that there is no electromagnetic leakage after assembly. The back cover 300 is the mounting surface of the coaxial connector, and the coaxial output port 2 is provided on the back cover 300. The assembly of the back cover 200 and the main body 100 is fastened and positioned by screws and positioning pins to ensure the accuracy of assembly. The separation position of the main body 100 and the upper cover 200 selects the edge of the E surface where the electromagnetic wave energy is smaller.

[0114] The total length of the waveguide coaxial filter is 120mm. Compared with the traditional technology, the length of the discrete commercial X-band waveguide filter @Qualwave is 300mm, the length of the commercial X-band back-fed waveguide coaxial converter @Qualwave is 73.35mm, and the cascade of the two devices is 373.35mm in total. It can be seen that the size of the waveguide coaxial filter provided in this embodiment is much smaller than the sum of the sizes of the two traditional cascaded devices, and the integrated design effectively realizes the miniaturization of the device.

[0115] Fig.16 The simulation and measured results of the reflection coefficient and out-of-band suppression of the waveguide input port 1 of the waveguide coaxial filter designed and processed in this embodiment are given. Fig.17 The simulation and measured results of the reflection coefficient and out-of-band suppression of the coaxial output port 2 of the waveguide coaxial filter designed and processed in this embodiment are given. Fig.18 The simulation and measured results of the insertion loss between the waveguide input port 1 and the coaxial output port 2 of the waveguide coaxial filter designed and processed in this embodiment are given. Figure 16 to Figure 18 It can be seen that the waveguide coaxial filter designed and processed in this embodiment has an out-of-band suppression of better than 27dB at 7.2GHz, an insertion loss of better than 0.22dB in the working frequency band of 8-9GHz, and a reflection coefficient of better than 15dB. In traditional technology, discretely designed waveguide coaxial converters usually bring 0.1dB insertion loss, and waveguide filters usually bring 0.4dB insertion loss, totaling 0.5dB insertion loss. The insertion loss of the waveguide coaxial filter designed and processed in this embodiment is much smaller than the insertion loss caused by the traditional cascade of two devices. At an operating temperature of 100K, the system noise temperature can be reduced by 6K, greatly improving the system receiving sensitivity.

[0116] The waveguide coaxial filter provided in this embodiment has no aerospace-prohibited or restricted processes and materials, and has good mechanical properties, meeting the requirements of aerospace application environments such as low insertion loss, strong structural stability, miniaturization, and lightweight. It can be directly used in the aerospace field and installed on systems or devices in the aerospace field to achieve the transmission, filtering, and coaxial conversion functions of electromagnetic wave signals.

[0117] It should be understood that although the terms "first", "second", etc. may be used herein to describe various units, these units should not be limited by these terms. These terms are used only to distinguish one unit from another. For example, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit without departing from the scope of the exemplary embodiments.

[0118] The directional terms such as up, down, left, right, front, back, front, back, top, bottom, etc. mentioned or may be mentioned in this specification are defined relative to the structures shown in the drawings. They are relative concepts and may change accordingly according to different positions and different usage conditions. Therefore, these or other directional terms should not be interpreted as restrictive terms.

[0119] The above is only a preferred embodiment of the present application, and is not any formal or substantial limitation to the present application. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present application, and these improvements and supplements should also be regarded as the protection scope of the present application. Any technician familiar with this profession can make some changes, modifications and evolutions of the technical content disclosed above without departing from the spirit and scope of the present application, which are equivalent embodiments of the present application; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the substantial technology of the present application are still within the scope of the technical solution of the present application.

Claims

1. A waveguide coaxial filter, characterized in that: include: A waveguide input port, used for inputting electromagnetic wave signals; A waveguide filter structure, used to transmit the electromagnetic wave signal in the form of a waveguide transmission line and filter the spectrum signal of a set frequency in the electromagnetic wave signal; A waveguide-coaxial conversion structure is disposed in the output port cavity of the waveguide filter structure, and is used to realize mode conversion and impedance matching between the waveguide transmission line and the coaxial transmission line, thereby converting the waveguide transmission line mode signal output by the waveguide filter structure into a coaxial transmission line mode signal; The coaxial output port is used to connect to the coaxial transmission line to output the coaxial transmission line mode signal.

2. The waveguide coaxial filter according to claim 1, characterized in that: The waveguide input port, the waveguide filtering structure and the waveguide coaxial conversion structure adopt an integrated full metal tube.

3. The waveguide coaxial filter according to claim 1, characterized in that: The waveguide filtering structure comprises: The first waveguide transition section and the second waveguide transition section are used to achieve filtering effect; Waveguide transmission section, used to achieve out-of-band signal suppression; The output port cavity is used as the output port of the filtered signal and also as a waveguide cavity for realizing waveguide coaxial conversion; The first waveguide transition section, the waveguide transmission section, the second waveguide transition section and the output port cavity are sequentially connected and integrated.

4. The waveguide coaxial filter according to claim 3, characterized in that: The waveguide transmission section is a curved waveguide structure.

5. The waveguide coaxial filter according to claim 4, characterized in that: The waveguide coaxial conversion structure comprises a T-shaped impedance matching column, the T-shaped impedance matching column is arranged on the bottom wide wall of the output port surface cavity, and the coaxial output port is arranged on the output end surface of the output port surface cavity; The height of the coaxial output port is greater than the height of the T-shaped impedance matching column, so as to satisfy the following requirement: after the coaxial probe of the coaxial transmission line is inserted into the coaxial output port, the coaxial probe is suspended above the T-shaped impedance matching column, and the coaxial probe does not contact the T-shaped impedance matching column.

6. The waveguide coaxial filter according to claim 5, characterized in that: The T-shaped impedance matching column includes a first column and a second column. The first column and the second column are both rectangular columns. The length and width of the first column are smaller than those of the second column. The wide side of the first column is connected to the middle of the wide side of the second column and are integrally formed.

7. The waveguide coaxial filter according to claim 5, characterized in that: The gap between the coaxial probe and the T-shaped impedance matching column is capacitive, and the coaxial probe, the T-shaped impedance matching column and the bottom wide wall of the output port cavity form a magnetic coupling ring, which completes the conversion of the signal between the waveguide transmission line mode and the coaxial transmission line mode by magnetic coupling.

8. The waveguide coaxial filter according to claim 6, characterized in that: The first waveguide transition section and the second waveguide transition section are centrally symmetrical structures; and / or The T-shaped impedance matching column is located in the center of the bottom wide wall width of the output port cavity; the coaxial output port is located in the center of the output end face width of the output port cavity and in the same direction as the waveguide input port.

9. A method for designing a waveguide coaxial filter according to any one of claims 5 to 8, characterized in that: The steps include: The waveguide filter structure is simulated and optimized using electromagnetic simulation software. In the first simulation, a straight waveguide is used in the waveguide transmission section to determine the dimensions of the first waveguide transition section, the second waveguide transition section, and the straight waveguide. After the simulation optimization is completed, the straight waveguide is replaced with a curved waveguide with the same waveguide dimensions, and the effects of different bending radii on the performance are simulated to determine the optimal bending radius of the curved waveguide. After completing the simulation design of the waveguide filter structure, the simulation design of the waveguide coaxial conversion structure was added. The size of the T-type impedance matching column and the height and depth of the coaxial probe were simulated and optimized through electromagnetic simulation software, and the specific size of the waveguide coaxial conversion structure was finally determined. The dimensions of the waveguide input port and the coaxial output port are based on standard waveguide dimensions for the matching mode.

10. A cryogenic receiver, characterized in that: include: Antenna, used to collect electromagnetic wave signals in space; The waveguide coaxial filter according to any one of claims 1 to 8, used to filter the spectrum signal of the set frequency in the electromagnetic wave signal, transmit the electromagnetic wave signal in the form of a waveguide transmission line, and then convert the waveguide transmission line mode signal into a coaxial transmission line mode signal; A low-temperature low-noise amplifier, used for receiving the coaxial transmission line mode signal and performing low-noise amplification; The antenna has a waveguide output port, the low-temperature low-noise amplifier has a coaxial input port, the waveguide input port of the waveguide coaxial filter is connected to the waveguide output port of the antenna, and the coaxial output port of the waveguide coaxial filter is connected to the coaxial input port of the low-temperature low-noise amplifier.

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