Airborne high-suppression high-power filter

Abstract

The utility model discloses an airborne high-suppression high-power filter, and relates to the field of communication. The radio frequency circuit comprises seven inductors which are connected in sequence, and every two adjacent inductors are grounded through a capacitor. The working frequency band is 500MHz, the in-band loss is less than 0.4 dB through circuit design, continuous wave 2000W high power can be borne, the size is small, the weight is light, out-of-band harmonic waves of a high-power transmitter can be filtered, and the electromagnetic compatibility of the system is improved. High suppression is realized by adopting a circuit form of a 13-section Chebyshev LC low-pass filter, and 760MHz out-of-band suppression can reach more than 70dB. Through structural process design and box body laser seal welding, the vibration and low-pressure environment of airborne use can be met. The antenna is suitable for improving the electromagnetic compatibility of an airborne broadband high-power transmitting system.

Description

Technical Field

[0001] The utility model relates to an airborne high-suppression high-power filter in the field of communications, which realizes the function of harmonic filtering of high-power transmitters, has a wide operating frequency band, can withstand large power, has high out-of-band suppression, is small in size and light in weight, has good vibration resistance, and can adapt to high-altitude low-pressure environments, meeting the application requirements of airborne broadband high-power transmission systems for improving their own electromagnetic compatibility. Background Art

[0002] With the advancement of communications technology, electronic devices are becoming increasingly sophisticated, with smaller sizes and higher functionality. Electronic systems are becoming increasingly integrated, and their frequency coverage is expanding. Simultaneous operation of devices in different frequency bands within a system requires good electromagnetic compatibility between these devices. High-power transmitters in a system generate strong harmonic signals, which can affect the normal operation of devices in other frequency bands. High-power filters are therefore required to filter out these harmonics and improve the system's electromagnetic compatibility.

[0003] There are many ways to classify filters. Based on their frequency response, they can be divided into four basic types: low-pass, band-pass, high-pass, and band-stop. Low-pass filter design is fundamental; appropriate frequency conversion can transform low-pass filters into band-pass, high-pass, and band-stop filters. Filters are generally categorized by implementation form, including LC filters, dielectric filters, cavity filters, surface acoustic wave filters, and microstrip filters.

[0004] Traditional high-rejection, high-power filters require a large number of filter sections for high rejection, and high power requires high component withstand voltage, low loss, and excellent heat dissipation. These requirements result in a large filter size. Airborne filters, on the other hand, require small size, low weight, good vibration resistance, and adaptability to high-altitude, low-pressure operating environments. Currently, there is little information on airborne high-rejection, high-power filters. To meet the needs of airborne broadband, high-power transmission systems to improve their electromagnetic compatibility, the development of high-rejection, high-power filters that meet airborne operating environments has become a key technology that urgently needs to be addressed in current engineering applications. Utility Model Content

[0005] The technical problem to be solved by the present invention is to achieve high suppression through circuit design of a 13-section Chebyshev LC low-pass filter; to increase power capacity by improving the withstand voltage and heat dissipation capability and reducing losses through device design; to improve the withstand voltage of the medium by designing a silicone adhesive coating method, thereby reducing the redundant space size of the box body and achieving miniaturization; and to solve problems such as temperature adaptability of the ceramic substrate, high-power air breakdown, high-intensity vibration, and high-altitude low-pressure environment through designing the structure and assembly process.

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

[0007] An airborne high-rejection high-power filter includes a radio frequency circuit.

[0008] The radio frequency circuit includes seven inductors connected in sequence, and each adjacent inductor is grounded via a capacitor.

[0009] Furthermore, it also includes a box body 28 and a ceramic insulator 24. The ceramic insulator passes through one of the box surfaces of the box body, and its inner end is connected to the radio frequency circuit; a cover is provided on the top of the box body, and the top cover and the box body are laser sealed.

[0010] Furthermore, the capacitor is a single-layer alumina ceramic plate capacitor, and the inductor is a hollow inductor wound with gold-plated copper wire;

[0011] The bottom surface of the box body is provided with a molybdenum copper carrier 27, which is welded to the corresponding position of the bottom surface of the box body 28; the ceramic plate capacitors 21 correspond to the molybdenum copper carriers 27 one by one, and the ceramic plate capacitors 21 are all welded to the upper surface of the molybdenum copper carrier 27; the inductor 22 is electrically welded to the corresponding position of the ceramic plate capacitor 21;

[0012] Silicone glue is applied to the inner bottom surface of the box body 28 and the ceramic plate capacitor 21 and the polytetrafluoroethylene support block 25 is fixed to the corresponding position of the box body 28 by screws 26. The inductor 22 is bonded and fixed to the polytetrafluoroethylene support block 25 using silicone glue.

[0013] Furthermore, the core of the ceramic insulator is made of Kovar material with a diameter of 2 mm, plated with gold, and the alumina ceramic is processed into an annular column. The core passes through the annular column ceramic and is welded together using gold-tin.

[0014] A method for installing an airborne high-inhibition high-power filter is used to install an airborne high-inhibition high-power filter, specifically comprising the following steps:

[0015] Step 1: solder the molybdenum copper carrier 27 to the box body 28;

[0016] Step 2: The ceramic plate capacitor 21 is soldered to the molybdenum copper carrier 27 using solder;

[0017] Step 3, the ceramic insulator 24 is soldered to the box body 28;

[0018] Step 4: Electrically weld the inductor 22 to the corresponding positions of the ceramic insulator 24 and the ceramic plate capacitor 21 in the box body 28;

[0019] Step 5: Install the RF socket and perform debugging tests on a vector network analyzer. Fine-tune the filter specifications by adjusting the inductor coil spacing. During the debugging process, reserve a certain bandwidth margin.

[0020] Step 6: After debugging is completed, a 3mm thick silicone adhesive is applied to the bottom surface of the box body 28 and the ceramic plate capacitor 21;

[0021] Step 7: After the silicone adhesive is cured, use screws 26 to fix the polytetrafluoroethylene support block 25 to the corresponding position of the box body 28, and use silicone adhesive to bond and fix the inductor 22 to the polytetrafluoroethylene support block 25;

[0022] Step 8: After the silicone adhesive is completely cured and before installing the cover plate 23, use tooling and equipment to perform a gas leakage rate test on the box body 28 and check the welding condition of the ceramic insulator 24;

[0023] Step 9: After the air leakage rate test is normal, the box body 28 and the cover plate 23 are laser sealed;

[0024] Step 10: After the laser sealing is completed, the filter is tested for air leakage rate again. If the test is normal, the filter is qualified.

[0025] The utility model has the following gain effects:

[0026] a) The utility model has high out-of-band suppression through radio frequency circuit design, which facilitates high power implementation of the device.

[0027] b) The utility model improves the power capacity of the filter by solving the voltage resistance and heat dissipation problems of the core high-power components, and can withstand greater power.

[0028] c) The four structural process designs of the utility model solve the environmental adaptability problems of miniaturization, high power breakdown, high-intensity vibration, high altitude and low air pressure of airborne high-inhibition high-power filters.

[0029] d) The radio frequency interface of the utility model adopts an asymmetric structure layout of ceramic insulators and is designed according to the layout of a power amplifier using a filter, which is conducive to the miniaturization of the upper-level product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the radio frequency circuit principle of the utility model;

[0031] Figure 2 This is a schematic diagram of the installation structure process design of the utility model;

[0032] Figure 3 yes Figure 2 Schematic diagram of the cross section of AA;

[0033] Figure 4This is a graph showing the test results of transmission loss and return loss of the utility model; DETAILED DESCRIPTION

[0034] The following is a detailed description of the specific embodiments of the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0035] A high-suppression, high-power filter characterized by a filter RF circuit consisting of inductors 01 to 07 and capacitors 08 to 13. Taking into account various filter requirements, including frequency, power, volume, and operating environment, a 13-cell Chebyshev LC low-pass filter circuit is employed. This circuit offers high out-of-band suppression and minimal component value variation, facilitating high-power device implementation and assembly.

[0036] The capacitors are constructed using single-layer alumina ceramic plates, offering high dielectric withstand voltage, excellent heat dissipation, and suitability for high power applications. The capacitor design calculates the metal areas on both the upper and lower surfaces of the ceramic plate based on the required capacitance. The plate dimensions are increased so that the edge of the upper metal pattern is greater than 5mm from the edge of the plate. Sharp corners of the upper metal pattern are rounded to prevent close proximity to the ground and sparking during high power operation. The lower layer of the ceramic plate is entirely metal, providing solder grounding and high-power heat dissipation. The inductor is a hollow-core inductor wound with gold-plated copper wire, offering low losses, high thermal conductivity, and high power handling. The inductor design uses a 2mm diameter gold-plated copper wire and an 8mm diameter inductor coil. The number of turns is calculated based on the required inductance, with a spacing of greater than 1mm between the wires to prevent sparking during high power operation. Ceramic insulators replace conventional glass insulators, offering significantly lower dielectric losses and the ability to handle higher power. The ceramic insulator is designed with a core made of 2mm diameter Kovar material and gold plating. The alumina ceramic is processed into a ring column. The size is calculated based on 50 ohm impedance. The inner and outer surfaces of the ring column are metallized and gold-plated by sputtering process. The core and the ring column are welded with gold-tin to form an insulator.

[0037] The thermal expansion coefficient of alumina is about 6.9ppm / ℃, and the thermal expansion coefficient of aluminum alloy is about 23ppm / ℃. The alumina ceramic plate may break during high-temperature welding or sudden changes in ambient temperature. In order to improve the temperature adaptability of the alumina ceramic plate, a molybdenum-copper carrier with a medium thermal expansion coefficient is added to match the large difference in thermal expansion coefficients between the ceramic plate and the aluminum alloy box.

[0038] Due to the need for miniaturized design, the space inside the filter box is limited. When working at high power, the electric field intensity is very high and close to the air breakdown field intensity. Silicone glue with a higher dielectric withstand voltage value is used to coat the ceramic plate to prevent the occurrence of high-power air breakdown.

[0039] In order to cope with high-intensity airborne vibration conditions and prevent high-power inductors from being damaged by metal fatigue, a polytetrafluoroethylene support block was designed. The dielectric constant of this material is 2.2, which has little effect on RF circuit indicators. It is bonded to the inductor with silicone glue to avoid metal fatigue damage caused by large swings when the inductor vibrates.

[0040] Low air pressure at high altitudes will reduce the air breakdown field strength. To address this problem, the box body is designed to be laser sealed, and the RF interface uses a ceramic insulator welded to the box body to ensure good airtightness.

[0041] Reference Figures 1 to 4 This embodiment includes filter RF circuit design, filter installation structure process design and index test results.

[0042] The filter RF circuit, the RF input end is connected to one end of inductor 01, the other end of inductor 01 is connected to inductor 02 and capacitor 08, and the other end of capacitor 08 is grounded; the other end of inductor 02 is connected to inductor 03 and capacitor 09, and the other end of capacitor 09 is grounded; the other end of inductor 03 is connected to inductor 04 and capacitor 10, and the other end of capacitor 10 is grounded; the other end of inductor 04 is connected to inductor 05 and capacitor 11, and the other end of capacitor 11 is grounded; the other end of inductor 05 is connected to inductor 06 and capacitor 12, and the other end of capacitor 12 is grounded; the other end of inductor 06 is connected to inductor 07 and capacitor 13, and the other end of capacitor 13 is grounded; the other end of inductor 07 is connected to the RF output end.

[0043] Filter installation structure process, the molybdenum copper carrier 27 is soldered to the box body 28, the ceramic plate capacitor 21 is soldered to the molybdenum copper carrier 27, and the ceramic insulator 24 is soldered to the box body 28. The inductor 22 is electrically soldered to the corresponding positions of the ceramic insulator 24 and the ceramic plate capacitor 21 in the box body 28. After the filter is installed in the RF socket, a debugging test is performed on the vector network analyzer, and the filter indicators are fine-tuned by adjusting the spacing between the inductor coils. A certain bandwidth needs to be reserved during debugging because the subsequent coating of silicone glue will produce some frequency offset. After debugging is completed, 3mm thick silicone glue is applied to the bottom surface of the box body 28 and the ceramic plate capacitor 21. After the silicone glue is cured, the polytetrafluoroethylene support block 25 is fixed to the corresponding position of the box body 28 using screws 26, and the inductor 22 is bonded to the polytetrafluoroethylene support block 25 using silicone glue. After the silicone adhesive has completely cured, a leak rate test is performed on the box body 28 using tooling and instrumentation, along with the welding of the ceramic insulator 24. If the leak rate test is normal, the box body 28 and cover plate 23 are laser-sealed. After the laser sealing is complete, the filter is tested for leak rate again. If normal, the filter is considered qualified.

[0044] The filter's technical specifications have been tested, with in-band loss less than 0.4dB, out-of-band rejection from 760MHz to tripled frequency greater than 70dB, and good in-band return loss. Airborne verification has confirmed that its power handling and other specifications meet requirements.

[0045] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes but is not limited to the contents described in the drawings and the above specific embodiments. Any modifications that do not deviate from the functional and structural principles of the present invention are included within the scope of the claims.

Claims

1. An airborne high-suppression high-power filter, characterized in that: including radio frequency circuits; The RF circuit includes seven inductors connected in sequence, each adjacent inductor is grounded through a capacitor; It also includes a box body (28) and a ceramic insulator (24), the ceramic insulator passes through the side wall of the box body, and its inner end is connected to the radio frequency circuit; the top of the box body is provided with a cover plate, and the top cover and the box body are laser sealed.

2. The airborne high-suppression high-power filter according to claim 1, characterized in that: The capacitor is a single-layer alumina ceramic plate capacitor, and the inductor is a hollow inductor wound with gold-plated copper wire; The bottom surface of the box body is provided with a molybdenum copper carrier (27), and the molybdenum copper carrier (27) is welded to the corresponding position of the bottom surface of the box body (28); the ceramic plate capacitors (21) correspond to the molybdenum copper carrier (27) one by one, and the ceramic plate capacitors (21) are all welded to the upper surface of the molybdenum copper carrier (27); the inductor (22) is then electrically welded to the corresponding position of the ceramic plate capacitor (21); Silicone glue is applied to the inner bottom surface of the box body (28) and the ceramic plate capacitor (21), and the polytetrafluoroethylene support block (25) is fixed to the corresponding position of the box body (28) by screws (26), and the inductor (22) is bonded and fixed to the polytetrafluoroethylene support block (25) using silicone glue.

3. The airborne high-suppression high-power filter according to claim 2, characterized in that: The core of the ceramic insulator is made of gold-plated Kovar material with a diameter of 2 mm, and the alumina ceramic is processed into an annular column. The core passes through the annular column ceramic and is welded together using gold-tin.

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