Method for adapting the frequency response of a radio frequency device.

Abstract

We will improve the method for adjusting the frequency response of the waveguide after manufacturing. [Solution] The present invention relates to a method for adapting the frequency response of a waveguide manufactured by additive manufacturing. The waveguide comprises a semi-finished metal core having side walls with an outer surface and an inner surface, the multiple inner surfaces defining an internal opening of the waveguide. The method includes the following steps: a. A step of measuring the frequency response of the device and generating a first measured value of the frequency response. b. A process of immersion chemical polishing of a metal core to reduce the thickness of the side walls and increase the volume of the internal opening according to the first measurement value. c. A step of measuring the frequency response of the device and generating a second frequency response measurement value. Repeat steps a. through c. until the second measured value falls within the predetermined range.

Description

Technical Field

[0001] The present invention relates to a method for adapting the frequency response of a radio frequency device.

Background Art

[0002] Radio frequency (RF) signals can propagate in space or in waveguides. These waveguides are used to transmit RF signals or for signal manipulation in the spatial or frequency domain.

[0003] The present invention particularly relates to passive RF devices that enable the transmission and manipulation of radio frequency signals without using active electronic components. Passive waveguides can be classified into three different categories. · Devices that rely on waveguiding within a metallic cavity path, commonly called waveguides. · Devices that rely on waveguiding within an insulator substrate. · Devices based on waveguiding by surface waves on a metallic substrate (printed circuit board (PCB), microstrip, etc.).

[0004] The present invention particularly relates to the manufacture of waveguides belonging to the first category above, and these will be collectively referred to as "waveguides" hereinafter. Examples of such devices include waveguides (waveguide tubes) themselves, filters, antennas, polarizers, mode converters, etc. These can be used for signal routing, frequency filtering, signal separation or recombination, transmission or reception of signals in free space or from free space, and the like.

[0005] Conventional waveguides are devices consisting of cavities whose shape and dimensions determine the propagation characteristics of electromagnetic waves of a specific wavelength. Conventional waveguides used for high-frequency signals have internal openings with a rectangular or circular cross-section. These propagate electromagnetic modes corresponding to different electromagnetic field distributions along their cross-section.

[0006] Manufacturing waveguides with complex cross-sections is difficult and costly. To address this problem, Patent Document 1 (US2012 / 0084968) proposes the manufacture of waveguides using three-dimensional (3D) printing. For this purpose, a non-conductive plastic core is printed using additive manufacturing and then plated with metal by immersion. The internal surface of the waveguide must be electrically conductive for it to function. Using a non-conductive core reduces the weight and cost of the equipment, and by employing 3D printing techniques suitable for polymers and ceramics, it is possible to manufacture high-precision parts with low wall roughness. The parts described in this document have a complex shape, with a path for wave propagation on one end and fixing holes on the other end for fixing to the waveguide legs.

[0007] There are various types of 3D printing technologies, one of which is laser selective melting 3D printing (SLM). This is a selective melting process on a powder bed, where a laser is used to melt metal microparticles. The metal particles are melted according to a computer-determined pattern until they fuse together. A powder spreading system then applies a new layer of powder. The laser then paints the next layer. These processes are repeated until the object is printed.

[0008] SLM printing can print layers with a thickness of 0.02 mm to 0.10 mm in the Z-axis direction, but the resolution in the X and Y axes varies depending on the laser beam diameter of the machine. Standard SLM machines use lasers with beam diameters of 0.080 mm and 0.1 mm. For aluminum, the diameter of the molten layer around the laser beam is approximately 0.250 mm. Ideally, two beams are required to manufacture the waveguide walls, resulting in a minimum thickness of 0.5 mm.

[0009] The metal parts obtained through this process can have layer thicknesses far exceeding the resolution of the machine in the Z-direction, depending on the desired shape, due to the constraints mentioned above. This directly affects the weight of the manufactured parts.

[0010] Laser-selective sintering (SLS) 3D printing is also well-known, particularly for printing plastics. However, this method also suffers from similar problems, such as resolution issues related to the diameter of the laser beam.

[0011] One of the crucial steps in the manufacture of waveguides is calibrating the frequency response of the device to suit its intended function.

[0012] The frequency response is determined, in particular, by the shape of the resonant cavity(s) of the waveguide, especially its internal volume. The frequency response of the waveguide can be adjusted from the outside using adjustment screws inserted into the resonant cavity(s). This frequency response adjustment process is performed after the waveguide itself has been manufactured, when it is no longer possible to change the geometry of the resonant cavity(s) of the waveguide.

[0013] However, tuning the frequency response can sometimes require significant adjustments, particularly those related to manufacturing defects or imperfections in the device. These adjustments do not affect the device's geometry or internal volume, but rather the external tuning elements that need to be incorporated into the device.

[0014] Therefore, a method is needed to adapt the frequency response of the waveguide, which allows for adjustment of this response during manufacturing. [Prior art documents] [Patent Documents]

[0015] [Patent Document 1] U.S. Patent Application Publication No. 2012 / 084968 [Overview of the project] [Problems that the invention aims to solve]

[0016] One of the objectives of the present invention is to provide a method for adapting the frequency response of a waveguide device without the limitations of the prior art.

[0017] One further object of the present invention is to provide a faster method as a method for adapting the frequency response of a waveguide device.

[0018] One further object of the present invention is to provide a method for adapting the frequency response of a waveguide device that can limit the use of external elements after the manufacture of the waveguide.

Means for Solving the Problems

[0019] In the present invention, these objects are achieved, in particular, by a method for adapting the frequency response of a waveguide device manufactured by additive manufacturing. The device comprises a semi-finished metal core having side walls with an external surface and internal surface(s), the plurality of internal surfaces defining an internal opening of the device. The method includes the following steps. a. Measuring the frequency response of the device to generate a first measurement value of the frequency response. b. Immersion chemical polishing of the metal core to reduce the thickness of the side walls and increase the volume of the internal opening according to the first measurement value. c. Measuring the frequency response of the device to generate a second frequency response measurement value. Steps a. to c. are repeated until the second measurement value falls within a predetermined range.

[0020] In this way, the frequency response of the waveguide device is adjusted by changing the internal volume of the device.

[0021] In one embodiment, the immersion time is between 45 seconds and 90 seconds.

[0022] In one embodiment, the thickness of the side wall(s) is reduced by a removal thickness of 5 μm to 30 μm, preferably 10 μm to 20 μm.

[0023] In one embodiment, the final thickness of the side walls of the device after repeating steps a. to c. is less than 300 μm, preferably less than 200 μm.

[0024] In one embodiment, the metal core is manufactured by powder bed laser melting (SLM) to obtain a semi-finished metal core, where the removal thickness is at least 1 times the particle size of the powder in the powder bed.

[0025] In one embodiment, the immersion process of the semi-finished metal core is carried out in an acid bath.

[0026] In one embodiment, the acid bath contains a mixture of two acids.

[0027] In one embodiment, the acid bath contains orthophosphoric acid (orthophosphoric acid, orthophosphate) and sulfuric acid.

[0028] In one embodiment, the density of the bath (liquid) is 1.5 g / cm³. 3 From 2 g / cm³ 3 The range is preferably 1.7 g / cm³. 3 It is nearby.

[0029] In one embodiment, the treatment temperature of this acid bath is 70°C to 120°C.

[0030] In one embodiment, the acid bath further contains dissolved aluminum at a concentration of 20 g / liter (g / l) to 50 g / liter, preferably 25 g / liter to 45 g / liter.

[0031] In one embodiment, the immersion of the semi-finished metal core is carried out in a basic bath.

[0032] In one embodiment, the basic bath contains a caustic solution and has a pH greater than 11.5.

[0033] In one embodiment, the method may include the following steps. b'. Following immersion in a basic bath, the semi-finished metal core is immersed in an acidic deoxidation bath to remove oxide residue from the surface of the apparatus.

[0034] In one embodiment, the method may include the following steps. b). A step of immersing a semi-finished metal core in an acid bath having a pH of preferably less than 2, such as a bath containing nitric acid and ammonium difluoride.

[0035] In one embodiment, the method may include step b'. b'. A step of immersing a semi-finished metal core in a heated acid bath 10 in order to clean it using ultrasound. [Effects of the Invention]

[0036] This solution has the advantage of enabling the manufacture of waveguides that are closer to the target frequency characteristics and require less post-manufacturing adjustment and fine-tuning compared to conventional technologies.

[0037] In particular, the use of external components such as adjustment screws for adjusting the frequency response can be significantly limited or completely eliminated. [Modes for carrying out the invention]

[0038] In this invention, the waveguide comprises a metal core made of, for example, aluminum, titanium, steel, Invar, or an alloy of these metals.

[0039] The core is manufactured by additive manufacturing, preferably by stereolithography, selective laser melting (SLM), selective laser sintering (SLS), binder jetting, or concentrated energy deposition (DED). The thickness of the core wall is, for example, at least 0.5 mm.

[0040] This core surrounds an internal opening that forms a waveguide. Therefore, the core has an internal surface and an external surface that define the internal opening (for example, a horizontally elongated cross-sectional shape).

[0041] A chemical polishing bath smooths out the fine surface roughness of the material used to form the core (e.g., aluminum). Polishing is a process that reduces the material's roughness Ra and improves its wave reflectivity (spectrality). Therefore, it smooths the peaks and valleys (or depressions) of the material's surface. Polishing is performed by immersing the part in the bath and stirring it.

[0042] Material roughness Ra, mean roughness, or arithmetic mean roughness refers to the average deviation between the peaks and valleys of a material in the size of particles (or granules) used in additive manufacturing.

[0043] It is known that chemical or electrochemical polishing processes are used to reduce the roughness of materials. Surprisingly, the polishing process of the present invention aims not only to improve the surface detail of the material but also to reduce the thickness of the waveguide walls. This reduction in wall thickness can also significantly reduce the weight of the apparatus.

[0044] The frequency response of a waveguide refers to the waveguide's response to an input frequency-varying signal. This frequency response is characterized by the amplitude (measured in decibels) and phase (measured in radians) of the waveguide's response to frequency.

[0045] Measuring the frequency response of a waveguide is essential for verifying the correct operation of the device according to its intended application.

[0046] The frequency response depends particularly on the geometry of the waveguide, and more specifically, the internal geometry of the resonant cavity, and especially its volume. Changing the internal volume of the waveguide will alter its frequency response.

[0047] Generally, the frequency response of a given radio frequency device (or waveguide device) is measured experimentally by propagating an input signal through the device and measuring the characteristics of the output signal, particularly its amplitude and phase. Each type of radio frequency device (hereinafter abbreviated as RF device) has an optimal frequency response (or more generally, frequency response range) depending on its application. Therefore, it is advantageous to be able to adapt the frequency response of a manufactured device based on the theoretically optimal frequency response value for that type of device.

[0048] This method iteratively adjusts the frequency response of an RF device by repeatedly immersing and polishing the RF device and measuring the frequency response after one or more immersions. This method can be used as an alternative to conventional frequency adjustment methods or as a fine-tuning step in the manufacturing process.

[0049] Various parameters related to immersion (e.g., immersion time, number of immersions, bath composition, bath temperature, bath agitation during immersion, application of ultrasound, etc.) are determined according to the target frequency response for a particular RF device. In particular, these parameters differ depending on the type of RF device, and further, they differ from device to device depending on the application.

[0050] Therefore, for example, in one embodiment of the present invention, the initial measurement of the frequency response of the RF device is performed using known measurement techniques. Based on this initial measurement, the chemical polishing parameters described above are determined, and the device is chemically polished. The thickness of the device walls is gradually reduced, increasing the internal volume of the device. After polishing, a second measurement of the frequency response of the RF device is performed. If this second measurement corresponds to one or both of the amplitude and phase values ​​suitable for the device's application, the process is terminated. If the second measurement does not match one or both of the amplitude and phase values ​​suitable for the device's application, a new set of chemical polishing parameters is determined based on the second measurement result, and the device is chemically polished again according to these new parameters. These steps are repeated until the measured value of the frequency response after polishing falls within the range of values ​​corresponding to the desired application for the device.

[0051] The terms "RF equipment" and "waveguide equipment" are particularly important. Single waveguides, waveguide arrays, antennas, antenna arrays, polarizers (especially septum polarizers), couplers, dividers, converters (especially orthogonal mode converters), beamforming networks, filters, comb filters, dissipation mode filters This encompasses all classifications of passive RF devices.

[0052] The term "semi-finished metal core" refers to a state of metal core obtained through additive manufacturing, but also includes those that require further finishing processes. For example, this includes not only the chemical polishing process mentioned above, but also coating, polishing, assembly, and other processes.

[0053] Advantageously, the thickness of the sidewalls of the RF apparatus after the chemical polishing process is less than 300 μm, preferably less than 200 μm, and even less than 150 μm. Thus, the chemical polishing process not only adapts the frequency response of the RF apparatus but also provides a wall thickness sufficient to limit the weight of the apparatus.

[0054] In one embodiment, the removal thickness, i.e., the thickness of the material removed by chemical polishing at each stage, depends on the specific additive manufacturing technique used to produce the semi-finished core.

[0055] For example, when a semi-finished metal core is manufactured by powder bed laser melting, the removal thickness is preferably at least one times the particle size of the powder in the powder bed. This improves the surface condition after polishing.

[0056] In one embodiment, each polishing step includes immersing the RF device in one or more consecutive baths. These baths may have different or similar compositions. The function of each bath may be material removal, cleaning, or surface treatment.

[0057] The immersion times in each of these baths may be different or the same. Typically, the immersion time in the bath is between 20 and 200 seconds, depending on the desired removal thickness and / or the composition of the bath liquid. Preferably, the immersion time is between 30 and 120 seconds, or between 45 and 90 seconds.

[0058] By using an immersion bath to reduce the wall thickness of the waveguide, it becomes possible to combine surface treatment processes necessary for the proper operation of the device (e.g., polishing to reduce internal roughness) with frequency response optimization processes. In fact, the thickness of the wall of the semi-finished core can be determined according to the desired final surface state and target frequency response. In this way, multiple processes can be carried out simultaneously, optimizing the manufacturing time and, consequently, the cost of the device.

Claims

1. A method for adapting the frequency response of a waveguide obtained by additive manufacturing, wherein the waveguide comprises a semi-finished metal core having a plurality of side walls having a plurality of external and internal surfaces, the plurality of internal surfaces defining an internal opening in the waveguide, and the method is as follows: a. A step of measuring the frequency response of the device and generating a first frequency response measurement value, b. A process of immersion chemical polishing of a metal core to reduce the thickness of the side wall according to the first measurement value and increase the volume of the internal opening, c. A step of measuring the frequency response of the device and generating a second frequency response measurement value, d. A process in which steps a. to c. are repeated until the second measured value falls within a predetermined range. A method for adapting the frequency response of a waveguide obtained by additive manufacturing, comprising the following:

2. The method according to claim 1, wherein the immersion time is between 45 and 90 seconds.

3. The method according to claim 1 or 2, wherein the thickness of a plurality of side walls is reduced by a removal thickness of 5 μm to 30 μm, preferably 10 μm to 20 μm.

4. The method according to any one of claims 1 to 3, wherein the final thickness of the multiple side walls of the apparatus after repeatedly performing steps a. to c. is less than 300 μm, preferably less than 200 μm.

5. The method according to any one of claims 1 to 4, wherein the metal core is manufactured by powder bed laser melting (SLM) to obtain the semi-finished metal core, and the removal thickness is equal to at least one times the particle size of the powder in the powder bed.

6. The method according to any one of claims 1 to 5, wherein the immersion step of the semi-finished metal core is performed in a single acid bath.

7. The method according to claim 6, wherein the acid bath contains a mixture of two types of acids.

8. The method according to claim 7, wherein the acid bath contains orthophosphoric acid and sulfuric acid.

9. The liquid density of the bath is 1.5 g / cm³. ３ From 2 g / cm³ ３ The method according to claim 8, wherein the range is preferably around 1.7 g / cm³.

10. The method according to any one of claims 6 to 9, wherein the temperature of the acid bath treatment is between 70°C and 120°C.

11. The method according to any one of claims 6 to 10, wherein the acid bath additionally contains dissolved aluminum at a concentration of 20 g / liter (g / l) to 50 g / liter, preferably 25 g / liter to 45 g / liter.

12. The method according to any one of claims 1 to 5, wherein the immersion step of the semi-finished metal core is performed in a basic bath.

13. The method according to claim 12, wherein the basic bath contains a caustic solution and has a pH greater than 11.

5.

14. b'. A step to remove oxidative residue from the surface of the apparatus by immersing the semi-finished metal core in an acidic deoxidation bath, following immersion in the basic bath. The method according to claim 12 or 13, comprising:

15. b) For cleaning, the semi-finished metal core is immersed in an acid bath with a pH of preferably less than 2, such as a bath containing nitric acid and ammonium difluoride. The method according to any one of claims 12 to 14, comprising:

16. b'. A step of immersing the semi-finished metal core in a heated acid bath 10 by applying ultrasound. The method according to any one of claims 6 to 15, comprising:

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