Broadband microwave window assembly

Abstract

The present invention relates to a broadband microwave window assembly with a Brewster waveguide window, a single mode microwave reactor system with a waveguide with a Brewster waveguide window, and a method for manufacturing a waveguide with a Brewster waveguide window.

Description

Technical Field

[0001] The present invention relates to a broadband microwave window assembly having a Brewster waveguide window, a single-mode microwave reactor system having a waveguide with a Brewster waveguide window, and a method of manufacturing a waveguide with a Brewster waveguide window.

Background Art

[0002] Microwaves are widely used in modern technologies.

[0003] In some applications such as industrial pyrolysis, or medical and high-power physics, radar and telecommunications applications, it is desirable to achieve high-power transmission without significant losses.

[0004] For the propagation of high-power microwaves through a waveguide, it is often necessary to select the frequencies to be transmitted and those that do not need to be reflected, and the presence of a microwave window that can separate gas or pressure without causing significant losses is required.

[0005] In these applications, the microwave window can be arranged to follow the Brewster principle.

[0006] However, generally, solutions using the Brewster angle require a plane wave or quasi-plane wave, circular TE01 mode, or Gaussian LP01 or HE11 mode.

[0007] If the propagation of the fundamental mode is required, in these solutions, it is necessary to convert the fundamental mode to the above modes in order to enable transmission within the window. This generally results in a significant power reduction and requires an expensive and complex mode converter.

[0008] Therefore, there is a need for a waveguide solution that enables high-power microwave transmission of a single fundamental mode within the waveguide without significantly increasing the trap mode, i.e., ghost mode, or reflection of incident power.

[0009] Overheating is also a common problem with microwave windows.

[0010] In this respect, broadband microwave window assemblies that can couple high-frequency, high-power microwave radiation within a waveguide without overheating, significant accumulation of trap modes, or reflection of incident power are advantageous. [Overview of the project] [Problems that the invention aims to solve]

[0011] The object of the present invention is to provide a broadband microwave window assembly that can couple high-frequency, high-power microwave radiation within a waveguide without overheating, significant accumulation of trap modes, or reflection of incident power.

[0012] The objective of this invention can also be considered to be to provide an alternative to the prior art.

[0013] In particular, an object of the present invention is to provide a broadband microwave window assembly that can couple high-frequency, high-power microwave radiation within a waveguide without overheating, significant accumulation of trap modes, or reflection of incident power, by using a microwave window pane comprising an inductive iris and a low dielectric loss ceramic material. [Means for solving the problem]

[0014] Accordingly, the above objectives and several other objectives are intended to be achieved by a broadband microwave window assembly comprising, in a first aspect of the present invention, a rectangular waveguide, a microwave window pane located within the rectangular waveguide and inclined with respect to the microwave propagation direction according to the Brewster angle, and an inductive iris positioned around the microwave window pane.

[0015] This invention relates to a distributed waveguide window in a fundamental mode rectangular waveguide. Therefore, the window broadband microwave window assembly can be considered a single-mode broadband microwave window assembly because only fundamental modes exist and propagate within the rectangular waveguide.

[0016] The waveguide window pane is positioned at the Brewster angle inside the rectangular waveguide.

[0017] The Brewster angle is the angle of incidence at which microwaves traveling along a waveguide with a specific mode completely penetrate the dielectric surface without reflection.

[0018] Generally, solutions using the Brewster angle require a plane wave or quasi-plane wave, a circular TE01 mode, or a Gaussian LP01 or HE11 mode.

[0019] For such a solution to work, the basic mode needs to be converted to the aforementioned mode.

[0020] In the broadband microwave window assembly of the present invention, the width of the microwave window pane is adjusted by using an inductive iris to overcome the non-plane wave state in the rectangular waveguide and to match the capacitive load of the waveguide.

[0021] A microwave window pane inclined with respect to the propagation direction of microwaves according to Brewster's angle is also called a Brewster window, which is a transparent plate oriented at Brewster's angle so that parasitic reflection loss is minimized.

[0022] The pane is transparent to microwaves and has a plane-parallel and flat main surface. The plane formed by the propagation direction and the normal of the window pane is in the same plane as the polarization direction of the microwaves.

[0023] The inductive iris is a symmetric iris arranged around the microwave window pane, such as surrounding the microwave window pane, or arranged at least at the ends, such as at least two ends of the microwave window pane.

[0024] The microwave window pane is arranged at Brewster's angle within a rectangular waveguide, but the microwave window pane can be regarded as a distributed microwave window assembly. At each point of the microwave window assembly along the wave propagation axis, the presence of the inductive iris can cancel the capacitive loading of the rectangular waveguide by the microwave window pane. In this way, the microwave window assembly can be considered to be broadband.

[0025] In some embodiments, the broadband microwave window assembly according to the first aspect is configured to operate in a fundamental TE 10 waveguide mode.

[0026] Electromagnetic waves propagate along the waveguide using various modes.

[0027] For a rectangular waveguide or a hollow rectangular waveguide, that is, for a waveguide with a rectangular cross-section, there are two types of waves, a transverse electric (TE) wave and a transverse magnetic (TM) wave, in a hollow waveguide with only one conductor.

[0028] The transverse electric field (TE) mode is characterized by having a magnetic field only along the propagation direction, and no electric field in the propagation direction.

[0029] In TE mode, the electrical vector (E) is always perpendicular to the direction of propagation.

[0030] The fundamental mode of a waveguide is the mode with the lowest cutoff frequency. In the case of a rectangular waveguide, TE 10 The mode is the basic mode.

[0031] The rectangular waveguide may be a standard 3.4-inch waveguide such as a WR-340 waveguide. However, it is also possible to use rectangular waveguides of different dimensions by making appropriate adjustments.

[0032] Therefore, the rectangular waveguide has its basic TE at a frequency of 2.45 GHz. 10 It can operate in one mode. However, by applying appropriate adjustments, it is also possible to use other modes or different frequencies.

[0033] In some other embodiments, the microwave window pane includes a ceramic material such as an alumina ceramic material.

[0034] The microwave window pane may be constructed from a special low-loss alumina ceramic material. However, the material can be of various types with other dielectric properties, thereby adjusting the Brewster angle and iris size.

[0035] In some embodiments, the low-loss alumina ceramic material contains Al2O3 in a proportion between 92% and 99.9%, for example, 99.8% Al2O3. The low-loss alumina ceramic material may also contain trace amounts of other elements, such as Si at a concentration of 60 ppm, between 10 and 1000 ppm; Na at a concentration of 10 ppm, between 1 and 250 ppm; FE at a concentration of 60 ppm, between 1 and 100 ppm; and Mg at a concentration of 250 ppm, between 1 and 1000 ppm.

[0036] The low-loss alumina ceramic material may have a particle size of 0.5 to 35 μm and an average particle size of 6 μm.

[0037] In some further embodiments, the ceramic material is a low dielectric loss ceramic material.

[0038] Low dielectric loss, when measured according to ASTM-D150, is 10 -3 Less than, for example, 10 -4 It is called "less than".

[0039] A microwave window pane according to the present invention can be manufactured using a low-loss dielectric material.

[0040] These are sometimes called oxide ceramics or microwave ceramics.

[0041] The properties of microwave ceramics are determined by several parameters, including their composition, the purity of the starting material, processing conditions, and final density / porosity.

[0042] Low-loss dielectric materials ideal for microwave ceramics may have an optimized relative permittivity or dielectric constant (εr), low dielectric loss (low loss tangent, tanδ), a low resonant frequency temperature coefficient (τf), low shear strength / tensile strength, and a suitable Young's modulus.

[0043] Alkaline earth metals and rare earth elements are also used as low dielectric loss ceramic materials, including tantalates, niobates, titans, silicates, tungstates, molybdates, vanadates, and tellurates.

[0044] Other low dielectric loss materials may be used. For example, high-temperature glass ceramics such as Macor®, aluminum oxynitride such as ALON®, boron nitride, quartz, fused silica, diamond, sapphire, and beryllium oxide may be used as low dielectric loss ceramic materials according to the present invention.

[0045] In some embodiments, the ceramic material has a dielectric constant between 3 and 12, for example between 9 and 10.

[0046] This has the advantage of reducing the possibility of overmode / ghost modes, which are generally present in windows with high dielectric constant materials.

[0047] For example, the ceramic material of a microwave window pane may have a dielectric constant between 9.7 and 9.9, for example, 9.8.

[0048] According to the present invention, as the dielectric constant increases, the angle of the window pane with respect to the plane of the broad wall of the waveguide should decrease.

[0049] In this respect, the slightly higher the dielectric constant value, such as between 9.7 and 9.9, the smaller the angle, or longer the window pane, which allows for a more effective distribution of the force acting on the surface of the window pane.

[0050] In some further embodiments, the microwave window pane has a thickness of less than 10% of the microwave wavelength propagating through the rectangular waveguide during operation.

[0051] A microwave window pane with a thickness of less than 10% of the microwave wavelength propagating through the rectangular waveguide during operation has the advantage of preventing ghost modes and wave propagation through the microwave window pane.

[0052] Studies have shown that a microwave window pane with a thickness of less than 10% of the microwave wavelength propagating through a rectangular waveguide is the maximum allowable thickness to prevent the propagation of ghost modes and waves through the microwave window pane.

[0053] For example, microwave window panes with a thickness of 3 mm or less have been shown to prevent the propagation of ghost modes and waves through the microwave window pane.

[0054] The broadband microwave window assembly of the present invention has the advantage of being able to couple high-frequency, high-power microwave radiation within the waveguide when used with a rectangular waveguide, without causing overheating, significant accumulation of trap modes, or reflection of incident power.

[0055] However, in some embodiments, the presence of a cooling means may be advantageous.

[0056] In some embodiments, the broadband microwave window assembly further comprises means for cooling the microwave window pane.

[0057] The advantage of using a cooling method is that the cooling method reduces the stress on the window pane, thereby reducing the possibility of variations in the window pane's properties caused by temperature changes.

[0058] By using cooling methods, the temperature inside the broadband microwave window assembly can be reduced.

[0059] The means for cooling may be a channel having at least a portion of its outer surface in contact with the heat transfer surface surrounding the microwave window pane.

[0060] In some embodiments, the means for cooling is a fluid heat exchanger or includes a fluid heat exchanger.

[0061] The cooling fluid may be a liquid or a gas.

[0062] For example, a microwave window pane can be cooled using a countercurrent heat exchanger between two liquids.

[0063] In some further embodiments, the fluid heat exchanger is a water-cooled channel or includes a water-cooled channel.

[0064] The fluid heat exchanger may be equipped with means for further cooling.

[0065] For example, the fluid heat exchanger may have air-cooled fins, or may include air-cooled fins.

[0066] The use of this cooling method resulted in the creation of a broadband microwave window assembly capable of handling 10KW CW power without significantly increasing the temperature of the microwave window pane.

[0067] Other features that improve the usability of the broadband microwave window assembly according to one aspect of the present invention may exist.

[0068] In some embodiments, the broadband microwave window assembly further comprises means for inspecting the temperature of the microwave window pane.

[0069] The means for inspecting the temperature of the microwave window pane may be means for inspecting the temperature of the microwave window pane or the temperature in the microwave window pane.

[0070] In some further embodiments, the means for inspecting the temperature of the microwave window pane is an infrared (IR) sensor in a thermal camera inspection tube that monitors the temperature of the microwave window pane, or includes an infrared (IR) sensor in the thermal camera inspection tube.

[0071] The presence of an IR sensor within the thermal camera enables optimal temperature assessment of the microwave window pane.

[0072] A circular tube can be inserted into the broadband microwave window assembly to monitor the temperature of the microwave window pane.

[0073] The tube diameter can be designed to be small enough to cut off at 2.45 GHz. This allows for the insertion of an IR sensor into the tube to monitor the temperature of the microwave window pane.

[0074] In some embodiments, the inductive iris is adapted to the frequency and properties of the ceramic material, and the capacitive impedance of the window pane and the inductive impedance of the iris cancel each other out.

[0075] The induction iris is placed within the magnetic field and effectively acts as an obstacle within the window pane, providing an induction element.

[0076] The iris distributes a shunt inductance proportional to the size of the iris across the entire window pane.

[0077] The inductive iris of the present invention is matched to the frequency of the ceramic material of the window pane such that the inductive impedance of the iris cancels out the capacitive impedance of the window pane.

[0078] Generally, the dimensions of the iris may depend on the frequency and other parameters of the material used. For example, the cross-section of a rainbow iris may be 10 mm × 4.35 mm.

[0079] In a second aspect, the present invention relates to a single-mode microwave reactor system comprising: a single-mode microwave reactor having a reactor chamber and means for transmitting single-mode microwaves into a reactor chamber connected to the reactor chamber; a microwave generator and the broadband microwave window assembly of the first aspect of the invention, connecting the microwave generator to the single-mode microwave reactor.

[0080] A single-mode microwave reactor system is also called a single-dominant-mode microwave reactor system.

[0081] A single-mode or single-dominant-mode microwave reactor is defined herein as a reactor in which microwaves propagate substantially in a single mode.

[0082] The single mode or single dominant mode of propagation may be the transverse electric (TE) mode.

[0083] The broadband microwave window assembly of the present invention may be used in combination with a single-mode or single-dominant-mode microwave flow reactor that suppresses overmode propagation, thereby resulting in a more uniform electric field distribution for the material being processed.

[0084] The broadband microwave window assembly of the present invention, when combined with a single-mode or single-dominant-mode microwave flow reactor, provides a single-mode microwave reactor system capable of generating a uniform electromagnetic field distribution within the reactor.

[0085] Therefore, one application of a broadband microwave window assembly may include environmental and medical applications, microwave drying processes, food processing, inks and paints, and microwave heating applications for wood processing and agricultural uses.

[0086] Further applications of broadband microwave window assemblies may include radar and communications applications, materials processing related to microwave chemistry and inorganic or organic synthesis, biochemical reactions, polymer-related processes, and catalytic chemical processing.

[0087] Further applications of broadband microwave window assemblies may include radar and communications applications, materials processing related to microwave chemistry and inorganic or organic synthesis, biochemical reactions, polymer-related processes, and catalytic chemical processing.

[0088] In this respect, broadband microwave window assemblies can be used in several applications requiring high power transmission, such as medical or other high-power physical applications.

[0089] In a third aspect, the present invention relates to a method for manufacturing a broadband microwave window assembly of the first aspect of the invention, comprising assembling an identical half housing of the broadband microwave window assembly and securing the housing.

[0090] Fixing can be done by welding, screwing, or other fastening techniques.

[0091] The broadband microwave window assembly may be fabricated from four aluminum components assembled along the microwave window pane, at the center of the broad wall of the rectangular waveguide, and at the position of the microwave window pane.

[0092] The broadband microwave window assembly may be made from titanium and may be manufactured through additive manufacturing or 3D printing processes.

[0093] This assembly is determined by the fact that the surface current in the fundamental mode originates from the center of the broad wall of the waveguide. Therefore, no current flows at this assembly location, allowing for the mechanical separation of the structure.

[0094] The first and other aspects and embodiments of the present invention can each be combined with any of the other aspects and embodiments. These and other aspects of the present invention will become apparent and will be described by reference to the embodiments described below.

[0095] A broadband microwave window assembly with a Brewster waveguide window, a single-mode microwave reactor system with a waveguide having a Brewster waveguide window, and a method for manufacturing a waveguide having a Brewster waveguide window are described in more detail with reference to the accompanying drawings. The drawings illustrate one method of carrying out the present invention and are not limited to other possible embodiments included in the accompanying claims. [Brief explanation of the drawing]

[0096] [Figure 1] Figure 1 is a schematic diagram of a broadband microwave window assembly according to several embodiments of the present invention. [Figure 2] Figure 2 is a top view of a broadband microwave window assembly according to several embodiments of the present invention. [Figure 3A] Figure 3A is a side view showing the position of a cross-section of a broadband microwave window assembly according to several embodiments of the present invention, as shown in Figure 3B. [Figure 3B] Figure 3B is a cross-sectional view of a broadband microwave window assembly according to several embodiments of the present invention. [Figure 4A] Figure 4A is a side view showing the location of the cross-section in Figure 4B. [Figure 4B] Figure 4B is a cross-sectional view of a broadband microwave window assembly according to several embodiments of the present invention. [Figure 5] Figure 5 is a schematic diagram of a broadband microwave window assembly according to several embodiments of the present invention, showing a water-cooled channel. [Figure 6] Figure 6 is a cross-sectional view of a broadband microwave window assembly according to several embodiments of the present invention, showing an inductive iris. [Figure 7] Figure 7 is a cross-sectional view of the electric field in the microwave propagation direction within a broadband microwave window assembly according to several embodiments of the present invention. [Figure 8] Figure 8 is a cross-sectional view of the electric field perpendicular to the microwave propagation direction of the microwave window pane in a broadband microwave window assembly according to several embodiments of the present invention. [Figure 9] Figure 9 is a schematic diagram of a single-dominant mode microwave reactor system according to several embodiments of a second aspect of the present invention. [Figure 10] Figure 10 is a flowchart of a method for manufacturing a broadband microwave window assembly according to several embodiments of a third aspect of the present invention. [Modes for carrying out the invention]

[0097] Figure 1 is a schematic diagram of broadband microwave window assembly 1, showing some of the assembly's relevant features.

[0098] Figure 1 shows the position 2 of the rectangular waveguide 4 and the microwave window pane (not shown).

[0099] Figure 1 further shows the presence of cooling means, such as the cooling channel 3.

[0100] Figure 2 is a top view of the broadband microwave window assembly 1.

[0101] Figure 2 shows the microwave window pane 5, but the tilt relative to the microwave propagation direction according to the Brewster angle is not shown.

[0102] The presence of the induction iris 6 is indicated to be located on the sides surrounding the microwave window pane 5.

[0103] Figure 2 further shows the presence of cooling channel 3.

[0104] Figure 3B further shows a cross-sectional view of the broadband microwave window assembly 1.

[0105] Figure 3A is a side view showing the position of the cross-section of Figure 3B in the broadband microwave window assembly 1.

[0106] Figure 4B further shows a cross-sectional view of the broadband microwave window assembly 1.

[0107] Figure 4A is a side view showing the position of the cross-section of Figure 4B in the broadband microwave window assembly 1.

[0108] In Figure 4B, we can focus on the microwave window pane 5 and the cooling channel 3.

[0109] Figure 5 is a schematic diagram of the broadband microwave window assembly 7 showing the presence of the cooling channel 9.

[0110] Figure 5 also shows the position of the inspection tube 8 for inserting the IR sensor into the thermal camera, which enables optimal temperature evaluation of the microwave window pane.

[0111] Figure 6 is a cross-sectional view of the broadband microwave window assembly 7, showing the induction iris 10 at the edge of the microwave window pane 11.

[0112] Figure 7 is a cross-sectional view of the electric field 13 along the microwave propagation direction within a broadband microwave window assembly.

[0113] Figure 8 is a cross-sectional view of the electric field 14 in the microwave window pane of a broadband microwave window assembly, perpendicular to the microwave propagation direction.

[0114] Figure 9 is a schematic diagram of the single-dominant-mode microwave reactor system 15.

[0115] The single-mode microwave reactor system 15 comprises a single-mode microwave reactor 18, a microwave generator 16, and a broadband microwave window assembly 17 that connects the microwave generator 16 to the single-mode microwave reactor 18.

[0116] Figure 10 shows a flowchart 19 of a method for manufacturing a broadband microwave window assembly, and this method is - S1, Assemble the identical half housing of the broadband microwave window assembly. - S2, secure the housing Includes steps.

[0117] Although the present invention has been described in relation to specific embodiments, it should not be construed as being limited in any way to the examples presented. The scope of the present invention is defined by the appended claims. In the context of the claims, the term “comprising” or “comprises” does not preclude other possible elements or steps. Furthermore, references to references such as “a” or “an” should not be construed as precluding a plurality. The use of reference numerals in the claims with respect to elements shown in the drawings should also not be construed as limiting the scope of the present invention. Furthermore, individual features mentioned in different claims may be advantageously combined, and references to these features in different claims do not preclude the combination of features from being impossible or advantageous.

Claims

1. Fundamental wave TE １０ A broadband microwave window assembly configured to operate in waveguide mode, A rectangular waveguide and, A rectangular microwave window pane inclined with respect to the microwave propagation direction according to the Brewster angle, located within the rectangular waveguide, and having a thickness of less than 10% of the microwave wavelength, An induction iris is positioned around the rectangular microwave window pane, and the capacitive load of the rectangular waveguide is adjusted. A broadband microwave window assembly characterized by comprising the following features.

2. The broadband microwave window assembly according to claim 1, characterized in that the rectangular microwave window pane includes a ceramic material.

3. The aforementioned ceramic material is a low dielectric loss ceramic material. The broadband microwave window assembly according to claim 2, characterized in that the low dielectric loss is called less than 10⁻³ when measured according to ASTM-D150.

4. The broadband microwave window assembly according to claim 2 or 3, characterized in that the ceramic material has a dielectric constant between 3 and 12.

5. The broadband microwave window assembly according to any one of claims 1 to 3, further comprising means for cooling the rectangular microwave window pane.

6. The broadband microwave window assembly according to claim 5, characterized in that the means for cooling is a fluid heat exchanger or includes a fluid heat exchanger.

7. The broadband microwave window assembly according to claim 6, characterized in that the fluid heat exchanger is a water-cooled channel or includes a water-cooled channel.

8. The broadband microwave window assembly according to claim 6, characterized in that the fluid heat exchanger is an air-cooled fin or includes an air-cooled fin.

9. The broadband microwave window assembly according to any one of claims 1 to 3, further comprising means for inspecting the temperature of the rectangular microwave window pane.

10. The broadband microwave window assembly according to claim 9, wherein the means for inspecting the temperature of the rectangular microwave window pane is an infrared (IR) sensor in a thermal camera inspection tube for monitoring the temperature of the rectangular microwave window pane, or includes an infrared (IR) sensor in a thermal camera inspection tube.

11. The broadband microwave window assembly according to claim 2 or 3, characterized in that the inductive iris is matched to the frequency and characteristics of the ceramic material, thereby canceling out the capacitive impedance of the rectangular microwave window pane and the inductive impedance of the inductive iris.

12. A single-mode microwave reactor comprising a reactor chamber and means for transmitting single-mode microwaves into the reactor chamber connected to the reactor chamber, microwave generator and The broadband microwave window assembly according to any one of claims 1 to 3, wherein the microwave generator is connected to the single-mode microwave reactor, A single-mode microwave reactor system characterized by comprising the following features.

13. Assembling the same half of the housing for the broadband microwave window assembly, To fix the aforementioned housing and A method for manufacturing a broadband microwave window assembly according to any one of claims 1 to 3, characterized by including the following:

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