TWI675609B - Method for distributed microwave phase control - Google Patents

Abstract

A distributed microwave phase control method includes: allowing a plurality of phase-controlled power modules to input microwaves into a cavity through each input port, so that the microwaves in the cavity exhibit a first electric field distribution; and each phase-controlled power mode The group adjusts the phase of the microwave input from each input port to the chamber, so that the microwave in the chamber generates a second electric field distribution complementary to the first electric field distribution due to the change in phase.

Description

Distributed microwave phase control method

The invention relates to a microwave control technology, in particular to a distributed microwave phase control method.

The traditional microwave heating technology uses the magnetron to generate microwaves to heat the object to be heated. However, the electric field strength distribution of the microwaves in this heating method tends to be uneven, making the part of the object to be heated located in the weak electric field area weak in absorption intensity Low heating area without significant heating, and the part of the object to be heated located in the strong electric field area will generate significantly heated high heating area due to strong absorption of the electric field, so the heated object will be heated by microwave heating Uneven condition.

In addition, in order to increase the temperature of the object to be heated in the low-heat-receiving area, the intensity distribution of the electric field can generally be changed through a mechanical turntable or a microwave stirrer, but its effect is still limited.

Therefore, how to effectively perform regional heating or overall uniform heating is really one of the issues to be urgently addressed in the industry.

The invention provides a distributed microwave phase control method, which includes: providing a housing with a cavity inside, and forming a plurality of input ports communicating with the cavity on the housing; and allowing a plurality of phased power modules to pass through. Each input port inputs microwaves into the chamber, so that the microwaves in the chamber exhibit a first electric field distribution; and each phase-controlled power module adjusts the phase of the microwaves input into the chamber by each input port, so that the Due to the change in phase, the microwave generates a second electric field distribution that is complementary to the first electric field distribution.

It can be known from the above that the present invention utilizes a distributed input port array formed on the casing, and then provides microwaves with different phases to the input port through the phased power module to input the input port to the chamber, and can actively control the microwave in the chamber. The transformation of the electric field strength distribution at different stages, and the microwave electric field in the chamber at different stages present complementary electric field distributions to each other, so that the heated objects in the chamber get more uniform heating from the complementary electric field distributions at different stages. , Thereby improving the phenomenon of uneven heating of traditional heaters.

The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this specification are only used to match the content disclosed in the specification for the understanding and reading of those skilled in the art, and are not intended to limit the implementation of the present invention. The limited conditions are not technically significant. Any modification of the structure, change of the proportional relationship, or adjustment of the size should still fall within the scope of this invention without affecting the effects and goals that can be achieved by the present invention. The technical content disclosed by the invention can be covered. At the same time, the terms such as "first", "second" and "third" used in this specification are only for the convenience of description, and are not intended to limit the scope of the invention and their relative relationship. Changes or adjustments without substantial changes in technical content shall be deemed to be the scope of the present invention.

Please refer to FIG. 1, which is a schematic diagram of a system to which the distributed microwave phase control method of the present invention is applied. The system includes: a housing 1 having a cavity 5 inside; a plurality of input ports located in the housing. 1 is connected to the chamber; a plurality of phase-controlled power modules 2 are connected to the input ports to provide microwaves to the input ports so that each of the input ports inputs the microwave into the chamber 5; The interface 3 is provided to connect with each of the phase-controlled power modules 2; and the microprocessor 4 is connected to the serial peripheral interface 3 and control the output of each phase-controlled power module 2 through the serial peripheral interface 3 The power and phase of the microwave.

Please refer to FIG. 2, which is a schematic flowchart of the distributed microwave phase control method of the present invention, which includes: in step S1, providing a housing 1 having a cavity 5 inside; in step S2, providing the housing 1 A plurality of input ports connected to the chamber 5 are formed thereon; in step S3, the plurality of phase-controlled power modules 2 are provided with microwaves to each of the input ports so that the input ports input the microwaves into the chamber 5 and further Make the microwaves in the chamber 5 exhibit a first electric field distribution; and in step S4, make each phase-controlled power module 2 adjust the phase of the microwaves input to the chamber by each of the input ports so that the Due to the change in phase, the microwave generates a second electric field distribution that is complementary to the first electric field distribution.

In one embodiment, the casing 1 is rectangular, cylindrical or polygonal, but not limited thereto.

Please refer to FIG. 3, which is a perspective view of a first arrangement embodiment of a rectangular housing 1 provided with a plurality of input ports, wherein the housing 1 is provided with an input of a circular array symmetrical to each other up, down, left, and right. Ports port1 ~ port4.

In an embodiment, the design dimension of the cavity 5 of the housing 1 is: the length of the Z axis of the cavity 5 is an integer multiple of λ (microwave wavelength), and the length of the X and Y axes of the cavity 5 is an integer Double λ or the integer multiple λ plus 0.5λ, but not limited to this.

Please refer to FIG. 4, which are electric field distribution diagrams of steps S3 and S4 in the distributed microwave phase control method of the casing 1 of FIG. 3 according to the present invention, where 1 [1,0] refers to port1 [peak The power is 1 watt, the phase of the microwave is 0 degrees], and so on, and the size of the chamber 5 of the housing 1 can be divided into four according to the design rules of the size of the chamber 5. The first is 1.5 Multiples of λ * 1.5λ * 1λ, the second is a multiple of 2λ * 2λ * 1λ, the third is a multiple of 2.5λ * 2.5λ * 1λ, and the fourth is a multiple of 3λ * 3λ * 1λ.

It can be seen from Figure 4 that the electric field distribution diagram distinguishes different electric field strengths according to different gray scale colors. Among them, the gray scale colors represent light field strength from low to high, and the first electric field distribution and the second electric field distribution are complementary. When the electric field distribution map is superimposed with the first electric field distribution map, the weak electric field area in the first electric field distribution map (for example, the middle area) overlaps the strong electric field area in the second electric field distribution map (for example, the middle area), or The weak electric field region in the second electric field distribution map (for example, the middle region) overlaps the strong electric field region in the first electric field distribution map (for example, the middle region).

The step S3 is to enable each phase-controlled power module 2 to provide microwaves of the same phase to each of the input ports port1 to port4, so that each of the input ports port1 to port4 can input microwaves of the same phase to the chamber 5 and thus the chamber 5 The microwaves present a first electric field distribution, wherein the first electric field distribution is in the form of a standing wave.

In an embodiment, the step S4 causes the phase-controlled power modules 2 to adjust the microwaves input from the symmetrical input ports to the chambers to have opposite phases to each other (for example, the inputs of the port1 and port3 are 0 to each other). Or 180-degree microwaves with opposite phases), so that the microwave in the chamber produces a second electric field distribution that is complementary to the first electric field distribution due to the phase change, wherein the second electric field distribution is in the form of a standing wave.

In an embodiment, the step S4 is to cause each phase-controlled power module 2 to adjust the microwaves input to the chamber by adjacent input ports to have opposite phases to each other (for example, the adjacent port1 and port2 inputs are 0 to each other). Or 180-degree microwaves with opposite phases), so that the microwave in the chamber produces a second electric field distribution that is complementary to the first electric field distribution due to the phase change, wherein the second electric field distribution is in the form of a standing wave.

In an embodiment, the step S4 is to cause the phase-controlled power modules 2 to sequentially adjust the microwaves of the input ports (such as port1 to port4) in the direction of the angle of the various positions of the housing 1 to sequentially The phase difference causes the microwave in the chamber to generate a second electric field distribution in the form of a phase-matched wave due to a change in phase.

Please refer to FIG. 5, which is a graph of the electric field between the input port port1 and the input port port2 when the size of the chamber 5 in FIG. 4 is 2λ * 2λ * 1λ.

The first electric field curve 51 represents the electric field curve in the form of a standing wave between the input port port1 and the input port port2 when the phases of the microwaves of the input ports port1 to port4 are in the same phase. The second electric field curve 52 represents the input port port1 to port4. An electric field curve in the form of a standing wave between input ports port1 and input port2 when adjacent input ports are in opposite phases, where node A of the electric field curve represents a weak electric field region, and peak B or trough C in a strong electric field region It is a higher electric field value in the strong electric field region. In contrast, the closer the strong electric field region is to the node A, the smaller the electric field value is.

It can be seen from FIG. 5 that the position of the node A of the first electric field curve 51 is located in the strong electric field region when the second electric field curve 52 is located, and the position of the node A of the second electric field curve 52 is located in the strong electric field when the first electric field curve 51 is located In other words, the complementary definition of the electric field curve is that when the first electric field curve 51 and the second electric field curve 52 overlap each other, the position of the node A of the first electric field curve 51 is located in the strong electric field area of the second electric field curve 52, or The position of the node A of the second electric field curve 52 is located in the strong electric field region of the first electric field curve 51. It should be understood that, because the standing wave is the original oscillating, the node position of the standing wave will not change with time. Secondly, because the input port port is the microwave feeding point, the first electric field curve 51 and the first standing wave form The two electric field curves 52 are located at the peak B or the valley C of the highest electric field value at the boundary between the input port port1 and the input port port2. In addition, it can be seen from FIG. 5 that the first electric field curve 51 and the second electric field curve 52 present a substantially complementary distribution in the middle region between the input port port1 and the input port port2.

Please refer to Fig. 6, which is a schematic diagram of the phase matching wave of the present invention. The casing 1 in Fig. 6 is a plan view of the casing 1 in Fig. 3. It is assumed that the phase of the microwave provided by the input port port1 is 0 degrees, The phase of the microwave provided by input port port2 is 90 degrees, the phase of the microwave provided by input port port3 is 180 degrees, the phase of the microwave provided by input port port4 is 270 degrees, and the microwave in the form of a standing wave 61 shown by a thin arrow It will be transmitted from the input port with a low phase to the input port with a high phase, and the input ports port1 to port4 are arranged on the casing 1 in a circular array. Therefore, a microwave in the form of a standing wave 61 indicated by a thin arrow will be transmitted from the input port Port1 to input port port4 generate a loop to form a phase-matched wave 62 shown by a thick arrow. Since the phase-matched wave 62 moves on a circular path, the node position of the phase-matched wave 62 will change with time.

Please refer to FIG. 7, which is a second electric field distribution diagram of the phase matching wave of FIG. 4 circulating in the chamber 5 of FIG. 3 according to the present invention. The four states of the phase matching wave in FIG. The phase matches the cycle of the phase-matching wave in the chamber 5. When the phase-matching wave is in the first state, the phase-matching wave is located at the input ports port1 to port4 and the phases are 0, 90, 180, and 270 degrees, respectively. In the second aspect, the phases of the phase-matching waves at input ports port1 to port4 are 45, 135, 225, and 315 degrees, respectively. When the phase-matching wave is in the third aspect, the phase-matching waves are at the phase of input ports port1 to port4. 90, 180, 270, and 0 degrees, respectively. When the phase matching wave is in the fourth state, the phases of the phase matching wave at the input ports port1 to port4 are 135, 225, 315, and 45 degrees, respectively.

It can be seen from FIG. 7 that the second electric field distribution diagram of the four aspects of the phase matching wave circulating in the chamber 5 is also substantially complementary to the energy generated by the first electric field distribution diagram of FIG. 4.

In an embodiment, if the phase-matched wave is to be more uniformly distributed in the chamber 5, that is, its electric field distribution has the best geometric symmetry characteristic, and the phase difference of the microwave input port is designed as follows: There are N input ports in a circle in the azimuth direction of the chamber. If the phase difference between adjacent input ports is the same, the phase difference is about (360 / N) degrees or a multiple thereof. If the phase difference is different, the input ports have two phases. The sum of the angles of the differences is about 360 degrees or a multiple thereof.

Taking a more uniformly distributed phase matching wave in chamber 5 in Fig. 3 as an example, since there are 4 input ports in a circle along the azimuth direction of chamber 5 in Fig. 3, the phase difference between each input port The preferred design is 360 degrees / 4 = 90 degrees, and the phases of the microwaves of the four input ports are 0, 90, 180, and 270 degrees, respectively. From this, it can be seen that the input port port1 of the phase-matching wave in Figure 4 is formed. The phase difference between port4 is a better design.

In an embodiment, the phase-matching wave is not limited to the input ports port1 to port4 of the circular array symmetrically arranged up and down, left and right, as shown in FIG. 3, and can also be provided by the input ports of the asymmetric circular array, such as The housing 1 shown in FIG. 3 is formed with 6 asymmetrical annular array input ports around the cavity 5 and a preferred design of the phase difference between each input port is 360 degrees / 6 = 60. Degrees, the phases of the microwaves of the six input ports are 0, 60, 120, 180, 240, and 300 degrees, respectively.

Referring to FIG. 8, a circular thin sheet of the object 6 is placed in the chamber 5 shown in FIG. 3.

Please refer to FIG. 9 at the same time, which is a temperature distribution diagram of three heating methods of the heated object 6 in FIG. 8 according to the present invention. Among them, a thick circular line represents the heated object 6, and the temperature distribution diagram varies according to different gray levels. The gradation color distinguishes different temperatures, where the gray-scale color from light to dark represents the temperature from low to high.

The first heating method: Step S3 is performed, and each phase-controlled power module 2 adjusts the microwaves inputted from the input ports port1 to port4 into the chamber 5 to the same phase and the power of 100W, and is input to the chamber 5 for 300 seconds. The object to be heated 6 is heated. It can be seen from FIG. 9 that the temperature distribution of the heated object 6 after being heated by the first heating method for 300 seconds is 74.4 degrees.

The second heating method: Step S4 is performed, and each phase-controlled power module 2 adjusts the microwave input from each of the input ports port1 to port4 into the chamber 5 to a phase-matched wave with a power of 100W and is input to the chamber for 300 seconds. 5 The object to be heated 6 is heated. It can be seen from FIG. 9 that the temperature distribution of the heated object 6 after being heated by the second heating method for 300 seconds differs by 47.4 degrees.

The third heating method: the first heating method lasts for 150 seconds and the second heating method lasts for 150 seconds. From Figure 9, it can be seen that the combined application of the first heating method and the second heating method is applied to the object to be heated. 6 The difference in the temperature distribution between heating and heating is only 34.4 degrees. It can be seen that the combined application of step S3 and step S4 can improve the problem that the temperature distribution of the heated object 6 is greatly different after step S3 or step S4. In other words, in The combination of steps S3 and S4 in a fixed heating time can greatly reduce the temperature difference of the object 6 to be heated.

Please refer to FIG. 10, which is a perspective view of a second embodiment in which a plurality of input ports are provided on a rectangular housing 1, in which three-dimensional arrays of input ports symmetrical to each other are formed on six faces of the rectangular housing 1. port1 ~ port6, and a spherical object 6 is placed in the chamber 5.

Please also refer to FIG. 11 at the same time, which is a temperature distribution diagram of the heating object 6 heated in three groups in FIG. 10 according to the present invention, wherein the thick circular line represents the heating object 6, and the temperature distribution diagram varies according to Grayscale colors distinguish between different temperatures, where grayscale colors from light to dark represent temperatures from low to high.

The first group of heating methods: Step S3 is performed, in which each phase-controlled power module 2 adjusts the microwaves input into the chamber 5 from the input ports port1 to port6 to the same phase and the power is 100W, and is input to the chamber for 300 seconds. The chamber 5 heats the object 6 to be heated. It can be seen from FIG. 11 that the temperature distribution of the heated object 6 after being continuously heated by the first heating method for 300 seconds is 46.4 degrees.

The second group of heating methods: Step S4, in which at least one group of symmetrical input ports port5 and port6 in the input port are first connected to the matching terminal (in one embodiment, the matching terminal system may be an impedance, but this is not the case) To limit), so that at least one set of symmetrical input ports port5 and port6 does not provide microwave input to the chamber 5, and then each phased power module 2 makes adjacent input ports port1 ~ port4 input to the microwave adjustment of the chamber The objects to be heated 6 are heated in the opposite phase to each other with a power of 100 W and input to the chamber 5 for 300 seconds. It can be seen from FIG. 11 that the temperature distribution of the heated object 6 after being continuously heated by the second heating method for 300 seconds differs by 25.3 degrees.

The third group of heating methods: the first group of heating methods lasts for 100 seconds and the second group of heating methods lasts for 200 seconds. From Figure 11, it can be seen that the first group of heating methods and the second group of heating methods are used in conjunction with the heated object 6 The difference in the temperature distribution after heating is only 17.2 degrees. It can be seen that the combined application of step S3 and step S4 can improve the problem that the temperature distribution of the heated object 6 after step S3 or step S4 is performed separately is very different. In other words, the fixed Using the combined application of steps S3 and S4 during the heating time can greatly reduce the temperature difference of the object 6 to be heated.

Please refer to FIG. 12, which is a perspective view of a third embodiment in which a plurality of input ports are provided on a rectangular casing 1, wherein the input ports port1 of a line array symmetrical to each other are formed on the casing 1. ~ port2, and a carrier 7 and a heated object 6 on the carrier 7 are attached to the bottom of the center of the chamber 5.

Please refer to FIG. 13 at the same time, which is the sectional electric field distribution diagram of the chamber after adjusting the phase of the microwave of the input ports port1 to port2 of the twelfth diagram of the present invention. The electric field distribution diagram shown in FIG. 13 is according to different gray levels. The gray color indicates different electric field strengths. The gray scale color represents light field strength from low to high, and the dotted circle represents the strong electric field area located on the surface of the heated object 6. According to Fig. 13, it can be seen that the strong electric field strength is located on the surface of the heated object 6. The position of the electric field area will be shifted with the adjustment of the microwave phase of the input ports port1 ~ port2. Therefore, the adjustment of the microwave phase at different stages can make the microwaves in the chamber 5 generate complementary electric fields at different stages. Electric field distribution, so that the heated object 6 gets more uniform heating from the complementary electric field distribution at different stages. In other words, the distributed microwave phase control method of the present invention can also change the microwave of each input port in step S3. Phase, as long as the electric field distribution diagram of the chamber 5 in step S4 and the electric field distribution diagram of the chamber 5 in step S3 present complementary forms, this is the spirit of the present invention. Furthermore, the distribution of the present invention The arrangement of the plurality of input ports on the casing 1 to which the microwave phase control method is applicable is not limited to the above. For example, the arrangement of the plurality of input ports on the casing 1 may also be an asymmetric three-dimensional array or a ring array. But not limited to this.

Please refer to FIG. 14, which is a schematic diagram of the present invention applied to a cylindrical casing 1, in which an array of a plurality of input ports can be arranged in layers on the cylindrical casing 1, and △ Φ1 to △ Φ4 are shown as individual layers. The phase of the microwave provided by the input port, Δθ1 and Δθ2 represent the phase difference of the microwaves between the layers, and in the electric field distribution 8 generated by the microwave provided by the input port, the circle indicated by S represents the strong electric field region and W The indicated circle represents a weak electric field region. Through the distributed microwave phase control method of the present invention, the distribution of the strong electric field region and the weak electric field region can be switched, so that the object to be heated in the electric field distribution can be heated more uniformly. .

As can be known from the above, the present invention utilizes a distributed input port array formed on the casing, and then provides microwaves of different phases through the phase-controlled power module to the input port to enter the chamber, and the microwave in the chamber can be actively controlled. The transformation of the electric field strength distribution at different stages, and the microwave electric field in the chamber at different stages present complementary electric field distributions to each other, so that the heated objects in the chamber can be heated more uniformly from the complementary electric field distributions at different stages. Furthermore, the phenomenon of uneven heating of the traditional heater is improved.

The above embodiments are used to exemplify the principle of the present invention and its effects, but not to limit the present invention. Anyone skilled in the art can modify the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention should be listed in the scope of patent application described later.

1‧‧‧shell

2‧‧‧phase-controlled power module

3‧‧‧Serial Peripheral Interface

4‧‧‧ Microprocessor

5‧‧‧ chamber

6‧‧‧ Object to be heated

7‧‧‧ carrier

8‧‧‧ Electric field distribution

51‧‧‧First electric field curve

52‧‧‧second electric field curve

61‧‧‧ standing wave

62‧‧‧phase matching wave

A‧‧‧node

B‧‧‧ crest

C‧‧‧Po Valley

Port‧‧‧Input port

Steps S1 ~ S4‧‧‧‧

FIG. 1 is a schematic diagram of a system to which the distributed microwave phase control method of the present invention is applied;

FIG. 2 is a schematic flowchart of a distributed microwave phase control method according to the present invention;

Figure 3 is a perspective view of a first embodiment of an input port of the present invention on a rectangular casing;

Fig. 4 is an electric field distribution diagram of the chamber in Fig. 3 of the present invention;

FIG. 5 is a graph of the electric field between the input port port1 and the input port port2 when the chamber size of FIG. 4 is 2λ * 2λ * 1λ;

FIG. 6 is a schematic diagram of a phase matching wave of the present invention;

FIG. 7 is an electric field distribution diagram of a phase matching wave in a cycle according to FIG. 4 of the present invention; FIG.

FIG. 8 is a schematic view of a heated object placed in a cavity sheet in the cavity shown in FIG. 3 of the present invention; FIG.

Fig. 9 is a temperature distribution diagram of the object to be heated in Fig. 8 of the present invention;

FIG. 10 is a perspective view of a second embodiment of an input port of the present invention on a rectangular casing;

FIG. 11 is a temperature distribution diagram of an object to be heated according to FIG. 10 of the present invention; FIG.

FIG. 12 is a perspective view of a third embodiment of an input port of the present invention on a rectangular casing;

Figure 13 is a sectional electric field distribution diagram of the chamber of Figure 12 of the present invention; and

Fig. 14 is a schematic view of a cylindrical casing according to the present invention.

Claims (13)

A distributed microwave phase control method includes: providing a housing with a cavity inside, and a plurality of input ports communicating with the cavity are formed on the housing; and a plurality of phase-controlled power modules are connected to the input port through the input port. The microwave is input into the chamber so that the microwave in the chamber exhibits a first electric field distribution; and each of the phased power modules adjusts the phase of the microwave input from each of the input ports to the chamber so that the chamber Due to the phase change, the microwave in the microwave generates a second electric field distribution that is complementary to the first electric field distribution; wherein the second electric field distribution that is complementary to the first electric field distribution refers to the second electric field distribution map and the first electric field distribution. When the distribution maps overlap, the weak electric field region in the middle region of the first electric field distribution map overlaps the strong electric field region in the middle region of the second electric field distribution map, or the The weak electric field region overlaps the strong electric field region in the middle region of the first electric field distribution map. The method according to item 1 of the scope of patent application, wherein a plurality of input ports of a symmetrical array are formed on the casing. The method according to item 2 of the scope of patent application, wherein each of the phase-controlled power modules provides microwaves of the same phase to each of the input ports, so that each of the input ports inputs the microwaves of the same phase into the chamber, Furthermore, the microwaves in the chamber exhibit the first electric field distribution. The method according to item 3 of the scope of patent application, wherein each of the phase-controlled power modules adjusts the microwave input from the input port to the chamber into opposite phases to each other, so that the microwave factor in the chamber The change in phase produces a second electric field distribution that is complementary to the first electric field distribution, wherein the first electric field distribution and the second electric field distribution are in the form of standing waves, and the node positions of the standing waves do not change with time. The method according to item 3 of the scope of patent application, wherein each of the phase-controlled power modules adjusts the microwave input from the adjacent input port to the chamber to have opposite phases to each other, so that the microwave factor in the chamber is The change in phase produces a second electric field distribution that is complementary to the first electric field distribution, wherein the first electric field distribution and the second electric field distribution are in the form of standing waves, and the node positions of the standing waves do not change with time. The method according to item 5 of the scope of patent application, wherein after generating the first electric field distribution, at least one group of symmetrical input ports in the input ports is connected to a matching terminal, so that the at least one group of symmetrical inputs The port does not provide microwave input to the chamber, and then each phase-controlled power module adjusts the microwave input from the adjacent input port to the chamber to have opposite phases to each other. The method according to item 3 of the scope of patent application, wherein each of the phase-controlled power modules sequentially adjusts the microwaves of the input ports in the direction of the azimuth angle of the casing to have a phase difference, The microwave in the chamber causes the second electric field distribution due to a change in phase. The method as described in item 7 of the scope of patent application, wherein the phase difference is designed in such a manner that there are N input ports in the direction of the azimuth angle of the housing, and the phase difference is (360 / N) degrees Or its multiples. The method according to item 7 of the scope of patent application, wherein the first electric field distribution is in the form of a standing wave, and the second electric field distribution is in the form of a phase-matched wave, wherein the node position of the standing wave does not change with time. , And the node position of the phase matching wave changes with time. The method according to item 1 of the patent application scope, wherein the shell and the cavity are rectangular, cylindrical or polygonal. The method according to item 2 of the application, wherein the symmetrical array is a line array, a three-dimensional array, or a circular array. The method according to item 1 of the scope of patent application, wherein the casing is formed with a plurality of input ports of an asymmetric array. The method according to item 12 of the application, wherein the asymmetric array is a three-dimensional array or a circular array.