Multi-frequency filter

Abstract

The present invention provides a multi-frequency filter, which includes a housing, a plurality of liquid metal grooves, and a plurality of first, second, and third electrodes. The housing includes a plurality of channels. These liquid metal grooves are respectively communicated with these channels. These first electrodes respectively extend into these liquid metal grooves to contact the liquid metal in these liquid metal grooves. These second electrodes and these third electrodes are respectively arranged in these channels. When a first voltage is applied to the first electrode and a second voltage is applied to the second electrode, the liquid metal in the liquid metal groove moves towards the second electrode, thereby forming a filter operating in the first frequency band. When a first voltage is applied to the first electrode and a third voltage is applied to the third electrode, the liquid metal in the liquid metal groove moves towards the third electrode, thereby forming a filter operating in the second frequency band. Therefore, the multi-frequency filter of the present invention can adjust the operating frequency band according to requirements.

Description

Technical Field

[0001] The present invention relates to a filter, and particularly to a multi - frequency filter. Background Art

[0002] Microwave filters can be mainly divided into two forms: lumped type and distributed type. The lumped type is composed of capacitor and inductor components, while the distributed type achieves corresponding capacitance and inductance values by changing the line width and line length of the transmission line. In high - frequency applications, the parasitic effects and losses inside the lumped components (Lumped elements) will be more significant as the frequency increases. Therefore, distributed components (distributed elements, such as microstrip lines) are often used instead.

[0003] Microstrip line filters have been widely used in RF front - end circuits. The main advantages of such filters are low cost, relatively wider bandwidth, and simple design process. How to use the architecture of microstrip line filters to make filters that can adjust the operating frequency band according to requirements is the current research direction. Summary of the Invention

[0004] The present invention provides a multi - frequency filter that can adjust the operating frequency band according to requirements.

[0005] A multi - frequency filter of the present invention includes a housing, a plurality of liquid metal grooves, a plurality of first electrodes, a plurality of second electrodes, and a plurality of third electrodes. The housing includes a plurality of channels. These liquid metal grooves are respectively communicated with these channels; these first electrodes respectively extend into these liquid metal grooves to contact the liquid metal in these liquid metal grooves. These second electrodes are respectively arranged in these channels. These third electrodes are respectively arranged in these channels. When a first voltage is applied to these first electrodes and a second voltage is applied to these second electrodes, the liquid metal in these liquid metal grooves moves towards these second electrodes, thereby forming a filter operating in the first frequency band. When a first voltage is applied to these first electrodes and a third voltage is applied to these third electrodes, the liquid metal in these liquid metal grooves moves towards these third electrodes, thereby forming a filter operating in the second frequency band.

[0006] In an embodiment of the present invention, the number of these second electrodes is the same as the number of these channels, and the distance between each of these second electrodes and the corresponding first electrode is an integer multiple of 1 / 4 of the wavelength of the first frequency band.

[0007] In an embodiment of the present invention, the number of these third electrodes is greater than the number of these channels. In the first part of these channels, a single third electrode is provided in each channel, and the distance between the third electrode and the corresponding first electrode is an integer multiple of 1 / 4 of the wavelength of the second frequency band.

[0008] In one embodiment of the present invention, in each channel, the distance between the second electrode and the nearest third electrode is an integer multiple of the minimum distance between the second electrode and the third electrode in the first part of these channels.

[0009] In one embodiment of the present invention, the above-mentioned channels extend in a first direction and are arranged in a second direction. In at least a part of these channels, the distance between the second electrode and the nearest third electrode increases along the second direction.

[0010] In one embodiment of the present invention, in the second part of these channels, two third electrodes are provided in each channel, and the distance between the two third electrodes is an integer multiple of 1 / 4 of the wavelength of the second frequency band.

[0011] In one embodiment of the present invention, in each of the second parts of these channels, the first electrode is located between the two third electrodes and is close to one of the third electrodes.

[0012] In one embodiment of the present invention, in each of the second parts of these channels, the distance between the first electrode and the nearest third electrode is an integer multiple of the minimum distance between the second electrode and the third electrode in the first part of these channels.

[0013] In one embodiment of the present invention, the above-mentioned channels extend in a first direction and are arranged in a second direction. In the second part of these channels, the distance between the first electrode and the nearest third electrode increases along the second direction.

[0014] In one embodiment of the present invention, the above-mentioned channels are parallel. In any two adjacent ones of these channels, the projection of one of the two channels on the plane where the other is located partially overlaps the other.

[0015] In one embodiment of the present invention, each of the above-mentioned channels includes opposite first and second ends. In each of these channels, the first electrode is located close to the first end, and the second electrode is located at the second end.

[0016] Based on the above, these liquid metal grooves of the multi - frequency filter of the present invention are respectively connected to these channels of the housing, and these first electrodes respectively extend into these liquid metal grooves to contact the liquid metal in these liquid metal grooves. These second electrodes and these third electrodes are respectively arranged in these channels. Through the above design, when a first voltage is applied to these first electrodes and a second voltage is applied to these second electrodes, the liquid metal in these liquid metal grooves moves towards these second electrodes, forming a filter operating in the first frequency band. When a first voltage is applied to these first electrodes and a third voltage is applied to these third electrodes, the liquid metal in these liquid metal grooves moves towards these third electrodes, forming a filter operating in the second frequency band. Therefore, the multi - frequency filter of the present invention can adjust the operating frequency band according to requirements, achieving the performance of multi - frequency filtering. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic partial cross - sectional view of a device using liquid metal as a filter;

[0018] Figure 2 is a top - view schematic diagram of a multi - frequency filter according to an embodiment of the present invention;

[0019] Figure 3 is Figure 2 a schematic diagram of the multi - frequency filter operating in the first frequency band;

[0020] Figure 4 is Figure 2 a schematic diagram of the multi - frequency filter operating in the second frequency band.

[0021] DESCRIPTION OF REFERENCE NUMERALS

[0022] D1: First direction;

[0023] D2: Second direction;

[0024] X, 2X, 3X, 4X: Distances;

[0025] 100: Multi - frequency filter;

[0026] 110: Housing;

[0027] 112, 112a, 112b, 112c, 112d: Channels;

[0028] 114: First end;

[0029] 116: Second end;

[0030] 118: Electrolyte;

[0031] 120: Liquid metal groove;

[0032] 122: Liquid metal;

[0033] 130: Circuit board;

[0034] 140: First electrode;

[0035] 150: Second electrode;

[0036] 160: Third electrode. Detailed implementation

[0037] Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same component symbols are used in the drawings and the description to represent the same or similar parts.

[0038] In addition to having the advantages of high conductivity, good heat dissipation effect, low insertion loss, and high radiation efficiency, liquid metal can have more applications due to its high fluidity as it remains liquid at normal temperature and in the atmosphere. The multi - frequency filter of the present invention utilizes liquid metal to implement a re - settable multi - band pass filter. The technical principle will be described below first with Figure 1 to illustrate the technical principle.

[0039] Figure 1 is a partial cross - sectional schematic view of a device using liquid metal as a filter. Please refer to Figure 1 . The channel 112 of the filter in this embodiment is formed by the housing 110. In this embodiment, the material of the housing 110 is, for example, Poly Dimethylsiloxane (PDMS), also known as silicone oil or PDMS for short. Poly Dimethylsiloxane has the characteristics of being colorless, odorless, non - toxic, and not easily volatile. Therefore, there are no safety concerns during production and the production method is simple. Also, because it is a transparent and colorless material, it is very conducive to observing the internal liquid flow path. Of course, the material of the housing 110 is not limited to this.

[0040] The channel 112 is filled with the electrolyte 118. The liquid metal tank 120 is located beside the channel 112 and communicates with the channel 112. There is liquid metal 122 in the liquid metal tank 120. The circuit board 130 is located below the channel 112 and includes the first electrode 140 and the second electrode 150. The first electrode 140 extends into the liquid metal tank 120, and the second electrode 150 is located at a position communicating with the channel 112.

[0041] When the liquid metal 122 contacts the electrolyte 118, the chemical interaction between the two causes the two contact surfaces between the liquid metal 122 and the electrolyte 118 to be charged, and this charged layer is called the electrical double layer (EDL). Since the electrical double layer will wrap the liquid metal 122 inside after formation, the liquid metal 122 can be regarded as a non-conductor in the electrolyte 118. Analyzing the two contact surfaces between the liquid metal 122 and the electrolyte 118 from a thermodynamic perspective, the relationship between the surface tension of the liquid metal 122 and the voltage difference across the electrical double layer can be obtained as follows.

[0042] This relationship is also called Lippman’s equation: Where γ is the surface tension of the liquid metal 122, C represents the unit capacitance generated by the electrical double layer, V0 is the internal pressure difference across the electrical double layer, and V is the externally applied voltage. From the above equation, since the quadratic term is always positive, γ has a maximum value of surface tension at V = V0.

[0043] Based on the above principle, if a positive bias voltage is applied to the first electrode 140 and a negative bias voltage is applied to the second electrode 150 respectively. Since the first electrode 140 contacts the liquid metal 122, the liquid metal 122 and the second electrode 150 contact the electrolyte 118, and the electrolyte 118 is a semiconductor. Through this relationship (Lippman’s equation), it can be understood that the liquid metal 122 undergoes surface oxidation, causing a potential gradient to form between the electrolyte 118 and the liquid metal 122 in the channel 112, generating a negative displacement pressure on the liquid metal 122. Also, since the liquid metal 122 has adhered to the electrode, the liquid metal 122 will quickly move along the channel 112 in the direction of the second electrode 150 (to the right) and be stretched.

[0044] That is to say, when the surface tension generated by the voltage difference exceeds the capillary pressure, the liquid metal 122 will be pulled in the direction of the electrode it is intended to reach. Therefore, the liquid metal 122 flows out of the liquid metal tank 120 and moves along the channel 112 in the direction of the second electrode 150, and a microstrip line filter can be formed. During the continuous application of the bias voltage, the liquid metal 122 will maintain the required extended length due to the oxide layer formed by the oxidation potential.

[0045] In addition, when the external bias voltage is removed, the oxidation potential is replaced by the reduction voltage, the oxide layer disappears, the surface tension of the liquid metal 122 is restored, and the liquid metal 122 will be pulled back into the liquid metal tank 120 by the viscous force with the first electrode 140, and has a reset effect.

[0046] It should be noted that the first electrode 140 and the second electrode 150 can be general conductor electrodes. In one embodiment, the first electrode 140 and the second electrode 150 can also be a coupler, an open stub filter, a switch, etc. The types of the first electrode 140 and the second electrode 150 are not limited thereto.

[0047] Hereinafter, a filter that can switch between two frequency bands will be taken as an example for illustration. However, the types of multi-frequency filters are not limited thereto. In other embodiments, the multi-frequency filter can support more than three operating frequency bands.

[0048] Figure 2 is a top view schematic diagram of a multi-frequency filter according to an embodiment of the present invention. Please refer to Figure 2 , the multi-frequency filter 100 of this embodiment can be selectively used as a filter for the first frequency band or a filter for the second frequency band. The first frequency band is, for example, a low frequency, and the second frequency band is, for example, a high frequency.

[0049] The multi-frequency filter 100 of this embodiment includes a housing 110 ( Figure 1 ), a plurality of liquid metal grooves 120, a plurality of first electrodes 140, a plurality of second electrodes 150, and a plurality of third electrodes 160.

[0050] As can be seen from Figure 2 , the housing 110 can be formed with a plurality of channels 112, 112a, 112b, 112c, 112d. In this embodiment, these channels 112, 112a, 112b, 112c, 112d are parallel, and these channels 112, 112a, 112b, 112c, 112d extend along the first direction D1 and are arranged along the second direction D2.

[0051] Among any two adjacent ones of these channels 112, 112a, 112b, 112c, 112d, the projection of one of the two channels on the plane where the other is located partially overlaps the other. Specifically, the channels 112, 112a partially overlap in the first direction D1, the channels 112a, 112b partially overlap in the first direction D1, the channels 112b, 112c partially overlap in the first direction D1, and the channels 112c, 112d partially overlap in the first direction D1.

[0052] The number of the liquid metal grooves 120 corresponds to the number of the channels 112, 112a, 112b, 112c, 112d. In this embodiment, there are five liquid metal grooves 120, and these five liquid metal grooves 120 are respectively communicated with these channels 112, 112a, 112b, 112c, 112d.

[0053] These first electrodes 140 respectively extend into these liquid metal tanks 120 to contact the liquid metal 122 within these liquid metal tanks 120. These second electrodes 150 are respectively disposed in these channels 112, 112a, 112b, 112c, 112d.

[0054] In this embodiment, the number of these first electrodes 140 is the same as the number of these channels 112, 112a, 112b, 112c, 112d, and the number of these second electrodes 150 is the same as the number of these channels 112, 112a, 112b, 112c, 112d.

[0055] That is to say, the channels 112, 112a, 112b, 112c, 112d, the first electrodes 140 and the second electrodes 150 correspond in number. Each of the channels 112, 112a, 112b, 112c, 112d is provided with a first electrode 140 and a second electrode 150.

[0056] In addition, in this embodiment, the distance between each of these second electrodes 150 and the corresponding first electrode 140 is an integer multiple of 1 / 4 of the wavelength of the first frequency band.

[0057] For Figure 2 example, each of these channels 112, 112a, 112b, 112c, 112d includes opposite first ends 114 (such as the left ends) and second ends 116 (such as the right ends). In each of these channels 112, 112a, 112b, 112c, 112d, the liquid metal tank 120 and the first electrode 140 are located near the first end 114, and the second electrode 150 is located at the second end 116.

[0058] Of course, in other embodiments, the channels 112, 112a, 112b, 112c, 112d may also be longer, such that the second electrode 150 is not located at the second end 116, and the relationship among the channels 112, 112a, 112b, 112c, 112d, the first electrode 140 and the second electrode 150 is not limited thereto.

[0059] In addition, these third electrodes 160 are respectively disposed in these channels 112, 112a, 112b, 112c, 112d. In this embodiment, the number of these third electrodes 160 is greater than the number of these channels 112, 112a, 112b, 112c, 112d. Therefore, in some of the channels 112, 112a, the number of the third electrodes 160 may be only one, and in some of the other channels 112b, 112c, 112d, the number of the third electrodes 160 is more than one.

[0060] By Figure 2It can be seen that in the first part of these channels 112, 112a, 112b, 112c, 112d (i.e., the channels 112, 112a in the upper two rows), a single third electrode 160 is provided in each of the channels 112, 112a. The third electrode 160 is located between the first electrode 140 and the second electrode 150 and is close to the second electrode 150. In addition, the distance between the third electrode 160 and the corresponding first electrode 140 is an integer multiple of 1 / 4 of the wavelength of the second frequency band.

[0061] In addition, in the second part of these channels 112, 112a, 112b, 112c, 112d (i.e., the channels 112b, 112c, 112d in the lower three rows), two third electrodes 160 are provided in each of the channels 112b, 112c, 112d. The distance between the two third electrodes 160 is an integer multiple of 1 / 4 of the wavelength of the second frequency band. In these channels 112b, 112c, 112d, the first electrode 140 is located between the two third electrodes 160 and is close to the third electrode 160 on the left.

[0062] It is worth mentioning that in this embodiment, in the channel 112 in the top row, the distance X between the second electrode 150 and the third electrode 160 is the minimum distance. In the channel 112a in the second row, the distance between the second electrode 150 and the third electrode 160 is 2X, that is, twice the minimum distance. In the channel 112b in the third row, the distance between the second electrode 150 and the adjacent third electrode 160 is 3X, that is, three times the minimum distance. In the channel 112c in the fourth row, the distance between the second electrode 150 and the adjacent third electrode 160 is 4X, that is, four times the minimum distance. In the channel 112d in the fifth row, the distance between the second electrode 150 and the adjacent third electrode 160 is 4X, that is, four times the minimum distance.

[0063] That is to say, in the channels 112, 112a, 112b, 112c, the distance between the second electrode 150 and the third electrode 160 it is close to increases along the second direction D2. And in each of the channels 112, 112a, 112b, 112c, 112d, the distances X, 2X, 3X, 4X between the second electrode 150 and the closest third electrode 160 are integer multiples of the distance X between the second electrode 150 and the third electrode 160 in the channel 112.

[0064] In addition, in the present embodiment, in the channel 112b of the third row, the distance between the first electrode 140 and the third electrode 160 (the third electrode 160 on the left) it is close to is X, which is the same as the distance X (the minimum distance) between the second electrode 150 and the third electrode 160 in the first row. In the channel 112c of the fourth row, the distance between the first electrode 140 and the third electrode 160 (the third electrode 160 on the left) it is close to is 2X. In the channel 112d of the fifth row, the distance between the first electrode 140 and the third electrode 160 (the third electrode 160 on the left) it is close to is 3X.

[0065] In each of the channels 112b, 112c, 112d, the distances X, 2X, 3X between the first electrode 140 and the third electrode 160 (the third electrode 160 on the left) it is close to are integer multiples of the distance X between the second electrode 150 and the third electrode 160 of the channel 112. In addition, in the channels 112b, 112c, 112d, the distances X, 2X, 3X between the first electrode 140 and the third electrode 160 (the third electrode 160 on the left) it is close to increase along the second direction D2.

[0066] When using Figure 2 the multi - frequency filter 100 as the filter for the first frequency band, Figure 3 it is Figure 2 a schematic diagram of the multi - frequency filter operating in the first frequency band. Please refer to Figure 3 , as long as a first voltage (such as a positive voltage) is applied to these first electrodes 140, and a second voltage (such as a negative voltage) is applied to these second electrodes 150. The liquid metal 122 in these liquid metal tanks 120 moves towards these second electrodes 150. Therefore, the extension lengths of the liquid metal 122 in these rows will be integer multiples of 1 / 4 of the wavelength of the first frequency band, and a filter operating in the first frequency band is formed.

[0067] For example, the extension length of the liquid metal 122 in the top - most row is, for example, one time 1 / 4 of the wavelength of the first frequency band, the extension length of the liquid metal 122 in the second row is, for example, two times 1 / 4 of the wavelength of the first frequency band, the extension length of the liquid metal 122 in the third row is, for example, two times 1 / 4 of the wavelength of the first frequency band, the extension length of the liquid metal 122 in the fourth row is, for example, two times 1 / 4 of the wavelength of the first frequency band, and the extension length of the liquid metal 122 in the fifth row is, for example, one time 1 / 4 of the wavelength of the first frequency band. Of course, the multiples of the extension length of the liquid metal 122 are not limited to this.

[0068] When using Figure 2 the multi - frequency filter 100 as the filter for the second frequency band, as long as the voltage application to the first electrode 140 and the second electrode 150 is stopped first to make the liquid metal 122 return to the liquid metal tank 120.

[0069] After resetting, a first voltage is applied to these first electrodes 140, and a third voltage is applied to these third electrodes 160. Figure 4 Yes Figure 2 Schematic diagram of the multi - frequency filter operating in the second frequency band. Please refer to Figure 4 , the liquid metal 122 in these liquid metal tanks 120 moves towards these third electrodes 160. Therefore, the extended length of the rows of liquid metal 122 will be an integer multiple of 1 / 4 of the wavelength of the second frequency band, forming a filter operating in the second frequency band.

[0070] For example, the extended length of the top - most row of liquid metal 122 is, for example, one times 1 / 4 of the wavelength of the second frequency band, the extended length of the second row of liquid metal 122 is, for example, two times 1 / 4 of the wavelength of the second frequency band, the extended length of the third row of liquid metal 122 is, for example, two times 1 / 4 of the wavelength of the second frequency band, the extended length of the fourth row of liquid metal 122 is, for example, two times 1 / 4 of the wavelength of the second frequency band, and the extended length of the fifth row of liquid metal 122 is, for example, one times 1 / 4 of the wavelength of the second frequency band. Of course, the multiple of the extended length of the liquid metal 122 is not limited to this.

[0071] It is worth mentioning that although in Figure 2 , the lengths of these channels 112, 112a, 112b, 112c, 112d are not all equal, in one embodiment, the lengths of these channels can also be equal. The lengths of these channels are, for example, more than twice 1 / 4 of the wavelength covering the required lowest frequency, so as to meet the condition that the microstrip lines required for all frequency bands can be made, and it is more convenient in manufacturing.

[0072] In summary, these liquid metal tanks of the multi - frequency filter of the present invention are respectively connected to these channels of the housing, and these first electrodes respectively extend into these liquid metal tanks to contact the liquid metal in these liquid metal tanks. These second electrodes and these third electrodes are respectively arranged in these channels. Through the above design, when a first voltage is applied to these first electrodes and a second voltage is applied to these second electrodes, the liquid metal in these liquid metal tanks moves towards these second electrodes, forming a filter operating in the first frequency band. When a first voltage is applied to these first electrodes and a third voltage is applied to these third electrodes, the liquid metal in these liquid metal tanks moves towards these third electrodes, forming a filter operating in the second frequency band. Therefore, the multi - frequency filter of the present invention can adjust the operating frequency band according to requirements, achieving the performance of multi - frequency filtering.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A multi - frequency filter, characterized in that, it includes: a housing including a plurality of channels; a plurality of liquid metal tanks respectively communicating with the plurality of channels; a plurality of first electrodes respectively extending into the plurality of liquid metal tanks to contact the liquid metal in the plurality of liquid metal tanks; a plurality of second electrodes respectively arranged in the plurality of channels; and a plurality of third electrodes respectively arranged in the plurality of channels, wherein when a first voltage is applied to the plurality of first electrodes and a second voltage is applied to the plurality of second electrodes, the liquid metal in the plurality of liquid metal tanks moves towards the plurality of second electrodes, forming a filter operating in a first frequency band; when a first voltage is applied to the plurality of first electrodes and a third voltage is applied to the plurality of third electrodes, the liquid metal in the plurality of liquid metal tanks moves towards the plurality of third electrodes, forming a filter operating in a second frequency band.

2. The multi - frequency filter according to claim 1, characterized in that, the number of the plurality of second electrodes is the same as the number of the plurality of channels, and the distance between each of the plurality of second electrodes and the corresponding first electrode is an integer multiple of 1 / 4 of the wavelength of the first frequency band.

3. The multi - frequency filter according to claim 1, characterized in that, the number of the plurality of third electrodes is greater than the number of the plurality of channels. In a first part of the plurality of channels, a single one of the third electrodes is provided in each of the channels, and the distance between the third electrode and the corresponding first electrode is an integer multiple of 1 / 4 of the wavelength of the second frequency band.

4. The multi - frequency filter according to claim 3, characterized in that, in each of the channels, the distance between the second electrode and the closest third electrode is an integer multiple of the minimum distance between the second electrode and the third electrode in the first part of the plurality of channels.

5. The multi - frequency filter according to claim 4, characterized in that, the plurality of channels extend along a first direction and are arranged along a second direction. In at least a part of the plurality of channels, the distance between the second electrode and the closest third electrode increases along the second direction.

6. The multi - frequency filter according to claim 3, characterized in that, in a second part of the plurality of channels, two of the third electrodes are provided in each of the channels, and the distance between the two third electrodes is an integer multiple of 1 / 4 of the wavelength of the second frequency band.

7. The multi - frequency filter according to claim 6, characterized in that, in each of the second parts of the plurality of channels, the first electrode is located between the two third electrodes and is close to one of the third electrodes.

8. The multi - frequency filter according to claim 7, characterized in that, in each of the second parts of the plurality of channels, the distance between the first electrode and the closest third electrode is an integer multiple of the minimum distance between the second electrode and the third electrode in the first part of the plurality of channels.

9. The multi - frequency filter according to claim 8, characterized in that, The plurality of channels extend in a first direction and are arranged in a second direction. In the second portion of the plurality of channels, the distance between the first electrode and the adjacent third electrode increases along the second direction.

10. The multi-frequency filter according to claim 1, wherein, the plurality of channels are parallel, and in any two adjacent ones of the plurality of channels, the projection of one of the two channels onto the plane of the other partially overlaps the other.

11. The multi-frequency filter according to claim 1, wherein, each of the plurality of channels includes opposite first and second ends. In each of the channels, the first electrode is located near the first end, and the second electrode is located at the second end.

Images