TWI773606B - Multi-frequency filter - Google Patents

Abstract

A multi-frequency filter includes a casing, liquid metal tanks, and first, second and third electrodes. The housing includes channels. The liquid metal tanks are respectively connected to the channels. The first electrodes respectively extend into the liquid metal tanks to contact liquid metal in the liquid metal tanks. The second electrodes and the third electrodes are respectively disposed in the channels. When a first voltage is applied to the first electrodes and a second voltage is applied to the second electrodes, the liquid metal in the liquid metal tanks moves to the second electrodes to form a filter operating in the first frequency band. When the first voltage is applied to the first electrodes and a third voltage is applied to the third electrodes, the liquid metal in the liquid metal tanks moves to the third electrodes to form a filter operating in the second frequency band.

Description

Multi-frequency filter

The present invention relates to a filter, and in particular to a multi-frequency filter.

Microwave filters can be mainly divided into two types, lumped type and distributed type. The lumped type is composed of capacitive and inductive elements, and the distributed type is to achieve the corresponding capacitance and inductance values by changing the line width and line length of the transmission line. In high-frequency applications, the lumped elements will increase with the frequency, and the parasitic effects and losses inside the elements will be more significant, so distributed elements (such as microstrip lines) are often used. replace.

Microstrip line filters have been widely used in RF front-end circuits. The main advantages of this filter are low cost, relatively wider bandwidth, and simple design process. How to use the structure of the microstrip filter to make a filter that can adjust the operating frequency band according to the needs is the current research direction.

The present invention provides a multi-frequency filter, which can adjust the operating frequency band as required.

A multi-frequency filter of the present invention includes a casing, a plurality of liquid metal tanks, a plurality of first electrodes, a plurality of second electrodes and a plurality of third electrodes. The housing includes a plurality of channels. The liquid metal grooves are respectively communicated with the channels; the first electrodes respectively extend into the liquid metal grooves to contact the liquid metal in the liquid metal grooves. The second electrodes are respectively disposed in the channels. The third electrodes are respectively disposed in the channels. When a first voltage is applied to the first electrodes, and a second voltage is applied to the second electrodes, the liquid metal in the liquid metal tanks moves to the second electrodes to form a filter operating in the first frequency band . When a first voltage is applied to the first electrodes and a third voltage is applied to the third electrodes, the liquid metal in the liquid metal tanks moves to the third electrodes to form a filter operating in the second frequency band .

In an embodiment of the present invention, the number of the above-mentioned second electrodes is the same as the number of the channels, and the distance between each of the second electrodes and the corresponding first electrode is 1/1 of the first frequency band 4 times the integer multiple of the wavelength.

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

In an embodiment of the present invention, in each channel, the distance between the second electrode and the closest third electrode is an integer multiple of the smallest distance between the second electrode and the third electrode in the first part of the channels .

In an embodiment of the present invention, the above-mentioned channels extend along a first direction and are arranged along a second direction, and in at least a part of the channels, the distance between the second electrode and the adjacent third electrode is along the increase in the second direction.

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

In one embodiment of the invention, in each of the second portions of the channels, the first electrode is located between the two third electrodes and is adjacent to one of the third electrodes.

In an embodiment of the invention, in each of the second portions of the channels, the distance between the first electrode and the adjacent third electrode is the distance between the second electrode and the third electrode in the first portion of the channels Integer multiple of the minimum distance between electrodes.

In an embodiment of the present invention, the above-mentioned channels extend along a first direction and are arranged along a second direction, and in the second part of the channels, the distance between the first electrode and the adjacent third electrode increase in the second direction.

In an embodiment of the present invention, the above-mentioned channels are parallel, and in any two adjacent channels, the projection of one of the two channels on the plane where the other is located partially overlaps the other.

In one embodiment of the present invention, each of the above-mentioned channels includes a first end and a second end opposite to each other, and in each channel, the first electrode is located near the first end and the second electrode is located at second end.

Based on the above, the liquid metal grooves of the multi-frequency filter of the present invention are respectively connected to the channels of the casing, and the first electrodes respectively extend into the liquid metal grooves to contact the liquid metal in the liquid metal grooves. The second electrodes and the third electrodes are respectively disposed in the channels. Through the above-mentioned design, when the first voltage is applied to the first electrodes, and the second voltage is applied to the second electrodes, the liquid metal in the liquid metal tank moves to the second electrodes, and the operation in the second electrode is formed. One-band filter. When a first voltage is applied to the first electrodes and a third voltage is applied to the third electrodes, the liquid metal in the liquid metal tanks moves to the third electrodes to form a filter operating in the second frequency band . Therefore, the multi-frequency filter of the present invention can adjust the operating frequency band as required, so as to achieve the performance of multi-frequency filtering.

In addition to the advantages of high conductivity, good heat dissipation, low insertion loss, and high radiation efficiency, liquid metal is still liquid in the atmosphere at room temperature. High flow characteristics, but can have more applications. The multi-frequency filter of the present invention utilizes liquid metal to realize a resettable multi-band pass filter. The technical principle will be described below with reference to FIG. 1 .

FIG. 1 is a partial cross-sectional schematic diagram of a device using liquid metal as a filter. Referring to FIG. 1 , the channel 112 of the filter in this embodiment is formed by the casing 110 . In this embodiment, the material of the casing 110 is, for example, Poly Dimethylsiloxane (PDMS), referred to as silicone oil or PDMS for short. Dimethylsiloxane is colorless, odorless, non-toxic and non-volatile. Therefore, there is no safety concern during production and the production method is simple, and because it is a transparent and colorless material, it is very beneficial to observe the internal liquid flow path. Of course, the material of the housing 110 is not limited thereto.

The channel 112 is filled with an electrolyte 118 . The liquid metal tank 120 is located beside the channel 112 and communicated with the channel 112 . The liquid metal tank 120 contains liquid metal 122 . The circuit board 130 is located under the channel 112 and includes a first electrode 140 and a second electrode 150 . The first electrode 140 extends into the liquid metal tank 120 , and the second electrode 150 is located at a position communicated with the channel 112 .

When the liquid metal 122 contacts the electrolyte 118, the chemical action between the two makes the two contact surfaces between the liquid metal 122 and the electrolyte 118 charged, and the charged layer is called an electrical double layer (EDL). After the formation of the electric double layer, the liquid metal 122 will be covered inside, so that the liquid metal 122 can be regarded as a non-conductor in the electrolyte 118 . From the thermodynamic analysis of the two contact surfaces between the liquid metal 122 and the electrolyte 118, the relationship between the surface tension of the liquid metal 122 and the voltage difference between the electric double layers can be obtained as follows.

，其中γ為液態金屬122表面張力，C代表由電雙層產生之單位電容，V ₀則是電雙層兩端內在壓差，而V為外部提供之電壓。由上面方程式可知，由於二次方項內恆正，故γ在V=V ₀為表面張力最大值。 This relation is also known as Lippman's equation:

, where γ is the surface tension of the liquid metal 122 , C represents the unit capacitance generated by the electric double layer, V ₀ is the internal pressure difference between the two ends of the electric double layer, and V is the externally supplied voltage. It can be seen from the above equation that since the quadratic term is constant and positive, γ is the maximum surface tension at V=V ₀ .

Based on the above principles, 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. It can be understood from Lippman's equation that the liquid metal 122 is oxidized on the surface, so that a potential gradient is formed between the electrolyte 118 and the liquid metal 122 in the channel 112 , and a negative displacement pressure is generated on the liquid metal 122 . And because the liquid metal 122 has been stuck on the electrode, the liquid metal 122 will quickly move to the direction of the second electrode 150 (rightward) along the channel 112 and be elongated.

That is, when the surface tension generated by the voltage difference exceeds the capillary pressure, the liquid metal 122 will be pulled toward the direction of the electrode to be reached. Therefore, the liquid metal 122 flows out of the liquid metal tank 120 and moves along the channel 112 toward the second electrode 150 , thereby forming a microstrip filter. During the continuous application of the bias voltage, the liquid metal 122 is maintained at the desired extension length due to the oxide layer formed by the oxidation potential.

In addition, when the external bias is removed, the oxidation potential is replaced by the reduction voltage, the disappearance of the oxide layer makes the surface tension of the liquid metal 122 recover, and the liquid metal 122 is pulled back to the liquid metal tank 120 by the viscous force between the liquid metal 122 and the first electrode 140 . , but has a resettable effect.

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

The following description will take a filter that can be switched between two frequency bands as an example, but the type of the multi-frequency filter is not limited by this. In other embodiments, the multi-frequency filter can support more than three operating frequency bands.

FIG. 2 is a schematic top view of a multi-frequency filter according to an embodiment of the present invention. Referring to FIG. 2 , the multi-frequency filter 100 of the present embodiment can be selectively used as a filter of a first frequency band or a filter of a second frequency band. The first frequency band is low frequency, for example, and the second frequency band is high frequency.

The multi-frequency filter 100 of this embodiment includes a casing 110 ( FIG. 1 ), a plurality of liquid metal tanks 120 , a plurality of first electrodes 140 , a plurality of second electrodes 150 and a plurality of third electrodes 160 .

2, the housing 110 may be formed with a plurality of channels 112, 112a, 112b, 112c, 112d. In this embodiment, the channels 112, 112a, 112b, 112c, 112d are parallel, and the channels 112, 112a, 112b, 112c, 112d extend along a first direction D1 and are arranged along a second direction D2.

In any two adjacent ones of these channels 112 , 112 a , 112 b , 112 c , and 112 d , the projection of one of the two channels to 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 Local overlap in direction D1.

The number of liquid metal tanks 120 corresponds to the number of channels 112, 112a, 112b, 112c, 112d. In this embodiment, there are five liquid metal tanks 120, and the five liquid metal tanks 120 are respectively connected to the channels 112, 112a, 112b, 112c, and 112d.

The first electrodes 140 respectively extend into the liquid metal tanks 120 to contact the liquid metal 122 in the liquid metal tanks 120 . The second electrodes 150 are disposed in the channels 112, 112a, 112b, 112c, 112d, respectively.

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

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

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

Referring to FIG. 2, each of the channels 112, 112a, 112b, 112c, 112d includes a first end 114 (eg, the left end) and a second end 116 (eg, the right end) opposite. In each of the channels 112 , 112 a , 112 b , 112 c , and 112 d , the liquid metal tank 120 and the first electrode 140 are located close to the first end 114 , and the second electrode 150 is located at the second end 116 .

Of course, in other embodiments, the channels 112, 112a, 112b, 112c, 112d can also be longer, so that the second electrode 150 is not located at the second end 116, the channels 112, 112a, 112b, 112c, 112d, the first electrode The relationship between 140 and the second electrode 150 is not limited thereto.

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

As can be seen from FIG. 2, in the first part of these channels 112, 112a, 112b, 112c, 112d (that is, the channels 112, 112a in the upper two rows), each channel 112, 112a is provided with a single third electrode 160, The three electrodes 160 are located between the first electrode 140 and the second electrode 150 and are 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 wavelength of the second frequency band.

In addition, in the second part of these channels 112, 112a, 112b, 112c, 112d (that is, the channels 112b, 112c, 112d in the lower three rows), there are two third electrodes 160 in each channel 112b, 112c, 112d , the distance between the two third electrodes 160 is an integer multiple of 1/4 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 located on the left.

It is worth mentioning that, in this embodiment, in the channel 112 in the uppermost row, the distance X between the second electrode 150 and the third electrode 160 is the minimum distance. In the channel 112a of the second row, the distance between the second electrode 150 and the third electrode 160 is 2X, which is twice the minimum distance. In the channel 112b of 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 of the fourth row, the distance between the second electrode 150 and the adjacent third electrode 160 is 4X, which is four times the minimum distance. In the channel 112d of 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.

That is, in the channels 112, 112a, 112b, and 112c, the distance between the second electrode 150 and the adjacent third electrode 160 increases along the second direction D2. In addition, in each channel 112 , 112 a , 112 b , 112 c , and 112 d , the distances X, 2X, 3X, and 4X between the second electrode 150 and the closest third electrode 160 are the distances X, 2X, 3X, and 4X between the second electrode 150 and the third electrode 160 of the channel 112 . An integer multiple of the distance X between the electrodes 160 .

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

In each of the channels 112b, 112c, 112d, the distances X, 2X, 3X between the first electrode 140 and the adjacent third electrode 160 (third electrode 160 on the left) are the second electrodes of the channel 112 An integer multiple of the distance X between 150 and the third electrode 160 . Furthermore, in the channels 112b, 112c, 112d, the distances X, 2X, 3X between the first electrode 140 and the adjacent third electrode 160 (the left third electrode 160) increase along the second direction D2.

When the multi-frequency filter 100 of FIG. 2 is used as the filter of the first frequency band, FIG. 3 is a schematic diagram of the multi-frequency filter of FIG. 2 operating in the first frequency band. Please refer to FIG. 3 , as long as a first voltage (eg, a positive voltage) is applied to the first electrodes 140 , and a second voltage (eg, a negative voltage) is applied to the second electrodes 150 . The liquid metal 122 in the liquid metal tanks 120 moves toward the second electrodes 150 . Therefore, the extension length of the liquid metal 122 in these rows is an integer multiple of 1/4 wavelength of the first frequency band, so as to form a filter operating in the first frequency band.

For example, the extension length of the liquid metal 122 in the top row is, for example, twice the wavelength of 1/4 times the wavelength of the first frequency band, and the extension length of the liquid metal 122 in the second row is, for example, 1/4 times the wavelength of the first frequency band. Twice the wavelength, the extension length of the liquid metal 122 in the third row is, for example, twice the wavelength of 1/4 times the wavelength of the first frequency band, and the extension length of the liquid metal 122 in the fourth row is, for example, 1/4 times the first frequency band. The extension length of the liquid metal 122 in the fifth row is, for example, twice the wavelength of 1/4 times the wavelength of the first frequency band. Of course, the multiple of the extension length of the liquid metal 122 is not limited to this.

To use the multi-frequency filter 100 of FIG. 2 as the filter of the second frequency band, it is only necessary to stop applying voltage to the first electrode 140 and the second electrode 150 so that the liquid metal 122 returns to the liquid metal tank 120 .

After resetting, the first voltage is applied to the first electrodes 140 , and the third voltage is applied to the third electrodes 160 . FIG. 4 is a schematic diagram of the multi-frequency filter of FIG. 2 operating in a second frequency band. Referring to FIG. 4 , the liquid metal 122 in the liquid metal tanks 120 moves toward the third electrodes 160 . Therefore, the extension length of the liquid metal 122 in these rows is an integer multiple of 1/4 wavelength of the second frequency band, so as to form a filter operating in the second frequency band.

For example, the extension length of the liquid metal 122 in the uppermost row is, for example, twice the wavelength of 1/4 times the wavelength of the second frequency band, and the extension length of the liquid metal 122 in the second row is, for example, 1/4 times the wavelength of the second frequency band. Twice the wavelength, the extension length of the liquid metal 122 in the third row is, for example, twice the wavelength of 1/4 times the wavelength of the second frequency band, and the extension length of the liquid metal 122 in the fourth row is, for example, 1/4 times the second frequency band. The extension length of the liquid metal 122 in the fifth row is, for example, twice the wavelength of 1/4 times the wavelength of the second frequency band. Of course, the multiple of the extension length of the liquid metal 122 is not limited to this.

It is worth mentioning that although the lengths of these channels 112 , 112a , 112b , 112c , and 112d are not all equal in FIG. 2 , in one embodiment, the lengths of these channels may also be equal. The 1/4 wavelength of the minimum frequency required is more than twice the wavelength to meet the conditions that the microstrip line required for all frequency bands can be made, and it is more convenient to manufacture.

To sum up, the liquid metal grooves of the multi-frequency filter of the present invention are respectively connected to the channels of the casing, and the first electrodes respectively extend into the liquid metal grooves to contact the liquid metal in the liquid metal grooves. The second electrodes and the third electrodes are respectively disposed in the channels. Through the above-mentioned design, when the first voltage is applied to the first electrodes, and the second voltage is applied to the second electrodes, the liquid metal in the liquid metal tank moves to the second electrodes, and the operation in the second electrode is formed. One-band filter. When a first voltage is applied to the first electrodes and a third voltage is applied to the third electrodes, the liquid metal in the liquid metal tanks moves to the third electrodes to form a filter operating in the second frequency band . Therefore, the multi-frequency filter of the present invention can adjust the operating frequency band as required, so as to achieve the performance of multi-frequency filtering.

D1: first direction D2: Second direction X, 2X, 3X, 4X: Distance 100: Multi-Frequency Filter 110: Shell 112, 112a, 112b, 112c, 112d: channels 114: First End 116: Second End 118: Electrolyte 120: Liquid metal tank 122: Liquid Metal 130: circuit board 140: First electrode 150: Second electrode 160: The third electrode

FIG. 1 is a partial cross-sectional schematic diagram of a device using liquid metal as a filter. FIG. 2 is a schematic top view of a multi-frequency filter according to an embodiment of the present invention. FIG. 3 is a schematic diagram of the multi-frequency filter of FIG. 2 operating in a first frequency band. FIG. 4 is a schematic diagram of the multi-frequency filter of FIG. 2 operating in a second frequency band.

D1: first direction

D2: Second direction

X, 2X, 3X, 4X: Distance

100: Multi-Frequency Filter

112, 112a, 112b, 112c, 112d: channels

114: First End

116: Second End

120: Liquid metal tank

140: First electrode

150: Second electrode

160: Third electrode

Claims (11)

A multi-frequency filter comprising: a housing including a plurality of channels; a plurality of liquid metal tanks, respectively connected to 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 disposed in the plurality of channels; and a plurality of third electrodes, respectively disposed 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 flows to the plurality of second electrodes move, forming a filter that operates on the 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 flows to the plurality of third electrodes move to form a filter operating in the second frequency band. The multi-frequency filter of claim 1, wherein the number of the plurality of second electrodes is the same as the number of the plurality of channels, and each of the plurality of second electrodes is associated with the corresponding first The distance between an electrode is an integer multiple of 1/4 wavelength of the first frequency band. The multi-frequency filter according to claim 1, wherein the number of the plurality of third electrodes is greater than the number of the plurality of channels, and in the first part of the plurality of channels, each channel is provided with a single One of the third electrodes, and the distance between the third electrode and the corresponding first electrode is an integer multiple of 1/4 wavelength of the second frequency band. The multi-frequency filter of claim 3, wherein in each of the channels, the distance between the second electrode and the closest third electrode is the same as that in the first portion of the plurality of channels. The integer multiple of the minimum distance between the second electrode and the third electrode. The multi-frequency filter of claim 4, wherein the plurality of channels extend along a first direction and are arranged along a second direction, and in at least a portion of the plurality of channels, the second electrode is connected to the The distance between the adjacent third electrodes increases along the second direction. The multi-frequency filter according to claim 3, wherein in the second part of the plurality of channels, two third electrodes are arranged in each of the channels, and the distance between the two third electrodes is It is an integer multiple of 1/4 wavelength of the second frequency band. The multi-frequency filter of claim 6, wherein in each of the second portions of the plurality of channels, the first electrode is located between the two third electrodes and proximate one of them the third electrode. The multi-frequency filter of claim 7, wherein in each of the second portions of the plurality of channels, the distance between the first electrode and the adjacent third electrode is An integer multiple of the minimum distance between the second electrode and the third electrode in the first portion of the plurality of channels. The multi-frequency filter of claim 8, wherein the plurality of channels extend in a first direction and are arranged in a second direction, and in the second portion of the plurality of channels, the first The distance between the electrode and the approached third electrode increases along the second direction. 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, one of the two channels has a difference to the plane where the other is located. The projection partially overlaps the other. The multi-frequency filter of claim 1, wherein each of the plurality of channels includes a first end and a second end opposed to each other, and in each of the channels, the first electrode is located close to the the first end, and the second electrode is located at the second end.

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