A reconfigurable filter based on liquid metal

Abstract

The present invention discloses a reconfigurable filter based on liquid metal. The filter comprises a top metal layer, a dielectric substrate, and a bottom metal layer stacked in this order from top to bottom. The dielectric substrate is provided with metallized vias arranged in a rectangular frame. The dielectric substrate within the rectangular frame is provided with a row of non-metallized vias. The dielectric substrate within the rectangular frame is divided into two rectangular sub-substrates. Each of the rectangular sub-substrates has a row of non-metallized vias on a diagonal line from the center to each vertex. The rows of non-metallized vias on the diagonals of the rectangular sub-substrates are symmetrical about the center. Some of the non-metallized vias are filled with liquid metal. Microstrip lines are connected to both rectangular sub-substrates. The present invention fills some of the non-metallized vias with liquid metal, with the injected liquid metal acting as a metal column. By filling different non-metallized vias, switching between low-frequency bandpass, high-frequency bandpass, and dual-bandpass states is achieved, providing a new method for addressing spectrum constraints.

Description

Technical Field

[0001] The invention relates to a reconfigurable filter based on liquid metal, belonging to the field of filters. Background Art

[0002] To ensure continuous and flexible communication, wireless communication systems often feature multiple frequency bands, switching between them using high-speed RF switches to meet communication requirements in varying signal quality, communication speed, and other scenarios. However, to ensure stable performance across frequency bands, filters, crucial for wireless systems, often require engineers to employ different filter designs for each RF link. This not only increases the size of wireless communication systems but also their cost. Therefore, a filter capable of switching between low-bandpass, high-bandpass, and dual-bandpass modes is urgently needed. Summary of the Invention

[0003] The present invention provides a liquid metal-based reconfigurable filter, which solves the problems disclosed in the background technology.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A reconfigurable filter based on liquid metal includes a top metal layer, a dielectric substrate, and a bottom metal layer stacked in this order from top to bottom. The dielectric substrate is provided with metallized vias arranged in a rectangular frame. The dielectric substrate within the rectangular frame is provided with a row of non-metallized vias. The dielectric substrate within the rectangular frame is divided into two rectangular sub-dielectric substrates. A row of non-metallized vias is provided on the diagonals from the center to each vertex of the rectangular sub-dielectric substrate. The rows of non-metallized vias on the diagonals of the rectangular sub-dielectric substrates are symmetrical about the center. Some of the non-metallized vias are filled with liquid metal. Both rectangular sub-dielectric substrates are connected to a microstrip line.

[0006] The top of the top metal layer is also covered with a top glass sheet, and the bottom of the bottom metal layer is also covered with a bottom glass sheet.

[0007] A rectangular resonant cavity is formed by a rectangular sub-dielectric substrate, non-metallized vias and metallized vias on the sides of the rectangular sub-dielectric substrate, non-metallized vias within the rectangular sub-dielectric substrate, a top metal layer above the rectangular sub-dielectric substrate, and a bottom metal layer below the rectangular sub-dielectric substrate. A gap is left on the non-metallized via array that divides the rectangular frame, and the gap serves as a coupling window between the two rectangular resonant cavities.

[0008] If the filter is in a low-frequency bandpass state, in the non-metallized via hole columns dividing the rectangular frame, except for the first non-metallized via hole on both sides of the gap, the remaining non-metallized via holes are all filled with liquid metal.

[0009] If the filter is in a high-frequency bandpass state, except for the first non-metallized via hole on both sides of the gap, the remaining non-metallized via holes are filled with liquid metal.

[0010] If the filter is in a dual-passband state, the first non-metallized via holes on both sides of the gap are filled with liquid metal.

[0011] Two non-metallized via holes are provided on the diagonal lines from the center to each vertex of the rectangular sub-dielectric substrate.

[0012] There are no metalized vias at the microstrip line connections.

[0013] The beneficial effects achieved by the present invention are as follows: the present invention adopts a new tuning method, filling liquid metal in some non-metallized vias. The injected liquid metal is equivalent to a metal column. By filling different non-metallized vias, the switching of low-frequency bandpass, high-frequency bandpass and dual-band passband states is realized, providing a new method for solving spectrum tension. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic diagram of the present invention;

[0015] Figure 2 It is a schematic diagram of the analysis of the present invention;

[0016] Figure 3 A top view of the present invention;

[0017] Figure 4 Schematic diagram of the non-metallized via filling state in the low-frequency bandpass state of the present invention;

[0018] Figure 5 Schematic diagram of the non-metallized via filling state in the high-frequency bandpass state of the present invention;

[0019] Figure 6 Schematic diagram of the non-metallized via filling state in the dual-passband state of the present invention;

[0020] Figure 7 It is the simulation curve diagram of the filter in the low-frequency bandpass state;

[0021] Figure 8 It is a simulation curve diagram of the filter in the high-frequency bandpass state;

[0022] Figure 9 This is the simulation curve of the filter in the dual-passband state. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0024] like Figures 1 to 3 As shown, a reconfigurable filter based on liquid metal includes a top acrylic glass plate 1, a top metal layer 2, a dielectric substrate 3, a bottom metal layer 4 and a bottom acrylic glass plate 5 stacked in this order from top to bottom.

[0025] The dielectric substrate 3 is a double-sided copper-clad dielectric substrate made of Rogers 4003 dielectric board with a dielectric constant of 3.55 and a thickness of 0.508 mm. The dielectric substrate 3 is provided with metallized vias 6 and non-metallized vias 7. To facilitate filling the non-metallized vias 7 with liquid metal, all non-metallized vias 7 extend from the top acrylic glass plate 1 to the bottom acrylic glass plate 5.

[0026] The structure of the metallized via 6 and the non-metallized via 7 is as follows: Figure 3 :

[0027] The metallized vias 6 are evenly distributed along the edge of the dielectric substrate to form a rectangular frame. The length of the rectangular frame is 2b, the width is a, the diameter of the metallized vias 6 in the rectangular frame is d0, and the spacing between adjacent metallized vias 6 is P0;

[0028] A row of vertical non-metallized vias 7 is formed on the dielectric substrate 3 within the rectangular frame, dividing the dielectric substrate 3 within the rectangular frame into two equal rectangular sub-dielectric substrates. A metallized via 6 is formed between the end of the row of non-metallized vias 7 and the rectangular frame. The spacing between the metallized via 6 and the outermost non-metallized via 7 is P3.

[0029] A row of non-metallic vias 7 is provided on the diagonal line from the center of the rectangular sub-dielectric substrate to each vertex. Specifically, the rows of non-metallic vias 7 are spaced apart by a distance K2. The rows of non-metallic vias 7 on the diagonal line of the rectangular sub-dielectric substrate are symmetrical about the center (the center of the rectangular sub-dielectric substrate). The angle between the diagonal line and the vertical axis of symmetry is θ. The distance from the center of the rectangular sub-dielectric substrate to the rows of non-metallic vias 7 is K1.

[0030] A rectangular SIW resonant cavity is formed by the rectangular sub-substrate, the non-metallized vias 7 and metallized vias 6 on the sides of the rectangular sub-substrate, the non-metallized vias 7 within the rectangular sub-substrate, the top metal layer 2 above the rectangular sub-substrate, and the bottom metal layer 4 below the rectangular sub-substrate. There are two rectangular SIW resonant cavities, and a gap is left in the column of non-metallized vias 7 that divides the rectangular frame, serving as a coupling window. The width of this gap is g0.

[0031] In the columns of non-metallized vias 7 that divide the rectangular frame, the spacing between the first non-metallized via 7 and its adjacent non-metallized vias 7 on both sides of the gap is P1, and the spacing between the remaining adjacent non-metallized vias 7 is P2.

[0032] The two rectangular sub-substrates are connected to the microstrip line. There is no metalized via 6 at the connection of the microstrip line, and a transition groove extending into the resonant cavity is opened at the connection. The width of the transition groove is M, and the width of the microstrip line is W. ms The two microstrip lines are both corner structure microstrip lines, L-shaped, the vertical sides of the two microstrip lines are connected to the rectangular sub-dielectric substrate, the lateral sides of the two microstrip lines are facing oppositely, and the distance between the lateral sides and the dielectric substrate 3 is L.

[0033] By filling some of the non-metallized vias 7 with liquid metal, the perturbation of the resonant cavity size and the control of the coupling between resonators are achieved by using the liquid metal, and the corresponding non-metallized vias are filled according to the filter response state.

[0034] The three states that the filter can switch to are: low-frequency bandpass, high-frequency bandpass and dual-band, among which,

[0035] 1) In the low-frequency bandpass state, at TE 102 Mode and TE 202 The electric field of the mode is weak, thus suppressing the TE 102 Mode and TE 202 Mode; two resonant cavities in TE 201 The electric field strength of the mode is weakest. Similarly, TE 201 The mode will also be suppressed.

[0036] Therefore, in this state, the filling state of the non-metallized via hole 7 is as follows: Figure 4 As shown, in the column of non-metallized vias 7 that divide the rectangular frame, except for the first non-metallized via 7 on both sides of the gap, the remaining non-metallized vias 7 are filled with liquid metal to achieve the best coupling state. This part of the filled non-metallized vias 7 is 8 in the figure.

[0037] Due to TE 102 TE 201 TE 202 All modes are suppressed, and the filter in this state can achieve wide stopband performance.

[0038] 2) In the high-frequency bandpass state, except for the first non-metallized via 7 on both sides of the gap, the remaining non-metallized vias 7 are filled with liquid metal, that is, Figure 5 When liquid metal is injected into both 8 and 9, 9 disturbs the field distribution of the resonant cavity mode and 8 changes the coupling strength, so that their resonant frequencies will also change.

[0039] Due to the disturbance of the metal pillars formed by the liquid metal, TE 101 TE 102 TE 201The mode frequencies are all increased. In order to ensure that the center frequency in the high-frequency bandpass state is consistent with the center frequency of the second passband in the dual-passband state, it is necessary to disturb the TE 101 The field distribution of the mode increases the frequency to the original TE 201 The frequency of the mode.

[0040] 3) In the dual-passband state, the feeding position remains unchanged, TE 102 Mode and TE 202 In this state, the first non-metallized vias 7 on both sides of the gap are filled with liquid metal, that is, Figure 6 10 in the 10, so the coupling window between the two resonant cavities has three parts. Compared with the low-frequency bandpass state, TE 201 Modes are coupled where their electric field strength is strong, so TE 201 mode is not suppressed, so TE 101 Mode and TE 201 The modes form the first and second passbands of the filter respectively.

[0041] To verify the filter effect, the above filter was constructed using the parameters in Table 1, and the liquid metal used was the indium gallium tin alloy shown in Table 2.

[0042] Table 1 Filter size values

[0043]

[0044]

[0045] Table 2 Parameters of InGaSn alloy

[0046]

[0047] Get the S-parameter simulation waveforms of the filter in different states. Figures 7-9 The horizontal axis is frequency (unit: GHz), the vertical axis is S parameter (unit: dB), the solid line S21 and the dotted line S11 respectively represent the relationship between the electromagnetic wave reflection coefficient and frequency and the relationship between the electromagnetic wave transmission coefficient and frequency.

[0048] like Figure 7 As shown, in the low-frequency passband state, the -3dB operating bandwidth of the filter of the present invention is 5.57GHz to 5.82GHz, the center frequency is 5.72GHz, the relative bandwidth is 4.4%, and the insertion loss is 1.74dB.

[0049] like Figure 8 As shown, in the high-frequency passband state, the -3dB operating bandwidth of the filter of the present invention is 9.13GHz to 9.44GHz, the center frequency is 9.28GHz, the relative bandwidth is 3.3%, and the insertion loss is 2.35dB.

[0050] like Figure 9 As shown, in the dual-passband state, the -3dB operating bandwidth of the first passband of the filter of the present invention is 5.59GHz~5.82GHz, and the center frequency is 5.7GHz; the -3dB operating bandwidth of the second passband is 9.06GHz~9.36GHz, and the center frequency is 9.21GHz.

[0051] The filter structure of the present invention is compared with some existing filter structures, as shown in Table 3.

[0052] Table 3 Comparison table

[0053]

[0054] Among them, the literature [1] B.Lee, S.Nam, T.Lee, C.Ahn and J.Lee.Single-Filter StructureWith Tunable Operating Frequency in Noncontiguous Bands[J]. IEEE Transactionson Components, Packaging and Manufacturing Technology, 2017, 7(1):98-105;

[0055] Literature[2]V.Sekar,M.Armendariz and K.Entesari.A1.2-1.6GHz SubstrateIntegrated Waveguide RF MEMS Tunable Filter[J].IEEE Transactions on MicrowaveTheory and Techniques,2011,59(4):866-876;

[0056] Literature [3] B.You, S.Lu, L.Chen and QJGu.AHalf-Mode Substrate-IntegratedFilter With Tunable Center Frequency and Reconfigurable Bandwidth[J]. IEEEMicrowave and Wireless Components Letters, 2016, 26(3):189-191;

[0057] Literature [4] M.Armendariz, V.Sekar and K.Entesari. Tunable SIW BandpassFilters with PIN Diodes[C]. IEEE European Microwave Conference, Paris, 2010, pp.830-833;

[0058] Literature[5]M.Koochakzadeh and A.Abbaspour-Tamijani.Switchable BandpassFilter for 0.3-0.6GHz[C].IEEE / MTTS International Microwave Symposium,2007,pp.557-560.

[0059] As can be seen from the above table, the liquid metal injected into the filter of the present invention is equivalent to a metal column, and no active devices are added to the structure. Compared with the electrically adjustable method with active devices, the insertion loss is smaller, and a dual-passband effect can be achieved without frequency offset.

[0060] The filter of the present invention adopts a new tuning method, filling liquid metal in some non-metallized vias. The injected liquid metal is equivalent to a metal column. By filling different non-metallized vias, switching between low-frequency bandpass, high-frequency bandpass and dual-band passband states is achieved, providing a new method for solving spectrum tension. In addition, the present invention adopts an SIW structure, which is simple in structure and easy to process.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A reconfigurable filter based on liquid metal, comprising a top metal layer, a dielectric substrate, and a bottom metal layer stacked in descending order, characterized in that: The dielectric substrate is provided with metallized vias arranged in a rectangular frame, the dielectric substrate within the rectangular frame is provided with a row of non-metallized vias, and the dielectric substrate within the rectangular frame is divided into two rectangular sub-dielectric substrates. A row of non-metallized vias is provided on the diagonal lines from the center to each vertex of the rectangular sub-dielectric substrate. The rows of non-metallized vias on the diagonals of the rectangular sub-dielectric substrates are symmetrical along the center. Some of the non-metallized vias are filled with liquid metal. The two rectangular sub-dielectric substrates are both connected to microstrip lines. There are no metallized vias at the connection of the microstrip lines, and transition grooves extending into the interior of the rectangular frame are provided on both sides of the microstrip lines.

2. The liquid metal-based reconfigurable filter according to claim 1, characterized in that: The top of the top metal layer is also covered with a top glass sheet, and the bottom of the bottom metal layer is also covered with a bottom glass sheet.

3. The liquid metal-based reconfigurable filter according to claim 1, characterized in that: The rectangular sub-dielectric substrate, the non-metallized via holes and the metallized via holes on the side of the rectangular sub-dielectric substrate, the non-metallized via holes in the rectangular sub-dielectric substrate, the top metal layer above the rectangular sub-dielectric substrate, and the bottom metal layer below the rectangular sub-dielectric substrate constitute a rectangular resonant cavity; A gap is left on the non-metallized via hole array that divides the rectangular frame, and the gap serves as a coupling window between the two rectangular resonant cavities.

4. The liquid metal-based reconfigurable filter according to claim 3, characterized in that: If the filter is in a low-frequency bandpass state, in the non-metallized via hole columns dividing the rectangular frame, except for the first non-metallized via hole on both sides of the gap, the remaining non-metallized via holes are all filled with liquid metal.

5. The liquid metal-based reconfigurable filter according to claim 3, characterized in that: If the filter is in a high-frequency bandpass state, except for the first non-metallized via hole on both sides of the gap, the remaining non-metallized via holes are filled with liquid metal.

6. The liquid metal-based reconfigurable filter according to claim 3, characterized in that: If the filter is in a dual-passband state, the first non-metallized via holes on both sides of the gap are filled with liquid metal.

7. The liquid metal-based reconfigurable filter according to claim 1, characterized in that: Two non-metallized via holes are provided on the diagonal lines from the center to each vertex of the rectangular sub-dielectric substrate.

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