Electrically tunable filter and communication system

Abstract

An electrically tunable filter (10) comprises a first dielectric substrate (11), a signal transmission line (12), a resonant structure (13) and a first grounding structure (14). The resonant structure (13) comprises a split-ring resonator (131) and a variable capacitor (132), the variable capacitor (132) is connected in series to the body of the split-ring resonator (131), the split-ring resonator (131) is located on one side of the signal transmission line (12) in the length direction, and a gap is formed between the split-ring resonator (131) and the signal transmission line (12). In the embodiments of the present disclosure, the resonant frequency of the split-ring resonator (131) can be adjusted by adjusting the capacitance value of the variable capacitor (132), i.e., the stop-band resonant frequency of the electrically tunable filter (10) can be adjusted, so that the electrically tunable filter (10) can filter a plurality of frequency bands, thereby simplifying a filter circuit for multi-band filtering, and improving the filter efficiency. Therefore, miniaturization, integration and low energy consumption of the filter circuit are realized. (Figure 1)

Description

Electrically tunable filters and communication systems Technical Field

[0001] This disclosure relates to the field of filtering technology, and more specifically, to an electrically tunable filter and a communication system. Background Technology

[0002] Filters effectively improve communication performance and ensure communication quality by filtering and separating signals. For multi-band wireless systems, filter banks composed of multiple filter banks with different center frequencies are typically used for frequency selection. However, the use of filter banks not only increases the structural complexity of transceiver circuits but also introduces significant losses. Therefore, filter banks do not conform to the current mainstream trend of miniaturization, integration, and low power consumption in filtering circuits.

[0003] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art.

[0004] Summary of the Invention

[0005] The purpose of this disclosure is to provide an electrically tunable filter and a communication system.

[0006] According to one aspect of this disclosure, an electrically tunable filter is provided, comprising: a first dielectric substrate, and a signal transmission line, a resonant structure, and a first grounding structure located on at least one side of the first dielectric substrate;

[0007] The resonant structure includes an open resonant ring and a variable capacitor. The variable capacitor is connected in series with the body of the open resonant ring and is used to apply a bias voltage. The open resonant ring is located on one side of the length direction of the signal transmission line and there is a gap between it and the signal transmission line.

[0008] According to any of the electrically tunable filters described in this disclosure, the signal transmission line includes an artificial surface plasmon, a matched segment, and a microstrip line;

[0009] The artificial surface plasmon includes a main transmission line and multiple comb lines. The multiple comb lines are connected to the main transmission line and distributed on at least one side of the main transmission line. Both ends of the main transmission line are connected to the matching segment and the microstrip line. The matching segment is located between the main transmission line and the microstrip line. The open-loop resonator is located on one side of the length direction of the main transmission line.

[0010] According to any of the electrically tunable filters described in this disclosure, the size of the open resonant ring is larger than the period size of the comb line distribution along the length of the main transmission line.

[0011] According to any of the electrically tunable filters described in this disclosure, the plurality of comb lines are located on a first side of the main transmission line, and the resonant structure is located on a second side of the main transmission line.

[0012] According to any of the electrically tunable filters described in this disclosure, the electrically tunable filter includes a plurality of the resonant structures, which are spaced apart along the length direction of the main transmission line.

[0013] According to any of the electrically tunable filters described in this disclosure, the plurality of comb lines includes a plurality of first comb lines and a plurality of second comb lines;

[0014] The plurality of first comb lines are located on the first side of the main transmission line and form a first empty area in the length direction of the main transmission line; the plurality of second comb lines are located on the second side of the main transmission line and form a second empty area in the length direction of the main transmission line.

[0015] The electrically tunable filter includes a first resonant structure and a second resonant structure. The orthographic projection of the first resonant structure onto the first dielectric substrate is located in the first vacant region, and the orthographic projection of the second resonant structure onto the first dielectric substrate is located in the second vacant region.

[0016] According to any of the electrically adjustable filters described in this disclosure, the comb wire includes a main body and a protrusion;

[0017] The main body has a strip-shaped structure, and the first end of the main body is connected to the main transmission line. The protrusion is fixedly connected to the second end of the main body and protrudes from both sides of the main body in the width direction.

[0018] According to any of the electrically tunable filters described in this disclosure, the protrusion is rectangular, and the long side of the protrusion is fixedly connected to the second end of the main body.

[0019] According to any of the electrically tunable filters described in this disclosure, the protrusion is circular, and the contour wall of the protrusion is fixedly connected to the second end of the main body.

[0020] According to any of the electrically tunable filters described in this disclosure, the protrusion is U-shaped, and the second end of the main body is located in the U-shaped groove of the protrusion and is fixedly connected to the center position of the bottom of the groove of the protrusion.

[0021] According to any of the electrically tunable filters described in this disclosure, the protrusions have a symmetrical structure, and the alignment lines of the protrusions coincide with the center line of the main body that is parallel to the length direction.

[0022] According to any of the electrically tunable filters described in this disclosure, the spacing between the open resonant ring and the signal transmission line is less than or equal to 0.5 mm.

[0023] According to any of the electrically tunable filters described in this disclosure, the open-loop resonant ring is a rectangular ring having an opening.

[0024] According to any of the electrically tunable filters described in this disclosure, the open-ended resonant ring has a resonant side facing the open end, the resonant side being located between the open end and the signal transmission line, and the length direction of the resonant side being parallel to the length direction of the signal transmission line.

[0025] According to any of the electrically tunable filters described in this disclosure, the resonant structure includes a plurality of variable capacitors, which are connected in series in series with the body of the open resonant ring.

[0026] According to any of the electrically tunable filters described in this disclosure, the two matching segments are symmetrically arranged along the perpendicular bisector of the main transmission line.

[0027] According to any of the electrically tunable filters described in this disclosure, the matching section includes a connecting line and a plurality of matching lines;

[0028] The connecting lines are respectively connected to the microstrip line and the main transmission line. A plurality of matching lines are connected to the connecting lines and are distributed on at least one side of the connecting lines. The length of each of the plurality of matching lines decreases in the direction away from the comb line.

[0029] According to any of the electrically tunable filters described in this disclosure, the signal transmission line is located on a first side of the first dielectric substrate, and the first grounding structure is located on a second side of the first dielectric substrate.

[0030] According to any of the electrically tunable filters described in this disclosure, the electrically tunable filter further includes a second dielectric substrate and a second grounding structure;

[0031] The second dielectric substrate is located on the side of the signal transmission line away from the first dielectric substrate, and the second grounding structure is located on the side of the second dielectric substrate away from the first dielectric substrate.

[0032] According to any of the electrically tunable filters described in this disclosure, the resonant structure is located on a first side of the first dielectric substrate.

[0033] According to any of the electrically tunable filters described in this disclosure, the signal transmission line and the first grounding structure are located on a first side of the first dielectric substrate;

[0034] The electrically tunable filter includes two pairs of the first grounding structures, each pair of the first grounding structures comprising two first grounding structures distributed on both sides of a microstrip line.

[0035] According to any of the electrically tunable filters described in this disclosure, the first grounding structure has a corner facing the main transmission line, and the corner is provided with a chamfer.

[0036] According to any of the electrically tunable filters described in this disclosure, the first grounding structure and the matching segment have an overlapping area in the width direction of the main transmission line.

[0037] According to any of the electrically tunable filters described in this disclosure, the resonant structure is located on a first side of the first dielectric substrate.

[0038] According to any of the electrically tunable filters described in this disclosure, the first dielectric substrate is a flexible dielectric substrate.

[0039] According to one aspect of this disclosure, a communication system is provided, including the electrically tunable filter described in the preceding aspect.

[0040] The embodiments disclosed herein include at least the following technical effects:

[0041] In this embodiment, on the one hand, by adjusting the capacitance value of the variable capacitor connected in series with the split-ring resonator, the resonant frequency of the split-ring resonator can be adjusted, thereby making the stopband resonant frequency of the electrically tunable filter adjustable. Thus, when an electromagnetic signal is transmitted along a signal transmission line, if filtering of multiple frequency bands is required, the bias voltage applied to the variable capacitor can be adjusted, enabling the electrically tunable filter to filter multiple frequency bands. This simplifies the multi-band filtering circuit and facilitates miniaturization, integration, and low power consumption of the filtering circuit. On the other hand, for signal transmission lines including artificial surface plasmons composed of a main transmission line and a comb line, the transmission efficiency of the electromagnetic signal can be effectively improved, thereby ensuring the filtering and transmission characteristics of the electrically tunable filter. Furthermore, for the artificial surface plasmon formed by the main transmission line and the comb line, in combination with the case where the first dielectric substrate is a flexible dielectric substrate, after adjusting the shape of the first dielectric substrate as needed, the artificial surface plasmon base source has a good binding effect on the transmitted electromagnetic signal. Even if the first dielectric substrate is bent into a curved surface or other shapes, the transmission effect of the electromagnetic signal on the signal transmission line will still be guaranteed.

[0042] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0043] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0044] Figure 1 is a top view of an electrically tunable filter provided in an embodiment of this disclosure.

[0045] Figure 2 is a schematic cross-sectional view of the electrically tunable filter shown in Figure 1 along the signal transmission line.

[0046] Figure 3 is a schematic diagram of the combination structure of a signal transmission line and a resonant structure provided in the embodiments of this disclosure.

[0047] Figure 4 is a schematic diagram of a resonant structure provided in an embodiment of this disclosure.

[0048] Figure 5 is a schematic diagram of another resonant structure provided in the embodiments of this disclosure.

[0049] Figure 6 is a graph of the insertion loss parameters of an electrically tunable filter provided in an embodiment of this disclosure.

[0050] Figure 7 shows the transmission coefficient curve and return loss curve of an electrically tunable filter provided in this embodiment of the present disclosure.

[0051] Figure 8 is a top view of a signal transmission line provided in an embodiment of this disclosure.

[0052] Figure 9 is a schematic diagram of another signal transmission line and resonant structure provided in the embodiments of this disclosure.

[0053] Figure 10 is a top view of another signal transmission line provided in this embodiment.

[0054] Figure 11 is a top view of another signal transmission line provided in this embodiment.

[0055] Figure 12 is a top view of another signal transmission line provided in this embodiment.

[0056] Figure 13 is a schematic cross-sectional view of another electrically tunable filter provided in this embodiment of the present disclosure along the signal transmission line.

[0057] Figure 14 is a top view of another electrically tunable filter provided in this embodiment.

[0058] Figure 15 is a schematic cross-sectional view of the electrically tunable filter shown in Figure 14 along the signal transmission line.

[0059] Figure 16 is a top view of another electrically tunable filter provided in this embodiment.

[0060] Figure 17 is a schematic cross-sectional view of the electrically tunable filter shown in Figure 16 along the signal transmission line.

[0061] Figure 18 is a top view of another electrically tunable filter provided in this embodiment.

[0062] Reference numerals: 10. Electrically tunable filter; 11. First dielectric substrate; 12. Signal transmission line; 13. Resonant structure; 14. First grounding structure; 15. Second dielectric substrate; 16. Second grounding structure; 121. Artificial surface plasmon; 122. Main transmission line; 123. Comb line; 124. Microstrip line; 125. Matching segment; 1231. First comb line; 1232. Second comb line; 1251. Connecting line; 1252. Matching line; 131. Open resonant ring; 132. Variable capacitor; 133. Opening; 134. Notch; 135. Voltage loading terminal; 136. First resonant structure; 137. Second resonant structure; 141. Corner. Detailed Implementation

[0063] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, they are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore detailed descriptions of them will be omitted. Furthermore, the drawings are merely illustrative of this disclosure and are not necessarily drawn to scale.

[0064] Although relative terms such as "up" and "down" are used in this specification to describe the relative relationship of one component of an icon to another, these terms are used only for convenience, such as according to the orientation of the examples shown in the accompanying drawings. It is understood that if the device of the icon is flipped upside down, the component described as "up" will become the component described as "down." When a structure is "up" of another structure, it may mean that the structure is integrally formed on the other structure, or that the structure is "directly" mounted on the other structure, or that the structure is "indirectly" mounted on the other structure through another structure.

[0065] The terms “a,” “one,” “the,” “the,” and “at least one” are used to indicate the presence of one or more elements / components / etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components / etc. in addition to the listed elements / components / etc.; the terms “first,” “second,” and “third,” etc., are used only as markers and are not a limitation on the number of objects.

[0066] Figure 1 illustrates a top view of an electrically tunable filter 10 provided in an embodiment of the present disclosure, and Figure 2 illustrates a cross-sectional view of an electrically tunable filter 10 provided in an embodiment of the present disclosure. As shown in Figures 1 and 2, the electrically tunable filter 10 includes: a first dielectric substrate 11, and a signal transmission line 12, a resonant structure 13, and a first grounding structure 14 located on at least one side of the first dielectric substrate 11; the resonant structure 13 includes an open-ended resonant ring 131 and a variable capacitor 132, the variable capacitor 132 being connected in series with the body of the open-ended resonant ring 131 and used to apply a bias voltage, the open-ended resonant ring 131 being located on one side of the length direction of the signal transmission line 12, and having a gap between it and the signal transmission line 12.

[0067] In this embodiment, the variable capacitor 132 is used to apply a bias voltage to adjust its capacitance value. Since the variable capacitor 132 is connected in series with the split-ring resonator 131, adjusting its capacitance value allows for adjustment of the resonant frequency of the split-ring resonator 131, thereby enabling the adjustable stopband resonant frequency of the electrically tunable filter 10. When an electromagnetic signal is transmitted along the signal transmission line 12, if filtering of multiple frequency bands is required, the bias voltage applied to the variable capacitor 132 can be adjusted, allowing the electrically tunable filter 10 to filter multiple frequency bands. This simplifies the multi-band filtering circuit and facilitates miniaturization, integration, and low power consumption of the filtering circuit.

[0068] The first dielectric substrate 11 can be a flexible dielectric substrate, such as a polytetrafluoroethylene glass fiber laminate, a phenolic paper laminate, or a phenolic glass cloth laminate, or a rigid dielectric substrate, such as quartz or glass, which have low microwave loss. When the first dielectric substrate 11 is flexible, its shape can be adjusted as needed, such as a planar structure or a curved structure, to achieve conformal characteristics of the electrically tunable filter 10 while transmitting electromagnetic signals (i.e., the shape can be arbitrarily adjusted as needed). Furthermore, the first dielectric substrate 11 can be a single-layer board structure or a multi-layer composite board structure. For example, in a multi-layer composite board structure, the first dielectric substrate 11 includes a first PI (polyimide) layer, a first protective layer, a second PI (polyimide) layer, and a second protective layer stacked sequentially from bottom to top. The two protective layers protect the PI layer and prevent damage to the PI layer from subsequent processes.

[0069] In this embodiment of the disclosure, the resonant structure 13 includes an open resonant ring 131, which is a metal ring with an opening 133 to form an open loop. Thus, when the electromagnetic signal is transmitted through the signal transmission line 12, the electromagnetic signal of a specific frequency can form a continuous oscillation in the open resonant ring 131. At the same time, it will have a coupling effect with the opening 133 of the open resonant ring 131, so that the electromagnetic signal of the specific frequency will be greatly attenuated, that is, the transmission of the electromagnetic signal of the specific frequency along the signal transmission line 12 will be hindered.

[0070] The open-ended resonant ring 131 can be made of low-resistance, low-loss metals such as copper, gold, or silver, and can be formed on the surface of the first dielectric substrate 11 by methods such as magnetron sputtering, thermal evaporation, or electroplating. Furthermore, the electrically tunable filter 10 can include one resonant structure 13 or multiple resonant structures 13, distributed on the same side of the length direction of the signal transmission line 12, or distributed on both sides of the length direction of the signal transmission line 12. For example, as shown in FIG3, the electrically tunable filter 10 includes two resonant structures 13, and the two resonant structures 13 are distributed on the same side of the length direction of the signal transmission line 12.

[0071] In this configuration, the open-loop resonant ring 131 and the signal transmission line 12 are adjacent but not in contact, in order to achieve a resonance effect between the signal transmission line 12 and the open-loop resonant ring 131. The open-loop resonant ring 131 and the signal transmission line 12 can be arranged on the same layer or on different layers.

[0072] When the open-ended resonant ring 131 and the signal transmission line 12 are on the same layer, the open-ended resonant ring 131 and the signal transmission line 12 can be located on the same side surface of the first dielectric substrate 11, and the open-ended resonant ring 131 and the signal transmission line 12 are spaced apart. When the open-ended resonant ring 131 and the signal transmission line 12 are on different layers, the open-ended resonant ring 131 and the signal transmission line 12 can be located on different side surfaces of the first dielectric substrate 11. For example, the signal transmission line 12 is located on the first side surface of the first dielectric substrate 11, and the open-ended resonant ring 131 is located on the second side surface of the first dielectric substrate 11. In this case, the orthographic projections of the open-ended resonant ring 131 and the signal transmission line 12 on the first dielectric substrate 11 may not overlap, or they may overlap, as long as resonance between the open-ended resonant ring 131 and the signal transmission line 12 can be guaranteed.

[0073] Optionally, the spacing between the split-ring resonator 131 and the signal transmission line 12 is greater than 0 and less than or equal to 0.5 mm to ensure the resonance effect between the split-ring resonator 131 and the signal transmission line 12. For example, the spacing between the split-ring resonator 131 and the signal transmission line 12 is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, etc. Of course, in certain structural designs of the split-ring resonator 131 and the signal transmission line 12, the spacing between the split-ring resonator 131 and the signal transmission line 12 can also be greater than 0.5 mm, as long as the resonance effect between the split-ring resonator 131 and the signal transmission line 12 can be guaranteed. For example, the spacing between the split-ring resonator 131 and the signal transmission line 12 is 0.6 mm.

[0074] In some embodiments, as shown in FIG4, the open-ring resonator 131 is a rectangular ring with an opening 133. Of course, the open-ring resonator 131 can also be other ring structures with an opening 133, such as the circular ring with an opening 133, the elliptical ring with an opening 133, or the triangular ring with an opening 133, etc., as shown in FIG5.

[0075] Specifically, for the rectangular structure of the open-ended resonant ring 131, the opening 133 on the open-ended resonant ring 131 can be located on one of the long resonant sides of the open-ended resonant ring 131 and in a central position. Specifically, the rectangular open-ended resonant ring 131 is a structure symmetrical along the perpendicular bisector of the long resonant side. Alternatively, for the rectangular structure of the open-ended resonant ring 131, one resonant side of the open-ended resonant ring 131 can be parallel to the length direction of the signal transmission line 12. This increases the sensing area between the open-ended resonant ring 131 and the signal transmission line 12, thereby improving the resonance effect between the open-ended resonant ring 131 and the signal transmission line 12, and thus improving the filtering effect of the electrically tunable filter 10 on electromagnetic signals of a specific frequency. In addition, for the open-ring resonant ring 131 in the shape of a rectangular ring, the resonant side with the opening 133 on the open-ring resonant ring 131 may be located on the side closer to the signal transmission line 12, or the resonant side with the opening 133 on the open-ring resonant ring 131 may be located on the side farther away from the signal transmission line 12, or the resonant side with the opening 133 on the open-ring resonant ring 131 may be located on one side along the length direction of the signal transmission line 12.

[0076] For example, the split-ring resonator 131 has a resonant side directly opposite the opening 133. This resonant side of the split-ring resonator 131 is located between the opening 133 and the signal transmission line 12, and the length direction of the resonant side is parallel to the length direction of the signal transmission line 12. Furthermore, considering the spacing between the split-ring resonator 131 and the signal transmission line 12 described above, the spacing between the resonant side of the split-ring resonator 131 closest to the signal transmission line 12 and the signal transmission line 12 can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, or 0.5 mm, etc.

[0077] In this embodiment of the disclosure, the series connection of the variable capacitor 132 on the open resonant ring 131 can be as shown in Figure 4 or Figure 5. The variable capacitor 132 has two voltage loading terminals 135, and the open resonant ring 131 has an open notch 134. The two voltage loading terminals 135 of the variable capacitor 132 are respectively connected to the two ends of the notch 134 on the open resonant ring 131.

[0078] In this way, the variable capacitor 132 is connected in series on the open resonant ring 131, and a bias voltage is applied to the variable capacitor 132 based on the two voltage loading terminals 135 of the variable capacitor 132.

[0079] The variable capacitor 132 can be a variable diode, etc. For example, the variable capacitor 132 has two solder leads (i.e., two voltage loading terminals 135), which are soldered to the two ends of the notch 134 on the open resonant ring 131, respectively.

[0080] The variable capacitor 132 connected in series on the open resonant ring 131 can be one or more.

[0081] When a variable capacitor 132 is connected in series with the open resonant ring 131, taking the open resonant ring 131 as a rectangular ring as an example, the variable capacitor 132 can be connected in series on one long resonant side of the open resonant ring 131, or on one short resonant side of the open resonant ring 131, or at one corner of the open resonant ring 131.

[0082] When multiple variable capacitors 132 are connected in series on the open-ended resonant ring 131, the multiple variable capacitors 132 can be connected in series sequentially on the open-ended resonant ring 131, that is, the open-ended resonant ring 131 has multiple spaced gaps 134, and the multiple gaps 134 correspond one-to-one with the multiple variable capacitors 132. The two voltage loading terminals 135 of each variable capacitor 132 are respectively connected to the two ends of the corresponding gap 134 on the open-ended resonant ring 131. Of course, multiple variable capacitors 132 can also be connected in parallel and then in series on the open-ended resonant ring 131, that is, the open-ended resonant ring 131 has one gap 134, and the two voltage loading terminals 135 of each variable capacitor 132 are respectively connected to the two ends of the gap 134 on the open-ended resonant ring 131.

[0083] In the case where multiple variable capacitors 132 are connected in series with the open resonant ring 131, the multiple variable capacitors 132 can be evenly distributed along the circumference of the open resonant ring 131. In the case where multiple variable capacitors 132 are connected in parallel and then connected in series with the open resonant ring 131, the multiple variable capacitors 132 can be connected in parallel and then connected in series with one long resonant side of the open resonant ring 131, or they can be connected in series with one short resonant side of the open resonant ring 131, or they can be connected in series with the corner of the open resonant ring 131.

[0084] For example, the resonant structure 13 includes a variable capacitor 132, and by adjusting the bias voltage applied to the variable capacitor 132, the capacitance value of the variable capacitor 132 can be changed between 0.6pF and 2.2pF, thereby achieving an adjustment of the stopband frequency between 5GHz and 6.5GHz after the open-circuit resonant ring 131 resonates.

[0085] For example, Figure 6 shows the insertion loss parameter curves of the electrically tunable filter 10 when the capacitance value of the variable capacitor 132 is 0.6pF, 0.9pF, 1.6pF, and 2.2pF, respectively. Combining the insertion loss parameter curves corresponding to each capacitance value, it can be seen that when the capacitance value of the variable capacitor 132 is 0.6pF, the stopband frequency of the electrically tunable filter 10 is 6.2GHz. At this time, the electrically tunable filter 10 can filter electromagnetic waves with a frequency of about 6.2GHz. When the capacitance value of the variable capacitor 132 is 0.9pF, the stopband frequency of the electrically tunable filter 10 is close to 5. At 6GHz, the electronically tunable filter 10 can filter electromagnetic waves with a frequency of approximately 5.6GHz. When the capacitance value of the variable capacitor 132 is 1.6pF, the stopband frequency of the electronically tunable filter 10 is close to 5.25GHz, and the electronically tunable filter 10 can filter electromagnetic waves with a frequency of approximately 5.25GHz. When the capacitance value of the variable capacitor 132 is 2.2pF, the stopband frequency of the electronically tunable filter 10 is 5.05GHz, and the electronically tunable filter 10 can filter electromagnetic waves with a frequency of approximately 5.05GHz.

[0086] Continuing with the example above, taking the capacitance value of variable capacitor 132 adjusted to 2.2pF as an example, the transmission coefficient curve and return loss curve of electrically tunable filter 10 when electromagnetic signals of different frequencies are transmitted along signal transmission line 12 are shown in Figure 7. When the absolute value of the transmission coefficient is greater than 5, it is considered that no effective transmission has occurred (i.e., it has been filtered by electrically tunable filter 10). Based on the transmission coefficient curve of electrically tunable filter 10, it can be seen that when the capacitance value of variable capacitor 132 is 2.2pF, the stopband frequency of electrically tunable filter 10 is approximately 4.9GHz to 5.2GHz, and the lower cutoff frequency of electrically tunable filter 10 is 8.2GHz.

[0087] In this embodiment of the disclosure, the signal transmission line 12 can be made of low-resistance, low-loss metals such as copper, gold, and silver, and can be formed on the surface of the first dielectric substrate 11 by means of magnetron sputtering, thermal evaporation, electroplating, etc.

[0088] In some embodiments, as shown in FIG8, the signal transmission line 12 includes an artificial surface plasmon 121 and a microstrip line 124. The artificial surface plasmon 121 includes a main transmission line 122 and a plurality of comb lines 123. The plurality of comb lines 123 are connected to the main transmission line 122 and are distributed on at least one side of the main transmission line 122. Both ends of the main transmission line 122 are connected to the microstrip line 124.

[0089] Among them, based on the transmission characteristics of the artificial surface plasmon 121 itself (strong localization, low insertion loss, etc.), when the electromagnetic signal is transmitted along the signal transmission line 12, the electromagnetic wave excited by the electromagnetic signal will be confined to the surface of the main transmission line 122 and the comb line 123, and will not easily diverge to the outside, so as to realize the confinement of the electromagnetic signal within the main transmission line 122 and the comb line 123. Moreover, the higher the frequency of the electromagnetic wave, the better the confinement effect of the main transmission line 122 and the comb line 123 on the electromagnetic signal.

[0090] Thus, for the signal transmission line 12, which includes the artificial surface plasmon 121 consisting of the main transmission line 122 and the comb line 123, the transmission efficiency of the electromagnetic signal can be effectively improved, thereby ensuring the filtering and transmission characteristics of the electrically tunable filter 10. Furthermore, regarding the artificial surface plasmon 121 formed by the main transmission line 122 and the comb line 123, combined with the aforementioned case where the first dielectric substrate 11 is a flexible dielectric substrate, after adjusting the shape of the first dielectric substrate 11 as needed, because the artificial surface plasmon source has a good binding effect on the transmitted electromagnetic signal, even if the first dielectric substrate 11 is bent into a curved surface or other shapes, the transmission effect of the electromagnetic signal on the signal transmission line 12 will still be guaranteed.

[0091] In this configuration, multiple comb lines 123 are uniformly distributed along the length of the main transmission line 122. For the artificial surface plasmon 121, which includes the main transmission line 122 and the multiple comb lines 123, the width of the main transmission line 122 may be greater than the width of the comb lines 123, and both the width of the main transmission line 122 and the width of the comb lines 123 may be less than the width of the microstrip line 124. Optionally, the width W of the main transmission line 122 may be greater than or equal to 0.2 mm and less than or equal to 0.8 mm, and the width of the comb lines 123 may be greater than or equal to 0.1 mm and less than or equal to 0.5 mm. For example, the width of the main transmission line 122 is 0.5 mm, and the width of the comb lines 123 is 0.3 mm. Furthermore, the lengths of the multiple comb lines 123 may be identical or not identical. Optionally, the length of the comb lines 123 may be greater than or equal to 3.0 mm and less than or equal to 4.5 mm. For example, the length of each of the multiple comb lines 123 is 3.8 mm. Furthermore, the multiple comb lines 123 can be evenly spaced or unequally spaced along the length of the main transmission line 122. Optionally, the spacing between two adjacent comb lines 123 is greater than or equal to 0.5 mm and less than or equal to 1.5 mm. For example, the multiple comb lines 123 are evenly spaced along the length of the main transmission line 122, and the spacing between two adjacent comb lines 123 is 0.8 mm.

[0092] The length direction of the main transmission line 122 is the same as the length direction of the signal transmission line 12. Furthermore, considering the relative positional relationship between the split-ring resonator 131 and the signal transmission line 12 described above, the split-ring resonator 131 can be located on one side of the length direction of the main transmission line 122. To ensure the resonance effect between the split-ring resonator 131 and the main transmission line 122, the distance between the split-ring resonator 131 and the main transmission line 122 can be greater than 0 and less than or equal to 0.5 mm. For example, the spacing between the split-ring resonator 131 and the main transmission line 122 can be 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, etc. In the length direction of the main transmission line 122, the centerline of the resonant structure 13 can coincide with the symmetry line of the artificial surface plasmon 121 to ensure the resonance effect between the resonant structure 13 and the artificial surface plasmon 121.

[0093] Furthermore, in conjunction with the resonant structure 13 described above, for the case where the electrically tunable filter 10 includes only one resonant structure 13, the resonant structure 13 can be located in the middle of the main transmission line 122 along its length. Further, for the open-ended resonant ring 131 to be a rectangular ring structure, and for the open-ended resonant ring 131 to be symmetrical along the perpendicular bisector of its long resonant side, the symmetry line of the open-ended resonant ring 131 can coincide with the perpendicular bisector of the main transmission line 122. Even further, the opening 133 and the variable capacitor 132 on the open-ended resonant ring 131 can be located in the middle of the two long resonant sides of the open-ended resonant ring 131, i.e., the resonant structure 13 is symmetrical along the perpendicular bisector of its long resonant side, and the symmetry line of the resonant structure 13 can coincide with the perpendicular bisector of the main transmission line 122.

[0094] In some embodiments, the size of the open-loop resonator 131 is larger than the period size of the distribution of the comb lines 123 along the length of the main transmission line 122, that is, the size of the open-loop resonator 131 along the length of the main transmission line 122 is greater than the sum of the width of one comb line 123 and the spacing between two adjacent comb lines 123.

[0095] In this way, a larger-sized open-loop resonant ring 131 can be set, thereby meeting the low-frequency filtering requirements of the electrically tunable filter 10.

[0096] Furthermore, considering the rectangular ring structure of the open-ended resonant ring 131 described above, the length of a resonant side of the open-ended resonant ring 131 parallel to the length direction of the main transmission line 122 is greater than the distribution period of the comb line 123. For example, in the length direction of the main transmission line 122, the size of the open-ended resonant ring 131 is 2 times, 4 times, 6 times, 8 times, etc., the non-distribution period of the comb line 123.

[0097] In some embodiments, as shown in Figure 1 or Figure 3, multiple comb lines 123 are located on the first side of the main transmission line 122, and the resonant structure 13 is located on the second side of the main transmission line 122. This facilitates bringing the resonant structure 13 closer to the main transmission line 122, avoiding interference from the comb lines 123. Simultaneously, the size design of the resonant structure 13 is not affected by the comb lines 123, allowing for the implementation of large-size open-circuit resonant rings 131, small-size open-circuit resonant rings 131, or both large-size and small-size open-circuit resonant rings 131 simultaneously. This facilitates the design of high-frequency, mid-frequency, and low-frequency stopband frequencies, ensuring the filtering range of the electrically tunable filter 10.

[0098] The electrically tunable filter 10 may include one or more resonant structures 13, and the multiple resonant structures 13 are spaced apart along the length direction of the main transmission line 122. For example, as shown in FIG3, the electrically tunable filter 10 includes two resonant structures 13, both of which are located on the side of the main transmission line 122 away from the comb line 123, and are spaced apart along the length direction of the main transmission line 122.

[0099] Among them, the multiple resonant structures 13 located on one side of the main transmission line 122 can be evenly distributed along the length direction of the main transmission line 122, or they can be distributed according to design requirements, as long as the filtering effect of the electrically tunable filter 10 can be guaranteed. This disclosure does not limit this.

[0100] The open-loop resonant rings 131 included in the multiple resonant structures 13 can have the same or different structural dimensions. When the open-loop resonant rings 131 included in the multiple resonant structures 13 have the same or approximately the same structural dimensions, after applying the same bias voltage to the variable capacitors 132 of the multiple resonant structures 13, the multiple resonant structures 13 can have the same resonant frequency. In this case, for electromagnetic signals of a specific frequency, multiple filtering can be performed under the action of the multiple resonant structures 13 to improve the filtering effect of the electrically tunable filter 10. When the open-loop resonant rings 131 included in the multiple resonant structures 13 have different structural dimensions and the size difference is large, after applying the bias voltage to the variable capacitors 132 of the multiple resonant structures 13, the multiple resonant structures 13 have different resonant frequencies. In this case, when the electromagnetic signal is transmitted along the signal transmission line 12, a multi-frequency filtering effect can be formed under the action of the multiple resonant structures 13 to improve the filtering effect of the electrically tunable filter 10.

[0101] It should be noted that multiple resonant structures 13 can be arranged in the same layer. For example, as shown in FIG3, multiple resonant structures 13 (two resonant structures 13) are located on the same side surface of the first dielectric substrate 11. Of course, multiple resonant structures 13 can also be located on different structural layers. For example, multiple resonant structures 13 are located on different side surfaces of the first dielectric substrate 11.

[0102] In other embodiments, as shown in FIG9, the plurality of comb lines 123 include a plurality of first comb lines 1231 and a plurality of second comb lines 1232; the plurality of first comb lines 1231 are located on a first side of the main transmission line 122 and a first vacancy region is formed in the length direction of the main transmission line 122, and the plurality of second comb lines 1232 are located on a second side of the main transmission line 122 and a second vacancy region is formed in the length direction of the main transmission line 122; the electrically tunable filter 10 includes a first resonant structure 136 and a second resonant structure 137, the orthographic projection of the first resonant structure 136 on the first dielectric substrate 11 is located in the first vacancy region, and the orthographic projection of the second resonant structure 137 on the first dielectric substrate 11 is located in the second vacancy region.

[0103] Thus, by setting the first resonant structure 136 and the second resonant structure 137, multiple filtering of the electrically tunable filter 10 or multi-frequency filtering of the electrically tunable filter 10 can be realized. That is, when the structural dimensions of the open resonant ring 131 included in the first resonant structure 136 and the second resonant structure 137 are the same or approximately the same, multiple filtering of the electrically tunable filter 10 can be realized; when the structural dimensions of the open resonant ring 131 included in the first resonant structure 136 and the second resonant structure 137 are different and the size difference is large, multi-frequency filtering of the electrically tunable filter 10 can be realized.

[0104] The first vacant area of ​​the first resonant structure 136 can be located on one side of the multiple first comb lines 1231 along the length of the main transmission line 122, or between any two of the multiple first comb lines 1231; similarly, the second vacant area of ​​the second resonant structure 137 can be located on one side of the multiple second comb lines 1232 along the length of the main transmission line 122, or between any two of the multiple second comb lines 1232.

[0105] Thus, the first resonant structure 136 in the first vacant region can resonate with the main transmission line 122 and the first comb line 1231 simultaneously, and the second resonant structure 137 in the second vacant region can resonate with the main transmission line 122 and the second comb line 1232 simultaneously, thereby improving the resonance effect of the first resonant structure 136 and the second resonant structure 137, and further improving the filtering effect of the electrically tunable filter 10. Furthermore, the first resonant structure 136 located in the first vacant region, the second resonant structure 137 located in the second vacant region, the first comb line 1231, and the second comb line 1232 will not interfere with the distance between the first resonant structure 136, the second resonant structure 137, and the main transmission line 122, thereby facilitating the resonance between the first resonant structure 136, the second resonant structure 137, and the main transmission line 122. At the same time, the size design of the first resonant structure 136 and the second resonant structure 137 will not be interfered with by the first comb line 1231 and the second comb line 1232, thereby facilitating the design of high-frequency, intermediate-frequency, and low-frequency stopband frequencies and ensuring the filtering range of the electrically tunable filter 10.

[0106] The first resonant structure 136 and the second resonant structure 137 can be disposed on the same layer. For example, the first resonant structure 136 and the second resonant structure 137 are located on the same side surface of the first dielectric substrate 11. Of course, the first resonant structure 136 and the second resonant structure 137 can also be located on different structural layers. For example, the first resonant structure 136 and the second resonant structure 137 are located on different side surfaces of the first dielectric substrate 11.

[0107] In some embodiments, as shown in Figure 8 or Figure 9, the comb wire 123 has a strip-shaped structure. This simplifies the structural shape of the comb wire 123, thereby making it easier to reduce the manufacturing precision of the comb wire 123 and improve the manufacturing yield of the comb wire 123.

[0108] In other embodiments, as shown in Figures 10, 11 or 12, the comb wire 123 includes a main body and a protrusion. The main body has a strip-shaped structure, and the first end of the main body is connected to the main transmission line 122. The protrusion is fixedly connected to the second end of the main body and protrudes from both sides of the main body in the width direction.

[0109] In this way, by setting the protrusion, the length of the main body can be effectively shortened while ensuring a strong confinement effect on the electromagnetic signal. This facilitates the reduction of the size of the artificial surface plasmon 121 in the width direction of the main transmission line 122, thereby enabling the miniaturization and integration of the electrically tunable filter 10. In addition, setting the protrusion at the second end of the main body can also effectively reduce the upper cutoff frequency of the signal transmission line 12 and increase the bandwidth of the signal transmission line 12 at the same frequency.

[0110] As for the protrusions included in the comb wire 123, they can be as shown in Figure 10, where the protrusions are rectangular and the long side of the protrusions is fixedly connected to the second end of the main body; or as shown in Figure 11, where the protrusions are circular and the contour wall of the protrusions is fixedly connected to the second end of the main body; or as shown in Figure 12, where the protrusions are U-shaped, the second end of the main body is located in the U-shaped groove of the protrusions and is fixedly connected to the center position of the bottom of the groove of the protrusions.

[0111] Optionally, the protrusions included in the comb line 123 may have a symmetrical structure, and the alignment of the protrusions may coincide with the centerline of the main body that is parallel to the length direction. In this way, when electromagnetic signals are transmitted through the comb line 123, they can be evenly distributed in the area where the protrusions of the comb line 123 are located, so as to ensure the binding effect of the comb line 123 on the electromagnetic signals.

[0112] In some embodiments, as shown in FIG8, the signal transmission line 12 further includes a matching segment 125, both ends of the main transmission line 122 are connected to the matching segment 125, and the matching segment 125 is located between the main transmission line 122 and the microstrip line 124.

[0113] Thus, by connecting the microstrip line 124 and the main transmission line 122 through the matching segment 125, impedance matching between the microstrip line 124 and the artificial surface plasmon 121 (main transmission line 122 and comb line 123) is achieved, reducing the loss of electromagnetic signals when they are transmitted between the microstrip line 124 and the main transmission line 122, and ensuring the transmission effect of electromagnetic signals.

[0114] Optionally, the two matching segments 125 included in the signal transmission line 12 can be symmetrically arranged along the perpendicular bisector of the main transmission line 122. In this way, while ensuring impedance matching between the artificial surface plasmon 121 (main transmission line 122 and comb line 123) and the microstrip lines 124 at both ends, the same matching effect is achieved, thereby ensuring the transmission effect of electromagnetic signals along the signal transmission line 12.

[0115] Optionally, as shown in FIG8, the matching segment 125 includes a connecting line 1251 and a plurality of matching lines 1252; the connecting line 1251 is connected to the microstrip line 124 and the main transmission line 122 respectively, and the plurality of matching lines 1252 are connected to the connecting line 1251 and distributed on at least one side of the connecting line 1251, and the length of each matching line 1252 decreases in the direction away from the comb line 123.

[0116] Thus, by decreasing the length of multiple matching lines 1252 on the matching segment 125 in the direction of the original comb line 123, the transition from microstrip line 124 to comb line 123 is achieved, so as to effectively realize impedance matching between microstrip line 124 and artificial surface plasmon 121 (main transmission line 122 and comb line 123).

[0117] In this embodiment, the length of each matching line 1252 can be less than the length of the comb line 123. This is to effectively shorten the size of the connecting line 1251 while ensuring impedance matching between the microstrip line 124 and the artificial surface plasmon resonance 121, thereby reducing the overall length of the signal transmission line 12 and facilitating the miniaturization of the electrically tunable filter 10. The width of the matching lines 1252 and the width of the connecting lines 1251 included in the matching segment 125 can be determined by referring to the width of the comb line 123 and the main transmission line 122, respectively. This embodiment does not limit the specific width of these dimensions.

[0118] For example, as shown in Figure 8, the multiple comb lines 123 included in the signal transmission line 12 are all located on the side of the main transmission line 122 away from the resonant structure 13. In this case, for the matching segments 125 connected to both ends of the main transmission line 122, the matching lines 1252 on both matching segments 125 can be located on the side of the connecting line 1251 away from the resonant structure 13. Alternatively, as shown in Figure 9, the signal transmission line 12 includes multiple comb lines 123, including multiple first comb lines 1231 and multiple second comb lines 1232. The electrically tunable filter 10 includes a first resonant structure 136 and a second resonant structure 137. The first comb lines 1231 and the first electrically tunable structure are both located on the first side of the main transmission line 122, and the second comb lines 1232 and the second resonant structure 137 are both located on the second side of the main transmission line 122. In this case, if the multiple first comb lines 1231 are generally close to the first end of the main transmission line 122, and the multiple second comb lines 1232 are generally close to the second end of the main transmission line 122, then for the matching segment 125 connected to the first end of the main transmission line 122, the matching lines 1252 on the matching segment 125 are all located on the first side of the main transmission line 122, and for the matching segment 125 connected to the second end of the main transmission line 122, the matching lines 1252 on the matching segment 125 are all located on the second side of the main transmission line 122.

[0119] In this embodiment of the disclosure, when transmitting electromagnetic signals based on the signal transmission line 12, the electromagnetic signals can be transmitted in the form of a microstrip line 124, a stripline, or a coplanar waveguide.

[0120] In some embodiments, as shown in Figures 1 and 2, the signal transmission line 12 is located on the first side of the first dielectric substrate 11, and the first grounding structure 14 is located on the second side of the first dielectric substrate 11. This allows electromagnetic signals to be transmitted via microstrip lines 124, and also simplifies the film structure of the electrically tunable filter 10, enabling the filter to be made ultrathin.

[0121] The resonant structure 13 included in the electrically tunable filter 10 can be located on the second side of the first dielectric substrate 11, or, as shown in Figure 1, on the first side of the first dielectric substrate 11, meaning that both the signal transmission line 12 and the resonant structure 13 are located on the same side of the first dielectric substrate 11. When the resonant structure 13 and the signal transmission line 12 are located on the same side of the first dielectric substrate 11, it is easier to control the distance between the resonant structure 13 and the signal transmission line 12, ensuring the resonance effect between them. Furthermore, the first grounding structure 14 can be a single-layer metal structure to avoid interference between the signal transmission line 12 and the resonant structure 13, simplifying the manufacturing process of the first grounding structure 14, while also improving the shielding of electromagnetic signals and reducing signal crosstalk during transmission.

[0122] For example, as shown in Figures 1 and 2, a signal transmission line 12 and a resonant structure 13 are formed on the first side surface of the first dielectric substrate 11, and a first grounding structure 14 is formed on the second side surface of the first dielectric substrate 11.

[0123] The signal transmission line 12 includes an artificial surface plasmon 121 with a main transmission line 122 and a comb line 123, matching segments 125 connected to both ends of the main transmission line 122, and microstrip lines 124 connected to the two matching segments 125 away from the main transmission line 122. The two matching segments 125 and the two microstrip lines 124 are symmetrical along the perpendicular bisector of the main transmission line 122. The resonant structure 13 includes an open resonant ring 131 in the shape of a rectangular ring and a variable capacitor 132 connected in series with the open resonant ring 131. The opening on the open resonant ring 131 is located in the middle of one long resonant side, and the variable capacitor 132 is connected in the middle of another long resonant side. The resonant structure 13 is symmetrical along the perpendicular bisector of the long resonant side, and the line of symmetry of the resonant structure 13 coincides with the perpendicular bisector of the main transmission line 122. The first grounding structure 14 is a metal structure formed on the front side of the second side surface of the first dielectric substrate 11.

[0124] Optionally, as shown in FIG13, the electrically tunable filter 10 further includes a second dielectric substrate 15 and a second grounding structure 16; the second dielectric substrate 15 is located on the side of the signal transmission line 12 away from the first dielectric substrate 11, and the second grounding structure 16 is located on the side of the second dielectric substrate 15 away from the first dielectric substrate 11.

[0125] Thus, the electromagnetic signal is transmitted in the form of a stripline by setting the second dielectric substrate 15 and the second grounding structure 16. At the same time, since the signal transmission line 12 is sandwiched between the first grounding structure 14 and the second grounding structure 16, the electromagnetic signal is well shielded, reducing electromagnetic radiation and external interference. In other words, signal crosstalk during transmission is avoided, and the transmission effect of the electromagnetic signal is improved.

[0126] The second grounding structure 16 can be a single-layer metal structure, combined with the single-layer first grounding structure 14, to improve the shielding effect on electromagnetic signals and avoid signal crosstalk during transmission. The specific structure of the second dielectric substrate 15 can be exactly the same as or different from the specific structure of the first dielectric substrate 11, and this disclosure does not limit this. For example, the specific structures of the first dielectric substrate 11 and the second dielectric substrate 15 are exactly the same, and both the first dielectric substrate 11 and the second dielectric substrate 15 are single-layer flexible dielectric substrates; for example, both the first dielectric substrate 11 and the second dielectric substrate 15 include a first PI (polyimide) layer, a first protective layer, a second PI (polyimide) layer, and a second protective layer stacked sequentially from bottom to top. Alternatively, the specific structures of the first dielectric substrate 11 and the second dielectric substrate 15 are not exactly the same, and the first dielectric substrate 11 is a multilayer rigid dielectric substrate, while the second dielectric substrate 15 is a single-layer flexible dielectric substrate; for example, the first dielectric substrate 11 is a glass substrate, and the second dielectric substrate 15 includes a first PI (polyimide) layer, a first protective layer, a second PI (polyimide) layer, and a second protective layer stacked sequentially from bottom to top.

[0127] For example, as shown in Figures 1 and 13, a signal transmission line 12 and a resonant structure 13 are formed on the first side surface of the first dielectric substrate 11, and a first grounding structure 14 is formed on the second side surface of the first dielectric substrate 11; a second grounding structure 16 is formed on the first side surface of the second dielectric substrate 15, the second side surface of the second dielectric substrate 15 faces the first side surface of the first dielectric substrate 11, and the two are bonded and fixed together.

[0128] The signal transmission line 12 includes an artificial surface plasmon 121 with a main transmission line 122 and a comb line 123, matching segments 125 connected to both ends of the main transmission line 122, and microstrip lines 124 connected to the two matching segments 125 away from the main transmission line 122. The two matching segments 125 and the two microstrip lines 124 are symmetrical along the perpendicular bisector of the main transmission line 122. The resonant structure 13 includes an open resonant ring 131 in the shape of a rectangular ring and a variable capacitor 132 connected in series with the open resonant ring 131. The opening 133 on the open resonant ring 131 is located in the middle of one long resonant side, and the variable capacitor 132 is connected in the middle of another long resonant side. The resonant structure 13 is symmetrical along the perpendicular bisector of the long resonant side, and the line of symmetry of the resonant structure 13 coincides with the perpendicular bisector of the main transmission line 122. The first grounding structure 14 is a metal structure formed on the front side of the second side surface of the first dielectric substrate 11.

[0129] In other embodiments, as shown in Figures 14 and 15, or Figures 16 and 17, the signal transmission line 12 and the first ground structure 14 are located on a first side of the first dielectric substrate 11; the electrically tunable filter 10 includes two pairs of first ground structures 14, each pair of first ground structures 14 including two first ground structures 14 distributed on both sides of one end of the signal transmission line 12.

[0130] In this way, electromagnetic signals can be transmitted in the form of coplanar waveguides based on the cooperation between the end of the signal transmission line 12 and the two first grounding structures 14, while also simplifying the film structure of the electrically tunable filter 10 and realizing the ultra-thin design of the electrically tunable filter 10.

[0131] The resonant structure 13 included in the electrically tunable filter 10 can be located on the second side of the first dielectric substrate 11, as shown in Figures 14 and 15; or it can be located on the first side of the first dielectric substrate 11, as shown in Figures 16 and 17, where the signal transmission line 12, the first grounding structure 14, and the resonant structure 13 are all located on the first side of the first dielectric substrate 11. When the resonant structure 13 is located on the first side of the first dielectric substrate 11, the film structure of the electrically tunable filter 10 can be further simplified, enabling the electrically tunable filter 10 to be ultra-thin.

[0132] In the case where the signal transmission line 12 includes an artificial surface plasmon resonance 121 (main transmission line 122 and comb line 123) and a microstrip line 124, a pair of first grounding structures 14 can be distributed on both sides of a microstrip line 124. Thus, based on the cooperation of a microstrip line 124 and two first grounding structures 14, electromagnetic signals are transmitted in the form of a coplanar waveguide.

[0133] For example, as shown in Figures 14 and 15, a signal transmission line 12 and a first grounding structure 14 are formed on the first side surface of the first dielectric substrate 11, and a resonant structure 13 is formed on the second side surface of the first dielectric substrate 11.

[0134] The signal transmission line 12 includes an artificial surface plasmon resonance 121 with a main transmission line 122 and a comb line 123, matching segments 125 connected to both ends of the main transmission line 122, and microstrip lines 124 connected to sections of the two matching segments 125 away from the main transmission line 122. Multiple comb lines 123 are located on the same side of the main transmission line 122, and the two matching segments 125 and two microstrip lines 124 are symmetrical along the perpendicular bisector of the main transmission line 122. The resonant structure 13 is located on the side of the main transmission line 122 away from the comb line 123 and includes an open resonant ring 131 in the shape of a rectangular loop. The variable capacitor 132 is connected in series with the open resonant ring 131, and the opening 133 of the open resonant ring 131 is located on a long resonant side away from the main transmission line 122 and in the middle position. The variable capacitor 132 is connected on a long resonant side of the open resonant ring 131 close to the main transmission line 122 and in the middle position. The resonant structure 13 is symmetrical along the perpendicular bisector of the long resonant side, and the line of symmetry of the resonant structure 13 coincides with the perpendicular bisector of the main transmission line 122. The electrically tunable filter 10 includes two pairs of first grounding structures 14, each pair of first grounding structures 14 being distributed on both sides of the length direction of the microstrip line 124.

[0135] For example, as shown in Figures 16 and 17, a signal transmission line 12, a resonant structure 13, and a first grounding structure 14 are formed on the first side surface of the first dielectric substrate 11.

[0136] The signal transmission line 12 includes an artificial surface plasmon resonance 121 with a main transmission line 122 and a comb line 123, matching segments 125 connected to both ends of the main transmission line 122, and microstrip lines 124 connected to sections of the two matching segments 125 away from the main transmission line 122. Multiple comb lines 123 are located on the same side of the main transmission line 122, and the two matching segments 125 and two microstrip lines 124 are symmetrical along the perpendicular bisector of the main transmission line 122. The resonant structure 13 is located on the side of the main transmission line 122 away from the comb line 123 and includes an open resonant ring 131 in the shape of a rectangular loop. The variable capacitor 132 is connected in series with the open resonant ring 131, and the opening 133 of the open resonant ring 131 is located on a long resonant side away from the main transmission line 122 and in the middle position. The variable capacitor 132 is connected on a long resonant side of the open resonant ring 131 close to the main transmission line 122 and in the middle position. The resonant structure 13 is symmetrical along the perpendicular bisector of the long resonant side, and the line of symmetry of the resonant structure 13 coincides with the perpendicular bisector of the main transmission line 122. The electrically tunable filter 10 includes two pairs of first grounding structures 14, each pair of first grounding structures 14 being distributed on both sides of the length direction of the microstrip line 124.

[0137] For example, as shown in FIG18, a signal transmission line 12, two resonant structures 13 and a first ground structure 14 are formed on the first side surface of the first dielectric substrate 11.

[0138] The signal transmission line 12 includes an artificial surface plasmon 121 with a main transmission line 122 and a comb line 123, matching segments 125 connected to both ends of the main transmission line 122, and microstrip lines 124 connected to sections of the two matching segments 125 away from the main transmission line 122. The multiple comb lines 123 are all located on the same side of the main transmission line 122, and the two matching segments 125 and two microstrip lines 124 are symmetrical along the perpendicular bisector of the main transmission line 122. Two resonant structures 13 are located on the side of the main transmission line 122 away from the comb line 123. Furthermore, along the length direction of the main transmission line 122, both resonant structures 13 include an open resonant ring 131 in the shape of a rectangular ring and a variable capacitor 132 connected in series on the open resonant ring 131. The opening 133 on the open resonant ring 131 is located on a long resonant side away from the main transmission line 122 and is in the middle position. The variable capacitor 132 is connected on a long resonant side of the open resonant ring 131 close to the main transmission line 122 and is in the middle position. The resonant structure 13 is symmetrical along the perpendicular bisector of the long resonant side, and the line of symmetry of the resonant structure 13 coincides with the perpendicular bisector of the main transmission line 122. The electrically tunable filter 10 includes two pairs of first grounding structures 14, each pair of first grounding structures 14 being distributed on both sides of the length direction of the microstrip line 124.

[0139] Optionally, as shown in Figure 14 or Figure 16, both first grounding structures 14 have a corner 141 facing the main transmission line 122, and the corner 141 is chamfered. Thus, a via structure can be formed by the chamfered structure on the pair of first grounding structures 14, assisting in impedance matching between the microstrip line 124 and the main transmission line 122. Furthermore, considering the aforementioned case where the signal transmission line 12 includes a matching section 125, the impedance matching between the microstrip line 124 and the main transmission line 122 can be effectively guaranteed under the combined effect of the matching section 125 and the via structure, thereby ensuring the transmission effect of electromagnetic signals along the signal transmission line 12.

[0140] Optionally, in conjunction with the aforementioned signal transmission line 12 including a matching segment 125, the first grounding structure 14 and the matching segment 125 have an overlapping area in the width direction of the main transmission line 122. Thus, by setting the first grounding structure 14 and the matching segment 125 to have an overlapping area in the width direction of the main transmission line 122, the matching effect between the microstrip line 124 and the main transmission line 122 is effectively guaranteed by the combination of the first grounding structure 14 and the matching segment 125, thereby ensuring the transmission effect of electromagnetic signals along the signal transmission line 12.

[0141] This disclosure also provides a communication system that includes the electrically tunable filter 10 described in the above embodiments.

[0142] In this embodiment of the disclosure, the electrically tunable filter 10 described above can be used to adjust the stopband frequency of the electrically tunable filter 10 based on the bias voltage applied to the variable capacitor 132, thereby simplifying the structure of the filter included in the communication system.

[0143] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

Claims

1. An electrically tunable filter, wherein, include: A first dielectric substrate, and a signal transmission line, a resonant structure, and a first grounding structure located on at least one side of the first dielectric substrate; The resonant structure includes an open resonant ring and a variable capacitor. The variable capacitor is connected in series with the body of the open resonant ring and is used to apply a bias voltage. The open resonant ring is located on one side of the length direction of the signal transmission line and there is a gap between it and the signal transmission line.

2. The electrically tunable filter as described in claim 1, wherein, The signal transmission line includes an artificial surface plasmon, a matched segment, and a microstrip line; The artificial surface plasmon includes a main transmission line and multiple comb lines. The multiple comb lines are connected to the main transmission line and distributed on at least one side of the main transmission line. Both ends of the main transmission line are connected to the matching segment and the microstrip line. The matching segment is located between the main transmission line and the microstrip line. The open-loop resonator is located on one side of the length direction of the main transmission line.

3. The electrically tunable filter as described in claim 2, characterized in that, Along the length of the main transmission line, the size of the open resonant ring is larger than the period size of the comb line distribution.

4. The electrically tunable filter as described in claim 2, wherein, The plurality of comb lines are located on the first side of the main transmission line, and the resonant structure is located on the second side of the main transmission line.

5. The electrically tunable filter as described in claim 4, wherein, The electrically tunable filter includes a plurality of resonant structures, which are spaced apart along the length of the main transmission line.

6. The electrically tunable filter as described in claim 2, wherein, The plurality of comb lines includes a plurality of first comb lines and a plurality of second comb lines; The plurality of first comb lines are located on the first side of the main transmission line and form a first empty area in the length direction of the main transmission line; the plurality of second comb lines are located on the second side of the main transmission line and form a second empty area in the length direction of the main transmission line. The electrically tunable filter includes a first resonant structure and a second resonant structure. The orthographic projection of the first resonant structure onto the first dielectric substrate is located in the first vacant region, and the orthographic projection of the second resonant structure onto the first dielectric substrate is located in the second vacant region.

7. The electrically tunable filter as described in claim 2, wherein, The comb line includes a main body and a protruding part; The main body has a strip-shaped structure, and the first end of the main body is connected to the main transmission line. The protrusion is fixedly connected to the second end of the main body, and the two protrusions are located in the width direction of the main body. Both sides protrude from the main body.

8. The electrically tunable filter as claimed in claim 7, wherein, The protrusion is rectangular, and the long side of the protrusion is fixedly connected to the second end of the main body.

9. The electrically tunable filter as claimed in claim 7, wherein, The protrusion is circular, and the contour wall of the protrusion is fixedly connected to the second end of the main body.

10. The electrically tunable filter as claimed in claim 7, wherein, The protrusion is U-shaped, and the second end of the main body is located in the U-shaped groove of the protrusion and is fixedly connected to the center position of the bottom of the groove of the protrusion.

11. The electrically tunable filter as described in any one of claims 7-10, wherein, The protrusions have a symmetrical structure, and the alignment of the protrusions coincides with the center line of the main body that is parallel to the length direction.

12. The electrically tunable filter as described in any one of claims 1-10, wherein, The spacing between the open resonant ring and the signal transmission line is less than or equal to 0.5 mm.

13. The electrically tunable filter as described in any one of claims 1-10, wherein, The open-loop resonant ring is a rectangular ring with an opening.

14. The electrically tunable filter as claimed in claim 13, wherein, The open resonant ring has a resonant side facing the opening, the resonant side is located between the opening and the signal transmission line, and the length direction of the resonant side is parallel to the length direction of the signal transmission line.

15. The electrically tunable filter as described in any one of claims 1-10, wherein, The resonant structure includes multiple variable capacitors, which are connected in series in the body of the open resonant ring.

16. The electrically tunable filter as described in any one of claims 2-10, wherein, The two matching segments are symmetrically arranged along the perpendicular bisector of the main transmission line.

17. The electrically tunable filter as claimed in claim 16, wherein, The matching segment includes a connecting line and multiple matching lines; The connecting lines are respectively connected to the microstrip line and the main transmission line. A plurality of matching lines are connected to the connecting lines and are distributed on at least one side of the connecting lines. The length of each of the plurality of matching lines decreases in the direction away from the comb line.

18. The electrically tunable filter as described in any one of claims 1-10, wherein, The signal transmission line is located on the first side of the first dielectric substrate, and the first grounding structure is located on the second side of the first dielectric substrate.

19. The electrically tunable filter as claimed in claim 17, wherein, The electrically tunable filter also includes a second dielectric substrate and a second grounding structure; The second dielectric substrate is located on the side of the signal transmission line away from the first dielectric substrate, and the second grounding structure is located on the side of the second dielectric substrate away from the first dielectric substrate.

20. The electrically tunable filter as claimed in claim 18, wherein, The resonant structure is located on the first side of the first dielectric substrate.

21. The electrically tunable filter as described in any one of claims 2-10, wherein, The signal transmission line and the first grounding structure are located on the first side of the first dielectric substrate; The electrically tunable filter includes two pairs of the first grounding structures, each pair of the first grounding structures comprising two first grounding structures distributed on both sides of a microstrip line.

22. The electrically tunable filter as claimed in claim 21, wherein, The first grounding structure has a corner facing the main transmission line, and the corner is chamfered.

23. The electrically tunable filter as claimed in claim 22, wherein, In the width direction of the main transmission line, the first grounding structure and the matching segment have an overlapping area.

24. The electrically tunable filter as claimed in claim 21, wherein, The resonant structure is located on the first side of the first dielectric substrate.

25. The electrically tunable filter as claimed in claim 1, wherein, The first dielectric substrate is a flexible dielectric substrate.

26. A communication system, wherein, Includes the electrically tunable filter as described in any one of claims 1-25.

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