Dual-frequency band-pass filter based on combined symmetric resonators
By combining symmetrical resonators and using a combination of mountain-shaped and U-shaped resonators, and adjusting the coupling gap and open-circuit stub size, the problems of large insertion loss and large area of dual-frequency filters were solved, realizing the design of miniaturized and low-loss dual-frequency filters.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- HUAQIAO UNIVERSITY
- Filing Date
- 2025-05-13
- Publication Date
- 2026-04-17
Smart Images
Figure CN224138305U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of radio frequency microwave communication technology, and more specifically to a dual-bandpass filter based on a combined symmetrical resonator. Background Technology
[0002] With the development of wireless communication technology, communication systems that cover two or more frequency bands have become an important research direction in the field of wireless communication. This demand has driven the development of multi-frequency microwave components, among which dual-frequency filters have received widespread attention as a key component.
[0003] Currently, the common structure for implementing dual-band filters is to combine two resonators operating at different frequencies through a coupling structure. This makes traditional dual-band filters capable of being designed independently and easily meet the requirements of both passbands for center frequency and bandwidth. However, this type of structure has the disadvantages of high insertion loss and large area.
[0004] In view of this, this application has conducted in-depth research on this basis, resulting in this case. Utility Model Content
[0005] The purpose of this invention is to provide a dual-bandpass filter based on a combined symmetrical resonator, which can achieve miniaturization and has low insertion loss in the passband.
[0006] To achieve the above objectives, the solution of this utility model is:
[0007] A dual-bandpass filter based on combined symmetrical resonators includes a grounded metal plate, a substrate disposed on the grounded metal plate, a microstrip line structure disposed on the substrate, and two transmission lines disposed on the substrate and arranged back-to-back. The microstrip line structure includes two sets of symmetrically arranged resonant combinations. Each set of resonant combinations includes resonators A and B arranged side-by-side. The two resonators A are arranged close to each other, and the two resonators B are arranged close to each other. Both resonators A are quarter-wavelength open-circuit stub-loaded resonators in a mountain-shaped configuration. The open-circuit stubs in resonator A are respectively located at the middle of their respective bottoms, and the two open-circuit stubs are arranged parallel to each other on both sides of the corresponding resonator A. Both resonators B are U-shaped half-wavelength resonators, and the openings of resonators A and B in each resonant combination face the same side. The two transmission lines are respectively located on both sides of the microstrip line structure, and the two transmission lines are arranged in parallel coupling with resonators A and B in the corresponding resonant combination. The first ends of the two transmission lines are respectively provided with input ports and output ports.
[0008] Metal through holes are respectively provided at the ends of the two resonators A on their adjacent sides, and each metal through hole passes through the substrate and the grounding metal plate in sequence.
[0009] The inner diameter of the metal through hole is 0.8 mm.
[0010] The coupling gap between the two resonators A is 1.24 mm, and the coupling gap between the two resonators A and their corresponding transmission lines is 0.1425 mm.
[0011] The coupling gap between the two resonators B is 0.245 mm, and the coupling gap between the two resonators B and the corresponding transmission line is 0.25 mm.
[0012] The two resonators A are used for resonance at a first passband center frequency of 2.4 GHz, and the two resonators B are used for resonance at a second passband center frequency of 5.25 GHz.
[0013] The first ends of the two transmission lines are respectively connected to feeder lines, and the two feeder lines are respectively arranged perpendicular to the corresponding transmission lines. One end of the two feeder lines is respectively connected to the input port and the output port.
[0014] The substrate is a dielectric substrate, and the substrate has a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness of 0.8 mm.
[0015] By adopting the above structure, this utility model has the following beneficial effects:
[0016] 1. This utility model employs two symmetrically arranged resonant combinations. Each resonator combination includes resonator A and resonator B. Resonator A is a quarter-wavelength resonator with an open-circuit stub, and resonator B is a half-wavelength resonator. In this way, different two resonators in one resonant combination resonate with two resonators in the other resonant combination to form different passbands, thus realizing the two passbands of the dual-frequency filter. By adjusting the gaps between the two resonators A and the two resonators B, the first and second passbands can each have a wide bandwidth and low insertion loss. Moreover, since the open-circuit stub is loaded in resonator A, the center frequency of the first passband in this utility model can be effectively adjusted, forming a compact multimode resonator, thus achieving miniaturization.
[0017] 2. This utility model employs a two-resonant combination setup. By adjusting the relative distance (i.e., coupling gap) between the two resonators A, the frequency characteristics of the first passband can be changed, i.e., the bandwidth and insertion loss of the first passband can be adjusted. Furthermore, by adjusting the dimensions (i.e., length and width) of the open-circuit stubs in resonator A, the center frequency of the first passband can be adjusted so that the first passband meets the frequency range requirements. This also reduces the size of the utility model, achieving a miniaturized design. Similarly, by adjusting the coupling gap between the two resonators B, the bandwidth and frequency characteristics of the second passband can be adjusted, and the insertion loss of the second passband can be optimized.
[0018] 3. In this utility model, both the center frequency of the first passband and the center frequency of the second passband are relatively wide. With the commonly used insertion loss suppression range of 3dB, the bandwidth of the first passband is 250MHz and the bandwidth of the second passband is 385MHz. It is suitable for different standards and multiple working modes and has a wide range of applications. Attached Figure Description
[0019] Figure 1 This is a schematic diagram of the assembly of the dual-frequency bandpass filter of this utility model.
[0020] Figure 2 This is a schematic diagram of the microstrip line structure and the arrangement of the two transmission lines in the dual-frequency bandpass filter of this utility model.
[0021] Figure 3 for Figure 2 Physical dimensions diagram.
[0022] Figure 4 This is a circuit connection block diagram of the dual-frequency bandpass filter of this utility model.
[0023] Figure 5 This is a schematic diagram showing the effect of the coupling gap S1 between the two resonators A in the dual-frequency bandpass filter of this utility model on the insertion loss S21.
[0024] Figure 6 This is a schematic diagram illustrating the effect of the coupling gap S1 between the two resonators A in the dual-frequency bandpass filter of this utility model on the return loss S11.
[0025] Figure 7 This is a schematic diagram illustrating the effect of the coupling gap S2 between the two resonators B in the dual-frequency bandpass filter of this utility model on the insertion loss S21.
[0026] Figure 8 This is a schematic diagram illustrating the effect of the coupling gap S2 between the two resonators B in the dual-frequency bandpass filter of this utility model on the return loss S11.
[0027] Figure 9This is a schematic diagram of the optimized simulation curves of return loss S11 and insertion loss S21 for the dual-frequency bandpass filter of this utility model.
[0028] In the picture:
[0029] 1-Substrate; 2-Microstrip line structure; 21-Resonator A; 211-Open stub; 22-Resonator B; 3-Transmission line; 31-Feeder line; 4-Ground metal plate; 5-Metal via; 61-Input port; 62-Output port. Detailed Implementation
[0030] To further explain the technical solution of this utility model, the following detailed description is provided through specific embodiments.
[0031] This invention provides a dual-bandpass filter based on a combined symmetrical resonator, such as... Figure 1 As shown - Figure 3 As shown, it includes a substrate 1, a microstrip line structure 2 disposed on the upper surface of the substrate 1, two transmission lines 3 disposed on the upper surface of the substrate 1, and a grounding metal plate 4 disposed on the lower surface of the substrate 1. The two transmission lines 3 are disposed on both sides of the microstrip line structure 2 and are arranged back to back. The two transmission lines 3 are respectively connected to the corresponding resonant combination through the following coupling feeding structure.
[0032] The substrate 1 mentioned above is a conventional dielectric substrate. In this embodiment, the relative permittivity of substrate 1 is 2.2, the loss tangent is 0.0009, and the thickness is 0.8mm. In this embodiment, the substrate 1 is RogersRT / duroid 5880, which is already available on the market.
[0033] The grounding metal plate 4 mentioned above is a commercially available metal plate used to achieve grounding; in addition, the grounding metal plate 4 can also be replaced with the following structure, in which a metal coating used as a grounding layer is provided on the lower surface of the substrate 1.
[0034] The aforementioned microstrip structure includes two symmetrically arranged resonant combinations. Each resonant combination includes resonators A21 and B22 arranged side by side. The two resonators A21 are arranged close to each other, and the two resonators B22 are arranged close to each other. For ease of description, the direction from resonator A21 to resonator B22 in the same resonant combination is taken as the left-to-right direction, and the horizontal direction perpendicular to the left and right is taken as the up-down direction. The two resonant combinations are symmetrically arranged along the center line, and the axis of symmetry of the two resonant combinations is consistent with the left-to-right direction. In other words, in this embodiment, one resonant combination is located above the other resonant combination, and the resonator A21 in the same resonant combination is located to the left or right of resonator B22. In this embodiment, the example of resonator A21 being located to the left of resonator B22 is used for illustration.
[0035] Furthermore, since the structures of the two sets of resonant combinations mentioned above are identical, we will take one set of resonant combinations as an example for explanation. Resonator A21 is a quarter-wavelength open-stub loaded resonator in a mountain-shaped configuration, that is, a quarter-wavelength resonator loaded with an open-stub 211 to form a quarter-wavelength open-stub loaded resonator. The open-stub 211 within resonator A21 is integrally connected to the middle position of the bottom of resonator A21. Here, the interior of resonator A21 refers to the side of resonator A21 that surrounds each other as the inner side. Resonator A21 includes two integrally connected opposite sides, a connecting side connecting the two opposite sides together, and an open-stub 211 located in the middle position of the connecting side. This open-stub 211 is arranged in the left-right direction. Here, the bottom of resonator A21 consists of the three aforementioned connecting sides. In this embodiment, the open-stub 211... The two resonators A21 are arranged parallel to each other on both sides. In this way, the two resonators A21 loaded with open-circuit stubs 21 are coupled to each other to form the first passband. That is, the two resonators A21 together constitute a resonator unit. The open-circuit stub loaded in the resonator A21 can effectively change the equivalent electrical length of the resonator A21, thereby flexibly adjusting the resonant frequency of the resonator A21. This effectively controls the center frequency and bandwidth of the first passband, increasing the flexibility of this invention and allowing for adjustments to meet different frequency band requirements at the factory. Moreover, since the high-order harmonic frequency distribution of the resonator A21 is suppressed to a certain extent after the open-circuit stub is loaded, it is beneficial to adjust the center frequency control of the first passband. Therefore, the size of the resonator A21 can be reduced, which is beneficial to the miniaturization and integration of this invention and can improve frequency selectivity.
[0036] The aforementioned resonator B22 is a U-shaped half-wavelength resonator, meaning that resonator B includes two opposite sides and a connecting side that connects the two sides together. The openings of resonators A21 and B22 both face the same side. In this embodiment, the example is taken where the openings of resonators A21 and B22 both face to the left. The two resonators B22 are arranged symmetrically vertically. In this way, the two resonators B22 are coupled to each other to form a second passband, that is, the two resonators B22 together constitute a resonator unit.
[0037] Furthermore, two metal through holes 5 are provided on the left end of the side of the two resonators A21 that are close to each other. The two metal through holes 5 have the same arrangement structure, so one of the metal through holes 5 is used as an example for explanation. The metal through hole 5 passes through the substrate 1 and the ground metal plate 4 from top to bottom to realize the electrical connection of the microstrip line structure and optimize the grounding path. Preferably, in this embodiment, the inner diameter of the metal through hole 5 is 0.8mm. In this embodiment, the metal through hole 5 is the metal through hole commonly used in existing resonators, so it will not be described in detail.
[0038] The two transmission lines 3 are respectively disposed on both sides of the microstrip line structure 2. In this embodiment, the two transmission lines 3 are disposed on the upper and lower sides of the microstrip line structure 2. The two transmission lines 3 are respectively arranged in parallel with the resonators A21 and B22 in the corresponding resonant combination. That is, the transmission line 3 on the upper side is arranged in parallel with the resonators A21 and B22 in the resonant combination on the upper side. The left ends of the two transmission lines 3 are respectively connected to feed lines 31. Preferably, the two feed lines 31 are arranged perpendicular to the corresponding transmission lines 3. The first end of the feed line 31 on the upper side is connected to the input port 61, and the first end of the feed line 31 on the lower side is connected to the output port 62. Transmission line 3, feed line 31, and input port 61 together form a coupled feeding structure. The lower transmission line 3, feed line 3, and output port 62 together form another coupled feeding structure. The two coupled feeding structures cooperate with the corresponding resonant combinations to perform signal coupling and energy transmission. In this way, the two feed lines 31 optimize the input / output matching performance and adjust the transmission efficiency of the filter by adjusting the coupling gap S4 between the corresponding transmission line 3 and the adjacent side of the resonator A, and by adjusting the coupling gap S5 between the corresponding transmission line 3 and the adjacent side of the resonator B. The coupling gaps S4 and S5 can be set according to actual needs.
[0039] like Figure 2 The as- Figure 8 As shown, in each of the above resonant combinations, resonators A21 and B22 are frequency-adjustable resonators. In other words, this invention can adjust the resonant frequency of the first passband by adjusting the length L4, width W1, and coupling gap S1 of resonator A21. The width W1 of resonator A21 is the same as the width of resonator B22. This invention adjusts the bandwidth and insertion loss of the first passband by adjusting the coupling gap S1, and adjusts the center frequency of the first passband by adjusting the dimensions (length and width) of resonator A21. Correspondingly, this invention can adjust the bandwidth and center frequency of the second passband by adjusting the side length L2, the connecting side length L5, and the coupling gap S2 of resonator B22. It should be noted that during production, the dimensions of resonators A21 and B22 can be adjusted according to actual needs to meet specific requirements.
[0040] To elaborate further, such as Figure 3As shown, the gap between the adjacent sides of two resonators A21 is the coupling gap S1, the gap between the adjacent sides of two resonators B22 is the coupling gap S2, the length of the side of resonator A21 is L4, the length of the connecting side of resonator A21 is L3, the length of the side of resonator B22 is L2, the length of the connecting side of resonator B22 is L5, the length of feed line 31 is L6, and the gap between transmission line 3 and the adjacent adjacent side of resonator A is the coupling gap S4.
[0041] By adjusting the coupling gap S1 between the two resonators A21, the bandwidth and insertion loss of the first passband are optimized, resulting in a wider bandwidth and lower insertion loss. Furthermore, changing the length L4 of resonator A21 alters the center frequency of the first passband. Two open-circuit stubs are respectively loaded onto corresponding quarter-wavelength resonators, forming the bandpass of the first passband. Without increasing the size of resonator A21, the added open-circuit stubs effectively adjust the center frequency of the first passband, reducing the filter size and facilitating miniaturization and integration. Additionally, by adjusting the coupling gap S2 and resonant lengths L2 and L5 between the two resonators B22, the bandwidth and frequency characteristics of the second passband are effectively optimized. Thus, the dual-band filter designed in this invention allows both the first and second passbands to reach the required frequency ranges, achieving a wider bandwidth and lower insertion loss, meeting the requirements of dual-band communication.
[0042] like Figure 1-3 As shown, in this embodiment, the coupling gap S1 between the two resonators A21 is 1.24 mm, the coupling gap S2 between the two resonators B is 0.245 mm, and the coupling gap between the two resonators A and their corresponding transmission lines 3 is 0.1425 mm, and the coupling gap between the two resonators B and their corresponding transmission lines 3 is 0.25 mm. In the microstrip line structure 2 described above, the thickness of resonators A and B is 0.035 mm. In this embodiment, the size of the dual-frequency filter can be 19.5 mm x 24 mm.
[0043] Furthermore, in this embodiment, the two passbands of the dual-band pass filter have a wide relative bandwidth and are relatively flat, which can meet the communication requirements of multiple frequency bands of the center frequency. The center frequency loss of the first passband is 0.67dB and the center frequency loss of the second passband is 0.82dB, that is, the insertion loss within the passband is low.
[0044] Furthermore, in this embodiment, in combination with Figure 3 As shown, the dimensions of this utility model are obtained according to the dimensions described above and the dimensions listed in Table 1 below. Figure 9 The simulation diagram shown in this embodiment... Figure 5 As shown - Figure 9The units for the coupling gaps S1 and S2 shown are millimeters, and the units for the values in the table below are also millimeters.
[0045]
[0046] Simulation results show that the center frequency of the first passband of this invention is 2.4 GHz, the bandwidth of the operating frequency is 250 MHz, and the center frequency loss (i.e., insertion loss) in the first passband is 0.67 dB; the center frequency of the second passband is 5.25 GHz, the bandwidth of the operating frequency is 385 MHz, and the center frequency loss (i.e., insertion loss) in the second passband is 0.82 dB; in the stopband outside the two passbands, the frequency band outside the stopband is quickly suppressed to below -20 dB, which improves the out-of-band suppression capability and the second harmonic suppression performance, thus improving the working performance of this invention.
[0047] This invention relates to a dual-bandpass filter based on a combined symmetrical resonator. By configuring a combination of a quarter-wavelength resonator and a half-wavelength resonator with open-circuit stubs, it achieves two frequency bands with wide passband ranges and low insertion loss, and improves the integration and anti-interference capability of this invention.
[0048] The above description is only a preferred embodiment of this invention. All equivalent changes and modifications made within the scope of the claims of this utility model shall fall within the scope of the claims of this utility model.
Claims
1. A dual-bandpass filter based on combined symmetrical resonators, comprising a ground metal plate, a substrate disposed on the ground metal plate, a microstrip line structure disposed on the substrate, and two transmission lines disposed on the substrate and arranged opposite to each other, characterized in that: The microstrip line structure includes two symmetrically arranged resonant combinations. Each set of resonant combinations includes resonators A and B arranged side-by-side. The two resonators A and B are arranged close to each other. Both resonators A are quarter-wavelength open-stub resonators in a mountain-shaped configuration. The open-stubs in each resonator A are located at the middle of their respective bottoms and are arranged parallel to the two sides of the corresponding resonator A. Both resonators B are U-shaped half-wavelength resonators. The openings of resonators A and B in each resonant combination face the same side. Two transmission lines are located on both sides of the microstrip line structure and are arranged in parallel coupling with the resonators A and B in the corresponding resonant combinations. The first ends of the two transmission lines are respectively provided with input ports and output ports.
2. The dual-bandpass filter based on combined symmetrical resonators according to claim 1, characterized in that: Metal through holes are respectively opened at the ends of the two resonators A on their adjacent sides, and each metal through hole passes through the substrate and the grounding metal plate in sequence.
3. The dual-bandpass filter based on combined symmetrical resonators according to claim 2, characterized in that: The inner diameter of the metal through hole is 0.8 mm.
4. The dual-bandpass filter based on combined symmetrical resonators according to claim 1, characterized in that: The coupling gap between the two resonators A is 1.24 mm, and the coupling gap between the two resonators A and the corresponding transmission lines is 0.1425 mm.
5. The dual-bandpass filter based on combined symmetrical resonators according to claim 4, characterized in that: The coupling gap between the two resonators B is 0.245 mm, and the coupling gap between the two resonators B and the corresponding transmission line is 0.25 mm.
6. The dual-bandpass filter based on combined symmetrical resonators according to claim 5, characterized in that: The two resonators A are used for resonance at a first passband center frequency of 2.4 GHz, and the two resonators B are used for resonance at a second passband center frequency of 5.25 GHz.
7. The dual-bandpass filter based on combined symmetrical resonators according to any of claims 1-6, characterized in that: The first ends of the two transmission lines are respectively connected to feeder lines, and the two feeder lines are respectively arranged perpendicular to the corresponding transmission lines. One end of the two feeder lines is respectively connected to the input port and the output port.
8. The dual-bandpass filter based on combined symmetrical resonators according to any of claims 1-6, characterized in that: The substrate is a dielectric substrate, and the substrate has a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness of 0.8 mm.