Hrr-based composite left-and-right-handed dual-mode microstrip dual-band bandpass filter and design method thereof
Patent Information
- Application Number
- CN202611145914.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-30
- Publication Date
- 2026-11-03
Smart Images
Figure CN123034805A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of bandpass filter technology, and in particular to a composite left- or right-handed dual-mode microstrip dual-passband bandpass filter based on HRR and its design method. Background Technology
[0002] Existing dual-passband filters typically employ multiple cascaded or parallel single-frequency resonators, or multimode structures such as SIR, stub-loaded resonators, patch resonators, and traditional HRR. While the former offers relatively intuitive adjustment of the two passbands, it results in a larger circuit area and higher cascading losses. The latter has a more compact structure, but the two resonant modes often share the same current path or are affected by the same geometric parameters, making it difficult to control the frequency ratio and passband bandwidth independently and simultaneously.
[0003] With the development of wireless communication, satellite communication, the Internet of Things, and multi-band RF front-ends, systems often need to simultaneously perform signal selection and spectrum isolation in multiple mutually separate operating frequency bands. Dual-passband bandpass filters can provide two passbands in a single device, reducing the number of passive front-end components, improving system integration, and enhancing interference immunity.
[0004] Currently, there are two main implementation methods for dual-passband filters. The first method uses a combination of multiple resonators with different center frequencies, such as cascading or paralleling two single-passband filter units. This approach has a clear design concept, but each passband typically requires an independent resonator, which can easily lead to increased circuit area, increased connection losses, and decreased integration density. The second method uses multimode resonators, such as step impedance resonators, stub-loaded resonators, rectangular patch resonators, or hairpin ring resonators, generating two passbands through multiple modes of a single resonant structure. This method is advantageous for miniaturization, but parameter coupling often exists between different modes; adjusting one frequency or bandwidth will simultaneously affect the other passband.
[0005] Hairpin ring resonators (HRRs) have advantages such as compact closed-loop structure, the ability to load stubs, and ease of constructing high-order filters, and have been used in dual-passband filters and common-mode filters. However, the two resonant modes of a traditional HRR are usually determined by both the loop path and the stub path. Parameters such as coupling spacing and crossover distance will affect both passbands simultaneously, making it difficult to achieve truly independent adjustment of the center frequency, frequency ratio, coupling coefficient, and bandwidth.
[0006] Therefore, it is necessary to introduce new quasi-lumped interpolation capacitors and bent inductor loading structures on the basis of HRR to separate the current paths of the two resonant modes. Furthermore, the coupling strength of the two passbands can be adjusted separately through independent coupling gaps, thereby realizing a miniaturized, flexible frequency ratio and independently controllable bandwidth dual-passband filter design. Summary of the Invention
[0007] To address the aforementioned technical problems, this invention provides a composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR and its design method. This invention primarily utilizes a dielectric substrate, an input feed line and an output feed line disposed on the dielectric substrate, and at least one dual-mode Meta-HRR resonant unit to achieve bandpass filtering in two target frequency bands. By providing a dual-passband microstrip filter with a compact structure, flexible frequency ratio adjustment range, separable controllable center frequencies of the two passbands, independently designable bandwidths of the two passbands, and good passband selectivity, this invention overcomes the problems of strong mode coupling, insufficient bandwidth adjustment freedom, and limited miniaturization in traditional HRR and existing multi-mode dual-passband filters.
[0008] The technical means employed in this invention are as follows: A composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR, comprising: Dielectric substrate; An input feed line, an output feed line, and at least one dual-mode Meta-HRR resonant unit are disposed on the dielectric substrate; The input feed line and the output feed line are respectively coupled to the corresponding dual-mode Meta-HRR resonant unit to achieve bandpass filtering in two target frequency bands.
[0009] Furthermore, the dual-mode Meta-HRR resonant unit includes an inner hairpin interdigital capacitor loading region and an outer hairpin double-bend inductor loading region; The internal hairpin interdigitated capacitor loading area is located on the upper part of the resonator. By changing the number of interdigitated capacitors N, the interdigitated length and the spacing, the resonant mode corresponding to the low-frequency passband can be adjusted. The external card double-bend inductor loading area is located at the bottom of the resonator. By changing the total length L1 of the double-bend path or the relevant bend size, the corresponding resonant mode of the high-frequency passband can be adjusted.
[0010] Furthermore, when the number N of the interdigitated capacitors in the internal hairpin is changed, the low-frequency resonant point shifts significantly, while the high-frequency resonant point changes less. When the path length of the external double-bend inductor is changed, the high-frequency resonant point shifts significantly, while the low-frequency resonant point remains basically stable.
[0011] Furthermore, an inner hairpin coupling gap d1 and an outer hairpin coupling gap d2 are provided between the dual-mode Meta-HRR resonant units; The internal hairpin coupling gap d1 is used to control the coupling coefficients of the low-frequency passband and the high-frequency passband; The external card coupling gap d2 is used to control the coupling coefficient of the high-frequency passband; When the inner hairpin coupling gap d1 and the outer hairpin coupling gap d2 increase, the coupling coefficient of the corresponding passband decreases, thereby realizing independent adjustment of the passband bandwidth.
[0012] Furthermore, a power coupling gap g is provided between the input feed line and the output feed line and the resonant unit to adjust the external quality factor and improve the passband matching.
[0013] This invention also provides a design method for a composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR, the specific steps of which include: S1: Determine the dielectric substrate parameters and the initial external dimensions of the resonator based on the target low-frequency passband center frequency fL, the target high-frequency passband center frequency fH, and the target relative bandwidth. S2: Introducing an internal hairpin interdigital capacitor and an external hairpin double-bend inductor path to form a dual-mode Meta-HRR resonant unit; S3: The low-frequency resonant mode is determined by scanning the number N of interdigital capacitors in the inner hairpin, the length of the interdigital capacitors, and the spacing; the high-frequency resonant mode is determined by scanning the length L1 of the double-bend path of the outer hairpin. S4: By scanning the inner hairpin coupling gap d1 and the outer hairpin coupling gap d2, the required coupling coefficients for the low-frequency passband and high-frequency passband are obtained respectively; S5: The resonator is combined with the input and output feed lines to form a dual-passband filter, and the S-parameters are jointly optimized so that the two passbands simultaneously meet the requirements of center frequency, bandwidth, return loss, insertion loss and out-of-band rejection.
[0014] Compared with the prior art, the present invention has the following advantages: This invention introduces two relatively independent resonant paths through an internal hairpin interdigital capacitor and an external hairpin double-bend inductor. The low-frequency passband is mainly determined by the internal hairpin interdigital capacitor loading path, while the high-frequency passband is mainly determined by the external hairpin double-bend inductor path. Therefore, a flexible frequency ratio can be obtained within a smaller structure, avoiding the frequency tuning difficulties caused by the strong coupling of traditional multimode HRR parameters.
[0015] This invention allows for independent adjustment of the coupling coefficients of the low-frequency and high-frequency passbands by setting an inner hairpin coupling gap d1 and an outer hairpin coupling gap d2. The low-frequency coupling coefficient mainly varies with d1, while the high-frequency coupling coefficient can be further adjusted through d2 and related coupling regions, thus providing a structural basis for the independent design of the relative bandwidths of the two passbands.
[0016] The interdigital capacitors used in this invention increase the equivalent capacitance, and the double-bend path increases the equivalent inductance. This extends the equivalent electrical length without significantly increasing the planar area, thereby reducing the resonant frequency and compressing the device size. The overall size of the example structure can reach the order of 0.227λg × 0.13λg, which is beneficial for reducing the size and weight of the RF front-end.
[0017] The dual-passband bandpass filter structure in this invention can form multiple transmission zeros on the left side, between the passbands, and on the right side of the two passbands, which is beneficial for improving out-of-band suppression and inter-passband isolation, and is suitable for dual-band signal selection under conditions of spectrum resource congestion.
[0018] In the high-temperature superconducting YBCO / MgO substrate embodiment, the dual-passband bandpass filter of this invention has an in-band insertion loss of less than 0.1 dB (excluding connector loss) and a return loss of better than 20 dB, making it suitable for microwave front-end systems with high requirements for low loss and high selectivity.
[0019] This invention maps center frequency adjustment, coupling coefficient adjustment, and power supply matching adjustment to geometric parameters such as N, L1, d1, d2, and g1 / g2, respectively, which facilitates design by combining electromagnetic simulation or automatic optimization algorithms. It can also be extended to dual-passband filters with different frequency ratios, different orders, or different substrate materials. Attached Figure Description
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the composite left- and right-handed dual-mode microstrip dual-passband bandpass filter structure based on HRR in this invention.
[0022] Figure 2 This is a schematic diagram of the dual-mode Meta-HRR resonant unit structure in an embodiment of the present invention.
[0023] Figure 3 This is a schematic diagram showing the change of the inner ring resonant frequency with the cross-index quantity in an embodiment of the present invention.
[0024] Figure 4 This is a schematic diagram illustrating the change in the bending length of the outer ring resonant frequency in an embodiment of the present invention.
[0025] Figure 5 This is a schematic diagram of the simulation results of HRR parameters in an embodiment of the present invention. Detailed Implementation
[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0029] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.
[0030] like Figure 1 As shown, the present invention provides a composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR, comprising: a dielectric substrate; An input feed line, an output feed line, and at least one dual-mode Meta-HRR resonant unit are disposed on the dielectric substrate; when a higher-order response is required, two or more adjacent coupled dual-mode Meta-HRR resonant units can be disposed.
[0031] The input feed line and the output feed line are respectively coupled to the corresponding dual-mode Meta-HRR resonant unit to achieve bandpass filtering in two target frequency bands.
[0032] In a specific implementation, as a preferred embodiment of the present invention, the dual-mode Meta-HRR resonant unit is a structure improved based on the traditional hairpin ring resonator. The dual-mode Meta-HRR resonant unit includes an inner hairpin interdigital capacitor loading region and an outer hairpin double-bend inductor loading region; The internal hairpin interdigitated capacitor loading area is located on the upper part of the resonator. By changing the number of interdigitated capacitors N, the interdigitated length and the spacing, the resonant mode corresponding to the low-frequency passband can be adjusted. The external card double-bend inductor loading area is located at the bottom of the resonator. By changing the total length L1 of the double-bend path or the relevant bend size, the corresponding resonant mode of the high-frequency passband can be adjusted.
[0033] Because the current distributions of the inner hairpin interdigital capacitor path and the outer hairpin double-bend inductor path are relatively separate, the two resonant modes can be adjusted independently. In a preferred embodiment of the invention, changing the number N of the inner hairpin interdigital capacitors results in a significant shift in the low-frequency resonant point, while the high-frequency resonant point changes less. When the path length of the external double-bend inductor is changed, the high-frequency resonant point shifts significantly, while the low-frequency resonant point remains basically stable.
[0034] In practice, by setting N and L1 respectively, the center frequency of the dual passband and the frequency ratio k=fH / fL can be flexibly designed.
[0035] In a specific implementation, as a preferred embodiment of the present invention, the dual-mode Meta-HRR resonant units are provided with an inner hairpin coupling gap d1 and an outer hairpin coupling gap d2. The internal hairpin coupling gap d1 is used to control the coupling coefficients of the low-frequency passband and the high-frequency passband; The external card coupling gap d2 is used to control the coupling coefficient of the high-frequency passband; When the inner hairpin coupling gap d1 and the outer hairpin coupling gap d2 increase, the coupling coefficient of the corresponding passband decreases, thereby realizing independent adjustment of the passband bandwidth.
[0036] In a specific implementation, as a preferred embodiment of the present invention, a power coupling gap g is also provided between the input feed line and the output feed line and the resonant unit, which is used to adjust the external quality factor and improve the passband matching.
[0037] Compared with traditional dual-passband filters, this invention decomposes the frequency design and bandwidth design of dual-passband filters into relatively independent geometric parameter tuning processes by using an internal hairpin interdigital capacitor to tune the low frequency, an external hairpin double-bend inductor to tune the high frequency, and d1 / d2 to tune the bandwidth respectively. This results in a high degree of design freedom and is suitable for miniaturized multi-band RF front-end integration.
[0038] This invention also provides a design method for a composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR, the specific steps of which include: S1: Determine the dielectric substrate parameters and the initial external dimensions of the resonator based on the target low-frequency passband center frequency fL, the target high-frequency passband center frequency fH, and the target relative bandwidth. S2: Introducing an internal hairpin interdigital capacitor and an external hairpin double-bend inductor path to form a dual-mode Meta-HRR resonant unit; S3: The low-frequency resonant mode is determined by scanning the number N of interdigital capacitors in the inner hairpin, the length of the interdigital capacitors, and the spacing; the high-frequency resonant mode is determined by scanning the length L1 of the double-bend path of the outer hairpin. S4: By scanning the inner hairpin coupling gap d1 and the outer hairpin coupling gap d2, the required coupling coefficients for the low-frequency passband and high-frequency passband are obtained respectively; S5: The resonator is combined with the input and output feed lines to form a dual-passband filter, and the S-parameters are jointly optimized so that the two passbands simultaneously meet the requirements of center frequency, bandwidth, return loss, insertion loss and out-of-band rejection.
[0039] Example This embodiment uses a MgO dielectric substrate with double-sided YBCO high-temperature superconducting thin films, a substrate thickness h = 0.5 mm, a relative permittivity of 9.78, and a resonator linewidth of 0.08 mm. The substrate can also be replaced with other low-loss dielectric substrates depending on the actual application.
[0040] like Figure 2 As shown, the dual-mode Meta-HRR of this invention is an improvement upon the conventional HRR. The conventional HRR includes a closed square ring and open stubs. This invention introduces an internal hairpin interdigital capacitor at the upper stub location and an external hairpin double-bend inductor path in the lower ring region. The interdigital capacitor increases the local equivalent capacitance, and the double-bend path increases the equivalent inductance, thereby forming two controllable resonant modes within a smaller area.
[0041] like Figure 3 As shown, while keeping other dimensions constant, when the number of interdigital capacitors in the inner hairpin changes from 13 to 15, the low-frequency resonant frequency excited by the inner hairpin shifts significantly, while the high-frequency resonant frequency excited by the outer hairpin changes less.
[0042] like Figure 4 As shown, when the total length L1 of the double bend of the outer hairpin is adjusted, the high-frequency resonant frequency shifts significantly, while the low-frequency resonant frequency remains basically stable. Therefore, this invention can achieve separate adjustment of the center frequencies of the two passbands.
[0043] As a specific embodiment, a dual-passband filter with a relatively low frequency is designed, such as... Figure 1As shown. The key dimensions of this filter are: L2=1.88mm, L3=3.08mm, L4=1.24mm, L5=0.78mm, L6=2.82mm, g1=0.04mm, g2=1.48mm, g3=0.02mm, g4=0.08mm, g5=1.26mm, d1=0.2mm, d2=0.12mm. Input port Port1 and output port Port2 are coupled to the adjacent Meta-HRR resonant unit through feed lines. The inner hairpin region and the outer hairpin region form the low-frequency and high-frequency passband responses, respectively.
[0044] like Figure 5 The figure shows the S-parameter simulation results of the filter of the present invention in the 1.8 GHz and 2.4 GHz frequency bands. The horizontal axis represents frequency (GHz), and the vertical axis represents amplitude (dB). As can be seen from the figure, the device forms an operating passband near the 1.8 GHz and 2.4 GHz frequency bands, respectively. S11 is below -20 dB, and there is a transmission zero before and after the passband and between the passbands, demonstrating good filtering characteristics. According to Sonnet full-wave electromagnetic simulation, the two 3 dB passbands of the filter are 1.78 GHz to 1.83 GHz and 2.33 GHz to 2.45 GHz, respectively, with relative fractional bandwidths of 2.77% and 5%.
[0045] Simulation results also show that this embodiment can generate transmission zeros on the left side of the two passbands, between the passbands, and on the right side of the passbands, thereby improving filter selectivity. The overall filter size is approximately 0.227λg × 0.13λg, where λg is the guided wave wavelength at the center frequency of the low-frequency passband (1.8 GHz). The in-band insertion loss is less than 0.1 dB (excluding connector loss), and the return loss is better than 20 dB, indicating that this structure combines miniaturization, low loss, and high selectivity.
[0046] In practical design, based on the target frequency and target bandwidth, the dielectric substrate, linewidth, and overall dimensions are first determined. Then, the parameters of the inner hairpin interdigital capacitance and the outer hairpin bending path are scanned to determine the two center frequencies. Subsequently, d1 and d2 are scanned to obtain the target coupling coefficient. Finally, the feeder coupling gap and overall structure are jointly optimized across the entire wave. This process can be extended to the design of dual-passband filters with different frequency bands, different frequency ratios, and different orders.
[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR, characterized in that, include: Dielectric substrate; An input feed line, an output feed line, and at least one dual-mode Meta-HRR resonant unit are disposed on the dielectric substrate; The input feed line and the output feed line are respectively coupled to the corresponding dual-mode Meta-HRR resonant unit to achieve bandpass filtering in two target frequency bands.
2. The composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR according to claim 1, characterized in that, The dual-mode Meta-HRR resonant unit includes an inner hairpin interdigital capacitor loading region and an outer hairpin double-bend inductor loading region. The internal hairpin interdigitated capacitor loading area is located on the upper part of the resonator. By changing the number of interdigitated capacitors N, the interdigitated length and the spacing, the resonant mode corresponding to the low-frequency passband can be adjusted. The external card double-bend inductor loading area is located at the bottom of the resonator. By changing the total length L1 of the double-bend path or the relevant bend size, the corresponding resonant mode of the high-frequency passband can be adjusted.
3. The composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR according to claim 2, characterized in that, When the number N of the internal hairpin interdigitated capacitors is changed, the low-frequency resonant point shifts significantly, while the high-frequency resonant point changes less. When the path length of the external double-bend inductor is changed, the high-frequency resonant point shifts significantly, while the low-frequency resonant point remains basically stable.
4. The composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR according to claim 1, characterized in that, The dual-mode Meta-HRR resonant units are provided with an inner hairpin coupling gap d1 and an outer hairpin coupling gap d2; The internal hairpin coupling gap d1 is used to control the coupling coefficients of the low-frequency passband and the high-frequency passband; The external card coupling gap d2 is used to control the coupling coefficient of the high-frequency passband; When the inner hairpin coupling gap d1 and the outer hairpin coupling gap d2 increase, the coupling coefficient of the corresponding passband decreases, thereby realizing independent adjustment of the passband bandwidth.
5. The composite left- and right-handed dual-mode microstrip dual-passband bandpass filter based on HRR according to claim 1, characterized in that, A power coupling gap g is also provided between the input feed line and the output feed line and the resonant unit to adjust the external quality factor and improve the passband matching.
6. A design method for a composite left- or right-handed dual-mode microstrip dual-passband bandpass filter based on HRR, implemented according to any one of claims 1-5, characterized in that, The specific steps include: S1: Determine the dielectric substrate parameters and the initial external dimensions of the resonator based on the target low-frequency passband center frequency fL, the target high-frequency passband center frequency fH, and the target relative bandwidth. S2: Introducing an internal hairpin interdigital capacitor and an external hairpin double-bend inductor path to form a dual-mode Meta-HRR resonant unit; S3: The low-frequency resonant mode is determined by scanning the number N of interdigital capacitors in the inner hairpin, the length of the interdigital capacitors, and the spacing; the high-frequency resonant mode is determined by scanning the length L1 of the double-bend path of the outer hairpin. S4: By scanning the inner hairpin coupling gap d1 and the outer hairpin coupling gap d2, the required coupling coefficients for the low-frequency passband and high-frequency passband are obtained respectively; S5: The resonator is combined with the input and output feed lines to form a dual-passband filter, and the S-parameters are jointly optimized so that the two passbands simultaneously meet the requirements of center frequency, bandwidth, return loss, insertion loss and out-of-band rejection.