CN113394529A

CN113394529A - Double-passband filter

Info

Publication number: CN113394529A
Application number: CN202110940133.7A
Authority: CN
Inventors: 李伟; 丁正阳; 戴勇; 汪大洋; 江凇; 贾平; 李沛; 蒋春霞; 蔡昊; 徐惠臣
Original assignee: Information and Telecommunication Branch of State Grid Jiangsu Electric Power Co Ltd
Current assignee: Information and Telecommunication Branch of State Grid Jiangsu Electric Power Co Ltd
Priority date: 2021-08-17
Filing date: 2021-08-17
Publication date: 2021-09-14

Abstract

The invention discloses a dual-passband filter, which belongs to the technical field of microwaves and comprises the following components: one side of the dielectric substrate comprises a metal ground, an input feeder line and an output feeder line, the metal plate on the other side of the dielectric substrate comprises a dual-passband ring resonator, the dual-passband ring resonator comprises a first ring resonator and a second ring resonator nested in the first ring resonator, the input feeder line and the output feeder line both adopt coplanar waveguide feeder lines, and the ground plane of the coplanar waveguide feeder lines is the metal ground. The dual-passband filter based on the dual-mode ring resonator and the coplanar waveguide feed design provided by the invention effectively reduces the size in the design.

Description

Double-passband filter

Technical Field

The invention belongs to the technical field of microwaves, and mainly relates to a dual-passband filter based on coplanar waveguide (CPW) feed and a dual-mode ring resonator.

Background

The filter plays a crucial role in the radio frequency front end. The filter can filter out the interference and transmission noise outside the pass band to meet the requirement of communication protocol in radio frequency system for signal-to-noise ratio. The variety of filters is largely classified into an LC filter, a microstrip filter, a waveguide filter, a Substrate Integrated Waveguide (SIW) filter, and a hybrid transmission line filter according to a manufacturing process and an implementation manner. At present, the filter is mainly studied in multiband filters, ultra-wideband filters, reconfigurable filters, differential filters, and the like. Along with communication system is bigger and heavier more and more to take 4G time as an example, the number of radio frequency filters that need in a cell-phone is about 40, works in 1, 2, 3 and 4G module, WIFI module, Bluetooth module and GPS module respectively. With the coming of the 5G era, the number of filters required by the radio frequency front end is about to double.

The dual-passband filter has the advantage that one filter can replace two single-passband filters, greatly reducing the size of the circuit. In the last fifteen years there has been considerable interest in the design of single-pass and dual-pass band filters using dual-mode ring resonators.

However, the dual-mode ring resonator still has a larger size at present, and cannot meet the requirement of the microwave technical field on miniaturization of the filter.

Disclosure of Invention

The invention aims to overcome the defects and shortcomings in the prior art and provide a dual-passband filter with smaller size.

In order to achieve the technical purpose, the invention adopts the following technical scheme.

According to the embodiment, the dual-passband filter with smaller size comprises a dielectric substrate, one metal plate of the dielectric substrate comprises a metal ground and etched input feed lines and output feed lines, the other metal plate of the dielectric substrate comprises dual-passband ring resonators, the dual-passband ring resonators comprise first ring resonators and second ring resonators nested in the first ring resonators, the input feed lines and the output feed lines are coplanar waveguide feed lines, and the ground plane of the coplanar waveguide feed lines is the metal ground.

Further in accordance with an embodiment, the first ring resonator and the second ring resonator both employ square ring resonators, which are a first square ring resonator and a second square ring resonator, respectively.

Furthermore, the metal plate on the other side of the dielectric substrate further comprises a first perturbation patch and a second perturbation patch besides the double-passband annular resonator, the first perturbation patch is located at one corner of the first square-shaped annular resonator and connected with the first square-shaped annular resonator, the second perturbation patch is located at one corner of the second square-shaped annular resonator and connected with the second square-shaped annular resonator, and the direction of the first perturbation patch located on the first square-shaped annular resonator is the same as the direction of the second perturbation patch located on the second square-shaped annular resonator.

Furthermore, the first perturbation patch and the second perturbation patch are both formed by rectangular microstrip patches.

Furthermore, the second square ring resonator comprises a closed-loop square microstrip line, four vertex angles of the closed-loop square microstrip line are respectively provided with an opening, each opening is located in the inner direction of the closed-loop square microstrip line and is respectively connected with an arrow structure, each arrow structure comprises two microstrip lines with equal length, an included angle between the two microstrip lines is 90 degrees, and the angle direction of the arrow structure is consistent with the outer edge of the vertex angle of the closed-loop square microstrip line.

Further, the input feeder line and the output feeder line have the same structure and size and form an angle of 90 degrees with each other.

Further, the coplanar waveguide feeder comprises 2 first slot lines, 2 second slot lines, 2 third slot lines, 2 fourth slot lines, 2 fifth slot lines, 2 sixth slot lines, 2 seventh slot lines and 1 eighth slot line; the 2 first groove lines are vertically parallel, the 2 second groove lines are respectively and vertically connected with the 2 first groove lines and are opposite in direction, the 2 third groove lines are respectively and vertically connected with the 2 second groove lines and are vertically parallel in direction, the 2 fourth groove lines are respectively and vertically connected with the 2 third groove lines and are horizontal in direction, the 2 fifth groove lines are respectively and vertically connected with the 2 fourth groove lines and are vertically parallel in direction, and the 2 sixth groove lines are respectively and vertically connected with the 2 fifth groove lines and are horizontal in direction; 2 seventh slotlines link to each other with 2 sixth slotlines are perpendicular respectively and the direction is vertical parallel, and 2 seventh slotlines and direction level are connected respectively to the both ends of 1 eighth slotline.

The invention has the following beneficial technical effects: the invention adopts a dual-mode dual-passband filter which is nested inside and outside and is fed by coplanar waveguide (CPW), and can overcome the defect that the dual-mode square ring resonator shown in figure 1(a) can not be fed by parallel coupling. The feeding structure adopts a coplanar waveguide (CPW) feeding structure, compared with the traditional parallel coupling feeding, the CPW feeding has wider external quality factor and structural design flexibility, and the dual-band-pass filter based on the dual-mode ring resonator and the coplanar waveguide feeding design provided by the invention effectively reduces the size in the design.

The double-passband filter is formed by nesting two double-mode rings, an inner ring is a double-mode ring resonator with an arrow structure, an outer ring is a traditional double-mode ring resonator, a gap between the arrow and the ring resonator forms an effective capacitor, and the adjustment of the physical sizes of the four arrows has the effect of changing the equivalent capacitor so as to change the resonance frequency, thereby being more beneficial to realizing the function of miniaturization of the resonator.

Drawings

Fig. 1(a) to 1(e) are structures that can be employed for resonators in specific embodiments; wherein, fig. 1(a) is a square ring resonator, fig. 1(b) is a square ring resonator with an arrow structure, fig. 1(c) is a parallel coupling feeding square ring resonator, fig. 1(d) is a coplanar waveguide (CPW) coupling feeding square resonator, and fig. 1(e) is a parallel coupling feeding square arrow loading resonator;

FIG. 2 shows the resonator of FIG. 1(b) with respect to L1 andL _{_C}results of the change of the resonant frequencyA drawing;

FIG. 3 is a view of the resonator shown in FIG. 1(a) with respect top _{_o}The result of the change of the resonant frequency is shown schematically; (L1 = 30mm, W1= 1.1 mm, S1= 0.5 mm, L3= 7 mm);

FIG. 4 shows the resonator of FIG. 1(b) with respect to the length of the perturbation patchPA change in resonance frequency of (L2 =22.5 mm, W2=1.1 mm, S2=0.4 mm, L5=21 mm);

FIG. 5 is a simulation of a parallel coupled feed filter based on the resonators shown in FIG. 1 (a);

FIG. 6 is a simulation of a parallel-coupled-feed single-passband filter based on the resonators shown in FIG. 1 (b);

fig. 7 is a graph of the variation of Q values for coplanar waveguide feed and parallel coupled feed (L1 = L = 30mm, W1= 1.1 mm, L3= L = 5 mm, S1= 0.15 mm, L4= 3 mm);

FIG. 8 is a schematic diagram of a dual bandpass filter structure provided in an exemplary embodiment;

FIG. 9 is a dimensional diagram of a coplanar waveguide feed structure in an exemplary embodiment;

FIG. 10 is a schematic diagram of a dual band-pass ring resonator structure in an exemplary embodiment;

FIG. 11 is a schematic diagram of a coplanar waveguide feed structure in an exemplary embodiment;

FIG. 12 is dual bandpass filter simulation data provided by an exemplary embodiment;

FIG. 13 is a graph comparing dual bandpass filter measurement data to simulation data;

wherein the figures are labeled:

1-a first square ring resonator; 2-a second square ring resonator; 3-a dielectric substrate; 4-metal ground; 5-input feeder; 6-output feeder; 7-a first slot line; 8-a second slot line; 9-a third slotline; 10-a first perturbation patch; 11-a second perturbation patch; 12-an opening; 13-a microstrip line; 14-a fourth slotline; 15-fifth slot line; 16-a sixth slotline; 17-a seventh slotline; 18-eighth slotline.

Detailed Description

The invention is further described with reference to the drawings and the specific embodiments in the following description.

The following examples are given to illustrate the detailed embodiments of the present invention on the premise of the technical solution of the present invention, but the scope of the present invention is not limited to the following examples.

In the description of the present invention, it is to be understood that the terms "inside", "outside", "upper", "top", "lower", "left", "right", "vertical", "horizontal", "parallel", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore, should not be taken as limiting the scope of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in one embodiment" or "in some embodiments" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Example 1: a dual bandpass filter comprising: the dielectric substrate, one side of dielectric substrate includes the metal ground and the input feeder and the output feeder of sculpture, includes dual passband ring resonator on the metal sheet of the another side of dielectric substrate, dual passband ring resonator includes first ring resonator and nestification second ring resonator in among the first ring resonator, input feeder and output feeder all adopt coplanar waveguide feeder, coplanar waveguide feeder's ground plane is the metal ground.

The first ring resonator and the second ring resonator may be a square dual-mode ring resonator, an open ring resonator, or a circular dual-mode ring resonator, as known in the art. Square-ring resonators, i.e., a first square-ring resonator and a second square-ring resonator, are used as the first ring resonator and the second ring resonator in this embodiment.

The resonator adopted by the invention is a dual-mode square ring resonator, as shown in fig. 1(a) to 1 (e). The first square ring resonator may be a square ring resonator as shown in fig. 1 (a); the second square-ring resonator may be any one of the resonators shown in fig. 1(a) to fig. 1(e), where fig. 1(b) is a square-ring resonator with an arrow structure, fig. 1(c) is a square-ring resonator with parallel coupling feeding, fig. 1(d) is a square-ring resonator with coplanar waveguide (CPW) coupling feeding, and fig. 1(e) is a square-arrow loaded resonator with parallel coupling feeding.

The resonator structure shown in fig. 1(a) consists of a square ring plus a square patch in the upper right corner. Each arm length of the resonator is equal, L1 represents the physical length of one of the arm lengths, and the resonant frequency of the resonator occurs when L1 is approximately equal to a quarter of a waveguide wavelength, where the waveguide wavelength relationship can be expressed as:

, cis the propagation speed of the electromagnetic field in a vacuum,

in order to have an effective dielectric constant, a dielectric constant,fis arm length

The corresponding resonant frequency of. The role of the miniature square patch in the upper right corner is to excite and couple a pair of degenerate modes.

The resonator shown in fig. 1(b) is formed by adding four arrows to the four inner corners of the resonator shown in fig. 1 (a). The square ring resonator with the arrow structure comprises a closed-loop square microstrip line, wherein four top angles of the closed-loop square microstrip line are respectively provided with an opening, each opening is positioned in the inner direction of the closed-loop square microstrip line and is respectively connected with an arrow structure, the arrow structure comprises two microstrip lines with equal length, an included angle between the two microstrip lines with equal length is 90 degrees, and the angle direction is consistent with the outer edge of the top angle of the closed-loop square microstrip line. The gap between the arrow and the ring resonator forms a capacitor, and adjusting the physical size of the four arrows has the effect of changing the equivalent capacitance so as to change the resonance frequency, thereby realizing the function of miniaturization of the resonator.

When the arrow-structured resonator shown in fig. 1(b) extracts the resonance frequency of the degenerate mode in the case of weak coupling feeding, the variation curves of the two resonance frequencies of the resonator shown in fig. 1(b) are obtained, as shown in fig. 2. Without changing the physical size of the arrow, as the physical length L1 of the resonator increases, the two resonant frequencies of the dual-mode ring resonator gradually decrease and both exhibit a tendency to fall, but the difference between the two resonant frequencies remains substantially the same.

Under the condition of keeping the size of the resonator unchanged, the length of the side length L _ c of the arrow is gradually increased, the two resonant frequencies of the dual-mode ring resonator are also reduced, and the difference value of the two resonant frequencies is kept unchanged.

Therefore, the resonance frequency of the double-mode ring resonator with the arrowhead structure shown in fig. 1(b) is mainly adjusted by L1 and L _ c, but according to the extraction formula of the coupling coefficient

It can be seen that L1 and L _ c do not substantially affect the coupling coefficient of the dual mode loop.

Fig. 3 and 4 are graphs showing the relationship between the resonant frequency and the physical size of the perturbation square patch in the case of weak coupling feeding of the resonator shown in fig. 1(a) and the resonator shown in fig. 1(b), respectively.

From FIG. 3, it can be seen that the patch length is varied with perturbationp _{_o}The difference between the two resonant frequencies is gradually increased. Therefore, according to the formula for extracting the coupling coefficient, the coupling strength of the two modes of the resonator shown in fig. 1(a) increases as the size of the perturbation patch increases. From FIG. 4, it can be seen that the patch length is varied with perturbationPThe difference between the two resonant frequencies is gradually increased. Thus resonating as shown in FIG. 1(b)The coupling strength of the two modes of the device increases as the size of the perturbation patch increases.

The first filter shown in fig. 5 is a single-pass filter designed by the resonators and parallel coupling feed shown in fig. 1(a) as shown in fig. 1(c), and the 3dB bandwidth shown in fig. 5 is from 1.5GHz to 1.55GHz according to simulation data, which has the disadvantages that only one transmission pole is arranged in the pass band, and the insertion loss in the pass band is not good enough. The input and output of the parallel coupling structure are coupled to form two transmission zeros which are respectively at 1.38GHz and 1.65GHz, and the introduction of the transmission zeros effectively improves the out-of-band rejection capability.

FIG. 6 is a simulation of a parallel-coupled fed single-passband filter based on the resonators shown in FIG. 1 (b); the second filter shown in fig. 1(b) is designed as a single-passband filter according to the arrowhead loaded resonators plus parallel coupled feeding as shown in fig. 1 (e). The 3dB bandwidth is from 1.81GHz to 1.89GHz, although there are two transmission poles in the pass band, the return loss in the pass band does not perform well enough. Two transmission zeros are formed by input and output coupling of the parallel coupling structure, the zeros are respectively at 1.69GHz and 2.05GHz, and the introduction of the transmission zeros effectively improves the out-of-band rejection capability. In summary, in the case of parallel coupling feeding, the two single-passband dual-mode filters have the disadvantages of few poles and high insertion loss, and the latter has the worst return loss of about-10 dB. The parallel coupling feed structure can only be used for designing a single passband filter, and when two dual-mode rings are used for nesting to design the dual passband filter, the parallel coupling feed structure lacks flexibility and cannot meet the feed requirement of the inner ring.

FIG. 7 shows coupling coefficients along with coupling branches of the resonator shown in FIG. 1(a) in a parallel coupling feed structure, such as FIG. 1(c), and in a coplanar waveguide feed structure, such as FIG. 1(d), respectivelyLA graph of the variation relationship of (c). As can be seen from fig. 7, the CPW feeding structure can obtain a wider Q_eAnd the range can be used for designing a filter with wider or narrower bandwidth. In contrast, the parallel coupling has high efficiency in a limited range and thus can be used only for narrow band filter design, so the CPW feeding method has flexibility in design structure and better electrical performance.

In this embodiment, a dual-mode dual-passband filter nested inside and outside with coplanar waveguide (CPW) feeding is adopted, so that the defect that an inner-ring resonator cannot be fed by parallel coupling in a dual-mode square-ring resonator as shown in fig. 1(a) can be overcome. The feeding structure aspect adopts a coplanar waveguide (CPW) feeding structure, and compared with the traditional parallel coupling feeding, the CPW feeding has wider external quality factor and structural design flexibility. The dual-passband filter is formed by nesting two dual-mode rings, an inner ring is a dual-mode ring resonator with an arrow structure, and an outer ring is a traditional dual-mode ring resonator.

Example 2: as shown in fig. 8, a dual bandpass filter includes: the dielectric substrate 3, one side metal sheet of dielectric substrate 3 includes metal ground 4, input feeder 5 and output feeder 6 of sculpture on the metal sheet, includes dual-passband ring resonator on the another side metal sheet of dielectric substrate 3, dual-passband ring resonator includes first ring resonator and nestification second ring resonator in the first ring resonator, input feeder and output feeder all adopt coplanar waveguide feeder, the ground plane of coplanar waveguide feeder is metal ground.

Square-ring resonators, i.e., a first square-ring resonator 1 and a second square-ring resonator 2, are used for both the first ring resonator and the second ring resonator in the present embodiment. The first square ring resonator 1 can adopt a square ring resonator shown in fig. 1(a), and the square ring resonator is composed of a square ring and a square perturbation patch at the upper right corner; as shown in fig. 10, the first perturbation patch 10 is connected to the upper right corner of the first square ring resonator 1.

The second square-ring resonator 2 includes a closed-loop square microstrip line, as shown in fig. 10, four vertex angles of the closed-loop square microstrip line have an opening 12, each opening 12 is in an inner direction of the closed-loop square microstrip line and is connected with an arrow structure, the arrow structure includes two microstrip lines 13 with equal length, an included angle between the two microstrip lines 13 with equal length is 90 degrees, and an angle direction of the arrow structure is consistent with an outer edge of the vertex angle of the closed-loop square microstrip line. And a second perturbation patch 11 is connected and arranged at the upper right corner of the second square ring resonator 2.

Specific dimensions of coplanar waveguide (CPW) feeds are shown in fig. 9 and 10, where specific dimensions within the dashed circle have been shown enlarged as shown. The input feeder line and the output feeder line have the same structure and size and form an angle of 90 degrees with each other.

Alternatively, a specific dual-passband ring resonator structure is shown in fig. 11, the coplanar waveguide feeder includes 2

first slot lines

7, 2

second slot lines

8, 2

third slot lines

9, 2

fourth slot lines

14, 2

fifth slot lines

15, 2

sixth slot lines

16, 2

seventh slot lines

17, and 1 eighth slot line 18; the 2 first groove lines 7 are vertically parallel, the 2 second groove lines 8 are respectively vertically connected with the 2 first groove lines 7 and are opposite in direction, the 2 third groove lines 9 are respectively vertically connected with the 2 second groove lines 8 and are vertically parallel in direction, the 2 fourth groove lines 14 are respectively vertically connected with the 2 third groove lines 9 and are horizontal in direction, the 2 fifth groove lines 15 are respectively vertically connected with the 2 fourth groove lines 14 and are vertically parallel in direction, and the 2 sixth groove lines 16 are respectively vertically connected with the 2 fifth groove lines 15 and are horizontal in direction; the 2 seventh slot lines 17 are respectively connected with the 2 sixth slot lines 16 vertically and parallel to each other vertically, and the two ends of the 1 eighth slot line 18 are respectively connected with the 2 seventh slot lines 17 horizontally. As shown in fig. 11, all the slot lines separate the metal into a "dry" shape. This coplanar waveguide feed form has a wider range of Q values than parallel coupled feeds, while CPW feeds increase structural design flexibility. The coplanar waveguide feed structure shown in fig. 11 enables a relatively wider bandwidth to be achieved.

The height of the middle dielectric layer ishRockwell 4350 dielectric material with relative dielectric constant =3.66 of =0.508 mm.

The most ideal main parameter values obtained according to the simulation results are (as shown in fig. 9 and 10):

L1=30,L2=20,W1=1.1,W2=1.1,W_{_p_o}=1.1,p_{_o}=0.614,W_{_p}=1.13,

P=0.63,S1=0.4,L_{_c}=6.1,W_{_c}=0.5, L4=9.2, L5=9.61, L6=19.49, L7=19, W3=2.2, W4=2.59, W5=2.2, W6=2.61, W7=1.88mm, g1=1.7, g2= 0.1. All units are in millimeters.

From the results shown in fig. 12, it can be seen that the first passband has a 3dB bandwidth from 1.41 GHz to 1.48GHz, and the second passband has a 3dB bandwidth from 1.83 GHz to 1.92 GHz. Four transmission zeros are formed by input and output coupling of the feed structure and are respectively at 1.22 GHz,1.53 GHz,1.7 GHz and 2.12 GHz. As can be seen from FIG. 12, there are two transmission poles in the first pass band, and the return loss is-18 dB. The second pass band also has two poles and the return loss is also around-18 dB.

FIG. 13 is a graph of dual bandpass filter measurement data versus simulation data. It can be observed from fig. 13 that the actual measurement data and the simulation data are substantially identical, but the measurement data has only one pole in the low-pass band (two poles in the simulation data) and the center frequency point of the low-pass band is somewhat shifted, which may be due to manufacturing errors in the PCB processing process. From the data measured in fig. 13, it can be seen that the center frequency of the low pass band is 1.43 GHz and the center frequency of the high pass band is 1.88 GHz. The measured 3dB absolute bandwidths (FBW) for the low and high passbands were about 4.9% and 3.7%, respectively. Both return losses for both passbands are greater than 20 dB. Furthermore, four transmission zeros occur at 1.2 GHz, 1.52 GHz,1.7 GHz, and 2.17 GHz, which improves the out-of-band rejection capability of the filter.

After the embodiment is compared with the dual-passband filter of the same type in the prior art, the dual-passband filter based on the dual-mode ring resonator and the coplanar waveguide feed design is the smallest in size in the design of the same type, and is only 0.17λ _g×0.17λ _g（λ _g: low-pass band center frequency waveguide wavelength) substantially enabling miniaturization of the overall structure.

The arrow-structure double-mode ring resonator in the embodiment is improved based on a conventional double-mode ring resonator, and a gap existing between the arrow structure and the resonator is equivalent to capacitance. The size of the gap can be controlled by adjusting the physical structure of the arrow, so that the size of the equivalent capacitor is equivalently adjusted to influence the resonance frequency of the resonator, which is the key role in realizing the miniaturization of the band-pass filter.

A rectangular perturbation patch is used for coupling two resonance modes of the double-mode ring resonator, and the proper bandwidth of the band-pass filter is obtained by adjusting the coupling strength between the two resonance modes by adjusting the size of the coupling patch.

In order to verify the feasibility of the theory, two types of single bandpass filters are designed by respectively combining the parallel coupling feed structure with two types of dual-mode loops, such as a resonator shown in fig. 1(a) and a resonator shown in fig. 1 (b). FIG. 5 is a simulation of a parallel coupled feed filter based on the resonators shown in FIG. 1 (a); fig. 6 is a simulation of a parallel coupled feed filter based on the resonators shown in fig. 1 (b).

And secondly, comparing parallel coupling feed with coplanar waveguide feed, wherein the coplanar waveguide feed mode has a wider Q value range compared with the parallel coupling feed, and the CPW feed increases the structural design flexibility and can be used for designing a dual-passband filter nested inside and outside two dual-mode resonant rings. The double-mode resonator with the internal arrow structure is equivalent to a capacitor to realize frequency adjustability, the size of the dual-passband filter is reduced, and the miniaturization of the overall structure of the dual-passband filter is realized.

Claims

1. A dual-passband filter comprises a dielectric substrate and is characterized in that one metal plate of the dielectric substrate comprises a metal ground and an etched input feeder line and an etched output feeder line, the other metal plate of the dielectric substrate comprises a dual-passband ring resonator, the dual-passband ring resonator comprises a first ring resonator and a second ring resonator nested in the first ring resonator, the input feeder line and the output feeder line both adopt coplanar waveguide feeder lines, and the ground plane of the coplanar waveguide feeder lines is the metal ground.

2. A double bandpass filter according to claim 1, wherein the first ring resonator and the second ring resonator are square ring resonators, and are a first square ring resonator and a second square ring resonator, respectively.

3. A double pass band filter according to claim 2, wherein the other side metal plate of the dielectric substrate includes a first perturbation patch and a second perturbation patch in addition to the double pass band ring resonator, the first perturbation patch being located at one corner of the first square ring resonator and connected to the first square ring resonator, the second perturbation patch being located at one corner of the second square ring resonator and connected to the second square ring resonator, and the direction in which the first perturbation patch is located on the first square ring resonator is the same as the direction in which the second perturbation patch is located on the second square ring resonator.

4. A dual bandpass filter according to claim 3 wherein the first perturbation patch and the second perturbation patch are both rectangular microstrip patches.

5. The dual bandpass filter according to claim 2, wherein the second square-ring resonator comprises a closed-loop square microstrip line, each of four corners of the closed-loop square microstrip line has an opening, each opening is located in an inner direction of the closed-loop square microstrip line and is connected with an arrow structure, the arrow structure comprises two microstrip lines with equal length, an included angle between the two microstrip lines is 90 degrees, and an angle direction of the arrow structure is consistent with an outer edge of the corner of the closed-loop square microstrip line.

6. A dual bandpass filter according to claim 1 wherein the input and output feed lines are of identical construction and size and are at 90 degrees to each other.

7. A dual bandpass filter according to claim 1, wherein the coplanar waveguide feed lines comprise 2 first slot lines, 2 second slot lines, 2 third slot lines, 2 fourth slot lines, 2 fifth slot lines, 2 sixth slot lines, 2 seventh slot lines and 1 eighth slot line; the 2 first groove lines are vertically parallel, the 2 second groove lines are respectively and vertically connected with the 2 first groove lines and are opposite in direction, the 2 third groove lines are respectively and vertically connected with the 2 second groove lines and are vertically parallel in direction, the 2 fourth groove lines are respectively and vertically connected with the 2 third groove lines and are horizontal in direction, the 2 fifth groove lines are respectively and vertically connected with the 2 fourth groove lines and are vertically parallel in direction, and the 2 sixth groove lines are respectively and vertically connected with the 2 fifth groove lines and are horizontal in direction; 2 seventh slotlines link to each other with 2 sixth slotlines are perpendicular respectively and the direction is vertical parallel, and 2 seventh slotlines and direction level are connected respectively to the both ends of 1 eighth slotline.

8. A dual bandpass filter as recited in claim 1, wherein the dielectric substrate is of rocky 4350 dielectric material.

9. A dual bandpass filter as recited in claim 8, wherein said rockwell 4350 dielectric material has a relative permittivity of 3.66.