CN210866432U

CN210866432U - Microstrip line band-pass filter

Info

Publication number: CN210866432U
Application number: CN201921460108.3U
Authority: CN
Inventors: 李秀山; 肖倩; 黎燕林; 朱建华; 旃强; 王智会
Original assignee: Shenzhen Zhenhua Ferrite and Ceramic Electronics Co Ltd
Current assignee: Shenzhen Zhenhua Ferrite and Ceramic Electronics Co Ltd
Priority date: 2019-09-03
Filing date: 2019-09-03
Publication date: 2020-06-26
Anticipated expiration: 2029-09-03

Abstract

The utility model provides a microstrip line band pass filter, including ceramic substrate, five rank syntonizers, first feeder interface and second feeder interface, each syntonizer comprises the microstrip line, and five rank syntonizers include the first syntonizers, second syntonizers, third syntonizers, fourth syntonizers and the fifth syntonizer that set gradually along ceramic substrate length direction, and first syntonizer, second syntonizer, third syntonizer, fourth syntonizer are the pectination structure, and the third syntonizer comprises half wavelength's U-shaped microstrip line. Through making middle third syntonizer constitute by half wavelength's U type microstrip line, reduce parasitic inductance in the through-hole to the influence of microstrip line filter to improve the effect of wave filter low frequency upwarp, high frequency upwarp down, make the low frequency section rectangular coefficient of stop band obtain improving, reduce fluctuation in the through-hole and high frequency department insertion loss, simultaneously, all the other four syntonizers are the pectination structure, and the structure is compacter, in order to dwindle the volume of this wave filter.

Description

Microstrip line band-pass filter

Technical Field

The utility model relates to a technical field of wave filter especially provides a microstrip line band pass filter.

Background

With the rapid development of wireless communication, the division between channels becomes finer and finer, and the microwave filter used for separating useful and useless signals becomes an important element in the communication system, and the quality of the performance directly affects the quality of the whole communication system. At present, microwave filters have been widely used in various fields such as microwave communication, microwave guidance, navigation, telemetry, remote control, satellite communication, and military electronic countermeasure, and the requirements for microwave filters are increasing. The existing microstrip line filter types include hairpin type, comb type, interdigital type, parallel coupling type and the like. The parallel coupling type filter has larger size when the order of the filter is the same, and the hairpin type microstrip line filter is a filter improved on the basis of the parallel coupling type filter and still has the defect of larger volume. The comb line and the interdigital filter have the advantage of small volume, but are influenced by parasitic inductance of a grounding hole, the phenomena of low-frequency upwarping and high-frequency downwarping are presented, and the defects of low-frequency rectangular coefficient difference in a stop band, high insertion loss on one side of high frequency in a pass band and large in-band fluctuation exist.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a microstrip line band pass filter aims at solving the technical problem that microstrip line band pass filter among the prior art is bulky, insertion loss is high and the in-band is undulant big.

In order to achieve the above object, the utility model adopts the following technical scheme: the microstrip line band-pass filter comprises a ceramic substrate, five-order resonators arranged on the ceramic substrate, a first feeder line interface and a second feeder line interface, wherein the first feeder line interface and the second feeder line interface are respectively arranged at two ends of the ceramic substrate, each resonator is composed of a microstrip line, the five-order resonators comprise a first resonator, a second resonator, a third resonator, a fourth resonator and a fifth resonator which are sequentially arranged along the length direction of the ceramic substrate, one end of the first resonator is connected with the first feeder line interface, one end of the fifth resonator is connected with the second feeder line interface, the first resonator, the second resonator, the third resonator and the fourth resonator are all of a comb-shaped structure, and the third resonator is composed of a half-wavelength U-shaped microstrip line.

Further, the third resonator comprises a first section and a second section which are arranged in a manner of extending from the width direction of the ceramic substrate, and a third section which extends along the length direction of the ceramic substrate, wherein the first section and the second section are positioned at two ends of the third section, and the first section and the second section are respectively connected with two ends of the third section.

Furthermore, a junction of the first section and the third section and a junction of the first section and the third section are respectively provided with a chamfer.

Further, the first resonator and the fifth resonator are symmetrically arranged around the third resonator, and the second resonator and the fourth resonator are arranged in mirror symmetry around the third resonator.

Furthermore, the first resonator comprises a first section extending along the length direction of the ceramic substrate and a second section bent from one end of the first section towards the second resonator, one end of the first feeder line interface is connected with the middle part of the first section, and the free end of the first section is grounded;

the fifth resonator comprises a third section extending along the length direction of the ceramic substrate and a fourth section bent towards the fourth resonator at one end of the third section, one end of the second feeder line interface is connected with the middle of the third section, and the free end of the third section is grounded.

Furthermore, a joint of the first section and the second section and a joint of the third section and the fourth section are respectively provided with a first round angle.

Furthermore, the ceramic substrate is provided with first through holes at positions corresponding to the free end of the first section and the free end of the third section, and the free end of the first section and the free end of the third section are connected with the ground through the corresponding first through holes respectively.

Furthermore, the second resonator comprises a first fold extending along the length direction of the ceramic substrate and a second fold arranged at one end of the first fold and bent towards the first resonator, and the free end of the first fold is grounded;

the fourth resonator comprises a third fold extending along the length direction of the ceramic substrate and a fourth fold bent and arranged at one end of the third fold towards the fifth resonator, and the free end of the third fold is grounded.

Furthermore, the ceramic substrate is provided with second through holes at positions corresponding to the free ends of the first fold and the third fold respectively, and the free ends of the first fold and the third fold are connected with the ground through the corresponding second through holes respectively.

Further, the ceramic substrate is an alumina ceramic plate with the thickness of 0.235 mm.

The utility model has the advantages that: compared with the prior art, the utility model discloses a microstrip line band pass filter, third syntonizer through among the five-order microstrip line filter comprises half wavelength's U type microstrip line, reduces parasitic inductance in the through-hole to microstrip line filter's influence, thereby improve the upwarp of wave filter low frequency, the effect of upwarp under the high frequency, make the low frequency section rectangular coefficient of stop band obtain improving, reduce the interior undulant and the high frequency insertion loss of department of passband, all the other four syntonizers are the pectination structure simultaneously, the structure is compacter, in order to reduce the volume of this wave filter.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments or the prior art descriptions will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive labor.

Fig. 1 is a schematic structural diagram of a microstrip line band-pass filter provided in an embodiment of the present invention;

fig. 2 is a schematic diagram of a simulation result of the microstrip line band-pass filter provided in the embodiment of the present invention;

fig. 3 is a schematic diagram showing a comparison of simulation results of the microstrip line band-pass filter and the five-order interdigital filter provided by the embodiment of the present invention.

Wherein, in the drawings, the reference numerals are mainly as follows:

10-microstrip line band pass filter; 11-a first resonator; 12-a second resonator; 13-a third resonator; 14-a fourth resonator; 15-a fifth resonator; 16-a first feeder interface; 17-a second feeder interface; 18-a first rounded corner; 19-a second rounded corner; 111-first stage; 112-a second segment; 121-first fold; 122-second folding; 131-first section; 132-second section; 133-third section; 134-chamfering; 141-third fold; 142-fourth fold; 151-third section; 152-fourth section;

20-a first via; 21-second via.

Detailed Description

In order to make the technical problem, technical solution and advantageous effects to be solved by the present invention more clearly understood, the following description is given in conjunction with the accompanying drawings and embodiments to illustrate the present invention in further detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

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. In the description of the present invention, "a plurality" means two or more unless specifically limited otherwise.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present invention can be understood according to specific situations by those skilled in the art.

Referring to fig. 1, a microstrip line band-pass filter provided by the present invention will now be described. The microstrip line band-pass filter 10 includes a ceramic substrate (not shown), a fifth-order resonator, a first feeder line interface 16 and a second feeder line interface 17, the first feeder line interface 16 is used for feeding in or feeding out an electromagnetic wave signal, the second feeder line interface 17 is used for feeding in or feeding out an electromagnetic wave signal, that is, the first feeder line interface 16 and the second feeder line interface 17 cooperate to form an electromagnetic wave signal output end and an electromagnetic wave signal input end of the microstrip line band-pass filter, the first feeder line interface 16 and the second feeder line interface 17 are respectively arranged on two sides of the ceramic substrate, and the fifth-order resonator is arranged on the ceramic substrate. Wherein, each resonator is composed of microstrip lines, the fifth order resonator includes a first resonator 11, a second resonator 12, a third resonator 13, a fourth resonator 14 and a fifth resonator 15, the first resonator 11, the second resonator 12, the third resonator 13, the fourth resonator 14 and the fifth resonator 15 are respectively arranged in sequence along the length direction of the ceramic substrate, one end of the first resonator 11 is connected with a first feeder interface 16, one end of the fifth resonator 15 is connected with a second feeder interface 17, so that the signal of the electromagnetic plate can flow into the first resonator 11, the second resonator 12, the third resonator 13, the fourth resonator 14 and the fifth resonator 15 through the first feeder interface 16 and then flow out through the second feeder interface 17, thereby realizing the filtering of the clutter on the electromagnetic wave and realizing the stability of signal transmission, wherein the width of each microstrip line is the same, the insertion loss in a pass band is reduced, stop band suppression is improved, and reliability is high; specifically, the first resonator 11, the second resonator 12, the third resonator 13, and the fourth resonator 14 are all comb-shaped structures, so that the structure is more compact, and the size of the resonators can be reduced, so that the filter 10 can be miniaturized; the third resonator 13 is composed of a half-wavelength U-shaped microstrip line, and thus, the half-wavelength microstrip line does not need a ground via, thereby reducing the influence of parasitic inductance in the via on the microstrip band-pass filter 10, further improving the low-frequency upwarp and high-frequency downwarp effects of the filter, improving the low-frequency band rectangular coefficient of the stop band, and reducing the insertion loss at the inner fluctuation and high frequency of the pass band. In addition, by providing five-order resonators on the ceramic substrate, four of the resonators are comb-shaped, which makes the structure more compact, and reduces the size of the resonators, thereby facilitating the miniaturization of the filter 10.

Further, referring to fig. 1, as an embodiment of the microstrip bandpass filter provided by the present invention, the third resonator 13 includes a first section 131, a second section 132 and a third section 133, wherein the first section 131 and the third section 133 are both disposed by extending in a width direction of the ceramic substrate, the third section 133 extends along a length direction of the ceramic substrate, the first section 131 and the third section 133 are disposed at two ends of the second section 132, lengths of the first section 131 and the third section 133 are equal, the first section 131 and the second section 132 are respectively connected to two ends of the third section 133, and the first section 131 and the second section 132 are respectively perpendicular to the third section 133. With the structure, the first section 131 and the second section 132 are symmetrically arranged, and the first section 131, the second section 132 and the third section 133 form a half-wavelength U-shaped structure, so that the influence of parasitic inductance in a grounding through hole on the ceramic baseplate on the microstrip band-pass filter 10 is reduced, the low-frequency upwarp and the high-frequency downwarp of the filter are improved, the low-frequency section rectangular coefficient of the stop band is improved, and the fluctuation in the passband and the insertion loss at the high frequency are reduced.

Further, please refer to fig. 1, as a specific embodiment of the microstrip line band pass filter provided by the present invention, a junction of the first section 131 and the third section 133 and a junction of the second section 132 and the third section 133 are respectively provided with a chamfer 134, and the first section 131 and the second section 132 are respectively perpendicular to the third section 133, so that the right-angle junctions between the microstrip lines constituting the pass band are connected by the chamfers 134, which can make the electromagnetic field transition smooth, reduce the electromagnetic radiation and the loss, thereby improving the performance of the filter.

Further, please refer to fig. 1, as a specific embodiment of the microstrip line band pass filter provided by the present invention, the first resonator 11 and the fifth resonator 15 are symmetrically disposed about the third resonator 13, and the second resonator 12 and the fourth resonator 14 are mirror-symmetrically disposed about the third resonator 13, it can be understood that the shapes and sizes of the first resonator 11 and the fifth resonator 15 are completely the same, correspondingly, the shapes of the second resonator 12 and the fourth resonator 14 are the same, so that the processing and the design are convenient, meanwhile, the symmetry of the resonators on both sides can be ensured, the insertion loss of the passband is reduced, and the adjustment and the range of the passband are convenient.

Further, please refer to fig. 1 together, as a specific embodiment of the microstrip line band pass filter provided by the present invention, the first resonator 11 includes a first section 111 and a second section 112, the first section 111 extends along the length direction of the ceramic substrate, and the second section 112 is bent toward the second resonator 12 at one end of the first section 111, wherein the first section 111 and the second section 112 are perpendicular to each other, that is, the first section 111 and the second section 112 form an L-shaped microstrip line, one end of the first feeder interface 16 is connected to the middle of the first section 111, the free end of the first section 111 is grounded, and the length of the microstrip line constituting the first resonator 11 is a quarter wavelength, so as to generate a transmission zero point on the passband. Correspondingly, the fifth resonator 15 includes a third fold 141 and a fourth fold 142, the third fold 141 extends along the length direction of the ceramic substrate, the fourth fold 142 is bent toward the fourth resonator 14 at one end of the third fold 141, and the free end of the third segment 151 is grounded, wherein the third fold 141 and the fourth fold 142 are perpendicular to each other, and the length of the microstrip line constituting the fifth resonator 15 is a quarter wavelength, so that a transmission zero point is generated on the passband, that is, two transmission zero points are generated on both sides of the filter, so that signals can cancel each other at some radio frequency points when being transmitted in each path, and the filter can obtain better filtered signals or harmonic suppression.

Further, please refer to fig. 1, as a specific embodiment of the microstrip line band pass filter provided by the present invention, the joint of the first section 111 and the second section 112 and the joint of the third section 151 and the fourth section 152 are respectively provided with the first fillet 18, that is, the corners of each microstrip line are provided with fillets, so that the electromagnetic field transition is smooth, the electromagnetic radiation is reduced, and the loss is reduced, thereby improving the performance of the filter. Preferably, the ceramic substrate is provided with first through holes 20 at positions corresponding to the free end of the first segment 111 and the free end of the third segment 151, respectively, and the free end of the first segment 111 and the free end of the third segment 151 are connected to the ground through the corresponding first through holes 20, respectively. By providing the first through hole 20 so as to ground the free end of the first end and the free end of the third segment 151. Preferably, the diameter of the first through hole 20 is 200um, and the through hole is filled with metal, so that the processing is convenient and the manufacturing is convenient.

Further, please refer to fig. 1, as a specific embodiment of the microstrip line band pass filter provided by the present invention, the second resonator 12 includes a first fold 121 and a second fold 122, the first fold 121 extends along the length direction of the ceramic substrate, the second fold 122 is bent at one end of the first fold 121 toward the second fold 122 of the first resonator 11, the free end of the second section 112 is grounded, wherein the length of the microstrip line constituting the second resonator 12 is a quarter wavelength, so that a transmission zero point is generated on the passband, so that the signals can be mutually offset at some radio frequency points during the transmission of each path. Preferably, the first fold 121 and the second fold 122 are arranged perpendicular to each other, that is, the first fold 121 and the second fold 122 form an L-shaped microstrip line, and the second segment 112 of the first resonator 11 and the second fold 122 of the second resonator 12 are parallel to each other and respectively located at two sides of the ceramic substrate, so that parallel coupling between the two microstrip lines is realized. The bending parts of the two microstrip lines are arranged in a staggered mode, so that the two microstrip lines are compact, and the filter is convenient to miniaturize. Correspondingly, the fourth resonator 14 includes a third fold 141 and a fourth fold 142, the third fold 141 extends along the length direction of the ceramic substrate, the fourth fold 142 is bent toward the fifth resonator 11 at one end of the third fold 141, and the free end of the third fold 141 is grounded, wherein the length of the microstrip line constituting the fourth resonator 14 is a quarter wavelength, which generates a transmission zero point on the passband, so that signals can cancel each other at some radio frequency points when being transmitted in each channel. Preferably, the third fold 141 and the fourth fold 142 are arranged perpendicular to each other, that is, the third fold 141 and the fourth fold 142 form an L-shaped microstrip line, and the fourth segment 152 of the fifth resonator 15 and the fourth fold 142 of the fourth resonator 14 are parallel to each other and respectively located on two sides of the ceramic substrate, so that parallel coupling between two passbands is realized. The bending parts of the two microstrip lines are arranged in a staggered mode, so that the two microstrip lines are compact, and the filter is convenient to miniaturize.

Further, please refer to fig. 1, as a specific implementation manner of the microstrip band pass filter provided by the present invention, the ceramic substrate is provided with a second through hole 21 at a position corresponding to the free end of the first fold 121 and the free end of the third fold 141, and the free end of the first fold 121 and the free end of the third fold 141 are connected to the ground through the corresponding second through hole 21. By providing a through hole to facilitate grounding of the free ends of the first and

third folds

121, 141. Preferably, the diameter of the through hole is 200um, and the through hole is filled with metal, so that the processing is convenient and the manufacturing is convenient. In order to reduce the electromagnetic radiation and loss of the filter, a second rounded corner 19 is provided at the junction of the first fold 121 and the second fold 122 and at the junction of the third fold 141 and the fourth fold 142, respectively.

Specifically, in the filter, a first feeder interface 16 is connected to the first resonator 11 for feeding in or feeding out an electromagnetic wave signal; the second feeder line interface 17 is connected to the fifth resonator 15, and is used for feeding in or feeding out an electromagnetic wave signal; the first feeder interface 16 is the same width as the second feeder interface 17; the first resonator 11, the second resonator 12, the third resonator 13, the fourth resonator 14 and the fifth resonator 15 are located between the first feeder interface 16 and the second feeder interface 17, the second resonator 12 is located between the first resonator 11 and the third resonator 13, the first resonator 11 is close to the first feeder interface 16, and the fifth resonator 15 is close to the second feeder interface 17; the fourth resonator 14 is between the third resonator 13 and the fifth resonator 15, and the third resonator 13 is between the second resonator 12 and the fourth resonator 14; the first resonator 11, the second resonator 12, the fourth resonator 14, and the fifth resonator 15 are all formed by quarter-wavelength microstrip lines, the third resonator 13 is formed by half-wavelength microstrip lines, and the third resonator 13 is in a U-shaped structure as a whole. The first resonator 11 is integrally in an L-shaped structure and comprises a first section 111 and a second section 112, the first section 111 and the second section 112 are perpendicular to each other, the second resonator 12 and the first resonator 11 are in a mirror symmetry structure and comprise a third section 151 and a fourth section 152, and the third section 151 and the fourth section 152 are perpendicular to each other; the third resonator 13 is a U-shaped structure as a whole, and is composed of a first section 131, a second section 132 and a third section 133, wherein the first section 131 and the second section 132 are parallel to each other and perpendicular to two ends of the third section 133 respectively; the second resonator 12 is integrally L-shaped and includes a first fold 121 and a second fold 122, the first fold 121 and the second fold 122 are perpendicular to each other, the fourth resonator 14 and the second resonator 12 are mirror-symmetric and include a third fold 141 and a fourth fold 142, the third fold 141 and the fourth fold 142 are perpendicular to each other, and the first section 111, the second section 112, the first fold 121, the second fold 122, the first section 131, the second section 132, the third section 133, the third fold 141, the fourth fold 142, the third section 151, and the fourth section 152 have the same width. With such a structure, the first feeder interface 16 feeds the first resonator 11, the second feeder interface 17 feeds the fifth resonator 15, the second resonator 12 is coupled with the first resonator 11 through the first fold 121, that is, the main coupling portions of the first resonator 11 and the second resonator 12 are the first segment 111 and the first fold 121, the main coupling portions of the second resonator 12 and the third resonator 13 are the portion where the first fold 121 coincides with the first segment 131, correspondingly, the fourth resonator 14 is coupled with the fifth resonator 15, the main coupling portions of the fourth resonator 14 and the fifth resonator 15 are the third fold 141 and the third segment 151, the main coupling portions of the third resonator 13 and the fourth resonator 14 are the portion where the second segment 132 coincides with the third fold 141, wherein each of the first resonator 11, the second resonator 12, the fourth resonator 14 and the fifth resonator 15 is composed of a microstrip line having a length approximately equal to a quarter wavelength, a plurality of transmission zeros are generated at the passband of the filter, so that signals can be mutually cancelled at some radio frequency points when being transmitted in each channel, and the filter can obtain better filtered signals or harmonic suppression.

Further, please refer to fig. 1 to fig. 3 together, as a specific embodiment of the microstrip line band pass filter provided by the present invention, the ceramic substrate is an alumina ceramic plate with a thickness of 0.235mm, so that the ceramic bottom plate has sufficient supporting strength, and the thickness of the ceramic bottom plate is still as small as possible, that is, the height of the through hole is as small as possible, so as to reduce the size and the in-band insertion loss of the filter, thereby reducing the influence of the parasitic inductance of the via hole on the filter.

The utility model provides a microstrip line band pass filter adopts photoetching corroded technology to make, at first makes the through-hole on ceramic substrate, adopts metal material such as copper or gold to pass through the pore-filling in the through-hole, then has plated one deck metal film respectively on two upper and lower surfaces of ceramic substrate, does to form each syntonizer, first feeder interface 16 and second feeder interface 17 at the upper surface of ceramic substrate through photoetching corrosion method after that.

Further, referring to fig. 1 to 3 together, as an embodiment of the microstrip band pass filter provided by the present invention, a width L0 of each microstrip line is equal, an L0 of each microstrip line is 0.2mmm, a length L1 of each of the first section 111 and the third section 151 is 1.72mm, a length L2 of each of the second section 112 and the fourth section 152 is 0.29mm, a length L3 of each of the first section 121 and the third section 141 is 1.68mm, a length L4 of each of the second section 122 and the fourth section 142 is 0.27mm, a length L5 of each of the first section 131 and the third section 133 is 1.82mm, a length L6 of the third section 133 is 0.6mm, a vertical height of the first feeder line interface 16 is the same as that of the first feeder line interface 16, a distance S1 between a center of the first feeder line interface 20 is 0.33mm, a distance between the first section 111 and the first section 121 is equal to a distance between the third section 151 and the first section 141, a distance between S1 and the third section 141 mm is equal to a distance between the third section 131 and the third section 132, the space S2 is 0.48mm, and the dielectric plate used for the microstrip line is an alumina ceramic plate with a thickness of 0.254 mm. To reduce bulk and in-band insertion loss. The first through hole 20 and the second through hole 21 have a diameter of 200um and are filled with metal. The utility model discloses use emulation software Advanced Design System (ADS) to simulate, figure 2 is the utility model provides a microstrip line band pass filter 10's simulation result picture and figure 3 do the utility model provides a microstrip line band pass filter 10 and five steps of zigzag filter's simulation result picture. Wherein, the horizontal axis represents the signal frequency of wave filter, and the vertical axis represents the range, including return loss S11 'S the range and insertion loss S21' S the range, S11 represents the utility model discloses return loss curve on the well each frequency, S21 represents the utility model discloses in the insertion loss curve on each frequency, correspondingly, S10 represents the return loss curve on each frequency in the five-order interdigital filter, S20 represents the insertion loss curve on each frequency in the five-order interdigital filter, can see from figure 2 and figure 3, the utility model discloses the wave filter is 12.2GHz-12.8GHz in the passband scope. The filter is greater than 55dB at 1.7GHz from the passband. The in-band standing wave ratio is better than 1.2, and the device has the advantages of good frequency selectivity, simple structure, convenient processing, compact volume and convenient PCB circuit integration.

The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.

Claims

1. A microstrip line band-pass filter comprises a ceramic substrate, five-order resonators arranged on the ceramic substrate, and a first feeder line interface and a second feeder line interface which are respectively arranged at two ends of the ceramic substrate, and is characterized in that each resonator consists of a microstrip line, the five-order resonators comprise a first resonator, a second resonator, a third resonator, a fourth resonator and a fifth resonator which are sequentially arranged along the length direction of the ceramic substrate, one end of the first resonator is connected with the first feeder line interface, one end of the fifth resonator is connected with the second feeder line interface, the first resonator, the second resonator, the third resonator and the fourth resonator are all of a comb-shaped structure, and the third resonator consists of a half-wavelength U-shaped microstrip line.

2. The microstrip band pass filter according to claim 1, wherein the third resonator includes a first section and a second section extending in a width direction of the ceramic substrate, and a third section extending in a length direction of the ceramic substrate, the first section and the second section are located at both ends of the third section, and the first section and the second section are connected to both ends of the third section, respectively.

3. The microstrip line bandpass filter according to claim 2, wherein a junction of the first section and the third section and a junction of the first section and the third section are respectively provided with a chamfer.

4. The microstrip bandpass filter of claim 1 wherein the first resonator and the fifth resonator are symmetrically disposed about the third resonator, and the second resonator and the fourth resonator are mirror symmetrically disposed about the third resonator.

5. The microstrip line bandpass filter according to claim 4, wherein the first resonator includes a first section extending along the length direction of the ceramic substrate and a second section bent at one end of the first section toward the second resonator, one end of the first feeder line interface is connected to the middle of the first section, and the free end of the first section is grounded;

6. The microstrip line bandpass filter of claim 5 wherein a junction of the first segment and the second segment and a junction of the third segment and the fourth segment are each provided with a first fillet.

7. The microstrip line bandpass filter according to claim 5, wherein the ceramic substrate is provided with first through holes at positions corresponding to the free end of the first section and the free end of the third section, respectively, and the free end of the first section and the free end of the third section are connected to the ground through the corresponding first through holes, respectively.

8. The microstrip band pass filter according to claim 4, wherein the second resonator includes a first fold extending in a length direction of the ceramic substrate and a second fold provided at one end of the first fold so as to be bent toward the first resonator, a free end of the first fold being grounded;

9. The microstrip band pass filter according to claim 8, wherein the ceramic substrate is provided with second through holes at positions corresponding to the free end of the first fold and the free end of the third fold, respectively, and the free end of the first fold and the free end of the third fold are connected to the ground through the second through holes, respectively.

10. The microstrip band pass filter according to any one of claims 1-9, wherein the ceramic substrate is an alumina ceramic plate having a thickness of 0.235 mm.