CN111276779B - Microstrip low-pass filter - Google Patents
Microstrip low-pass filter Download PDFInfo
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- CN111276779B CN111276779B CN202010103756.4A CN202010103756A CN111276779B CN 111276779 B CN111276779 B CN 111276779B CN 202010103756 A CN202010103756 A CN 202010103756A CN 111276779 B CN111276779 B CN 111276779B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/201—Filters for transverse electromagnetic waves
- H01P1/203—Strip line filters
- H01P1/20327—Electromagnetic interstage coupling
- H01P1/20336—Comb or interdigital filters
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P1/00—Auxiliary devices
- H01P1/20—Frequency-selective devices, e.g. filters
- H01P1/212—Frequency-selective devices, e.g. filters suppressing or attenuating harmonic frequencies
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Abstract
The invention discloses a microstrip low-pass filter, which comprises: the dielectric substrate comprises a first surface and a second surface which are arranged oppositely, and a metal grounding plate is arranged on the first surface; a stepped impedance structure disposed on the second surface; a plurality of impedance step resonators disposed on the second surface and connected to the impedance step structure; and the microstrip interdigital structure is arranged on the second surface and formed by extending from the plurality of step impedance resonators. The invention adopts the improved step impedance resonator and introduces the microstrip interdigital coupling structure between the step impedance resonators, so that the microstrip low-pass filter has very small circuit size, good passband characteristic and wider stopband bandwidth.
Description
Technical Field
The invention belongs to the technical field of mobile communication, particularly relates to the field of filters, and particularly relates to a microstrip low-pass filter.
Background
The microstrip low-pass filter is one of the important components of a filter, is mainly used at the front stage of a transmitting end or the rear stage of a receiving end of a wireless communication system, and is used for filtering out a required low-frequency-band signal and inhibiting a high-frequency-band signal. Therefore, the high-performance low-pass filter can not only effectively reduce the size of the system, but also simplify the complexity of the integration of the communication system, thereby further realizing the low-cost, high-performance and miniaturized design of the wireless communication system. In recent years, with the rapid development of fifth generation mobile communication technology, higher demands have been made on good operation performance and smaller volume of wireless communication devices. The working performance of the wireless communication system is directly affected by the working performance of the filter, so that a miniaturized and high-performance low-pass filter becomes a research hotspot of broad researchers.
In 2007, Atallah Balalem, AliR. Ali, Jan Machac, Abbas Omar published in IEEE Microwave and Wireless Components Letters (Volume:17, Issue:8, Aug.2007) "Quasi-elastic micro trigger Low-Pass Filters Using an inter digital DGS Slot", and a design method of a Low Pass filter with a defect structure is proposed, and the resonant frequency of a Slot can be easily controlled by changing the length of an Interdigital structure. The defected ground structure is widely applied to high-performance miniaturization design of passive elements, and can be used for designing miniaturized low-pass filters. However, this structure is also insufficient in terms of stopband roll-off and cell structure size, resulting in non-ideal passband characteristics and circuit size.
In 2017, "Compact ultra-wide band stop and low pass filter using transformed stepped impedance resonator" was published in 2017 by Fan Zhang, Shuai Liu, Peng Zhao, Ming Du, Xiaochuan Zhang and Jun Xu in the national radio science conference of IEEE antenna and International seminar of propagation and USNC/URSI, and a subminiature microstrip low pass filter using transformed step impedance resonators was proposed, which realizes miniaturization of low pass filter. However, the-20 dB rejection bandwidth of the filter with the structure is narrow, and the out-of-band rejection effect is poor.
In summary, the following technical problems also exist in the prior art: the microstrip low-pass filter has too low out-of-band rejection performance and too large volume, and cannot ensure good in-band transmission performance.
Disclosure of Invention
The invention mainly aims to provide a microstrip low-pass filter, and aims to solve the technical problems that the microstrip low-pass filter in the prior art has low out-of-band rejection performance and large volume, and cannot ensure good in-band transmission performance.
In order to achieve the above object, the present invention provides a microstrip low pass filter, including: the dielectric substrate comprises a first surface and a second surface which are arranged oppositely, and a metal grounding plate is arranged on the first surface; a stepped impedance structure disposed on the second surface; a plurality of impedance step resonators disposed on the second surface and connected to the impedance step structure; and the microstrip interdigital structure is arranged on the second surface and formed by extending from the plurality of step impedance resonators.
Further, the stepped impedance structure comprises: and two ends of the transmission line are respectively connected with an input port feeder and an output port feeder.
Further, the input port feed line and the output port feed line are centrosymmetric about a midpoint of the transmission line, and the input port feed line and the output port feed line are axisymmetric about a centerline passing through the midpoint.
Further, the plurality of step-impedance resonators includes at least: a first stepped impedance resonator connected to the input port feed line; a second stepped-impedance resonator connected to the transmission line; the third step impedance resonator is connected with the output port feeder line; wherein the second stepped impedance resonator is located between the first and third stepped impedance resonators.
Further, the sizes of the first step-impedance resonator, the second step-impedance resonator and the third step-impedance resonator are different.
Further, the microstrip interdigital structure comprises: a first stub extending from the first stepped-impedance resonator to the second stepped-impedance resonator; a second stub connected to the second stepped-impedance resonator and extending toward the first stepped-impedance resonator; a third leg connected to and extending toward the second transimpedance resonator; a fourth leg connected to the third transimpedance resonator and extending toward the second transimpedance resonator.
Further, the first step-impedance resonator comprises a first transmission line and a second transmission line, two ends of the first transmission line are respectively connected with the input port feeder and the second transmission line, and the characteristic impedances of the first transmission line and the second transmission line are different; the second step-impedance resonator comprises a third transmission line and a fourth transmission line, two ends of the third transmission line are respectively connected with the middle position of the transmission line and the fourth transmission line, and the characteristic impedances of the third transmission line and the fourth transmission line are different; the third step-impedance resonator comprises a fifth transmission line and a sixth transmission line, two ends of the fifth transmission line are respectively connected with the output port feeder line and the sixth transmission line, and the characteristic impedances of the fifth transmission line and the sixth transmission line are different; the first transmission line, the third transmission line and the fifth transmission line are arranged in parallel, and the third transmission line is vertically connected with the transmission lines.
Furthermore, the first branch is formed by extending from the first transmission line to the third transmission line, and the first branch is vertically connected with the first transmission line; the second branch is formed by extending from the third transmission line to the first transmission line, and the second branch is vertically connected with the third transmission line; the third branch is formed by extending from the third transmission line to the fifth transmission line, and the third branch is vertically connected with the third transmission line; the fourth branch is formed by extending from the fifth transmission line to the third transmission line, and the fourth branch is vertically connected with the fifth transmission line; in the direction in which the first transmission line, the third transmission line and the fifth transmission line are parallel to each other, the projections of the first branch and the second branch are at least partially overlapped, and the projections of the third branch and the fourth branch are at least partially overlapped.
Furthermore, the shapes of the first branch, the second branch, the third branch and the fourth branch are the same.
Furthermore, the dielectric substrate is rectangular, the input end of the input port feeder is located at the midpoint of one of the short sides of the rectangular dielectric substrate, and the output end of the output port feeder is located at the midpoint of the other short side of the rectangular dielectric substrate.
In the technical scheme of the invention, a metal grounding plate is arranged on the first surface of the dielectric substrate; set up on the second surface of medium base plate step impedance structure, a plurality of step impedance syntonizers and microstrip interdigital structure, it is a plurality of step impedance syntonizer with the step impedance structure is connected, the microstrip interdigital structure is from a plurality of step impedance syntonizer extends and forms, through adopting improved step impedance syntonizer, introducing the mode of microstrip interdigital structure, makes this application microstrip low pass filter have very little circuit size, good passband characteristic and wider stopband bandwidth.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic perspective view of a microstrip low-pass filter according to an embodiment of the present invention;
FIG. 2 is a schematic top view of FIG. 1;
FIG. 3 is an equivalent circuit diagram of the microstrip low pass filter of the present invention;
FIG. 4 is a schematic structural dimension diagram of a microstrip low-pass filter according to an embodiment of the present invention;
FIG. 5 is a simulation diagram of S11 and S21 parameters of the microstrip low-pass filter of the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are 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 at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
Referring to fig. 1-3, the present invention provides a microstrip low-pass filter 100, wherein the microstrip low-pass filter 100 includes: the dielectric substrate 10, the dielectric substrate 10 includes a first surface (not shown) and a second surface 12 which are oppositely arranged, and the first surface is provided with a metal grounding plate 20; a stepped impedance structure 30, said stepped impedance structure 30 being disposed on said second surface 12; a plurality of stepped-impedance resonators 40, a plurality of the stepped-impedance resonators 40 being disposed on the second surface 12 and connected to the stepped-impedance structure 30; a microstrip interdigital structure 50, wherein the microstrip interdigital structure 50 is disposed on the second surface 12 and formed by extending from the plurality of stepped impedance resonators 40.
In this embodiment, the dielectric substrate 10 is preferably rectangular, and in other embodiments, the dielectric substrate 10 may have various shapes, which is not limited in this embodiment; the relative dielectric constant of the dielectric substrate 10 is preferably 3, and the thickness is preferably 0.787mm, in other embodiments, the relative dielectric constant may be the same value, and the thickness may also be other thicknesses, which is not limited in this embodiment. The dielectric substrate 10 is a flat plate, the dielectric substrate 10 includes a first surface and a second surface 12 that are opposite to each other, wherein a metal ground plate 20 is attached to the first surface, and the stepped impedance structure 30, the plurality of stepped impedance resonators 40, and the microstrip interdigital structure 50 are attached to the second surface 12, and the dielectric substrate 10 is a rectangular dielectric substrate 10 for example.
Referring to fig. 2, further, the stepped impedance structure 30 includes: and the transmission line 31, wherein an input port feeder 32 and an output port feeder 33 are respectively connected to two ends of the transmission line 31.
In this embodiment, the transmission line 31 is a high-impedance transmission line 31, the transmission line 31 extends along the length direction of the dielectric substrate 10 and is parallel to the long side of the rectangular dielectric substrate 10, the input port feed line 32 and the output port feed line 33 are respectively located at two ends of the transmission line 31, and in other embodiments, when the dielectric substrate 10 is not rectangular, the transmission line 31 may extend along any direction; specifically, the input port feeder 32 is a 50 ohm microstrip conduction band, the input end of the input port feeder 32 is located at the midpoint of one short side of the rectangular dielectric substrate 10, and the output end of the output port feeder 33 is located at the midpoint of the other short side of the rectangular dielectric substrate 10, so that the area on the second surface 12 can be reasonably utilized, and the miniaturization of the stepped impedance structure 30 is facilitated. Meanwhile, the step impedance structure 30 not only can reduce the electrical length of the resonator, but also can not reduce the no-load Q value, and can effectively improve the performance of the microstrip low-pass filter 100.
Referring to fig. 2, further, the input port feed line 32 and the output port feed line 33 are centrosymmetric with respect to a midpoint of the transmission line 31, and the input port feed line 32 and the output port feed line 33 are axisymmetric with respect to a center line passing through the midpoint.
In this embodiment, the input port feeder 32 and the output port feeder 33 are centrosymmetric with respect to a midpoint of the transmission line 31, that is, the input port feeder 32 and the output port feeder 33 are respectively located at two ends of the dielectric substrate 10 in the length direction, the input port feeder 32 is connected to one short side of the dielectric substrate 10, and the output port feeder 33 is connected to the other short side of the dielectric substrate 10; in addition, the input port feeder 32 and the output port feeder 33 are axisymmetric with respect to a center line passing through the center point, and there are two center lines passing through the center point of the transmission line 31, one of which is a center line of two short sides of the dielectric substrate 10, and the other is a center line of two long sides of the dielectric substrate 10, in fig. 2, when the input port feeder 32 and the output port feeder 33 are axisymmetric with respect to a center line of the short sides, that is, the input port feeder 32 itself is vertically symmetric, and at the same time, the output port feeder 33 itself is vertically symmetric; in fig. 2, when the input port feeder 32 and the output port feeder 33 are axisymmetric with respect to a long side center line, that is, the input port feeder 32 and the output port feeder 33 are bilaterally symmetric, which means that the input port feeder 32 and the output port feeder 33 are required to have the same shape and size, specifically, the input port feeder 32 and the output port feeder 33 are preferably square, in other embodiments, the stepped impedance structure 30 may also be another structure, and the position of the stepped impedance structure 30 on the second surface 12 may also be adaptively adjusted.
Referring to fig. 2, further, the plurality of stepped-impedance resonators 40 at least includes: a first stepped impedance resonator 41, the first stepped impedance resonator 41 being connected to the input port feed line 32; a second step-impedance resonator 42, the second step-impedance resonator 42 being connected to the transmission line 31; a third step-impedance resonator 43, the third step-impedance resonator 43 being connected to the output port feed line 33; wherein the second impedance-step resonator 42 is located between the first impedance-step resonator 41 and the third impedance-step resonator 43.
In this embodiment, the stepped-impedance resonators 40 are used to form transmission zeros in a resonant manner within the stop band, the number of the stepped-impedance resonators 40 can be selected according to the requirements of the stop band index, and in this embodiment, 3 stepped-impedance resonators 40, that is, the first stepped-impedance resonator 41, the second stepped-impedance resonator 42, and the third stepped-impedance resonator 43 are taken as an example for explanation; wherein the first stepped impedance resonator 41 is connected to the input port feed line 32, the second stepped impedance resonator 42 is connected to the transmission line 31, and the third stepped impedance resonator 43 is connected to the output port feed line 33, and since the input port feed line 32 and the output port feed line 33 are located at both ends of the transmission line 31, the second stepped impedance resonator 42 is located between the first stepped impedance resonator 41 and the third stepped impedance resonator 43 when the first stepped impedance resonator 41, the second stepped impedance resonator 42 and the third stepped impedance resonator 43 are located on the same side of the transmission line 31 (for example, on the upper side of the transmission line 31 shown in fig. 2), and further, the sizes of the first stepped impedance resonator 41, the second stepped impedance resonator 42 and the third stepped impedance resonator 43 are different from each other, thus, in the present embodiment, three stepped-impedance resonators 40 with different sizes and types are connected in parallel to the main transmission path, that is, the stepped-impedance structure 30, so that three transmission zeros can be generated outside the pass band, that is, inside the stop band, thereby widening the stop band range.
Referring to fig. 2-3, further, the microstrip interdigital structure 50 comprises: a first branch 51, the first branch 51 extending from the first stepped impedance resonator 41 to the second stepped impedance resonator 42; a second stub 52, the second stub 52 being connected to the second stepped-impedance resonator 42 and extending toward the first stepped-impedance resonator 41; a third branch 53, the third branch 53 being connected to the second transimpedance resonator 42 and extending toward the third transimpedance resonator 43; a fourth branch 54, the fourth branch 54 being connected to the third stepped-impedance resonator 43 and extending toward the second stepped-impedance resonator 42.
In this embodiment, a plurality of branches, such as the first branch 51, the second branch 52, the third branch 53, and the fourth branch 54, are used to generate coupling between adjacent impedance-stepped resonators 40, so as to form cross-coupling with the main transmission path, that is, the impedance-stepped structure 30, and the first branch 51, the second branch 52, the third branch 53, and the fourth branch 54 form a plurality of microstrip fingers in interleaving coupling on two sides of the second impedance-stepped resonator 42, that is, form the microstrip cross-finger structure 50; when the microstrip interdigital structure 50 is fed, a capacitive characteristic is provided by a coupling effect and an edge field effect between the microstrip fingers crossed by the microstrip interdigital structure 50 (as shown in fig. 3), and thus the microstrip interdigital structure 50 is also referred to as an interdigital capacitor. Because the microstrip interdigital structure 50 has a meandering structure, and the phase thereof exceeds the phase of the traditional microstrip line with the same length, the microstrip interdigital structure 50 can be applied to the design of the microstrip low-pass filter 100, thereby effectively reducing the area and achieving the purpose of miniaturization.
In this embodiment, since the second stepped impedance resonator 42 is located between the first stepped impedance resonator 41 and the third stepped impedance resonator 43, the first branch 51 extends from the first stepped impedance resonator 41 to the second stepped impedance resonator 42, that is, the first branch 51 is located between the first stepped impedance resonator 41 and the second stepped impedance resonator 42 and connected to the first stepped impedance resonator 41; the second stub 52 extends from the second stepped-impedance resonator 42 toward the first stepped-impedance resonator 41, that is, the second stub 52 is located between the first stepped-impedance resonator 41 and the second stepped-impedance resonator 42 and connected to the second stepped-impedance resonator 42; the third branch 53 extends from the second impedance-stepped resonator 42 to the third impedance-stepped resonator 43, that is, the third branch 53 is located between the second impedance-stepped resonator 42 and the third impedance-stepped resonator 43 and connected to the second impedance-stepped resonator 42; the fourth branch 54 extends from the third stepped impedance resonator 43 toward the second stepped impedance resonator 42, that is, the fourth branch 54 is located between the second stepped impedance resonator 42 and the third stepped impedance resonator 43 and connected to the third stepped impedance resonator 43.
Referring to fig. 2, further, the first step-impedance resonator 41 includes a first transmission line 411 and a second transmission line 412, two ends of the first transmission line 411 are respectively connected to the input port feed line 32 and the second transmission line 412, and the characteristic impedances of the first transmission line 411 and the second transmission line 412 are different; the second step-impedance resonator 42 includes a third transmission line 421 and a fourth transmission line 422, both ends of the third transmission line 421 are respectively connected to the middle position of the transmission line 31 and the fourth transmission line 422, and the characteristic impedances of the third transmission line 421 and the fourth transmission line 422 are different; the third step-impedance resonator 43 includes a fifth transmission line 431 and a sixth transmission line 432, the fifth transmission line 431 is connected to the output port feeder 33 and the sixth transmission line 432 at two ends thereof, respectively, and the characteristic impedances of the fifth transmission line 431 and the sixth transmission line 432 are different; the first transmission line 411, the third transmission line 421 and the fifth transmission line 431 are arranged in parallel, and the third transmission line 421 is vertically connected to the transmission line 31.
In this embodiment, two ends of the first transmission line 411 are respectively connected to the input port feeder 32 and the second transmission line 412, and the first transmission line 411 is vertically connected to the second transmission line 412; the two ends of the third transmission line 421 are respectively connected to the middle position of the transmission line 31 and the fourth transmission line 422, and the third transmission line 421 is vertically connected to the fourth transmission line 422; the two ends of the fifth transmission line 431 are respectively connected to the output port feeder 33 and the sixth transmission line 432, and the fifth transmission line 431 is vertically connected to the sixth transmission line 31; since the first, third and fifth transmission lines 411, 421 and 431 are disposed parallel to each other and the third transmission line 421 is connected perpendicular to the transmission line 31, the second, fourth and sixth transmission lines 412, 422, 432 and the transmission line 31 are also parallel to each other.
Referring to fig. 2, further, the first branch 51 extends from the first transmission line 411 to the third transmission line 421, and the first branch 51 is vertically connected to the first transmission line 411; the second branch 52 extends from the third transmission line 421 to the first transmission line 411, and the second branch 52 is vertically connected to the third transmission line 421; the third branch 53 extends from the third transmission line 421 to the fifth transmission line 431, and the third branch 53 is vertically connected to the third transmission line 421; the fourth branch 54 is formed by extending from the fifth transmission line 431 to the third transmission line 421, and the fourth branch 54 is vertically connected to the fifth transmission line 431; in the direction in which the first transmission line 411, the third transmission line 421 and the fifth transmission line 431 are parallel to each other, the projections of the first branch 51 and the second branch 52 are at least partially overlapped, and the projections of the third branch 53 and the fourth branch 54 are at least partially overlapped.
In this embodiment, the first branch 51 extends from the first transmission line 411 to the third transmission line 421, and the first branch 51 is vertically connected to the first transmission line 411; the second branch 52 extends from the third transmission line 421 to the first transmission line 411, and the second branch 52 is vertically connected to the third transmission line 421, so that the first branch 51 and the second branch 52 are overlapped, that is, in a direction (i.e., the up-down direction shown in fig. 2) in which the first transmission line 411 and the third transmission line 421 are parallel to each other, projections of the first branch 51 and the second branch 52 are at least partially overlapped; the third branch 53 extends from the third transmission line 421 to the fifth transmission line 431, and the third branch 53 is vertically connected to the third transmission line 421; the fourth branch 54 extends from the fifth transmission line 431 to the third transmission line 421, and the fourth branch 54 is vertically connected to the fifth transmission line 431, so that the third branch 53 and the fourth branch 54 are overlapped, that is, in a direction (that is, the up-down direction shown in fig. 2) in which the third transmission line 421 and the fifth transmission line 431 are parallel to each other, projections of the third branch 53 and the fourth branch 54 are at least partially overlapped. Further, the first, second, third and fourth branches 51, 52, 53 and 54 have the same shape and size, and are preferably rectangular, and in other embodiments, the number of branches may not be limited to four, or may be four or more, and the shapes and sizes of the branches may be different.
In addition, the microstrip low-pass filter 100 designed by the step impedance structure 30 and the microstrip interdigital structure 50 can be manufactured by etching the metal surface of the second surface 12 of the dielectric substrate 10 through a printed circuit board manufacturing process, so as to form a desired metal pattern.
In summary, in the technical solution of the present invention, a metal ground plate 20 is disposed on the first surface of the dielectric substrate 10; the step impedance structure 30, the plurality of step impedance resonators 40, and the microstrip interdigital structure 50 are disposed on the second surface 12 of the dielectric substrate 10, the plurality of step impedance resonators 40 are connected to the step impedance structure 30, the microstrip interdigital structure 50 is formed by extending from the plurality of step impedance resonators 40, and the microstrip low-pass filter 100 of the present invention has a very small circuit size, a good pass-band characteristic, and a wide stop-band bandwidth by adopting the improved step impedance resonators 40 and introducing the microstrip interdigital structure 50.
Referring to fig. 4, fig. 4 is a schematic structural dimension diagram of a microstrip low-pass filter 100 according to an embodiment of the present invention, where the dimension parameters of the microstrip low-pass filter 100 are as follows: w1＝2mm，W2＝3.5mm， W3＝1.5mm，W4＝3mm，W5＝2.2mm，W6＝1.75mm，W7＝11mm，W8＝0.5mm， L1＝5.1mm，L2＝1.95mm，L3＝2.35mm，L4＝0.55mm，L5＝1.95mm，L6＝3mm， L7＝0.55mm，L8＝1.45mm，Y1＝2mm，Y2＝0.6mm，Y3＝0.5mm，Y4＝1.5mm， Y51.5 mm. The overall area of the microstrip low-pass filter 100 is 15mm × 12.2mm, the corresponding guided wave length dimension is 0.39 λ g × 0.32 λ g, where λ g is the guided wave wavelength corresponding to the cutoff frequency, and as can be seen from the above dimensions, the microstrip low-pass filter 100 has a microstrip structureThe low-pass filter 100 has the advantage of better miniaturization.
Referring to fig. 5, the microstrip low-pass filter 100 is modeled by simulation in the electromagnetic simulation software hfss.17. Fig. 5 is a simulation diagram of S-parameter of the microstrip low-pass filter 100, and it can be seen from fig. 5 that the cutoff frequency of the microstrip low-pass filter 100 is 4.6GHz, the in-band insertion loss is less than 0.1dB in the pass band from dc to 3.79GHz, thereby achieving very excellent in-band transmission performance, and further, the frequency bandwidth with insertion loss outside the pass band of more than 20dB is in the range of 5.26GHz to 10.13GHz, so that the microstrip low-pass filter 100 has the characteristic of suppressing 2.2 th harmonic corresponding to this standard, and the microstrip low-pass filter 100 proposed by the present invention has a very small circuit size, good pass band characteristic, and wide stop band bandwidth.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (5)
1. A microstrip low pass filter, characterized in that it comprises:
the dielectric substrate comprises a first surface and a second surface which are arranged oppositely, and a metal grounding plate is arranged on the first surface;
a stepped-impedance structure disposed on the second surface, the stepped-impedance structure comprising: the transmission line is rectangular, and the impedance of the transmission line is high impedance;
a plurality of impedance step resonators disposed on the second surface and connected to the impedance step structure;
the microstrip interdigital structure is arranged on the second surface and formed by extending from the step impedance resonators;
wherein the plurality of stepped-impedance resonators includes at least:
a first stepped impedance resonator connected to the input port feed line;
a second stepped-impedance resonator connected to the transmission line;
the third step impedance resonator is connected with the output port feeder line;
the second impedance-stepping resonator is positioned between the first impedance-stepping resonator and the third impedance-stepping resonator, and the first impedance-stepping resonator, the second impedance-stepping resonator and the third impedance-stepping resonator are different in size;
the microstrip interdigital structure comprises:
a first stub extending from the first stepped-impedance resonator to the second stepped-impedance resonator;
a second stub connected to the second stepped-impedance resonator and extending toward the first stepped-impedance resonator;
a third leg connected to and extending toward the second transimpedance resonator;
a fourth leg connected to the third transimpedance resonator and extending toward the second transimpedance resonator;
the first step impedance resonator comprises a first transmission line and a second transmission line, wherein two ends of the first transmission line are respectively connected with the input port feeder line and the second transmission line, and the characteristic impedances of the first transmission line and the second transmission line are different;
the second step-impedance resonator comprises a third transmission line and a fourth transmission line, two ends of the third transmission line are respectively connected with the middle position of the transmission line and the fourth transmission line, and the characteristic impedances of the third transmission line and the fourth transmission line are different;
the third step-impedance resonator comprises a fifth transmission line and a sixth transmission line, two ends of the fifth transmission line are respectively connected with the output port feeder line and the sixth transmission line, and the characteristic impedances of the fifth transmission line and the sixth transmission line are different;
the first transmission line, the third transmission line and the fifth transmission line are arranged in parallel, and the third transmission line is vertically connected with the transmission lines;
the first branch is formed by extending from the first transmission line to the third transmission line, and the first branch is vertically connected with the first transmission line;
the second branch is formed by extending from the third transmission line to the first transmission line, and the second branch is vertically connected with the third transmission line;
the third branch is formed by extending from the third transmission line to the fifth transmission line, and the third branch is vertically connected with the third transmission line;
the fourth branch is formed by extending from the fifth transmission line to the third transmission line, and the fourth branch is vertically connected with the fifth transmission line;
in the direction in which the first transmission line, the third transmission line and the fifth transmission line are parallel to each other, the projections of the first branch and the second branch are at least partially overlapped, and the projections of the third branch and the fourth branch are at least partially overlapped.
2. The microstrip low pass filter according to claim 1,
the input port feed line and the output port feed line are centrosymmetric about a midpoint of the transmission line, and the input port feed line and the output port feed line are axisymmetric about a centerline passing through the midpoint.
3. The microstrip low pass filter according to claim 1, wherein the first step impedance resonator, the second step impedance resonator, and the third step impedance resonator are different in size.
4. The microstrip low pass filter according to any of claims 1 to 3 wherein the first, second, third and fourth stubs are all the same shape.
5. The microstrip low pass filter according to any of claims 1 to 3 wherein the dielectric substrate is rectangular, the input port feed line having its input end located at the midpoint of one of the short sides of the rectangular dielectric substrate and the output port feed line having its output end located at the midpoint of the other short side of the rectangular dielectric substrate.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010103756.4A CN111276779B (en) | 2020-02-19 | 2020-02-19 | Microstrip low-pass filter |
| PCT/CN2020/104450 WO2021164198A1 (en) | 2020-02-19 | 2020-07-24 | Microstrip low-pass filter |
Applications Claiming Priority (1)
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| CN111276779B (en) * | 2020-02-19 | 2021-11-26 | 中天宽带技术有限公司 | Microstrip low-pass filter |
| CN114530678B (en) * | 2022-02-25 | 2023-11-21 | 中天宽带技术有限公司 | Strip line combiner |
| CN114824700B (en) * | 2022-05-12 | 2024-06-25 | 洛阳中超新材料股份有限公司 | Filter and manufacturing method thereof |
| CN114824702B (en) * | 2022-05-13 | 2023-12-08 | 南京邮电大学 | Miniaturized ultra-wideband stop band plane band-pass filter |
| CN115117631B (en) * | 2022-06-15 | 2023-07-14 | 西安电子科技大学 | Horizontal polarization broadband filtering omnidirectional annular antenna |
| CN115051126B (en) * | 2022-06-23 | 2023-11-17 | 辽宁工程技术大学 | Four-notch ultra-wideband filter based on novel double open-loop resonators |
| CN115149229B (en) * | 2022-07-15 | 2024-02-20 | 华东交通大学 | Balanced filter |
| CN116613491B (en) * | 2023-07-18 | 2023-10-13 | 成都华兴汇明科技有限公司 | Frequency-selecting network with three transmission zero points and microwave oscillator constructed by same |
| CN117913486B (en) * | 2024-03-19 | 2024-05-28 | 微网优联科技(成都)有限公司 | Low-insertion-loss low-cost multi-zero miniaturized microstrip filter |
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| CN111276779A (en) | 2020-06-12 |
| WO2021164198A1 (en) | 2021-08-26 |
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