A square ring extremely narrow band band-pass filter thin film circuit

Abstract

The application discloses a square ring extremely narrow band pass filter thin film circuit, and relates to the technical field of microstrip filter thin film circuits.The circuit comprises a dielectric substrate, a signal input end, a signal output end and a square ring resonator array arranged on the front surface area of the dielectric substrate.The square ring resonator array comprises a plurality of square ring resonators arranged in an array form.Gaps exist between adjacent square ring resonators.The signal input end is directly connected with a square ring resonator at the head of the square ring resonator array, and the signal output end is directly connected with a square ring resonator at the tail of the square ring resonator array.A ground metal layer is arranged on the back surface area of the dielectric substrate.The square ring resonator is connected with the ground metal layer through a metal through hole.The application can effectively improve the out-of-band rejection capability, and the coupling distance, i.e., the gap width, is smaller due to the reduction of the coupling interval, so that the overall performance is more superior.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microstrip filter thin film circuit, and particularly relates to a square ring extremely narrow band bandpass filter thin film circuit. BACKGROUND

[0002] With the rapid development of wireless communication technology, the frequency resources available to human beings are less and less, so the design requirements of passive electronic devices are higher and higher, and it is very meaningful to study the microstrip filter thin film circuit with high frequency selectivity, which not only requires good in-band performance, but also requires higher out-of-band performance. The in-band performance requires low insertion loss, and the out-of-band performance requires steep passband cutoff edge and certain harmonic suppression function. The traditional microstrip filter thin film circuit has the advantages of small size and light weight, and has been widely used.

[0003] The traditional microstrip interdigital filter thin film circuit has simple structure and convenient design, and the passband range is mostly between 10% and 40%. However, due to the limitation of the line gap width, the coupling coefficient is difficult to meet the requirement of narrow band, and the size is greatly increased. It is difficult to achieve the requirement of narrow passband (below 5%), and the out-of-band suppression is poor due to the lack of transmission zero point. Therefore, it is of certain research significance to improve the structure to achieve the performance of narrow band filter thin film circuit without increasing the size as much as possible. SUMMARY

[0004] The purpose of the present application is to provide a square ring extremely narrow band bandpass filter thin film circuit, which can realize one transmission zero point in the low-end stop band and one transmission zero point in the high-end stop band, effectively improve the out-of-band suppression capability, and realize smaller coupling distance (i.e. gap width) due to the reduction of coupling interval, so that the overall performance is more superior.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] A square ring extremely narrow band bandpass filter thin film circuit, comprising: a dielectric substrate, and a signal input end, a signal output end and a square ring resonator array arranged on the front surface region of the dielectric substrate;

[0007] The square ring resonator array comprises a plurality of square ring resonators arranged in an array form; wherein there is a gap between adjacent square ring resonators;

[0008] The square ring resonator array is arranged between the signal input end and the signal output end; the signal input end is directly connected with the square ring resonator at the head of the square ring resonator array, and the signal output end is directly connected with the square ring resonator at the tail of the square ring resonator array;

[0009] The back area of the medium substrate is provided with a ground metal layer; the medium substrate is provided with a plurality of metal through holes; and the square ring resonator is connected with the ground metal layer through the metal through holes.

[0010] Optionally, the square ring resonator is a resonator formed by bending a traditional interdigital resonator into a square ring structure.

[0011] Optionally, the square ring resonator is a lambda g / 4 resonator.

[0012] Wherein, the wavelength λ0 is the wavelength corresponding to the center frequency in free space, epsilon re is the effective dielectric constant of the medium substrate, epsilon r is the relative dielectric constant of the medium substrate, and h is the thickness of the medium substrate, and w is the line width of the microstrip line.

[0013] Optionally, the number of the metal through holes is the same as the number of the square ring resonators, and one metal through hole is matched with one square ring resonator.

[0014] Optionally, the metal through hole is located in the interior of the square ring resonator, and the metal through hole is connected with one end of the square ring resonator; and the one end of the square ring resonator is the inwardly bent end.

[0015] Optionally, the medium substrate is a ceramic substrate; the relative dielectric constant epsilon r of the medium substrate is 9.8, and the thickness h is 0.254 mm.

[0016] Optionally, the signal input end and the signal output end are both 50 ohm microstrip lines.

[0017] Optionally, the parameters of the square ring extremely narrow band bandpass filter thin film circuit are as follows: the center frequency is 12.7 GHz, the working bandwidth is 12.5-12.9 GHz, and the relative bandwidth is 3%.

[0018] According to the specific embodiments of the present application, the following technical effects are achieved:

[0019] The square ring resonators in the present application are arranged in a certain rule, and the design is convenient; by adjusting the size of the square ring resonator, the extremely small coupling coefficient is achieved under the premise of the line seam width, and the design requirement of the extremely narrow band bandpass filter thin film circuit is achieved; compared with the traditional interdigital filter thin film circuit, the gap is greatly reduced, and the miniaturization purpose is achieved. The present application has high universality, meets the high frequency selectivity, and can flexibly adjust the center frequency of the square ring resonator and the line seam width according to the working bandwidth, so as to meet the requirement. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0021] Figure 1 A top view of the thin film circuit for square ring ultra-narrow band band-pass filtering provided by the embodiment of the present application;

[0022] Figure 2 A perspective view of the thin film circuit for square ring ultra-narrow band band-pass filtering provided by the embodiment of the present application;

[0023] Figure 3 A physical diagram of the thin film circuit for square ring ultra-narrow band band-pass filtering provided by the embodiment of the present application;

[0024] Figure 4 A simulation performance diagram of the thin film circuit for square ring ultra-narrow band band-pass filtering provided by the embodiment of the present application;

[0025] Figure 5 A measured performance diagram of the thin film circuit for square ring ultra-narrow band band-pass filtering provided by the embodiment of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments only constitute some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0028] As shown in Figure 1 , Figure 2 and Figure 3 , the thin film circuit for square ring ultra-narrow band band-pass filtering provided by the embodiment includes a dielectric substrate 102, a signal input end (also referred to as an input feed line) 101, a signal output end (also referred to as an output feed line) 105 and a square ring resonator array arranged on the front surface area of the dielectric substrate 102.

[0029] The square loop resonator array comprises a plurality of square loop resonators 103 arranged in an array form; wherein there is a gap between adjacent square loop resonators 103. The square loop resonator array is arranged between the signal input end 101 and the signal output end 105; the signal input end 101 is directly connected with the square loop resonator at the head of the square loop resonator array, and the signal output end 105 is directly connected with the square loop resonator at the tail of the square loop resonator array.

[0030] Preferably, the square loop resonator array has ten square loop resonators 103 arranged in a column, wherein the left five square loop resonators 103 can be mirror-symmetric to the right. The signal input end 101 is coupled with the first square loop resonator 103 by direct connection.

[0031] The back surface area of the dielectric substrate 102 is provided with a ground metal layer; the dielectric substrate 102 is provided with a plurality of metal vias 104; the square loop resonator 103 is connected with the ground metal layer through the metal via 104.

[0032] In the embodiment, the square loop resonator 103 is a resonator formed by bending the traditional interdigital resonator into a square loop structure, realizes new coupling characteristics to achieve a smaller coupling coefficient. The square loop resonator 103 is a λ g / 4 resonator, wherein the wavelength λ0 is the wavelength corresponding to the center frequency in free space, ε re is the effective dielectric constant of the dielectric substrate, ε r is the relative dielectric constant of the dielectric substrate, and h is the thickness of the dielectric substrate, and w is the line width of the microstrip line.

[0033] In the embodiment, the number of the metal vias 104 is the same as the number of the square loop resonators 103, and one metal via 104 is matched with one square loop resonator 103.

[0034] The metal via 104 is located inside the square loop resonator 103, and the metal via 104 is connected with one end of the square loop resonator 103; the one end of the square loop resonator 103 is the inwardly bent end.

[0035] In the embodiment, the dielectric substrate is a ceramic substrate; the relative dielectric constant ε r= 9.8, thickness h = 0.254 mm. Preferably, the medium substrate can be other materials with higher dielectric constant, further reducing the size, and the material can be quartz glass wafer, aluminum oxide ceramic substrate, aluminum nitride ceramic substrate, silicon carbide wafer, and boron nitride wafer, etc.

[0036] In this embodiment, the signal input end 101 and the signal output end 105 are both 50Ω microstrip lines.

[0037] The embodiment also provides a determination method of the square ring ultra-narrow band bandpass filter thin film circuit, including the following steps.

[0038] Step one: simulate the center frequency of a single square ring resonator to determine its size.

[0039] Step two: simulate the respective resonant frequencies f1, f2 of adjacent square ring resonators, and determine the coupling coefficient through to determine the size of the middle gap.

[0040] Step three: simulate the square ring resonator connected to the input end, calculate the time delay through the external Q value, and determine the connection position.

[0041] Step four: fine-tune the gap size to make the return loss meet the design requirements.

[0042] Based on the above method, a microstrip line filter thin film circuit with a working bandwidth of about 12.5-12.9GHz, a center frequency of 12.7GHz, and a relative bandwidth of about 3% is designed. After simulation optimization, the square ring ultra-narrow band bandpass filter thin film circuit is determined, and the performance of the final physical product can meet the design requirements of the ultra-narrow band.

[0043] The square ring ultra-narrow band bandpass filter thin film circuit provided in this embodiment is applied to the wireless communication system, has a working bandwidth of about 12.5-12.9GHz, a center frequency of 12.7GHz, and a relative bandwidth of about 3%. Figure 4 As shown in the S parameter performance simulation diagram of the square ring ultra-narrow band bandpass filter thin film circuit, Figure 4 the insertion loss of the square ring ultra-narrow band bandpass filter thin film circuit in the working bandwidth is about -5dB, and the return loss can meet less than -18dB, Figure 5 the S parameter performance test diagram of the square ring ultra-narrow band bandpass filter thin film circuit is basically the same as the simulation performance, so it is considered that the embodiment is feasible.

[0044] Each embodiment in the specification is described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same and similar parts between each embodiment can be referred to each other.

[0045] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the art, the specific implementation manners and application ranges will be changed according to the idea of the present application. In conclusion, the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A thin-film circuit for a square ring ultra-narrow bandpass filter, characterized in that, include: A dielectric substrate and a signal input terminal, a signal output terminal, and a square ring resonator array disposed on the front surface area of ​​the dielectric substrate; The square ring resonator array includes multiple square ring resonators arranged in an array configuration; wherein, there are gaps between adjacent square ring resonators. The square ring resonator array is disposed between the signal input terminal and the signal output terminal; the signal input terminal is directly connected to the square ring resonator located at the beginning of the square ring resonator array, and the signal output terminal is directly connected to the square ring resonator located at the end of the square ring resonator array. A ground metal layer is disposed on the back side of the dielectric substrate; the dielectric substrate has a plurality of metal vias; the square ring resonator is connected to the ground metal layer through the metal vias; The square ring resonator is a resonator with a square ring structure formed by bending on the basis of a traditional interdigital resonator; the metal through hole is located inside the square ring resonator and is connected to one end of the square ring resonator; one end of the square ring resonator is the end that is bent inward.

2. The thin-film circuit for a square ring ultra-narrow bandpass filter according to claim 1, characterized in that, The square ring resonator is λ. g / 4 resonator; Among them, wavelength λ0 is the wavelength corresponding to the center frequency in free space, and ε re The effective dielectric constant of the dielectric substrate, , ε r denoted as ρ, where h is the relative permittivity of the dielectric substrate, h is the thickness of the dielectric substrate, and w is the microstrip linewidth.

3. The thin-film circuit for a square ring ultra-narrow bandpass filter according to claim 1, characterized in that, The number of metal vias is the same as the number of square ring resonators, and each metal via is paired with only one square ring resonator.

4. A thin-film circuit for a square ring ultra-narrow bandpass filter according to claim 1, characterized in that, The dielectric substrate is a ceramic substrate; the relative permittivity ε of the dielectric substrate r =9.8, thickness h=0.254mm.

5. A thin-film circuit for a square ring ultra-narrow bandpass filter according to claim 1, characterized in that, Both the signal input terminal and the signal output terminal are 50Ω microstrip lines.

6. A thin-film circuit for a square ring ultra-narrow bandpass filter according to claim 1, characterized in that, The parameters of the thin-film circuit for the square ring ultra-narrow bandpass filter are: center frequency of 12.7 GHz, operating bandwidth of 12.5 to 12.9 GHz, and relative bandwidth of 3%.

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