CN115528402A - Miniaturized thin film filter - Google Patents
Miniaturized thin film filter Download PDFInfo
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- CN115528402A CN115528402A CN202211240895.7A CN202211240895A CN115528402A CN 115528402 A CN115528402 A CN 115528402A CN 202211240895 A CN202211240895 A CN 202211240895A CN 115528402 A CN115528402 A CN 115528402A
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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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- 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
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Abstract
A miniaturized thin film filter comprises a dielectric substrate, wherein an I metal signal excitation port, an II metal signal excitation port and a resonator unit are formed on the front surface of the dielectric substrate through a thin film process, and a metal ground plane is arranged on the back surface of the dielectric substrate; the resonator unit is connected between the two excitation ports and is arranged in a centrosymmetric manner by taking the center of the dielectric substrate as a center; the resonator unit comprises a plurality of spaced resonator pairs, each resonator pair comprises two spaced quarter-wavelength metal resonators, one ends of the two quarter-wavelength metal resonators face different sides and are connected with a metal ground plane through via holes, the other ends of the two quarter-wavelength metal resonators are bent, and the bent sections are located between the two quarter-wavelength metal resonators. On the premise of not changing the coupling coefficient between the resonators, the width of the filter can be reduced by adjusting the shapes of the resonators, the performance indexes of the filter are basically unchanged, and different orders can be selected for design according to different indexes.
Description
Technical Field
The application belongs to the technical field of filters, and particularly relates to a miniaturized thin film filter applied to a radio frequency microwave circuit.
Background
The filter is one of the most common devices in the field of modern radio frequency microwave, and the filter is in a wide variety. The performance can be divided into a high-pass filter, a low-pass filter, a band-pass filter and a band-stop filter; according to the structural distinction, the filter can be divided into a cavity filter, a microstrip line filter, a strip line filter, an LTCC filter, an SAW filter and the like; different kinds of filters have different advantages and disadvantages. With the increasingly stringent requirements for device miniaturization in the modern radio frequency microwave field, miniaturization of filters as common devices faces an increasing challenge.
The thin film filter is one kind of microstrip filter, and has the advantages of low cost, easy integration, etc. Because the alumina substrate has higher dielectric constant, the thin film filter produced on the alumina substrate by a thin film process has the outstanding advantage of small volume, and is widely applied to radio frequency microwave system components.
Conventional interdigital and comb microstrip filters have a resonator length of approximately one quarter of a wavelength, and the width of the filter is determined when the frequency is selected. For a low-frequency filter, because the frequency is low and the wavelength is long, the width of the filter is often large, and therefore, on the basis, the research of a novel thin-film filter with small volume and high performance has very important significance.
Disclosure of Invention
In order to solve the defects of the prior art, the application provides a miniaturized thin film filter, on the premise of not changing the coupling coefficient between resonators, the width of the filter can be reduced by adjusting the shape of the quarter-wave resonator, the performance index of the filter is basically unchanged, and different orders can be selected for design according to different indexes.
In order to achieve the above object, the present invention employs the following techniques:
a miniaturized thin film filter comprises a dielectric substrate, wherein an I metal signal excitation port, an II metal signal excitation port and a resonator unit are formed on the front surface of the dielectric substrate through a thin film process, and a metal ground plane is arranged on the back surface of the dielectric substrate;
the resonator unit is positioned between the I metal signal excitation port and the II metal signal excitation port and is arranged in central symmetry with the center of the dielectric substrate;
the resonator unit comprises a plurality of resonator pairs arranged at intervals, each resonator pair comprises two quarter-wavelength metal resonators arranged at intervals, one ends of the two quarter-wavelength metal resonators face different sides and are connected with a metal ground plane through via holes, the other ends of the two quarter-wavelength metal resonators are bent, and the bent sections are located between the two quarter-wavelength metal resonators;
and the two quarter-wavelength metal resonators positioned at the outermost sides are correspondingly connected with the I metal signal excitation port and the II metal signal excitation port respectively.
Each quarter-wavelength metal resonator comprises a straight section, a vertical section and a reverse-folded section, wherein one end of the straight section is connected with a metal ground plane through a via hole, the other end of the straight section is vertically connected with one end of the vertical section, the other end of the vertical section is vertically connected with one end of the reverse-folded section, and the reverse-folded section is parallel to the straight section. The other ends of the return sections of the two quarter-wave metal resonators of each resonator pair are oppositely arranged.
The length of the straight section is L1, the length of the vertical section is L2, the length of the inflection section is L3, and the total length of the L1, the L2 and the L3 is equal to a quarter wavelength.
The invention has the beneficial effects that:
1. the structure is compact in appearance, the size is small, the width of the filter can be reduced by adjusting the bending degree of the quarter-wavelength resonator under the condition of ensuring that the working frequency is not changed, and the performance index of the filter is ensured to be basically unchanged;
2. compared with the traditional interdigital microstrip filter, the interdigital microstrip filter has larger coupling coefficient on the premise of the same resonator spacing, and can achieve wider bandwidth;
3. the finished product has adjustability, and the out-of-band rejection of the filter can be adjusted by adjusting the external cavity in practical use;
4. most of bending technologies in the prior art are used for reducing the size, and in the structure of the invention, the coupling between the resonators R1 and R2 is mainly coupled through the return section L3, compared with the traditional interdigital filter in a main body coupling mode, the coupling amount is greatly reduced, so that the relative bandwidth is small, the relative bandwidth of the traditional interdigital filter is generally 15% -40%, the relative bandwidth of the filter in the invention can be about 5% at the minimum, and the filter can be applied to the design of a narrow-band filter.
Drawings
Fig. 1 is an equivalent circuit diagram of a miniaturized thin film filter of the embodiment of the present application at 4 th order.
Fig. 2 is a plan view of the front substrate structure of the miniaturized thin film filter of the embodiment of the present application in order 4.
Fig. 3 is a plan view of a reverse substrate structure in a 4-order miniaturized thin film filter according to an embodiment of the present invention.
Fig. 4 is a dimension chart of the miniaturized thin film filter of the embodiment of the present application at 4 th order.
Fig. 5 is a schematic diagram of a miniaturized thin film filter according to an embodiment of the present application, applied in a cavity.
Fig. 6 is a simulation curve of the miniaturized thin film filter of the embodiment of the present application at an order of 4.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings, but the described embodiments of the present invention are a part of the embodiments of the present invention, not all of the embodiments of the present invention.
The embodiment of the application provides a miniaturized film filter utilizes film technology processing, and minimum dimension can reach 0.03mm, and the precision error can be guaranteed within 5um to there is better uniformity when processing in batches.
The filter of the embodiment comprises a dielectric substrate, wherein an I metal signal excitation port, an II metal signal excitation port and a resonator unit are formed on the front surface of the dielectric substrate through a thin film process, and a metal ground plane is arranged on the back surface of the dielectric substrate; the resonator unit is positioned between the I metal signal excitation port and the II metal signal excitation port and is arranged in a centrosymmetric manner by taking the center of the dielectric substrate as a center; the resonator unit comprises a plurality of resonator pairs arranged at intervals, each resonator pair comprises two quarter-wavelength metal resonators arranged at intervals, one ends of the two quarter-wavelength metal resonators face different sides and are connected with a metal ground plane through via holes, the other ends of the two quarter-wavelength metal resonators are bent, and the bent sections are located between the two quarter-wavelength metal resonators;
and the two quarter-wavelength metal resonators positioned at the outermost sides are correspondingly connected with the I metal signal excitation port and the II metal signal excitation port respectively.
Specifically, the I-th metal signal excitation port and the II-th metal signal excitation port are also symmetrical, and the whole filter is arranged in a centrosymmetric manner by taking the center of the dielectric substrate as a center.
Specifically, the number of resonator pairs is selected according to practical application, so as to form a filter using resonators of different orders, specifically, if the resonator unit has 1 resonator pair, that is, 2 quarter-wavelength resonators are included, the order of the filter is 2 orders; if the resonator unit has 2 resonator pairs, namely 4 quarter-wavelength resonators are included, the order of the filter is 4 orders; if the resonator unit has 3 resonator pairs, namely 6 quarter-wavelength resonators are included, the order of the filter is 6 orders; by analogy, there may be 8 steps, 10 steps, … … with the spacing between each pair maintained.
In this embodiment, a miniaturized thin film filter as shown in fig. 2 to fig. 3 is taken as an example, and a 4-order resonator is adopted, which includes a dielectric substrate A1, a first metal signal excitation port P1, a second metal signal excitation port P2 and a resonator unit are formed on the front surface of the dielectric substrate through a thin film process, and a metal ground plane G1 is disposed on the back surface of the dielectric substrate. The dielectric substrate A1 is an alumina ceramic substrate with a dielectric constant of 9.9, and the metal ground plane G1 is made of one or more of TIW, ni and Au.
The resonator unit is positioned between the I metal signal excitation port P1 and the II metal signal excitation port P2 and comprises two resonator pairs which are arranged in a centrosymmetric manner by taking the center of the dielectric substrate A1 as a center; specifically, one resonator pair includes an I-th quarter-wavelength metal resonator R1 and an II-th quarter-wavelength metal resonator R2 which are arranged at intervals, and the other resonator pair includes a III-th quarter-wavelength metal resonator R3 and an IV-th quarter-wavelength metal resonator R4 which are arranged at intervals. Each quarter-wavelength metal resonator is subjected to bending treatment and comprises a straight section, a vertical section and a folded section, wherein one end of the straight section is connected with a metal ground plane G1 through a through hole, the other end of the straight section is vertically connected with one end of the vertical section, the other end of the vertical section is vertically connected with one end of the folded section, and the folded section is parallel to the straight section. And the other ends of the two quarter-wavelength metal resonators of the same pair are oppositely arranged and have a distance.
The I quarter-wave metal resonator R1 and the IV quarter-wave metal resonator R4 are arranged in central symmetry with the center of the dielectric substrate A1; the II quarter-wave metal resonator R2 and the III quarter-wave metal resonator R3 are arranged in central symmetry with respect to the center of the dielectric substrate A1.
As shown in fig. 4, a first coupling gap g12 is provided between the I-th and II-th quarter-wavelength metal resonators R1 and R2, a second coupling gap g23 is provided between the II-th and III-th quarter-wavelength metal resonators R2 and R3, and a third coupling gap g34 is provided between the III-th and IV-th quarter-wavelength metal resonators R3 and R4.
The line segment width of each quarter-wavelength metal resonator is W1, the length of the straight section is L1, the length of the vertical section is L2, the length of the inflection section is L3, and the total length of L1, L2 and L3 is approximately equal to a quarter wavelength.
As shown in fig. 2, an I-th metalized ground via H1 is disposed at one end of a straight section of the I-th quarter-wave metal resonator R1, and the I-th metalized ground via H1 is connected to the metal ground plane G1; the I-th metal signal excitation port P1 is vertically connected with the outer side of the straight section of the I-th quarter-wavelength metal resonator R1, and the connection position is close to the I-th metalized grounding through hole H1. And one end of the straight section of the II quarter-wave metal resonator R2 is provided with an II metalized grounding through hole H2, and the II metalized grounding through hole H2 is connected to the metal ground plane G1.
The straight section of the I quarter-wave metal resonator R1 is provided with one end of an I metalized grounding through hole H1, and the straight section of the I quarter-wave metal resonator R1 and one end of the II quarter-wave metal resonator R2 which is provided with an II metalized grounding through hole H2 face opposite directions and face different sides of the dielectric substrate A1.
Similarly, an IV metalized ground via H4 is disposed at one end of the straight section of the IV quarter-wave metal resonator R4, and the IV metalized ground via H4 is connected to the metal ground plane G1; the II metal signal excitation port P2 is vertically connected with the outer side of the straight section of the IV quarter-wavelength metal resonator R4, and the connection position is close to the IV metalized ground through hole H4. One end of the straight section of the third quarter-wave metal resonator R3 is provided with a third metalized ground via H3, and the third metalized ground via H3 is connected to the metal ground plane G1.
The straight section of the IV quarter-wave metal resonator R4 is provided with one end of the IV metalized grounding through hole H4, and the straight section of the III quarter-wave metal resonator R3 is opposite to the end provided with the III metalized grounding through hole H3 and faces to different sides of the dielectric substrate A1.
More specifically, the straight section of the second quarter-wavelength metal resonator R2 and the straight section of the first quarter-wavelength metal resonator R1 are arranged in parallel at intervals; the distance between the reverse section and the straight section of the I quarter-wavelength metal resonator R1 is equal to the distance between the reverse section and the straight section of the II quarter-wavelength metal resonator R2; the distance between the reverse section of the I-th quarter-wavelength metal resonator R1 and the straight section of the II-th quarter-wavelength metal resonator R2 is equal to the distance between the reverse section of the II-th quarter-wavelength metal resonator R2 and the straight section of the I-th quarter-wavelength metal resonator R1, and is smaller than the distance between the reverse section and the straight section of the I-th quarter-wavelength metal resonator R1.
Fig. 1 is an equivalent circuit diagram of the present example using a 4-step resonator, in which an I-th quarter-wave metal resonator R1 is equivalent to an inductor L1 and a capacitor C1 of a parallel resonant circuit; the II quarter-wavelength metal resonator R2 is equivalent to an inductor L2 and a capacitor C2 of a parallel resonant circuit; the III quarter-wave metal resonator R3 is equivalent to an inductor L3 and a capacitor C3 of the parallel resonant circuit; the IV quarter-wave metal resonator R4 is equivalent to an inductor L4 and a capacitor C4 of a parallel resonant circuit.
The edge coupling between the I quarter-wave metal resonator R1 and the II quarter-wave metal resonator R2 is equivalent to a coupling capacitor C12; the edge coupling between the II quarter-wave metal resonator R2 and the III quarter-wave metal resonator R3 is equivalent to a coupling capacitor C23; the edge coupling between the III-quarter wavelength metal resonator R3 and the IV-quarter wavelength metal resonator R4 is equivalent to a coupling capacitance C34.
When in application, the filter of the present example is placed in a cavity, as shown in fig. 5; the cavity may be a metal cavity. Taking the total length of the filter as 6.5mm and the width as 5.0mm as an example, as shown in fig. 6, a simulation result curve is shown, a signal enters from an I-th metal signal excitation port P1, is filtered by a 4-order resonator and then is output from an II-th metal signal excitation port P2, and a non-artificial adjustable transmission zero point is generated at a high frequency position due to cross coupling between an intermediate II-th quarter-wavelength metal resonator R2 and an intermediate III-th quarter-wavelength metal resonator R3, so that out-of-band rejection can be improved.
This example is through carrying out bending process to the syntonizer, under the unchangeable circumstances of guaranteeing the syntonizer total length, under the unchangeable circumstances of the operating frequency of guaranteeing the wave filter promptly, the effectual width that reduces the wave filter to the performance of wave filter is not worsened. The novel structure can be adopted in the application scene with special requirements on the width of the filter. The filter width designed in this way is reduced by about 1/4 compared to a conventional interdigital microstrip filter.
The filter designed by the embodiment has the advantages of compact structure, small volume, good performance index, adjustability in the later period and higher consistency during batch production. In addition, the requirement of most microstrip filter indexes can be met by adjusting the order of the filter or the bending degree of the resonator, and the microstrip filter has high engineering practicability.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and it is apparent that those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (10)
1. A miniaturized thin film filter is characterized by comprising a dielectric substrate (A1), wherein an I metal signal excitation port (P1), an II metal signal excitation port (P2) and a resonator unit are formed on the front surface of the dielectric substrate through a thin film process, and a metal ground plane (G1) is arranged on the back surface of the dielectric substrate;
the resonator unit is positioned between the I metal signal excitation port (P1) and the II metal signal excitation port (P2) and is arranged in a centrosymmetric manner by taking the center of the dielectric substrate (A1);
the resonator unit comprises a plurality of resonator pairs arranged at intervals, each resonator pair comprises two quarter-wavelength metal resonators arranged at intervals, one ends of the two quarter-wavelength metal resonators face different sides and are connected with a metal ground plane (G1) through via holes, the other ends of the two quarter-wavelength metal resonators are bent, and the bent sections are located between the two quarter-wavelength metal resonators;
and the two outermost quarter-wavelength metal resonators are correspondingly connected with the I metal signal excitation port (P1) and the II metal signal excitation port (P2) respectively.
2. The miniaturized thin film filter of claim 1 wherein each quarter-wave metal resonator comprises a straight section, a vertical section, and a folded-back section, one end of the straight section is connected to the metal ground plane (G1) through a via hole, the other end of the straight section is vertically connected to one end of the vertical section, the other end of the vertical section is vertically connected to one end of the folded-back section, and the folded-back section is parallel to the straight section.
3. The miniaturized thin film filter of claim 2 wherein the two quarter-wave metal resonators of each resonator pair have their return sections at opposite ends.
4. The miniaturized thin film filter of claim 3, wherein the resonator unit comprises 2 spaced resonator pairs, wherein one of the resonator pairs comprises spaced I-th quarter-wave metal resonators (R1) and II-th quarter-wave metal resonators (R2), and the other resonator pair comprises spaced III-th quarter-wave metal resonators (R3) and IV-th quarter-wave metal resonators (R4);
the I quarter-wave metal resonator (R1) and the IV quarter-wave metal resonator (R4) are arranged in a centrosymmetric manner at the center of the dielectric substrate (A1);
the II quarter-wave metal resonator (R2) and the III quarter-wave metal resonator (R3) are arranged in central symmetry with the center of the dielectric substrate (A1).
5. The miniaturized thin film filter of claim 4, wherein the I metallic signal excitation port (P1) is vertically connected to the outside of the straight section of the I quarter-wavelength metallic resonator (R1), and the II metallic signal excitation port (P2) is vertically connected to the outside of the straight section of the IV quarter-wavelength metallic resonator (R4).
6. The miniaturized thin film filter of claim 4 wherein the I quarter wave metal resonator (R1) and the II quarter wave metal resonator (R2) have a first coupling gap (g 12) therebetween, the II quarter wave metal resonator (R2) and the III quarter wave metal resonator (R3) have a second coupling gap (g 23) therebetween, and the III quarter wave metal resonator (R3) and the IV quarter wave metal resonator (R4) have a third coupling gap (g 34) therebetween.
7. The miniaturized thin film filter of claim 4 wherein the straight sections of the II quarter wave metal resonators (R2) are spaced in parallel with the straight sections of the I quarter wave metal resonators (R1);
the distance between the reverse section and the straight section of the I quarter-wavelength metal resonator (R1) is equal to the distance between the reverse section and the straight section of the II quarter-wavelength metal resonator (R2);
the distance between the reverse section of the I quarter-wavelength metal resonator (R1) and the straight section of the II quarter-wavelength metal resonator (R2) is equal to the distance between the reverse section of the II quarter-wavelength metal resonator (R2) and the straight section of the I quarter-wavelength metal resonator (R1), and is smaller than the distance between the reverse section and the straight section of the I quarter-wavelength metal resonator (R1).
8. The miniaturized thin film filter of claim 2 wherein the straight section has a length L1, the vertical section has a length L2, the reverse section has a length L3, and the total length of L1, L2, and L3 is equal to a quarter wavelength.
9. The miniaturized thin film filter of claim 1, wherein the dielectric substrate (A1) is an alumina ceramic substrate.
10. The miniaturized thin film filter of claim 1, characterized in that the metal ground plane (G1) is made of one or more of TIW, ni, au.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211240895.7A CN115528402A (en) | 2022-10-11 | 2022-10-11 | Miniaturized thin film filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211240895.7A CN115528402A (en) | 2022-10-11 | 2022-10-11 | Miniaturized thin film filter |
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| CN115528402A true CN115528402A (en) | 2022-12-27 |
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| CN202211240895.7A Pending CN115528402A (en) | 2022-10-11 | 2022-10-11 | Miniaturized thin film filter |
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- 2022-10-11 CN CN202211240895.7A patent/CN115528402A/en active Pending
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