CN113540713A - Miniature filter - Google Patents
Miniature filter Download PDFInfo
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- CN113540713A CN113540713A CN202110779978.2A CN202110779978A CN113540713A CN 113540713 A CN113540713 A CN 113540713A CN 202110779978 A CN202110779978 A CN 202110779978A CN 113540713 A CN113540713 A CN 113540713A
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- micro
- transmission line
- coaxial transmission
- filter
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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
- H01P1/202—Coaxial filters
Abstract
The invention discloses a micro filter, which comprises a first micro coaxial transmission line, wherein the terminal of the first micro coaxial transmission line is short-circuited or open-circuited; the first micro-coaxial transmission line satisfies
Or
Wherein d1 is the length of the first micro-coaxial transmission line, n is a natural number, v is an electromagnetic wave phase velocity, and f is the center frequency of the micro-filter. The band-pass filter or band-stop filter with the frequency band of more than 6GHz formed by the micro-coaxial transmission line has smaller volume and low insertion loss, and the micro-coaxial transmission line is processed and manufactured by a semiconductor process, so the micro-coaxial transmission line is simple to manufacture, is easy for batch production, is compatible with semiconductor processes of other electronic devices, can be integrated with an electronic system, and is beneficial to integration and miniaturization of the system.
Description
Technical Field
The invention relates to the technical field of filters, in particular to a miniature filter.
Background
The filter is an essential element in a communication system, and filters of different frequency bands can adopt different manufacturing means, but are developed towards integration and miniaturization. In the frequency band below 6GHz, the micro-filter currently used for communication is an Acoustic Wave device based on semiconductor technology, including a Surface Acoustic Wave (SAW) device and a Bulk Acoustic Wave (BAW) device. At a higher frequency (for example, greater than 6GHz), the conventional filters mainly use metal waveguides, dielectric waveguides, and the like.
However, in the process of implementing the technical solution of the invention in the embodiments of the present application, the inventors of the present application find that the above-mentioned technology has at least the following technical problems: the limit frequency of an acoustic wave device based on a semiconductor process can only achieve 6GHz at present, and filtering of a frequency band above 6GHz cannot be achieved; in the filter with the frequency band above 6GHz, the device manufactured by adopting the technologies of metal waveguide, dielectric waveguide and the like has large volume, is difficult to integrate with an electronic system and is not beneficial to the miniaturization of the system.
Disclosure of Invention
The embodiment of the application solves the technical problems that the frequency band filter above 6GHz is large in size and difficult to integrate with an electronic system in the prior art by providing the micro filter, reduces the size of the frequency band filter above 6GHz, can be integrated with the electronic system, and is favorable for integration and miniaturization of the system.
The application provides the following technical scheme through an embodiment of the application:
a micro-filter comprises a first micro-coaxial transmission line, wherein the terminal of the first micro-coaxial transmission line is short-circuited or open-circuited;
the first micro-coaxial transmission line satisfies
Or
Wherein d1 is the length of the first micro-coaxial transmission line, n is a natural number, v is an electromagnetic wave phase velocity, and f is the center frequency of the micro-filter.
Preferably, n is 0.
Preferably, the value range of f is 6-500 GHz.
Preferably, the micro filter further comprises N stages of filter circuits, the first micro coaxial transmission line and the N stages of filter circuits are sequentially cascaded, and N is a positive integer;
each stage of the filter circuit comprises a second micro-coaxial transmission line and a third micro-coaxial transmission line, and the second micro-coaxial transmission line is connected with the third micro-coaxial transmission line in parallel;
the third micro-coaxial transmission line has the same length as the first micro-coaxial transmission line, and the third micro-coaxial transmission line and the terminal of the first micro-coaxial transmission line are simultaneously short-circuited or open-circuited.
Preferably, the value range of N is 1-3.
Preferably, the lengths of the first micro-coaxial transmission line, the second micro-coaxial transmission line and the third micro-coaxial transmission line are the same.
Preferably, the first micro-coaxial transmission line comprises an outer conductor, an inner conductor and a supporting medium;
the outer conductor surrounds the inner conductor, a distance is kept between the inner conductor and the outer conductor, the supporting medium is fixed in the outer conductor, and the inner conductor is arranged on the supporting medium.
Preferably, the inner conductor and the outer conductor are made of a metal material.
Preferably, the metal material is copper or gold.
Preferably, the supporting medium is made of SU-8 photoresist or benzocyclobutene.
The technical scheme provided in the embodiment of the application at least has the following technical effects or advantages:
1. the micro-coaxial transmission line with the length related to the central frequency of the filter can form a 0.5-level or multi-level band-pass filter/band-stop filter with the most basic frequency band above 6GHz, so that the filtering function of ultrahigh frequency and millimeter wave frequency bands is realized.
2. The length of the micro-coaxial transmission line can be minimized
The length of the micro-coaxial transmission line used for forming the band-pass filter or the band-stop filter is minimum, and the volume of the band-pass filter or the band-stop filter is minimum.
3. The steepness of the transition band of the filter can be increased by increasing the series of the micro-coaxial transmission line, and the filtering effect is improved.
4. The bandwidth of the filter can be changed by increasing the series number of the micro-coaxial transmission line or changing the length of the micro-coaxial transmission line, and the filter can be selected according to practical application and has strong adaptability.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a schematic axial cross-sectional view of a micro-coaxial transmission line according to the present invention;
FIG. 2 is an impedance characteristic diagram of a micro-coaxial transmission line with a length of 1.5mm in the range of 1-120 GHz according to the present invention;
FIG. 3 is a schematic diagram of a 0.5 stage bandpass filter of the present invention;
FIG. 4 is a graph of the transmission characteristics of a 0.5 stage bandpass filter of the present invention;
FIG. 5 is a schematic diagram of a 0.5 stage band reject filter of the present invention;
FIG. 6 is a schematic diagram of a multistage bandpass filter of the present invention;
FIG. 7 is a graph of the transmission characteristics of the multistage bandpass filter of the present invention;
FIG. 8 is a graph of the transmission characteristics of the multi-stage band-stop filter of the present invention;
fig. 9 is a transmission characteristic curve diagram of the multistage band-pass filter of the present invention when the length of the micro-coaxial transmission line is 4.5 mm.
Detailed Description
The embodiment of the application provides a micro filter, and solves the technical problems that in the prior art, a filter with a frequency band above 6GHz is large in size and difficult to integrate with an electronic system.
In order to solve the technical problems, the general idea of the embodiment of the application is as follows:
a micro filter comprises a first micro coaxial transmission line, wherein the terminal of the first micro coaxial transmission line is short-circuited or open-circuited; the first micro-coaxial transmission line satisfies
Or
Wherein d1 is the length of the first micro-coaxial transmission line, n is a natural number, v is the electromagnetic wave phase velocity, and f is the center frequency of the micro-filter.
In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.
First, it is stated that the term "and/or" appearing herein is merely one type of associative relationship that describes an associated object, meaning that three types of relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.
The first micro-coaxial transmission line, the second micro-coaxial transmission line, and the third micro-coaxial transmission line mentioned above and below in the present embodiment may be collectively referred to as a micro-coaxial transmission line. As shown in fig. 1, the micro-coaxial transmission line includes an outer conductor, an inner conductor and a supporting medium; the outer conductor surrounds the inner conductor, a distance is kept between the inner conductor and the outer conductor, the supporting medium is fixed in the outer conductor, and the inner conductor is arranged on the supporting medium. The outer conductor has a si substrate on one side.
The micro-coaxial transmission line is processed by a semiconductor process and comprises an inner conductor, a supporting medium and an outer conductor, wherein the inner conductor is suspended in the middle, the supporting medium is used for supporting the inner conductor, and the outer conductor surrounds the inner conductor. The inner conductor and the outer conductor are both made of conductive materials, including but not limited to metal materials or non-metal conductive materials, the metal materials include but not limited to gold, copper and the like, the gold is most suitable for the micro-coaxial transmission line, but the price is high, the cost is high, and the inner conductor and the outer conductor are preferably made of copper, so that the cost performance is highest. The supporting medium is used for supporting the inner conductor suspended in the middle and is made of dielectric materials commonly used in semiconductor technology, including but not limited to SU-8 photoresist, benzocyclobutene (BCB) and the like.
The experiment of the embodiment shows that when the terminal of the micro-coaxial transmission line is short-circuited, the input impedance of the micro-coaxial transmission line is low
Where Zin is an input impedance, Z0 is a characteristic impedance of the micro-coaxial transmission line, β is a phase, d is a length of the micro-coaxial transmission line, M is a natural number, λ is a wavelength
v is the electromagnetic wave phase velocity, and in the hollow micro-coaxial transmission line, v is approximate to the electromagnetic wave velocity propagating in vacuum, and f is the central frequency. In the experiment, the impedance characteristics of the micro-coaxial transmission line with d being 1.5mm in the range of 1-120 GHz are simulated, and the result is shown in FIG. 2. As can be seen from fig. 2, when f is 50GHz, the input impedance of the micro-coaxial transmission line is extremely large, and at this time, the input impedance is extremely large
By
As can be seen, M is 0,
when f is 0 or 100GHz, the input impedance of the micro-coaxial transmission line is extremely small, and when f is 0, both M and d are 0; when f is 100GHz, at this time
By
As can be seen, M is 1. The simulation result of fig. 2 corresponds to equation (r).
From the above experiments, it was found that the terminals were short-circuited,
(i.e. the
) The input impedance of the micro-coaxial transmission line is extremely large, and the terminal is short-circuited,
The micro-coaxial transmission line is connected in parallel to the transmission circuit, that is, a 0.5-stage band-pass filter, which is denoted as a first band-pass filter, is shown in fig. 3 (the COAX in fig. 3 is the micro-coaxial transmission line), and the electrical transmission characteristic curve of the micro-coaxial transmission line is shown in fig. 4, the center frequency is 50GHz, and when M is 0, d has the minimum value of
Namely, it is
Short circuit at the terminal,
(i.e. the
) (M is a natural number greater than 0 in this case) has a very low input impedance, and short-circuits the terminals,
The micro-coaxial transmission line (M is a natural number greater than 0) is connected in parallel to the transmission circuit, so that a 0.5-stage band elimination filter can be formed and is marked as a first band elimination filter, and d has the minimum value of 1
Namely, it is
The experiment of the embodiment also shows that when the terminal of the micro-coaxial transmission line is open, the input impedance is open
By the same token, the terminal is open-circuited,
(i.e. the
) The input impedance of the micro-coaxial transmission line is extremely small, and the terminal is open-circuited,
The micro-coaxial transmission line is connected in parallel to the transmission circuit, namely a 0.5-stage band-stop filter can be formed and marked as a second band-stop filter, as shown in fig. 5, when M is 0, d has the minimum value of
Namely, it is
Open circuit at the terminal,
(i.e. the
) (M is a natural number greater than 0 at this time) the input impedance of the micro-coaxial transmission line is extremely large, and the terminal is opened,
The micro-coaxial transmission line (M is a natural number greater than 0 at this moment) is connected in parallel to the transmission circuit, namely a 0.5-stage band-pass filter can be formed and recorded as a second band-pass filter, and d has the minimum value of 0.5 when M takes 1
Namely, it is
As can be seen from the above, the embodiment may form a most basic bandpass filter or band-stop filter of 0.5 stage by the micro-coaxial transmission line, and the micro-coaxial transmission line in fig. 3 and fig. 5 is referred to as the first micro-coaxial transmission line, then the most basic bandpass filter or band-stop filter of 0.5 stage may be summarized as: the micro-coaxial transmission line comprises a first micro-coaxial transmission line, wherein the terminal of the first micro-coaxial transmission line is short-circuited or open-circuited; the first micro-coaxial transmission line satisfies
Or
Wherein d1 is the length of the first micro-coaxial transmission line, n is a natural number, v is the electromagnetic wave phase velocity, and f is the center frequency of the micro-filter. Where n is equivalent to M above and d1 is equivalent to d. When the terminal of the first micro-coaxial transmission line is short-circuited and the first micro-coaxial transmission line satisfies
When the band-stop filter is used, the band-stop filter corresponds to the first band-stop filter in the above; when the terminal of the first micro-coaxial transmission line is short-circuited and the first micro-coaxial transmission line satisfies
When corresponding to the first band-pass filter above; when the terminal of the first micro-coaxial transmission line is open and the first micro-coaxial transmission line meets the requirement
Then, corresponds to the second band-pass filter above; when the terminal of the first micro-coaxial transmission line is open and the first micro-coaxial transmission line meets the requirement
Corresponding to the second band reject filter above. Thus, after the target center frequency is determined, the length of the micro-coaxial transmission line can be calculated to meet the requirement, and the length can be multiple, but has the minimum length.
Further, in this embodiment, it is preferable that the value of n is 0, that is, the first band-pass filter or the second band-stop filter can be obtained, and when n is 0, d1 of the first band-pass filter or the second band-stop filter has the minimum value of 0
The length of the micro-coaxial transmission line used for forming the band-pass filter or the band-stop filter is minimum, and the volume of the band-pass filter or the band-stop filter is minimum.
After experimental verification, the 0.5-stage filter composed of the micro-coaxial transmission line can realize band-pass/band-stop filtering with the center frequency in the range of 6GHz-500GHz, namely, the value range of f is 6-500 GHz.
In addition, in addition to the most basic band-pass filter or band-stop filter with 0.5 order, the present embodiment has found through experiments that increasing the number of stages of the micro-coaxial transmission line can increase the steepness of the transition band of the filter. For the band pass filter, the form of adding micro coaxial transmission line is shown in fig. 6, fig. 6 shows band pass filters of 1.5 stages and 3.5 stages, and this embodiment refers to each stage added as a filter circuit. For a band-pass filter or a band-stop filter, each added stage of filter circuit is formed by connecting a normal micro-coaxial transmission line and a micro-coaxial transmission line with a short-circuited terminal in parallel, or formed by connecting a normal micro-coaxial transmission line and a micro-coaxial transmission line with an open-circuited terminal in parallel. In this embodiment, the normal micro-coaxial transmission line in each added stage of the filter circuit is referred to as a second micro-coaxial transmission line, and the micro-coaxial transmission line with a short-circuited terminal or the micro-coaxial transmission line with an open-circuited terminal in each added stage of the filter circuit is referred to as a third micro-coaxial transmission line. In the 1.5-stage bandpass filter shown in the upper part of fig. 6, the left micro-coaxial transmission line is the first micro-coaxial transmission line, the middle micro-coaxial transmission line is the second micro-coaxial transmission line, the right micro-coaxial transmission line is the third micro-coaxial transmission line, and so on. However, after the filter circuit is added, the requirement that the length of the third micro-coaxial transmission line is the same as that of the first micro-coaxial transmission line and the terminal of the third micro-coaxial transmission line and the terminal of the first micro-coaxial transmission line are simultaneously short-circuited or open-circuited must be met, so that the band-pass filter or the band-stop filter can be formed. The lengths of the first micro-coaxial transmission line, the second micro-coaxial transmission line and the third micro-coaxial transmission line are all kept the same and are 1.5mm, and 0.5, 1.5, 2.5 and 3.5-level band-pass filters with the center frequency of 50GHz are simulated, and the result is shown in FIG. 7; the results of simulating 0.5, 1.5, 2.5 and 3.5 stages of band-stop filters with the center frequency of 50GHz are shown in FIG. 8. Fig. 7 and 8 illustrate that increasing the number of stages of the micro-coaxial transmission line increases the steepness of the transition band.
In this way, in order to increase the steepness of the transition band of the filter, the preferable micro filter of this embodiment further includes N stages of filter circuits, the first micro coaxial transmission line and the N stages of filter circuits are sequentially cascaded, and N is a positive integer; each stage of filter circuit comprises a second micro-coaxial transmission line and a third micro-coaxial transmission line, and the second micro-coaxial transmission line is connected with the third micro-coaxial transmission line in parallel; the third micro-coaxial transmission line has the same length as the first micro-coaxial transmission line, and the third micro-coaxial transmission line and the terminal of the first micro-coaxial transmission line are simultaneously short-circuited or open-circuited. When the third micro-coaxial transmission line and the terminal of the first micro-coaxial transmission line are short-circuited at the same time, the filter is a multistage band-pass filter; and when the third micro-coaxial transmission line and the terminal of the first micro-coaxial transmission line are simultaneously open-circuited, the filter is a multistage band-stop filter. Thus, the steepness of the transition band of the filter can be increased by increasing the number of stages of the micro-coaxial transmission line. In fig. 7 and 8 of this embodiment, when N is 1, it corresponds to a 1.5-level filter, when N is 2, it corresponds to a 2.5-level filter, and when N is 3, it corresponds to a 3.5-level filter, and the value range of N includes, but is not limited to, 1 to 3.
After experimental verification, the multistage filter composed of the micro-coaxial transmission line can also realize band-pass/band-stop filtering with the center frequency in the range of 6GHz-500GHz, namely, the value range of f is 6-500 GHz.
For a multistage filter, the length of the second micro-coaxial transmission line can be the same as or different from the lengths of the first and third micro-coaxial transmission lines, but experiments show that the symmetry of the transmission characteristic curve of the filter is best when the length of the second micro-coaxial transmission line is the same as the lengths of the first and third micro-coaxial transmission lines, and the symmetry of the transmission characteristic curve of the filter is poor when the length of the second micro-coaxial transmission line is different from the lengths of the first and third micro-coaxial transmission lines. Therefore, in this embodiment, it is preferable that the lengths of the first micro-coaxial transmission line, the second micro-coaxial transmission line, and the third micro-coaxial transmission line are all the same, and the symmetry of the transmission characteristic curve of the filter is the best, so that the filtering effect of the filter is better in a frequency band near the center frequency.
In addition, the experiment of the embodiment shows that for the filter with determined center frequency, the bandwidth of the filter can be changed by changing the stage number of the filter or the length of the micro-coaxial transmission line. Taking the band-pass filter as an example, if the center frequency is 50GHz, as shown in fig. 7, the higher the level of the band-pass filter is, the narrower the bandwidth is, and the steeper the transition band is; as shown in fig. 7, the 3.5-stage, 1.5 mm-d 1 bandpass filter has a bandwidth of 41.2 GHz; a 4.5mm d1 bandpass filter is used, as shown in fig. 9, and the 3.5 stage, 4.5mm d1 bandpass filter has a bandwidth of 13.6 GHz. The number of stages of the filter or the length of the micro-coaxial transmission line can be changed according to the actual requirements of the filter to realize different bandwidths.
In summary, in the present embodiment, the micro-coaxial transmission line having a length associated with the center frequency of the filter may form the most basic 0.5-level or multi-level band pass filter/band stop filter in the frequency band above 6GHz, so as to implement the filtering function in the ultra-high frequency and millimeter wave frequency bands, and compared with the devices manufactured by using the metal waveguide, the dielectric waveguide, and other technologies, the band pass filter or band stop filter in the frequency band above 6GHz formed by the micro-coaxial transmission line has smaller volume and low insertion loss.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A micro-filter is characterized by comprising a first micro-coaxial transmission line, wherein the terminal of the first micro-coaxial transmission line is short-circuited or open-circuited;
the first micro-coaxial transmission line satisfies
Or
Wherein d1 is the length of the first micro-coaxial transmission line, n is a natural number, v is an electromagnetic wave phase velocity, and f is the center frequency of the micro-filter.
2. The microfilter of claim 1, wherein n has a value of 0.
3. The micro-filter of claim 1, wherein f has a value in the range of 6 to 500 GHz.
4. The microfilter of claim 1 or 2, further comprising N stages of filter circuits, said first micro-coaxial transmission line, N stages of said filter circuits being cascaded in sequence, N being a positive integer;
each stage of the filter circuit comprises a second micro-coaxial transmission line and a third micro-coaxial transmission line, and the second micro-coaxial transmission line is connected with the third micro-coaxial transmission line in parallel;
the third micro-coaxial transmission line has the same length as the first micro-coaxial transmission line, and the third micro-coaxial transmission line and the terminal of the first micro-coaxial transmission line are simultaneously short-circuited or open-circuited.
5. The microfilter of claim 4, wherein N is between 1 and 3.
6. The micro-filter of claim 4, wherein the first micro-coaxial transmission line, the second micro-coaxial transmission line, and the third micro-coaxial transmission line are all the same length.
7. The micro-filter of claim 1, wherein the first micro-coaxial transmission line comprises an outer conductor, an inner conductor, and a supporting medium;
the outer conductor surrounds the inner conductor, a distance is kept between the inner conductor and the outer conductor, the supporting medium is fixed in the outer conductor, and the inner conductor is arranged on the supporting medium.
8. The micro-filter of claim 7, wherein the inner conductor and the outer conductor are made of a metallic material.
9. The microfilter of claim 8, wherein said metallic material is copper or gold.
10. The micro-filter of claim 7, wherein the support medium is made of SU-8 photoresist or benzocyclobutene.
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| CN202110779978.2A CN113540713A (en) | 2021-07-09 | 2021-07-09 | Miniature filter |
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| CN202110779978.2A CN113540713A (en) | 2021-07-09 | 2021-07-09 | Miniature filter |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1041663A1 (en) * | 1999-03-27 | 2000-10-04 | Space Systems / Loral, Inc. | General response dual-mode, dielectric resonator loaded cavity filter |
| CN201285677Y (en) * | 2008-11-04 | 2009-08-05 | 中国传媒大学 | Coaxial transmission wire having matching dielectric ring |
| JP2010258857A (en) * | 2009-04-27 | 2010-11-11 | Nippon Antenna Co Ltd | Filter device |
| CN102176525A (en) * | 2011-01-30 | 2011-09-07 | 广东通宇通讯股份有限公司 | Filtering device with compact structure |
| CN104134847A (en) * | 2014-07-01 | 2014-11-05 | 泰兴市东盛电子器材厂 | Air coaxial center-fed antenna |
-
2021
- 2021-07-09 CN CN202110779978.2A patent/CN113540713A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1041663A1 (en) * | 1999-03-27 | 2000-10-04 | Space Systems / Loral, Inc. | General response dual-mode, dielectric resonator loaded cavity filter |
| CN201285677Y (en) * | 2008-11-04 | 2009-08-05 | 中国传媒大学 | Coaxial transmission wire having matching dielectric ring |
| JP2010258857A (en) * | 2009-04-27 | 2010-11-11 | Nippon Antenna Co Ltd | Filter device |
| CN102176525A (en) * | 2011-01-30 | 2011-09-07 | 广东通宇通讯股份有限公司 | Filtering device with compact structure |
| CN104134847A (en) * | 2014-07-01 | 2014-11-05 | 泰兴市东盛电子器材厂 | Air coaxial center-fed antenna |
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Application publication date: 20211022 |