CN115863942A - Double-passband independently adjustable band-pass filter with constant bandwidth - Google Patents
Double-passband independently adjustable band-pass filter with constant bandwidth Download PDFInfo
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Abstract
The invention provides a dual-passband independently adjustable filter capable of keeping constant bandwidth, which is realized by adopting a structure that two different resonators share an input/output feeder line. The resonator comprises a microstrip line loaded variable capacitance diode, and the variable capacitance diode is connected with an external bias circuit. The filter mainly comprises an upper-layer microstrip line structure, a middle-layer dielectric substrate and a lower-layer grounding metal, and has the characteristics of simple structure, miniaturization, excellent characteristics and the like. The dual-passband tunable filter has the advantages that the defects of insufficient selectivity and bandwidth change of the dual-passband tunable filter can be overcome, the effects of independent adjustability of dual-passband and constant bandwidth keeping are realized, circuit integration and system packaging are easy to realize, and the dual-passband tunable filter can be widely applied to industrial production.
Description
Technical Field
The invention relates to the technical field of microwave communication, in particular to a dual-passband independently adjustable bandpass filter with constant bandwidth.
Background
With the rapid development of modern wireless communication technology, more and more mobile communication, satellite communication, radar tracking, remote sensing technology and the like need to use microwave and millimeter wave technology, so that the electromagnetic environment is increasingly complex, the spectrum resources are finally increasingly tense, the contradiction between the limited spectrum resources and the application requirements is increasingly prominent, and the traditional narrow-band communication system cannot adapt to the actual requirements of the application scenes due to small transmission capacity and low transmission rate, so that the adjustable technology is more and more emphasized by people.
In order to meet the urgent demands of multiple users for different communication modes and high transmission rates, the modern communication system needs to combine the multiband technology and the tunable technology, and therefore, a tunable multiband filter is developed. On the other hand, with the rapid development of wireless communication technology, it is generally necessary to communicate through a series of channels having the same bandwidth. Although a number of tunable dual-bandpass filters have been reported, these filters do not meet the requirements of constant bandwidth and independent adjustability, and are complex, adding to many design uncertainties.
The tunable filter structure designed in the past has the following disadvantages:
(1) Bandwidth changes during the frequency tuning range;
(2) The pass bands in the multi-pass-band adjustable filter are not independently adjustable;
(3) In the adjusting process, the performance of the filter is deteriorated and unstable.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a dual-passband independently tunable bandpass filter with constant bandwidth, which has compact structure, can realize high selectivity and is independently tunable, and can maintain constant bandwidth.
In order to achieve the purpose, the invention provides the following scheme:
a dual passband independently tunable filter for maintaining a constant bandwidth, comprising: the device comprises an upper microstrip structure, a middle dielectric substrate, a lower grounding metal, a first port, a second port, a first microstrip line connected with the first port, and a second microstrip line connected with the second port; the upper-layer microstrip structure is attached to the upper surface of the middle-layer dielectric substrate, and the lower-layer grounding metal is attached to the lower surface of the middle-layer dielectric substrate; the first port and the second port are respectively positioned at two sides of the middle layer medium substrate; the first microstrip line and the second microstrip line are mutually connected to form a common input/output feeder line;
the upper-layer microstrip structure comprises a first resonator and a second resonator; the first resonator and the second resonator are both left-right symmetric about a vertical axis; the first resonator is positioned at the outer side of the common input and output feeder line and is connected with the common input and output feeder line in a slot coupling mode; the first resonator comprises two symmetrical impedance line structures; the impedance line structure comprises a low impedance line, a first high impedance line, a second high impedance line, a third high impedance line, a fourth high impedance line and a first variable capacitance diode; one end of the low-impedance line is connected with a first bias voltage through a large resistor, the other end of the low-impedance line is connected with the first high-impedance line and the second high-impedance line, the other end of the second high-impedance line is connected with one end of the first variable capacitance diode, the other end of the first variable capacitance diode is connected with the third high-impedance line and the fourth high-impedance line, and the other end of the fourth high-impedance line is connected with the ground; the two symmetrical low-impedance lines are coupled with each other, and the two symmetrical first high-impedance lines are coupled with each other;
the second resonator is positioned on the inner side of the common input and output feeder line and is connected with the common input and output feeder line in a slot coupling mode; the second resonator comprises a third variable capacitance diode, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line and two symmetrical microstrip line structures; the microstrip line structure comprises a second variable capacitance diode, a third microstrip line and a fourth microstrip line connected with the third microstrip line; the other end of the fourth microstrip line is connected with one end of the second variable capacitance diode, the other end of the second variable capacitance diode is connected with the fifth microstrip line, two ends of the fifth microstrip line are grounded through large resistors respectively, and the center of the fifth microstrip line is connected with the sixth microstrip line and the seventh microstrip line through loading the third variable capacitance diode; and the sixth microstrip line is connected with a second bias voltage through a large resistor.
Preferably, the first resonator is used for generating two modes to form a first passband, and the first passband frequency is adjustable by changing the capacitance of the first varactor diode; the second resonator is used for generating odd and even modes to form a second passband, and the frequency of the second passband is adjustable by changing the capacitance of the second varactor; and the sixth microstrip line and the seventh microstrip line of the branch structure are loaded with a third variable capacitance diode to generate a self transmission zero point.
Preferably, the interlayer dielectric substrate is R04003C, the thickness is 0.508mm, the dielectric constant is 3.55 and the loss tangent is 0.0027.
Preferably, the radius of the ground end hole, through which the two ends of the fifth microstrip line are grounded via the large resistor, is 0.3mm.
Preferably, the first bias voltage and/or the second bias voltage is 0-15V.
Preferably, the first varactor is of a type of a silicon varactor SMV1233; the second varactor and/or the third varactor are of the type silicon varactor SMV1234.
Preferably, the resistance value of the large resistor is 100K ohms.
Preferably, the common input and output feeder comprises a source load coupling structure for additionally generating three adaptive transmission zeros.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the invention has the following advantages
The invention can generate four transmission zeros of an upper passband and a lower passband through the branch loading and source load coupling structure so as to realize high selectivity; and the independent adjustability of the upper and lower two pass bands is realized through the two different resonators by sharing the input and output feeder. And in particular embodiments by controlling the coupling coefficient K 12 And an external quality factor Q e To achieve bandwidth constancy during frequency tuning. The invention can make the device structure compact, and realize the independent adjustment of two pass bands while keeping constant absolute bandwidth.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is a schematic three-dimensional structure diagram of a tunable filter according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a tunable filter according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the physical dimensions of a tunable filter according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an S-parameter simulation curve for adjusting a pass band according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an S-parameter simulation curve of an adjustable two-pass band according to an embodiment of the present invention.
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 obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.
The terms "first," "second," "third," and "fourth," etc. in the description and claims of this application and in the accompanying drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, the inclusion of a list of steps, processes, methods, etc. is not limited to only those steps recited, but may alternatively include additional steps not recited, or may alternatively include additional steps inherent to such processes, methods, articles, or devices.
The invention aims to provide a double-passband independently adjustable bandpass filter with constant bandwidth, which has a compact structure, can realize high selectivity and is independently adjustable, and can keep constant bandwidth.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Fig. 1 is a schematic diagram of a three-dimensional structure of a tunable filter according to an embodiment of the present invention, and as shown in fig. 1, the embodiment provides a dual-passband independently tunable filter with a constant bandwidth, which includes an upper microstrip structure, a middle dielectric substrate, and a lower grounding metal.
As shown in fig. 2, the upper microstrip structure is left-right symmetric about a vertical axis. The microstrip structure of the filter is realized by two different resonators through sharing an input and output feeder line, wherein the two different resonators are a first resonator and a second resonator respectively; the first resonator and the second resonator are both bilaterally symmetrical about a vertical axis; the first port of the filter is positioned at one side of the medium substrate, and the second port is positioned at the other side of the medium substrate; two 50-ohm microstrip lines are respectively connected with the corresponding two ports, the two 50-ohm microstrip lines are the first microstrip line 12 (12_1), and the two microstrip lines are arranged on the same horizontal line; the first microstrip line 12 and the second microstrip line 11 (11_1) are connected to form a common input/output feeder.
The first resonator is positioned at the outer side of the shared feeder line and is connected with the feeder line in a slot coupling mode; the first resonator includes a symmetrical low impedance line 1 (1_1) and a first high impedance line 2 (2_1), the secondTwo high impedance lines 3, a third high impedance line 4, a fourth high impedance line 5 and a first variable capacitance diode Cv1, wherein one section of the low impedance line 1 is connected with a first bias voltage (bias voltage 1) through a large resistor, the other end of the low impedance line is connected with the first high impedance line 2 and the second high impedance line 3, and the other end of the second high impedance line 3 is connected with the first variable capacitance diode C v1 Are connected to one end of a first varactor diode C v1 The other end of the third high-impedance line 4 is connected with a fourth high-impedance line 5, and the other end of the fourth high-impedance line 5 is connected with the ground; the low impedance line 1 and the low impedance line 1_1 are coupled to each other, and the first high impedance line 2_1 are coupled to each other.
The second resonator is positioned at the inner side of the common feeder line and is connected with the feeder line in a slot coupling mode; the second resonator comprises a third microstrip line 6 and a fourth microstrip line 7 which are symmetrical, and the other end of the fourth microstrip line 7 is connected with a second variable capacitance diode C v2 Are connected to one end of a second varactor diode C v2 The other end of the second microstrip line 8 is connected with a fifth microstrip line 8, the two ends of the fifth microstrip line 8 are respectively grounded through a large resistor, and the center of the fifth microstrip line 8 is loaded with a third varactor diode C v3 Is connected with the seventh microstrip line 9 and the sixth microstrip line 10; the seventh microstrip line 9 is connected to the second bias voltage (bias 2) through a large resistance.
The first resonator is a pair of dual-mode resonators coupled with a feeder line to generate two resonance modes to form a first pass band, and the frequency of one pass band is adjustable by changing the external bias voltage 1. The second resonator is a branch-node loaded step impedance resonator, two odd-even resonance modes can be generated to form a second pass band, the frequency of the two pass bands can be adjusted by changing the external bias voltage 2, and the resonator can additionally generate a zero point.
In the embodiment, the coupling coefficients K of the upper and lower two pass bands are respectively analyzed 12 And an external quality factor Q e When the passband bandwidth is kept constant, the coupling coefficient K increases with the frequency during tuning 12 Reduced, external quality factor Q e And is increased.
As shown in FIG. 1, the interlayer dielectric sheet used in this example was R04003C, and had a thickness of 0.508mm, a dielectric constant of 3.55 and a loss tangent of 0.0027. The feeder structure adopts a source load coupling structure for feeding, and the structure can introduce extra transmission zero points, so that the selectivity of pass bands and the isolation between the pass bands are improved.
As shown in fig. 3, the detailed circuit dimensions of the resonator structure are: l is 1 ＝1.1mm，L 2 ＝2.4mm，L 3 ＝4.15mm，L 4 ＝5.65mm，L 5 ＝2.7mm，L 6 ＝12.1mm，L 7 ＝5.8mm，L 8 ＝4.3mm，L 9 ＝7.85mm，L 10 ＝6.95mm，L 11 ＝19.95mm，w 1 ＝2.3mm，w 2 ＝0.1mm，w 3 ＝0.3mm，w 4 ＝0.7mm，w 5 ＝0.3mm，w 6 ＝0.15mm，w 7 ＝0.4mm，w 8 ＝1.1mm，g 1 ＝0.3mm，g 2 ＝0.4mm，s 1 ＝0.3mm，s 2 ＝0.2mm，s 3 =0.8mm. The ground hole radius is 0.3mm.
In this embodiment, the high-frequency simulation software sonnet is used to perform optimization analysis on the whole structure, and the obtained S-parameter simulation curve is as shown in fig. 4 and 5. As can be seen from fig. 4 and 5, the center frequency of the first pass band of the filter can be changed within the range of 2.06-2.22GHz, and the absolute bandwidth can be kept unchanged at 60MHz during the change process; the central frequency of the second passband can be changed within the range of 3.1-3.6GHz, and the absolute bandwidth can be kept unchanged at 72MHz in the changing process; in the whole tuning range, the insertion loss is less than 1.4dB, and the return loss is better than 12dB; and the tuning processes of the upper and lower pass bands are not influenced mutually, so that the two pass bands can be independently adjusted. The two adaptive zeros on either side of the upper and lower pass bands allow the filter to be highly selective.
In conclusion, the double-passband independently adjustable filter with constant bandwidth combines the multimode resonator and the step impedance resonator, so that the double-passband independently adjustable filter which is compact in structure, high in selectivity, low in loss and capable of keeping the bandwidth constant in the adjusting process is realized, and the filter is suitable for modern wireless communication systems.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principle and the embodiment of the present invention are explained by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (8)
1. A dual passband independently tunable filter for maintaining a constant bandwidth comprising: the device comprises an upper microstrip structure, a middle dielectric substrate, a lower grounding metal, a first port, a second port, a first microstrip line connected with the first port, and a second microstrip line connected with the second port; the upper-layer microstrip structure is attached to the upper surface of the middle-layer dielectric substrate, and the lower-layer grounding metal is attached to the lower surface of the middle-layer dielectric substrate; the first port and the second port are respectively positioned on two sides of the middle layer dielectric substrate; the first microstrip line and the second microstrip line are mutually connected to form a common input/output feeder line;
the upper-layer microstrip structure comprises a first resonator and a second resonator; the first resonator and the second resonator are both left-right symmetric about a vertical axis; the first resonator is positioned at the outer side of the common input and output feeder line and is connected with the common input and output feeder line in a slot coupling mode; the first resonator comprises two symmetrical impedance line structures; the impedance line structure comprises a low impedance line, a first high impedance line, a second high impedance line, a third high impedance line, a fourth high impedance line and a first variable capacitance diode; one end of the low-impedance line is connected with a first bias voltage through a large resistor, the other end of the low-impedance line is connected with the first high-impedance line and the second high-impedance line, the other end of the second high-impedance line is connected with one end of the first variable capacitance diode, the other end of the first variable capacitance diode is connected with the third high-impedance line and the fourth high-impedance line, and the other end of the fourth high-impedance line is connected with the ground; the two symmetrical low-impedance lines are coupled with each other, and the two symmetrical first high-impedance lines are coupled with each other;
the second resonator is positioned on the inner side of the common input and output feeder line and is connected with the common input and output feeder line in a slot coupling mode; the second resonator comprises a third variable capacitance diode, a fifth microstrip line, a sixth microstrip line, a seventh microstrip line and two symmetrical microstrip line structures; the microstrip line structure comprises a second variable capacitance diode, a third microstrip line and a fourth microstrip line connected with the third microstrip line; the other end of the fourth microstrip line is connected with one end of the second varactor, the other end of the second varactor is connected with the fifth microstrip line, two ends of the fifth microstrip line are respectively grounded through a large resistor, and the center of the fifth microstrip line is connected with the sixth microstrip line and the seventh microstrip line through loading the third varactor; and the sixth microstrip line is connected with a second bias voltage through a large resistor.
2. A dual-passband independently tunable filter maintaining a constant bandwidth as claimed in claim 1 wherein said first resonator is configured to generate two modes to form a first passband and to achieve tuning of a frequency of the first passband by varying a capacitance of said first varactor; the second resonator is used for generating odd and even modes to form a second passband, and the frequency of the second passband is adjustable by changing the capacitance of the second varactor; and the sixth microstrip line and the seventh microstrip line of the branch structure are loaded with a third variable capacitance diode to generate a self transmission zero point.
3. A dual-passband independently tunable filter which maintains a constant bandwidth as claimed in claim 1 wherein the interlayer dielectric substrate is R04003C, has a thickness of 0.508mm, a dielectric constant of 3.55 and a loss tangent of 0.0027.
4. The dual-passband independently tunable filter capable of maintaining a constant bandwidth as claimed in claim 1, wherein the radius of the ground terminal hole of each of the two ends of the fifth microstrip line grounded through the large resistor is 0.3mm.
5. The dual-passband independently tunable filter for maintaining a constant bandwidth as claimed in claim 1, wherein the first bias voltage and/or the second bias voltage is 0-15V.
6. The double passband independently tunable filter to maintain a constant bandwidth as claimed in claim 1 wherein said first varactor is of the type silicon varactor SMV1233; the second varactor and/or the third varactor are/is of a silicon varactor SMV1234.
7. A dual passband independently tunable filter maintaining a constant bandwidth as claimed in claim 1 wherein said large resistor has a resistance of 100 kohms.
8. The dual-passband independently tunable filter for maintaining a constant bandwidth as claimed in claim 1, wherein the common input and output feed comprises a source load coupling structure for additionally generating three adaptive transmission zeros.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116259940A (en) * | 2023-04-14 | 2023-06-13 | 天津理工大学 | Dual-passband filter composed of semi-lumped elements |
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- 2022-12-13 CN CN202211602163.8A patent/CN115863942A/en active Pending
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